optimize eqz^2 in select and br_if

5 files changed, 59 insertions, 50 deletions

diff --git a/src/passes/OptimizeInstructions.cpp b/src/passes/OptimizeInstructions.cpp
index cd0610634..ec646d89f 100644
--- a/src/passes/OptimizeInstructions.cpp
+++ b/src/passes/OptimizeInstructions.cpp
@@ -215,20 +215,35 @@ struct OptimizeInstructions : public WalkerPass<PostWalker<OptimizeInstructions,
         ExpressionManipulator::nop(curr);
       }
     } else if (auto* select = curr->dynCast<Select>()) {
-      // flip select if eqz input and flippable
       auto* condition = select->condition->dynCast<Unary>();
       if (condition && condition->op == EqZInt32) {
-        EffectAnalyzer ifTrue(select->ifTrue);
-        EffectAnalyzer ifFalse(select->ifFalse);
-        if (!ifTrue.invalidates(ifFalse)) {
-          select->condition = condition->value;
-          std::swap(select->ifTrue, select->ifFalse);
+        auto* condition2 = condition->value->dynCast<Unary>();
+        if (condition2 && condition2->op == EqZInt32) {
+          // double eqz
+          select->condition = condition2->value;
+        } else {
+          // flip select, eqz input and flippable
+          EffectAnalyzer ifTrue(select->ifTrue);
+          EffectAnalyzer ifFalse(select->ifFalse);
+          if (!ifTrue.invalidates(ifFalse)) {
+            select->condition = condition->value;
+            std::swap(select->ifTrue, select->ifFalse);
+          }
+        }
+      }
+    } else if (auto* br = curr->dynCast<Break>()) {
+      if (br->condition) {
+        auto* condition = br->condition->dynCast<Unary>();
+        if (condition && condition->op == EqZInt32) {
+          auto* condition2 = condition->value->dynCast<Unary>();
+          if (condition2 && condition2->op == EqZInt32) {
+            // double eqz
+            br->condition = condition2->value;
+          }
         }
       }
     }
     return nullptr;
-    // TODO:
-    //       * eqz^2 can be removed if flowing into a boolean context (we handle if, but need also br_if and select)
   }
 };
 
diff --git a/test/emcc_hello_world.fromasm b/test/emcc_hello_world.fromasm
index fb1163576..06b48ffd6 100644
--- a/test/emcc_hello_world.fromasm
+++ b/test/emcc_hello_world.fromasm
@@ -6601,15 +6601,11 @@
                               (get_local $41)
                               (block
                                 (br_if $do-once$114
-                                  (i32.eqz
-                                    (i32.eqz
-                                      (i32.and
-                                        (i32.load
-                                          (get_local $0)
-                                        )
-                                        (i32.const 32)
-                                      )
+                                  (i32.and
+                                    (i32.load
+                                      (get_local $0)
                                     )
+                                    (i32.const 32)
                                   )
                                 )
                                 (drop
@@ -6955,15 +6951,11 @@
                             (i32.const 0)
                           )
                           (br_if $do-once$106
-                            (i32.eqz
-                              (i32.eqz
-                                (i32.and
-                                  (i32.load
-                                    (get_local $0)
-                                  )
-                                  (i32.const 32)
-                                )
+                            (i32.and
+                              (i32.load
+                                (get_local $0)
                               )
+                              (i32.const 32)
                             )
                           )
                           (drop
@@ -12923,11 +12915,7 @@
                                                   (get_local $16)
                                                 )
                                                 (br_if $do-once$63
-                                                  (i32.eqz
-                                                    (i32.eqz
-                                                      (get_local $16)
-                                                    )
-                                                  )
+                                                  (get_local $16)
                                                 )
                                                 (i32.store
                                                   (i32.const 180)
diff --git a/test/emcc_hello_world.fromasm.imprecise b/test/emcc_hello_world.fromasm.imprecise
index 149c837ec..e83f2b757 100644
--- a/test/emcc_hello_world.fromasm.imprecise
+++ b/test/emcc_hello_world.fromasm.imprecise
@@ -6594,15 +6594,11 @@
                               (get_local $41)
                               (block
                                 (br_if $do-once$114
-                                  (i32.eqz
-                                    (i32.eqz
-                                      (i32.and
-                                        (i32.load
-                                          (get_local $0)
-                                        )
-                                        (i32.const 32)
-                                      )
+                                  (i32.and
+                                    (i32.load
+                                      (get_local $0)
                                     )
+                                    (i32.const 32)
                                   )
                                 )
                                 (drop
@@ -6948,15 +6944,11 @@
                             (i32.const 0)
                           )
                           (br_if $do-once$106
-                            (i32.eqz
-                              (i32.eqz
-                                (i32.and
-                                  (i32.load
-                                    (get_local $0)
-                                  )
-                                  (i32.const 32)
-                                )
+                            (i32.and
+                              (i32.load
+                                (get_local $0)
                               )
+                              (i32.const 32)
                             )
                           )
                           (drop
@@ -12916,11 +12908,7 @@
                                                   (get_local $16)
                                                 )
                                                 (br_if $do-once$63
-                                                  (i32.eqz
-                                                    (i32.eqz
-                                                      (get_local $16)
-                                                    )
-                                                  )
+                                                  (get_local $16)
                                                 )
                                                 (i32.store
                                                   (i32.const 180)
diff --git a/test/passes/optimize-instructions.txt b/test/passes/optimize-instructions.txt
index 6d83cbdbc..ca5f02849 100644
--- a/test/passes/optimize-instructions.txt
+++ b/test/passes/optimize-instructions.txt
@@ -205,5 +205,12 @@
         )
       )
     )
+    (drop
+      (select
+        (i32.const 0)
+        (i32.const 1)
+        (i32.const 2)
+      )
+    )
   )
 )
diff --git a/test/passes/optimize-instructions.wast b/test/passes/optimize-instructions.wast
index 08868e23a..b1a7ab47e 100644
--- a/test/passes/optimize-instructions.wast
+++ b/test/passes/optimize-instructions.wast
@@ -240,5 +240,16 @@
         )
       )
     )
+    (drop
+      (select
+        (i32.const 0)
+        (i32.const 1)
+        (i32.eqz
+          (i32.eqz
+            (i32.const 2)
+          )
+        )
+      )
+    )
   )
 )