[all-commits] [llvm/llvm-project] 051ec9: [ValueTracking] Strengthen impliesPoison reasoning

[Nikita Popov via All-commits]

  Branch: refs/heads/master
  Home:   https://github.com/llvm/llvm-project
  Commit: 051ec9f5f43a83e23bd3e20e512fc5ec44c19850
      https://github.com/llvm/llvm-project/commit/051ec9f5f43a83e23bd3e20e512fc5ec44c19850
  Author: Nikita Popov <nikita.ppv at gmail.com>
  Date:   2021-01-19 (Tue, 19 Jan 2021)

  Changed paths:
    M llvm/lib/Analysis/ValueTracking.cpp
    M llvm/test/Transforms/InstCombine/select-and-or.ll
    M llvm/unittests/Analysis/ValueTrackingTest.cpp

  Log Message:
  -----------
  [ValueTracking] Strengthen impliesPoison reasoning

Split impliesPoison into two recursive walks, one over V, the
other over ValAssumedPoison. This allows us to reason about poison
implications in a number of additional cases that are important
in practice. This is a generalized form of D94859, which handles
the cmp to cmp implication in particular.

Differential Revision: https://reviews.llvm.org/D94866