[PATCH] D142271: [ValueTracking] Add KnownBits patterns `xor(x, x - 1)` and `and(x, -x)` for knowing upper bits to be zero

[Jay Foad via Phabricator via llvm-commits]

foad added a comment.

In D142271#4073849 <https://reviews.llvm.org/D142271#4073849>, @foad wrote:

> I suggest implementing this in new helper functions `KnownBits::blsi` and `KnownBits::blsmsk` (if we're happy with those names), plus comprehensive test coverage in `unittests/Support/KnownBitsTest.cpp`.

I was thinking of something like D142469 <https://reviews.llvm.org/D142469>. Is this any use to you?


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https://reviews.llvm.org/D142271