[llvm] [LAA] Allow vectorizing `A[NonZeroNonConstantStride*I] += 1` (PR #186262)

[Ramkumar Ramachandra via llvm-commits]

================
@@ -1691,7 +1693,23 @@ std::optional<int64_t> llvm::getPtrStride(
   LLVM_DEBUG(
       dbgs() << "LAA: Bad stride - Pointer may wrap in the address space "
              << *Ptr << " SCEV: " << *AR << "\n");
-  return std::nullopt;
+  return nullptr;
+}
+
+/// Check whether the access through \p Ptr has a constant stride.
+std::optional<int64_t> llvm::getPtrStride(
+    PredicatedScalarEvolution &PSE, Type *AccessTy, Value *Ptr, const Loop *Lp,
+    const DominatorTree &DT, const DenseMap<Value *, const SCEV *> &StridesMap,
+    bool ShouldCheckWrap, SmallVectorImpl<const SCEVPredicate *> *Predicates) {
+  const SCEV *StrideScev = getPtrStrideScev(
+      PSE, AccessTy, Ptr, Lp, DT, StridesMap, ShouldCheckWrap, Predicates);
+  if (!StrideScev)
+    return std::nullopt;
+  const APInt *APStride = nullptr;
----------------
artagnon wrote:

```suggestion
  const APInt *APStride;
```

Initialized in match?

https://github.com/llvm/llvm-project/pull/186262