[llvm] [ValueTracking] Teach isGuaranteedNotToBeUndefOrPoison about splats (PR #163570)

[David Sherwood via llvm-commits]

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@@ -7678,6 +7678,7 @@ static bool isGuaranteedNotToBeUndefOrPoison(
         return true;
     }
 
+    Value *Splat;
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david-arm wrote:

I think you can move this below the `if (!::canCreateUndefOrPoison` statement.

https://github.com/llvm/llvm-project/pull/163570