https://gcc.gnu.org/bugzilla/show_bug.cgi?id=104439
Bug ID: 104439
Summary: arm crc feature not enabled in assembly for function
with crc target attribute
Product: gcc
Version: 11.2.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c
Assignee: unassigned at gcc dot gnu.org
Reporter: ebiggers3 at gmail dot com
Target Milestone: ---
Minimized reproducer:
void some_other_function(void) { }
unsigned int __attribute__((target("arch=armv8-a+crc")))
crc32_arm(unsigned int crc, const unsigned char *data, unsigned long size)
{
for (unsigned long i = 0; i < size; i++)
crc = __builtin_arm_crc32b(crc, data[i]);
return crc;
}
#pragma GCC push_options
#pragma GCC pop_options
$ arm-linux-gnueabihf-gcc -c test.c
/tmp/ccCUwib8.s: Assembler messages:
/tmp/ccCUwib8.s:58: Error: selected processor does not support `crc32b
r3,r3,r2' in ARM mode
$ arm-linux-gnueabihf-gcc --version
arm-linux-gnueabihf-gcc (GCC) 11.2.0
The crc32_arm() function is compiled with crc instructions enabled, and gcc is
emitting assembly code using them. However, gcc isn't emitting the directives
that tell the assembler to allow these instructions.
The problem goes away if either some_other_function() is deleted, or if the
"GCC push_options" and "GCC pop_options" pair is deleted. I don't see any
logical reason why either change would make a difference.
(The original, non-minimized code this problem was seen on can be found at
https://github.com/ebiggers/libdeflate/blob/v1.9/lib/arm/crc32_impl.h#L75.)
