[llvm] [LVI][ValueTracking] Take UB-implying attributes into account in `isSafeToSpeculativelyExecute` (PR #137604)

[Nikita Popov via llvm-commits]

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@@ -7287,7 +7286,20 @@ bool llvm::isSafeToSpeculativelyExecuteWithOpcode(
 
     // The called function could have undefined behavior or side-effects, even
     // if marked readnone nounwind.
-    return Callee && Callee->isSpeculatable();
+    if (!Callee || !Callee->isSpeculatable())
+      return false;
+    // Since the operands may be changed after hoisting, undefined behavior may
+    // be triggered by some UB-implying attributes.
+    if (!AllowRefinement) {
+      if (CI->hasRetAttr(Attribute::NoUndef) ||
+          CI->getRetDereferenceableBytes() > 0 ||
+          CI->getRetDereferenceableOrNullBytes() > 0 ||
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nikic wrote:

I think we should have a has() query for dropUBImplyingAttrsAndMetadata similar to how we have hasPoisonGeneratingAnnotations and dropPoisonGeneratingAnnotations, so we can keep these things in sync.

https://github.com/llvm/llvm-project/pull/137604