[llvm] [WebAssembly] Add RefTypeMem2Local pass (PR #81965)

[Heejin Ahn via llvm-commits]

================
@@ -0,0 +1,91 @@
+//=== WebAssemblyRefTypeMem2Local.cpp - WebAssembly RefType Mem2Local -----===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+///
+/// \file
+/// Assign reference type allocas to local addrspace (addrspace(1)) so that
+/// their loads and stores can be lowered to local.gets/local.sets.
+///
+//===----------------------------------------------------------------------===//
+
+#include "Utils/WasmAddressSpaces.h"
+#include "Utils/WebAssemblyTypeUtilities.h"
+#include "WebAssembly.h"
+#include "llvm/IR/IRBuilder.h"
+#include "llvm/IR/InstVisitor.h"
+#include "llvm/IR/ValueHandle.h"
+#include "llvm/Pass.h"
+using namespace llvm;
+
+#define DEBUG_TYPE "wasm-ref-type-mem2local"
+
+namespace {
+class WebAssemblyRefTypeMem2Local final
+    : public FunctionPass,
+      public InstVisitor<WebAssemblyRefTypeMem2Local> {
+  StringRef getPassName() const override {
+    return "WebAssembly Refernce Types Memory to Local";
+  }
+
+  void getAnalysisUsage(AnalysisUsage &AU) const override {
+    AU.setPreservesCFG();
+    FunctionPass::getAnalysisUsage(AU);
+  }
+
+  bool runOnFunction(Function &F) override;
+  bool Changed = false;
+
+public:
+  static char ID;
+  WebAssemblyRefTypeMem2Local() : FunctionPass(ID) {}
+
+  void visitAllocaInst(AllocaInst &AI);
+};
+} // End anonymous namespace
+
+char WebAssemblyRefTypeMem2Local::ID = 0;
+INITIALIZE_PASS(WebAssemblyRefTypeMem2Local, DEBUG_TYPE,
+                "Assign reference type allocas to local address space", true,
+                false)
+
+FunctionPass *llvm::createWebAssemblyRefTypeMem2Local() {
+  return new WebAssemblyRefTypeMem2Local();
+}
+
+void WebAssemblyRefTypeMem2Local::visitAllocaInst(AllocaInst &AI) {
+  if (WebAssembly::isWebAssemblyReferenceType(AI.getAllocatedType())) {
+    Changed = true;
+    IRBuilder<> IRB(AI.getContext());
+    IRB.SetInsertPoint(&AI);
+    auto *NewAI = IRB.CreateAlloca(AI.getAllocatedType(),
+                                   WebAssembly::WASM_ADDRESS_SPACE_VAR, nullptr,
+                                   AI.getName() + ".var");
+
+    // The below is basically equivalent to AI.replaceAllUsesWith(NewAI), but we
+    // cannot use it because it requires the old and new types be the same,
+    // which is not true here because the address spaces are different.
----------------
aheejin wrote:

I couldn't do `AI.replaceAllUsesWith(NewAI)` because of this assertion: https://github.com/llvm/llvm-project/blob/3af5c98200e0b1268f755c3f289be4f73aac4214/llvm/lib/IR/Value.cpp#L507-L508

https://github.com/llvm/llvm-project/pull/81965