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Date: Sun, 02 Jun 2019 12:28:00 -0000
From: Segher Boessenkool <segher@kernel.crashing.org>
To: Fredrik Hederstierna <fredrik.hederstierna@verisure.com>
Cc: "gcc@gcc.gnu.org" <gcc@gcc.gnu.org>
Subject: Re: ARM peephole2 from 2003 never merged, still valid
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On Sat, Jun 01, 2019 at 11:41:30PM +0000, Fredrik Hederstierna wrote:
> +(define_peephole2
> +  [(set (match_operand:SI 0 "arm_general_register_operand" "")
> +       (match_operand:SI 1 "arm_general_register_operand" ""))
> +   (set (reg:CC CC_REGNUM)
> +       (compare:CC (match_dup 0) (const_int 0)))]
> +  "TARGET_ARM"
> +  [(parallel [(set (reg:CC CC_REGNUM) (compare:CC (match_dup 1) (const_int 0)))
> +             (set (match_dup 0) (match_dup 1))])]
> +  ""
> +)

Hi Fredrik,

Do you have a testcase for this?  I wonder if it would be better handled
during combine, and what that then tried; or perhaps these opportunities
are created later, making a peephole a more attractive solution.


Segher