[Bug target/110104] gcc produces sub-optimal code for _addcarry_u64 chain
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=110104
--- Comment #5 from Mason ---
FWIW, trunk (gcc14) translates testcase3 to the same code as the other
testcases, while remaining portable across all architectures:
$ gcc-trunk -O3 -march=bdver3 testcase3.c
typedef unsigned long long u64;
typedef unsigned __int128 u128;
void testcase3(u64 *acc, u64 a, u64 b)
{
int c1, c2;
u128 res = (u128)a * b;
u64 lo = res, hi = res >> 64;
c1 = __builtin_add_overflow(lo, acc[0], [0]);
c2 = __builtin_add_overflow(hi, acc[1], [1])
| __builtin_add_overflow(c1, acc[1], [1]);
__builtin_add_overflow(c2, acc[2], [2]);
}
testcase3:
movq%rsi, %rax
mulq%rdx
addq%rax, (%rdi)
adcq%rdx, 8(%rdi)
adcq$0, 16(%rdi)
ret
Thanks again, Jakub.
[Bug target/110104] gcc produces sub-optimal code for _addcarry_u64 chain
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=110104 --- Comment #4 from Mason --- I confirm that trunk now emits the same code for testcase1 and testcase2. Thanks Jakub and Roger, great work!
[Bug target/110104] gcc produces sub-optimal code for _addcarry_u64 chain
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=110104 Jakub Jelinek changed: What|Removed |Added Resolution|--- |FIXED Status|NEW |RESOLVED --- Comment #3 from Jakub Jelinek --- GCC trunk now emits movq%rsi, %rax mulq%rdx addq%rax, (%rdi) adcq%rdx, 8(%rdi) adcq$0, 16(%rdi) ret
[Bug target/110104] gcc produces sub-optimal code for _addcarry_u64 chain
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=110104 --- Comment #2 from Mason --- You meant PR79173 ;) Latest update: https://gcc.gnu.org/pipermail/gcc-patches/2023-June/621554.html I didn't see my testcase specifically in Jakub's patch, but I'll test trunk on godbolt when/if the patch lands.
[Bug target/110104] gcc produces sub-optimal code for _addcarry_u64 chain
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=110104 Roger Sayle changed: What|Removed |Added Status|ASSIGNED|NEW Assignee|roger at nextmovesoftware dot com |unassigned at gcc dot gnu.org --- Comment #1 from Roger Sayle --- I proposed a fix at https://gcc.gnu.org/pipermail/gcc-patches/2023-June/620823.html but this was obsoleted by a much more comprehensive patch (for PR79193) proposed by Jakub just an hour earlier: https://gcc.gnu.org/pipermail/gcc-patches/2023-June/620821.html
[Bug target/110104] gcc produces sub-optimal code for _addcarry_u64 chain
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=110104 Roger Sayle changed: What|Removed |Added CC||roger at nextmovesoftware dot com Status|UNCONFIRMED |ASSIGNED Ever confirmed|0 |1 Assignee|unassigned at gcc dot gnu.org |roger at nextmovesoftware dot com Last reconfirmed||2023-06-04
