[llvm] [memcpyopt] handle memcpy from memset in more cases (PR #140954)

[Jameson Nash via llvm-commits]

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@@ -1403,6 +1404,24 @@ static bool hasUndefContents(MemorySSA *MSSA, BatchAAResults &AA, Value *V,
   return false;
 }
 
+static bool coversInputFully(MemorySSA *MSSA, MemCpyInst *MemCpy,
+                             MemIntrinsic *MemSrc, BatchAAResults &BAA) {
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vtjnash wrote:

The CanReduceSize bool is actually a property of having both sizes be constants (the other conditional here). If they aren't constants, then you cannot reduce the size, though this query and this optimization are still okay

https://github.com/llvm/llvm-project/pull/140954