From: Richard Kenner [mailto:ken...@vlsi1.ultra.nyu.edu]
Sent: Tuesday, August 8, 2017 1:20 PM
To: Michael Collison <michael.colli...@arm.com>
Cc: firstname.lastname@example.org; nd <n...@arm.com>; pins...@gmail.com
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.