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Unverified Commit f2816ff6 authored by Yingwei Zheng's avatar Yingwei Zheng Committed by GitHub
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[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.
parent 8a980911
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