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Date: Sun, 22 Mar 2020 14:30:42 -0500
From: Segher Boessenkool <segher@kernel.crashing.org>
To: Richard Henderson <richard.henderson@linaro.org>
Cc: gcc-patches@gcc.gnu.org, richard.earnshaw@arm.com, Wilco.Dijkstra@arm.com, 
 marcus.shawcroft@arm.com
Subject: Re: [PATCH v2 3/9] aarch64: Add <su>cmp_*_carryinC patterns
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Hi!

On Fri, Mar 20, 2020 at 07:42:25PM -0700, Richard Henderson via Gcc-patches wrote:
> Duplicate all usub_*_carryinC, but use xzr for the output when we
> only require the flags output.  The signed versions use sign_extend
> instead of zero_extend for combine's benefit.

You actually use ANY_EXTEND, which makes a lot more sense :-)

Did you see combine create a sign_extend, ever?  Or do those just come
from combining other insns that already contain a sign_extend?


Segher