[llvm] [LoopIdiom] Do not emit wcslen for underaligned wide loads (PR #216080)

[Ömer Sinan Ağacan via llvm-commits]

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@@ -2107,10 +2107,20 @@ class StrlenVerifier {
       return false;
     if (OpWidth != 8 && OpWidth != 16 && OpWidth != 32)
       return false;
-    if (OpWidth >= 16)
+    if (OpWidth >= 16) {
       if (OpWidth != WcharSize * 8)
         return false;
 
+      // wcslen requires a pointer aligned to wchar_t. Loops that load
+      // wchar_t-sized values at weaker alignment (e.g. memcpy from a byte
+      // buffer) must not be rewritten as wcslen.
+      Align RequiredAlign(WcharSize);
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osa1 wrote:

I don't understand why you're initializing an alignment value as the size?

`getABITypeAlign` may be the method we want to use here: https://github.com/llvm/llvm-project/blob/e5174fe683e882f6bbd2ef023c9c9e293b273a98/llvm/include/llvm/IR/DataLayout.h#L630

https://github.com/llvm/llvm-project/pull/216080