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* Re: c/3913: On Athlon's, gcc 3.0 produces code running 1/2 as fast as gcc 2.95
@ 2002-04-24 14:41 rth
0 siblings, 0 replies; 2+ messages in thread
From: rth @ 2002-04-24 14:41 UTC (permalink / raw)
To: gcc-bugs, gcc-prs, nobody, rwhaley
Synopsis: On Athlon's, gcc 3.0 produces code running 1/2 as fast as gcc 2.95
State-Changed-From-To: open->closed
State-Changed-By: rth
State-Changed-When: Wed Apr 24 14:41:30 2002
State-Changed-Why:
From the web page:
NOTE: all of these problems appear to be fixed in the newer 3.1 preleases. I tested gcc-20020225.tar.gz, and found it performed indistinguishably from 2.95.2 for both Athlon and PIII. An ATLAS user has independently verified this observation for PIII/P4.
http://gcc.gnu.org/cgi-bin/gnatsweb.pl?cmd=view%20audit-trail&database=gcc&pr=3913
^ permalink raw reply [flat|nested] 2+ messages in thread
* c/3913: On Athlon's, gcc 3.0 produces code running 1/2 as fast as gcc 2.95
@ 2001-08-01 17:56 rwhaley
0 siblings, 0 replies; 2+ messages in thread
From: rwhaley @ 2001-08-01 17:56 UTC (permalink / raw)
To: gcc-gnats; +Cc: rwhaley
>Number: 3913
>Category: c
>Synopsis: On Athlon's, gcc 3.0 produces code running 1/2 as fast as gcc 2.95
>Confidential: no
>Severity: serious
>Priority: medium
>Responsible: unassigned
>State: open
>Class: pessimizes-code
>Submitter-Id: net
>Arrival-Date: Wed Aug 01 17:56:00 PDT 2001
>Closed-Date:
>Last-Modified:
>Originator: rwhaley@cs.utk.edu
>Release: gcc version 3.0
>Organization:
>Environment:
RedHat Linux 7.1 on a 1.2Ghz Athlon. gcc -v gives:
hades. /usr/local/gcc-3.0/bin/gcc -v
Reading specs from /usr/local/gcc-3.0/lib/gcc-lib/i686-pc-linux-gnu/3.0/specs
Configured with: ./configure --prefix=/usr/local/gcc-3.0
Thread model: single
gcc version 3.0
>Description:
The new memory fetch scheduling algorithm reduces Athlon performance by a factor of 2 over the one used by gcc 2.95.x. It also appears that the x87 register stack utilization algorithm is worse than 2.95.x as well.
Problem is too complex to reduce to 1 single preprocessed file. The full problem is detailed (along with code to reproduce, and assembler outputs) here:
http://www.cs.utk.edu/~rwhaley/ATLAS/gcc30.html
>How-To-Repeat:
http://www.cs.utk.edu/~rwhaley/ATLAS/gcc30.html#dup
>Fix:
Have option to use 2.95 scheduler for scheduling problem.
Have option to use 2.95 x87 register stack for register stack usage problem.
>Release-Note:
>Audit-Trail:
>Unformatted:
^ permalink raw reply [flat|nested] 2+ messages in thread
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2002-04-24 14:41 c/3913: On Athlon's, gcc 3.0 produces code running 1/2 as fast as gcc 2.95 rth
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