MergeBlocks #32

8 files changed, 634 insertions, 369 deletions

diff --git a/CMakeLists.txt b/CMakeLists.txt
index f1d575635..124a93fd0 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -34,6 +34,7 @@ SET(binaryen-shell_SOURCES
   src/binaryen-shell.cpp
   src/pass.cpp
   src/passes/LowerIfElse.cpp
+  src/passes/MergeBlocks.cpp
   src/passes/NameManager.cpp
   src/passes/RemoveImports.cpp
   src/passes/RemoveUnusedBrs.cpp
@@ -49,6 +50,7 @@ INSTALL(TARGETS binaryen-shell DESTINATION bin)
 SET(asm2wasm_SOURCES
   src/asm2wasm-main.cpp
   src/pass.cpp
+  src/passes/MergeBlocks.cpp
   src/passes/RemoveUnusedBrs.cpp
   src/passes/RemoveUnusedNames.cpp
   src/emscripten-optimizer/parser.cpp
diff --git a/build.sh b/build.sh
index 6ec6e054a..c6cee16f6 100755
--- a/build.sh
+++ b/build.sh
@@ -1,13 +1,13 @@
 ./update.py
 echo "building binaryen shell"
-g++ -O2 -std=c++11 src/binaryen-shell.cpp src/pass.cpp src/passes/LowerIfElse.cpp src/passes/NameManager.cpp src/passes/RemoveImports.cpp src/passes/RemoveUnusedNames.cpp src/support/colors.cpp -o bin/binaryen-shell -Isrc/ -msse2 -mfpmath=sse # use sse for math, avoid x87, necessarily for proper float rounding on 32-bit
+g++ -O2 -std=c++11 src/binaryen-shell.cpp src/pass.cpp src/passes/LowerIfElse.cpp src/passes/MergeBlocks.cpp src/passes/NameManager.cpp src/passes/RemoveImports.cpp src/passes/RemoveUnusedBrs.cpp src/passes/RemoveUnusedNames.cpp src/support/colors.cpp -o bin/binaryen-shell -Isrc/ -msse2 -mfpmath=sse # use sse for math, avoid x87, necessarily for proper float rounding on 32-bit
 echo "building asm2wasm"
-g++ -O2 -std=c++11 src/asm2wasm-main.cpp src/passes/RemoveUnusedBrs.cpp src/pass.cpp src/passes/RemoveUnusedNames.cpp src/emscripten-optimizer/parser.cpp src/emscripten-optimizer/simple_ast.cpp src/emscripten-optimizer/optimizer-shared.cpp src/support/colors.cpp -Isrc/ -o bin/asm2wasm
+g++ -O2 -std=c++11 src/asm2wasm-main.cpp src/passes/MergeBlocks.cpp src/passes/RemoveUnusedBrs.cpp src/pass.cpp src/passes/RemoveUnusedNames.cpp src/emscripten-optimizer/parser.cpp src/emscripten-optimizer/simple_ast.cpp src/emscripten-optimizer/optimizer-shared.cpp src/support/colors.cpp -Isrc/ -o bin/asm2wasm
 echo "building wasm2asm"
 g++ -O2 -std=c++11 src/wasm2asm-main.cpp src/emscripten-optimizer/parser.cpp src/emscripten-optimizer/simple_ast.cpp src/emscripten-optimizer/optimizer-shared.cpp src/support/colors.cpp -Isrc/ -o bin/wasm2asm
 echo "building s2wasm"
 g++ -O2 -std=c++11 src/s2wasm-main.cpp src/support/colors.cpp -Isrc/ -o bin/s2wasm
 echo "building interpreter/js"
-em++ -std=c++11 src/wasm-js.cpp src/pass.cpp src/passes/RemoveUnusedBrs.cpp src/passes/RemoveUnusedNames.cpp src/emscripten-optimizer/parser.cpp src/emscripten-optimizer/simple_ast.cpp src/emscripten-optimizer/optimizer-shared.cpp src/support/colors.cpp -Isrc/ -o bin/wasm.js -s MODULARIZE=1 -s 'EXPORT_NAME="WasmJS"' --memory-init-file 0 -Oz -s ALLOW_MEMORY_GROWTH=1 -profiling -s DEMANGLE_SUPPORT=1 #-DWASM_JS_DEBUG -DWASM_INTERPRETER_DEBUG=2
+em++ -std=c++11 src/wasm-js.cpp src/pass.cpp src/passes/MergeBlocks.cpp src/passes/RemoveUnusedBrs.cpp src/passes/RemoveUnusedNames.cpp src/emscripten-optimizer/parser.cpp src/emscripten-optimizer/simple_ast.cpp src/emscripten-optimizer/optimizer-shared.cpp src/support/colors.cpp -Isrc/ -o bin/wasm.js -s MODULARIZE=1 -s 'EXPORT_NAME="WasmJS"' --memory-init-file 0 -Oz -s ALLOW_MEMORY_GROWTH=1 -profiling -s DEMANGLE_SUPPORT=1 #-DWASM_JS_DEBUG -DWASM_INTERPRETER_DEBUG=2
 cat src/js/wasm.js-post.js >> bin/wasm.js
 
diff --git a/src/asm2wasm.h b/src/asm2wasm.h
index e91a9344e..0320b7924 100644
--- a/src/asm2wasm.h
+++ b/src/asm2wasm.h
@@ -1573,6 +1573,7 @@ void Asm2WasmBuilder::optimize() {
   PassRunner passRunner(&allocator);
   passRunner.add("remove-unused-brs");
   passRunner.add("remove-unused-names");
+  passRunner.add("merge-blocks");
   passRunner.run(&wasm);
 }
 
diff --git a/src/passes/MergeBlocks.cpp b/src/passes/MergeBlocks.cpp
new file mode 100644
index 000000000..3d7afc4cb
--- /dev/null
+++ b/src/passes/MergeBlocks.cpp
@@ -0,0 +1,56 @@
+/*
+ * Copyright 2015 WebAssembly Community Group participants
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+//
+// Merges blocks to their parents.
+//
+
+#include <wasm.h>
+#include <pass.h>
+
+namespace wasm {
+
+struct MergeBlocks : public Pass {
+  void visitBlock(Block *curr) override {
+    bool more = true;
+    while (more) {
+      more = false;
+      for (size_t i = 0; i < curr->list.size(); i++) {
+        Block* child = curr->list[i]->dyn_cast<Block>();
+        if (!child) continue;
+        if (child->name.is()) continue; // named blocks can have breaks to them (and certainly do, if we ran RemoveUnusedNames and RemoveUnusedBrs)
+        ExpressionList merged;
+        for (size_t j = 0; j < i; j++) {
+          merged.push_back(curr->list[j]);
+        }
+        for (auto item : child->list) {
+          merged.push_back(item);
+        }
+        for (size_t j = i + 1; j < curr->list.size(); j++) {
+          merged.push_back(curr->list[j]);
+        }
+        curr->list = merged;
+        more = true;
+        break;
+      }
+    }
+  }
+};
+
+static RegisterPass<MergeBlocks> registerPass("merge-blocks", "merges blocks to their parents");
+
+} // namespace wasm
+
diff --git a/test/emcc_O2_hello_world.fromasm b/test/emcc_O2_hello_world.fromasm
index 84e10d632..e056b0c05 100644
--- a/test/emcc_O2_hello_world.fromasm
+++ b/test/emcc_O2_hello_world.fromasm
@@ -3710,22 +3710,20 @@
                 (i32.const 608)
               )
             )
-            (block
-              (set_local $i50
-                (i32.add
-                  (get_local $i51)
-                  (get_local $i43)
-                )
+            (set_local $i50
+              (i32.add
+                (get_local $i51)
+                (get_local $i43)
               )
-              (i32.or
-                (i32.le_u
-                  (get_local $i50)
-                  (get_local $i51)
-                )
-                (i32.gt_u
-                  (get_local $i50)
-                  (get_local $i52)
-                )
+            )
+            (i32.or
+              (i32.le_u
+                (get_local $i50)
+                (get_local $i51)
+              )
+              (i32.gt_u
+                (get_local $i50)
+                (get_local $i52)
               )
             )
           )
@@ -4091,26 +4089,24 @@
                               (i32.const 656)
                             )
                           )
-                          (block
-                            (set_local $i5
-                              (i32.and
-                                (i32.add
-                                  (i32.sub
-                                    (get_local $i44)
-                                    (get_local $i61)
-                                  )
-                                  (get_local $i52)
-                                )
+                          (set_local $i5
+                            (i32.and
+                              (i32.add
                                 (i32.sub
-                                  (i32.const 0)
-                                  (get_local $i52)
+                                  (get_local $i44)
+                                  (get_local $i61)
                                 )
+                                (get_local $i52)
+                              )
+                              (i32.sub
+                                (i32.const 0)
+                                (get_local $i52)
                               )
                             )
-                            (i32.lt_u
-                              (get_local $i5)
-                              (i32.const 2147483647)
-                            )
+                          )
+                          (i32.lt_u
+                            (get_local $i5)
+                            (i32.const 2147483647)
                           )
                         )
                         (i32.const 0)
@@ -4202,26 +4198,24 @@
                   (get_local $i43)
                 )
               )
-              (block
-                (set_local $i43
-                  (call_import $_sbrk
-                    (i32.const 0)
-                  )
+              (set_local $i43
+                (call_import $_sbrk
+                  (i32.const 0)
+                )
+              )
+              (i32.and
+                (i32.lt_u
+                  (get_local $i63)
+                  (get_local $i43)
                 )
                 (i32.and
-                  (i32.lt_u
+                  (i32.ne
                     (get_local $i63)
-                    (get_local $i43)
+                    (i32.const -1)
                   )
-                  (i32.and
-                    (i32.ne
-                      (get_local $i63)
-                      (i32.const -1)
-                    )
-                    (i32.ne
-                      (get_local $i43)
-                      (i32.const -1)
-                    )
+                  (i32.ne
+                    (get_local $i43)
+                    (i32.const -1)
                   )
                 )
               )
@@ -10755,39 +10749,37 @@
                 (nop)
                 (br $while-out$0)
               )
-              (block
-                (if
-                  (i32.eq
-                    (get_local $i3)
-                    (i32.const 0)
-                  )
-                  (br $topmost
-                    (get_local $i4)
-                  )
+              (if
+                (i32.eq
+                  (get_local $i3)
+                  (i32.const 0)
                 )
-                (i32.store8 align=1
-                  (get_local $i1)
-                  (i32.load8_s align=1
-                    (get_local $i2)
-                  )
+                (br $topmost
+                  (get_local $i4)
                 )
-                (set_local $i1
-                  (i32.add
-                    (get_local $i1)
-                    (i32.const 1)
-                  )
+              )
+              (i32.store8 align=1
+                (get_local $i1)
+                (i32.load8_s align=1
+                  (get_local $i2)
                 )
-                (set_local $i2
-                  (i32.add
-                    (get_local $i2)
-                    (i32.const 1)
-                  )
+              )
+              (set_local $i1
+                (i32.add
+                  (get_local $i1)
+                  (i32.const 1)
                 )
-                (set_local $i3
-                  (i32.sub
-                    (get_local $i3)
-                    (i32.const 1)
-                  )
+              )
+              (set_local $i2
+                (i32.add
+                  (get_local $i2)
+                  (i32.const 1)
+                )
+              )
+              (set_local $i3
+                (i32.sub
+                  (get_local $i3)
+                  (i32.const 1)
                 )
               )
               (br $while-in$1)
@@ -10803,30 +10795,28 @@
                 (nop)
                 (br $while-out$2)
               )
-              (block
-                (i32.store align=4
-                  (get_local $i1)
-                  (i32.load align=4
-                    (get_local $i2)
-                  )
+              (i32.store align=4
+                (get_local $i1)
+                (i32.load align=4
+                  (get_local $i2)
                 )
-                (set_local $i1
-                  (i32.add
-                    (get_local $i1)
-                    (i32.const 4)
-                  )
+              )
+              (set_local $i1
+                (i32.add
+                  (get_local $i1)
+                  (i32.const 4)
                 )
-                (set_local $i2
-                  (i32.add
-                    (get_local $i2)
-                    (i32.const 4)
-                  )
+              )
+              (set_local $i2
+                (i32.add
+                  (get_local $i2)
+                  (i32.const 4)
                 )
-                (set_local $i3
-                  (i32.sub
-                    (get_local $i3)
-                    (i32.const 4)
-                  )
+              )
+              (set_local $i3
+                (i32.sub
+                  (get_local $i3)
+                  (i32.const 4)
                 )
               )
               (br $while-in$3)
@@ -10844,30 +10834,28 @@
             (nop)
             (br $while-out$4)
           )
-          (block
-            (i32.store8 align=1
-              (get_local $i1)
-              (i32.load8_s align=1
-                (get_local $i2)
-              )
+          (i32.store8 align=1
+            (get_local $i1)
+            (i32.load8_s align=1
+              (get_local $i2)
             )
-            (set_local $i1
-              (i32.add
-                (get_local $i1)
-                (i32.const 1)
-              )
+          )
+          (set_local $i1
+            (i32.add
+              (get_local $i1)
+              (i32.const 1)
             )
-            (set_local $i2
-              (i32.add
-                (get_local $i2)
-                (i32.const 1)
-              )
+          )
+          (set_local $i2
+            (i32.add
+              (get_local $i2)
+              (i32.const 1)
             )
-            (set_local $i3
-              (i32.sub
-                (get_local $i3)
-                (i32.const 1)
-              )
+          )
+          (set_local $i3
+            (i32.sub
+              (get_local $i3)
+              (i32.const 1)
             )
           )
           (br $while-in$5)
@@ -10960,16 +10948,14 @@
                   (nop)
                   (br $while-out$0)
                 )
-                (block
-                  (i32.store8 align=1
+                (i32.store8 align=1
+                  (get_local $i1)
+                  (get_local $i2)
+                )
+                (set_local $i1
+                  (i32.add
                     (get_local $i1)
-                    (get_local $i2)
-                  )
-                  (set_local $i1
-                    (i32.add
-                      (get_local $i1)
-                      (i32.const 1)
-                    )
+                    (i32.const 1)
                   )
                 )
                 (br $while-in$1)
@@ -10987,16 +10973,14 @@
               (nop)
               (br $while-out$2)
             )
-            (block
-              (i32.store align=4
+            (i32.store align=4
+              (get_local $i1)
+              (get_local $i6)
+            )
+            (set_local $i1
+              (i32.add
                 (get_local $i1)
-                (get_local $i6)
-              )
-              (set_local $i1
-                (i32.add
-                  (get_local $i1)
-                  (i32.const 4)
-                )
+                (i32.const 4)
               )
             )
             (br $while-in$3)
@@ -11014,16 +10998,14 @@
           (nop)
           (br $while-out$4)
         )
-        (block
-          (i32.store8 align=1
+        (i32.store8 align=1
+          (get_local $i1)
+          (get_local $i2)
+        )
+        (set_local $i1
+          (i32.add
             (get_local $i1)
-            (get_local $i2)
-          )
-          (set_local $i1
-            (i32.add
-              (get_local $i1)
-              (i32.const 1)
-            )
+            (i32.const 1)
           )
         )
         (br $while-in$5)
@@ -11095,19 +11077,17 @@
                     (i32.const 20)
                   )
                 )
-                (block
-                  (set_local $i6
-                    (i32.load align=4
-                      (get_local $i5)
-                    )
+                (set_local $i6
+                  (i32.load align=4
+                    (get_local $i5)
                   )
-                  (i32.lt_u
-                    (get_local $i6)
-                    (i32.load align=4
-                      (i32.add
-                        (get_local $i2)
-                        (i32.const 16)
-                      )
+                )
+                (i32.lt_u
+                  (get_local $i6)
+                  (i32.load align=4
+                    (i32.add
+                      (get_local $i2)
+                      (i32.const 16)
                     )
                   )
                 )
@@ -11489,33 +11469,29 @@
               )
             )
           )
-          (block
-            (i32.store align=4
-              (i32.add
-                (get_local $i5)
-                (i32.const 4)
-              )
-              (i32.const 21505)
+          (i32.store align=4
+            (i32.add
+              (get_local $i5)
+              (i32.const 4)
             )
-            (block
-              (i32.store align=4
-                (i32.add
-                  (get_local $i5)
-                  (i32.const 8)
-                )
-                (i32.add
-                  (get_local $i4)
-                  (i32.const 12)
-                )
-              )
-              (i32.ne
-                (call_import $___syscall54
-                  (i32.const 54)
-                  (get_local $i5)
-                )
-                (i32.const 0)
-              )
+            (i32.const 21505)
+          )
+          (i32.store align=4
+            (i32.add
+              (get_local $i5)
+              (i32.const 8)
             )
+            (i32.add
+              (get_local $i4)
+              (i32.const 12)
+            )
+          )
+          (i32.ne
+            (call_import $___syscall54
+              (i32.const 54)
+              (get_local $i5)
+            )
+            (i32.const 0)
           )
         )
         (i32.const 0)
diff --git a/test/emcc_hello_world.fromasm b/test/emcc_hello_world.fromasm
index bea407a53..574eb098a 100644
--- a/test/emcc_hello_world.fromasm
+++ b/test/emcc_hello_world.fromasm
@@ -30427,13 +30427,11 @@
         )
       )
     )
-    (block
-      (i32.store align=4
-        (i32.const 168)
-        (get_local $h)
-      )
-      (get_local $l)
+    (i32.store align=4
+      (i32.const 168)
+      (get_local $h)
     )
+    (get_local $l)
   )
   (func $_i64Add (param $a i32) (param $b i32) (param $c i32) (param $d i32) (result i32)
     (local $l i32)
@@ -30456,13 +30454,11 @@
         )
       )
     )
-    (block
-      (i32.store align=4
-        (i32.const 168)
-        (get_local $h)
-      )
-      (get_local $l)
+    (i32.store align=4
+      (i32.const 168)
+      (get_local $h)
     )
+    (get_local $l)
   )
   (func $_memset (param $ptr i32) (param $value i32) (param $num i32) (result i32)
     (local $stop i32)
@@ -30545,16 +30541,14 @@
                   (nop)
                   (br $while-out$0)
                 )
-                (block
-                  (i32.store8 align=1
+                (i32.store8 align=1
+                  (get_local $ptr)
+                  (get_local $value)
+                )
+                (set_local $ptr
+                  (i32.add
                     (get_local $ptr)
-                    (get_local $value)
-                  )
-                  (set_local $ptr
-                    (i32.add
-                      (get_local $ptr)
-                      (i32.const 1)
-                    )
+                    (i32.const 1)
                   )
                 )
                 (br $while-in$1)
@@ -30572,16 +30566,14 @@
               (nop)
               (br $while-out$2)
             )
-            (block
-              (i32.store align=4
+            (i32.store align=4
+              (get_local $ptr)
+              (get_local $value4)
+            )
+            (set_local $ptr
+              (i32.add
                 (get_local $ptr)
-                (get_local $value4)
-              )
-              (set_local $ptr
-                (i32.add
-                  (get_local $ptr)
-                  (i32.const 4)
-                )
+                (i32.const 4)
               )
             )
             (br $while-in$3)
@@ -30599,16 +30591,14 @@
           (nop)
           (br $while-out$4)
         )
-        (block
-          (i32.store8 align=1
+        (i32.store8 align=1
+          (get_local $ptr)
+          (get_local $value)
+        )
+        (set_local $ptr
+          (i32.add
             (get_local $ptr)
-            (get_local $value)
-          )
-          (set_local $ptr
-            (i32.add
-              (get_local $ptr)
-              (i32.const 1)
-            )
+            (i32.const 1)
           )
         )
         (br $while-in$5)
@@ -30782,39 +30772,37 @@
                 (nop)
                 (br $while-out$0)
               )
-              (block
-                (if
-                  (i32.eq
-                    (get_local $num)
-                    (i32.const 0)
-                  )
-                  (br $topmost
-                    (get_local $ret)
-                  )
+              (if
+                (i32.eq
+                  (get_local $num)
+                  (i32.const 0)
                 )
-                (i32.store8 align=1
-                  (get_local $dest)
-                  (i32.load8_s align=1
-                    (get_local $src)
-                  )
+                (br $topmost
+                  (get_local $ret)
                 )
-                (set_local $dest
-                  (i32.add
-                    (get_local $dest)
-                    (i32.const 1)
-                  )
+              )
+              (i32.store8 align=1
+                (get_local $dest)
+                (i32.load8_s align=1
+                  (get_local $src)
                 )
-                (set_local $src
-                  (i32.add
-                    (get_local $src)
-                    (i32.const 1)
-                  )
+              )
+              (set_local $dest
+                (i32.add
+                  (get_local $dest)
+                  (i32.const 1)
                 )
-                (set_local $num
-                  (i32.sub
-                    (get_local $num)
-                    (i32.const 1)
-                  )
+              )
+              (set_local $src
+                (i32.add
+                  (get_local $src)
+                  (i32.const 1)
+                )
+              )
+              (set_local $num
+                (i32.sub
+                  (get_local $num)
+                  (i32.const 1)
                 )
               )
               (br $while-in$1)
@@ -30830,30 +30818,28 @@
                 (nop)
                 (br $while-out$2)
               )
-              (block
-                (i32.store align=4
-                  (get_local $dest)
-                  (i32.load align=4
-                    (get_local $src)
-                  )
+              (i32.store align=4
+                (get_local $dest)
+                (i32.load align=4
+                  (get_local $src)
                 )
-                (set_local $dest
-                  (i32.add
-                    (get_local $dest)
-                    (i32.const 4)
-                  )
+              )
+              (set_local $dest
+                (i32.add
+                  (get_local $dest)
+                  (i32.const 4)
                 )
-                (set_local $src
-                  (i32.add
-                    (get_local $src)
-                    (i32.const 4)
-                  )
+              )
+              (set_local $src
+                (i32.add
+                  (get_local $src)
+                  (i32.const 4)
                 )
-                (set_local $num
-                  (i32.sub
-                    (get_local $num)
-                    (i32.const 4)
-                  )
+              )
+              (set_local $num
+                (i32.sub
+                  (get_local $num)
+                  (i32.const 4)
                 )
               )
               (br $while-in$3)
@@ -30871,30 +30857,28 @@
             (nop)
             (br $while-out$4)
           )
-          (block
-            (i32.store8 align=1
-              (get_local $dest)
-              (i32.load8_s align=1
-                (get_local $src)
-              )
+          (i32.store8 align=1
+            (get_local $dest)
+            (i32.load8_s align=1
+              (get_local $src)
             )
-            (set_local $dest
-              (i32.add
-                (get_local $dest)
-                (i32.const 1)
-              )
+          )
+          (set_local $dest
+            (i32.add
+              (get_local $dest)
+              (i32.const 1)
             )
-            (set_local $src
-              (i32.add
-                (get_local $src)
-                (i32.const 1)
-              )
+          )
+          (set_local $src
+            (i32.add
+              (get_local $src)
+              (i32.const 1)
             )
-            (set_local $num
-              (i32.sub
-                (get_local $num)
-                (i32.const 1)
-              )
+          )
+          (set_local $num
+            (i32.sub
+              (get_local $num)
+              (i32.const 1)
             )
           )
           (br $while-in$5)
@@ -31121,46 +31105,44 @@
         (get_local $$1)
       )
     )
-    (block
-      (i32.store align=4
-        (i32.const 168)
+    (i32.store align=4
+      (i32.const 168)
+      (i32.add
         (i32.add
-          (i32.add
-            (i32.shr_u
-              (get_local $$8)
-              (i32.const 16)
-            )
-            (i32.mul
-              (get_local $$11)
-              (get_local $$6)
-            )
-          )
           (i32.shr_u
-            (i32.add
-              (i32.and
-                (get_local $$8)
-                (i32.const 65535)
-              )
-              (get_local $$12)
-            )
+            (get_local $$8)
             (i32.const 16)
           )
+          (i32.mul
+            (get_local $$11)
+            (get_local $$6)
+          )
         )
-      )
-      (i32.or
-        (i32.const 0)
-        (i32.or
-          (i32.shl
-            (i32.add
+        (i32.shr_u
+          (i32.add
+            (i32.and
               (get_local $$8)
-              (get_local $$12)
+              (i32.const 65535)
             )
-            (i32.const 16)
+            (get_local $$12)
           )
-          (i32.and
-            (get_local $$3)
-            (i32.const 65535)
+          (i32.const 16)
+        )
+      )
+    )
+    (i32.or
+      (i32.const 0)
+      (i32.or
+        (i32.shl
+          (i32.add
+            (get_local $$8)
+            (get_local $$12)
           )
+          (i32.const 16)
+        )
+        (i32.and
+          (get_local $$3)
+          (i32.const 65535)
         )
       )
     )
@@ -31532,13 +31514,11 @@
       (i32.const 8)
       (get_local $__stackBase__)
     )
-    (block
-      (i32.store align=4
-        (i32.const 168)
-        (get_local $$10$1)
-      )
-      (get_local $$10$0)
+    (i32.store align=4
+      (i32.const 168)
+      (get_local $$10$1)
     )
+    (get_local $$10$0)
   )
   (func $___muldi3 (param $$a$0 i32) (param $$a$1 i32) (param $$b$0 i32) (param $$b$1 i32) (result i32)
     (local $$x_sroa_0_0_extract_trunc i32)
@@ -31569,34 +31549,32 @@
         (get_local $$y_sroa_0_0_extract_trunc)
       )
     )
-    (block
-      (i32.store align=4
-        (i32.const 168)
-        (i32.or
+    (i32.store align=4
+      (i32.const 168)
+      (i32.or
+        (i32.add
           (i32.add
-            (i32.add
-              (i32.mul
-                (get_local $$b$1)
-                (get_local $$x_sroa_0_0_extract_trunc)
-              )
-              (get_local $$2)
+            (i32.mul
+              (get_local $$b$1)
+              (get_local $$x_sroa_0_0_extract_trunc)
             )
-            (get_local $$1$1)
-          )
-          (i32.and
-            (get_local $$1$1)
-            (i32.const 0)
+            (get_local $$2)
           )
+          (get_local $$1$1)
         )
-      )
-      (i32.or
-        (i32.const 0)
         (i32.and
-          (get_local $$1$0)
-          (i32.const -1)
+          (get_local $$1$1)
+          (i32.const 0)
         )
       )
     )
+    (i32.or
+      (i32.const 0)
+      (i32.and
+        (get_local $$1$0)
+        (i32.const -1)
+      )
+    )
   )
   (func $___udivdi3 (param $$a$0 i32) (param $$a$1 i32) (param $$b$0 i32) (param $$b$1 i32) (result i32)
     (local $$1$0 i32)
@@ -31642,20 +31620,18 @@
       (i32.const 8)
       (get_local $__stackBase__)
     )
-    (block
-      (i32.store align=4
-        (i32.const 168)
-        (i32.load align=4
-          (i32.add
-            (get_local $$rem)
-            (i32.const 4)
-          )
-        )
-      )
+    (i32.store align=4
+      (i32.const 168)
       (i32.load align=4
-        (get_local $$rem)
+        (i32.add
+          (get_local $$rem)
+          (i32.const 4)
+        )
       )
     )
+    (i32.load align=4
+      (get_local $$rem)
+    )
   )
   (func $___udivmoddi4 (param $$a$0 i32) (param $$a$1 i32) (param $$b$0 i32) (param $$b$1 i32) (param $$rem i32) (result i32)
     (local $$n_sroa_0_0_extract_trunc i32)
@@ -32901,13 +32877,11 @@
           (get_local $$carry_0_lcssa$0)
         )
       )
-      (block
-        (i32.store align=4
-          (i32.const 168)
-          (get_local $$_0$1)
-        )
-        (get_local $$_0$0)
+      (i32.store align=4
+        (i32.const 168)
+        (get_local $$_0$1)
       )
+      (get_local $$_0$0)
     )
   )
   (func $dynCall_ii (param $index i32) (param $a1 i32) (result i32)
diff --git a/test/passes/merge-blocks.txt b/test/passes/merge-blocks.txt
new file mode 100644
index 000000000..876fe7b2f
--- /dev/null
+++ b/test/passes/merge-blocks.txt
@@ -0,0 +1,170 @@
+(module
+  (memory 16777216 16777216)
+  (func $b0-yes (param $i1 i32)
+    (block $topmost
+      (block $block0
+        (i32.const 10)
+      )
+    )
+  )
+  (func $b1-yes (param $i1 i32)
+    (block $topmost
+      (block $block0
+        (block $block1
+          (i32.const 10)
+        )
+      )
+    )
+  )
+  (func $b2-yes (param $i1 i32)
+    (block $topmost
+      (i32.const 5)
+      (block $block0
+        (i32.const 10)
+      )
+      (i32.const 15)
+    )
+  )
+  (func $b3-yes (param $i1 i32)
+    (block $topmost
+      (i32.const 3)
+      (block $block0
+        (i32.const 6)
+        (block $block1
+          (i32.const 10)
+        )
+        (i32.const 15)
+      )
+      (i32.const 20)
+    )
+  )
+  (func $b4 (param $i1 i32)
+    (block $topmost
+      (block $inner
+        (i32.const 10)
+        (br $inner)
+      )
+    )
+  )
+  (func $b5 (param $i1 i32)
+    (block $topmost
+      (block $middle
+        (block $inner
+          (i32.const 10)
+          (br $inner)
+        )
+        (br $middle)
+      )
+    )
+  )
+  (func $b6 (param $i1 i32)
+    (block $topmost
+      (i32.const 5)
+      (block $inner
+        (i32.const 10)
+        (br $inner)
+      )
+      (i32.const 15)
+    )
+  )
+  (func $b7 (param $i1 i32)
+    (block $topmost
+      (i32.const 3)
+      (block $middle
+        (i32.const 6)
+        (block $inner
+          (i32.const 10)
+          (br $inner)
+        )
+        (i32.const 15)
+        (br $middle)
+      )
+      (i32.const 20)
+    )
+  )
+)
+(module
+  (memory 16777216 16777216)
+  (func $b0-yes (param $i1 i32)
+    (block $topmost
+      (block $block0
+        (i32.const 10)
+      )
+    )
+  )
+  (func $b1-yes (param $i1 i32)
+    (block $topmost
+      (block $block0
+        (block $block1
+          (i32.const 10)
+        )
+      )
+    )
+  )
+  (func $b2-yes (param $i1 i32)
+    (block $topmost
+      (i32.const 5)
+      (block $block0
+        (i32.const 10)
+      )
+      (i32.const 15)
+    )
+  )
+  (func $b3-yes (param $i1 i32)
+    (block $topmost
+      (i32.const 3)
+      (block $block0
+        (i32.const 6)
+        (block $block1
+          (i32.const 10)
+        )
+        (i32.const 15)
+      )
+      (i32.const 20)
+    )
+  )
+  (func $b4 (param $i1 i32)
+    (block $topmost
+      (block $inner
+        (i32.const 10)
+        (br $inner)
+      )
+    )
+  )
+  (func $b5 (param $i1 i32)
+    (block $topmost
+      (block $middle
+        (block $inner
+          (i32.const 10)
+          (br $inner)
+        )
+        (br $middle)
+      )
+    )
+  )
+  (func $b6 (param $i1 i32)
+    (block $topmost
+      (i32.const 5)
+      (block $inner
+        (i32.const 10)
+        (br $inner)
+      )
+      (i32.const 15)
+    )
+  )
+  (func $b7 (param $i1 i32)
+    (block $topmost
+      (i32.const 3)
+      (block $middle
+        (i32.const 6)
+        (block $inner
+          (i32.const 10)
+          (br $inner)
+        )
+        (i32.const 15)
+        (br $middle)
+      )
+      (i32.const 20)
+    )
+  )
+)
diff --git a/test/passes/merge-blocks.wast b/test/passes/merge-blocks.wast
new file mode 100644
index 000000000..bd58ebc38
--- /dev/null
+++ b/test/passes/merge-blocks.wast
@@ -0,0 +1,86 @@
+(module
+  (memory 16777216 16777216)
+  (func $b0-yes (param $i1 i32)
+    (block $topmost
+      (block
+        (i32.const 10)
+      )
+    )
+  )
+  (func $b1-yes (param $i1 i32)
+    (block $topmost
+      (block
+        (block
+          (i32.const 10)
+        )
+      )
+    )
+  )
+  (func $b2-yes (param $i1 i32)
+    (block $topmost
+      (i32.const 5)
+      (block
+        (i32.const 10)
+      )
+      (i32.const 15)
+    )
+  )
+  (func $b3-yes (param $i1 i32)
+    (block $topmost
+      (i32.const 3)
+      (block
+        (i32.const 6)
+        (block
+          (i32.const 10)
+        )
+        (i32.const 15)
+      )
+      (i32.const 20)
+    )
+  )
+  (func $b4 (param $i1 i32)
+    (block $topmost
+      (block $inner
+        (i32.const 10)
+        (br $inner)
+      )
+    )
+  )
+  (func $b5 (param $i1 i32)
+    (block $topmost
+      (block $middle
+        (block $inner
+          (i32.const 10)
+          (br $inner)
+        )
+        (br $middle)
+      )
+    )
+  )
+  (func $b6 (param $i1 i32)
+    (block $topmost
+      (i32.const 5)
+      (block $inner
+        (i32.const 10)
+        (br $inner)
+      )
+      (i32.const 15)
+    )
+  )
+  (func $b7 (param $i1 i32)
+    (block $topmost
+      (i32.const 3)
+      (block $middle
+        (i32.const 6)
+        (block $inner
+          (i32.const 10)
+          (br $inner)
+        )
+        (i32.const 15)
+        (br $middle)
+      )
+      (i32.const 20)
+    )
+  )
+)
+