From: Segher Boessenkool <segher@kernel.crashing.org>
To: Roger Sayle <roger@nextmovesoftware.com>
Cc: gcc-patches@gcc.gnu.org, "'Uros Bizjak'" <ubizjak@gmail.com>
Subject: Re: [x86 PATCH] Fun with flags: Adding stc/clc instructions to i386.md.
Date: Fri, 8 Jul 2022 16:08:55 -0500 [thread overview]
Message-ID: <20220708210855.GC25951@gate.crashing.org> (raw)
In-Reply-To: <003b01d8929a$70be2cc0$523a8640$@nextmovesoftware.com>
Hi!
On Fri, Jul 08, 2022 at 08:14:58AM +0100, Roger Sayle wrote:
> This patch adds support for x86's single-byte encoded stc (set carry flag)
> and clc (clear carry flag) instructions to i386.md.
Maybe add a test for clc as well? Because:
> +(define_insn "x86_clc"
> + [(set (reg:CCC FLAGS_REG) (const_int 0))]
> + ""
> + "stc"
> + [(set_attr "length" "1")
> + (set_attr "length_immediate" "0")
> + (set_attr "modrm" "0")])
Spot the problem :-)
> +/* { dg-final { scan-assembler "stc" } } */
This checks if the substring "stc" occurs anywhere in the generated
assembler code. More robust is to use scan-assembler-times, and to use
\mstc\M (same as \<stc\> in some other languages, or \bstc\b in Perl).
Segher
prev parent reply other threads:[~2022-07-08 21:09 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-07-08 7:14 Roger Sayle
2022-07-08 7:23 ` Uros Bizjak
2022-07-08 7:59 ` Uros Bizjak
2022-07-08 21:08 ` Segher Boessenkool [this message]
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