From a8598bec287108d0359880d33955759dc90cd5a1 Mon Sep 17 00:00:00 2001
From: Dan Gohman <gohman@apple.com>
Date: Mon, 8 Nov 2010 17:10:22 +0000
Subject: [PATCH] Implement getModRefBehavior for TypeBasedAliasAnalysis.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@118416 91177308-0d34-0410-b5e6-96231b3b80d8
---
 lib/Analysis/TypeBasedAliasAnalysis.cpp | 23 +++++++++++++++++++++++
 1 file changed, 23 insertions(+)

diff --git a/lib/Analysis/TypeBasedAliasAnalysis.cpp b/lib/Analysis/TypeBasedAliasAnalysis.cpp
index 044a93f8661..16ff64e4cfb 100644
--- a/lib/Analysis/TypeBasedAliasAnalysis.cpp
+++ b/lib/Analysis/TypeBasedAliasAnalysis.cpp
@@ -139,6 +139,8 @@ namespace {
     virtual void getAnalysisUsage(AnalysisUsage &AU) const;
     virtual AliasResult alias(const Location &LocA, const Location &LocB);
     virtual bool pointsToConstantMemory(const Location &Loc, bool OrLocal);
+    virtual ModRefBehavior getModRefBehavior(ImmutableCallSite CS);
+    virtual ModRefBehavior getModRefBehavior(const Function *F);
     virtual ModRefResult getModRefInfo(ImmutableCallSite CS,
                                        const Location &Loc);
     virtual ModRefResult getModRefInfo(ImmutableCallSite CS1,
@@ -241,6 +243,27 @@ bool TypeBasedAliasAnalysis::pointsToConstantMemory(const Location &Loc,
   return AliasAnalysis::pointsToConstantMemory(Loc, OrLocal);
 }
 
+AliasAnalysis::ModRefBehavior
+TypeBasedAliasAnalysis::getModRefBehavior(ImmutableCallSite CS) {
+  if (!EnableTBAA)
+    return AliasAnalysis::getModRefBehavior(CS);
+
+  ModRefBehavior Min = UnknownModRefBehavior;
+
+  // If this is an "immutable" type, we can assume the call doesn't write
+  // to memory.
+  if (const MDNode *M = CS.getInstruction()->getMetadata(LLVMContext::MD_tbaa))
+    if (TBAANode(M).TypeIsImmutable())
+      Min = OnlyReadsMemory;
+
+  return std::min(AliasAnalysis::getModRefBehavior(CS), Min);
+}
+
+AliasAnalysis::ModRefBehavior
+TypeBasedAliasAnalysis::getModRefBehavior(const Function *F) {
+  return AliasAnalysis::getModRefBehavior(F);
+}
+
 AliasAnalysis::ModRefResult
 TypeBasedAliasAnalysis::getModRefInfo(ImmutableCallSite CS,
                                       const Location &Loc) {