* [Bug tree-optimization/89360] GCC doesn't emit cmovcc instruction in some cases
[not found] <bug-89360-4@http.gcc.gnu.org/bugzilla/>
@ 2021-08-19 20:39 ` pinskia at gcc dot gnu.org
2021-08-19 20:42 ` [Bug target/89360] " pinskia at gcc dot gnu.org
2023-05-06 19:02 ` pinskia at gcc dot gnu.org
2 siblings, 0 replies; 3+ messages in thread
From: pinskia at gcc dot gnu.org @ 2021-08-19 20:39 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=89360
Andrew Pinski <pinskia at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Status|UNCONFIRMED |NEW
Ever confirmed|0 |1
Last reconfirmed| |2021-08-19
Component|rtl-optimization |tree-optimization
Severity|normal |enhancement
--- Comment #1 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
Confirmed, with GCC 11+ we get close for sort2_if:
cmpl %esi, %edi
jl .L4
movl %esi, %eax
movl %edi, %esi
movl %eax, %edi
.L4:
movl %edi, (%rdx)
movl %esi, (%rcx)
GCC 9+ produces the cmov for sort2_ternary due to r9-3606.
We don't recongize the MIN/MAX in sort2_if as phiopt only handles the case
where there is only phi node which differs.
^ permalink raw reply [flat|nested] 3+ messages in thread* [Bug target/89360] GCC doesn't emit cmovcc instruction in some cases
[not found] <bug-89360-4@http.gcc.gnu.org/bugzilla/>
2021-08-19 20:39 ` [Bug tree-optimization/89360] GCC doesn't emit cmovcc instruction in some cases pinskia at gcc dot gnu.org
@ 2021-08-19 20:42 ` pinskia at gcc dot gnu.org
2023-05-06 19:02 ` pinskia at gcc dot gnu.org
2 siblings, 0 replies; 3+ messages in thread
From: pinskia at gcc dot gnu.org @ 2021-08-19 20:42 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=89360
Andrew Pinski <pinskia at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Component|tree-optimization |target
--- Comment #2 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
Also the other issue is two cmov back-to-back might be bad on x86_64.
In fact on aarch64 we get for sort2_if:
sort2_if(int, int, int*, int*):
cmp w0, w1
csel w4, w0, w1, lt
str w4, [x2]
csel w1, w1, w0, lt
str w1, [x3]
ret
So the question is a cmov better than a branch here, I don't know.
^ permalink raw reply [flat|nested] 3+ messages in thread* [Bug target/89360] GCC doesn't emit cmovcc instruction in some cases
[not found] <bug-89360-4@http.gcc.gnu.org/bugzilla/>
2021-08-19 20:39 ` [Bug tree-optimization/89360] GCC doesn't emit cmovcc instruction in some cases pinskia at gcc dot gnu.org
2021-08-19 20:42 ` [Bug target/89360] " pinskia at gcc dot gnu.org
@ 2023-05-06 19:02 ` pinskia at gcc dot gnu.org
2 siblings, 0 replies; 3+ messages in thread
From: pinskia at gcc dot gnu.org @ 2023-05-06 19:02 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=89360
Andrew Pinski <pinskia at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
See Also| |https://gcc.gnu.org/bugzill
| |a/show_bug.cgi?id=79390
Resolution|--- |INVALID
Status|NEW |RESOLVED
--- Comment #3 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
x86_64 has a cost model by design to reject back to back cmov.
See PR 79390 on the reasons why.
^ permalink raw reply [flat|nested] 3+ messages in thread