Simon Pilgrim d40b7f0d5a [DAG] Fold (shl (srl x, c), c) -> and(x, m) even if srl has other uses ...

If we're using shift pairs to mask, then relax the one use limit if the shift amounts are equal - we'll only be generating a single AND node.

AArch64 has a couple of regressions due to this, so I've enforced the existing one use limit inside a AArch64TargetLowering::shouldFoldConstantShiftPairToMask callback.

Part of the work to fix the regressions in D77804

Differential Revision: https://reviews.llvm.org/D125607

2022-05-17 13:40:11 +01:00

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