[InstCombine] Canonicalize sub mask, X -> ~X when high bits are ignored
#110635
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This was referenced Oct 1, 2024
nikic
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Oct 1, 2024
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✅ With the latest revision this PR passed the C/C++ code formatter. |
Sterling-Augustine
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…ored (llvm#110635) Alive2: https://alive2.llvm.org/ce/z/NJgBPL The motivating case of this patch is to emit `andn` on RISC-V with zbb for expressions like `(sub 63, X) & 63`.
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Alive2: https://alive2.llvm.org/ce/z/NJgBPL
The motivating case of this patch is to emit
andnon RISC-V with zbb for expressions like(sub 63, X) & 63.An alternative is shrinking the LHS constant in SDAG. But I think this patch may expose more folding/sinking opportunities.