[PATCH] D62544: [InstCombine] Optimize always overflowing signed saturating add/sub

[Nikita Popov via Phabricator via llvm-commits]

nikic marked an inline comment as done.
nikic added inline comments.


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Comment at: llvm/lib/Transforms/InstCombine/InstCombineCalls.cpp:2073-2074
+        unsigned BitWidth = Ty->getScalarSizeInBits();
+        APInt Min = SI->isSigned() ? APInt::getSignedMinValue(BitWidth)
+                                   : APInt::getMinValue(BitWidth);
+        return replaceInstUsesWith(*SI, ConstantInt::get(Ty, Min));
----------------
lebedev.ri wrote:
> Can you use `APSInt::getMinValue(BitWidth, !SI->isSigned())` instead?
It works, but I'm wondering whether it's okay to use APSInt for this purpose. It looks like APSInt is used heavily by clang, but the only uses in the LLVM middle end are for interfacing with the convertToInteger() APFloat API.


Repository:
  rL LLVM

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  https://reviews.llvm.org/D62544/new/

https://reviews.llvm.org/D62544