If a function only reads memory, then we know that...
it only reads memory! The other change has no
functional effect, it just seems more logical to
go in order of decreasing knowledge.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@64463 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Analysis/AliasAnalysis.cpp b/lib/Analysis/AliasAnalysis.cpp
index 369f2f4..67b2faa 100644
--- a/lib/Analysis/AliasAnalysis.cpp
+++ b/lib/Analysis/AliasAnalysis.cpp
@@ -120,9 +120,13 @@
AliasAnalysis::ModRefBehavior
AliasAnalysis::getModRefBehavior(Function *F,
std::vector<PointerAccessInfo> *Info) {
- if (F && F->doesNotAccessMemory())
- // Can't do better than this.
- return DoesNotAccessMemory;
+ if (F) {
+ if (F->doesNotAccessMemory())
+ // Can't do better than this.
+ return DoesNotAccessMemory;
+ else if (F->onlyReadsMemory())
+ return OnlyReadsMemory;
+ }
return UnknownModRefBehavior;
}
@@ -130,10 +134,10 @@
AliasAnalysis::getModRefInfo(CallSite CS, Value *P, unsigned Size) {
ModRefResult Mask = ModRef;
ModRefBehavior MRB = getModRefBehavior(CS);
- if (MRB == OnlyReadsMemory)
- Mask = Ref;
- else if (MRB == DoesNotAccessMemory)
+ if (MRB == DoesNotAccessMemory)
return NoModRef;
+ else if (MRB == OnlyReadsMemory)
+ Mask = Ref;
else if (MRB == AliasAnalysis::AccessesArguments) {
bool doesAlias = false;
for (CallSite::arg_iterator AI = CS.arg_begin(), AE = CS.arg_end();
@@ -142,7 +146,7 @@
doesAlias = true;
break;
}
-
+
if (!doesAlias)
return NoModRef;
}