Noah Goldstein 60e8915d22 [InstCombine] Add folds for (add/sub/disjoint_or/icmp C, (ctpop (not x))) ...

`(ctpop (not x))` <-> `(sub nuw nsw BitWidth(x), (ctpop x))`. The
`sub` expression can sometimes be constant folded depending on the use
case of `(ctpop (not x))`.

This patch adds fold for the following cases:

`(add/sub/disjoint_or C, (ctpop (not x))`
    -> `(add/sub/disjoint_or C', (ctpop x))`
`(cmp pred C, (ctpop (not x))`
    -> `(cmp swapped_pred C', (ctpop x))`

Where `C'` depends on how we constant fold `C` with `BitWidth(x)` for
the given opcode.

Proofs: https://alive2.llvm.org/ce/z/qUgfF3

Closes #77859

2024-01-15 12:05:38 -08:00

107 KiB

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