From ac07270828e6d34acbae9584789e8709a18b258a Mon Sep 17 00:00:00 2001
From: Chandler Carruth <chandlerc@gmail.com>
Date: Fri, 19 Feb 2016 03:12:14 +0000
Subject: [PATCH] [AA] Preserve the AA results wrapper pass as well as BasicAA
 in a few more places to prevent gratuitous re-"runs" of these passes.

The passes themselves don't do any work when run, but we keep spending
time scheduling and running these needlessly when we really don't need
to do so.

This is the first patch towards fixing the really horrible loop pass
pipeline fragmentation pointed out by Sanjoy in PR24804.

llvm-svn: 261302
---
 llvm/lib/Transforms/InstCombine/InstructionCombining.cpp | 4 ++++
 llvm/lib/Transforms/Utils/LCSSA.cpp                      | 2 ++
 2 files changed, 6 insertions(+)

diff --git a/llvm/lib/Transforms/InstCombine/InstructionCombining.cpp b/llvm/lib/Transforms/InstCombine/InstructionCombining.cpp
index d75913f9c289..1b95e9334c12 100644
--- a/llvm/lib/Transforms/InstCombine/InstructionCombining.cpp
+++ b/llvm/lib/Transforms/InstCombine/InstructionCombining.cpp
@@ -39,7 +39,9 @@
 #include "llvm/ADT/SmallPtrSet.h"
 #include "llvm/ADT/Statistic.h"
 #include "llvm/ADT/StringSwitch.h"
+#include "llvm/Analysis/AliasAnalysis.h"
 #include "llvm/Analysis/AssumptionCache.h"
+#include "llvm/Analysis/BasicAliasAnalysis.h"
 #include "llvm/Analysis/CFG.h"
 #include "llvm/Analysis/ConstantFolding.h"
 #include "llvm/Analysis/EHPersonalities.h"
@@ -3103,6 +3105,8 @@ void InstructionCombiningPass::getAnalysisUsage(AnalysisUsage &AU) const {
   AU.addRequired<TargetLibraryInfoWrapperPass>();
   AU.addRequired<DominatorTreeWrapperPass>();
   AU.addPreserved<DominatorTreeWrapperPass>();
+  AU.addPreserved<AAResultsWrapperPass>();
+  AU.addPreserved<BasicAAWrapperPass>();
   AU.addPreserved<GlobalsAAWrapperPass>();
 }
 
diff --git a/llvm/lib/Transforms/Utils/LCSSA.cpp b/llvm/lib/Transforms/Utils/LCSSA.cpp
index b4b2e148dfbb..0abb1f440d32 100644
--- a/llvm/lib/Transforms/Utils/LCSSA.cpp
+++ b/llvm/lib/Transforms/Utils/LCSSA.cpp
@@ -31,6 +31,7 @@
 #include "llvm/ADT/STLExtras.h"
 #include "llvm/ADT/Statistic.h"
 #include "llvm/Analysis/AliasAnalysis.h"
+#include "llvm/Analysis/BasicAliasAnalysis.h"
 #include "llvm/Analysis/GlobalsModRef.h"
 #include "llvm/Analysis/LoopPass.h"
 #include "llvm/Analysis/ScalarEvolution.h"
@@ -298,6 +299,7 @@ struct LCSSA : public FunctionPass {
     AU.addRequired<LoopInfoWrapperPass>();
     AU.addPreservedID(LoopSimplifyID);
     AU.addPreserved<AAResultsWrapperPass>();
+    AU.addPreserved<BasicAAWrapperPass>();
     AU.addPreserved<GlobalsAAWrapperPass>();
     AU.addPreserved<ScalarEvolutionWrapperPass>();
     AU.addPreserved<SCEVAAWrapperPass>();