[PATCH] D79234: [ValueTracking] Fix computeKnownBits() with bitwidth-changing ptrtoint

[Nikita Popov via Phabricator via llvm-commits]

nikic created this revision.
nikic added reviewers: spatel, lebedev.ri.
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computeKnownBitsFromAssume() currently asserts if m_V matches a ptrtoint that changes the bitwidth. Because InstCombine canonicalizes ptrtoint instructions to use explicit zext/trunc, we never ran into the issue in practice. I'm adding unit tests, as I don't know if this can be triggered via IR anywhere.

Fix this by calling anyextOrTrunc(BitWidth) on the computed KnownBits. Note that we are going from the KnownBits of the ptrtoint result to the KnownBits of the ptrtoint operand, so we need to truncate if the ptrtoint zexted and anyext if the ptrtoint truncated.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D79234

Files:
  lib/Analysis/ValueTracking.cpp
  unittests/Analysis/ValueTrackingTest.cpp

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