[all-commits] [llvm/llvm-project] 6749d1: [KnownBits] Add blsi and blsmsk

[goldsteinn via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: 6749d187c6dfd1b126698e44276bbf1f9050beb8
      https://github.com/llvm/llvm-project/commit/6749d187c6dfd1b126698e44276bbf1f9050beb8
  Author: Jay Foad <jay.foad at amd.com>
  Date:   2023-02-18 (Sat, 18 Feb 2023)

  Changed paths:
    M llvm/include/llvm/Support/KnownBits.h
    M llvm/lib/Support/KnownBits.cpp
    M llvm/unittests/Support/KnownBitsTest.cpp

  Log Message:
  -----------
  [KnownBits] Add blsi and blsmsk

Reviewed By: nikic

Differential Revision: https://reviews.llvm.org/D142519


  Commit: c8fb2775cee0e80b07ba99d8f4986c170ff6e2be
      https://github.com/llvm/llvm-project/commit/c8fb2775cee0e80b07ba99d8f4986c170ff6e2be
  Author: Noah Goldstein <goldstein.w.n at gmail.com>
  Date:   2023-02-18 (Sat, 18 Feb 2023)

  Changed paths:
    A llvm/test/Analysis/ValueTracking/knownbits-bmi-pattern.ll

  Log Message:
  -----------
  [ValueTracking] Add tests for known bits after common BMI pattern (blsmsk/blsi); NFC

Differential Revision: https://reviews.llvm.org/D142270


  Commit: 9a8f517f5750050e9df4bca332e90d38d075f6a7
      https://github.com/llvm/llvm-project/commit/9a8f517f5750050e9df4bca332e90d38d075f6a7
  Author: Noah Goldstein <goldstein.w.n at gmail.com>
  Date:   2023-02-18 (Sat, 18 Feb 2023)

  Changed paths:
    M llvm/lib/Analysis/ValueTracking.cpp
    M llvm/test/Analysis/ValueTracking/knownbits-bmi-pattern.ll
    M llvm/test/Transforms/InstCombine/ctpop-pow2.ll
    M llvm/test/Transforms/InstSimplify/ctpop-pow2.ll

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

These two BMI pattern will clear the upper bits of result past the
first set bit. So if we know a single bit in `x` is set, we know that
`results[bitwidth - 1, log2(x) + 1] = 0`.

Alive2:
blsmsk: https://alive2.llvm.org/ce/z/a397BS
blsi: https://alive2.llvm.org/ce/z/tsbQhC

Differential Revision: https://reviews.llvm.org/D142271


Compare: https://github.com/llvm/llvm-project/compare/4384127549e2...9a8f517f5750