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* Re: optimization/6405: Loop-unrolling related performance regressions
@ 2002-09-08 11:47 sayle
0 siblings, 0 replies; 2+ messages in thread
From: sayle @ 2002-09-08 11:47 UTC (permalink / raw)
To: gcc-bugs, gcc-prs, nobody, roger
Synopsis: Loop-unrolling related performance regressions
State-Changed-From-To: open->closed
State-Changed-By: sayle
State-Changed-When: Sun Sep 8 11:47:35 2002
State-Changed-Why:
This has now been fixed on mainline by the following patch:
2002-09-08 Roger Sayle <roger@eyesopen.com>
PR optimization/6405
* unroll.c (loop_iterations): last_loop_insn should be the previous
non-note instruction before loop->end.
* loop.c (strength_reduce): The conditional jump is the last
non-note instruction before loop->end (as above).
http://gcc.gnu.org/cgi-bin/gnatsweb.pl?cmd=view%20audit-trail&database=gcc&pr=6405
^ permalink raw reply [flat|nested] 2+ messages in thread
* optimization/6405: Loop-unrolling related performance regressions
@ 2002-04-22 7:56 roger
0 siblings, 0 replies; 2+ messages in thread
From: roger @ 2002-04-22 7:56 UTC (permalink / raw)
To: gcc-gnats; +Cc: roger
>Number: 6405
>Category: optimization
>Synopsis: Loop-unrolling related performance regressions
>Confidential: no
>Severity: non-critical
>Priority: medium
>Responsible: unassigned
>State: open
>Class: pessimizes-code
>Submitter-Id: net
>Arrival-Date: Mon Apr 22 07:56:00 PDT 2002
>Closed-Date:
>Last-Modified:
>Originator: Roger Sayle <roger@eyesopen.com>
>Release: gcc-3.1 branch and mainline 20020422
>Organization:
>Environment:
All platforms, but first observed on i686-pc-linux-gnu.
>Description:
See http://gcc.gnu.org/ml/gcc/2002-02/msg00307.html
With the command line options "-O3 -funroll-loops", GCC 2.96
generates better code for the attached loop than GCC 3.1
(prerelease) or mainline. A correctness fix had the side
effect that the compiler can no longer determine that this
loop iterates a fix number of times.
>How-To-Repeat:
Compile the attached loop.c with "-O2 -funroll-all-loops"
and inspect the assembly code generated.
>Fix:
>Release-Note:
>Audit-Trail:
>Unformatted:
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2002-09-08 11:47 optimization/6405: Loop-unrolling related performance regressions sayle
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