https://gcc.gnu.org/bugzilla/show_bug.cgi?id=87623
Bug ID: 87623
Summary: bytes swapped in register when comparing cause fail
when comiled with -O1 or higher
Product: gcc
Version: 8.2.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: tree-optimization
Assignee: unassigned at gcc dot gnu.org
Reporter: george.thopas at gmail dot com
Target Milestone: ---
Target: x86_64-pc-linux-gnu
Build: gcc version 8.2.0 (Gentoo 8.2.0-r3 p1.4)
- Compare of two single char fields in two structures with different
scalar_storage_order order goes wrong. Reduced test case below.
- Observed in 6.3.1 and reproducible in 8.2.0 , Target x86_64-pc-linux-gnu
---[howto]------------------------------------
passed test:
$ gcc -O0 test.c
$ ./a.out
failed test:
$ gcc -O1 test.c
$ ./a.out
Aborted
-- [code]----------------------------------------
/* test.c */
#include <stdlib.h>
struct be {
unsigned short pad[1];
unsigned char a;
unsigned char b;
} __attribute__((scalar_storage_order("big-endian")));
typedef struct be t_be;
struct le {
unsigned short pad[3];
unsigned char a;
unsigned char b;
};
typedef struct le t_le;
int a_or_b_different(t_be *x,t_le *y)
{
return ((x->a != y->a) ||
(x->b != y->b));
}
int main(int argc,char *argv[])
{
t_be x = { .a=1, .b=2 };
t_le y = { .a=1, .b=2 };
if (a_or_b_different(&x,&y))
abort();
return 0;
}
----------------------------------------------------------------------
jbeu@bt9923 ~ $ gcc -v -O1 test.c
Using built-in specs.
COLLECT_GCC=gcc
COLLECT_LTO_WRAPPER=/usr/libexec/gcc/x86_64-pc-linux-gnu/8.2.0/lto-wrapper
Target: x86_64-pc-linux-gnu
Configured with:
/var/tmp/portage/sys-devel/gcc-8.2.0-r3/work/gcc-8.2.0/configure
--host=x86_64-pc-linux-gnu --build=x86_64-pc-linux-gnu --prefix=/usr
--bindir=/usr/x86_64-pc-linux-gnu/gcc-bin/8.2.0
--includedir=/usr/lib/gcc/x86_64-pc-linux-gnu/8.2.0/include
--datadir=/usr/share/gcc-data/x86_64-pc-linux-gnu/8.2.0
--mandir=/usr/share/gcc-data/x86_64-pc-linux-gnu/8.2.0/man
--infodir=/usr/share/gcc-data/x86_64-pc-linux-gnu/8.2.0/info
--with-gxx-include-dir=/usr/lib/gcc/x86_64-pc-linux-gnu/8.2.0/include/g++-v8
--with-python-dir=/share/gcc-data/x86_64-pc-linux-gnu/8.2.0/python
--enable-languages=c,c++,fortran --enable-obsolete --enable-secureplt
--disable-werror --with-system-zlib --enable-nls --without-included-gettext
--enable-checking=release --with-bugurl=https://bugs.gentoo.org/
--with-pkgversion='Gentoo 8.2.0-r3 p1.4' --disable-esp --enable-libstdcxx-time
--enable-shared --enable-threads=posix --enable-__cxa_atexit
--enable-clocale=gnu --enable-multilib --with-multilib-list=m32,m64
--disable-altivec --disable-fixed-point --enable-targets=all --enable-libgomp
--disable-libmudflap --disable-libssp --disable-libmpx --disable-systemtap
--enable-vtable-verify --enable-libvtv --enable-lto --without-isl
--enable-libsanitizer --enable-default-pie --enable-default-ssp
Thread model: posix
gcc version 8.2.0 (Gentoo 8.2.0-r3 p1.4)
COLLECT_GCC_OPTIONS='-v' '-O1' '-mtune=generic' '-march=x86-64'
/usr/libexec/gcc/x86_64-pc-linux-gnu/8.2.0/cc1 -quiet -v bug.c -quiet
-dumpbase bug.c -mtune=generic -march=x86-64 -auxbase bug -O1 -version -o
/tmp/ccdpdLOi.s
GNU C17 (Gentoo 8.2.0-r3 p1.4) version 8.2.0 (x86_64-pc-linux-gnu)
compiled by GNU C version 8.2.0, GMP version 6.1.2, MPFR version 4.0.1,
MPC version 1.1.0, isl version none
GGC heuristics: --param ggc-min-expand=100 --param ggc-min-heapsize=131072
ignoring nonexistent directory "/usr/local/include"
ignoring nonexistent directory
"/usr/lib/gcc/x86_64-pc-linux-gnu/8.2.0/../../../../x86_64-pc-linux-gnu/include"
#include "..." search starts here:
#include <...> search starts here:
/usr/lib/gcc/x86_64-pc-linux-gnu/8.2.0/include
/usr/lib/gcc/x86_64-pc-linux-gnu/8.2.0/include-fixed
/usr/include
End of search list.
GNU C17 (Gentoo 8.2.0-r3 p1.4) version 8.2.0 (x86_64-pc-linux-gnu)
compiled by GNU C version 8.2.0, GMP version 6.1.2, MPFR version 4.0.1,
MPC version 1.1.0, isl version none
GGC heuristics: --param ggc-min-expand=100 --param ggc-min-heapsize=131072
Compiler executable checksum: 91d4bd0e38b68a0f50315f89ba003c77
COLLECT_GCC_OPTIONS='-v' '-O1' '-mtune=generic' '-march=x86-64'
/usr/lib/gcc/x86_64-pc-linux-gnu/8.2.0/../../../../x86_64-pc-linux-gnu/bin/as
-v --64 -o /tmp/ccsw11XW.o /tmp/ccdpdLOi.s
GNU assembler version 2.31.1 (x86_64-pc-linux-gnu) using BFD version (Gentoo
2.31.1 p3) 2.31.1
COMPILER_PATH=/usr/libexec/gcc/x86_64-pc-linux-gnu/8.2.0/:/usr/libexec/gcc/x86_64-pc-linux-gnu/8.2.0/:/usr/libexec/gcc/x86_64-pc-linux-gnu/:/usr/lib/gcc/x86_64-pc-linux-gnu/8.2.0/:/usr/lib/gcc/x86_64-pc-linux-gnu/:/usr/lib/gcc/x86_64-pc-linux-gnu/8.2.0/../../../../x86_64-pc-linux-gnu/bin/
LIBRARY_PATH=/usr/lib/gcc/x86_64-pc-linux-gnu/8.2.0/:/usr/lib/gcc/x86_64-pc-linux-gnu/8.2.0/../../../../lib64/:/lib/../lib64/:/usr/lib/../lib64/:/usr/lib/gcc/x86_64-pc-linux-gnu/8.2.0/../../../../x86_64-pc-linux-gnu/lib/:/usr/lib/gcc/x86_64-pc-linux-gnu/8.2.0/../../../:/lib/:/usr/lib/
COLLECT_GCC_OPTIONS='-v' '-O1' '-mtune=generic' '-march=x86-64'
/usr/libexec/gcc/x86_64-pc-linux-gnu/8.2.0/collect2 -plugin
/usr/libexec/gcc/x86_64-pc-linux-gnu/8.2.0/liblto_plugin.so
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/usr/lib/gcc/x86_64-pc-linux-gnu/8.2.0/crtbeginS.o
-L/usr/lib/gcc/x86_64-pc-linux-gnu/8.2.0
-L/usr/lib/gcc/x86_64-pc-linux-gnu/8.2.0/../../../../lib64 -L/lib/../lib64
-L/usr/lib/../lib64
-L/usr/lib/gcc/x86_64-pc-linux-gnu/8.2.0/../../../../x86_64-pc-linux-gnu/lib
-L/usr/lib/gcc/x86_64-pc-linux-gnu/8.2.0/../../.. /tmp/ccsw11XW.o -lgcc
--as-needed -lgcc_s --no-as-needed -lc -lgcc --as-needed -lgcc_s --no-as-needed
/usr/lib/gcc/x86_64-pc-linux-gnu/8.2.0/crtendS.o
/usr/lib/gcc/x86_64-pc-linux-gnu/8.2.0/../../../../lib64/crtn.o
COLLECT_GCC_OPTIONS='-v' '-O1' '-mtune=generic' '-march=x86-64'
