wasm2js: handle unreachable select and global.set (#2029)

1 files changed, 21 insertions, 0 deletions

diff --git a/src/passes/I64ToI32Lowering.cpp b/src/passes/I64ToI32Lowering.cpp
index a1686d27d..33bb7229e 100644
--- a/src/passes/I64ToI32Lowering.cpp
+++ b/src/passes/I64ToI32Lowering.cpp
@@ -28,6 +28,7 @@
 #include "support/name.h"
 #include "wasm-builder.h"
 #include "ir/flat.h"
+#include "ir/iteration.h"
 #include "ir/memory-utils.h"
 #include "ir/module-utils.h"
 #include "ir/names.h"
@@ -464,6 +465,7 @@ struct I64ToI32Lowering : public WalkerPass<PostWalker<I64ToI32Lowering>> {
   }
 
   void visitSetGlobal(SetGlobal* curr) {
+    if (handleUnreachable(curr)) return;
     if (!originallyI64Globals.count(curr->name)) return;
     TempVar highBits = fetchOutParam(curr->value);
     auto* setHigh = builder->makeSetGlobal(
@@ -1578,6 +1580,7 @@ struct I64ToI32Lowering : public WalkerPass<PostWalker<I64ToI32Lowering>> {
   }
 
   void visitSelect(Select* curr) {
+    if (handleUnreachable(curr)) return;
     if (!hasOutParam(curr->ifTrue)) {
       assert(!hasOutParam(curr->ifFalse));
       return;
@@ -1669,6 +1672,24 @@ private:
     highBitVars.erase(e);
     return ret;
   }
+
+  // If e.g. a select is unreachable, then one arm may have an out param
+  // but not the other. In this case dce should really have been run
+  // before; handle it in a simple way here.
+  bool handleUnreachable(Expression* curr) {
+    if (curr->type != unreachable) return false;
+    std::vector<Expression*> children;
+    for (auto* child : ChildIterator(curr)) {
+      if (isConcreteType(child->type)) {
+        child = builder->makeDrop(child);
+      }
+      children.push_back(child);
+    }
+    auto* block = builder->makeBlock(children);
+    assert(block->type == unreachable);
+    replaceCurrent(block);
+    return true;
+  }
 };
 
 Pass *createI64ToI32LoweringPass() {