[llvm] [Reg2Mem] Add legacy pass wrapping Reg2Mem (PR #111024)

[Nathan Gauër via llvm-commits]

https://github.com/Keenuts created https://github.com/llvm/llvm-project/pull/111024

The SPIR-V backend will need to use Reg2Mem, hence this pass needs to be wrapped to be used with the legacy pass manager.

>From 760eefdf4dc0f4bc3d04b3d4f373908c31a14a61 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Nathan=20Gau=C3=ABr?= <brioche at google.com>
Date: Thu, 3 Oct 2024 18:26:10 +0200
Subject: [PATCH] [Reg2Mem] Add legacy pass wrapping Reg2Mem
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The SPIR-V backend will need to use Reg2Mem, hence this pass
needs to be wrapped to be used with the legacy pass manager.

Signed-off-by: Nathan Gauër <brioche at google.com>
---
 llvm/include/llvm/Transforms/Scalar/Reg2Mem.h | 25 +++++++++++++++++
 llvm/lib/Transforms/Scalar/Reg2Mem.cpp        | 28 +++++++++++++++++++
 2 files changed, 53 insertions(+)

diff --git a/llvm/include/llvm/Transforms/Scalar/Reg2Mem.h b/llvm/include/llvm/Transforms/Scalar/Reg2Mem.h
index 25f6563d7dcfc2..f7815ca9a9a18c 100644
--- a/llvm/include/llvm/Transforms/Scalar/Reg2Mem.h
+++ b/llvm/include/llvm/Transforms/Scalar/Reg2Mem.h
@@ -13,7 +13,11 @@
 #ifndef LLVM_TRANSFORMS_SCALAR_REG2MEM_H
 #define LLVM_TRANSFORMS_SCALAR_REG2MEM_H
 
+#include "llvm/Analysis/LoopInfo.h"
+#include "llvm/IR/Dominators.h"
 #include "llvm/IR/PassManager.h"
+#include "llvm/InitializePasses.h"
+#include "llvm/Pass.h"
 
 namespace llvm {
 
@@ -22,6 +26,27 @@ class RegToMemPass : public PassInfoMixin<RegToMemPass> {
   PreservedAnalyses run(Function &F, FunctionAnalysisManager &AM);
 };
 
+class RegToMemWrapperPass : public FunctionPass {
+public:
+  static char ID;
+
+  RegToMemWrapperPass();
+
+  void getAnalysisUsage(AnalysisUsage &AU) const override {
+    AU.setPreservesAll();
+
+    AU.addPreserved<DominatorTreeWrapperPass>();
+    AU.addRequired<DominatorTreeWrapperPass>();
+
+    AU.addPreserved<LoopInfoWrapperPass>();
+    AU.addRequired<LoopInfoWrapperPass>();
+  }
+
+  bool runOnFunction(Function &F) override;
+};
+
+FunctionPass *createRegToMemWrapperPass();
+
 } // end namespace llvm
 
 #endif // LLVM_TRANSFORMS_SCALAR_REG2MEM_H
diff --git a/llvm/lib/Transforms/Scalar/Reg2Mem.cpp b/llvm/lib/Transforms/Scalar/Reg2Mem.cpp
index ebc5075aa36fe8..33ae5faeba1198 100644
--- a/llvm/lib/Transforms/Scalar/Reg2Mem.cpp
+++ b/llvm/lib/Transforms/Scalar/Reg2Mem.cpp
@@ -105,3 +105,31 @@ PreservedAnalyses RegToMemPass::run(Function &F, FunctionAnalysisManager &AM) {
   PA.preserve<LoopAnalysis>();
   return PA;
 }
+
+namespace llvm {
+void initializeRegToMemWrapperPassPass(PassRegistry &);
+} // namespace llvm
+
+INITIALIZE_PASS_BEGIN(RegToMemWrapperPass, "reg-to-mem", "", true, true)
+INITIALIZE_PASS_DEPENDENCY(DominatorTreeWrapperPass);
+INITIALIZE_PASS_DEPENDENCY(LoopInfoWrapperPass);
+INITIALIZE_PASS_END(RegToMemWrapperPass, "reg-to-mem", "", true, true)
+
+char RegToMemWrapperPass::ID = 0;
+
+RegToMemWrapperPass::RegToMemWrapperPass() : FunctionPass(ID) {}
+
+bool RegToMemWrapperPass::runOnFunction(Function &F) {
+  DominatorTree *DT = &getAnalysis<DominatorTreeWrapperPass>().getDomTree();
+  LoopInfo *LI = &getAnalysis<LoopInfoWrapperPass>().getLoopInfo();
+
+  unsigned N = SplitAllCriticalEdges(F, CriticalEdgeSplittingOptions(DT, LI));
+  bool Changed = runPass(F);
+  if (N == 0 && !Changed)
+    return false;
+  return true;
+}
+
+FunctionPass *llvm::createRegToMemWrapperPass() {
+  return new RegToMemWrapperPass();
+}