https://gcc.gnu.org/bugzilla/show_bug.cgi?id=126283
Bug ID: 126283
Summary: Extra register move in __builtin_bswap16 on x86-64
Product: gcc
Version: 15.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: target
Assignee: unassigned at gcc dot gnu.org
Reporter: arthur.j.odwyer at gmail dot com
Target Milestone: ---
// https://godbolt.org/z/9vozroWMn
int f(short x) {
return __builtin_bswap16(x);
}
GCC 14.4 (x86-64) produces:
rolw $8, %di
movzwl %di, %eax
ret
GCC 15.1 (x86-64), and trunk as of this writing, produces one additional
register move:
movl %edi, %eax
rolw $8, %ax
movzwl %ax, %eax
ret
Doesn't have any business impact, obviously, but I thought it was strange that
it would have regressed, and might be worth tracking down why.
