[Bug target/53659] New: ARM: Using -mcpu=cortex-a9 option results in bad performance for Cortex-A9 processor in C-Ray phoronix benchmark

[Bug target/53659] New: ARM: Using -mcpu=cortex-a9 option results in bad performance for Cortex-A9 processor in C-Ray phoronix benchmark

[siarhei.siamashka at gmail dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=53659

             Bug #: 53659
           Summary: ARM: Using -mcpu=cortex-a9 option results in bad
                    performance for Cortex-A9 processor in C-Ray phoronix
                    benchmark
    Classification: Unclassified
           Product: gcc
           Version: 4.7.0
            Status: UNCONFIRMED
          Severity: enhancement
          Priority: P3
         Component: target
        AssignedTo: unassigned@gcc.gnu.org
        ReportedBy: siarhei.siamashka@gmail.com


gcc version 4.7.0
--with-arch=armv7-a --with-float=hard --with-fpu=neon --with-mode=thumb

$ cd /tmp
$ wget http://www.phoronix-test-suite.com/benchmark-files/c-ray-1.1.tar.gz
$ tar -xzf c-ray-1.1.tar.gz
$ cd c-ray-1.1

$ make clean && make
gcc -O3 -ffast-math   -c -o c-ray-mt.o c-ray-mt.c
gcc -o c-ray-mt c-ray-mt.o -lm -lpthread
$ ./c-ray-mt -t 32 -s 160x120 -r 8 -i sphfract -o output.ppm
c-ray-mt v1.1
Rendering took: 6 seconds (6683 milliseconds)

$ sed -i "s,-O3,-O3 -mcpu=cortex-a9,g" Makefile

$ make clean && make
gcc -O3 -mcpu=cortex-a9 -ffast-math   -c -o c-ray-mt.o c-ray-mt.c
gcc -o c-ray-mt c-ray-mt.o -lm -lpthread
$ ./c-ray-mt -t 32 -s 160x120 -r 8 -i sphfract -o output.ppm
c-ray-mt v1.1
Rendering took: 7 seconds (7906 milliseconds)

Comparing to the default -march=armv7-a configuration, -mcpu=cortex-a9 caused a
~18% slowdown (7906 milliseconds vs. 6683 milliseconds). The test was run on a
dual-core ARM Cortex-A9 @1.2GHz

[Bug target/53659] ARM: Using -mcpu=cortex-a9 option results in bad performance for Cortex-A9 processor in C-Ray phoronix benchmark

[rearnsha at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=53659

Richard Earnshaw <rearnsha at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Target|                            |arm

--- Comment #1 from Richard Earnshaw <rearnsha at gcc dot gnu.org> 2012-07-10 08:48:24 UTC ---
What platform are you running on (GCC configuration)?

Please can you do some profiling and try to identify where the slowdown is
coming from.  We need more information if we are to progress this.

[Bug target/53659] ARM: Using -mcpu=cortex-a9 option results in bad performance for Cortex-A9 processor in C-Ray phoronix benchmark

[ramana at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=53659

Ramana Radhakrishnan <ramana at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |WAITING
   Last reconfirmed|                            |2012-07-12
                 CC|                            |ramana at gcc dot gnu.org
     Ever Confirmed|0                           |1