* [Bug tree-optimization/79201] missed optimization: sinking doesn't handle calls, swap PRE and sinking
[not found] <bug-79201-4@http.gcc.gnu.org/bugzilla/>
@ 2021-06-11 10:12 ` drraph at gmail dot com
2021-09-11 7:04 ` pinskia at gcc dot gnu.org
` (2 subsequent siblings)
3 siblings, 0 replies; 4+ messages in thread
From: drraph at gmail dot com @ 2021-06-11 10:12 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=79201
--- Comment #5 from Raphael C <drraph at gmail dot com> ---
I can confirm you now get
f:
mov eax, 1
ret
with gcc 8 onwards.
^ permalink raw reply [flat|nested] 4+ messages in thread* [Bug tree-optimization/79201] missed optimization: sinking doesn't handle calls, swap PRE and sinking
[not found] <bug-79201-4@http.gcc.gnu.org/bugzilla/>
2021-06-11 10:12 ` [Bug tree-optimization/79201] missed optimization: sinking doesn't handle calls, swap PRE and sinking drraph at gmail dot com
@ 2021-09-11 7:04 ` pinskia at gcc dot gnu.org
2024-06-06 10:59 ` drraph at gmail dot com
2024-06-06 11:08 ` pinskia at gcc dot gnu.org
3 siblings, 0 replies; 4+ messages in thread
From: pinskia at gcc dot gnu.org @ 2021-09-11 7:04 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=79201
Andrew Pinski <pinskia at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Status|RESOLVED |NEW
Severity|normal |enhancement
Resolution|FIXED |---
--- Comment #6 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
So this is actually still broken in the sense if we turn off dominator
optimizations (-fno-tree-dominator-opts), the problem with PRE and sink
interaction comes into play still.
The improvement came in via r8-2694 which in fact added
-fno-tree-dominator-opts to gcc.dg/tree-ssa/ssa-sink-16.c .
Note DOM actually does the sinking rather than the rotating of the loop.
here is a testcase where DOM does not mess with the loop but we should still be
able to sink the function out and do when adding -fno-tree-pre:
int f(int n, int t) {
int i,j=0;
if (t >=31 || t < 0) return 100;
for (i = 0; i < t; i++) {
j = __builtin_ffs(i);
}
return j;
}
^ permalink raw reply [flat|nested] 4+ messages in thread* [Bug tree-optimization/79201] missed optimization: sinking doesn't handle calls, swap PRE and sinking
[not found] <bug-79201-4@http.gcc.gnu.org/bugzilla/>
2021-06-11 10:12 ` [Bug tree-optimization/79201] missed optimization: sinking doesn't handle calls, swap PRE and sinking drraph at gmail dot com
2021-09-11 7:04 ` pinskia at gcc dot gnu.org
@ 2024-06-06 10:59 ` drraph at gmail dot com
2024-06-06 11:08 ` pinskia at gcc dot gnu.org
3 siblings, 0 replies; 4+ messages in thread
From: drraph at gmail dot com @ 2024-06-06 10:59 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=79201
--- Comment #7 from Raphael C <drraph at gmail dot com> ---
As of gcc 8 this returns:
f(int):
mov eax, 1
ret
I think this can be closed as resolved now.
^ permalink raw reply [flat|nested] 4+ messages in thread* [Bug tree-optimization/79201] missed optimization: sinking doesn't handle calls, swap PRE and sinking
[not found] <bug-79201-4@http.gcc.gnu.org/bugzilla/>
` (2 preceding siblings ...)
2024-06-06 10:59 ` drraph at gmail dot com
@ 2024-06-06 11:08 ` pinskia at gcc dot gnu.org
3 siblings, 0 replies; 4+ messages in thread
From: pinskia at gcc dot gnu.org @ 2024-06-06 11:08 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=79201
--- Comment #8 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
(In reply to Andrew Pinski from comment #6)
> here is a testcase where DOM does not mess with the loop but we should still
> be able to sink the function out and do when adding -fno-tree-pre:
>
> int f(int n, int t) {
> int i,j=0;
> if (t >=31 || t < 0) return 100;
>
> for (i = 0; i < t; i++) {
> j = __builtin_ffs(i);
> }
> return j;
> }
Note in GCC 12+, you need -fno-tree-vectorize to get the bad behavior back.
^ permalink raw reply [flat|nested] 4+ messages in thread