Fix LoopAccessAnalysis when potentially nullptr check are involved
Summary:
GetUnderlyingObjects() can return "null" among its list of objects,
we don't want to deduce that two pointers can point to the same
memory in this case, so filter it out.
Reviewers: anemet
Subscribers: dexonsmith, llvm-commits
From: Mehdi Amini <mehdi.amini@apple.com>
llvm-svn: 252149
diff --git a/llvm/lib/Analysis/LoopAccessAnalysis.cpp b/llvm/lib/Analysis/LoopAccessAnalysis.cpp
index 58a7d08..49b2807 100644
--- a/llvm/lib/Analysis/LoopAccessAnalysis.cpp
+++ b/llvm/lib/Analysis/LoopAccessAnalysis.cpp
@@ -268,7 +268,7 @@
// ShouldRetryWithRuntimeCheck is set, and therefore UseDependencies
// is also false. In this case we will use the fallback path and create
// separate checking groups for all pointers.
-
+
// If we don't have the dependency partitions, construct a new
// checking pointer group for each pointer. This is also required
// for correctness, because in this case we can have checking between
@@ -743,6 +743,11 @@
GetUnderlyingObjects(Ptr, TempObjects, DL, LI);
DEBUG(dbgs() << "Underlying objects for pointer " << *Ptr << "\n");
for (Value *UnderlyingObj : TempObjects) {
+ // nullptr never alias, don't join sets for pointer that have "null"
+ // in their UnderlyingObjects list.
+ if (isa<ConstantPointerNull>(UnderlyingObj))
+ continue;
+
UnderlyingObjToAccessMap::iterator Prev =
ObjToLastAccess.find(UnderlyingObj);
if (Prev != ObjToLastAccess.end())