//
// 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.
//
#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"
#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
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,
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) {