Merge pull request #4 from PLUTOFX/copilot/fix-frontend-compilation-error

Fix WebAssemblySpillPointers crash at O2: move pass before PEI

Author: PLUTOFX

.gitignore

@@ -70,3 +70,4 @@ pythonenv*
 /clang/utils/analyzer/projects/*/RefScanBuildResults
 # automodapi puts generated documentation files here.
 /lldb/docs/python_api/
+build/

llvm/lib/Target/WebAssembly/WebAssemblySpillPointers.cpp

@@ -46,7 +46,6 @@ class WebAssemblySpillPointers final : public MachineFunctionPass {
   void getAnalysisUsage(AnalysisUsage &AU) const override {
     AU.setPreservesCFG();
     AU.addRequired<LiveIntervals>();
-    AU.addPreserved<LiveIntervals>();
     MachineFunctionPass::getAnalysisUsage(AU);
   }
 

llvm/lib/Target/WebAssembly/WebAssemblyTargetMachine.cpp

@@ -525,6 +525,11 @@ void WebAssemblyPassConfig::addPostRegAlloc() {
   // control flow.
   disablePass(&MachineBlockPlacementID);
 
+  // Spill pointer-typed values to shadow stack for GC.
+  // This must run before PEI so that frame indices are properly resolved.
+  if (getOptLevel() != CodeGenOpt::None)
+    addPass(createWebAssemblySpillPointers());
+
   TargetPassConfig::addPostRegAlloc();
 }
 
@@ -568,11 +573,6 @@ void WebAssemblyPassConfig::addPreEmitPass() {
     addPass(createWebAssemblyRegColoring());
   }
 
-  // Spill pointer-typed values to shadow stack for GC.
-  // This must run after register allocation but before explicit locals.
-  if (getOptLevel() != CodeGenOpt::None)
-    addPass(createWebAssemblySpillPointers());
-
   // Sort the blocks of the CFG into topological order, a prerequisite for
   // BLOCK and LOOP markers.
   addPass(createWebAssemblyCFGSort());