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* Re: optimization/3978: arm peephole for loading two consecutive memory locations generates suboptimal code (on arm7tdmi)
@ 2001-08-10 3:26 rearnsha
0 siblings, 0 replies; 3+ messages in thread
From: rearnsha @ 2001-08-10 3:26 UTC (permalink / raw)
To: gcc-bugs, gcc-prs, nobody, segher
Synopsis: arm peephole for loading two consecutive memory locations generates suboptimal code (on arm7tdmi)
State-Changed-From-To: open->closed
State-Changed-By: rearnsha
State-Changed-When: Fri Aug 10 03:26:43 2001
State-Changed-Why:
Duplicate of 3977
http://gcc.gnu.org/cgi-bin/gnatsweb.pl?cmd=view&pr=3978&database=gcc
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: optimization/3978: arm peephole for loading two consecutive memory locations generates suboptimal code (on arm7tdmi)
@ 2001-08-09 14:16 Philip Blundell
0 siblings, 0 replies; 3+ messages in thread
From: Philip Blundell @ 2001-08-09 14:16 UTC (permalink / raw)
To: nobody; +Cc: gcc-prs
The following reply was made to PR optimization/3978; it has been noted by GNATS.
From: Philip Blundell <philb@gnu.org>
To: segher@chello.nl
Cc: gcc-gnats@gcc.gnu.org
Subject: Re: optimization/3978: arm peephole for loading two consecutive memory locations generates suboptimal code (on arm7tdmi)
Date: Thu, 09 Aug 2001 22:12:51 +0100
--==_Exmh_1440650826P
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>I often see generated code like
>
>add temp, pointer, #offset
>ldmia temp, {regA, regB}
>
>(after which temp is dead)
>
>which is slower than just
>
>ldr regA, [pointer, #offset]
>ldr regB, [pointer, #offset+4]
>
>and wastes a register as well
Use -mtune=arm8 or some such. I don't think this will do any harm on
ARM7TDMI and it should yield the results you are looking for.
p.
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^ permalink raw reply [flat|nested] 3+ messages in thread
* optimization/3978: arm peephole for loading two consecutive memory locations generates suboptimal code (on arm7tdmi)
@ 2001-08-09 12:56 segher
0 siblings, 0 replies; 3+ messages in thread
From: segher @ 2001-08-09 12:56 UTC (permalink / raw)
To: gcc-gnats
>Number: 3978
>Category: optimization
>Synopsis: arm peephole for loading two consecutive memory locations generates suboptimal code (on arm7tdmi)
>Confidential: no
>Severity: non-critical
>Priority: medium
>Responsible: unassigned
>State: open
>Class: pessimizes-code
>Submitter-Id: net
>Arrival-Date: Thu Aug 09 12:56:00 PDT 2001
>Closed-Date:
>Last-Modified:
>Originator: segher@chello.nl
>Release: 3.0
>Organization:
>Environment:
>Description:
I often see generated code like
add temp, pointer, #offset
ldmia temp, {regA, regB}
(after which temp is dead)
which is slower than just
ldr regA, [pointer, #offset]
ldr regB, [pointer, #offset+4]
and wastes a register as well
>How-To-Repeat:
a lot of code will do this
>Fix:
change the peephole, i think
>Release-Note:
>Audit-Trail:
>Unformatted:
^ permalink raw reply [flat|nested] 3+ messages in thread
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2001-08-10 3:26 optimization/3978: arm peephole for loading two consecutive memory locations generates suboptimal code (on arm7tdmi) rearnsha
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2001-08-09 14:16 Philip Blundell
2001-08-09 12:56 segher
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