LAA: handle 0 return from getPtrStride correctly (#124539)

getPtrStride returns 0 when the PtrScev is loop-invariant, and this is
not an erroneous value: it returns std::nullopt to communicate that it
was not able to find a valid pointer stride. In analyzeLoop, we call
getPtrStride with a value_or(0) conflating the zero return value with
std::nullopt. Fix this, handling loop-invariant loads correctly.

1 files changed, 2 insertions, 2 deletions

diff --git a/llvm/lib/Analysis/LoopAccessAnalysis.cpp b/llvm/lib/Analysis/LoopAccessAnalysis.cpp
index 11e0a22..697b404 100644
--- a/llvm/lib/Analysis/LoopAccessAnalysis.cpp
+++ b/llvm/lib/Analysis/LoopAccessAnalysis.cpp
@@ -1438,7 +1438,7 @@ llvm::getPtrStride(PredicatedScalarEvolution &PSE, Type *AccessTy, Value *Ptr,
                    bool Assume, bool ShouldCheckWrap) {
   const SCEV *PtrScev = replaceSymbolicStrideSCEV(PSE, StridesMap, Ptr);
   if (PSE.getSE()->isLoopInvariant(PtrScev, Lp))
-    return {0};
+    return 0;
 
   Type *Ty = Ptr->getType();
   assert(Ty->isPointerTy() && "Unexpected non-ptr");
@@ -2593,7 +2593,7 @@ bool LoopAccessInfo::analyzeLoop(AAResults *AA, const LoopInfo *LI,
     bool IsReadOnlyPtr = false;
     Type *AccessTy = getLoadStoreType(LD);
     if (Seen.insert({Ptr, AccessTy}).second ||
-        !getPtrStride(*PSE, LD->getType(), Ptr, TheLoop, SymbolicStrides).value_or(0)) {
+        !getPtrStride(*PSE, AccessTy, Ptr, TheLoop, SymbolicStrides)) {
       ++NumReads;
       IsReadOnlyPtr = true;
     }