X-Git-Url: http://demsky.eecs.uci.edu/git/?a=blobdiff_plain;f=lib%2FAnalysis%2FTypeBasedAliasAnalysis.cpp;h=0faf1398ec76609775e1a05d91252f0e964d5d4b;hb=618c1dbd293d15ee19f61b1156ab8086ad28311a;hp=044a93f8661a82d220e2179b45c15fdbf668c7d0;hpb=a25e5dbcc2371352386a01e3c1b8e76dd890272b;p=oota-llvm.git

diff --git a/lib/Analysis/TypeBasedAliasAnalysis.cpp b/lib/Analysis/TypeBasedAliasAnalysis.cpp
index 044a93f8661..0faf1398ec7 100644
--- a/lib/Analysis/TypeBasedAliasAnalysis.cpp
+++ b/lib/Analysis/TypeBasedAliasAnalysis.cpp
@@ -31,7 +31,7 @@
 //
 // The second field identifies the type's parent node in the tree, or
 // is null or omitted for a root node. A type is considered to alias
-// all of its decendents and all of its ancestors in the tree. Also,
+// all of its descendants and all of its ancestors in the tree. Also,
 // a type is considered to alias all types in other trees, so that
 // bitcode produced from multiple front-ends is handled conservatively.
 //
@@ -59,6 +59,7 @@
 
 #include "llvm/Analysis/AliasAnalysis.h"
 #include "llvm/Analysis/Passes.h"
+#include "llvm/Constants.h"
 #include "llvm/LLVMContext.h"
 #include "llvm/Module.h"
 #include "llvm/Metadata.h"
@@ -66,8 +67,10 @@
 #include "llvm/Support/CommandLine.h"
 using namespace llvm;
 
-// For testing purposes, enable TBAA only via a special option.
-static cl::opt<bool> EnableTBAA("enable-tbaa");
+// A handy option for disabling TBAA functionality. The same effect can also be
+// achieved by stripping the !tbaa tags from IR, but this option is sometimes
+// more convenient.
+static cl::opt<bool> EnableTBAA("enable-tbaa", cl::init(true));
 
 namespace {
   /// TBAANode - This is a simple wrapper around an MDNode which provides a
@@ -139,6 +142,8 @@ 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 +246,28 @@ 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 ModRefBehavior(AliasAnalysis::getModRefBehavior(CS) & Min);
+}
+
+AliasAnalysis::ModRefBehavior
+TypeBasedAliasAnalysis::getModRefBehavior(const Function *F) {
+  // Functions don't have metadata. Just chain to the next implementation.
+  return AliasAnalysis::getModRefBehavior(F);
+}
+
 AliasAnalysis::ModRefResult
 TypeBasedAliasAnalysis::getModRefInfo(ImmutableCallSite CS,
                                       const Location &Loc) {