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RE: [PATCH] [Aarch64] Optimize subtract in shift counts
From: Richard Kenner [mailto:email@example.com]
Sent: Tuesday, August 8, 2017 1:20 PM
To: Michael Collison <Michael.Collison@arm.com>
Cc: firstname.lastname@example.org; nd <email@example.com>; firstname.lastname@example.org
Subject: RE: [PATCH] [Aarch64] Optimize subtract in shift counts
> Correct. It is truncated for integer shift, but not simd shift
> instructions. We generate a pattern in the split that only generates
> the integer shift instructions.
That's unfortunate, because it would be nice to do this in simplify_rtx, since it's machine-independent, but that has to be conditioned on SHIFT_COUNT_TRUNCATED, so you wouldn't get the benefit of it.