Handle EM_ASM/EM_JS in LLVM wasm backend O0 output (#1888)

See emscripten-core/emscripten#7928 - we have been optimizing all wasms until now, and noticed this when the wasm object file path did not do so. When not optimizing, our methods of handling EM_ASM and EM_JS fail since the patterns are different.

Specifically, for EM_ASM we hunt for emscripten_asm_const(X, where X is a constant, but without opts it may be a get of a local. For EM_JS, the function body may not just contain a const, but a block with a set of the const and a return of a get later.

This adds logic to track gets and sets in basic blocks, which is sufficient to handle this.

1 files changed, 10 insertions, 8 deletions

diff --git a/src/tools/wasm-emscripten-finalize.cpp b/src/tools/wasm-emscripten-finalize.cpp
index 3ea3629c5..5c2e37ac3 100644
--- a/src/tools/wasm-emscripten-finalize.cpp
+++ b/src/tools/wasm-emscripten-finalize.cpp
@@ -173,14 +173,16 @@ int main(int argc, const char *argv[]) {
   EmscriptenGlueGenerator generator(wasm);
   generator.fixInvokeFunctionNames();
 
-  PassRunner passRunner(&wasm);
-  passRunner.setDebug(options.debug);
-  passRunner.setDebugInfo(debugInfo);
-  passRunner.add(ABI::getLegalizationPass(
-    legalizeJavaScriptFFI ? ABI::LegalizationLevel::Full
-                          : ABI::LegalizationLevel::Minimal
-  ));
-  passRunner.run();
+  {
+    PassRunner passRunner(&wasm);
+    passRunner.setDebug(options.debug);
+    passRunner.setDebugInfo(debugInfo);
+    passRunner.add(ABI::getLegalizationPass(
+      legalizeJavaScriptFFI ? ABI::LegalizationLevel::Full
+                            : ABI::LegalizationLevel::Minimal
+    ));
+    passRunner.run();
+  }
 
   std::vector<Name> initializerFunctions;