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

[Florian Hahn via llvm-commits]

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@@ -1144,13 +1153,10 @@ bool AccessAnalysis::createCheckForAccess(RuntimePointerChecking &RtCheck,
 
     // When we run after a failing dependency check we have to make sure
     // we don't have wrapping pointers.
-    if (ShouldCheckWrap) {
-      // Skip wrap checking when translating pointers.
-      if (TranslatedPtrs.size() > 1)
-        return false;
-
-      if (!isNoWrap(PSE, AR, Ptr, AccessTy, TheLoop, Assume))
-        return false;
+    if (ShouldCheckWrap &&
+        !isNoWrap(PSE, AR, TranslatedPtrs.size() == 1 ? Ptr : nullptr, AccessTy,
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fhahn wrote:

If there is exactly one, it means that we have translated the IR pointer directly to a corresponding SCEV, and we can use the IR value in the analysis.

There could be more translated pointers, e.g. if the IR pointer is something like `%p = select %c, ptr %a, ptr %b`. There's logic to look through things like select/phi and it may return multiple SCEVs, one for each possible option. For the select mentioned earlier, TranslatedPointers may contain 2 entries, one with the SCEV for %a and one with the SCEV for %b.

In that case we do not try to find IR expressions corresponding to the SCEVs, and most of the logic looking at the IR value would not be safe, as the IR value may never be executed (i.e. we cannot assume it being poison would cause UB)

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