[PATCH] D123819: [InstCombine] Fold strlen and strnlen recursively.

[Nikita Popov via Phabricator via llvm-commits]

nikic added a comment.

As mentioned on the original review, I think we would be better off not passing the Bound to minStringLength() and instead doing one umin at the end -- this avoids the need to handle this in each branch. Though possibly I forgot some reason why that doesn't work from the previous discussion.



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Comment at: llvm/lib/Transforms/Utils/SimplifyLibCalls.cpp:714
           (isa<GlobalVariable>(GEP->getOperand(0)) &&
-           NullTermIdx == ArrSize - 1)) {
-        Offset = B.CreateSExtOrTrunc(Offset, CI->getType());
-        return B.CreateSub(ConstantInt::get(CI->getType(), NullTermIdx),
-                           Offset);
+           (NullTermIdx == ArrSize - 1) && (!Bound || MaxLen < UINT64_MAX))) {
+        // Fold strnlen(s + x, Bound) -> min(strlen(s) - x, Bound)
----------------
Why is this condition needed?


CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D123819/new/

https://reviews.llvm.org/D123819