From: Richard Henderson <rth@redhat.com>
To: Jeff Law <law@redhat.com>, "H. Peter Anvin" <hpa@zytor.com>
Cc: gcc-patches@gcc.gnu.org, peterz@infradead.org,
torvalds@linux-foundation.org, jakub@redhat.com,
Segher Boessenkool <segher@kernel.crashing.org>
Subject: Re: [RFC 0/6] Flags outputs for asms
Date: Fri, 08 May 2015 21:55:00 -0000 [thread overview]
Message-ID: <554D30CD.3010506@redhat.com> (raw)
In-Reply-To: <554D2B8A.4010506@redhat.com>
On 05/08/2015 02:32 PM, Jeff Law wrote:
> On 05/08/2015 02:15 PM, Richard Henderson wrote:
>>
>> But it *does* try to match an intermediate pattern,
>>
>> (set (reg:CCGC 17 flags)
>> (compare:CCGC (reg:CCGC 17 flags)
>> (const_int 0 [0])))
>>
>> which can be considered a no-op move. If I add the attached pattern, then the
>> combination happens in two steps -- 9->12, 12->13 -- and we get what we hoped:
> So what happens if that pattern is actually recognized as a nop-move by
> set_noop_p? That would allow recog_for_combine to see it as a nop and
> "recognize" it as valid.
Interesting suggestion -- I hadn't thought of that. It might be easier than
playing with use_crosses_set_p, and certainly better than the nop_cmp pattern.
I'll have a go at this later.
r~
next prev parent reply other threads:[~2015-05-08 21:55 UTC|newest]
Thread overview: 33+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-05-07 21:39 Richard Henderson
2015-05-07 21:39 ` [PATCH 4/6] Convert to md_asm_adjust Richard Henderson
2015-05-08 19:41 ` Jeff Law
2015-05-08 19:56 ` Richard Henderson
2015-05-07 21:39 ` [PATCH 6/6] i386: Implement asm flag outputs Richard Henderson
2015-05-08 18:40 ` H. Peter Anvin
2015-05-08 18:45 ` Jeff Law
2015-05-15 15:46 ` [PATCH v2 " Richard Henderson
2015-05-20 16:26 ` Jeff Law
2015-05-20 16:36 ` H. Peter Anvin
2015-05-20 17:28 ` Richard Henderson
2015-05-07 21:39 ` [PATCH 2/6] Merge expand_asm_operands into expand_asm_stmt Richard Henderson
2015-05-08 18:54 ` Jeff Law
2015-05-07 21:39 ` [PATCH 1/6] Only resolve_asm_operand_names once Richard Henderson
2015-05-08 18:11 ` Jeff Law
2015-05-07 21:39 ` [PATCH 3/6] Canonicalize asm volatility earlier Richard Henderson
2015-05-08 18:12 ` Jeff Law
2015-05-07 21:39 ` [PATCH 5/6] i386: Add CCPmode Richard Henderson
2015-05-08 18:16 ` Jeff Law
2015-05-08 1:15 ` [RFC 0/6] Flags outputs for asms H. Peter Anvin
2015-05-08 1:20 ` H. Peter Anvin
2015-05-08 15:24 ` Richard Henderson
2015-05-08 15:37 ` Jay Foad
2015-05-08 15:39 ` Jeff Law
2015-05-08 15:54 ` Richard Henderson
2015-05-08 17:46 ` H. Peter Anvin
2015-05-08 20:15 ` Richard Henderson
2015-05-08 21:14 ` Segher Boessenkool
2015-05-08 22:11 ` Richard Henderson
2015-05-08 21:33 ` Jeff Law
2015-05-08 21:55 ` Richard Henderson [this message]
2015-05-08 22:10 ` Segher Boessenkool
2015-05-11 13:19 ` Segher Boessenkool
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