[PATCH] D58650: Add support for computing "zext of value" in KnownBits. NFCI
Bjorn Pettersson via Phabricator via llvm-commits
llvm-commits at lists.llvm.org
Wed Feb 27 06:04:25 PST 2019
bjope marked an inline comment as done.
bjope added inline comments.
================
Comment at: llvm/include/llvm/Support/KnownBits.h:123
+ APInt NewZero = Zero.zext(BitWidth);
+ if (ExtendedBitsAreKnownZero)
+ NewZero.setBitsFrom(OldBitWidth);
----------------
RKSimon wrote:
> if (BitWidth > OldBitWidth && ExtendedBitsAreKnownZero)
The calls to Zero.zext(...) and One.zext(...) will assert if not increasing the width. You need to use zextOrTrunc (maybe there is a zextOrSelf as well) if it should be allowed to have the same size.
I guess that is why these methods hasn't been asserting themselves earlier. Should I add an explicit assert here instead of a condition that always should be fulfilled? Or is it OK as is, given this answer?
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https://reviews.llvm.org/D58650/new/
https://reviews.llvm.org/D58650
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