[Bug target/52736] New: [4.7 regression] miscompilation: store to aliased __m128d is 8 Bytes off

[Bug target/52736] New: [4.7 regression] miscompilation: store to aliased __m128d is 8 Bytes off

[kretz at kde dot org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=52736

             Bug #: 52736
           Summary: [4.7 regression] miscompilation: store to aliased
                    __m128d is 8 Bytes off
    Classification: Unclassified
           Product: gcc
           Version: 4.7.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: target
        AssignedTo: unassigned@gcc.gnu.org
        ReportedBy: kretz@kde.org


Created attachment 27007
  --> http://gcc.gnu.org/bugzilla/attachment.cgi?id=27007
testcase

The attached testcase fails when compiled with:
g++ -msse2 -O1 main.cpp

The first aliased store on line 35 stores to the second element in the vector
instead of the fist. The store on line 37 stores to the exact same location in
memory (which is the correct location for line 37).

Slight modification of the example can lead to the compiler optimizing the code
to use half vector loads, in which case it uses the correct one.

[Bug target/52736] [4.7 regression] miscompilation: store to aliased __m128d is 8 Bytes off

[rguenth at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=52736

Richard Guenther <rguenth at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |WAITING
   Last reconfirmed|                            |2012-03-27
     Ever Confirmed|0                           |1

--- Comment #1 from Richard Guenther <rguenth at gcc dot gnu.org> 2012-03-27 07:42:36 UTC ---
I cannot reproduce this on trunk.  What is your target?  Please provide the
output of the compiler command when you append 'v'.

[Bug target/52736] [4.7 regression] miscompilation: store to aliased __m128d is 8 Bytes off

[kretz at kde dot org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=52736

--- Comment #2 from Matthias Kretz <kretz at kde dot org> 2012-03-27 08:00:47 UTC ---
Using built-in specs.
COLLECT_GCC=/opt/gcc-4.7.0/bin/g++
COLLECT_LTO_WRAPPER=/opt/gcc-4.7.0/libexec/gcc/x86_64-linux-gnu/4.7.0/lto-wrapper
Target: x86_64-linux-gnu
Configured with: ./configure --prefix=/opt/gcc-4.7.0 --build=x86_64-linux-gnu
--host=x86_64-linux-gnu --enable-languages=c,c++,fortran
--with-gmp=/opt/gcc-4.7.0 --with-mpfr=/opt/gcc-4.7.0 --with-ppl=/opt/gcc-4.7.0
--with-cloog=/opt/gcc-4.7.0 --with-libelf=/opt/gcc-4.7.0
--with-mpc=/opt/gcc-4.7.0 --enable-lto
Thread model: posix
gcc version 4.7.0 (GCC) 
COLLECT_GCC_OPTIONS='-v' '-Wall' '-Wextra' '-msse2' '-O1' '-o' 'gcc-bug'
'-shared-libgcc' '-mtune=generic' '-march=x86-64'
 /opt/gcc-4.7.0/libexec/gcc/x86_64-linux-gnu/4.7.0/cc1plus -quiet -v
-imultiarch x86_64-linux-gnu -D_GNU_SOURCE gcc-bug.cpp -quiet -dumpbase
gcc-bug.cpp -msse2 -mtune=generic -march=x86-64 -auxbase gcc-bug -O1 -Wall
-Wextra -version -o /tmp/ccfqD6uO.s
GNU C++ (GCC) version 4.7.0 (x86_64-linux-gnu)
        compiled by GNU C version 4.7.0, GMP version 5.0.4, MPFR version 3.1.0,
MPC version 0.9
GGC heuristics: --param ggc-min-expand=100 --param ggc-min-heapsize=131072
ignoring nonexistent directory "/usr/local/include/x86_64-linux-gnu"
ignoring nonexistent directory
"/opt/gcc-4.7.0/lib/gcc/x86_64-linux-gnu/4.7.0/../../../../x86_64-linux-gnu/include"
#include "..." search starts here:
#include <...> search starts here:
 /opt/gcc-4.7.0/lib/gcc/x86_64-linux-gnu/4.7.0/../../../../include/c++/4.7.0

/opt/gcc-4.7.0/lib/gcc/x86_64-linux-gnu/4.7.0/../../../../include/c++/4.7.0/x86_64-linux-gnu

/opt/gcc-4.7.0/lib/gcc/x86_64-linux-gnu/4.7.0/../../../../include/c++/4.7.0/backward
 /opt/gcc-4.7.0/lib/gcc/x86_64-linux-gnu/4.7.0/include
 /usr/local/include
 /opt/gcc-4.7.0/include
 /opt/gcc-4.7.0/lib/gcc/x86_64-linux-gnu/4.7.0/include-fixed
 /usr/include/x86_64-linux-gnu
 /usr/include
End of search list.
GNU C++ (GCC) version 4.7.0 (x86_64-linux-gnu)
        compiled by GNU C version 4.7.0, GMP version 5.0.4, MPFR version 3.1.0,
MPC version 0.9
GGC heuristics: --param ggc-min-expand=100 --param ggc-min-heapsize=131072
Compiler executable checksum: 1ed577a2a8985e4282c7df02a5129e15
COLLECT_GCC_OPTIONS='-v' '-Wall' '-Wextra' '-msse2' '-O1' '-o' 'gcc-bug'
'-shared-libgcc' '-mtune=generic' '-march=x86-64'

/opt/gcc-4.7.0/lib/gcc/x86_64-linux-gnu/4.7.0/../../../../x86_64-linux-gnu/bin/as
--64 -o /tmp/ccJeVBlU.o /tmp/ccfqD6uO.s
COMPILER_PATH=/opt/gcc-4.7.0/libexec/gcc/x86_64-linux-gnu/4.7.0/:/opt/gcc-4.7.0/libexec/gcc/x86_64-linux-gnu/4.7.0/:/opt/gcc-4.7.0/libexec/gcc/x86_64-linux-gnu/:/opt/gcc-4.7.0/lib/gcc/x86_64-linux-gnu/4.7.0/:/opt/gcc-4.7.0/lib/gcc/x86_64-linux-gnu/:/opt/gcc-4.7.0/lib/gcc/x86_64-linux-gnu/4.7.0/../../../../x86_64-linux-gnu/bin/
LIBRARY_PATH=/opt/gcc-4.7.0/lib/gcc/x86_64-linux-gnu/4.7.0/:/opt/gcc-4.7.0/lib/gcc/x86_64-linux-gnu/4.7.0/../../../../lib64/:/lib/x86_64-linux-gnu/:/lib/../lib64/:/usr/lib/x86_64-linux-gnu/:/opt/gcc-4.7.0/lib/gcc/x86_64-linux-gnu/4.7.0/../../../../x86_64-linux-gnu/lib/:/opt/gcc-4.7.0/lib/gcc/x86_64-linux-gnu/4.7.0/../../../:/lib/:/usr/lib/
COLLECT_GCC_OPTIONS='-v' '-Wall' '-Wextra' '-msse2' '-O1' '-o' 'gcc-bug'
'-shared-libgcc' '-mtune=generic' '-march=x86-64'
 /opt/gcc-4.7.0/libexec/gcc/x86_64-linux-gnu/4.7.0/collect2 --eh-frame-hdr -m
elf_x86_64 -dynamic-linker /lib64/ld-linux-x86-64.so.2 -o gcc-bug
/usr/lib/x86_64-linux-gnu/crt1.o /usr/lib/x86_64-linux-gnu/crti.o
/opt/gcc-4.7.0/lib/gcc/x86_64-linux-gnu/4.7.0/crtbegin.o
-L/opt/gcc-4.7.0/lib/gcc/x86_64-linux-gnu/4.7.0
-L/opt/gcc-4.7.0/lib/gcc/x86_64-linux-gnu/4.7.0/../../../../lib64
-L/lib/x86_64-linux-gnu -L/lib/../lib64 -L/usr/lib/x86_64-linux-gnu
-L/opt/gcc-4.7.0/lib/gcc/x86_64-linux-gnu/4.7.0/../../../../x86_64-linux-gnu/lib
-L/opt/gcc-4.7.0/lib/gcc/x86_64-linux-gnu/4.7.0/../../.. /tmp/ccJeVBlU.o
-lstdc++ -lm -lgcc_s -lgcc -lc -lgcc_s -lgcc
/opt/gcc-4.7.0/lib/gcc/x86_64-linux-gnu/4.7.0/crtend.o
/usr/lib/x86_64-linux-gnu/crtn.o


I will also add the output of -S. Line 16 is the broken one. Instead of "movsd
%xmm0, 8(%rsp)" it should be "movsd %xmm0, %(rsp)".

[Bug target/52736] [4.7 regression] miscompilation: store to aliased __m128d is 8 Bytes off

[kretz at kde dot org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=52736

--- Comment #3 from Matthias Kretz <kretz at kde dot org> 2012-03-27 08:01:23 UTC ---
Created attachment 27010
  --> http://gcc.gnu.org/bugzilla/attachment.cgi?id=27010
-S output

[Bug target/52736] [4.7 regression] miscompilation: store to aliased __m128d is 8 Bytes off

[jakub at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=52736

Jakub Jelinek <jakub at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |jakub at gcc dot gnu.org

--- Comment #4 from Jakub Jelinek <jakub at gcc dot gnu.org> 2012-03-27 13:54:34 UTC ---
Looking at it.

[Bug target/52736] [4.5/4.6/4.7/4.8 Regression] miscompilation: store to aliased __m128d is 8 Bytes off

[jakub at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=52736

Jakub Jelinek <jakub at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|WAITING                     |ASSIGNED
         AssignedTo|unassigned at gcc dot       |jakub at gcc dot gnu.org
                   |gnu.org                     |
   Target Milestone|---                         |4.5.4
            Summary|[4.7 regression]            |[4.5/4.6/4.7/4.8
                   |miscompilation: store to    |Regression] miscompilation:
                   |aliased __m128d is 8 Bytes  |store to aliased __m128d is
                   |off                         |8 Bytes off

--- Comment #5 from Jakub Jelinek <jakub at gcc dot gnu.org> 2012-03-27 14:51:17 UTC ---
The bug seems to have been introduced in gcc 4.0.

[Bug target/52736] [4.5/4.6/4.7/4.8 Regression] miscompilation: store to aliased __m128d is 8 Bytes off

[jakub at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=52736

--- Comment #6 from Jakub Jelinek <jakub at gcc dot gnu.org> 2012-03-27 14:52:13 UTC ---
Created attachment 27015
  --> http://gcc.gnu.org/bugzilla/attachment.cgi?id=27015
gcc48-pr52736.patch

Untested fix.

[Bug target/52736] [4.5/4.6/4.7/4.8 Regression] miscompilation: store to aliased __m128d is 8 Bytes off

[kretz at kde dot org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=52736

--- Comment #7 from Matthias Kretz <kretz at kde dot org> 2012-03-27 16:58:42 UTC ---
With the patch my unit test passes again with 4.7.0. In my code I don't see any
regressions from the patch.

[Bug target/52736] [4.5/4.6/4.7/4.8 Regression] miscompilation: store to aliased __m128d is 8 Bytes off

[kretz at kde dot org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=52736

--- Comment #8 from Matthias Kretz <kretz at kde dot org> 2012-03-27 17:02:59 UTC ---
I might have been too fast. On the Intel Sandy-Bridge, where I debugged the
problem first things have improved. On an AMD Magny-Cours I get lots of
failures. I need to investigate whether I broke something unrelated to this
patch.

[Bug target/52736] [4.5/4.6/4.7/4.8 Regression] miscompilation: store to aliased __m128d is 8 Bytes off

[kretz at kde dot org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=52736

--- Comment #9 from Matthias Kretz <kretz at kde dot org> 2012-03-27 21:20:49 UTC ---
All good. The error is mine. I don't see any regressions from the use of the
patch.

[Bug target/52736] [4.5/4.6/4.7/4.8 Regression] miscompilation: store to aliased __m128d is 8 Bytes off

[jakub at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=52736

--- Comment #10 from Jakub Jelinek <jakub at gcc dot gnu.org> 2012-03-28 08:01:17 UTC ---
Author: jakub
Date: Wed Mar 28 08:01:00 2012
New Revision: 185904

URL: http://gcc.gnu.org/viewcvs?root=gcc&view=rev&rev=185904
Log:
    PR target/52736
    * config/i386/sse.md (sse2_loadlpd splitter): Use offset 0
    instead of 8 in adjust_address.

    * gcc.target/i386/pr52736.c: New test.

Added:
    trunk/gcc/testsuite/gcc.target/i386/pr52736.c
Modified:
    trunk/gcc/ChangeLog
    trunk/gcc/config/i386/sse.md
    trunk/gcc/testsuite/ChangeLog

[Bug target/52736] [4.5/4.6/4.7/4.8 Regression] miscompilation: store to aliased __m128d is 8 Bytes off

[jakub at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=52736

--- Comment #11 from Jakub Jelinek <jakub at gcc dot gnu.org> 2012-03-28 08:03:41 UTC ---
Author: jakub
Date: Wed Mar 28 08:03:11 2012
New Revision: 185905

URL: http://gcc.gnu.org/viewcvs?root=gcc&view=rev&rev=185905
Log:
    PR target/52736
    * config/i386/sse.md (sse2_loadlpd splitter): Use offset 0
    instead of 8 in adjust_address.

    * gcc.target/i386/pr52736.c: New test.

Added:
    branches/gcc-4_7-branch/gcc/testsuite/gcc.target/i386/pr52736.c
Modified:
    branches/gcc-4_7-branch/gcc/ChangeLog
    branches/gcc-4_7-branch/gcc/config/i386/sse.md
    branches/gcc-4_7-branch/gcc/testsuite/ChangeLog

[Bug target/52736] [4.5/4.6/4.7/4.8 Regression] miscompilation: store to aliased __m128d is 8 Bytes off

[jakub at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=52736

--- Comment #12 from Jakub Jelinek <jakub at gcc dot gnu.org> 2012-03-28 08:10:25 UTC ---
Author: jakub
Date: Wed Mar 28 08:09:55 2012
New Revision: 185906

URL: http://gcc.gnu.org/viewcvs?root=gcc&view=rev&rev=185906
Log:
    PR target/52736
    * config/i386/sse.md (sse2_loadlpd splitter): Use offset 0
    instead of 8 in adjust_address.

    * gcc.target/i386/pr52736.c: New test.

Added:
    branches/gcc-4_6-branch/gcc/testsuite/gcc.target/i386/pr52736.c
Modified:
    branches/gcc-4_6-branch/gcc/ChangeLog
    branches/gcc-4_6-branch/gcc/config/i386/sse.md
    branches/gcc-4_6-branch/gcc/testsuite/ChangeLog

[Bug target/52736] [4.5/4.6/4.7/4.8 Regression] miscompilation: store to aliased __m128d is 8 Bytes off

[jakub at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=52736

Jakub Jelinek <jakub at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|ASSIGNED                    |RESOLVED
         Resolution|                            |FIXED

--- Comment #13 from Jakub Jelinek <jakub at gcc dot gnu.org> 2012-03-28 08:15:36 UTC ---
Fixed for 4.6+ (note, even in 4.6 the bug is just latent).

[Bug target/52736] [4.5/4.6/4.7/4.8 Regression] miscompilation: store to aliased __m128d is 8 Bytes off

[kretz at kde dot org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=52736

--- Comment #14 from Matthias Kretz <kretz at kde dot org> 2012-03-28 09:03:05 UTC ---
Thanks! Great response time!

And yes, I started to notice the bug on 4.6.x now, too. In different unit
tests, though. I'll see if I can come up with a workaround for the "broken"
compilers.