From 4fd1f266b1e984e06da164beb7513589a87e983a Mon Sep 17 00:00:00 2001
From: Alina Sbirlea <asbirlea@google.com>
Date: Tue, 23 Apr 2019 20:59:44 +0000
Subject: [MemorySSA] LCSSA preserves MemorySSA.

Summary:
Enabling MemorySSA in the old pass manager leads to MemorySSA being run
twice due to the fact that LCSSA and LoopSimplify do not preserve
MemorySSA. This is the first step to address that: target LCSSA.

LCSSA does not make any changes that invalidate MemorySSA, so it
preserves it by design. It must preserve AA as well, for this to hold.

After this patch, MemorySSA is still run twice in the old pass manager.
Step two follows: target LoopSimplify.

Subscribers: mehdi_amini, jlebar, Prazek, llvm-commits, george.burgess.iv, chandlerc

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D60832

llvm-svn: 359032
---
 llvm/lib/Transforms/Utils/LCSSA.cpp | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

(limited to 'llvm/lib/Transforms')

diff --git a/llvm/lib/Transforms/Utils/LCSSA.cpp b/llvm/lib/Transforms/Utils/LCSSA.cpp
index 5ddb7381a56..29e7c5260f4 100644
--- a/llvm/lib/Transforms/Utils/LCSSA.cpp
+++ b/llvm/lib/Transforms/Utils/LCSSA.cpp
@@ -34,9 +34,9 @@
 #include "llvm/Analysis/BranchProbabilityInfo.h"
 #include "llvm/Analysis/GlobalsModRef.h"
 #include "llvm/Analysis/LoopPass.h"
+#include "llvm/Analysis/MemorySSA.h"
 #include "llvm/Analysis/ScalarEvolution.h"
 #include "llvm/Analysis/ScalarEvolutionAliasAnalysis.h"
-#include "llvm/Transforms/Utils/Local.h"
 #include "llvm/IR/Constants.h"
 #include "llvm/IR/Dominators.h"
 #include "llvm/IR/Function.h"
@@ -45,6 +45,7 @@
 #include "llvm/IR/PredIteratorCache.h"
 #include "llvm/Pass.h"
 #include "llvm/Transforms/Utils.h"
+#include "llvm/Transforms/Utils/Local.h"
 #include "llvm/Transforms/Utils/LoopUtils.h"
 #include "llvm/Transforms/Utils/SSAUpdater.h"
 using namespace llvm;
@@ -444,6 +445,7 @@ struct LCSSAWrapperPass : public FunctionPass {
     AU.addPreserved<ScalarEvolutionWrapperPass>();
     AU.addPreserved<SCEVAAWrapperPass>();
     AU.addPreserved<BranchProbabilityInfoWrapperPass>();
+    AU.addPreserved<MemorySSAWrapperPass>();
 
     // This is needed to perform LCSSA verification inside LPPassManager
     AU.addRequired<LCSSAVerificationPass>();
@@ -490,5 +492,6 @@ PreservedAnalyses LCSSAPass::run(Function &F, FunctionAnalysisManager &AM) {
   // BPI maps terminators to probabilities, since we don't modify the CFG, no
   // updates are needed to preserve it.
   PA.preserve<BranchProbabilityAnalysis>();
+  PA.preserve<MemorySSAAnalysis>();
   return PA;
 }
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