https://gcc.gnu.org/bugzilla/show_bug.cgi?id=93990
Bug ID: 93990
Summary: [x86] Silly code generation for
_addcarry_u32/_addcarry_u64
Product: gcc
Version: 9.2.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: target
Assignee: unassigned at gcc dot gnu.org
Reporter: lloyd at randombit dot net
Target Milestone: ---
Bug 67317 has regressed, starting in GCC 6
Same test case as 67317:
#include <x86intrin.h>
#include <stdint.h>
unsigned long long testcarry(unsigned long long a, unsigned long long
b, unsigned long long c, unsigned long long d)
{
unsigned long long result0, result1;
_addcarry_u64(_addcarry_u64(0, a, c, &result0), b, d,
&result1);
return result0 ^ result1;
}
GCC 5.4.1 (only) produces the expected output
.cfi_startproc
addq %rdi, %rdx # a, tmp99
adcq %rsi, %rcx # b, tmp107
movq %rdx, %rax # tmp99, D.28638
xorq %rcx, %rax # tmp107, D.28638
ret
.cfi_endproc
GCC 6.4.1, 7.4.1, 8.3.0 and 9.2.0 all produce variations on this [GCC 9.2.0
output here]:
.cfi_startproc
subq $40, %rsp #,
.cfi_def_cfa_offset 48
# adx.cpp:5: {
movq %fs:40, %rax # MEM[(<address-space-1> long unsigned int
*)40B], tmp107
movq %rax, 24(%rsp) # tmp107, D.33144
xorl %eax, %eax # tmp107
# /usr/lib/gcc/x86_64-pc-linux-gnu/9.2.0/include/adxintrin.h:69: return
__builtin_ia32_addcarryx_u64 (__CF, __X, __Y, __P);
addq %rdx, %rdi # tmp105, tmp93
movq %rsi, %rax # tmp104, tmp104
setc %r8b #, _12
movq %rdi, 8(%rsp) # tmp93,
addb $-1, %r8b #, _12
adcq %rcx, %rax # tmp106, tmp104
movq %rax, 16(%rsp) # tmp97,
# adx.cpp:8: return result0 ^ result1;
xorq %rdi, %rax # tmp93, <retval>
# adx.cpp:9: }
movq 24(%rsp), %rdx # D.33144, tmp109
xorq %fs:40, %rdx # MEM[(<address-space-1> long unsigned int
*)40B], tmp109
jne .L5 #,
addq $40, %rsp #,
.cfi_remember_state
.cfi_def_cfa_offset 8
ret
All were compiled with -O3. I checked 9.2.0 output with -O and -O2 as well,
with no significant change.
