ignore untaken branches in determining block type

Author: kripken

src/wasm/wasm.cpp

@@ -109,18 +109,20 @@ struct TypeSeeker : public PostWalker<TypeSeeker> {
   Name targetName;
   std::vector<WasmType> types;
 
+
   TypeSeeker(Expression* target, Name targetName) : target(target), targetName(targetName) {
     Expression* temp = target;
     walk(temp);
   }
 
   void visitBreak(Break* curr) {
-    if (curr->name == targetName) {
+    if (curr->name == targetName && BranchUtils::isBranchTaken(curr)) {
       types.push_back(curr->value ? curr->value->type : none);
     }
   }
 
   void visitSwitch(Switch* curr) {
+    if (!BranchUtils::isBranchTaken(curr)) return;
     for (auto name : curr->targets) {
       if (name == targetName) types.push_back(curr->value ? curr->value->type : none);
     }

test/passes/remove-unused-brs.txt

@@ -1035,4 +1035,17 @@
    )
   )
  )
+ (func $untaken-br-with-concrete-last-element (type $2) (result i32)
+  (block $label$8 (result i32)
+   (block $label$11 (result i32)
+    (block $label$14
+     (br_if $label$8
+      (br $label$11
+       (i32.const 103)
+      )
+     )
+    )
+   )
+  )
+ )
 )

test/passes/remove-unused-brs.wast

@@ -919,5 +919,18 @@
     )
    )
   )
+  (func $untaken-br-with-concrete-last-element (result i32)
+   (block $label$8 (result i32)
+    (block $label$11 (result i32)
+     (block $label$14
+      (br_if $label$14
+       (br $label$11
+        (i32.const 103)
+       )
+      )
+     )
+    )
+   )
+  )
 )