Antonio Frighetto adfd59fdb8 [InstCombine] Introduce foldICmpBinOpWithConstantViaTruthTable folding ...

Match icmps of binops where both operands are select with constant arms,
i.e., `icmp pred (select A ? C1 : C2) binop (select B ? C3 : C4), C5`.
Fold such patterns by creating a truth table of the possible four
constant variants, and materialize back the optimal logic from it via
`createLogicFromTable` helper. This also generalizes an existing fold,
which has therefore been dropped.

Proofs: https://alive2.llvm.org/ce/z/NS7Vzu.

Fixes: https://github.com/llvm/llvm-project/issues/138212.

2025-05-13 09:04:25 +02:00

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