https://gcc.gnu.org/bugzilla/show_bug.cgi?id=99520
Bug ID: 99520
Summary: Failure to detect bswap pattern
Product: gcc
Version: unknown
Status: UNCONFIRMED
Keywords: missed-optimization
Severity: normal
Priority: P3
Component: middle-end
Assignee: unassigned at gcc dot gnu.org
Reporter: ktkachov at gcc dot gnu.org
Target Milestone: ---
#include <stdint.h>
uint32_t endian_fix32( uint32_t x ){
return (x<<24) + ((x<<8)&0xff0000) + ((x>>8)&0xff00) + (x>>24);
}
For aarch64 clang manages to optimise it to:
endian_fix32(unsigned int): // @endian_fix32(unsigned int)
rev w0, w0
ret
GCC doesn't:
endian_fix32(unsigned int):
lsl w1, w0, 8
lsr w2, w0, 8
and w2, w2, 65280
lsr w3, w0, 24
and w1, w1, 16711680
add w0, w3, w0, lsl 24
orr w1, w1, w2
add w0, w1, w0
ret
Is there something missing in the bswap pass?
