https://gcc.gnu.org/bugzilla/show_bug.cgi?id=96939
Bug ID: 96939
Summary: LTO vs. different arm arch options
Product: gcc
Version: 11.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: target
Assignee: unassigned at gcc dot gnu.org
Reporter: jakub at gcc dot gnu.org
Target Milestone: ---
$ cat a1.c
extern unsigned crc (unsigned, const void *);
typedef unsigned (*fnptr) (unsigned, const void *);
volatile fnptr fn;
int
main ()
{
fn = crc;
return 0;
}
$ cat a2.c
#include <arm_acle.h>
unsigned
crc (unsigned x, const void *y)
{
return __crc32cw (x, *(unsigned *) y);
}
$ ./xgcc -B ./ -O2 -march=armv7-a -mfpu=vfpv3-d16 -mtune=generic-armv7-a
-mabi=aapcs-linux -mfloat-abi=hard -c a1.c -flto
$ ./xgcc -B ./ -O2 -march=armv7-a -mfpu=vfpv3-d16 -mtune=generic-armv7-a
-mabi=aapcs-linux -mfloat-abi=hard -march=armv8-a+crc -c a2.c -flto
$ ./xgcc -B ./ -r -march=armv7-a -mfpu=vfpv3-d16 -mtune=generic-armv7-a
-mabi=aapcs-linux -mfloat-abi=hard -o a a1.o a2.o -flto
results in:
a2.c: In function ‘crc’:
a2.c:6:10: error: this builtin is not supported for this target
6 | return __crc32cw (x, *(unsigned *) y);
| ^
Adding
__attribute__((target ("arch=armv8-a+crc")))
to crc function doesn't help.
In gdb I see
(gdb) p global_options.x_arm_arch_string
$2 = 0x2a38d50 "armv8-a+crc+simd"
(gdb) p arm_arch_crc
$3 = 0
which means the function got proper target attribute even if it didn't have
one, TARGET_OPTIONS and the like, but arm_option_reconfigure_globals wasn't
really called when changing current function from the armv7 built one (or the
default) and the armv8-a+crc+simd one.
I'm afraid this makes LTO not work at all on arm when one mixes command line
options between TUs or uses target attribute.
