[ModRefInfo] Add must alias info to ModRefInfo.
Summary:
Add an additional bit to ModRefInfo, ModRefInfo::Must, to be cleared for known must aliases.
Shift existing Mod/Ref/ModRef values to include an additional most
significant bit. Update wrappers that modify ModRefInfo values to
reflect the change.
Notes:
* ModRefInfo::Must is almost entirely cleared in the AAResults methods, the remaining changes are trying to preserve it.
* Only some small changes to make custom AA passes set ModRefInfo::Must (BasicAA).
* GlobalsModRef already declares a bit, who's meaning overlaps with the most significant bit in ModRefInfo (MayReadAnyGlobal). No changes to shift the value of MayReadAnyGlobal (see AlignedMap). FunctionInfo.getModRef() ajusts most significant bit so correctness is preserved, but the Must info is lost.
* There are cases where the ModRefInfo::Must is not set, e.g. 2 calls that only read will return ModRefInfo::NoModRef, though they may read from exactly the same location.
Reviewers: dberlin, hfinkel, george.burgess.iv
Subscribers: llvm-commits, sanjoy
Differential Revision: https://reviews.llvm.org/D38862
llvm-svn: 321309
diff --git a/llvm/lib/Analysis/MemoryDependenceAnalysis.cpp b/llvm/lib/Analysis/MemoryDependenceAnalysis.cpp
index d5538f5..bb7bf96 100644
--- a/llvm/lib/Analysis/MemoryDependenceAnalysis.cpp
+++ b/llvm/lib/Analysis/MemoryDependenceAnalysis.cpp
@@ -647,6 +647,7 @@
// Ok, this store might clobber the query pointer. Check to see if it is
// a must alias: in this case, we want to return this as a def.
+ // FIXME: Use ModRefInfo::Must bit from getModRefInfo call above.
MemoryLocation StoreLoc = MemoryLocation::get(SI);
// If we found a pointer, check if it could be the same as our pointer.
@@ -690,7 +691,7 @@
// If necessary, perform additional analysis.
if (isModAndRefSet(MR))
MR = AA.callCapturesBefore(Inst, MemLoc, &DT, &OBB);
- switch (MR) {
+ switch (clearMust(MR)) {
case ModRefInfo::NoModRef:
// If the call has no effect on the queried pointer, just ignore it.
continue;