[PATCH] D123816: [InstCombine] Fold strnlen with a bound of zero and one.

[Nikita Popov via Phabricator via llvm-commits]

nikic requested changes to this revision.
nikic added inline comments.
This revision now requires changes to proceed.


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Comment at: llvm/include/llvm/Transforms/Utils/SimplifyLibCalls.h:242
+  Value *optimizeStringLength(CallInst *CI, IRBuilderBase &B, unsigned CharSize,
+			      Value *Bound = nullptr);
 };
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nit: Indent not aligned.


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Comment at: llvm/lib/Transforms/Utils/SimplifyLibCalls.cpp:649
+        Value *ZeroLen = ConstantInt::get(CI->getType(), 0);
+        return B.CreateSelect(Cmp, ZeroLen, BoundCst, "strnlen.sel");
+      }
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Isn't this select the wrong way around? You're doing `*s != 0 ? 0 : 1` here.

You might also want to directly emit the zext form if InstCombine is going to fold it anyway, so that would be `zext(s != 0)`.


Repository:
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  https://reviews.llvm.org/D123816/new/

https://reviews.llvm.org/D123816