[MemorySSA] Remove unnecessary MSSA dependencies

[nikic]

Summary

LoopLoadElimination, LoopVersioning and LoopVectorize currently fetch MemorySSA when construction LoopAccessAnalysis. However, LoopAccessAnalysis does not actually use MemorySSA and we can pass nullptr instead.

Together with D108073 this makes for a free compile-time improvement: https://llvm-compile-time-tracker.com/compare.php?from=371f6ec0254dbdb461323a46515d167c6fe40359&to=59e5e3b85ed5a01c92b9d76a65327eae98953a3d&stat=instructions

[asbirlea]

LGTM!

clang/test/CodeGen/thinlto-distributed-newpm.ll

 ; CHECK-O: Running pass: LoopRotatePass on Loop at depth 1 containing: %b
 ; CHECK-O: Running pass: LoopDistributePass on main
 ; CHECK-O: Running pass: InjectTLIMappings on main
 ; CHECK-O: Running pass: LoopVectorizePass on main
 ; CHECK-O: Running analysis: BlockFrequencyAnalysis on main
 ; CHECK-O: Running analysis: BranchProbabilityAnalysis on main
 ; CHECK-O: Running analysis: PostDominatorTreeAnalysis on main
 ; CHECK-O: Running analysis: DemandedBitsAnalysis on main
-; CHECK-O: Running analysis: MemorySSAAnalysis on main
 ; CHECK-O: Running pass: LoopLoadEliminationPass on main
 ; CHECK-O: Running pass: InstCombinePass on main
 ; CHECK-O: Running pass: SimplifyCFGPass on main
 ; CHECK-O: Running pass: SLPVectorizerPass on main
 ; CHECK-O: Running pass: VectorCombinePass on main
 ; CHECK-O: Running pass: InstCombinePass on main
 ; CHECK-O: Running pass: LoopUnrollPass on main
 ; CHECK-O: Running pass: WarnMissedTransformationsPass on main

llvm/lib/Transforms/Scalar/LoopLoadElimination.cpp

 #include "llvm/ADT/Statistic.h"
 #include "llvm/Analysis/AssumptionCache.h"
 #include "llvm/Analysis/BlockFrequencyInfo.h"
 #include "llvm/Analysis/GlobalsModRef.h"
 #include "llvm/Analysis/LazyBlockFrequencyInfo.h"
 #include "llvm/Analysis/LoopAccessAnalysis.h"
 #include "llvm/Analysis/LoopAnalysisManager.h"
 #include "llvm/Analysis/LoopInfo.h"
-#include "llvm/Analysis/MemorySSA.h"
 #include "llvm/Analysis/ProfileSummaryInfo.h"
 #include "llvm/Analysis/ScalarEvolution.h"
 #include "llvm/Analysis/ScalarEvolutionExpressions.h"
 #include "llvm/Analysis/TargetLibraryInfo.h"
 #include "llvm/Analysis/TargetTransformInfo.h"
 #include "llvm/IR/DataLayout.h"
 #include "llvm/IR/Dominators.h"
 #include "llvm/IR/Instructions.h"
PreservedAnalyses LoopLoadEliminationPass::run(Function &F,
   auto &DT = AM.getResult<DominatorTreeAnalysis>(F);
   auto &TLI = AM.getResult<TargetLibraryAnalysis>(F);
   auto &AA = AM.getResult<AAManager>(F);
   auto &AC = AM.getResult<AssumptionAnalysis>(F);
   auto &MAMProxy = AM.getResult<ModuleAnalysisManagerFunctionProxy>(F);
   auto *PSI = MAMProxy.getCachedResult<ProfileSummaryAnalysis>(*F.getParent());
   auto *BFI = (PSI && PSI->hasProfileSummary()) ?
       &AM.getResult<BlockFrequencyAnalysis>(F) : nullptr;
-  MemorySSA *MSSA = EnableMSSALoopDependency
-                        ? &AM.getResult<MemorySSAAnalysis>(F).getMSSA()
-                        : nullptr;
 
   auto &LAM = AM.getResult<LoopAnalysisManagerFunctionProxy>(F).getManager();
   bool Changed = eliminateLoadsAcrossLoops(
       F, LI, DT, BFI, PSI, &SE, &AC, [&](Loop &L) -> const LoopAccessInfo & {
         LoopStandardAnalysisResults AR = {AA,  AC,  DT,      LI,  SE,
-                                          TLI, TTI, nullptr, MSSA};
+                                          TLI, TTI, nullptr, nullptr};
         return LAM.getResult<LoopAccessAnalysis>(L, AR);
       });
 
   if (!Changed)
     return PreservedAnalyses::all();
 
   PreservedAnalyses PA;
   return PA;
 }

llvm/lib/Transforms/Utils/LoopVersioning.cpp

 //===- LoopVersioning.cpp - Utility to version a loop ---------------------===//
 //
 // 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
 //
 //===----------------------------------------------------------------------===//
 //
 // This file defines a utility class to perform loop versioning.  The versioned
 // loop speculates that otherwise may-aliasing memory accesses don't overlap and
 // emits checks to prove this.
 //
 //===----------------------------------------------------------------------===//
 
 #include "llvm/Transforms/Utils/LoopVersioning.h"
 #include "llvm/ADT/ArrayRef.h"
+#include "llvm/Analysis/AliasAnalysis.h"
 #include "llvm/Analysis/LoopAccessAnalysis.h"
 #include "llvm/Analysis/LoopInfo.h"
-#include "llvm/Analysis/MemorySSA.h"
 #include "llvm/Analysis/ScalarEvolution.h"
 #include "llvm/Analysis/TargetLibraryInfo.h"
 #include "llvm/IR/Dominators.h"
 #include "llvm/IR/MDBuilder.h"
 #include "llvm/IR/PassManager.h"
 #include "llvm/InitializePasses.h"
 #include "llvm/Support/CommandLine.h"
 #include "llvm/Transforms/Utils/BasicBlockUtils.h"
PreservedAnalyses LoopVersioningPass::run(Function &F,
                                           FunctionAnalysisManager &AM) {
   auto &SE = AM.getResult<ScalarEvolutionAnalysis>(F);
   auto &LI = AM.getResult<LoopAnalysis>(F);
   auto &TTI = AM.getResult<TargetIRAnalysis>(F);
   auto &DT = AM.getResult<DominatorTreeAnalysis>(F);
   auto &TLI = AM.getResult<TargetLibraryAnalysis>(F);
   auto &AA = AM.getResult<AAManager>(F);
   auto &AC = AM.getResult<AssumptionAnalysis>(F);
-  MemorySSA *MSSA = EnableMSSALoopDependency
-                        ? &AM.getResult<MemorySSAAnalysis>(F).getMSSA()
-                        : nullptr;
 
   auto &LAM = AM.getResult<LoopAnalysisManagerFunctionProxy>(F).getManager();
   auto GetLAA = [&](Loop &L) -> const LoopAccessInfo & {
     LoopStandardAnalysisResults AR = {AA,  AC,  DT,      LI,  SE,
-                                      TLI, TTI, nullptr, MSSA};
+                                      TLI, TTI, nullptr, nullptr};
     return LAM.getResult<LoopAccessAnalysis>(L, AR);
   };
 
   if (runImpl(&LI, GetLAA, &DT, &SE))
     return PreservedAnalyses::none();
   return PreservedAnalyses::all();
 }
 } // namespace llvm

llvm/lib/Transforms/Vectorize/LoopVectorize.cpp

 #include "llvm/Analysis/CFG.h"
 #include "llvm/Analysis/CodeMetrics.h"
 #include "llvm/Analysis/DemandedBits.h"
 #include "llvm/Analysis/GlobalsModRef.h"
 #include "llvm/Analysis/LoopAccessAnalysis.h"
 #include "llvm/Analysis/LoopAnalysisManager.h"
 #include "llvm/Analysis/LoopInfo.h"
 #include "llvm/Analysis/LoopIterator.h"
-#include "llvm/Analysis/MemorySSA.h"
 #include "llvm/Analysis/OptimizationRemarkEmitter.h"
 #include "llvm/Analysis/ProfileSummaryInfo.h"
 #include "llvm/Analysis/ScalarEvolution.h"
 #include "llvm/Analysis/ScalarEvolutionExpressions.h"
 #include "llvm/Analysis/TargetLibraryInfo.h"
 #include "llvm/Analysis/TargetTransformInfo.h"
 #include "llvm/Analysis/VectorUtils.h"
 #include "llvm/IR/Attributes.h"
PreservedAnalyses LoopVectorizePass::run(Function &F,
     auto &TTI = AM.getResult<TargetIRAnalysis>(F);
     auto &DT = AM.getResult<DominatorTreeAnalysis>(F);
     auto &BFI = AM.getResult<BlockFrequencyAnalysis>(F);
     auto &TLI = AM.getResult<TargetLibraryAnalysis>(F);
     auto &AA = AM.getResult<AAManager>(F);
     auto &AC = AM.getResult<AssumptionAnalysis>(F);
     auto &DB = AM.getResult<DemandedBitsAnalysis>(F);
     auto &ORE = AM.getResult<OptimizationRemarkEmitterAnalysis>(F);
-    MemorySSA *MSSA = EnableMSSALoopDependency
-                          ? &AM.getResult<MemorySSAAnalysis>(F).getMSSA()
-                          : nullptr;
 
     auto &LAM = AM.getResult<LoopAnalysisManagerFunctionProxy>(F).getManager();
     std::function<const LoopAccessInfo &(Loop &)> GetLAA =
         [&](Loop &L) -> const LoopAccessInfo & {
       LoopStandardAnalysisResults AR = {AA,  AC,  DT,      LI,  SE,
-                                        TLI, TTI, nullptr, MSSA};
+                                        TLI, TTI, nullptr, nullptr};
       return LAM.getResult<LoopAccessAnalysis>(L, AR);
     };
     auto &MAMProxy = AM.getResult<ModuleAnalysisManagerFunctionProxy>(F);
     ProfileSummaryInfo *PSI =
         MAMProxy.getCachedResult<ProfileSummaryAnalysis>(*F.getParent());
     LoopVectorizeResult Result =
         runImpl(F, SE, LI, TTI, DT, BFI, &TLI, DB, AA, AC, GetLAA, ORE, PSI);
     if (!Result.MadeAnyChange)

llvm/test/Transforms/LoopVectorize/novect-lcssa-cfg-invalidation.ll

 ; RUN: opt -S -passes="loop-vectorize,jump-threading" -debug-pass-manager < %s 2>&1 | FileCheck %s
 
 target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
 
 ; Checks what analyses are invalidated after Loop Vectorization when no actual
 ; vectorization happens, and the only change LV makes is LCSSA formation.
 
 define i32 @novect(i32* %p) {
 
 ; CHECK:           Running pass: LoopVectorizePass on novect
 ; CHECK:           Clearing all analysis results for: <possibly invalidated loop>
 ; CHECK:           Invalidating analysis: ScalarEvolutionAnalysis on novect
 ; CHECK-NOT:       Invalidating analysis: BranchProbabilityAnalysis on novect
 ; CHECK-NOT:       Invalidating analysis: BlockFrequencyAnalysis on novect
 ; CHECK:           Invalidating analysis: DemandedBitsAnalysis on novect
-; CHECK:           Invalidating analysis: MemorySSAAnalysis on novect
 ; CHECK:           Running pass: JumpThreadingPass on novect
 
 ; CHECK:           entry:
 ; CHECK:             br label %middle
 ; CHECK:           middle:
 ; CHECK:             %iv = phi i32 [ 0, %entry ], [ %iv.next, %middle ]
 ; CHECK:             %x = load volatile i32, i32* %p
 ; CHECK:             %iv.next = add i32 %iv, 1