Teach basicaa about memcpy/memmove/memset. The length argument can be used to
improve alias results if constant, and the source pointer can't be modified.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@84175 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Analysis/BasicAliasAnalysis.cpp b/lib/Analysis/BasicAliasAnalysis.cpp
index a030666..c5be616 100644
--- a/lib/Analysis/BasicAliasAnalysis.cpp
+++ b/lib/Analysis/BasicAliasAnalysis.cpp
@@ -310,6 +310,28 @@
if (IntrinsicInst *II = dyn_cast<IntrinsicInst>(CS.getInstruction())) {
switch (II->getIntrinsicID()) {
default: break;
+ case Intrinsic::memcpy:
+ case Intrinsic::memmove: {
+ unsigned Len = ~0U;
+ if (ConstantInt *LenCI = dyn_cast<ConstantInt>(II->getOperand(3)))
+ Len = LenCI->getZExtValue();
+ Value *Dest = II->getOperand(1);
+ Value *Src = II->getOperand(2);
+ if (alias(Dest, Len, P, Size) == NoAlias) {
+ if (alias(Src, Len, P, Size) == NoAlias)
+ return NoModRef;
+ return Ref;
+ }
+ }
+ break;
+ case Intrinsic::memset:
+ if (ConstantInt *LenCI = dyn_cast<ConstantInt>(II->getOperand(3))) {
+ unsigned Len = LenCI->getZExtValue();
+ Value *Dest = II->getOperand(1);
+ if (alias(Dest, Len, P, Size) == NoAlias)
+ return NoModRef;
+ }
+ break;
case Intrinsic::atomic_cmp_swap:
case Intrinsic::atomic_swap:
case Intrinsic::atomic_load_add: