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* [Bug middle-end/114559] New: After function inlining some optimizations missing
@ 2024-04-02 9:19 antoshkka at gmail dot com
2024-04-03 0:21 ` [Bug middle-end/114559] " pinskia at gcc dot gnu.org
` (3 more replies)
0 siblings, 4 replies; 5+ messages in thread
From: antoshkka at gmail dot com @ 2024-04-02 9:19 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=114559
Bug ID: 114559
Summary: After function inlining some optimizations missing
Product: gcc
Version: 14.0
Status: UNCONFIRMED
Keywords: missed-optimization
Severity: normal
Priority: P3
Component: middle-end
Assignee: unassigned at gcc dot gnu.org
Reporter: antoshkka at gmail dot com
Target Milestone: ---
Consider the example:
template <class Func>
int AtomicUpdate(int& atomic, Func updater) {
int old_value = atomic;
while (true) {
const int new_value = updater(int{old_value});
if (old_value == new_value) return old_value;
if (__atomic_compare_exchange_n(&atomic, &old_value, new_value, 1, 5, 5))
return new_value;
}
}
int AtomicMin(int& atomic, int value) {
return AtomicUpdate(atomic, [value](int old_value) {
return value < old_value ? value : old_value;
});
}
With -O2 GCC produces the assembly:
AtomicMin(int&, int):
mov eax, DWORD PTR [rdi]
.L3:
cmp esi, eax
mov edx, eax
cmovle edx, esi
jge .L4
lock cmpxchg DWORD PTR [rdi], edx
jne .L3
.L1:
mov eax, edx
ret
.L4:
mov edx, eax
jmp .L1
However, a more optimal assembly is possible:
AtomicMin(int&, int): # @AtomicMin(int&, int)
mov eax, dword ptr [rdi]
.LBB0_1: # =>This Inner Loop Header: Depth=1
cmp eax, esi
jle .LBB0_4
lock cmpxchg dword ptr [rdi], esi
jne .LBB0_1
mov eax, esi
.LBB0_4:
ret
Note that manual inlining of the lambda improves the codegen:
int AtomicMin(int& atomic, int value) {
int old_value = atomic;
while (true) {
const int new_value = (value < old_value ? value : old_value);
if (old_value == new_value) return old_value;
if (__atomic_compare_exchange_n(&atomic, &old_value, new_value, 1, 5, 5))
return new_value;
}
}
Results in
AtomicMin(int&, int):
mov eax, DWORD PTR [rdi]
.L3:
cmp esi, eax
mov edx, eax
cmovle edx, esi
jge .L1
lock cmpxchg DWORD PTR [rdi], edx
jne .L3
.L1:
mov eax, edx
ret
Godbolt playground: https://godbolt.org/z/G6YEGb15q
^ permalink raw reply [flat|nested] 5+ messages in thread
* [Bug middle-end/114559] After function inlining some optimizations missing
2024-04-02 9:19 [Bug middle-end/114559] New: After function inlining some optimizations missing antoshkka at gmail dot com
@ 2024-04-03 0:21 ` pinskia at gcc dot gnu.org
2024-04-03 0:30 ` [Bug tree-optimization/114559] [11/12/13/14 Regression] " pinskia at gcc dot gnu.org
` (2 subsequent siblings)
3 siblings, 0 replies; 5+ messages in thread
From: pinskia at gcc dot gnu.org @ 2024-04-03 0:21 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=114559
Andrew Pinski <pinskia at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
See Also| |https://gcc.gnu.org/bugzill
| |a/show_bug.cgi?id=110199
Last reconfirmed| |2024-04-03
Status|UNCONFIRMED |NEW
Ever confirmed|0 |1
--- Comment #1 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
Confirmed. Reduced testcase without the need of inlining nor atomics:
```
int g(int);
int h(int);
int f(int a, int b)
{
while (true)
{
int t = a < b ? a : b; // MIN<a,b>
if (b <= a)
return a;
{ a = g(a); if (h(t)) return t; }
// t here should be old a before the assignment from `g(a);`
}
}
```
As far as I can tell this is basically slightly more complex version of PR
110199 really wehre the MIN (MAX) has 2 usages. Note if we the usage of t in
`h(t)` the trunk (due to PR 110199) is able to optimize it correctly to
`return a`.
^ permalink raw reply [flat|nested] 5+ messages in thread
* [Bug tree-optimization/114559] [11/12/13/14 Regression] After function inlining some optimizations missing
2024-04-02 9:19 [Bug middle-end/114559] New: After function inlining some optimizations missing antoshkka at gmail dot com
2024-04-03 0:21 ` [Bug middle-end/114559] " pinskia at gcc dot gnu.org
@ 2024-04-03 0:30 ` pinskia at gcc dot gnu.org
2024-04-05 2:33 ` law at gcc dot gnu.org
2024-07-19 13:24 ` [Bug tree-optimization/114559] [12/13/14/15 " rguenth at gcc dot gnu.org
3 siblings, 0 replies; 5+ messages in thread
From: pinskia at gcc dot gnu.org @ 2024-04-03 0:30 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=114559
Andrew Pinski <pinskia at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Known to work| |8.5.0
CC| |pinskia at gcc dot gnu.org
Known to fail| |9.1.0
Target Milestone|--- |11.5
Summary|After function inlining |[11/12/13/14 Regression]
|some optimizations missing |After function inlining
| |some optimizations missing
--- Comment #2 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
Note the original testcase worked in GCC 8.5.0 and before and the reduced
testcase with the C++ front-end too. Due to not creating MIN/MAX expression
early.
So I am going to make this as a regression because the user would not
understand the difference really.
^ permalink raw reply [flat|nested] 5+ messages in thread
* [Bug tree-optimization/114559] [11/12/13/14 Regression] After function inlining some optimizations missing
2024-04-02 9:19 [Bug middle-end/114559] New: After function inlining some optimizations missing antoshkka at gmail dot com
2024-04-03 0:21 ` [Bug middle-end/114559] " pinskia at gcc dot gnu.org
2024-04-03 0:30 ` [Bug tree-optimization/114559] [11/12/13/14 Regression] " pinskia at gcc dot gnu.org
@ 2024-04-05 2:33 ` law at gcc dot gnu.org
2024-07-19 13:24 ` [Bug tree-optimization/114559] [12/13/14/15 " rguenth at gcc dot gnu.org
3 siblings, 0 replies; 5+ messages in thread
From: law at gcc dot gnu.org @ 2024-04-05 2:33 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=114559
Jeffrey A. Law <law at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Priority|P3 |P2
CC| |law at gcc dot gnu.org
^ permalink raw reply [flat|nested] 5+ messages in thread
* [Bug tree-optimization/114559] [12/13/14/15 Regression] After function inlining some optimizations missing
2024-04-02 9:19 [Bug middle-end/114559] New: After function inlining some optimizations missing antoshkka at gmail dot com
` (2 preceding siblings ...)
2024-04-05 2:33 ` law at gcc dot gnu.org
@ 2024-07-19 13:24 ` rguenth at gcc dot gnu.org
3 siblings, 0 replies; 5+ messages in thread
From: rguenth at gcc dot gnu.org @ 2024-07-19 13:24 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=114559
Richard Biener <rguenth at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Target Milestone|11.5 |12.5
--- Comment #3 from Richard Biener <rguenth at gcc dot gnu.org> ---
GCC 11 branch is being closed.
^ permalink raw reply [flat|nested] 5+ messages in thread
end of thread, other threads:[~2024-07-19 13:24 UTC | newest]
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2024-04-02 9:19 [Bug middle-end/114559] New: After function inlining some optimizations missing antoshkka at gmail dot com
2024-04-03 0:21 ` [Bug middle-end/114559] " pinskia at gcc dot gnu.org
2024-04-03 0:30 ` [Bug tree-optimization/114559] [11/12/13/14 Regression] " pinskia at gcc dot gnu.org
2024-04-05 2:33 ` law at gcc dot gnu.org
2024-07-19 13:24 ` [Bug tree-optimization/114559] [12/13/14/15 " rguenth at gcc dot gnu.org
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