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* [Bug tree-optimization/95423] New: Failure to optimize separated multiplications by x and square of x
@ 2020-05-29 19:53 gabravier at gmail dot com
2020-05-29 20:01 ` [Bug tree-optimization/95423] " gabravier at gmail dot com
` (5 more replies)
0 siblings, 6 replies; 7+ messages in thread
From: gabravier at gmail dot com @ 2020-05-29 19:53 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=95423
Bug ID: 95423
Summary: Failure to optimize separated multiplications by x and
square of x
Product: gcc
Version: 11.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: tree-optimization
Assignee: unassigned at gcc dot gnu.org
Reporter: gabravier at gmail dot com
Target Milestone: ---
int f(int a, int b, int x)
{
return a * (x * x) + (b * x);
}
This can be optimized to `return (((a * x) + b) * x);`. LLVM does this
transformation, but GCC does not.
^ permalink raw reply [flat|nested] 7+ messages in thread* [Bug tree-optimization/95423] Failure to optimize separated multiplications by x and square of x
2020-05-29 19:53 [Bug tree-optimization/95423] New: Failure to optimize separated multiplications by x and square of x gabravier at gmail dot com
@ 2020-05-29 20:01 ` gabravier at gmail dot com
2020-05-29 21:06 ` pinskia at gcc dot gnu.org
` (4 subsequent siblings)
5 siblings, 0 replies; 7+ messages in thread
From: gabravier at gmail dot com @ 2020-05-29 20:01 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=95423
--- Comment #1 from Gabriel Ravier <gabravier at gmail dot com> ---
I've hit a similar thing with this function :
int f(int x)
{
return (x * x * x) - (3 * x) - 1;
}
Which can be optimized to `return (((x * x) - 3) * x) - 1;`, but isn't
^ permalink raw reply [flat|nested] 7+ messages in thread* [Bug tree-optimization/95423] Failure to optimize separated multiplications by x and square of x
2020-05-29 19:53 [Bug tree-optimization/95423] New: Failure to optimize separated multiplications by x and square of x gabravier at gmail dot com
2020-05-29 20:01 ` [Bug tree-optimization/95423] " gabravier at gmail dot com
@ 2020-05-29 21:06 ` pinskia at gcc dot gnu.org
2020-05-29 21:31 ` glisse at gcc dot gnu.org
` (3 subsequent siblings)
5 siblings, 0 replies; 7+ messages in thread
From: pinskia at gcc dot gnu.org @ 2020-05-29 21:06 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=95423
--- Comment #2 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
Could there be overflows which don't happen originally?
^ permalink raw reply [flat|nested] 7+ messages in thread* [Bug tree-optimization/95423] Failure to optimize separated multiplications by x and square of x
2020-05-29 19:53 [Bug tree-optimization/95423] New: Failure to optimize separated multiplications by x and square of x gabravier at gmail dot com
2020-05-29 20:01 ` [Bug tree-optimization/95423] " gabravier at gmail dot com
2020-05-29 21:06 ` pinskia at gcc dot gnu.org
@ 2020-05-29 21:31 ` glisse at gcc dot gnu.org
2020-06-02 6:46 ` rguenth at gcc dot gnu.org
` (2 subsequent siblings)
5 siblings, 0 replies; 7+ messages in thread
From: glisse at gcc dot gnu.org @ 2020-05-29 21:31 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=95423
--- Comment #3 from Marc Glisse <glisse at gcc dot gnu.org> ---
We manage it with -fwrapv. This should happen late when we don't care about
overflow anymore, or it needs to introduce casts to an unsigned type.
^ permalink raw reply [flat|nested] 7+ messages in thread* [Bug tree-optimization/95423] Failure to optimize separated multiplications by x and square of x
2020-05-29 19:53 [Bug tree-optimization/95423] New: Failure to optimize separated multiplications by x and square of x gabravier at gmail dot com
` (2 preceding siblings ...)
2020-05-29 21:31 ` glisse at gcc dot gnu.org
@ 2020-06-02 6:46 ` rguenth at gcc dot gnu.org
2020-06-03 20:32 ` joseph at codesourcery dot com
2021-12-16 0:01 ` pinskia at gcc dot gnu.org
5 siblings, 0 replies; 7+ messages in thread
From: rguenth at gcc dot gnu.org @ 2020-06-02 6:46 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=95423
Richard Biener <rguenth at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Last reconfirmed| |2020-06-02
Status|UNCONFIRMED |NEW
Ever confirmed|0 |1
CC| |rguenth at gcc dot gnu.org
--- Comment #4 from Richard Biener <rguenth at gcc dot gnu.org> ---
We probably have duplicates - the main issue is the reassoc pass does not
run for signed integer arithmetic chains.
^ permalink raw reply [flat|nested] 7+ messages in thread* [Bug tree-optimization/95423] Failure to optimize separated multiplications by x and square of x
2020-05-29 19:53 [Bug tree-optimization/95423] New: Failure to optimize separated multiplications by x and square of x gabravier at gmail dot com
` (3 preceding siblings ...)
2020-06-02 6:46 ` rguenth at gcc dot gnu.org
@ 2020-06-03 20:32 ` joseph at codesourcery dot com
2021-12-16 0:01 ` pinskia at gcc dot gnu.org
5 siblings, 0 replies; 7+ messages in thread
From: joseph at codesourcery dot com @ 2020-06-03 20:32 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=95423
--- Comment #5 from joseph at codesourcery dot com <joseph at codesourcery dot com> ---
On Fri, 29 May 2020, pinskia at gcc dot gnu.org wrote:
> Could there be overflows which don't happen originally?
Yes. Say a == INT_MIN, x == -1, b == 0, for example. (This
transformation can also remove overflows.)
^ permalink raw reply [flat|nested] 7+ messages in thread* [Bug tree-optimization/95423] Failure to optimize separated multiplications by x and square of x
2020-05-29 19:53 [Bug tree-optimization/95423] New: Failure to optimize separated multiplications by x and square of x gabravier at gmail dot com
` (4 preceding siblings ...)
2020-06-03 20:32 ` joseph at codesourcery dot com
@ 2021-12-16 0:01 ` pinskia at gcc dot gnu.org
5 siblings, 0 replies; 7+ messages in thread
From: pinskia at gcc dot gnu.org @ 2021-12-16 0:01 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=95423
Andrew Pinski <pinskia at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Severity|normal |enhancement
^ permalink raw reply [flat|nested] 7+ messages in thread
end of thread, other threads:[~2021-12-16 0:01 UTC | newest]
Thread overview: 7+ messages (download: mbox.gz / follow: Atom feed)
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2020-05-29 19:53 [Bug tree-optimization/95423] New: Failure to optimize separated multiplications by x and square of x gabravier at gmail dot com
2020-05-29 20:01 ` [Bug tree-optimization/95423] " gabravier at gmail dot com
2020-05-29 21:06 ` pinskia at gcc dot gnu.org
2020-05-29 21:31 ` glisse at gcc dot gnu.org
2020-06-02 6:46 ` rguenth at gcc dot gnu.org
2020-06-03 20:32 ` joseph at codesourcery dot com
2021-12-16 0:01 ` pinskia at gcc dot gnu.org
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