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* [Bug tree-optimization/53397] New: Scimark performance drops by 10x times when compiled -O3 -march=amdfam10 due to generation more prefecthes
@ 2012-05-18 12:07 venkataramanan.kumar at amd dot com
2012-05-18 12:10 ` [Bug tree-optimization/53397] " venkataramanan.kumar at amd dot com
` (2 more replies)
0 siblings, 3 replies; 4+ messages in thread
From: venkataramanan.kumar at amd dot com @ 2012-05-18 12:07 UTC (permalink / raw)
To: gcc-bugs
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=53397
Bug #: 53397
Summary: Scimark performance drops by 10x times when compiled
-O3 -march=amdfam10 due to generation more prefecthes
Classification: Unclassified
Product: gcc
Version: tree-ssa
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: tree-optimization
AssignedTo: unassigned@gcc.gnu.org
ReportedBy: venkataramanan.kumar@amd.com
With GCC4.7 the benchmark score drops from ~400 Mflops to ~40 mflops. Almost 10
folds.
Prefecth instructions introduced in the innermost loops of
"FFT_transform_internal" ( FFT.c ) in GCC4.7 but not in GCC4.6 which is causing
the slow down.
Compiling this function alone as a separate test case with
-fno-prefetch-loop-arrays brings back the original score.
The problem is exposed http://gcc.gnu.org/viewcvs?root=gcc&view=rev&rev=175474
With GCC r175473
--------------------------
gcc -O3 -march=amdfam10 *.c -o Scimark175473 -lm
vekumar@pcedinar5:/local/home/vekumar/SciMark2_bench/SciMark2> ./Scimark175473
** **
** SciMark2 Numeric Benchmark, see http://math.nist.gov/scimark **
** for details. (Results can be submitted to pozo@nist.gov) **
** **
Using 2.00 seconds min time per kenel.
Composite Score: 99.67
FFT Mflops: 498.35 (N=1024)
With GCC r175474
-------------------------
gcc -O3 -march=amdfam10 *.c -o Scimark175474 -lm
vekumar@pcedinar5:/local/home/vekumar/SciMark2_bench/SciMark2> ./Scimark175474
** **
** SciMark2 Numeric Benchmark, see http://math.nist.gov/scimark **
** for details. (Results can be submitted to pozo@nist.gov) **
** **
Using 2.00 seconds min time per kenel.
Composite Score: 7.73
FFT Mflops: 38.66 (N=1024)
^ permalink raw reply [flat|nested] 4+ messages in thread
* [Bug tree-optimization/53397] Scimark performance drops by 10x times when compiled -O3 -march=amdfam10 due to generation more prefecthes
2012-05-18 12:07 [Bug tree-optimization/53397] New: Scimark performance drops by 10x times when compiled -O3 -march=amdfam10 due to generation more prefecthes venkataramanan.kumar at amd dot com
@ 2012-05-18 12:10 ` venkataramanan.kumar at amd dot com
2012-05-18 12:16 ` rguenth at gcc dot gnu.org
2012-10-09 15:55 ` venkataramanan.kumar at amd dot com
2 siblings, 0 replies; 4+ messages in thread
From: venkataramanan.kumar at amd dot com @ 2012-05-18 12:10 UTC (permalink / raw)
To: gcc-bugs
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=53397
Venkataramanan <venkataramanan.kumar at amd dot com> changed:
What |Removed |Added
----------------------------------------------------------------------------
Target| |x86_64-unknown-linux-gnu
CC| |rguenth at gcc dot gnu.org
Host| |x86_64-unknown-linux-gnu
Build| |x86_64-unknown-linux-gnu
Severity|normal |major
^ permalink raw reply [flat|nested] 4+ messages in thread
* [Bug tree-optimization/53397] Scimark performance drops by 10x times when compiled -O3 -march=amdfam10 due to generation more prefecthes
2012-05-18 12:07 [Bug tree-optimization/53397] New: Scimark performance drops by 10x times when compiled -O3 -march=amdfam10 due to generation more prefecthes venkataramanan.kumar at amd dot com
2012-05-18 12:10 ` [Bug tree-optimization/53397] " venkataramanan.kumar at amd dot com
@ 2012-05-18 12:16 ` rguenth at gcc dot gnu.org
2012-10-09 15:55 ` venkataramanan.kumar at amd dot com
2 siblings, 0 replies; 4+ messages in thread
From: rguenth at gcc dot gnu.org @ 2012-05-18 12:16 UTC (permalink / raw)
To: gcc-bugs
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=53397
Richard Guenther <rguenth at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Status|UNCONFIRMED |NEW
Last reconfirmed| |2012-05-18
Version|tree-ssa |4.7.1
Ever Confirmed|0 |1
--- Comment #1 from Richard Guenther <rguenth at gcc dot gnu.org> 2012-05-18 12:11:07 UTC ---
Confirmed.
^ permalink raw reply [flat|nested] 4+ messages in thread
* [Bug tree-optimization/53397] Scimark performance drops by 10x times when compiled -O3 -march=amdfam10 due to generation more prefecthes
2012-05-18 12:07 [Bug tree-optimization/53397] New: Scimark performance drops by 10x times when compiled -O3 -march=amdfam10 due to generation more prefecthes venkataramanan.kumar at amd dot com
2012-05-18 12:10 ` [Bug tree-optimization/53397] " venkataramanan.kumar at amd dot com
2012-05-18 12:16 ` rguenth at gcc dot gnu.org
@ 2012-10-09 15:55 ` venkataramanan.kumar at amd dot com
2 siblings, 0 replies; 4+ messages in thread
From: venkataramanan.kumar at amd dot com @ 2012-10-09 15:55 UTC (permalink / raw)
To: gcc-bugs
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=53397
Venkataramanan <venkataramanan.kumar at amd dot com> changed:
What |Removed |Added
----------------------------------------------------------------------------
Status|NEW |RESOLVED
Resolution| |FIXED
--- Comment #2 from Venkataramanan <venkataramanan.kumar at amd dot com> 2012-10-09 15:55:04 UTC ---
Fixed.
http://gcc.gnu.org/viewcvs?view=revision&revision=192261
^ permalink raw reply [flat|nested] 4+ messages in thread
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2012-05-18 12:07 [Bug tree-optimization/53397] New: Scimark performance drops by 10x times when compiled -O3 -march=amdfam10 due to generation more prefecthes venkataramanan.kumar at amd dot com
2012-05-18 12:10 ` [Bug tree-optimization/53397] " venkataramanan.kumar at amd dot com
2012-05-18 12:16 ` rguenth at gcc dot gnu.org
2012-10-09 15:55 ` venkataramanan.kumar at amd dot com
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