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* [Bug target/114528] New: (0xFFFFFFFF0001FFFFULL - 0x00123000) constant forming could be done in 2 instructions
@ 2024-03-29 2:17 pinskia at gcc dot gnu.org
2024-05-10 4:47 ` [Bug target/114528] " pinskia at gcc dot gnu.org
` (2 more replies)
0 siblings, 3 replies; 4+ messages in thread
From: pinskia at gcc dot gnu.org @ 2024-03-29 2:17 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=114528
Bug ID: 114528
Summary: (0xFFFFFFFF0001FFFFULL - 0x00123000) constant forming
could be done in 2 instructions
Product: gcc
Version: 14.0
Status: UNCONFIRMED
Keywords: missed-optimization
Severity: normal
Priority: P3
Component: target
Assignee: unassigned at gcc dot gnu.org
Reporter: pinskia at gcc dot gnu.org
Target Milestone: ---
Target: aarch64
Take:
```
long long f()
{
return 0xFFFFFFFF0001FFFF;// - 0x00123000;
}
long long g(long long a)
{
return a - 0x00123000;
}
long long x()
{
return 0xFFFFFFFF0001FFFF - 0x00123000;
}
long long x1()
{
return g(f());
}
```
As you can see x and x1 produces 3 instructions forming the constant but GCC
should be able to do it in 2 as shown via `g` and `f` are one instruction each.
Noticed from reading the LLVM issue
https://github.com/llvm/llvm-project/issues/87028 .
^ permalink raw reply [flat|nested] 4+ messages in thread
* [Bug target/114528] (0xFFFFFFFF0001FFFFULL - 0x00123000) constant forming could be done in 2 instructions
2024-03-29 2:17 [Bug target/114528] New: (0xFFFFFFFF0001FFFFULL - 0x00123000) constant forming could be done in 2 instructions pinskia at gcc dot gnu.org
@ 2024-05-10 4:47 ` pinskia at gcc dot gnu.org
2024-06-16 1:14 ` pinskia at gcc dot gnu.org
2024-06-16 9:27 ` xry111 at gcc dot gnu.org
2 siblings, 0 replies; 4+ messages in thread
From: pinskia at gcc dot gnu.org @ 2024-05-10 4:47 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=114528
Andrew Pinski <pinskia at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Assignee|unassigned at gcc dot gnu.org |pinskia at gcc dot gnu.org
--- Comment #1 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
I am going to have someone work on this so self-assigning for now.
^ permalink raw reply [flat|nested] 4+ messages in thread
* [Bug target/114528] (0xFFFFFFFF0001FFFFULL - 0x00123000) constant forming could be done in 2 instructions
2024-03-29 2:17 [Bug target/114528] New: (0xFFFFFFFF0001FFFFULL - 0x00123000) constant forming could be done in 2 instructions pinskia at gcc dot gnu.org
2024-05-10 4:47 ` [Bug target/114528] " pinskia at gcc dot gnu.org
@ 2024-06-16 1:14 ` pinskia at gcc dot gnu.org
2024-06-16 9:27 ` xry111 at gcc dot gnu.org
2 siblings, 0 replies; 4+ messages in thread
From: pinskia at gcc dot gnu.org @ 2024-06-16 1:14 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=114528
Andrew Pinski <pinskia at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Ever confirmed|0 |1
Status|UNCONFIRMED |ASSIGNED
Last reconfirmed| |2024-06-16
--- Comment #2 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
.
^ permalink raw reply [flat|nested] 4+ messages in thread
* [Bug target/114528] (0xFFFFFFFF0001FFFFULL - 0x00123000) constant forming could be done in 2 instructions
2024-03-29 2:17 [Bug target/114528] New: (0xFFFFFFFF0001FFFFULL - 0x00123000) constant forming could be done in 2 instructions pinskia at gcc dot gnu.org
2024-05-10 4:47 ` [Bug target/114528] " pinskia at gcc dot gnu.org
2024-06-16 1:14 ` pinskia at gcc dot gnu.org
@ 2024-06-16 9:27 ` xry111 at gcc dot gnu.org
2 siblings, 0 replies; 4+ messages in thread
From: xry111 at gcc dot gnu.org @ 2024-06-16 9:27 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=114528
Xi Ruoyao <xry111 at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
CC| |xry111 at gcc dot gnu.org
--- Comment #3 from Xi Ruoyao <xry111 at gcc dot gnu.org> ---
Note that on some uarch the naive implementation may have 1 cycle latency while
the "clever" implementation has 2 due to fusion. Maybe we need a tune
parameter.
^ permalink raw reply [flat|nested] 4+ messages in thread
end of thread, other threads:[~2024-06-16 9:27 UTC | newest]
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2024-03-29 2:17 [Bug target/114528] New: (0xFFFFFFFF0001FFFFULL - 0x00123000) constant forming could be done in 2 instructions pinskia at gcc dot gnu.org
2024-05-10 4:47 ` [Bug target/114528] " pinskia at gcc dot gnu.org
2024-06-16 1:14 ` pinskia at gcc dot gnu.org
2024-06-16 9:27 ` xry111 at gcc dot gnu.org
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