[all-commits] [llvm/llvm-project] f2816f: [InstCombine] Simplify and/or by replacing operand...

[Yingwei Zheng via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: f2816ff60c7dae0347beba9b11154b33e6311059
      https://github.com/llvm/llvm-project/commit/f2816ff60c7dae0347beba9b11154b33e6311059
  Author: Yingwei Zheng <dtcxzyw2333 at gmail.com>
  Date:   2024-01-31 (Wed, 31 Jan 2024)

  Changed paths:
    M llvm/lib/Transforms/InstCombine/InstCombineAndOrXor.cpp
    M llvm/test/Transforms/InstCombine/and-or-icmps.ll
    M llvm/test/Transforms/InstCombine/and-or-not.ll
    M llvm/test/Transforms/InstCombine/and-xor-or.ll
    M llvm/test/Transforms/InstCombine/or-xor.ll
    M llvm/test/Transforms/InstCombine/or.ll

  Log Message:
  -----------
  [InstCombine] Simplify and/or by replacing operands with constants (#77231)

This patch tries to simplify `X | Y` by replacing occurrences of `Y` in
`X` with 0. Similarly, it tries to simplify `X & Y` by replacing
occurrences of `Y` in `X` with -1.

Alive2: https://alive2.llvm.org/ce/z/cNjDTR
Note: As the current implementation is too conservative in the one-use
checks, I cannot remove other existing hard-coded simplifications if
they involves more than two instructions (e.g, `A & ~(A ^ B) --> A &
B`).

Compile-time impact:
http://llvm-compile-time-tracker.com/compare.php?from=a085402ef54379758e6c996dbaedfcb92ad222b5&to=9d655c6685865ffce0ad336fed81228f3071bd03&stat=instructions%3Au

|stage1-O3|stage1-ReleaseThinLTO|stage1-ReleaseLTO-g|stage1-O0-g|stage2-O3|stage2-O0-g|stage2-clang|
|--|--|--|--|--|--|--|
|+0.01%|-0.00%|+0.00%|-0.02%|+0.01%|+0.02%|-0.01%|

Fixes #76554.