Merge pull request #648 from WebAssembly/relooper-opts

Relooper improvements

7 files changed, 2805 insertions, 733 deletions

diff --git a/test/example/c-api-kitchen-sink.c b/test/example/c-api-kitchen-sink.c
index 568492659..496ac4efd 100644
--- a/test/example/c-api-kitchen-sink.c
+++ b/test/example/c-api-kitchen-sink.c
@@ -270,37 +270,48 @@ void test_core() {
   BinaryenModuleDispose(module);
 }
 
+BinaryenExpressionRef makeCallCheck(BinaryenModuleRef module, int x) {
+  BinaryenExpressionRef callOperands[] = { makeInt32(module, x) };
+  return BinaryenCallImport(module, "check", callOperands, 1, BinaryenNone());
+}
+
 void test_relooper() {
   BinaryenModuleRef module = BinaryenModuleCreate();
   BinaryenFunctionTypeRef v = BinaryenAddFunctionType(module, "v", BinaryenNone(), NULL, 0);
   BinaryenType localTypes[] = { BinaryenInt32() };
 
+  {
+    BinaryenType iparams[1] = { BinaryenInt32() };
+    BinaryenFunctionTypeRef vi = BinaryenAddFunctionType(module, "vi", BinaryenNone(), iparams, 1);
+    BinaryenAddImport(module, "check", "module", "check", vi);
+  }
+
   { // trivial: just one block
     RelooperRef relooper = RelooperCreate();
-    RelooperBlockRef block = RelooperAddBlock(relooper, makeSomething(module));
+    RelooperBlockRef block = RelooperAddBlock(relooper, makeCallCheck(module, 1337));
     BinaryenExpressionRef body = RelooperRenderAndDispose(relooper, block, 0, module);
     BinaryenFunctionRef sinker = BinaryenAddFunction(module, "just-one-block", v, localTypes, 1, body);
   }
   { // two blocks
     RelooperRef relooper = RelooperCreate();
-    RelooperBlockRef block0 = RelooperAddBlock(relooper, makeInt32(module, 0));
-    RelooperBlockRef block1 = RelooperAddBlock(relooper, makeInt32(module, 1));
+    RelooperBlockRef block0 = RelooperAddBlock(relooper, makeCallCheck(module, 0));
+    RelooperBlockRef block1 = RelooperAddBlock(relooper, makeCallCheck(module,  1));
     RelooperAddBranch(block0, block1, NULL, NULL); // no condition, no code on branch
     BinaryenExpressionRef body = RelooperRenderAndDispose(relooper, block0, 0, module);
     BinaryenFunctionRef sinker = BinaryenAddFunction(module, "two-blocks", v, localTypes, 1, body);
   }
   { // two blocks with code between them
     RelooperRef relooper = RelooperCreate();
-    RelooperBlockRef block0 = RelooperAddBlock(relooper, makeInt32(module, 0));
-    RelooperBlockRef block1 = RelooperAddBlock(relooper, makeInt32(module, 1));
+    RelooperBlockRef block0 = RelooperAddBlock(relooper, makeCallCheck(module,  0));
+    RelooperBlockRef block1 = RelooperAddBlock(relooper, makeCallCheck(module,  1));
     RelooperAddBranch(block0, block1, NULL, makeInt32(module, 77)); // code on branch
     BinaryenExpressionRef body = RelooperRenderAndDispose(relooper, block0, 0, module);
     BinaryenFunctionRef sinker = BinaryenAddFunction(module, "two-blocks-plus-code", v, localTypes, 1, body);
   }
   { // two blocks in a loop
     RelooperRef relooper = RelooperCreate();
-    RelooperBlockRef block0 = RelooperAddBlock(relooper, makeInt32(module, 0));
-    RelooperBlockRef block1 = RelooperAddBlock(relooper, makeInt32(module, 1));
+    RelooperBlockRef block0 = RelooperAddBlock(relooper, makeCallCheck(module,  0));
+    RelooperBlockRef block1 = RelooperAddBlock(relooper, makeCallCheck(module,  1));
     RelooperAddBranch(block0, block1, NULL, NULL);
     RelooperAddBranch(block1, block0, NULL, NULL);
     BinaryenExpressionRef body = RelooperRenderAndDispose(relooper, block0, 0, module);
@@ -308,8 +319,8 @@ void test_relooper() {
   }
   { // two blocks in a loop with codes
     RelooperRef relooper = RelooperCreate();
-    RelooperBlockRef block0 = RelooperAddBlock(relooper, makeInt32(module, 0));
-    RelooperBlockRef block1 = RelooperAddBlock(relooper, makeInt32(module, 1));
+    RelooperBlockRef block0 = RelooperAddBlock(relooper, makeCallCheck(module,  0));
+    RelooperBlockRef block1 = RelooperAddBlock(relooper, makeCallCheck(module,  1));
     RelooperAddBranch(block0, block1, NULL, makeInt32(module, 33));
     RelooperAddBranch(block1, block0, NULL, makeInt32(module, -66));
     BinaryenExpressionRef body = RelooperRenderAndDispose(relooper, block0, 0, module);
@@ -317,9 +328,9 @@ void test_relooper() {
   }
   { // split
     RelooperRef relooper = RelooperCreate();
-    RelooperBlockRef block0 = RelooperAddBlock(relooper, makeInt32(module, 0));
-    RelooperBlockRef block1 = RelooperAddBlock(relooper, makeInt32(module, 1));
-    RelooperBlockRef block2 = RelooperAddBlock(relooper, makeInt32(module, 2));
+    RelooperBlockRef block0 = RelooperAddBlock(relooper, makeCallCheck(module,  0));
+    RelooperBlockRef block1 = RelooperAddBlock(relooper, makeCallCheck(module,  1));
+    RelooperBlockRef block2 = RelooperAddBlock(relooper, makeCallCheck(module,  2));
     RelooperAddBranch(block0, block1, makeInt32(module, 55), NULL);
     RelooperAddBranch(block0, block2, NULL, NULL);
     BinaryenExpressionRef body = RelooperRenderAndDispose(relooper, block0, 0, module);
@@ -327,9 +338,9 @@ void test_relooper() {
   }
   { // split + code
     RelooperRef relooper = RelooperCreate();
-    RelooperBlockRef block0 = RelooperAddBlock(relooper, makeInt32(module, 0));
-    RelooperBlockRef block1 = RelooperAddBlock(relooper, makeInt32(module, 1));
-    RelooperBlockRef block2 = RelooperAddBlock(relooper, makeInt32(module, 2));
+    RelooperBlockRef block0 = RelooperAddBlock(relooper, makeCallCheck(module,  0));
+    RelooperBlockRef block1 = RelooperAddBlock(relooper, makeCallCheck(module,  1));
+    RelooperBlockRef block2 = RelooperAddBlock(relooper, makeCallCheck(module,  2));
     BinaryenExpressionRef temp = makeInt32(module, 10);
     RelooperAddBranch(block0, block1, makeInt32(module, 55), temp);
     RelooperAddBranch(block0, block2, NULL, makeInt32(module, 20));
@@ -338,9 +349,9 @@ void test_relooper() {
   }
   { // if
     RelooperRef relooper = RelooperCreate();
-    RelooperBlockRef block0 = RelooperAddBlock(relooper, makeInt32(module, 0));
-    RelooperBlockRef block1 = RelooperAddBlock(relooper, makeInt32(module, 1));
-    RelooperBlockRef block2 = RelooperAddBlock(relooper, makeInt32(module, 2));
+    RelooperBlockRef block0 = RelooperAddBlock(relooper, makeCallCheck(module,  0));
+    RelooperBlockRef block1 = RelooperAddBlock(relooper, makeCallCheck(module,  1));
+    RelooperBlockRef block2 = RelooperAddBlock(relooper, makeCallCheck(module,  2));
     RelooperAddBranch(block0, block1, makeInt32(module, 55), NULL);
     RelooperAddBranch(block0, block2, NULL, NULL);
     RelooperAddBranch(block1, block2, NULL, NULL);
@@ -349,9 +360,9 @@ void test_relooper() {
   }
   { // if + code
     RelooperRef relooper = RelooperCreate();
-    RelooperBlockRef block0 = RelooperAddBlock(relooper, makeInt32(module, 0));
-    RelooperBlockRef block1 = RelooperAddBlock(relooper, makeInt32(module, 1));
-    RelooperBlockRef block2 = RelooperAddBlock(relooper, makeInt32(module, 2));
+    RelooperBlockRef block0 = RelooperAddBlock(relooper, makeCallCheck(module,  0));
+    RelooperBlockRef block1 = RelooperAddBlock(relooper, makeCallCheck(module,  1));
+    RelooperBlockRef block2 = RelooperAddBlock(relooper, makeCallCheck(module,  2));
     BinaryenExpressionRef temp = makeInt32(module, -1);
     RelooperAddBranch(block0, block1, makeInt32(module, 55), temp);
     RelooperAddBranch(block0, block2, NULL, makeInt32(module, -2));
@@ -361,10 +372,10 @@ void test_relooper() {
   }
   { // if-else
     RelooperRef relooper = RelooperCreate();
-    RelooperBlockRef block0 = RelooperAddBlock(relooper, makeInt32(module, 0));
-    RelooperBlockRef block1 = RelooperAddBlock(relooper, makeInt32(module, 1));
-    RelooperBlockRef block2 = RelooperAddBlock(relooper, makeInt32(module, 2));
-    RelooperBlockRef block3 = RelooperAddBlock(relooper, makeInt32(module, 3));
+    RelooperBlockRef block0 = RelooperAddBlock(relooper, makeCallCheck(module,  0));
+    RelooperBlockRef block1 = RelooperAddBlock(relooper, makeCallCheck(module,  1));
+    RelooperBlockRef block2 = RelooperAddBlock(relooper, makeCallCheck(module,  2));
+    RelooperBlockRef block3 = RelooperAddBlock(relooper, makeCallCheck(module,  3));
     RelooperAddBranch(block0, block1, makeInt32(module, 55), NULL);
     RelooperAddBranch(block0, block2, NULL, NULL);
     RelooperAddBranch(block1, block3, NULL, NULL);
@@ -374,9 +385,9 @@ void test_relooper() {
   }
   { // loop+tail
     RelooperRef relooper = RelooperCreate();
-    RelooperBlockRef block0 = RelooperAddBlock(relooper, makeInt32(module, 0));
-    RelooperBlockRef block1 = RelooperAddBlock(relooper, makeInt32(module, 1));
-    RelooperBlockRef block2 = RelooperAddBlock(relooper, makeInt32(module, 2));
+    RelooperBlockRef block0 = RelooperAddBlock(relooper, makeCallCheck(module,  0));
+    RelooperBlockRef block1 = RelooperAddBlock(relooper, makeCallCheck(module,  1));
+    RelooperBlockRef block2 = RelooperAddBlock(relooper, makeCallCheck(module,  2));
     RelooperAddBranch(block0, block1, NULL, NULL);
     RelooperAddBranch(block1, block0, makeInt32(module, 10), NULL);
     RelooperAddBranch(block1, block2, NULL, NULL);
@@ -385,13 +396,13 @@ void test_relooper() {
   }
   { // nontrivial loop + phi to head
     RelooperRef relooper = RelooperCreate();
-    RelooperBlockRef block0 = RelooperAddBlock(relooper, makeInt32(module, 0));
-    RelooperBlockRef block1 = RelooperAddBlock(relooper, makeInt32(module, 1));
-    RelooperBlockRef block2 = RelooperAddBlock(relooper, makeInt32(module, 2));
-    RelooperBlockRef block3 = RelooperAddBlock(relooper, makeInt32(module, 3));
-    RelooperBlockRef block4 = RelooperAddBlock(relooper, makeInt32(module, 4));
-    RelooperBlockRef block5 = RelooperAddBlock(relooper, makeInt32(module, 5));
-    RelooperBlockRef block6 = RelooperAddBlock(relooper, makeInt32(module, 6));
+    RelooperBlockRef block0 = RelooperAddBlock(relooper, makeCallCheck(module,  0));
+    RelooperBlockRef block1 = RelooperAddBlock(relooper, makeCallCheck(module,  1));
+    RelooperBlockRef block2 = RelooperAddBlock(relooper, makeCallCheck(module,  2));
+    RelooperBlockRef block3 = RelooperAddBlock(relooper, makeCallCheck(module,  3));
+    RelooperBlockRef block4 = RelooperAddBlock(relooper, makeCallCheck(module,  4));
+    RelooperBlockRef block5 = RelooperAddBlock(relooper, makeCallCheck(module,  5));
+    RelooperBlockRef block6 = RelooperAddBlock(relooper, makeCallCheck(module,  6));
     RelooperAddBranch(block0, block1, NULL, makeInt32(module, 10));
     RelooperAddBranch(block1, block2, makeInt32(module, -2), NULL);
     RelooperAddBranch(block1, block6, NULL, makeInt32(module, 20));
@@ -407,10 +418,10 @@ void test_relooper() {
   { // switch
     RelooperRef relooper = RelooperCreate();
     BinaryenExpressionRef temp = makeInt32(module, -99);
-    RelooperBlockRef block0 = RelooperAddBlockWithSwitch(relooper, makeInt32(module, 0), temp);
-    RelooperBlockRef block1 = RelooperAddBlock(relooper, makeInt32(module, 1));
-    RelooperBlockRef block2 = RelooperAddBlock(relooper, makeInt32(module, 2));
-    RelooperBlockRef block3 = RelooperAddBlock(relooper, makeInt32(module, 3));
+    RelooperBlockRef block0 = RelooperAddBlockWithSwitch(relooper, makeCallCheck(module,  0), temp);
+    RelooperBlockRef block1 = RelooperAddBlock(relooper, makeCallCheck(module,  1));
+    RelooperBlockRef block2 = RelooperAddBlock(relooper, makeCallCheck(module,  2));
+    RelooperBlockRef block3 = RelooperAddBlock(relooper, makeCallCheck(module,  3));
     BinaryenIndex to_block1[] = { 2, 5 };
     RelooperAddBranchForSwitch(block0, block1, to_block1, 2, NULL);
     BinaryenIndex to_block2[] = { 4 };
@@ -421,9 +432,9 @@ void test_relooper() {
   }
   { // duff's device
     RelooperRef relooper = RelooperCreate();
-    RelooperBlockRef block0 = RelooperAddBlock(relooper, makeInt32(module, 0));
-    RelooperBlockRef block1 = RelooperAddBlock(relooper, makeInt32(module, 1));
-    RelooperBlockRef block2 = RelooperAddBlock(relooper, makeInt32(module, 2));
+    RelooperBlockRef block0 = RelooperAddBlock(relooper, makeCallCheck(module,  0));
+    RelooperBlockRef block1 = RelooperAddBlock(relooper, makeCallCheck(module,  1));
+    RelooperBlockRef block2 = RelooperAddBlock(relooper, makeCallCheck(module,  2));
     RelooperAddBranch(block0, block1, makeInt32(module, 10), NULL);
     RelooperAddBranch(block0, block2, NULL, NULL);
     RelooperAddBranch(block1, block2, NULL, NULL);
@@ -437,7 +448,7 @@ void test_relooper() {
 
   { // return in a block
     RelooperRef relooper = RelooperCreate();
-    BinaryenExpressionRef listList[] = { makeInt32(module, 42), BinaryenReturn(module, makeInt32(module, 1337)) };
+    BinaryenExpressionRef listList[] = { makeCallCheck(module,  42), BinaryenReturn(module, makeInt32(module, 1337)) };
     BinaryenExpressionRef list = BinaryenBlock(module, "the-list", listList, 2);
     RelooperBlockRef block = RelooperAddBlock(relooper, list);
     BinaryenExpressionRef body = RelooperRenderAndDispose(relooper, block, 0, module);
diff --git a/test/example/c-api-kitchen-sink.txt b/test/example/c-api-kitchen-sink.txt
index bd3b911f7..64f5fc3b4 100644
--- a/test/example/c-api-kitchen-sink.txt
+++ b/test/example/c-api-kitchen-sink.txt
@@ -370,40 +370,63 @@ raw:
 (module
   (memory 0)
   (type $v (func))
+  (type $vi (func (param i32)))
   (type $i (func (result i32)))
+  (import $check "module" "check" (param i32))
   (func $just-one-block (type $v)
     (local $0 i32)
-    (i32.const 1337)
+    (call_import $check
+      (i32.const 1337)
+    )
   )
   (func $two-blocks (type $v)
     (local $0 i32)
-    (block
-      (i32.const 0)
+    (block $block$2$break
+      (call_import $check
+        (i32.const 0)
+      )
+      (block
+        (br $block$2$break)
+      )
     )
     (block
-      (i32.const 1)
+      (call_import $check
+        (i32.const 1)
+      )
     )
   )
   (func $two-blocks-plus-code (type $v)
     (local $0 i32)
-    (block
-      (i32.const 0)
+    (block $block$2$break
+      (call_import $check
+        (i32.const 0)
+      )
       (block
         (i32.const 77)
+        (br $block$2$break)
       )
     )
     (block
-      (i32.const 1)
+      (call_import $check
+        (i32.const 1)
+      )
     )
   )
   (func $loop (type $v)
     (local $0 i32)
-    (loop $shape$0$break $shape$0$continue
-      (block
-        (i32.const 0)
+    (loop $shape$0$continue
+      (block $block$2$break
+        (call_import $check
+          (i32.const 0)
+        )
+        (block
+          (br $block$2$break)
+        )
       )
       (block
-        (i32.const 1)
+        (call_import $check
+          (i32.const 1)
+        )
         (block
           (br $shape$0$continue)
         )
@@ -412,15 +435,20 @@ raw:
   )
   (func $loop-plus-code (type $v)
     (local $0 i32)
-    (loop $shape$0$break $shape$0$continue
-      (block
-        (i32.const 0)
+    (loop $shape$0$continue
+      (block $block$2$break
+        (call_import $check
+          (i32.const 0)
+        )
         (block
           (i32.const 33)
+          (br $block$2$break)
         )
       )
       (block
-        (i32.const 1)
+        (call_import $check
+          (i32.const 1)
+        )
         (block
           (i32.const -66)
           (br $shape$0$continue)
@@ -430,14 +458,18 @@ raw:
   )
   (func $split (type $v)
     (local $0 i32)
-    (i32.const 0)
-    (block $shape$1$break
-      (if
-        (i32.const 55)
-        (block
+    (call_import $check
+      (i32.const 0)
+    )
+    (if
+      (i32.const 55)
+      (block
+        (call_import $check
           (i32.const 1)
         )
-        (block
+      )
+      (block
+        (call_import $check
           (i32.const 2)
         )
       )
@@ -445,19 +477,23 @@ raw:
   )
   (func $split-plus-code (type $v)
     (local $0 i32)
-    (i32.const 0)
-    (block $shape$1$break
-      (if
-        (i32.const 55)
+    (call_import $check
+      (i32.const 0)
+    )
+    (if
+      (i32.const 55)
+      (block
+        (i32.const 10)
         (block
-          (i32.const 10)
-          (block
+          (call_import $check
             (i32.const 1)
           )
         )
+      )
+      (block
+        (i32.const 20)
         (block
-          (i32.const 20)
-          (block
+          (call_import $check
             (i32.const 2)
           )
         )
@@ -466,166 +502,197 @@ raw:
   )
   (func $if (type $v)
     (local $0 i32)
-    (block
-      (i32.const 0)
-      (block $shape$1$break
-        (if
-          (i32.const 55)
-          (block
+    (block $block$3$break
+      (call_import $check
+        (i32.const 0)
+      )
+      (if
+        (i32.const 55)
+        (block
+          (call_import $check
             (i32.const 1)
-            (block
-              (br $shape$1$break)
-            )
+          )
+          (block
+            (br $block$3$break)
           )
         )
+        (br $block$3$break)
       )
     )
     (block
-      (i32.const 2)
+      (call_import $check
+        (i32.const 2)
+      )
     )
   )
   (func $if-plus-code (type $v)
     (local $0 i32)
-    (block
-      (i32.const 0)
-      (block $shape$1$break
-        (if
-          (i32.const 55)
+    (block $block$3$break
+      (call_import $check
+        (i32.const 0)
+      )
+      (if
+        (i32.const 55)
+        (block
+          (i32.const -1)
           (block
-            (i32.const -1)
-            (block
+            (call_import $check
               (i32.const 1)
-              (block
-                (i32.const -3)
-                (br $shape$1$break)
-              )
+            )
+            (block
+              (i32.const -3)
+              (br $block$3$break)
             )
           )
+        )
+        (block
           (i32.const -2)
+          (br $block$3$break)
         )
       )
     )
     (block
-      (i32.const 2)
+      (call_import $check
+        (i32.const 2)
+      )
     )
   )
   (func $if-else (type $v)
     (local $0 i32)
-    (block
-      (i32.const 0)
-      (block $shape$1$break
-        (if
-          (i32.const 55)
-          (block
+    (block $block$4$break
+      (call_import $check
+        (i32.const 0)
+      )
+      (if
+        (i32.const 55)
+        (block
+          (call_import $check
             (i32.const 1)
-            (block
-              (br $shape$1$break)
-            )
           )
           (block
+            (br $block$4$break)
+          )
+        )
+        (block
+          (call_import $check
             (i32.const 2)
-            (block
-              (br $shape$1$break)
-            )
+          )
+          (block
+            (br $block$4$break)
           )
         )
       )
     )
     (block
-      (i32.const 3)
+      (call_import $check
+        (i32.const 3)
+      )
     )
   )
   (func $loop-tail (type $v)
     (local $0 i32)
-    (loop $shape$0$break $shape$0$continue
-      (block
-        (i32.const 0)
-      )
-      (block
-        (i32.const 1)
-        (if
-          (i32.const 10)
-          (br $shape$0$continue)
-          (br $shape$0$break)
+    (block $block$3$break
+      (loop $shape$0$continue
+        (block $block$2$break
+          (call_import $check
+            (i32.const 0)
+          )
+          (block
+            (br $block$2$break)
+          )
+        )
+        (block
+          (call_import $check
+            (i32.const 1)
+          )
+          (if
+            (i32.const 10)
+            (br $shape$0$continue)
+            (br $block$3$break)
+          )
         )
       )
     )
     (block
-      (i32.const 2)
+      (call_import $check
+        (i32.const 2)
+      )
     )
   )
   (func $nontrivial-loop-plus-phi-to-head (type $v)
     (local $0 i32)
-    (block
-      (i32.const 0)
+    (block $block$2$break
+      (call_import $check
+        (i32.const 0)
+      )
       (block
         (i32.const 10)
+        (br $block$2$break)
       )
     )
     (block
-      (loop $shape$1$break $shape$1$continue
-        (block
-          (i32.const 1)
-          (if
-            (i32.eqz
-              (i32.const -2)
-            )
-            (block
-              (i32.const 20)
-              (br $shape$1$break)
-            )
-          )
-        )
-        (block
-          (i32.const 2)
-          (if
-            (i32.const -6)
-            (block
-              (set_local $0
-                (i32.const 4)
+      (block $block$7$break
+        (block $block$4$break
+          (loop $shape$1$continue
+            (block $block$3$break
+              (call_import $check
+                (i32.const 1)
+              )
+              (if
+                (i32.const -2)
+                (br $block$3$break)
+                (block
+                  (i32.const 20)
+                  (br $block$7$break)
+                )
               )
-              (br $shape$1$break)
             )
             (block
-              (i32.const 30)
-              (br $shape$1$continue)
+              (call_import $check
+                (i32.const 2)
+              )
+              (if
+                (i32.const -6)
+                (br $block$4$break)
+                (block
+                  (i32.const 30)
+                  (br $shape$1$continue)
+                )
+              )
             )
           )
         )
-      )
-      (block
-        (block $shape$4$break
-          (if
-            (i32.eq
-              (get_local $0)
-              (i32.const 4)
+        (block
+          (block $block$6$break
+            (call_import $check
+              (i32.const 3)
             )
-            (block
+            (if
+              (i32.const -10)
               (block
-                (i32.const 3)
-                (block $shape$6$break
-                  (if
-                    (i32.const -10)
-                    (block
-                      (i32.const 4)
-                      (block
-                        (br $shape$6$break)
-                      )
-                    )
-                  )
+                (call_import $check
+                  (i32.const 4)
                 )
-              )
-              (block
-                (i32.const 5)
                 (block
-                  (i32.const 40)
-                  (br $shape$4$break)
+                  (br $block$6$break)
                 )
               )
+              (br $block$6$break)
+            )
+          )
+          (block
+            (call_import $check
+              (i32.const 5)
+            )
+            (block
+              (i32.const 40)
+              (br $block$7$break)
             )
           )
         )
-        (block
+      )
+      (block
+        (call_import $check
           (i32.const 6)
         )
       )
@@ -633,38 +700,44 @@ raw:
   )
   (func $switch (type $v)
     (local $0 i32)
-    (i32.const 0)
-    (block $shape$1$break
-      (block $switch$1$leave
-        (block $switch$1$default
-          (block $switch$1$case$3
-            (block $switch$1$case$2
-              (br_table $switch$1$default $switch$1$default $switch$1$case$2 $switch$1$default $switch$1$case$3 $switch$1$case$2 $switch$1$default
-                (i32.const -99)
-              )
+    (call_import $check
+      (i32.const 0)
+    )
+    (block $switch$1$leave
+      (block $switch$1$default
+        (block $switch$1$case$3
+          (block $switch$1$case$2
+            (br_table $switch$1$default $switch$1$default $switch$1$case$2 $switch$1$default $switch$1$case$3 $switch$1$case$2 $switch$1$default
+              (i32.const -99)
             )
+          )
+          (block
             (block
-              (block
+              (call_import $check
                 (i32.const 1)
               )
             )
-            (br $switch$1$leave)
           )
+          (br $switch$1$leave)
+        )
+        (block
+          (i32.const 55)
           (block
-            (i32.const 55)
-            (block
+            (call_import $check
               (i32.const 2)
             )
           )
-          (br $switch$1$leave)
         )
+        (br $switch$1$leave)
+      )
+      (block
         (block
-          (block
+          (call_import $check
             (i32.const 3)
           )
         )
-        (br $switch$1$leave)
       )
+      (br $switch$1$leave)
     )
   )
   (func $duffs-device (type $v)
@@ -676,52 +749,66 @@ raw:
     (local $5 f64)
     (local $6 i32)
     (block
-      (i32.const 0)
+      (block $block$3$break
+        (block $block$2$break
+          (call_import $check
+            (i32.const 0)
+          )
+          (if
+            (i32.const 10)
+            (block
+              (set_local $3
+                (i32.const 2)
+              )
+              (br $block$2$break)
+            )
+            (block
+              (set_local $3
+                (i32.const 3)
+              )
+              (br $block$3$break)
+            )
+          )
+        )
+      )
+    )
+    (loop $shape$1$continue
       (if
-        (i32.const 10)
-        (set_local $3
+        (i32.eq
+          (get_local $3)
           (i32.const 2)
         )
-        (set_local $3
-          (i32.const 3)
+        (block
+          (set_local $3
+            (i32.const 0)
+          )
+          (call_import $check
+            (i32.const 1)
+          )
+          (block
+            (set_local $3
+              (i32.const 3)
+            )
+            (br $shape$1$continue)
+          )
         )
-      )
-    )
-    (loop $shape$1$break $shape$1$continue
-      (block $shape$2$break
         (if
           (i32.eq
             (get_local $3)
-            (i32.const 2)
+            (i32.const 3)
           )
           (block
             (set_local $3
               (i32.const 0)
             )
-            (i32.const 1)
-            (block
-              (set_local $3
-                (i32.const 3)
-              )
-              (br $shape$1$continue)
-            )
-          )
-          (if
-            (i32.eq
-              (get_local $3)
-              (i32.const 3)
+            (call_import $check
+              (i32.const 2)
             )
             (block
               (set_local $3
-                (i32.const 0)
-              )
-              (i32.const 2)
-              (block
-                (set_local $3
-                  (i32.const 2)
-                )
-                (br $shape$1$continue)
+                (i32.const 2)
               )
+              (br $shape$1$continue)
             )
           )
         )
@@ -731,7 +818,9 @@ raw:
   (func $return (type $i) (result i32)
     (local $0 i32)
     (block $the-list
-      (i32.const 42)
+      (call_import $check
+        (i32.const 42)
+      )
       (return
         (i32.const 1337)
       )
@@ -742,22 +831,179 @@ optimized:
 (module
   (memory 0)
   (type $v (func))
+  (type $vi (func (param i32)))
   (type $i (func (result i32)))
+  (import $check "module" "check" (param i32))
   (func $just-one-block (type $v)
-    (nop)
+    (call_import $check
+      (i32.const 1337)
+    )
+  )
+  (func $two-blocks (type $v)
+    (call_import $check
+      (i32.const 0)
+    )
+    (call_import $check
+      (i32.const 1)
+    )
+  )
+  (func $loop (type $v)
+    (loop $shape$0$continue
+      (call_import $check
+        (i32.const 0)
+      )
+      (call_import $check
+        (i32.const 1)
+      )
+      (br $shape$0$continue)
+    )
+  )
+  (func $split (type $v)
+    (call_import $check
+      (i32.const 0)
+    )
+    (if
+      (i32.const 55)
+      (call_import $check
+        (i32.const 1)
+      )
+      (call_import $check
+        (i32.const 2)
+      )
+    )
+  )
+  (func $if (type $v)
+    (call_import $check
+      (i32.const 0)
+    )
+    (if
+      (i32.const 55)
+      (call_import $check
+        (i32.const 1)
+      )
+    )
+    (call_import $check
+      (i32.const 2)
+    )
+  )
+  (func $if-else (type $v)
+    (call_import $check
+      (i32.const 0)
+    )
+    (if
+      (i32.const 55)
+      (call_import $check
+        (i32.const 1)
+      )
+      (call_import $check
+        (i32.const 2)
+      )
+    )
+    (call_import $check
+      (i32.const 3)
+    )
+  )
+  (func $loop-tail (type $v)
+    (loop $block$3$break $shape$0$continue
+      (call_import $check
+        (i32.const 0)
+      )
+      (call_import $check
+        (i32.const 1)
+      )
+      (if
+        (i32.const 10)
+        (br $shape$0$continue)
+        (br $block$3$break)
+      )
+    )
+    (call_import $check
+      (i32.const 2)
+    )
+  )
+  (func $nontrivial-loop-plus-phi-to-head (type $v)
+    (call_import $check
+      (i32.const 0)
+    )
+    (block $block$7$break
+      (loop $block$4$break $shape$1$continue
+        (call_import $check
+          (i32.const 1)
+        )
+        (br_if $block$7$break
+          (i32.const 0)
+        )
+        (call_import $check
+          (i32.const 2)
+        )
+        (if
+          (i32.const -6)
+          (br $block$4$break)
+          (br $shape$1$continue)
+        )
+      )
+      (call_import $check
+        (i32.const 3)
+      )
+      (if
+        (i32.const -10)
+        (call_import $check
+          (i32.const 4)
+        )
+      )
+      (call_import $check
+        (i32.const 5)
+      )
+    )
+    (call_import $check
+      (i32.const 6)
+    )
+  )
+  (func $switch (type $v)
+    (call_import $check
+      (i32.const 0)
+    )
+    (block $switch$1$leave
+      (block $switch$1$default
+        (block $switch$1$case$3
+          (block $switch$1$case$2
+            (br_table $switch$1$default $switch$1$default $switch$1$case$2 $switch$1$default $switch$1$case$3 $switch$1$case$2 $switch$1$default
+              (i32.const -99)
+            )
+          )
+          (call_import $check
+            (i32.const 1)
+          )
+          (br $switch$1$leave)
+        )
+        (call_import $check
+          (i32.const 2)
+        )
+        (br $switch$1$leave)
+      )
+      (call_import $check
+        (i32.const 3)
+      )
+    )
   )
   (func $duffs-device (type $v)
     (local $0 i32)
+    (call_import $check
+      (i32.const 0)
+    )
     (set_local $0
       (i32.const 2)
     )
-    (loop $shape$1$break $shape$1$continue
+    (loop $shape$1$continue
       (if
         (i32.eq
           (get_local $0)
           (i32.const 2)
         )
         (block
+          (call_import $check
+            (i32.const 1)
+          )
           (set_local $0
             (i32.const 3)
           )
@@ -769,6 +1015,9 @@ optimized:
             (i32.const 3)
           )
           (block
+            (call_import $check
+              (i32.const 2)
+            )
             (set_local $0
               (i32.const 2)
             )
@@ -779,6 +1028,9 @@ optimized:
     )
   )
   (func $return (type $i) (result i32)
+    (call_import $check
+      (i32.const 42)
+    )
     (i32.const 1337)
   )
 )
@@ -1517,303 +1769,503 @@ int main() {
     BinaryenIndex paramTypes[] = { 0 };
     functionTypes[0] = BinaryenAddFunctionType(the_module, "v", 0, paramTypes, 0);
   }
+  {
+    BinaryenIndex paramTypes[] = { 1 };
+    functionTypes[1] = BinaryenAddFunctionType(the_module, "vi", 0, paramTypes, 1);
+  }
+  BinaryenAddImport(the_module, "check", "module", "check", functionTypes[1]);
   the_relooper = RelooperCreate();
   expressions[1] = BinaryenConst(the_module, BinaryenLiteralInt32(1337));
-  relooperBlocks[0] = RelooperAddBlock(the_relooper, expressions[1]);
-  expressions[2] = RelooperRenderAndDispose(the_relooper, relooperBlocks[0], 0, the_module);
   {
-    BinaryenType varTypes[] = { 1 };
-    functions[0] = BinaryenAddFunction(the_module, "just-one-block", functionTypes[0], varTypes, 1, expressions[2]);
+    BinaryenExpressionRef operands[] = { expressions[1] };
+    expressions[2] = BinaryenCallImport(the_module, "check", operands, 1, 0);
   }
-  the_relooper = RelooperCreate();
-  expressions[3] = BinaryenConst(the_module, BinaryenLiteralInt32(0));
-  relooperBlocks[0] = RelooperAddBlock(the_relooper, expressions[3]);
-  expressions[4] = BinaryenConst(the_module, BinaryenLiteralInt32(1));
-  relooperBlocks[1] = RelooperAddBlock(the_relooper, expressions[4]);
-  RelooperAddBranch(relooperBlocks[0], relooperBlocks[1], expressions[0], expressions[0]);
-  expressions[5] = RelooperRenderAndDispose(the_relooper, relooperBlocks[0], 0, the_module);
+  relooperBlocks[0] = RelooperAddBlock(the_relooper, expressions[2]);
+  expressions[3] = RelooperRenderAndDispose(the_relooper, relooperBlocks[0], 0, the_module);
   {
     BinaryenType varTypes[] = { 1 };
-    functions[1] = BinaryenAddFunction(the_module, "two-blocks", functionTypes[0], varTypes, 1, expressions[5]);
+    functions[0] = BinaryenAddFunction(the_module, "just-one-block", functionTypes[0], varTypes, 1, expressions[3]);
   }
   the_relooper = RelooperCreate();
-  expressions[6] = BinaryenConst(the_module, BinaryenLiteralInt32(0));
-  relooperBlocks[0] = RelooperAddBlock(the_relooper, expressions[6]);
-  expressions[7] = BinaryenConst(the_module, BinaryenLiteralInt32(1));
+  expressions[4] = BinaryenConst(the_module, BinaryenLiteralInt32(0));
+  {
+    BinaryenExpressionRef operands[] = { expressions[4] };
+    expressions[5] = BinaryenCallImport(the_module, "check", operands, 1, 0);
+  }
+  relooperBlocks[0] = RelooperAddBlock(the_relooper, expressions[5]);
+  expressions[6] = BinaryenConst(the_module, BinaryenLiteralInt32(1));
+  {
+    BinaryenExpressionRef operands[] = { expressions[6] };
+    expressions[7] = BinaryenCallImport(the_module, "check", operands, 1, 0);
+  }
   relooperBlocks[1] = RelooperAddBlock(the_relooper, expressions[7]);
-  expressions[8] = BinaryenConst(the_module, BinaryenLiteralInt32(77));
-  RelooperAddBranch(relooperBlocks[0], relooperBlocks[1], expressions[0], expressions[8]);
-  expressions[9] = RelooperRenderAndDispose(the_relooper, relooperBlocks[0], 0, the_module);
+  RelooperAddBranch(relooperBlocks[0], relooperBlocks[1], expressions[0], expressions[0]);
+  expressions[8] = RelooperRenderAndDispose(the_relooper, relooperBlocks[0], 0, the_module);
   {
     BinaryenType varTypes[] = { 1 };
-    functions[2] = BinaryenAddFunction(the_module, "two-blocks-plus-code", functionTypes[0], varTypes, 1, expressions[9]);
+    functions[1] = BinaryenAddFunction(the_module, "two-blocks", functionTypes[0], varTypes, 1, expressions[8]);
   }
   the_relooper = RelooperCreate();
-  expressions[10] = BinaryenConst(the_module, BinaryenLiteralInt32(0));
+  expressions[9] = BinaryenConst(the_module, BinaryenLiteralInt32(0));
+  {
+    BinaryenExpressionRef operands[] = { expressions[9] };
+    expressions[10] = BinaryenCallImport(the_module, "check", operands, 1, 0);
+  }
   relooperBlocks[0] = RelooperAddBlock(the_relooper, expressions[10]);
   expressions[11] = BinaryenConst(the_module, BinaryenLiteralInt32(1));
-  relooperBlocks[1] = RelooperAddBlock(the_relooper, expressions[11]);
+  {
+    BinaryenExpressionRef operands[] = { expressions[11] };
+    expressions[12] = BinaryenCallImport(the_module, "check", operands, 1, 0);
+  }
+  relooperBlocks[1] = RelooperAddBlock(the_relooper, expressions[12]);
+  expressions[13] = BinaryenConst(the_module, BinaryenLiteralInt32(77));
+  RelooperAddBranch(relooperBlocks[0], relooperBlocks[1], expressions[0], expressions[13]);
+  expressions[14] = RelooperRenderAndDispose(the_relooper, relooperBlocks[0], 0, the_module);
+  {
+    BinaryenType varTypes[] = { 1 };
+    functions[2] = BinaryenAddFunction(the_module, "two-blocks-plus-code", functionTypes[0], varTypes, 1, expressions[14]);
+  }
+  the_relooper = RelooperCreate();
+  expressions[15] = BinaryenConst(the_module, BinaryenLiteralInt32(0));
+  {
+    BinaryenExpressionRef operands[] = { expressions[15] };
+    expressions[16] = BinaryenCallImport(the_module, "check", operands, 1, 0);
+  }
+  relooperBlocks[0] = RelooperAddBlock(the_relooper, expressions[16]);
+  expressions[17] = BinaryenConst(the_module, BinaryenLiteralInt32(1));
+  {
+    BinaryenExpressionRef operands[] = { expressions[17] };
+    expressions[18] = BinaryenCallImport(the_module, "check", operands, 1, 0);
+  }
+  relooperBlocks[1] = RelooperAddBlock(the_relooper, expressions[18]);
   RelooperAddBranch(relooperBlocks[0], relooperBlocks[1], expressions[0], expressions[0]);
   RelooperAddBranch(relooperBlocks[1], relooperBlocks[0], expressions[0], expressions[0]);
-  expressions[12] = RelooperRenderAndDispose(the_relooper, relooperBlocks[0], 0, the_module);
+  expressions[19] = RelooperRenderAndDispose(the_relooper, relooperBlocks[0], 0, the_module);
   {
     BinaryenType varTypes[] = { 1 };
-    functions[3] = BinaryenAddFunction(the_module, "loop", functionTypes[0], varTypes, 1, expressions[12]);
+    functions[3] = BinaryenAddFunction(the_module, "loop", functionTypes[0], varTypes, 1, expressions[19]);
   }
   the_relooper = RelooperCreate();
-  expressions[13] = BinaryenConst(the_module, BinaryenLiteralInt32(0));
-  relooperBlocks[0] = RelooperAddBlock(the_relooper, expressions[13]);
-  expressions[14] = BinaryenConst(the_module, BinaryenLiteralInt32(1));
-  relooperBlocks[1] = RelooperAddBlock(the_relooper, expressions[14]);
-  expressions[15] = BinaryenConst(the_module, BinaryenLiteralInt32(33));
-  RelooperAddBranch(relooperBlocks[0], relooperBlocks[1], expressions[0], expressions[15]);
-  expressions[16] = BinaryenConst(the_module, BinaryenLiteralInt32(-66));
-  RelooperAddBranch(relooperBlocks[1], relooperBlocks[0], expressions[0], expressions[16]);
-  expressions[17] = RelooperRenderAndDispose(the_relooper, relooperBlocks[0], 0, the_module);
+  expressions[20] = BinaryenConst(the_module, BinaryenLiteralInt32(0));
+  {
+    BinaryenExpressionRef operands[] = { expressions[20] };
+    expressions[21] = BinaryenCallImport(the_module, "check", operands, 1, 0);
+  }
+  relooperBlocks[0] = RelooperAddBlock(the_relooper, expressions[21]);
+  expressions[22] = BinaryenConst(the_module, BinaryenLiteralInt32(1));
+  {
+    BinaryenExpressionRef operands[] = { expressions[22] };
+    expressions[23] = BinaryenCallImport(the_module, "check", operands, 1, 0);
+  }
+  relooperBlocks[1] = RelooperAddBlock(the_relooper, expressions[23]);
+  expressions[24] = BinaryenConst(the_module, BinaryenLiteralInt32(33));
+  RelooperAddBranch(relooperBlocks[0], relooperBlocks[1], expressions[0], expressions[24]);
+  expressions[25] = BinaryenConst(the_module, BinaryenLiteralInt32(-66));
+  RelooperAddBranch(relooperBlocks[1], relooperBlocks[0], expressions[0], expressions[25]);
+  expressions[26] = RelooperRenderAndDispose(the_relooper, relooperBlocks[0], 0, the_module);
   {
     BinaryenType varTypes[] = { 1 };
-    functions[4] = BinaryenAddFunction(the_module, "loop-plus-code", functionTypes[0], varTypes, 1, expressions[17]);
+    functions[4] = BinaryenAddFunction(the_module, "loop-plus-code", functionTypes[0], varTypes, 1, expressions[26]);
   }
   the_relooper = RelooperCreate();
-  expressions[18] = BinaryenConst(the_module, BinaryenLiteralInt32(0));
-  relooperBlocks[0] = RelooperAddBlock(the_relooper, expressions[18]);
-  expressions[19] = BinaryenConst(the_module, BinaryenLiteralInt32(1));
-  relooperBlocks[1] = RelooperAddBlock(the_relooper, expressions[19]);
-  expressions[20] = BinaryenConst(the_module, BinaryenLiteralInt32(2));
-  relooperBlocks[2] = RelooperAddBlock(the_relooper, expressions[20]);
-  expressions[21] = BinaryenConst(the_module, BinaryenLiteralInt32(55));
-  RelooperAddBranch(relooperBlocks[0], relooperBlocks[1], expressions[21], expressions[0]);
+  expressions[27] = BinaryenConst(the_module, BinaryenLiteralInt32(0));
+  {
+    BinaryenExpressionRef operands[] = { expressions[27] };
+    expressions[28] = BinaryenCallImport(the_module, "check", operands, 1, 0);
+  }
+  relooperBlocks[0] = RelooperAddBlock(the_relooper, expressions[28]);
+  expressions[29] = BinaryenConst(the_module, BinaryenLiteralInt32(1));
+  {
+    BinaryenExpressionRef operands[] = { expressions[29] };
+    expressions[30] = BinaryenCallImport(the_module, "check", operands, 1, 0);
+  }
+  relooperBlocks[1] = RelooperAddBlock(the_relooper, expressions[30]);
+  expressions[31] = BinaryenConst(the_module, BinaryenLiteralInt32(2));
+  {
+    BinaryenExpressionRef operands[] = { expressions[31] };
+    expressions[32] = BinaryenCallImport(the_module, "check", operands, 1, 0);
+  }
+  relooperBlocks[2] = RelooperAddBlock(the_relooper, expressions[32]);
+  expressions[33] = BinaryenConst(the_module, BinaryenLiteralInt32(55));
+  RelooperAddBranch(relooperBlocks[0], relooperBlocks[1], expressions[33], expressions[0]);
   RelooperAddBranch(relooperBlocks[0], relooperBlocks[2], expressions[0], expressions[0]);
-  expressions[22] = RelooperRenderAndDispose(the_relooper, relooperBlocks[0], 0, the_module);
+  expressions[34] = RelooperRenderAndDispose(the_relooper, relooperBlocks[0], 0, the_module);
   {
     BinaryenType varTypes[] = { 1 };
-    functions[5] = BinaryenAddFunction(the_module, "split", functionTypes[0], varTypes, 1, expressions[22]);
+    functions[5] = BinaryenAddFunction(the_module, "split", functionTypes[0], varTypes, 1, expressions[34]);
   }
   the_relooper = RelooperCreate();
-  expressions[23] = BinaryenConst(the_module, BinaryenLiteralInt32(0));
-  relooperBlocks[0] = RelooperAddBlock(the_relooper, expressions[23]);
-  expressions[24] = BinaryenConst(the_module, BinaryenLiteralInt32(1));
-  relooperBlocks[1] = RelooperAddBlock(the_relooper, expressions[24]);
-  expressions[25] = BinaryenConst(the_module, BinaryenLiteralInt32(2));
-  relooperBlocks[2] = RelooperAddBlock(the_relooper, expressions[25]);
-  expressions[26] = BinaryenConst(the_module, BinaryenLiteralInt32(10));
-  expressions[27] = BinaryenConst(the_module, BinaryenLiteralInt32(55));
-  RelooperAddBranch(relooperBlocks[0], relooperBlocks[1], expressions[27], expressions[26]);
-  expressions[28] = BinaryenConst(the_module, BinaryenLiteralInt32(20));
-  RelooperAddBranch(relooperBlocks[0], relooperBlocks[2], expressions[0], expressions[28]);
-  expressions[29] = RelooperRenderAndDispose(the_relooper, relooperBlocks[0], 0, the_module);
+  expressions[35] = BinaryenConst(the_module, BinaryenLiteralInt32(0));
+  {
+    BinaryenExpressionRef operands[] = { expressions[35] };
+    expressions[36] = BinaryenCallImport(the_module, "check", operands, 1, 0);
+  }
+  relooperBlocks[0] = RelooperAddBlock(the_relooper, expressions[36]);
+  expressions[37] = BinaryenConst(the_module, BinaryenLiteralInt32(1));
+  {
+    BinaryenExpressionRef operands[] = { expressions[37] };
+    expressions[38] = BinaryenCallImport(the_module, "check", operands, 1, 0);
+  }
+  relooperBlocks[1] = RelooperAddBlock(the_relooper, expressions[38]);
+  expressions[39] = BinaryenConst(the_module, BinaryenLiteralInt32(2));
+  {
+    BinaryenExpressionRef operands[] = { expressions[39] };
+    expressions[40] = BinaryenCallImport(the_module, "check", operands, 1, 0);
+  }
+  relooperBlocks[2] = RelooperAddBlock(the_relooper, expressions[40]);
+  expressions[41] = BinaryenConst(the_module, BinaryenLiteralInt32(10));
+  expressions[42] = BinaryenConst(the_module, BinaryenLiteralInt32(55));
+  RelooperAddBranch(relooperBlocks[0], relooperBlocks[1], expressions[42], expressions[41]);
+  expressions[43] = BinaryenConst(the_module, BinaryenLiteralInt32(20));
+  RelooperAddBranch(relooperBlocks[0], relooperBlocks[2], expressions[0], expressions[43]);
+  expressions[44] = RelooperRenderAndDispose(the_relooper, relooperBlocks[0], 0, the_module);
   {
     BinaryenType varTypes[] = { 1 };
-    functions[6] = BinaryenAddFunction(the_module, "split-plus-code", functionTypes[0], varTypes, 1, expressions[29]);
+    functions[6] = BinaryenAddFunction(the_module, "split-plus-code", functionTypes[0], varTypes, 1, expressions[44]);
   }
   the_relooper = RelooperCreate();
-  expressions[30] = BinaryenConst(the_module, BinaryenLiteralInt32(0));
-  relooperBlocks[0] = RelooperAddBlock(the_relooper, expressions[30]);
-  expressions[31] = BinaryenConst(the_module, BinaryenLiteralInt32(1));
-  relooperBlocks[1] = RelooperAddBlock(the_relooper, expressions[31]);
-  expressions[32] = BinaryenConst(the_module, BinaryenLiteralInt32(2));
-  relooperBlocks[2] = RelooperAddBlock(the_relooper, expressions[32]);
-  expressions[33] = BinaryenConst(the_module, BinaryenLiteralInt32(55));
-  RelooperAddBranch(relooperBlocks[0], relooperBlocks[1], expressions[33], expressions[0]);
+  expressions[45] = BinaryenConst(the_module, BinaryenLiteralInt32(0));
+  {
+    BinaryenExpressionRef operands[] = { expressions[45] };
+    expressions[46] = BinaryenCallImport(the_module, "check", operands, 1, 0);
+  }
+  relooperBlocks[0] = RelooperAddBlock(the_relooper, expressions[46]);
+  expressions[47] = BinaryenConst(the_module, BinaryenLiteralInt32(1));
+  {
+    BinaryenExpressionRef operands[] = { expressions[47] };
+    expressions[48] = BinaryenCallImport(the_module, "check", operands, 1, 0);
+  }
+  relooperBlocks[1] = RelooperAddBlock(the_relooper, expressions[48]);
+  expressions[49] = BinaryenConst(the_module, BinaryenLiteralInt32(2));
+  {
+    BinaryenExpressionRef operands[] = { expressions[49] };
+    expressions[50] = BinaryenCallImport(the_module, "check", operands, 1, 0);
+  }
+  relooperBlocks[2] = RelooperAddBlock(the_relooper, expressions[50]);
+  expressions[51] = BinaryenConst(the_module, BinaryenLiteralInt32(55));
+  RelooperAddBranch(relooperBlocks[0], relooperBlocks[1], expressions[51], expressions[0]);
   RelooperAddBranch(relooperBlocks[0], relooperBlocks[2], expressions[0], expressions[0]);
   RelooperAddBranch(relooperBlocks[1], relooperBlocks[2], expressions[0], expressions[0]);
-  expressions[34] = RelooperRenderAndDispose(the_relooper, relooperBlocks[0], 0, the_module);
+  expressions[52] = RelooperRenderAndDispose(the_relooper, relooperBlocks[0], 0, the_module);
   {
     BinaryenType varTypes[] = { 1 };
-    functions[7] = BinaryenAddFunction(the_module, "if", functionTypes[0], varTypes, 1, expressions[34]);
+    functions[7] = BinaryenAddFunction(the_module, "if", functionTypes[0], varTypes, 1, expressions[52]);
   }
   the_relooper = RelooperCreate();
-  expressions[35] = BinaryenConst(the_module, BinaryenLiteralInt32(0));
-  relooperBlocks[0] = RelooperAddBlock(the_relooper, expressions[35]);
-  expressions[36] = BinaryenConst(the_module, BinaryenLiteralInt32(1));
-  relooperBlocks[1] = RelooperAddBlock(the_relooper, expressions[36]);
-  expressions[37] = BinaryenConst(the_module, BinaryenLiteralInt32(2));
-  relooperBlocks[2] = RelooperAddBlock(the_relooper, expressions[37]);
-  expressions[38] = BinaryenConst(the_module, BinaryenLiteralInt32(-1));
-  expressions[39] = BinaryenConst(the_module, BinaryenLiteralInt32(55));
-  RelooperAddBranch(relooperBlocks[0], relooperBlocks[1], expressions[39], expressions[38]);
-  expressions[40] = BinaryenConst(the_module, BinaryenLiteralInt32(-2));
-  RelooperAddBranch(relooperBlocks[0], relooperBlocks[2], expressions[0], expressions[40]);
-  expressions[41] = BinaryenConst(the_module, BinaryenLiteralInt32(-3));
-  RelooperAddBranch(relooperBlocks[1], relooperBlocks[2], expressions[0], expressions[41]);
-  expressions[42] = RelooperRenderAndDispose(the_relooper, relooperBlocks[0], 0, the_module);
+  expressions[53] = BinaryenConst(the_module, BinaryenLiteralInt32(0));
+  {
+    BinaryenExpressionRef operands[] = { expressions[53] };
+    expressions[54] = BinaryenCallImport(the_module, "check", operands, 1, 0);
+  }
+  relooperBlocks[0] = RelooperAddBlock(the_relooper, expressions[54]);
+  expressions[55] = BinaryenConst(the_module, BinaryenLiteralInt32(1));
+  {
+    BinaryenExpressionRef operands[] = { expressions[55] };
+    expressions[56] = BinaryenCallImport(the_module, "check", operands, 1, 0);
+  }
+  relooperBlocks[1] = RelooperAddBlock(the_relooper, expressions[56]);
+  expressions[57] = BinaryenConst(the_module, BinaryenLiteralInt32(2));
+  {
+    BinaryenExpressionRef operands[] = { expressions[57] };
+    expressions[58] = BinaryenCallImport(the_module, "check", operands, 1, 0);
+  }
+  relooperBlocks[2] = RelooperAddBlock(the_relooper, expressions[58]);
+  expressions[59] = BinaryenConst(the_module, BinaryenLiteralInt32(-1));
+  expressions[60] = BinaryenConst(the_module, BinaryenLiteralInt32(55));
+  RelooperAddBranch(relooperBlocks[0], relooperBlocks[1], expressions[60], expressions[59]);
+  expressions[61] = BinaryenConst(the_module, BinaryenLiteralInt32(-2));
+  RelooperAddBranch(relooperBlocks[0], relooperBlocks[2], expressions[0], expressions[61]);
+  expressions[62] = BinaryenConst(the_module, BinaryenLiteralInt32(-3));
+  RelooperAddBranch(relooperBlocks[1], relooperBlocks[2], expressions[0], expressions[62]);
+  expressions[63] = RelooperRenderAndDispose(the_relooper, relooperBlocks[0], 0, the_module);
   {
     BinaryenType varTypes[] = { 1 };
-    functions[8] = BinaryenAddFunction(the_module, "if-plus-code", functionTypes[0], varTypes, 1, expressions[42]);
+    functions[8] = BinaryenAddFunction(the_module, "if-plus-code", functionTypes[0], varTypes, 1, expressions[63]);
   }
   the_relooper = RelooperCreate();
-  expressions[43] = BinaryenConst(the_module, BinaryenLiteralInt32(0));
-  relooperBlocks[0] = RelooperAddBlock(the_relooper, expressions[43]);
-  expressions[44] = BinaryenConst(the_module, BinaryenLiteralInt32(1));
-  relooperBlocks[1] = RelooperAddBlock(the_relooper, expressions[44]);
-  expressions[45] = BinaryenConst(the_module, BinaryenLiteralInt32(2));
-  relooperBlocks[2] = RelooperAddBlock(the_relooper, expressions[45]);
-  expressions[46] = BinaryenConst(the_module, BinaryenLiteralInt32(3));
-  relooperBlocks[3] = RelooperAddBlock(the_relooper, expressions[46]);
-  expressions[47] = BinaryenConst(the_module, BinaryenLiteralInt32(55));
-  RelooperAddBranch(relooperBlocks[0], relooperBlocks[1], expressions[47], expressions[0]);
+  expressions[64] = BinaryenConst(the_module, BinaryenLiteralInt32(0));
+  {
+    BinaryenExpressionRef operands[] = { expressions[64] };
+    expressions[65] = BinaryenCallImport(the_module, "check", operands, 1, 0);
+  }
+  relooperBlocks[0] = RelooperAddBlock(the_relooper, expressions[65]);
+  expressions[66] = BinaryenConst(the_module, BinaryenLiteralInt32(1));
+  {
+    BinaryenExpressionRef operands[] = { expressions[66] };
+    expressions[67] = BinaryenCallImport(the_module, "check", operands, 1, 0);
+  }
+  relooperBlocks[1] = RelooperAddBlock(the_relooper, expressions[67]);
+  expressions[68] = BinaryenConst(the_module, BinaryenLiteralInt32(2));
+  {
+    BinaryenExpressionRef operands[] = { expressions[68] };
+    expressions[69] = BinaryenCallImport(the_module, "check", operands, 1, 0);
+  }
+  relooperBlocks[2] = RelooperAddBlock(the_relooper, expressions[69]);
+  expressions[70] = BinaryenConst(the_module, BinaryenLiteralInt32(3));
+  {
+    BinaryenExpressionRef operands[] = { expressions[70] };
+    expressions[71] = BinaryenCallImport(the_module, "check", operands, 1, 0);
+  }
+  relooperBlocks[3] = RelooperAddBlock(the_relooper, expressions[71]);
+  expressions[72] = BinaryenConst(the_module, BinaryenLiteralInt32(55));
+  RelooperAddBranch(relooperBlocks[0], relooperBlocks[1], expressions[72], expressions[0]);
   RelooperAddBranch(relooperBlocks[0], relooperBlocks[2], expressions[0], expressions[0]);
   RelooperAddBranch(relooperBlocks[1], relooperBlocks[3], expressions[0], expressions[0]);
   RelooperAddBranch(relooperBlocks[2], relooperBlocks[3], expressions[0], expressions[0]);
-  expressions[48] = RelooperRenderAndDispose(the_relooper, relooperBlocks[0], 0, the_module);
+  expressions[73] = RelooperRenderAndDispose(the_relooper, relooperBlocks[0], 0, the_module);
   {
     BinaryenType varTypes[] = { 1 };
-    functions[9] = BinaryenAddFunction(the_module, "if-else", functionTypes[0], varTypes, 1, expressions[48]);
+    functions[9] = BinaryenAddFunction(the_module, "if-else", functionTypes[0], varTypes, 1, expressions[73]);
   }
   the_relooper = RelooperCreate();
-  expressions[49] = BinaryenConst(the_module, BinaryenLiteralInt32(0));
-  relooperBlocks[0] = RelooperAddBlock(the_relooper, expressions[49]);
-  expressions[50] = BinaryenConst(the_module, BinaryenLiteralInt32(1));
-  relooperBlocks[1] = RelooperAddBlock(the_relooper, expressions[50]);
-  expressions[51] = BinaryenConst(the_module, BinaryenLiteralInt32(2));
-  relooperBlocks[2] = RelooperAddBlock(the_relooper, expressions[51]);
+  expressions[74] = BinaryenConst(the_module, BinaryenLiteralInt32(0));
+  {
+    BinaryenExpressionRef operands[] = { expressions[74] };
+    expressions[75] = BinaryenCallImport(the_module, "check", operands, 1, 0);
+  }
+  relooperBlocks[0] = RelooperAddBlock(the_relooper, expressions[75]);
+  expressions[76] = BinaryenConst(the_module, BinaryenLiteralInt32(1));
+  {
+    BinaryenExpressionRef operands[] = { expressions[76] };
+    expressions[77] = BinaryenCallImport(the_module, "check", operands, 1, 0);
+  }
+  relooperBlocks[1] = RelooperAddBlock(the_relooper, expressions[77]);
+  expressions[78] = BinaryenConst(the_module, BinaryenLiteralInt32(2));
+  {
+    BinaryenExpressionRef operands[] = { expressions[78] };
+    expressions[79] = BinaryenCallImport(the_module, "check", operands, 1, 0);
+  }
+  relooperBlocks[2] = RelooperAddBlock(the_relooper, expressions[79]);
   RelooperAddBranch(relooperBlocks[0], relooperBlocks[1], expressions[0], expressions[0]);
-  expressions[52] = BinaryenConst(the_module, BinaryenLiteralInt32(10));
-  RelooperAddBranch(relooperBlocks[1], relooperBlocks[0], expressions[52], expressions[0]);
+  expressions[80] = BinaryenConst(the_module, BinaryenLiteralInt32(10));
+  RelooperAddBranch(relooperBlocks[1], relooperBlocks[0], expressions[80], expressions[0]);
   RelooperAddBranch(relooperBlocks[1], relooperBlocks[2], expressions[0], expressions[0]);
-  expressions[53] = RelooperRenderAndDispose(the_relooper, relooperBlocks[0], 0, the_module);
+  expressions[81] = RelooperRenderAndDispose(the_relooper, relooperBlocks[0], 0, the_module);
   {
     BinaryenType varTypes[] = { 1 };
-    functions[10] = BinaryenAddFunction(the_module, "loop-tail", functionTypes[0], varTypes, 1, expressions[53]);
+    functions[10] = BinaryenAddFunction(the_module, "loop-tail", functionTypes[0], varTypes, 1, expressions[81]);
   }
   the_relooper = RelooperCreate();
-  expressions[54] = BinaryenConst(the_module, BinaryenLiteralInt32(0));
-  relooperBlocks[0] = RelooperAddBlock(the_relooper, expressions[54]);
-  expressions[55] = BinaryenConst(the_module, BinaryenLiteralInt32(1));
-  relooperBlocks[1] = RelooperAddBlock(the_relooper, expressions[55]);
-  expressions[56] = BinaryenConst(the_module, BinaryenLiteralInt32(2));
-  relooperBlocks[2] = RelooperAddBlock(the_relooper, expressions[56]);
-  expressions[57] = BinaryenConst(the_module, BinaryenLiteralInt32(3));
-  relooperBlocks[3] = RelooperAddBlock(the_relooper, expressions[57]);
-  expressions[58] = BinaryenConst(the_module, BinaryenLiteralInt32(4));
-  relooperBlocks[4] = RelooperAddBlock(the_relooper, expressions[58]);
-  expressions[59] = BinaryenConst(the_module, BinaryenLiteralInt32(5));
-  relooperBlocks[5] = RelooperAddBlock(the_relooper, expressions[59]);
-  expressions[60] = BinaryenConst(the_module, BinaryenLiteralInt32(6));
-  relooperBlocks[6] = RelooperAddBlock(the_relooper, expressions[60]);
-  expressions[61] = BinaryenConst(the_module, BinaryenLiteralInt32(10));
-  RelooperAddBranch(relooperBlocks[0], relooperBlocks[1], expressions[0], expressions[61]);
-  expressions[62] = BinaryenConst(the_module, BinaryenLiteralInt32(-2));
-  RelooperAddBranch(relooperBlocks[1], relooperBlocks[2], expressions[62], expressions[0]);
-  expressions[63] = BinaryenConst(the_module, BinaryenLiteralInt32(20));
-  RelooperAddBranch(relooperBlocks[1], relooperBlocks[6], expressions[0], expressions[63]);
-  expressions[64] = BinaryenConst(the_module, BinaryenLiteralInt32(-6));
-  RelooperAddBranch(relooperBlocks[2], relooperBlocks[3], expressions[64], expressions[0]);
-  expressions[65] = BinaryenConst(the_module, BinaryenLiteralInt32(30));
-  RelooperAddBranch(relooperBlocks[2], relooperBlocks[1], expressions[0], expressions[65]);
-  expressions[66] = BinaryenConst(the_module, BinaryenLiteralInt32(-10));
-  RelooperAddBranch(relooperBlocks[3], relooperBlocks[4], expressions[66], expressions[0]);
+  expressions[82] = BinaryenConst(the_module, BinaryenLiteralInt32(0));
+  {
+    BinaryenExpressionRef operands[] = { expressions[82] };
+    expressions[83] = BinaryenCallImport(the_module, "check", operands, 1, 0);
+  }
+  relooperBlocks[0] = RelooperAddBlock(the_relooper, expressions[83]);
+  expressions[84] = BinaryenConst(the_module, BinaryenLiteralInt32(1));
+  {
+    BinaryenExpressionRef operands[] = { expressions[84] };
+    expressions[85] = BinaryenCallImport(the_module, "check", operands, 1, 0);
+  }
+  relooperBlocks[1] = RelooperAddBlock(the_relooper, expressions[85]);
+  expressions[86] = BinaryenConst(the_module, BinaryenLiteralInt32(2));
+  {
+    BinaryenExpressionRef operands[] = { expressions[86] };
+    expressions[87] = BinaryenCallImport(the_module, "check", operands, 1, 0);
+  }
+  relooperBlocks[2] = RelooperAddBlock(the_relooper, expressions[87]);
+  expressions[88] = BinaryenConst(the_module, BinaryenLiteralInt32(3));
+  {
+    BinaryenExpressionRef operands[] = { expressions[88] };
+    expressions[89] = BinaryenCallImport(the_module, "check", operands, 1, 0);
+  }
+  relooperBlocks[3] = RelooperAddBlock(the_relooper, expressions[89]);
+  expressions[90] = BinaryenConst(the_module, BinaryenLiteralInt32(4));
+  {
+    BinaryenExpressionRef operands[] = { expressions[90] };
+    expressions[91] = BinaryenCallImport(the_module, "check", operands, 1, 0);
+  }
+  relooperBlocks[4] = RelooperAddBlock(the_relooper, expressions[91]);
+  expressions[92] = BinaryenConst(the_module, BinaryenLiteralInt32(5));
+  {
+    BinaryenExpressionRef operands[] = { expressions[92] };
+    expressions[93] = BinaryenCallImport(the_module, "check", operands, 1, 0);
+  }
+  relooperBlocks[5] = RelooperAddBlock(the_relooper, expressions[93]);
+  expressions[94] = BinaryenConst(the_module, BinaryenLiteralInt32(6));
+  {
+    BinaryenExpressionRef operands[] = { expressions[94] };
+    expressions[95] = BinaryenCallImport(the_module, "check", operands, 1, 0);
+  }
+  relooperBlocks[6] = RelooperAddBlock(the_relooper, expressions[95]);
+  expressions[96] = BinaryenConst(the_module, BinaryenLiteralInt32(10));
+  RelooperAddBranch(relooperBlocks[0], relooperBlocks[1], expressions[0], expressions[96]);
+  expressions[97] = BinaryenConst(the_module, BinaryenLiteralInt32(-2));
+  RelooperAddBranch(relooperBlocks[1], relooperBlocks[2], expressions[97], expressions[0]);
+  expressions[98] = BinaryenConst(the_module, BinaryenLiteralInt32(20));
+  RelooperAddBranch(relooperBlocks[1], relooperBlocks[6], expressions[0], expressions[98]);
+  expressions[99] = BinaryenConst(the_module, BinaryenLiteralInt32(-6));
+  RelooperAddBranch(relooperBlocks[2], relooperBlocks[3], expressions[99], expressions[0]);
+  expressions[100] = BinaryenConst(the_module, BinaryenLiteralInt32(30));
+  RelooperAddBranch(relooperBlocks[2], relooperBlocks[1], expressions[0], expressions[100]);
+  expressions[101] = BinaryenConst(the_module, BinaryenLiteralInt32(-10));
+  RelooperAddBranch(relooperBlocks[3], relooperBlocks[4], expressions[101], expressions[0]);
   RelooperAddBranch(relooperBlocks[3], relooperBlocks[5], expressions[0], expressions[0]);
   RelooperAddBranch(relooperBlocks[4], relooperBlocks[5], expressions[0], expressions[0]);
-  expressions[67] = BinaryenConst(the_module, BinaryenLiteralInt32(40));
-  RelooperAddBranch(relooperBlocks[5], relooperBlocks[6], expressions[0], expressions[67]);
-  expressions[68] = RelooperRenderAndDispose(the_relooper, relooperBlocks[0], 0, the_module);
+  expressions[102] = BinaryenConst(the_module, BinaryenLiteralInt32(40));
+  RelooperAddBranch(relooperBlocks[5], relooperBlocks[6], expressions[0], expressions[102]);
+  expressions[103] = RelooperRenderAndDispose(the_relooper, relooperBlocks[0], 0, the_module);
   {
     BinaryenType varTypes[] = { 1 };
-    functions[11] = BinaryenAddFunction(the_module, "nontrivial-loop-plus-phi-to-head", functionTypes[0], varTypes, 1, expressions[68]);
+    functions[11] = BinaryenAddFunction(the_module, "nontrivial-loop-plus-phi-to-head", functionTypes[0], varTypes, 1, expressions[103]);
   }
   the_relooper = RelooperCreate();
-  expressions[69] = BinaryenConst(the_module, BinaryenLiteralInt32(-99));
-  expressions[70] = BinaryenConst(the_module, BinaryenLiteralInt32(0));
-  relooperBlocks[0] = RelooperAddBlockWithSwitch(the_relooper, expressions[70], expressions[69]);
-  expressions[71] = BinaryenConst(the_module, BinaryenLiteralInt32(1));
-  relooperBlocks[1] = RelooperAddBlock(the_relooper, expressions[71]);
-  expressions[72] = BinaryenConst(the_module, BinaryenLiteralInt32(2));
-  relooperBlocks[2] = RelooperAddBlock(the_relooper, expressions[72]);
-  expressions[73] = BinaryenConst(the_module, BinaryenLiteralInt32(3));
-  relooperBlocks[3] = RelooperAddBlock(the_relooper, expressions[73]);
+  expressions[104] = BinaryenConst(the_module, BinaryenLiteralInt32(-99));
+  expressions[105] = BinaryenConst(the_module, BinaryenLiteralInt32(0));
+  {
+    BinaryenExpressionRef operands[] = { expressions[105] };
+    expressions[106] = BinaryenCallImport(the_module, "check", operands, 1, 0);
+  }
+  relooperBlocks[0] = RelooperAddBlockWithSwitch(the_relooper, expressions[106], expressions[104]);
+  expressions[107] = BinaryenConst(the_module, BinaryenLiteralInt32(1));
+  {
+    BinaryenExpressionRef operands[] = { expressions[107] };
+    expressions[108] = BinaryenCallImport(the_module, "check", operands, 1, 0);
+  }
+  relooperBlocks[1] = RelooperAddBlock(the_relooper, expressions[108]);
+  expressions[109] = BinaryenConst(the_module, BinaryenLiteralInt32(2));
+  {
+    BinaryenExpressionRef operands[] = { expressions[109] };
+    expressions[110] = BinaryenCallImport(the_module, "check", operands, 1, 0);
+  }
+  relooperBlocks[2] = RelooperAddBlock(the_relooper, expressions[110]);
+  expressions[111] = BinaryenConst(the_module, BinaryenLiteralInt32(3));
+  {
+    BinaryenExpressionRef operands[] = { expressions[111] };
+    expressions[112] = BinaryenCallImport(the_module, "check", operands, 1, 0);
+  }
+  relooperBlocks[3] = RelooperAddBlock(the_relooper, expressions[112]);
   {
     BinaryenIndex indexes[] = { 2, 5 };
     RelooperAddBranchForSwitch(relooperBlocks[0], relooperBlocks[1], indexes, 2, expressions[0]);
   }
-  expressions[74] = BinaryenConst(the_module, BinaryenLiteralInt32(55));
+  expressions[113] = BinaryenConst(the_module, BinaryenLiteralInt32(55));
   {
     BinaryenIndex indexes[] = { 4 };
-    RelooperAddBranchForSwitch(relooperBlocks[0], relooperBlocks[2], indexes, 1, expressions[74]);
+    RelooperAddBranchForSwitch(relooperBlocks[0], relooperBlocks[2], indexes, 1, expressions[113]);
   }
   {
     BinaryenIndex indexes[] = { 0 };
     RelooperAddBranchForSwitch(relooperBlocks[0], relooperBlocks[3], indexes, 0, expressions[0]);
   }
-  expressions[75] = RelooperRenderAndDispose(the_relooper, relooperBlocks[0], 0, the_module);
+  expressions[114] = RelooperRenderAndDispose(the_relooper, relooperBlocks[0], 0, the_module);
   {
     BinaryenType varTypes[] = { 1 };
-    functions[12] = BinaryenAddFunction(the_module, "switch", functionTypes[0], varTypes, 1, expressions[75]);
+    functions[12] = BinaryenAddFunction(the_module, "switch", functionTypes[0], varTypes, 1, expressions[114]);
   }
   the_relooper = RelooperCreate();
-  expressions[76] = BinaryenConst(the_module, BinaryenLiteralInt32(0));
-  relooperBlocks[0] = RelooperAddBlock(the_relooper, expressions[76]);
-  expressions[77] = BinaryenConst(the_module, BinaryenLiteralInt32(1));
-  relooperBlocks[1] = RelooperAddBlock(the_relooper, expressions[77]);
-  expressions[78] = BinaryenConst(the_module, BinaryenLiteralInt32(2));
-  relooperBlocks[2] = RelooperAddBlock(the_relooper, expressions[78]);
-  expressions[79] = BinaryenConst(the_module, BinaryenLiteralInt32(10));
-  RelooperAddBranch(relooperBlocks[0], relooperBlocks[1], expressions[79], expressions[0]);
+  expressions[115] = BinaryenConst(the_module, BinaryenLiteralInt32(0));
+  {
+    BinaryenExpressionRef operands[] = { expressions[115] };
+    expressions[116] = BinaryenCallImport(the_module, "check", operands, 1, 0);
+  }
+  relooperBlocks[0] = RelooperAddBlock(the_relooper, expressions[116]);
+  expressions[117] = BinaryenConst(the_module, BinaryenLiteralInt32(1));
+  {
+    BinaryenExpressionRef operands[] = { expressions[117] };
+    expressions[118] = BinaryenCallImport(the_module, "check", operands, 1, 0);
+  }
+  relooperBlocks[1] = RelooperAddBlock(the_relooper, expressions[118]);
+  expressions[119] = BinaryenConst(the_module, BinaryenLiteralInt32(2));
+  {
+    BinaryenExpressionRef operands[] = { expressions[119] };
+    expressions[120] = BinaryenCallImport(the_module, "check", operands, 1, 0);
+  }
+  relooperBlocks[2] = RelooperAddBlock(the_relooper, expressions[120]);
+  expressions[121] = BinaryenConst(the_module, BinaryenLiteralInt32(10));
+  RelooperAddBranch(relooperBlocks[0], relooperBlocks[1], expressions[121], expressions[0]);
   RelooperAddBranch(relooperBlocks[0], relooperBlocks[2], expressions[0], expressions[0]);
   RelooperAddBranch(relooperBlocks[1], relooperBlocks[2], expressions[0], expressions[0]);
   RelooperAddBranch(relooperBlocks[2], relooperBlocks[1], expressions[0], expressions[0]);
-  expressions[80] = RelooperRenderAndDispose(the_relooper, relooperBlocks[0], 3, the_module);
+  expressions[122] = RelooperRenderAndDispose(the_relooper, relooperBlocks[0], 3, the_module);
   {
     BinaryenType varTypes[] = { 1, 1, 2, 1, 3, 4, 1 };
-    functions[13] = BinaryenAddFunction(the_module, "duffs-device", functionTypes[0], varTypes, 7, expressions[80]);
+    functions[13] = BinaryenAddFunction(the_module, "duffs-device", functionTypes[0], varTypes, 7, expressions[122]);
   }
   {
     BinaryenIndex paramTypes[] = { 0 };
-    functionTypes[1] = BinaryenAddFunctionType(the_module, "i", 1, paramTypes, 0);
+    functionTypes[2] = BinaryenAddFunctionType(the_module, "i", 1, paramTypes, 0);
   }
   the_relooper = RelooperCreate();
-  expressions[81] = BinaryenConst(the_module, BinaryenLiteralInt32(42));
-  expressions[82] = BinaryenConst(the_module, BinaryenLiteralInt32(1337));
-  expressions[83] = BinaryenReturn(the_module, expressions[82]);
+  expressions[123] = BinaryenConst(the_module, BinaryenLiteralInt32(42));
   {
-    BinaryenExpressionRef children[] = { expressions[81], expressions[83] };
-    expressions[84] = BinaryenBlock(the_module, "the-list", children, 2);
+    BinaryenExpressionRef operands[] = { expressions[123] };
+    expressions[124] = BinaryenCallImport(the_module, "check", operands, 1, 0);
   }
-  relooperBlocks[0] = RelooperAddBlock(the_relooper, expressions[84]);
-  expressions[85] = RelooperRenderAndDispose(the_relooper, relooperBlocks[0], 0, the_module);
+  expressions[125] = BinaryenConst(the_module, BinaryenLiteralInt32(1337));
+  expressions[126] = BinaryenReturn(the_module, expressions[125]);
+  {
+    BinaryenExpressionRef children[] = { expressions[124], expressions[126] };
+    expressions[127] = BinaryenBlock(the_module, "the-list", children, 2);
+  }
+  relooperBlocks[0] = RelooperAddBlock(the_relooper, expressions[127]);
+  expressions[128] = RelooperRenderAndDispose(the_relooper, relooperBlocks[0], 0, the_module);
   {
     BinaryenType varTypes[] = { 1 };
-    functions[14] = BinaryenAddFunction(the_module, "return", functionTypes[1], varTypes, 1, expressions[85]);
+    functions[14] = BinaryenAddFunction(the_module, "return", functionTypes[2], varTypes, 1, expressions[128]);
   }
 raw:
   BinaryenModulePrint(the_module);
 (module
   (memory 0)
   (type $v (func))
+  (type $vi (func (param i32)))
   (type $i (func (result i32)))
+  (import $check "module" "check" (param i32))
   (func $just-one-block (type $v)
     (local $0 i32)
-    (i32.const 1337)
+    (call_import $check
+      (i32.const 1337)
+    )
   )
   (func $two-blocks (type $v)
     (local $0 i32)
-    (block
-      (i32.const 0)
+    (block $block$2$break
+      (call_import $check
+        (i32.const 0)
+      )
+      (block
+        (br $block$2$break)
+      )
     )
     (block
-      (i32.const 1)
+      (call_import $check
+        (i32.const 1)
+      )
     )
   )
   (func $two-blocks-plus-code (type $v)
     (local $0 i32)
-    (block
-      (i32.const 0)
+    (block $block$2$break
+      (call_import $check
+        (i32.const 0)
+      )
       (block
         (i32.const 77)
+        (br $block$2$break)
       )
     )
     (block
-      (i32.const 1)
+      (call_import $check
+        (i32.const 1)
+      )
     )
   )
   (func $loop (type $v)
     (local $0 i32)
-    (loop $shape$0$break $shape$0$continue
-      (block
-        (i32.const 0)
+    (loop $shape$0$continue
+      (block $block$2$break
+        (call_import $check
+          (i32.const 0)
+        )
+        (block
+          (br $block$2$break)
+        )
       )
       (block
-        (i32.const 1)
+        (call_import $check
+          (i32.const 1)
+        )
         (block
           (br $shape$0$continue)
         )
@@ -1822,15 +2274,20 @@ raw:
   )
   (func $loop-plus-code (type $v)
     (local $0 i32)
-    (loop $shape$0$break $shape$0$continue
-      (block
-        (i32.const 0)
+    (loop $shape$0$continue
+      (block $block$2$break
+        (call_import $check
+          (i32.const 0)
+        )
         (block
           (i32.const 33)
+          (br $block$2$break)
         )
       )
       (block
-        (i32.const 1)
+        (call_import $check
+          (i32.const 1)
+        )
         (block
           (i32.const -66)
           (br $shape$0$continue)
@@ -1840,14 +2297,18 @@ raw:
   )
   (func $split (type $v)
     (local $0 i32)
-    (i32.const 0)
-    (block $shape$1$break
-      (if
-        (i32.const 55)
-        (block
+    (call_import $check
+      (i32.const 0)
+    )
+    (if
+      (i32.const 55)
+      (block
+        (call_import $check
           (i32.const 1)
         )
-        (block
+      )
+      (block
+        (call_import $check
           (i32.const 2)
         )
       )
@@ -1855,19 +2316,23 @@ raw:
   )
   (func $split-plus-code (type $v)
     (local $0 i32)
-    (i32.const 0)
-    (block $shape$1$break
-      (if
-        (i32.const 55)
+    (call_import $check
+      (i32.const 0)
+    )
+    (if
+      (i32.const 55)
+      (block
+        (i32.const 10)
         (block
-          (i32.const 10)
-          (block
+          (call_import $check
             (i32.const 1)
           )
         )
+      )
+      (block
+        (i32.const 20)
         (block
-          (i32.const 20)
-          (block
+          (call_import $check
             (i32.const 2)
           )
         )
@@ -1876,166 +2341,197 @@ raw:
   )
   (func $if (type $v)
     (local $0 i32)
-    (block
-      (i32.const 0)
-      (block $shape$1$break
-        (if
-          (i32.const 55)
-          (block
+    (block $block$3$break
+      (call_import $check
+        (i32.const 0)
+      )
+      (if
+        (i32.const 55)
+        (block
+          (call_import $check
             (i32.const 1)
-            (block
-              (br $shape$1$break)
-            )
+          )
+          (block
+            (br $block$3$break)
           )
         )
+        (br $block$3$break)
       )
     )
     (block
-      (i32.const 2)
+      (call_import $check
+        (i32.const 2)
+      )
     )
   )
   (func $if-plus-code (type $v)
     (local $0 i32)
-    (block
-      (i32.const 0)
-      (block $shape$1$break
-        (if
-          (i32.const 55)
+    (block $block$3$break
+      (call_import $check
+        (i32.const 0)
+      )
+      (if
+        (i32.const 55)
+        (block
+          (i32.const -1)
           (block
-            (i32.const -1)
-            (block
+            (call_import $check
               (i32.const 1)
-              (block
-                (i32.const -3)
-                (br $shape$1$break)
-              )
+            )
+            (block
+              (i32.const -3)
+              (br $block$3$break)
             )
           )
+        )
+        (block
           (i32.const -2)
+          (br $block$3$break)
         )
       )
     )
     (block
-      (i32.const 2)
+      (call_import $check
+        (i32.const 2)
+      )
     )
   )
   (func $if-else (type $v)
     (local $0 i32)
-    (block
-      (i32.const 0)
-      (block $shape$1$break
-        (if
-          (i32.const 55)
-          (block
+    (block $block$4$break
+      (call_import $check
+        (i32.const 0)
+      )
+      (if
+        (i32.const 55)
+        (block
+          (call_import $check
             (i32.const 1)
-            (block
-              (br $shape$1$break)
-            )
           )
           (block
+            (br $block$4$break)
+          )
+        )
+        (block
+          (call_import $check
             (i32.const 2)
-            (block
-              (br $shape$1$break)
-            )
+          )
+          (block
+            (br $block$4$break)
           )
         )
       )
     )
     (block
-      (i32.const 3)
+      (call_import $check
+        (i32.const 3)
+      )
     )
   )
   (func $loop-tail (type $v)
     (local $0 i32)
-    (loop $shape$0$break $shape$0$continue
-      (block
-        (i32.const 0)
-      )
-      (block
-        (i32.const 1)
-        (if
-          (i32.const 10)
-          (br $shape$0$continue)
-          (br $shape$0$break)
+    (block $block$3$break
+      (loop $shape$0$continue
+        (block $block$2$break
+          (call_import $check
+            (i32.const 0)
+          )
+          (block
+            (br $block$2$break)
+          )
+        )
+        (block
+          (call_import $check
+            (i32.const 1)
+          )
+          (if
+            (i32.const 10)
+            (br $shape$0$continue)
+            (br $block$3$break)
+          )
         )
       )
     )
     (block
-      (i32.const 2)
+      (call_import $check
+        (i32.const 2)
+      )
     )
   )
   (func $nontrivial-loop-plus-phi-to-head (type $v)
     (local $0 i32)
-    (block
-      (i32.const 0)
+    (block $block$2$break
+      (call_import $check
+        (i32.const 0)
+      )
       (block
         (i32.const 10)
+        (br $block$2$break)
       )
     )
     (block
-      (loop $shape$1$break $shape$1$continue
-        (block
-          (i32.const 1)
-          (if
-            (i32.eqz
-              (i32.const -2)
-            )
-            (block
-              (i32.const 20)
-              (br $shape$1$break)
-            )
-          )
-        )
-        (block
-          (i32.const 2)
-          (if
-            (i32.const -6)
-            (block
-              (set_local $0
-                (i32.const 4)
+      (block $block$7$break
+        (block $block$4$break
+          (loop $shape$1$continue
+            (block $block$3$break
+              (call_import $check
+                (i32.const 1)
+              )
+              (if
+                (i32.const -2)
+                (br $block$3$break)
+                (block
+                  (i32.const 20)
+                  (br $block$7$break)
+                )
               )
-              (br $shape$1$break)
             )
             (block
-              (i32.const 30)
-              (br $shape$1$continue)
+              (call_import $check
+                (i32.const 2)
+              )
+              (if
+                (i32.const -6)
+                (br $block$4$break)
+                (block
+                  (i32.const 30)
+                  (br $shape$1$continue)
+                )
+              )
             )
           )
         )
-      )
-      (block
-        (block $shape$4$break
-          (if
-            (i32.eq
-              (get_local $0)
-              (i32.const 4)
+        (block
+          (block $block$6$break
+            (call_import $check
+              (i32.const 3)
             )
-            (block
+            (if
+              (i32.const -10)
               (block
-                (i32.const 3)
-                (block $shape$6$break
-                  (if
-                    (i32.const -10)
-                    (block
-                      (i32.const 4)
-                      (block
-                        (br $shape$6$break)
-                      )
-                    )
-                  )
+                (call_import $check
+                  (i32.const 4)
                 )
-              )
-              (block
-                (i32.const 5)
                 (block
-                  (i32.const 40)
-                  (br $shape$4$break)
+                  (br $block$6$break)
                 )
               )
+              (br $block$6$break)
+            )
+          )
+          (block
+            (call_import $check
+              (i32.const 5)
+            )
+            (block
+              (i32.const 40)
+              (br $block$7$break)
             )
           )
         )
-        (block
+      )
+      (block
+        (call_import $check
           (i32.const 6)
         )
       )
@@ -2043,38 +2539,44 @@ raw:
   )
   (func $switch (type $v)
     (local $0 i32)
-    (i32.const 0)
-    (block $shape$1$break
-      (block $switch$1$leave
-        (block $switch$1$default
-          (block $switch$1$case$3
-            (block $switch$1$case$2
-              (br_table $switch$1$default $switch$1$default $switch$1$case$2 $switch$1$default $switch$1$case$3 $switch$1$case$2 $switch$1$default
-                (i32.const -99)
-              )
+    (call_import $check
+      (i32.const 0)
+    )
+    (block $switch$1$leave
+      (block $switch$1$default
+        (block $switch$1$case$3
+          (block $switch$1$case$2
+            (br_table $switch$1$default $switch$1$default $switch$1$case$2 $switch$1$default $switch$1$case$3 $switch$1$case$2 $switch$1$default
+              (i32.const -99)
             )
+          )
+          (block
             (block
-              (block
+              (call_import $check
                 (i32.const 1)
               )
             )
-            (br $switch$1$leave)
           )
+          (br $switch$1$leave)
+        )
+        (block
+          (i32.const 55)
           (block
-            (i32.const 55)
-            (block
+            (call_import $check
               (i32.const 2)
             )
           )
-          (br $switch$1$leave)
         )
+        (br $switch$1$leave)
+      )
+      (block
         (block
-          (block
+          (call_import $check
             (i32.const 3)
           )
         )
-        (br $switch$1$leave)
       )
+      (br $switch$1$leave)
     )
   )
   (func $duffs-device (type $v)
@@ -2086,52 +2588,66 @@ raw:
     (local $5 f64)
     (local $6 i32)
     (block
-      (i32.const 0)
+      (block $block$3$break
+        (block $block$2$break
+          (call_import $check
+            (i32.const 0)
+          )
+          (if
+            (i32.const 10)
+            (block
+              (set_local $3
+                (i32.const 2)
+              )
+              (br $block$2$break)
+            )
+            (block
+              (set_local $3
+                (i32.const 3)
+              )
+              (br $block$3$break)
+            )
+          )
+        )
+      )
+    )
+    (loop $shape$1$continue
       (if
-        (i32.const 10)
-        (set_local $3
+        (i32.eq
+          (get_local $3)
           (i32.const 2)
         )
-        (set_local $3
-          (i32.const 3)
+        (block
+          (set_local $3
+            (i32.const 0)
+          )
+          (call_import $check
+            (i32.const 1)
+          )
+          (block
+            (set_local $3
+              (i32.const 3)
+            )
+            (br $shape$1$continue)
+          )
         )
-      )
-    )
-    (loop $shape$1$break $shape$1$continue
-      (block $shape$2$break
         (if
           (i32.eq
             (get_local $3)
-            (i32.const 2)
+            (i32.const 3)
           )
           (block
             (set_local $3
               (i32.const 0)
             )
-            (i32.const 1)
-            (block
-              (set_local $3
-                (i32.const 3)
-              )
-              (br $shape$1$continue)
-            )
-          )
-          (if
-            (i32.eq
-              (get_local $3)
-              (i32.const 3)
+            (call_import $check
+              (i32.const 2)
             )
             (block
               (set_local $3
-                (i32.const 0)
-              )
-              (i32.const 2)
-              (block
-                (set_local $3
-                  (i32.const 2)
-                )
-                (br $shape$1$continue)
+                (i32.const 2)
               )
+              (br $shape$1$continue)
             )
           )
         )
@@ -2141,7 +2657,9 @@ raw:
   (func $return (type $i) (result i32)
     (local $0 i32)
     (block $the-list
-      (i32.const 42)
+      (call_import $check
+        (i32.const 42)
+      )
       (return
         (i32.const 1337)
       )
@@ -2156,22 +2674,179 @@ optimized:
 (module
   (memory 0)
   (type $v (func))
+  (type $vi (func (param i32)))
   (type $i (func (result i32)))
+  (import $check "module" "check" (param i32))
   (func $just-one-block (type $v)
-    (nop)
+    (call_import $check
+      (i32.const 1337)
+    )
+  )
+  (func $two-blocks (type $v)
+    (call_import $check
+      (i32.const 0)
+    )
+    (call_import $check
+      (i32.const 1)
+    )
+  )
+  (func $loop (type $v)
+    (loop $shape$0$continue
+      (call_import $check
+        (i32.const 0)
+      )
+      (call_import $check
+        (i32.const 1)
+      )
+      (br $shape$0$continue)
+    )
+  )
+  (func $split (type $v)
+    (call_import $check
+      (i32.const 0)
+    )
+    (if
+      (i32.const 55)
+      (call_import $check
+        (i32.const 1)
+      )
+      (call_import $check
+        (i32.const 2)
+      )
+    )
+  )
+  (func $if (type $v)
+    (call_import $check
+      (i32.const 0)
+    )
+    (if
+      (i32.const 55)
+      (call_import $check
+        (i32.const 1)
+      )
+    )
+    (call_import $check
+      (i32.const 2)
+    )
+  )
+  (func $if-else (type $v)
+    (call_import $check
+      (i32.const 0)
+    )
+    (if
+      (i32.const 55)
+      (call_import $check
+        (i32.const 1)
+      )
+      (call_import $check
+        (i32.const 2)
+      )
+    )
+    (call_import $check
+      (i32.const 3)
+    )
+  )
+  (func $loop-tail (type $v)
+    (loop $block$3$break $shape$0$continue
+      (call_import $check
+        (i32.const 0)
+      )
+      (call_import $check
+        (i32.const 1)
+      )
+      (if
+        (i32.const 10)
+        (br $shape$0$continue)
+        (br $block$3$break)
+      )
+    )
+    (call_import $check
+      (i32.const 2)
+    )
+  )
+  (func $nontrivial-loop-plus-phi-to-head (type $v)
+    (call_import $check
+      (i32.const 0)
+    )
+    (block $block$7$break
+      (loop $block$4$break $shape$1$continue
+        (call_import $check
+          (i32.const 1)
+        )
+        (br_if $block$7$break
+          (i32.const 0)
+        )
+        (call_import $check
+          (i32.const 2)
+        )
+        (if
+          (i32.const -6)
+          (br $block$4$break)
+          (br $shape$1$continue)
+        )
+      )
+      (call_import $check
+        (i32.const 3)
+      )
+      (if
+        (i32.const -10)
+        (call_import $check
+          (i32.const 4)
+        )
+      )
+      (call_import $check
+        (i32.const 5)
+      )
+    )
+    (call_import $check
+      (i32.const 6)
+    )
+  )
+  (func $switch (type $v)
+    (call_import $check
+      (i32.const 0)
+    )
+    (block $switch$1$leave
+      (block $switch$1$default
+        (block $switch$1$case$3
+          (block $switch$1$case$2
+            (br_table $switch$1$default $switch$1$default $switch$1$case$2 $switch$1$default $switch$1$case$3 $switch$1$case$2 $switch$1$default
+              (i32.const -99)
+            )
+          )
+          (call_import $check
+            (i32.const 1)
+          )
+          (br $switch$1$leave)
+        )
+        (call_import $check
+          (i32.const 2)
+        )
+        (br $switch$1$leave)
+      )
+      (call_import $check
+        (i32.const 3)
+      )
+    )
   )
   (func $duffs-device (type $v)
     (local $0 i32)
+    (call_import $check
+      (i32.const 0)
+    )
     (set_local $0
       (i32.const 2)
     )
-    (loop $shape$1$break $shape$1$continue
+    (loop $shape$1$continue
       (if
         (i32.eq
           (get_local $0)
           (i32.const 2)
         )
         (block
+          (call_import $check
+            (i32.const 1)
+          )
           (set_local $0
             (i32.const 3)
           )
@@ -2183,6 +2858,9 @@ optimized:
             (i32.const 3)
           )
           (block
+            (call_import $check
+              (i32.const 2)
+            )
             (set_local $0
               (i32.const 2)
             )
@@ -2193,6 +2871,9 @@ optimized:
     )
   )
   (func $return (type $i) (result i32)
+    (call_import $check
+      (i32.const 42)
+    )
     (i32.const 1337)
   )
 )
diff --git a/test/example/c-api-kitchen-sink.txt.txt b/test/example/c-api-kitchen-sink.txt.txt
index a9e599bef..96cbaaa00 100644
--- a/test/example/c-api-kitchen-sink.txt.txt
+++ b/test/example/c-api-kitchen-sink.txt.txt
@@ -364,40 +364,63 @@
 (module
   (memory 0)
   (type $v (func))
+  (type $vi (func (param i32)))
   (type $i (func (result i32)))
+  (import $check "module" "check" (param i32))
   (func $just-one-block (type $v)
     (local $0 i32)
-    (i32.const 1337)
+    (call_import $check
+      (i32.const 1337)
+    )
   )
   (func $two-blocks (type $v)
     (local $0 i32)
-    (block
-      (i32.const 0)
+    (block $block$2$break
+      (call_import $check
+        (i32.const 0)
+      )
+      (block
+        (br $block$2$break)
+      )
     )
     (block
-      (i32.const 1)
+      (call_import $check
+        (i32.const 1)
+      )
     )
   )
   (func $two-blocks-plus-code (type $v)
     (local $0 i32)
-    (block
-      (i32.const 0)
+    (block $block$2$break
+      (call_import $check
+        (i32.const 0)
+      )
       (block
         (i32.const 77)
+        (br $block$2$break)
       )
     )
     (block
-      (i32.const 1)
+      (call_import $check
+        (i32.const 1)
+      )
     )
   )
   (func $loop (type $v)
     (local $0 i32)
-    (loop $shape$0$break $shape$0$continue
-      (block
-        (i32.const 0)
+    (loop $shape$0$continue
+      (block $block$2$break
+        (call_import $check
+          (i32.const 0)
+        )
+        (block
+          (br $block$2$break)
+        )
       )
       (block
-        (i32.const 1)
+        (call_import $check
+          (i32.const 1)
+        )
         (block
           (br $shape$0$continue)
         )
@@ -406,15 +429,20 @@
   )
   (func $loop-plus-code (type $v)
     (local $0 i32)
-    (loop $shape$0$break $shape$0$continue
-      (block
-        (i32.const 0)
+    (loop $shape$0$continue
+      (block $block$2$break
+        (call_import $check
+          (i32.const 0)
+        )
         (block
           (i32.const 33)
+          (br $block$2$break)
         )
       )
       (block
-        (i32.const 1)
+        (call_import $check
+          (i32.const 1)
+        )
         (block
           (i32.const -66)
           (br $shape$0$continue)
@@ -424,14 +452,18 @@
   )
   (func $split (type $v)
     (local $0 i32)
-    (i32.const 0)
-    (block $shape$1$break
-      (if
-        (i32.const 55)
-        (block
+    (call_import $check
+      (i32.const 0)
+    )
+    (if
+      (i32.const 55)
+      (block
+        (call_import $check
           (i32.const 1)
         )
-        (block
+      )
+      (block
+        (call_import $check
           (i32.const 2)
         )
       )
@@ -439,19 +471,23 @@
   )
   (func $split-plus-code (type $v)
     (local $0 i32)
-    (i32.const 0)
-    (block $shape$1$break
-      (if
-        (i32.const 55)
+    (call_import $check
+      (i32.const 0)
+    )
+    (if
+      (i32.const 55)
+      (block
+        (i32.const 10)
         (block
-          (i32.const 10)
-          (block
+          (call_import $check
             (i32.const 1)
           )
         )
+      )
+      (block
+        (i32.const 20)
         (block
-          (i32.const 20)
-          (block
+          (call_import $check
             (i32.const 2)
           )
         )
@@ -460,166 +496,197 @@
   )
   (func $if (type $v)
     (local $0 i32)
-    (block
-      (i32.const 0)
-      (block $shape$1$break
-        (if
-          (i32.const 55)
-          (block
+    (block $block$3$break
+      (call_import $check
+        (i32.const 0)
+      )
+      (if
+        (i32.const 55)
+        (block
+          (call_import $check
             (i32.const 1)
-            (block
-              (br $shape$1$break)
-            )
+          )
+          (block
+            (br $block$3$break)
           )
         )
+        (br $block$3$break)
       )
     )
     (block
-      (i32.const 2)
+      (call_import $check
+        (i32.const 2)
+      )
     )
   )
   (func $if-plus-code (type $v)
     (local $0 i32)
-    (block
-      (i32.const 0)
-      (block $shape$1$break
-        (if
-          (i32.const 55)
+    (block $block$3$break
+      (call_import $check
+        (i32.const 0)
+      )
+      (if
+        (i32.const 55)
+        (block
+          (i32.const -1)
           (block
-            (i32.const -1)
-            (block
+            (call_import $check
               (i32.const 1)
-              (block
-                (i32.const -3)
-                (br $shape$1$break)
-              )
+            )
+            (block
+              (i32.const -3)
+              (br $block$3$break)
             )
           )
+        )
+        (block
           (i32.const -2)
+          (br $block$3$break)
         )
       )
     )
     (block
-      (i32.const 2)
+      (call_import $check
+        (i32.const 2)
+      )
     )
   )
   (func $if-else (type $v)
     (local $0 i32)
-    (block
-      (i32.const 0)
-      (block $shape$1$break
-        (if
-          (i32.const 55)
-          (block
+    (block $block$4$break
+      (call_import $check
+        (i32.const 0)
+      )
+      (if
+        (i32.const 55)
+        (block
+          (call_import $check
             (i32.const 1)
-            (block
-              (br $shape$1$break)
-            )
           )
           (block
+            (br $block$4$break)
+          )
+        )
+        (block
+          (call_import $check
             (i32.const 2)
-            (block
-              (br $shape$1$break)
-            )
+          )
+          (block
+            (br $block$4$break)
           )
         )
       )
     )
     (block
-      (i32.const 3)
+      (call_import $check
+        (i32.const 3)
+      )
     )
   )
   (func $loop-tail (type $v)
     (local $0 i32)
-    (loop $shape$0$break $shape$0$continue
-      (block
-        (i32.const 0)
-      )
-      (block
-        (i32.const 1)
-        (if
-          (i32.const 10)
-          (br $shape$0$continue)
-          (br $shape$0$break)
+    (block $block$3$break
+      (loop $shape$0$continue
+        (block $block$2$break
+          (call_import $check
+            (i32.const 0)
+          )
+          (block
+            (br $block$2$break)
+          )
+        )
+        (block
+          (call_import $check
+            (i32.const 1)
+          )
+          (if
+            (i32.const 10)
+            (br $shape$0$continue)
+            (br $block$3$break)
+          )
         )
       )
     )
     (block
-      (i32.const 2)
+      (call_import $check
+        (i32.const 2)
+      )
     )
   )
   (func $nontrivial-loop-plus-phi-to-head (type $v)
     (local $0 i32)
-    (block
-      (i32.const 0)
+    (block $block$2$break
+      (call_import $check
+        (i32.const 0)
+      )
       (block
         (i32.const 10)
+        (br $block$2$break)
       )
     )
     (block
-      (loop $shape$1$break $shape$1$continue
-        (block
-          (i32.const 1)
-          (if
-            (i32.eqz
-              (i32.const -2)
-            )
-            (block
-              (i32.const 20)
-              (br $shape$1$break)
-            )
-          )
-        )
-        (block
-          (i32.const 2)
-          (if
-            (i32.const -6)
-            (block
-              (set_local $0
-                (i32.const 4)
+      (block $block$7$break
+        (block $block$4$break
+          (loop $shape$1$continue
+            (block $block$3$break
+              (call_import $check
+                (i32.const 1)
+              )
+              (if
+                (i32.const -2)
+                (br $block$3$break)
+                (block
+                  (i32.const 20)
+                  (br $block$7$break)
+                )
               )
-              (br $shape$1$break)
             )
             (block
-              (i32.const 30)
-              (br $shape$1$continue)
+              (call_import $check
+                (i32.const 2)
+              )
+              (if
+                (i32.const -6)
+                (br $block$4$break)
+                (block
+                  (i32.const 30)
+                  (br $shape$1$continue)
+                )
+              )
             )
           )
         )
-      )
-      (block
-        (block $shape$4$break
-          (if
-            (i32.eq
-              (get_local $0)
-              (i32.const 4)
+        (block
+          (block $block$6$break
+            (call_import $check
+              (i32.const 3)
             )
-            (block
+            (if
+              (i32.const -10)
               (block
-                (i32.const 3)
-                (block $shape$6$break
-                  (if
-                    (i32.const -10)
-                    (block
-                      (i32.const 4)
-                      (block
-                        (br $shape$6$break)
-                      )
-                    )
-                  )
+                (call_import $check
+                  (i32.const 4)
                 )
-              )
-              (block
-                (i32.const 5)
                 (block
-                  (i32.const 40)
-                  (br $shape$4$break)
+                  (br $block$6$break)
                 )
               )
+              (br $block$6$break)
+            )
+          )
+          (block
+            (call_import $check
+              (i32.const 5)
+            )
+            (block
+              (i32.const 40)
+              (br $block$7$break)
             )
           )
         )
-        (block
+      )
+      (block
+        (call_import $check
           (i32.const 6)
         )
       )
@@ -627,38 +694,44 @@
   )
   (func $switch (type $v)
     (local $0 i32)
-    (i32.const 0)
-    (block $shape$1$break
-      (block $switch$1$leave
-        (block $switch$1$default
-          (block $switch$1$case$3
-            (block $switch$1$case$2
-              (br_table $switch$1$default $switch$1$default $switch$1$case$2 $switch$1$default $switch$1$case$3 $switch$1$case$2 $switch$1$default
-                (i32.const -99)
-              )
+    (call_import $check
+      (i32.const 0)
+    )
+    (block $switch$1$leave
+      (block $switch$1$default
+        (block $switch$1$case$3
+          (block $switch$1$case$2
+            (br_table $switch$1$default $switch$1$default $switch$1$case$2 $switch$1$default $switch$1$case$3 $switch$1$case$2 $switch$1$default
+              (i32.const -99)
             )
+          )
+          (block
             (block
-              (block
+              (call_import $check
                 (i32.const 1)
               )
             )
-            (br $switch$1$leave)
           )
+          (br $switch$1$leave)
+        )
+        (block
+          (i32.const 55)
           (block
-            (i32.const 55)
-            (block
+            (call_import $check
               (i32.const 2)
             )
           )
-          (br $switch$1$leave)
         )
+        (br $switch$1$leave)
+      )
+      (block
         (block
-          (block
+          (call_import $check
             (i32.const 3)
           )
         )
-        (br $switch$1$leave)
       )
+      (br $switch$1$leave)
     )
   )
   (func $duffs-device (type $v)
@@ -670,52 +743,66 @@
     (local $5 f64)
     (local $6 i32)
     (block
-      (i32.const 0)
+      (block $block$3$break
+        (block $block$2$break
+          (call_import $check
+            (i32.const 0)
+          )
+          (if
+            (i32.const 10)
+            (block
+              (set_local $3
+                (i32.const 2)
+              )
+              (br $block$2$break)
+            )
+            (block
+              (set_local $3
+                (i32.const 3)
+              )
+              (br $block$3$break)
+            )
+          )
+        )
+      )
+    )
+    (loop $shape$1$continue
       (if
-        (i32.const 10)
-        (set_local $3
+        (i32.eq
+          (get_local $3)
           (i32.const 2)
         )
-        (set_local $3
-          (i32.const 3)
+        (block
+          (set_local $3
+            (i32.const 0)
+          )
+          (call_import $check
+            (i32.const 1)
+          )
+          (block
+            (set_local $3
+              (i32.const 3)
+            )
+            (br $shape$1$continue)
+          )
         )
-      )
-    )
-    (loop $shape$1$break $shape$1$continue
-      (block $shape$2$break
         (if
           (i32.eq
             (get_local $3)
-            (i32.const 2)
+            (i32.const 3)
           )
           (block
             (set_local $3
               (i32.const 0)
             )
-            (i32.const 1)
-            (block
-              (set_local $3
-                (i32.const 3)
-              )
-              (br $shape$1$continue)
-            )
-          )
-          (if
-            (i32.eq
-              (get_local $3)
-              (i32.const 3)
+            (call_import $check
+              (i32.const 2)
             )
             (block
               (set_local $3
-                (i32.const 0)
-              )
-              (i32.const 2)
-              (block
-                (set_local $3
-                  (i32.const 2)
-                )
-                (br $shape$1$continue)
+                (i32.const 2)
               )
+              (br $shape$1$continue)
             )
           )
         )
@@ -725,7 +812,9 @@
   (func $return (type $i) (result i32)
     (local $0 i32)
     (block $the-list
-      (i32.const 42)
+      (call_import $check
+        (i32.const 42)
+      )
       (return
         (i32.const 1337)
       )
@@ -735,22 +824,179 @@
 (module
   (memory 0)
   (type $v (func))
+  (type $vi (func (param i32)))
   (type $i (func (result i32)))
+  (import $check "module" "check" (param i32))
   (func $just-one-block (type $v)
-    (nop)
+    (call_import $check
+      (i32.const 1337)
+    )
+  )
+  (func $two-blocks (type $v)
+    (call_import $check
+      (i32.const 0)
+    )
+    (call_import $check
+      (i32.const 1)
+    )
+  )
+  (func $loop (type $v)
+    (loop $shape$0$continue
+      (call_import $check
+        (i32.const 0)
+      )
+      (call_import $check
+        (i32.const 1)
+      )
+      (br $shape$0$continue)
+    )
+  )
+  (func $split (type $v)
+    (call_import $check
+      (i32.const 0)
+    )
+    (if
+      (i32.const 55)
+      (call_import $check
+        (i32.const 1)
+      )
+      (call_import $check
+        (i32.const 2)
+      )
+    )
+  )
+  (func $if (type $v)
+    (call_import $check
+      (i32.const 0)
+    )
+    (if
+      (i32.const 55)
+      (call_import $check
+        (i32.const 1)
+      )
+    )
+    (call_import $check
+      (i32.const 2)
+    )
+  )
+  (func $if-else (type $v)
+    (call_import $check
+      (i32.const 0)
+    )
+    (if
+      (i32.const 55)
+      (call_import $check
+        (i32.const 1)
+      )
+      (call_import $check
+        (i32.const 2)
+      )
+    )
+    (call_import $check
+      (i32.const 3)
+    )
+  )
+  (func $loop-tail (type $v)
+    (loop $block$3$break $shape$0$continue
+      (call_import $check
+        (i32.const 0)
+      )
+      (call_import $check
+        (i32.const 1)
+      )
+      (if
+        (i32.const 10)
+        (br $shape$0$continue)
+        (br $block$3$break)
+      )
+    )
+    (call_import $check
+      (i32.const 2)
+    )
+  )
+  (func $nontrivial-loop-plus-phi-to-head (type $v)
+    (call_import $check
+      (i32.const 0)
+    )
+    (block $block$7$break
+      (loop $block$4$break $shape$1$continue
+        (call_import $check
+          (i32.const 1)
+        )
+        (br_if $block$7$break
+          (i32.const 0)
+        )
+        (call_import $check
+          (i32.const 2)
+        )
+        (if
+          (i32.const -6)
+          (br $block$4$break)
+          (br $shape$1$continue)
+        )
+      )
+      (call_import $check
+        (i32.const 3)
+      )
+      (if
+        (i32.const -10)
+        (call_import $check
+          (i32.const 4)
+        )
+      )
+      (call_import $check
+        (i32.const 5)
+      )
+    )
+    (call_import $check
+      (i32.const 6)
+    )
+  )
+  (func $switch (type $v)
+    (call_import $check
+      (i32.const 0)
+    )
+    (block $switch$1$leave
+      (block $switch$1$default
+        (block $switch$1$case$3
+          (block $switch$1$case$2
+            (br_table $switch$1$default $switch$1$default $switch$1$case$2 $switch$1$default $switch$1$case$3 $switch$1$case$2 $switch$1$default
+              (i32.const -99)
+            )
+          )
+          (call_import $check
+            (i32.const 1)
+          )
+          (br $switch$1$leave)
+        )
+        (call_import $check
+          (i32.const 2)
+        )
+        (br $switch$1$leave)
+      )
+      (call_import $check
+        (i32.const 3)
+      )
+    )
   )
   (func $duffs-device (type $v)
     (local $0 i32)
+    (call_import $check
+      (i32.const 0)
+    )
     (set_local $0
       (i32.const 2)
     )
-    (loop $shape$1$break $shape$1$continue
+    (loop $shape$1$continue
       (if
         (i32.eq
           (get_local $0)
           (i32.const 2)
         )
         (block
+          (call_import $check
+            (i32.const 1)
+          )
           (set_local $0
             (i32.const 3)
           )
@@ -762,6 +1008,9 @@
             (i32.const 3)
           )
           (block
+            (call_import $check
+              (i32.const 2)
+            )
             (set_local $0
               (i32.const 2)
             )
@@ -772,6 +1021,9 @@
     )
   )
   (func $return (type $i) (result i32)
+    (call_import $check
+      (i32.const 42)
+    )
     (i32.const 1337)
   )
 )
diff --git a/test/example/relooper-fuzz.c b/test/example/relooper-fuzz.c
index ecb204347..65d00aa5d 100644
--- a/test/example/relooper-fuzz.c
+++ b/test/example/relooper-fuzz.c
@@ -256,12 +256,14 @@ int main() {
   // memory
   BinaryenSetMemory(module, 1, 1, "mem", NULL, NULL, NULL, 0);
 
+  assert(BinaryenModuleValidate(module));
+
+  BinaryenModulePrint(module);
+
   BinaryenModuleOptimize(module);
 
   assert(BinaryenModuleValidate(module));
 
-  // write it out
-
   BinaryenModulePrint(module);
 
   BinaryenModuleDispose(module);
diff --git a/test/example/relooper-fuzz.txt b/test/example/relooper-fuzz.txt
index 6a45dbe84..b4e6c8b57 100644
--- a/test/example/relooper-fuzz.txt
+++ b/test/example/relooper-fuzz.txt
@@ -152,6 +152,299 @@
       (i32.const 112)
       (i32.const 34)
     )
+    (block
+      (block
+        (block $block$6$break
+          (block $block$5$break
+            (block
+              (call_import $print
+                (i32.const 0)
+              )
+              (set_local $0
+                (call $check)
+              )
+            )
+            (if
+              (i32.eq
+                (i32.rem_u
+                  (get_local $0)
+                  (i32.const 2)
+                )
+                (i32.const 0)
+              )
+              (block
+                (set_local $1
+                  (i32.const 6)
+                )
+                (br $block$6$break)
+              )
+              (block
+                (block
+                  (call_import $print
+                    (i32.const 8)
+                  )
+                  (set_local $0
+                    (call $check)
+                  )
+                )
+                (block
+                  (br $block$5$break)
+                )
+              )
+            )
+          )
+        )
+      )
+      (loop $shape$3$continue
+        (block $block$5$break
+          (if
+            (i32.eq
+              (get_local $1)
+              (i32.const 6)
+            )
+            (block
+              (set_local $1
+                (i32.const 0)
+              )
+              (block
+                (call_import $print
+                  (i32.const 5)
+                )
+                (set_local $0
+                  (call $check)
+                )
+              )
+              (if
+                (i32.eq
+                  (i32.rem_u
+                    (get_local $0)
+                    (i32.const 2)
+                  )
+                  (i32.const 0)
+                )
+                (br $shape$3$continue)
+                (block
+                  (set_local $1
+                    (i32.const 6)
+                  )
+                  (br $shape$3$continue)
+                )
+              )
+            )
+          )
+        )
+        (block
+          (block $block$3$break
+            (block
+              (call_import $print
+                (i32.const 4)
+              )
+              (set_local $0
+                (call $check)
+              )
+            )
+            (if
+              (i32.eq
+                (i32.rem_u
+                  (get_local $0)
+                  (i32.const 3)
+                )
+                (i32.const 0)
+              )
+              (br $shape$3$continue)
+              (if
+                (i32.eq
+                  (i32.rem_u
+                    (get_local $0)
+                    (i32.const 3)
+                  )
+                  (i32.const 1)
+                )
+                (block
+                  (set_local $1
+                    (i32.const 6)
+                  )
+                  (br $shape$3$continue)
+                )
+                (br $block$3$break)
+              )
+            )
+          )
+          (block
+            (block
+              (call_import $print
+                (i32.const 2)
+              )
+              (set_local $0
+                (call $check)
+              )
+            )
+            (block
+              (set_local $1
+                (i32.const 6)
+              )
+              (br $shape$3$continue)
+            )
+          )
+        )
+      )
+    )
+  )
+)
+(module
+  (memory 1 1)
+  (export "mem" memory)
+  (start $main)
+  (type $i (func (result i32)))
+  (type $v (func))
+  (type $vi (func (param i32)))
+  (import $print "spectest" "print" (param i32))
+  (func $check (type $i) (result i32)
+    (if
+      (i32.eq
+        (i32.load
+          (i32.const 4)
+        )
+        (i32.const 108)
+      )
+      (unreachable)
+    )
+    (i32.store
+      (i32.const 4)
+      (i32.add
+        (i32.load
+          (i32.const 4)
+        )
+        (i32.const 4)
+      )
+    )
+    (call_import $print
+      (i32.sub
+        (i32.const 0)
+        (i32.load offset=4
+          (i32.load
+            (i32.const 4)
+          )
+        )
+      )
+    )
+    (i32.load offset=4
+      (i32.load
+        (i32.const 4)
+      )
+    )
+  )
+  (func $main (type $v)
+    (local $0 i32)
+    (local $1 i32)
+    (i32.store
+      (i32.const 8)
+      (i32.const 89)
+    )
+    (i32.store
+      (i32.const 12)
+      (i32.const 12)
+    )
+    (i32.store
+      (i32.const 16)
+      (i32.const 78)
+    )
+    (i32.store
+      (i32.const 20)
+      (i32.const 149)
+    )
+    (i32.store
+      (i32.const 24)
+      (i32.const 118)
+    )
+    (i32.store
+      (i32.const 28)
+      (i32.const 179)
+    )
+    (i32.store
+      (i32.const 32)
+      (i32.const 127)
+    )
+    (i32.store
+      (i32.const 36)
+      (i32.const 80)
+    )
+    (i32.store
+      (i32.const 40)
+      (i32.const 21)
+    )
+    (i32.store
+      (i32.const 44)
+      (i32.const 34)
+    )
+    (i32.store
+      (i32.const 48)
+      (i32.const 119)
+    )
+    (i32.store
+      (i32.const 52)
+      (i32.const 98)
+    )
+    (i32.store
+      (i32.const 56)
+      (i32.const 38)
+    )
+    (i32.store
+      (i32.const 60)
+      (i32.const 29)
+    )
+    (i32.store
+      (i32.const 64)
+      (i32.const 36)
+    )
+    (i32.store
+      (i32.const 68)
+      (i32.const 147)
+    )
+    (i32.store
+      (i32.const 72)
+      (i32.const 13)
+    )
+    (i32.store
+      (i32.const 76)
+      (i32.const 55)
+    )
+    (i32.store
+      (i32.const 80)
+      (i32.const 166)
+    )
+    (i32.store
+      (i32.const 84)
+      (i32.const 16)
+    )
+    (i32.store
+      (i32.const 88)
+      (i32.const 143)
+    )
+    (i32.store
+      (i32.const 92)
+      (i32.const 52)
+    )
+    (i32.store
+      (i32.const 96)
+      (i32.const 130)
+    )
+    (i32.store
+      (i32.const 100)
+      (i32.const 150)
+    )
+    (i32.store
+      (i32.const 104)
+      (i32.const 176)
+    )
+    (i32.store
+      (i32.const 108)
+      (i32.const 91)
+    )
+    (i32.store
+      (i32.const 112)
+      (i32.const 34)
+    )
     (call_import $print
       (i32.const 0)
     )
@@ -173,7 +466,7 @@
         (call $check)
       )
     )
-    (loop $shape$3$break $shape$3$continue
+    (loop $shape$3$continue
       (if
         (i32.eq
           (get_local $0)
diff --git a/test/example/relooper-fuzz1.c b/test/example/relooper-fuzz1.c
new file mode 100644
index 000000000..fbbbfdd59
--- /dev/null
+++ b/test/example/relooper-fuzz1.c
@@ -0,0 +1,332 @@
+
+
+#include <assert.h>
+#include <stdio.h>
+
+#include "binaryen-c.h"
+
+// globals: address 4 is index
+// decisions are at address 8+
+
+int main() {
+  BinaryenModuleRef module = BinaryenModuleCreate();
+
+  // check()
+
+  // if the end, halt
+  BinaryenExpressionRef halter = BinaryenIf(module,
+    BinaryenBinary(module,
+      BinaryenEqInt32(),
+      BinaryenLoad(module, 4, 0, 0, 0, BinaryenInt32(),
+                   BinaryenConst(module, BinaryenLiteralInt32(4))),
+      BinaryenConst(module, BinaryenLiteralInt32(4 * 30)) // jumps of 4 bytes
+    ),
+    BinaryenUnreachable(module),
+    NULL
+  );
+  // increment index
+  BinaryenExpressionRef incer = BinaryenStore(module,
+    4, 0, 0,
+    BinaryenConst(module, BinaryenLiteralInt32(4)),
+    BinaryenBinary(module,
+      BinaryenAddInt32(),
+      BinaryenLoad(module, 4, 0, 0, 0, BinaryenInt32(),
+                   BinaryenConst(module, BinaryenLiteralInt32(4))),
+      BinaryenConst(module, BinaryenLiteralInt32(4))
+    )
+  );
+
+  // optionally, print the return value
+  BinaryenExpressionRef args[] = {
+    BinaryenBinary(module,
+      BinaryenSubInt32(),
+      BinaryenConst(module, BinaryenLiteralInt32(0)),
+      BinaryenLoad(module,
+        4, 0, 4, 0, BinaryenInt32(),
+        BinaryenLoad(module, 4, 0, 0, 0, BinaryenInt32(),
+                     BinaryenConst(module, BinaryenLiteralInt32(4)))
+      )
+    )
+  };
+  BinaryenExpressionRef debugger;
+  if (1) debugger = BinaryenCallImport(module, "print", args, 1,
+                                       BinaryenNone());
+  else debugger = BinaryenNop(module);
+
+  // return the decision. need to subtract 4 that we just added,
+  // and add 8 since that's where we start, so overall offset 4
+  BinaryenExpressionRef returner = BinaryenLoad(module,
+    4, 0, 4, 0, BinaryenInt32(),
+    BinaryenLoad(module, 4, 0, 0, 0, BinaryenInt32(),
+    BinaryenConst(module, BinaryenLiteralInt32(4)))
+  );
+  BinaryenExpressionRef checkBodyList[] = { halter, incer, debugger,
+                                            returner };
+  BinaryenExpressionRef checkBody = BinaryenBlock(module,
+    NULL, checkBodyList, sizeof(checkBodyList) / sizeof(BinaryenExpressionRef)
+  );
+  BinaryenFunctionTypeRef i = BinaryenAddFunctionType(module, "i",
+                                                      BinaryenInt32(),
+                                                      NULL, 0);
+  BinaryenAddFunction(module, "check", i, NULL, 0, checkBody);
+
+  // contents of main() begin here
+
+  RelooperRef relooper = RelooperCreate();
+
+
+  RelooperBlockRef b0;
+  {
+    BinaryenExpressionRef args[] = {
+      BinaryenConst(module, BinaryenLiteralInt32(0))
+    };
+    BinaryenExpressionRef list[] = {
+      BinaryenCallImport(module, "print", args, 1, BinaryenNone()),
+      BinaryenSetLocal(module, 0, BinaryenCall(module, "check", NULL, 0,
+                                               BinaryenInt32()))
+    };
+
+    b0 = RelooperAddBlock(relooper, BinaryenBlock(module, NULL, list, 2));
+
+  }
+
+  RelooperBlockRef b1;
+  {
+    BinaryenExpressionRef args[] = {
+      BinaryenConst(module, BinaryenLiteralInt32(1))
+    };
+    BinaryenExpressionRef list[] = {
+      BinaryenCallImport(module, "print", args, 1, BinaryenNone()),
+      BinaryenSetLocal(module, 0, BinaryenCall(module, "check", NULL, 0,
+                                               BinaryenInt32()))
+    };
+
+    b1 = RelooperAddBlock(relooper, BinaryenBlock(module, NULL, list, 2));
+
+  }
+
+  RelooperBlockRef b2;
+  {
+    BinaryenExpressionRef args[] = {
+      BinaryenConst(module, BinaryenLiteralInt32(2))
+    };
+    BinaryenExpressionRef list[] = {
+      BinaryenCallImport(module, "print", args, 1, BinaryenNone()),
+      BinaryenSetLocal(module, 0, BinaryenCall(module, "check", NULL, 0,
+                                               BinaryenInt32()))
+    };
+
+    b2 = RelooperAddBlock(relooper, BinaryenBlock(module, NULL, list, 2));
+
+  }
+
+  RelooperBlockRef b3;
+  {
+    BinaryenExpressionRef args[] = {
+      BinaryenConst(module, BinaryenLiteralInt32(3))
+    };
+    BinaryenExpressionRef list[] = {
+      BinaryenCallImport(module, "print", args, 1, BinaryenNone()),
+      BinaryenSetLocal(module, 0, BinaryenCall(module, "check", NULL, 0,
+                                               BinaryenInt32()))
+    };
+
+    b3 = RelooperAddBlock(relooper, BinaryenBlock(module, NULL, list, 2));
+
+  }
+
+  RelooperBlockRef b4;
+  {
+    BinaryenExpressionRef args[] = {
+      BinaryenConst(module, BinaryenLiteralInt32(4))
+    };
+    BinaryenExpressionRef list[] = {
+      BinaryenCallImport(module, "print", args, 1, BinaryenNone()),
+      BinaryenSetLocal(module, 0, BinaryenCall(module, "check", NULL, 0,
+                                               BinaryenInt32()))
+    };
+
+    b4 = RelooperAddBlock(relooper, BinaryenBlock(module, NULL, list, 2));
+
+  }
+
+  RelooperBlockRef b5;
+  {
+    BinaryenExpressionRef args[] = {
+      BinaryenConst(module, BinaryenLiteralInt32(5))
+    };
+    BinaryenExpressionRef list[] = {
+      BinaryenCallImport(module, "print", args, 1, BinaryenNone()),
+      BinaryenSetLocal(module, 0, BinaryenCall(module, "check", NULL, 0,
+                                               BinaryenInt32()))
+    };
+
+    b5 = RelooperAddBlock(relooper, BinaryenBlock(module, NULL, list, 2));
+
+  }
+
+  RelooperBlockRef b6;
+  {
+    BinaryenExpressionRef args[] = {
+      BinaryenConst(module, BinaryenLiteralInt32(6))
+    };
+    BinaryenExpressionRef list[] = {
+      BinaryenCallImport(module, "print", args, 1, BinaryenNone()),
+      BinaryenSetLocal(module, 0, BinaryenCall(module, "check", NULL, 0,
+                                               BinaryenInt32()))
+    };
+
+    b6 = RelooperAddBlock(relooper, BinaryenBlock(module, NULL, list, 2));
+
+  }
+
+  RelooperBlockRef b7;
+  {
+    BinaryenExpressionRef args[] = {
+      BinaryenConst(module, BinaryenLiteralInt32(7))
+    };
+    BinaryenExpressionRef list[] = {
+      BinaryenCallImport(module, "print", args, 1, BinaryenNone()),
+      BinaryenSetLocal(module, 0, BinaryenCall(module, "check", NULL, 0,
+                                               BinaryenInt32()))
+    };
+
+    b7 = RelooperAddBlock(relooper, BinaryenBlock(module, NULL, list, 2));
+
+  }
+
+  RelooperBlockRef b8;
+  {
+    BinaryenExpressionRef args[] = {
+      BinaryenConst(module, BinaryenLiteralInt32(8))
+    };
+    BinaryenExpressionRef list[] = {
+      BinaryenCallImport(module, "print", args, 1, BinaryenNone()),
+      BinaryenSetLocal(module, 0, BinaryenCall(module, "check", NULL, 0,
+                                               BinaryenInt32()))
+    };
+
+    b8 = RelooperAddBlock(relooper, BinaryenBlock(module, NULL, list, 2));
+
+  }
+
+  RelooperBlockRef b9;
+  {
+    BinaryenExpressionRef args[] = {
+      BinaryenConst(module, BinaryenLiteralInt32(9))
+    };
+    BinaryenExpressionRef list[] = {
+      BinaryenCallImport(module, "print", args, 1, BinaryenNone()),
+      BinaryenSetLocal(module, 0, BinaryenCall(module, "check", NULL, 0,
+                                               BinaryenInt32()))
+    };
+
+    b9 = RelooperAddBlock(relooper, BinaryenBlock(module, NULL, list, 2));
+
+  }
+
+  RelooperAddBranch(b0, b2, BinaryenBinary(module,
+    BinaryenEqInt32(),
+    BinaryenBinary(module,
+      BinaryenRemUInt32(),
+      BinaryenGetLocal(module, 0, BinaryenInt32()),
+      BinaryenConst(module, BinaryenLiteralInt32(4))
+    ),
+    BinaryenConst(module, BinaryenLiteralInt32(0))
+  ), NULL);
+
+  RelooperAddBranch(b0, b7, BinaryenBinary(module,
+    BinaryenEqInt32(),
+    BinaryenBinary(module,
+      BinaryenRemUInt32(),
+      BinaryenGetLocal(module, 0, BinaryenInt32()),
+      BinaryenConst(module, BinaryenLiteralInt32(4))
+    ),
+    BinaryenConst(module, BinaryenLiteralInt32(2))
+  ), NULL);
+
+  RelooperAddBranch(b0, b3, NULL, NULL);
+
+  RelooperAddBranch(b2, b3, BinaryenBinary(module,
+    BinaryenEqInt32(),
+    BinaryenBinary(module,
+      BinaryenRemUInt32(),
+      BinaryenGetLocal(module, 0, BinaryenInt32()),
+      BinaryenConst(module, BinaryenLiteralInt32(2))
+    ),
+    BinaryenConst(module, BinaryenLiteralInt32(0))
+  ), NULL);
+
+  RelooperAddBranch(b2, b9, NULL, NULL);
+
+  RelooperAddBranch(b3, b3, NULL, NULL);
+
+  RelooperAddBranch(b7, b2, BinaryenBinary(module,
+    BinaryenEqInt32(),
+    BinaryenBinary(module,
+      BinaryenRemUInt32(),
+      BinaryenGetLocal(module, 0, BinaryenInt32()),
+      BinaryenConst(module, BinaryenLiteralInt32(3))
+    ),
+    BinaryenConst(module, BinaryenLiteralInt32(0))
+  ), NULL);
+
+  RelooperAddBranch(b7, b9, NULL, NULL);
+
+  BinaryenExpressionRef body = RelooperRenderAndDispose(relooper, b0, 1,
+                                                        module);
+
+  int decisions[] = { 67, 131, 49, 36, 112, 161, 62, 166, 16, 88, 176, 152, 161, 194, 117, 180, 60, 166, 55, 183, 150, 73, 196, 143, 76, 182, 97, 140, 126, 3 };
+  int numDecisions = sizeof(decisions)/sizeof(int);
+
+  // write out all the decisions, then the body of the function
+  BinaryenExpressionRef full[numDecisions + 1];
+
+  {
+    int i;
+    for (i = 0; i < numDecisions; i++) {
+      full[i] = BinaryenStore(module,
+        4, 0, 0,
+        BinaryenConst(module, BinaryenLiteralInt32(8 + 4 * i)),
+        BinaryenConst(module, BinaryenLiteralInt32(decisions[i]))
+      );
+    }
+  }
+  full[numDecisions] = body;
+  BinaryenExpressionRef all = BinaryenBlock(module, NULL, full,
+                                            numDecisions + 1);
+
+  BinaryenFunctionTypeRef v = BinaryenAddFunctionType(module, "v",
+                                                      BinaryenNone(),
+                                                      NULL, 0);
+  // locals: state, free-for-label
+  BinaryenType localTypes[] = { BinaryenInt32(), BinaryenInt32() };
+  BinaryenFunctionRef theMain = BinaryenAddFunction(module, "main", v,
+                                                    localTypes, 2, all);
+  BinaryenSetStart(module, theMain);
+
+  // import
+
+  BinaryenType iparams[] = { BinaryenInt32() };
+  BinaryenFunctionTypeRef vi = BinaryenAddFunctionType(module, "vi",
+                                                       BinaryenNone(),
+                                                       iparams, 1);
+  BinaryenAddImport(module, "print", "spectest", "print", vi);
+
+  // memory
+  BinaryenSetMemory(module, 1, 1, "mem", NULL, NULL, NULL, 0);
+
+  assert(BinaryenModuleValidate(module));
+
+  BinaryenModulePrint(module);
+
+  BinaryenModuleOptimize(module);
+
+  assert(BinaryenModuleValidate(module));
+
+  BinaryenModulePrint(module);
+
+  BinaryenModuleDispose(module);
+
+  return 0;
+}
diff --git a/test/example/relooper-fuzz1.txt b/test/example/relooper-fuzz1.txt
new file mode 100644
index 000000000..437dab062
--- /dev/null
+++ b/test/example/relooper-fuzz1.txt
@@ -0,0 +1,501 @@
+(module
+  (memory 1 1)
+  (export "mem" memory)
+  (start $main)
+  (type $i (func (result i32)))
+  (type $v (func))
+  (type $vi (func (param i32)))
+  (import $print "spectest" "print" (param i32))
+  (func $check (type $i) (result i32)
+    (if
+      (i32.eq
+        (i32.load
+          (i32.const 4)
+        )
+        (i32.const 120)
+      )
+      (unreachable)
+    )
+    (i32.store
+      (i32.const 4)
+      (i32.add
+        (i32.load
+          (i32.const 4)
+        )
+        (i32.const 4)
+      )
+    )
+    (call_import $print
+      (i32.sub
+        (i32.const 0)
+        (i32.load offset=4
+          (i32.load
+            (i32.const 4)
+          )
+        )
+      )
+    )
+    (i32.load offset=4
+      (i32.load
+        (i32.const 4)
+      )
+    )
+  )
+  (func $main (type $v)
+    (local $0 i32)
+    (local $1 i32)
+    (i32.store
+      (i32.const 8)
+      (i32.const 67)
+    )
+    (i32.store
+      (i32.const 12)
+      (i32.const 131)
+    )
+    (i32.store
+      (i32.const 16)
+      (i32.const 49)
+    )
+    (i32.store
+      (i32.const 20)
+      (i32.const 36)
+    )
+    (i32.store
+      (i32.const 24)
+      (i32.const 112)
+    )
+    (i32.store
+      (i32.const 28)
+      (i32.const 161)
+    )
+    (i32.store
+      (i32.const 32)
+      (i32.const 62)
+    )
+    (i32.store
+      (i32.const 36)
+      (i32.const 166)
+    )
+    (i32.store
+      (i32.const 40)
+      (i32.const 16)
+    )
+    (i32.store
+      (i32.const 44)
+      (i32.const 88)
+    )
+    (i32.store
+      (i32.const 48)
+      (i32.const 176)
+    )
+    (i32.store
+      (i32.const 52)
+      (i32.const 152)
+    )
+    (i32.store
+      (i32.const 56)
+      (i32.const 161)
+    )
+    (i32.store
+      (i32.const 60)
+      (i32.const 194)
+    )
+    (i32.store
+      (i32.const 64)
+      (i32.const 117)
+    )
+    (i32.store
+      (i32.const 68)
+      (i32.const 180)
+    )
+    (i32.store
+      (i32.const 72)
+      (i32.const 60)
+    )
+    (i32.store
+      (i32.const 76)
+      (i32.const 166)
+    )
+    (i32.store
+      (i32.const 80)
+      (i32.const 55)
+    )
+    (i32.store
+      (i32.const 84)
+      (i32.const 183)
+    )
+    (i32.store
+      (i32.const 88)
+      (i32.const 150)
+    )
+    (i32.store
+      (i32.const 92)
+      (i32.const 73)
+    )
+    (i32.store
+      (i32.const 96)
+      (i32.const 196)
+    )
+    (i32.store
+      (i32.const 100)
+      (i32.const 143)
+    )
+    (i32.store
+      (i32.const 104)
+      (i32.const 76)
+    )
+    (i32.store
+      (i32.const 108)
+      (i32.const 182)
+    )
+    (i32.store
+      (i32.const 112)
+      (i32.const 97)
+    )
+    (i32.store
+      (i32.const 116)
+      (i32.const 140)
+    )
+    (i32.store
+      (i32.const 120)
+      (i32.const 126)
+    )
+    (i32.store
+      (i32.const 124)
+      (i32.const 3)
+    )
+    (block
+      (block $block$10$break
+        (block $block$4$break
+          (block $block$3$break
+            (block
+              (call_import $print
+                (i32.const 0)
+              )
+              (set_local $0
+                (call $check)
+              )
+            )
+            (if
+              (i32.eq
+                (i32.rem_u
+                  (get_local $0)
+                  (i32.const 4)
+                )
+                (i32.const 0)
+              )
+              (br $block$3$break)
+              (if
+                (i32.eq
+                  (i32.rem_u
+                    (get_local $0)
+                    (i32.const 4)
+                  )
+                  (i32.const 2)
+                )
+                (block
+                  (block
+                    (call_import $print
+                      (i32.const 7)
+                    )
+                    (set_local $0
+                      (call $check)
+                    )
+                  )
+                  (if
+                    (i32.eq
+                      (i32.rem_u
+                        (get_local $0)
+                        (i32.const 3)
+                      )
+                      (i32.const 0)
+                    )
+                    (br $block$3$break)
+                    (br $block$10$break)
+                  )
+                )
+                (br $block$4$break)
+              )
+            )
+          )
+          (block
+            (block
+              (call_import $print
+                (i32.const 2)
+              )
+              (set_local $0
+                (call $check)
+              )
+            )
+            (if
+              (i32.eq
+                (i32.rem_u
+                  (get_local $0)
+                  (i32.const 2)
+                )
+                (i32.const 0)
+              )
+              (br $block$4$break)
+              (br $block$10$break)
+            )
+          )
+        )
+        (loop $shape$6$continue
+          (block
+            (call_import $print
+              (i32.const 3)
+            )
+            (set_local $0
+              (call $check)
+            )
+          )
+          (block
+            (br $shape$6$continue)
+          )
+        )
+      )
+      (block
+        (block
+          (call_import $print
+            (i32.const 9)
+          )
+          (set_local $0
+            (call $check)
+          )
+        )
+      )
+    )
+  )
+)
+(module
+  (memory 1 1)
+  (export "mem" memory)
+  (start $main)
+  (type $i (func (result i32)))
+  (type $v (func))
+  (type $vi (func (param i32)))
+  (import $print "spectest" "print" (param i32))
+  (func $check (type $i) (result i32)
+    (if
+      (i32.eq
+        (i32.load
+          (i32.const 4)
+        )
+        (i32.const 120)
+      )
+      (unreachable)
+    )
+    (i32.store
+      (i32.const 4)
+      (i32.add
+        (i32.load
+          (i32.const 4)
+        )
+        (i32.const 4)
+      )
+    )
+    (call_import $print
+      (i32.sub
+        (i32.const 0)
+        (i32.load offset=4
+          (i32.load
+            (i32.const 4)
+          )
+        )
+      )
+    )
+    (i32.load offset=4
+      (i32.load
+        (i32.const 4)
+      )
+    )
+  )
+  (func $main (type $v)
+    (local $0 i32)
+    (i32.store
+      (i32.const 8)
+      (i32.const 67)
+    )
+    (i32.store
+      (i32.const 12)
+      (i32.const 131)
+    )
+    (i32.store
+      (i32.const 16)
+      (i32.const 49)
+    )
+    (i32.store
+      (i32.const 20)
+      (i32.const 36)
+    )
+    (i32.store
+      (i32.const 24)
+      (i32.const 112)
+    )
+    (i32.store
+      (i32.const 28)
+      (i32.const 161)
+    )
+    (i32.store
+      (i32.const 32)
+      (i32.const 62)
+    )
+    (i32.store
+      (i32.const 36)
+      (i32.const 166)
+    )
+    (i32.store
+      (i32.const 40)
+      (i32.const 16)
+    )
+    (i32.store
+      (i32.const 44)
+      (i32.const 88)
+    )
+    (i32.store
+      (i32.const 48)
+      (i32.const 176)
+    )
+    (i32.store
+      (i32.const 52)
+      (i32.const 152)
+    )
+    (i32.store
+      (i32.const 56)
+      (i32.const 161)
+    )
+    (i32.store
+      (i32.const 60)
+      (i32.const 194)
+    )
+    (i32.store
+      (i32.const 64)
+      (i32.const 117)
+    )
+    (i32.store
+      (i32.const 68)
+      (i32.const 180)
+    )
+    (i32.store
+      (i32.const 72)
+      (i32.const 60)
+    )
+    (i32.store
+      (i32.const 76)
+      (i32.const 166)
+    )
+    (i32.store
+      (i32.const 80)
+      (i32.const 55)
+    )
+    (i32.store
+      (i32.const 84)
+      (i32.const 183)
+    )
+    (i32.store
+      (i32.const 88)
+      (i32.const 150)
+    )
+    (i32.store
+      (i32.const 92)
+      (i32.const 73)
+    )
+    (i32.store
+      (i32.const 96)
+      (i32.const 196)
+    )
+    (i32.store
+      (i32.const 100)
+      (i32.const 143)
+    )
+    (i32.store
+      (i32.const 104)
+      (i32.const 76)
+    )
+    (i32.store
+      (i32.const 108)
+      (i32.const 182)
+    )
+    (i32.store
+      (i32.const 112)
+      (i32.const 97)
+    )
+    (i32.store
+      (i32.const 116)
+      (i32.const 140)
+    )
+    (i32.store
+      (i32.const 120)
+      (i32.const 126)
+    )
+    (i32.store
+      (i32.const 124)
+      (i32.const 3)
+    )
+    (block $block$10$break
+      (block $block$4$break
+        (call_import $print
+          (i32.const 0)
+        )
+        (if
+          (i32.ne
+            (i32.rem_u
+              (set_local $0
+                (call $check)
+              )
+              (i32.const 4)
+            )
+            (i32.const 0)
+          )
+          (if
+            (i32.eq
+              (i32.rem_u
+                (get_local $0)
+                (i32.const 4)
+              )
+              (i32.const 2)
+            )
+            (block
+              (call_import $print
+                (i32.const 7)
+              )
+              (br_if $block$10$break
+                (i32.ne
+                  (i32.rem_u
+                    (call $check)
+                    (i32.const 3)
+                  )
+                  (i32.const 0)
+                )
+              )
+            )
+            (br $block$4$break)
+          )
+        )
+        (call_import $print
+          (i32.const 2)
+        )
+        (br_if $block$10$break
+          (i32.ne
+            (i32.rem_u
+              (call $check)
+              (i32.const 2)
+            )
+            (i32.const 0)
+          )
+        )
+      )
+      (loop $shape$6$continue
+        (call_import $print
+          (i32.const 3)
+        )
+        (call $check)
+        (br $shape$6$continue)
+      )
+    )
+    (call_import $print
+      (i32.const 9)
+    )
+    (call $check)
+  )
+)