Finish making AliasAnalysis aware of the fact that most atomic intrinsics only dereference their arguments, and enhance
BasicAA to make use of this fact when computing ModRef info.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@63718 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Analysis/BasicAliasAnalysis.cpp b/lib/Analysis/BasicAliasAnalysis.cpp
index ccbe338..317e9d9 100644
--- a/lib/Analysis/BasicAliasAnalysis.cpp
+++ b/lib/Analysis/BasicAliasAnalysis.cpp
@@ -256,6 +256,22 @@
//
AliasAnalysis::ModRefResult
BasicAliasAnalysis::getModRefInfo(CallSite CS, Value *P, unsigned Size) {
+ // If the function only accesses its arguments, it suffices to check that
+ // P does not alias any of those arguments.
+ if (AliasAnalysis::getModRefBehavior(CS, 0) ==
+ AliasAnalysis::AccessesArguments) {
+ bool doesAlias = false;
+ for (CallSite::arg_iterator AI = CS.arg_begin(), AE = CS.arg_end();
+ AI != AE; ++AI)
+ if (alias(*AI, ~0U, P, Size) != NoAlias) {
+ doesAlias = true;
+ break;
+ }
+
+ if (!doesAlias)
+ return NoModRef;
+ }
+
if (!isa<Constant>(P)) {
const Value *Object = P->getUnderlyingObject();