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Subject: Re: [PATCH][v3] GIMPLE store merging pass
To: Richard Biener <rguenther@suse.de>, Jakub Jelinek <jakub@redhat.com>
References: <57CEDD67.6010801@foss.arm.com> <20160906153250.GK14857@tucnak.redhat.com> <57CEE7DB.8070604@foss.arm.com> <20160906162133.GL14857@tucnak.redhat.com> <alpine.LSU.2.11.1609071010210.26629@t29.fhfr.qr>
Cc: Kyrill Tkachov <kyrylo.tkachov@foss.arm.com>,        Uros Bizjak <ubizjak@gmail.com>, GCC Patches <gcc-patches@gcc.gnu.org>
From: Bernd Schmidt <bschmidt@redhat.com>
Message-ID: <4f894602-e64c-f571-6c50-5239a175bd02@redhat.com>
Date: Wed, 07 Sep 2016 13:32:00 -0000
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On 09/07/2016 10:19 AM, Richard Biener wrote:
> On Tue, 6 Sep 2016, Jakub Jelinek wrote:

>> If you want a 64-bit store, you'd need to merge the two, and that would be
>> even more expensive.  It is a matter of say:
>> 	movl $0x12345678, (%rsp)
>> 	movl $0x09abcdef, 4(%rsp)
>> vs.
>> 	movabsq $0x09abcdef12345678, %rax
>> 	movq %rax, (%rsp)
>> vs.
>> 	movl $0x09abcdef, %eax
>> 	salq $32, %rax
>> 	orq $0x12345678, %rax
>> 	movq $rax, (%rsp)
>
> vs.
>
>         movq $LC0, (%rsp)
>
> ?

Not the same. That moves the address of $LC0.


Bernd