[llvm] [NewPM] Remove Reg2Mem Legacy Pass (PR #73404)

[Aiden Grossman via llvm-commits]

https://github.com/boomanaiden154 created https://github.com/llvm/llvm-project/pull/73404

This pass isn't used anywhere upstream and thus has no test coverage. For these reasons it should be removed.

>From 8d95d92445532817a23421279b1d7aec7ded5cb0 Mon Sep 17 00:00:00 2001
From: Aiden Grossman <agrossman154 at yahoo.com>
Date: Sat, 25 Nov 2023 13:39:41 -0800
Subject: [PATCH] [NewPM] Remove Reg2Mem Legacy Pass

This pass isn't used anywhere upstream and thus has no test coverage.
For these reasons it should be removed.
---
 llvm/include/llvm/InitializePasses.h   |  1 -
 llvm/include/llvm/LinkAllPasses.h      |  1 -
 llvm/include/llvm/Transforms/Scalar.h  |  9 -------
 llvm/lib/Transforms/Scalar/Reg2Mem.cpp | 33 --------------------------
 llvm/lib/Transforms/Scalar/Scalar.cpp  |  1 -
 5 files changed, 45 deletions(-)

diff --git a/llvm/include/llvm/InitializePasses.h b/llvm/include/llvm/InitializePasses.h
index 05122ea98d8ca52..5b15dd82a6e2f56 100644
--- a/llvm/include/llvm/InitializePasses.h
+++ b/llvm/include/llvm/InitializePasses.h
@@ -260,7 +260,6 @@ void initializeRegAllocFastPass(PassRegistry&);
 void initializeRegAllocPriorityAdvisorAnalysisPass(PassRegistry &);
 void initializeRegAllocScoringPass(PassRegistry &);
 void initializeRegBankSelectPass(PassRegistry&);
-void initializeRegToMemLegacyPass(PassRegistry&);
 void initializeRegUsageInfoCollectorPass(PassRegistry&);
 void initializeRegUsageInfoPropagationPass(PassRegistry&);
 void initializeRegionInfoPassPass(PassRegistry&);
diff --git a/llvm/include/llvm/LinkAllPasses.h b/llvm/include/llvm/LinkAllPasses.h
index 927c2d8cde5c478..30bf020daa9546c 100644
--- a/llvm/include/llvm/LinkAllPasses.h
+++ b/llvm/include/llvm/LinkAllPasses.h
@@ -97,7 +97,6 @@ namespace {
       (void) llvm::createNaryReassociatePass();
       (void) llvm::createObjCARCContractPass();
       (void) llvm::createPromoteMemoryToRegisterPass();
-      (void) llvm::createDemoteRegisterToMemoryPass();
       (void)llvm::createPostDomOnlyPrinterWrapperPassPass();
       (void)llvm::createPostDomPrinterWrapperPassPass();
       (void)llvm::createPostDomOnlyViewerWrapperPassPass();
diff --git a/llvm/include/llvm/Transforms/Scalar.h b/llvm/include/llvm/Transforms/Scalar.h
index 7e50e216fb7dcd2..da6a03a51f2acad 100644
--- a/llvm/include/llvm/Transforms/Scalar.h
+++ b/llvm/include/llvm/Transforms/Scalar.h
@@ -74,15 +74,6 @@ Pass *createLoopUnrollPass(int OptLevel = 2, bool OnlyWhenForced = false,
 //
 Pass *createLoopRotatePass(int MaxHeaderSize = -1, bool PrepareForLTO = false);
 
-//===----------------------------------------------------------------------===//
-//
-// DemoteRegisterToMemoryPass - This pass is used to demote registers to memory
-// references. In basically undoes the PromoteMemoryToRegister pass to make cfg
-// hacking easier.
-//
-FunctionPass *createDemoteRegisterToMemoryPass();
-extern char &DemoteRegisterToMemoryID;
-
 //===----------------------------------------------------------------------===//
 //
 // Reassociate - This pass reassociates commutative expressions in an order that
diff --git a/llvm/lib/Transforms/Scalar/Reg2Mem.cpp b/llvm/lib/Transforms/Scalar/Reg2Mem.cpp
index db7a1f24660c96c..9b2a713db642478 100644
--- a/llvm/lib/Transforms/Scalar/Reg2Mem.cpp
+++ b/llvm/lib/Transforms/Scalar/Reg2Mem.cpp
@@ -107,36 +107,3 @@ PreservedAnalyses RegToMemPass::run(Function &F, FunctionAnalysisManager &AM) {
   PA.preserve<LoopAnalysis>();
   return PA;
 }
-
-namespace {
-struct RegToMemLegacy : public FunctionPass {
-  static char ID; // Pass identification, replacement for typeid
-  RegToMemLegacy() : FunctionPass(ID) {
-    initializeRegToMemLegacyPass(*PassRegistry::getPassRegistry());
-  }
-
-  void getAnalysisUsage(AnalysisUsage &AU) const override {
-    AU.addRequiredID(BreakCriticalEdgesID);
-    AU.addPreservedID(BreakCriticalEdgesID);
-  }
-
-  bool runOnFunction(Function &F) override {
-    if (F.isDeclaration() || skipFunction(F))
-      return false;
-    return runPass(F);
-  }
-};
-} // namespace
-
-char RegToMemLegacy::ID = 0;
-INITIALIZE_PASS_BEGIN(RegToMemLegacy, "reg2mem",
-                      "Demote all values to stack slots", false, false)
-INITIALIZE_PASS_DEPENDENCY(BreakCriticalEdges)
-INITIALIZE_PASS_END(RegToMemLegacy, "reg2mem",
-                    "Demote all values to stack slots", false, false)
-
-// createDemoteRegisterToMemory - Provide an entry point to create this pass.
-char &llvm::DemoteRegisterToMemoryID = RegToMemLegacy::ID;
-FunctionPass *llvm::createDemoteRegisterToMemoryPass() {
-  return new RegToMemLegacy();
-}
diff --git a/llvm/lib/Transforms/Scalar/Scalar.cpp b/llvm/lib/Transforms/Scalar/Scalar.cpp
index d19f1c697d87852..20184d274867baf 100644
--- a/llvm/lib/Transforms/Scalar/Scalar.cpp
+++ b/llvm/lib/Transforms/Scalar/Scalar.cpp
@@ -39,7 +39,6 @@ void llvm::initializeScalarOpts(PassRegistry &Registry) {
   initializePartiallyInlineLibCallsLegacyPassPass(Registry);
   initializeReassociateLegacyPassPass(Registry);
   initializeRedundantDbgInstEliminationPass(Registry);
-  initializeRegToMemLegacyPass(Registry);
   initializeScalarizeMaskedMemIntrinLegacyPassPass(Registry);
   initializeSROALegacyPassPass(Registry);
   initializeCFGSimplifyPassPass(Registry);