[Loads] Respect UseDerefAtPointSemantics in isDerefAndAlignedPointer. (#123196)

If a pointer gets freed, it may not be dereferenceable any longer, even
though there is a dominating dereferenceable assumption. As first step,
only consider assumptions if the pointer value cannot be freed if
UseDerefAtPointSemantics is used.

PR: https://github.com/llvm/llvm-project/pull/123196

1 files changed, 3 insertions, 1 deletions

diff --git a/llvm/lib/Analysis/Loads.cpp b/llvm/lib/Analysis/Loads.cpp
index 7bbd469..11ccfa3 100644
--- a/llvm/lib/Analysis/Loads.cpp
+++ b/llvm/lib/Analysis/Loads.cpp
@@ -25,6 +25,8 @@
 
 using namespace llvm;
 
+extern cl::opt<bool> UseDerefAtPointSemantics;
+
 static bool isAligned(const Value *Base, Align Alignment,
                       const DataLayout &DL) {
   return Base->getPointerAlignment(DL) >= Alignment;
@@ -168,7 +170,7 @@ static bool isDereferenceableAndAlignedPointer(
                                               Size, DL, CtxI, AC, DT, TLI,
                                               Visited, MaxDepth);
 
-  if (CtxI) {
+  if (CtxI && (!UseDerefAtPointSemantics || !V->canBeFreed())) {
     /// Look through assumes to see if both dereferencability and alignment can
     /// be proven by an assume if needed.
     RetainedKnowledge AlignRK;