AliasAnalysis: unify getModRefInfo(I, CS) semantics with other overloads

This subtle change to getModRefInfo(Instruction, ImmutableCallSite) is to
ensure that the semantics are equal to that of getModRefInfo(CS1, CS2) when
the Instruction is a call-site.

This is now more in line with getModRefInfo generally: it returns Mod when
I modifies a memory location that is accessed (read or written) by CS and
Ref when I reads a memory location that is written by CS.

From a grep of the code, the only uses of this particular getModRefInfo
overload are in MemorySSA and MemCpyOptimizer, and they only care about
where the result is MR_NoModRef or not. Therefore, this change should have
no visible effect.

Separated out from D17279 upon request.

llvm-svn: 275065

1 files changed, 1 insertions, 1 deletions

diff --git a/llvm/lib/Analysis/AliasAnalysis.cpp b/llvm/lib/Analysis/AliasAnalysis.cpp
index 643e9da1db1..ab5f814fb39 100644
--- a/llvm/lib/Analysis/AliasAnalysis.cpp
+++ b/llvm/lib/Analysis/AliasAnalysis.cpp
@@ -110,7 +110,7 @@ ModRefInfo AAResults::getModRefInfo(Instruction *I, ImmutableCallSite Call) {
   // We may have two calls
   if (auto CS = ImmutableCallSite(I)) {
     // Check if the two calls modify the same memory
-    return getModRefInfo(Call, CS);
+    return getModRefInfo(CS, Call);
   } else {
     // Otherwise, check if the call modifies or references the
     // location this memory access defines.  The best we can say