https://gcc.gnu.org/bugzilla/show_bug.cgi?id=65450
Bug ID: 65450
Summary: [5.0 Regression]: Unaligned access with -O3 -mtune=k8
Product: gcc
Version: 5.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: fortran
Assignee: unassigned at gcc dot gnu.org
Reporter: ubizjak at gmail dot com
The compiler generates unaligned access for Polyhedron channel.f90 test when
compiled with -O2 -mtune=k8:
/home/uros/gcc-build/gcc/gfortran -B/home/uros/gcc-build/gcc
-B/home/uros/gcc-build/x86_64-unknown-linux-gnu/libgfortran/
-B/home/uros/gcc-build/x86_64-unknown-linux-gnu/libquadmath/.libs
-L/home/uros/gcc-build/x86_64-unknown-linux-gnu/libgfortran/.libs
-L-L/home/uros/gcc-build/x86_64-unknown-linux-gnu/libquadmath/.libs -O2
-ffast-math -mtune=k8 channel.f90
LD_LIBRARY_PATH=/home/uros/gcc-build/gcc:/home/uros/gcc-build/x86_64-unknown-linux-gnu/libgfortran/.libs:/home/uros/gcc-build/x86_64-unknown-linux-gnu/libquadmath/.libs
./a.out
...
Program received signal SIGSEGV: Segmentation fault - invalid memory reference.
Backtrace for this error:
#0 0x2AC9058B3C27
#1 0x2AC9058B2E20
#2 0x31CDC3002F
#3 0x402AFB in ddx at channel.f90:247
Segmentation fault
(gdb) r
...
Program received signal SIGSEGV, Segmentation fault.
0x0000000000402afb in ddx (array=..., __result=...) at channel.f90:247
247 ddx(2:I-1,1:J) = array(3:I,1:J)-array(1:I-2,1:J) ! interior
points
(gdb) bt
#0 0x0000000000402afb in ddx (array=..., __result=...) at channel.f90:247
#1 sw () at channel.f90:148
#2 0x0000000000404cfd in main (argc=<optimized out>, argv=<optimized out>) at
channel.f90:234
#3 0x00000031cdc1d9f4 in __libc_start_main () from /lib64/libc.so.6
#4 0x0000000000400909 in _start ()
(gdb) disass
...
0x0000000000402acc <+7644>: movaps %xmm4,-0x20(%rdx)
0x0000000000402ad0 <+7648>: movlpd -0x10(%rax),%xmm0
0x0000000000402ad5 <+7653>: movhpd -0x8(%rax),%xmm0
0x0000000000402ada <+7658>: movapd %xmm0,%xmm4
0x0000000000402ade <+7662>: subpd %xmm3,%xmm4
0x0000000000402ae2 <+7666>: movaps %xmm4,-0x10(%rdx)
0x0000000000402ae6 <+7670>: cmp $0xf4,%rdi
0x0000000000402aed <+7677>: jne 0x402a71 <sw+7553>
0x0000000000402aef <+7679>: lea 0x20(%rcx),%rdi
0x0000000000402af3 <+7683>: add $0x20,%rax
0x0000000000402af7 <+7687>: add $0x20,%rdx
=> 0x0000000000402afb <+7691>: movapd -0x20(%rax),%xmm3
0x0000000000402b00 <+7696>: mov $0xf6,%r11d
0x0000000000402b06 <+7702>: xor %ecx,%ecx
0x0000000000402b08 <+7704>: movapd %xmm3,%xmm4
0x0000000000402b0c <+7708>: subpd %xmm0,%xmm4
...
(gdb) p/x $rax
$3 = 0x8c5a38
The failure can also be seen on SUSE gcc tester [1].
[1] http://gcc.opensuse.org/c++bench/polyhedron/polyhedron-performance-latest
