don't conditionalize an unreachable binary, the if might have a diffe…

…rent type
WebAssembly · Aug 30, 2017 · f23a92d · f23a92d
1 parent 2b73e69
commit f23a92d
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diff --git a/src/passes/OptimizeInstructions.cpp b/src/passes/OptimizeInstructions.cpp
@@ -872,6 +872,9 @@ struct OptimizeInstructions : public WalkerPass<PostWalker<OptimizeInstructions,
   //   expensive | cheap     can be turned into cheap     ? 1 : expensive,
   // so that we can avoid one expensive computation, if it has no side effects.
   Expression* conditionalizeExpensiveOnBitwise(Binary* binary) {
+    // if this contains dead code, don't bother trying to optimize it, the type
+    // might change (if might not be unreachable if just one arm is)
+    if (binary->type == unreachable) return nullptr;
     // this operation can increase code size, so don't always do it
     auto& options = getPassRunner()->options;
     if (options.optimizeLevel < 2 || options.shrinkLevel > 0) return nullptr;

diff --git a/test/passes/optimize-instructions_optimize-level=2_ignore-implicit-traps.txt b/test/passes/optimize-instructions_optimize-level=2_ignore-implicit-traps.txt
@@ -1,5 +1,6 @@
 (module
  (type $0 (func (param i32 i32) (result i32)))
+ (type $1 (func (result f64)))
  (memory $0 0)
  (func $conditionals (type $0) (param $0 i32) (param $1 i32) (result i32)
   (local $2 i32)
@@ -321,4 +322,41 @@
    (get_local $1)
   )
  )
+ (func $conditionalize-if-type-change (type $1) (result f64)
+  (local $0 i32)
+  (drop
+   (loop $label$1 (result f32)
+    (block $label$2 (result f32)
+     (drop
+      (block $label$3 (result f32)
+       (br_if $label$1
+        (i32.or
+         (f32.gt
+          (br_if $label$3
+           (f32.const 1)
+           (get_local $0)
+          )
+          (br $label$2
+           (f32.const 71)
+          )
+         )
+         (i64.eqz
+          (select
+           (i64.const 58)
+           (i64.const -982757)
+           (i64.eqz
+            (i64.const 0)
+           )
+          )
+         )
+        )
+       )
+      )
+     )
+     (f32.const 1)
+    )
+   )
+  )
+  (f64.const -nan:0xfffffffffffff)
+ )
 )
diff --git a/test/passes/optimize-instructions_optimize-level=2_ignore-implicit-traps.wast b/test/passes/optimize-instructions_optimize-level=2_ignore-implicit-traps.wast
@@ -323,5 +323,43 @@
    )
    (return (get_local $1))
   )
+
+ (func $conditionalize-if-type-change (result f64)
+  (local $0 i32)
+  (drop
+   (loop $label$1 (result f32)
+    (block $label$2 (result f32)
+     (drop
+      (block $label$3 (result f32)
+       (br_if $label$1
+        (i32.or ;; this turns into an if, but then the if might not be unreachable
+         (f32.gt
+          (br_if $label$3
+           (f32.const 1)
+           (get_local $0)
+          )
+          (br $label$2
+           (f32.const 71)
+          )
+         )
+         (i64.eqz
+          (select
+           (i64.const 58)
+           (i64.const -982757)
+           (i64.eqz
+            (i64.const 0)
+           )
+          )
+         )
+        )
+       )
+      )
+     )
+     (f32.const 1)
+    )
+   )
+  )
+  (f64.const -nan:0xfffffffffffff)
+ )
 )