Craig Topper 7cd725858b [RISCV] RISCVDAGToDAGISel::selectShiftMask to shift by (sub size-1, X). ...

If the shift amount is (sub C, X) where C is -1 modulo the size of
the shift, we can replace the sub with a NOT.

We could also use XORI X, size-1, but NOT would work better with
c.not from the future Zce extension.

2022-12-29 16:33:18 -08:00

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