https://gcc.gnu.org/bugzilla/show_bug.cgi?id=85096
Bug ID: 85096
Summary: [6/7/8 Regression] Unnecessary(?) MOV instructions for
int128 addition
Product: gcc
Version: 8.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c
Assignee: unassigned at gcc dot gnu.org
Reporter: redi at gcc dot gnu.org
CC: uros at gcc dot gnu.org, vmakarov at gcc dot gnu.org
Target Milestone: ---
__uint128_t add128(__uint128_t a, __uint128_t b) {
return a + b;
}
GCC with -O3 produces:
mov r9, rdi # a, a
mov r10, rsi # a, a
add r9, rdx # a, b
adc r10, rcx # a, b
mov rax, r9 # tmp93, a
mov rdx, r10 #, a
ret
GCC 4.8.5 produced:
mov rax, rdx # D.1732, b
mov rdx, rcx # D.1732, b
add rax, rdi # D.1732, a
adc rdx, rsi # D.1732, a
ret
Clang produces:
add rdi, rdx
adc rsi, rcx
mov rax, rdi
mov rdx, rsi
ret
and ICC:
add rdi, rdx #3.14
mov rax, rdi #3.14
adc rsi, rcx #3.14
mov rdx, rsi #3.14
ret #3.14
I don't know which component this should be, but Jakub suggested to CC Vlad and
Uros, so maybe one of you can re-assign it to the right component.
