[llvm] [LAA] Make Ptr argument optional in isNoWrap. (PR #127410)

[Florian Hahn via llvm-commits]

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@@ -839,29 +848,29 @@ getStrideFromAddRec(const SCEVAddRecExpr *AR, const Loop *Lp, Type *AccessTy,
 static bool isNoWrapGEP(Value *Ptr, PredicatedScalarEvolution &PSE,
                         const Loop *L);
 
-/// Check whether \p AR is a non-wrapping AddRec, or if \p Ptr is a non-wrapping
-/// GEP.
+/// Check whether a pointer address cannot wrap. If \p Ptr is not nullptr, use
+/// informating from the IR pointer value to determine no-wrap.
 static bool isNoWrap(PredicatedScalarEvolution &PSE, const SCEVAddRecExpr *AR,
                      Value *Ptr, Type *AccessTy, const Loop *L, bool Assume,
                      std::optional<int64_t> Stride = std::nullopt) {
   // FIXME: This should probably only return true for NUW.
   if (AR->getNoWrapFlags(SCEV::NoWrapMask))
     return true;
 
-  if (PSE.hasNoOverflow(Ptr, SCEVWrapPredicate::IncrementNUSW))
+  if (Ptr && PSE.hasNoOverflow(Ptr, SCEVWrapPredicate::IncrementNUSW))
     return true;
 
   // The address calculation must not wrap. Otherwise, a dependence could be
   // inverted.
-  if (isNoWrapGEP(Ptr, PSE, L))
+  if (Ptr && isNoWrapGEP(Ptr, PSE, L))
     return true;
 
   // An nusw getelementptr that is an AddRec cannot wrap. If it would wrap,
   // the distance between the previously accessed location and the wrapped
   // location will be larger than half the pointer index type space. In that
   // case, the GEP would be  poison and any memory access dependent on it would
   // be immediate UB when executed.
-  if (auto *GEP = dyn_cast<GetElementPtrInst>(Ptr);
+  if (auto *GEP = dyn_cast_if_present<GetElementPtrInst>(Ptr);
       GEP && GEP->hasNoUnsignedSignedWrap())
     return true;
 
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fhahn wrote:

The stride check could be moved to the top and then we could have an early return false if `Ptr` is nullptr, but most of the checks above are simpler/cheaper than the stride check

https://github.com/llvm/llvm-project/pull/127410