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* [Bug tree-optimization/25620] New: Missed optimisation with power
@ 2006-01-01 12:29 jv244 at cam dot ac dot uk
2006-01-06 14:07 ` [Bug tree-optimization/25620] Missed optimization with power (only with -ffast-math) pinskia at gcc dot gnu dot org
` (17 more replies)
0 siblings, 18 replies; 19+ messages in thread
From: jv244 at cam dot ac dot uk @ 2006-01-01 12:29 UTC (permalink / raw)
To: gcc-bugs
The following is not optimised (I tested current 4.2) with -ffast-math -O2 (or
any of the other options I tried):
SUBROUTINE S41(a,b,c,N)
IMPLICIT NONE
integer :: N
real*8 :: a(N),b(N),c(N)
integer :: i
c=0.0D0
DO i=1,N
b(i)=b(i)+a(i)**(4.0D0/3.0D0)
c(i)=c(i)+a(i)**(2.0D0/3.0D0)
ENDDO
END SUBROUTINE
This could be written as
SUBROUTINE S42(a,b,c,N)
IMPLICIT NONE
integer :: N
real*8 :: a(N),b(N),c(N),tmp,tmp2,tmp4
real*8, parameter :: p=1.0D0/3.0D0
integer :: i
c=0.0D0
DO i=1,N
tmp=a(i)**p ! could even be done with a cube root
tmp2=tmp*tmp
tmp4=tmp2*tmp2
b(i)=b(i)+tmp4
c(i)=c(i)+tmp2
ENDDO
END SUBROUTINE
saving at least one expensive power computation. Also replacing the cube root
with specific code would be nice.
--
Summary: Missed optimisation with power
Product: gcc
Version: 4.2.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: tree-optimization
AssignedTo: unassigned at gcc dot gnu dot org
ReportedBy: jv244 at cam dot ac dot uk
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=25620
^ permalink raw reply [flat|nested] 19+ messages in thread
* [Bug tree-optimization/25620] Missed optimization with power (only with -ffast-math)
2006-01-01 12:29 [Bug tree-optimization/25620] New: Missed optimisation with power jv244 at cam dot ac dot uk
@ 2006-01-06 14:07 ` pinskia at gcc dot gnu dot org
2006-01-13 16:37 ` [Bug tree-optimization/25620] Missed optimization with power pinskia at gcc dot gnu dot org
` (16 subsequent siblings)
17 siblings, 0 replies; 19+ messages in thread
From: pinskia at gcc dot gnu dot org @ 2006-01-06 14:07 UTC (permalink / raw)
To: gcc-bugs
------- Comment #1 from pinskia at gcc dot gnu dot org 2006-01-06 14:07 -------
Confirmed.
--
pinskia at gcc dot gnu dot org changed:
What |Removed |Added
----------------------------------------------------------------------------
Severity|normal |enhancement
Status|UNCONFIRMED |NEW
Ever Confirmed|0 |1
Last reconfirmed|0000-00-00 00:00:00 |2006-01-06 14:07:43
date| |
Summary|Missed optimisation with |Missed optimization with
|power |power (only with -ffast-
| |math)
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=25620
^ permalink raw reply [flat|nested] 19+ messages in thread
* [Bug tree-optimization/25620] Missed optimization with power
2006-01-01 12:29 [Bug tree-optimization/25620] New: Missed optimisation with power jv244 at cam dot ac dot uk
2006-01-06 14:07 ` [Bug tree-optimization/25620] Missed optimization with power (only with -ffast-math) pinskia at gcc dot gnu dot org
@ 2006-01-13 16:37 ` pinskia at gcc dot gnu dot org
2006-01-13 16:44 ` [Bug fortran/25620] " rguenth at gcc dot gnu dot org
` (15 subsequent siblings)
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From: pinskia at gcc dot gnu dot org @ 2006-01-13 16:37 UTC (permalink / raw)
To: gcc-bugs
------- Comment #2 from pinskia at gcc dot gnu dot org 2006-01-13 16:37 -------
Actually I take back my comment about with -ffast-math only as Fortran rules
are way different from C and C++.
--
pinskia at gcc dot gnu dot org changed:
What |Removed |Added
----------------------------------------------------------------------------
Summary|Missed optimization with |Missed optimization with
|power (only with -ffast- |power
|math) |
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=25620
^ permalink raw reply [flat|nested] 19+ messages in thread
* [Bug fortran/25620] Missed optimization with power
2006-01-01 12:29 [Bug tree-optimization/25620] New: Missed optimisation with power jv244 at cam dot ac dot uk
2006-01-06 14:07 ` [Bug tree-optimization/25620] Missed optimization with power (only with -ffast-math) pinskia at gcc dot gnu dot org
2006-01-13 16:37 ` [Bug tree-optimization/25620] Missed optimization with power pinskia at gcc dot gnu dot org
@ 2006-01-13 16:44 ` rguenth at gcc dot gnu dot org
2006-01-13 17:33 ` jv244 at cam dot ac dot uk
` (14 subsequent siblings)
17 siblings, 0 replies; 19+ messages in thread
From: rguenth at gcc dot gnu dot org @ 2006-01-13 16:44 UTC (permalink / raw)
To: gcc-bugs
------- Comment #3 from rguenth at gcc dot gnu dot org 2006-01-13 16:44 -------
This needs to be done by the frontend, as the folded 2/3 or 4/3 is not exactly
representable in the target FP format (and such cannot be checked for). Making
this a frontend bug, rather than just closing as WONTFIX ;)
--
rguenth at gcc dot gnu dot org changed:
What |Removed |Added
----------------------------------------------------------------------------
Component|tree-optimization |fortran
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=25620
^ permalink raw reply [flat|nested] 19+ messages in thread
* [Bug fortran/25620] Missed optimization with power
2006-01-01 12:29 [Bug tree-optimization/25620] New: Missed optimisation with power jv244 at cam dot ac dot uk
` (2 preceding siblings ...)
2006-01-13 16:44 ` [Bug fortran/25620] " rguenth at gcc dot gnu dot org
@ 2006-01-13 17:33 ` jv244 at cam dot ac dot uk
2006-01-13 17:38 ` jv244 at cam dot ac dot uk
` (13 subsequent siblings)
17 siblings, 0 replies; 19+ messages in thread
From: jv244 at cam dot ac dot uk @ 2006-01-13 17:33 UTC (permalink / raw)
To: gcc-bugs
------- Comment #4 from jv244 at cam dot ac dot uk 2006-01-13 17:33 -------
(In reply to comment #3)
> This needs to be done by the frontend, as the folded 2/3 or 4/3 is not exactly
> representable in the target FP format (and such cannot be checked for). Making
> this a frontend bug, rather than just closing as WONTFIX ;)
Without fully understanding the above in all details.
some target FP format might still have that 2./3. == 2 * 1./3. ?
Furthermore, I would think that under -ffast-math these kind of transformations
should be allowed if these equalities hold 'at machine precision'. E.g.
x**p is replaced by cuberoot(p) if p is the FP number that is closest to 1./3.
--
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=25620
^ permalink raw reply [flat|nested] 19+ messages in thread
* [Bug fortran/25620] Missed optimization with power
2006-01-01 12:29 [Bug tree-optimization/25620] New: Missed optimisation with power jv244 at cam dot ac dot uk
` (3 preceding siblings ...)
2006-01-13 17:33 ` jv244 at cam dot ac dot uk
@ 2006-01-13 17:38 ` jv244 at cam dot ac dot uk
2006-01-13 18:15 ` jv244 at cam dot ac dot uk
` (12 subsequent siblings)
17 siblings, 0 replies; 19+ messages in thread
From: jv244 at cam dot ac dot uk @ 2006-01-13 17:38 UTC (permalink / raw)
To: gcc-bugs
------- Comment #5 from jv244 at cam dot ac dot uk 2006-01-13 17:38 -------
I just note that ifort generates this in the asm
for a**(1./3.):
call cbrtf
and for a**(1.D0/3.D0)
call cbrt
--
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=25620
^ permalink raw reply [flat|nested] 19+ messages in thread
* [Bug fortran/25620] Missed optimization with power
2006-01-01 12:29 [Bug tree-optimization/25620] New: Missed optimisation with power jv244 at cam dot ac dot uk
` (4 preceding siblings ...)
2006-01-13 17:38 ` jv244 at cam dot ac dot uk
@ 2006-01-13 18:15 ` jv244 at cam dot ac dot uk
2006-01-13 18:42 ` rguenth at gcc dot gnu dot org
` (11 subsequent siblings)
17 siblings, 0 replies; 19+ messages in thread
From: jv244 at cam dot ac dot uk @ 2006-01-13 18:15 UTC (permalink / raw)
To: gcc-bugs
------- Comment #6 from jv244 at cam dot ac dot uk 2006-01-13 18:15 -------
another example:
REAL*8 :: a,b
read(6,*) a
b=a**(3.D0/2.D0)
write(6,*) b
END
gets computed by ifort as
b=a*sqrt(a)
but this is also turned into pow by gfortran at -O3 -ffast-math
--
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=25620
^ permalink raw reply [flat|nested] 19+ messages in thread
* [Bug fortran/25620] Missed optimization with power
2006-01-01 12:29 [Bug tree-optimization/25620] New: Missed optimisation with power jv244 at cam dot ac dot uk
` (5 preceding siblings ...)
2006-01-13 18:15 ` jv244 at cam dot ac dot uk
@ 2006-01-13 18:42 ` rguenth at gcc dot gnu dot org
2006-01-13 19:58 ` kargl at gcc dot gnu dot org
` (10 subsequent siblings)
17 siblings, 0 replies; 19+ messages in thread
From: rguenth at gcc dot gnu dot org @ 2006-01-13 18:42 UTC (permalink / raw)
To: gcc-bugs
------- Comment #7 from rguenth at gcc dot gnu dot org 2006-01-13 18:42 -------
Looking at how we deal with all this, we seem to like pow() very much during
folding, even doing the reverse transformations you suggest. The
transformation
back to sqrt ( x**N ) with N being an integer could be done by
expand_builtin_pow
in case that computation of sqrt is cheap. Other than that, exposing integer
powers is only a win if theres some CSE possibility.
--
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=25620
^ permalink raw reply [flat|nested] 19+ messages in thread
* [Bug fortran/25620] Missed optimization with power
2006-01-01 12:29 [Bug tree-optimization/25620] New: Missed optimisation with power jv244 at cam dot ac dot uk
` (6 preceding siblings ...)
2006-01-13 18:42 ` rguenth at gcc dot gnu dot org
@ 2006-01-13 19:58 ` kargl at gcc dot gnu dot org
2006-09-04 14:10 ` jv244 at cam dot ac dot uk
` (9 subsequent siblings)
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From: kargl at gcc dot gnu dot org @ 2006-01-13 19:58 UTC (permalink / raw)
To: gcc-bugs
------- Comment #8 from kargl at gcc dot gnu dot org 2006-01-13 19:58 -------
Technically, all of the transformations noted by Joost are
a violation of the Fortran standard with the possible
exception of the transformation of x**(1./3.) to cbrt(x).
See 7.1.7.2.
--
kargl at gcc dot gnu dot org changed:
What |Removed |Added
----------------------------------------------------------------------------
CC| |kargl at gcc dot gnu dot org
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=25620
^ permalink raw reply [flat|nested] 19+ messages in thread
* [Bug fortran/25620] Missed optimization with power
2006-01-01 12:29 [Bug tree-optimization/25620] New: Missed optimisation with power jv244 at cam dot ac dot uk
` (7 preceding siblings ...)
2006-01-13 19:58 ` kargl at gcc dot gnu dot org
@ 2006-09-04 14:10 ` jv244 at cam dot ac dot uk
2006-09-04 14:17 ` rguenther at suse dot de
` (8 subsequent siblings)
17 siblings, 0 replies; 19+ messages in thread
From: jv244 at cam dot ac dot uk @ 2006-09-04 14:10 UTC (permalink / raw)
To: gcc-bugs
------- Comment #9 from jv244 at cam dot ac dot uk 2006-09-04 14:10 -------
(In reply to comment #7)
> Looking at how we deal with all this, we seem to like pow() very much during
> folding, even doing the reverse transformations you suggest. The
> transformation
> back to sqrt ( x**N ) with N being an integer could be done by
> expand_builtin_pow
> in case that computation of sqrt is cheap. Other than that, exposing integer
> powers is only a win if theres some CSE possibility.
Despite this PR being a bit old, I'd like to add another (similar example, also
from real code) where other compilers generate much better code:
subroutine t(x)
x=x**1.5
end subroutine t
pgf90:
# lineno: 0
sqrtss (%rdi), %xmm0
mulss (%rdi), %xmm0
movss %xmm0, (%rdi)
gfortran -S -O3 -ffast-math:
movss (%rdi), %xmm0
movq %rdi, %rbx
movss .LC0(%rip), %xmm1
call powf
movss %xmm0, (%rbx)
popq %rbx
ret
trying to time this with the following fragment:
y=0.
DO i=1,10000000
x=i
y=y+x**1.5
ENDDO
write(6,*) y
END
pgf90 is about 10 times faster than gfortran
--
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=25620
^ permalink raw reply [flat|nested] 19+ messages in thread
* [Bug fortran/25620] Missed optimization with power
2006-01-01 12:29 [Bug tree-optimization/25620] New: Missed optimisation with power jv244 at cam dot ac dot uk
` (8 preceding siblings ...)
2006-09-04 14:10 ` jv244 at cam dot ac dot uk
@ 2006-09-04 14:17 ` rguenther at suse dot de
2006-11-04 15:01 ` rguenth at gcc dot gnu dot org
` (7 subsequent siblings)
17 siblings, 0 replies; 19+ messages in thread
From: rguenther at suse dot de @ 2006-09-04 14:17 UTC (permalink / raw)
To: gcc-bugs
------- Comment #10 from rguenther at suse dot de 2006-09-04 14:17 -------
Subject: Re: Missed optimization with power
On Mon, 4 Sep 2006, jv244 at cam dot ac dot uk wrote:
>
>
> ------- Comment #9 from jv244 at cam dot ac dot uk 2006-09-04 14:10 -------
> (In reply to comment #7)
> > Looking at how we deal with all this, we seem to like pow() very much during
> > folding, even doing the reverse transformations you suggest. The
> > transformation
> > back to sqrt ( x**N ) with N being an integer could be done by
> > expand_builtin_pow
> > in case that computation of sqrt is cheap. Other than that, exposing integer
> > powers is only a win if theres some CSE possibility.
>
> Despite this PR being a bit old, I'd like to add another (similar example, also
> from real code) where other compilers generate much better code:
>
> subroutine t(x)
> x=x**1.5
> end subroutine t
>
> pgf90:
> # lineno: 0
> sqrtss (%rdi), %xmm0
> mulss (%rdi), %xmm0
> movss %xmm0, (%rdi)
>
> gfortran -S -O3 -ffast-math:
> movss (%rdi), %xmm0
> movq %rdi, %rbx
> movss .LC0(%rip), %xmm1
> call powf
> movss %xmm0, (%rbx)
> popq %rbx
> ret
This should be doable from expand_builtin_pow if we have an optab
for the sqrt computation.
Richard.
--
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=25620
^ permalink raw reply [flat|nested] 19+ messages in thread
* [Bug fortran/25620] Missed optimization with power
2006-01-01 12:29 [Bug tree-optimization/25620] New: Missed optimisation with power jv244 at cam dot ac dot uk
` (9 preceding siblings ...)
2006-09-04 14:17 ` rguenther at suse dot de
@ 2006-11-04 15:01 ` rguenth at gcc dot gnu dot org
2006-11-05 20:39 ` [Bug middle-end/25620] " patchapp at dberlin dot org
` (6 subsequent siblings)
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From: rguenth at gcc dot gnu dot org @ 2006-11-04 15:01 UTC (permalink / raw)
To: gcc-bugs
------- Comment #11 from rguenth at gcc dot gnu dot org 2006-11-04 15:01 -------
Mine.
--
rguenth at gcc dot gnu dot org changed:
What |Removed |Added
----------------------------------------------------------------------------
AssignedTo|unassigned at gcc dot gnu |rguenth at gcc dot gnu dot
|dot org |org
Status|NEW |ASSIGNED
Last reconfirmed|2006-04-23 18:02:00 |2006-11-04 15:01:43
date| |
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=25620
^ permalink raw reply [flat|nested] 19+ messages in thread
* [Bug middle-end/25620] Missed optimization with power
2006-01-01 12:29 [Bug tree-optimization/25620] New: Missed optimisation with power jv244 at cam dot ac dot uk
` (10 preceding siblings ...)
2006-11-04 15:01 ` rguenth at gcc dot gnu dot org
@ 2006-11-05 20:39 ` patchapp at dberlin dot org
2006-11-26 14:30 ` patchapp at dberlin dot org
` (5 subsequent siblings)
17 siblings, 0 replies; 19+ messages in thread
From: patchapp at dberlin dot org @ 2006-11-05 20:39 UTC (permalink / raw)
To: gcc-bugs
------- Comment #12 from patchapp at dberlin dot org 2006-11-05 20:39 -------
Subject: Bug number PR25620
A patch for this bug has been added to the patch tracker.
The mailing list url for the patch is
http://gcc.gnu.org/ml/gcc-patches/2006-11/msg00216.html
--
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=25620
^ permalink raw reply [flat|nested] 19+ messages in thread
* [Bug middle-end/25620] Missed optimization with power
2006-01-01 12:29 [Bug tree-optimization/25620] New: Missed optimisation with power jv244 at cam dot ac dot uk
` (11 preceding siblings ...)
2006-11-05 20:39 ` [Bug middle-end/25620] " patchapp at dberlin dot org
@ 2006-11-26 14:30 ` patchapp at dberlin dot org
2006-11-27 11:39 ` rguenth at gcc dot gnu dot org
` (4 subsequent siblings)
17 siblings, 0 replies; 19+ messages in thread
From: patchapp at dberlin dot org @ 2006-11-26 14:30 UTC (permalink / raw)
To: gcc-bugs
------- Comment #13 from patchapp at dberlin dot org 2006-11-26 14:30 -------
Subject: Bug number PR25620
A patch for this bug has been added to the patch tracker.
The mailing list url for the patch is
http://gcc.gnu.org/ml/gcc-patches/2006-11/msg01758.html
--
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=25620
^ permalink raw reply [flat|nested] 19+ messages in thread
* [Bug middle-end/25620] Missed optimization with power
2006-01-01 12:29 [Bug tree-optimization/25620] New: Missed optimisation with power jv244 at cam dot ac dot uk
` (12 preceding siblings ...)
2006-11-26 14:30 ` patchapp at dberlin dot org
@ 2006-11-27 11:39 ` rguenth at gcc dot gnu dot org
2006-11-27 11:52 ` [Bug fortran/25620] " rguenth at gcc dot gnu dot org
` (3 subsequent siblings)
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From: rguenth at gcc dot gnu dot org @ 2006-11-27 11:39 UTC (permalink / raw)
To: gcc-bugs
------- Comment #14 from rguenth at gcc dot gnu dot org 2006-11-27 11:38 -------
Subject: Bug 25620
Author: rguenth
Date: Mon Nov 27 11:38:42 2006
New Revision: 119248
URL: http://gcc.gnu.org/viewcvs?root=gcc&view=rev&rev=119248
Log:
2006-11-27 Richard Guenther <rguenther@suse.de>
PR middle-end/25620
* builtins.c (expand_builtin_pow): Optimize non integer valued
constant exponents using sqrt or cbrt if possible. Always fall back
to expanding via optabs.
* gcc.target/i386/pow-1.c: New testcase.
* gcc.dg/builtins-58.c: Likewise.
Added:
trunk/gcc/testsuite/gcc.dg/builtins-58.c
trunk/gcc/testsuite/gcc.target/i386/pow-1.c
Modified:
trunk/gcc/ChangeLog
trunk/gcc/builtins.c
trunk/gcc/testsuite/ChangeLog
--
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=25620
^ permalink raw reply [flat|nested] 19+ messages in thread
* [Bug fortran/25620] Missed optimization with power
2006-01-01 12:29 [Bug tree-optimization/25620] New: Missed optimisation with power jv244 at cam dot ac dot uk
` (13 preceding siblings ...)
2006-11-27 11:39 ` rguenth at gcc dot gnu dot org
@ 2006-11-27 11:52 ` rguenth at gcc dot gnu dot org
2006-11-27 16:49 ` jv244 at cam dot ac dot uk
` (2 subsequent siblings)
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From: rguenth at gcc dot gnu dot org @ 2006-11-27 11:52 UTC (permalink / raw)
To: gcc-bugs
------- Comment #15 from rguenth at gcc dot gnu dot org 2006-11-27 11:52 -------
Fixed (partly) on the mainline. We can now expand pow (x, n/2) and pow (x,
n/3)
properly using sqrt and/or cbrt, but cbrt is not available from the fortran
frontend (it misses to define __builtin_cbrt).
--
rguenth at gcc dot gnu dot org changed:
What |Removed |Added
----------------------------------------------------------------------------
AssignedTo|rguenth at gcc dot gnu dot |unassigned at gcc dot gnu
|org |dot org
Status|ASSIGNED |NEW
Component|middle-end |fortran
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=25620
^ permalink raw reply [flat|nested] 19+ messages in thread
* [Bug fortran/25620] Missed optimization with power
2006-01-01 12:29 [Bug tree-optimization/25620] New: Missed optimisation with power jv244 at cam dot ac dot uk
` (14 preceding siblings ...)
2006-11-27 11:52 ` [Bug fortran/25620] " rguenth at gcc dot gnu dot org
@ 2006-11-27 16:49 ` jv244 at cam dot ac dot uk
2007-01-22 22:02 ` fxcoudert at gcc dot gnu dot org
2010-03-18 14:37 ` vincent at vinc17 dot org
17 siblings, 0 replies; 19+ messages in thread
From: jv244 at cam dot ac dot uk @ 2006-11-27 16:49 UTC (permalink / raw)
To: gcc-bugs
------- Comment #16 from jv244 at cam dot ac dot uk 2006-11-27 16:49 -------
(In reply to comment #15)
> Fixed (partly) on the mainline. We can now expand pow (x, n/2) and pow (x,
> n/3)
> properly using sqrt and/or cbrt, but cbrt is not available from the fortran
> frontend (it misses to define __builtin_cbrt).
>
Thanks Richard, for this patch, and your other efforts to improve performance
for number crunching applications...
hopefully the fortran frontend will be fixed as well.
--
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=25620
^ permalink raw reply [flat|nested] 19+ messages in thread
* [Bug fortran/25620] Missed optimization with power
2006-01-01 12:29 [Bug tree-optimization/25620] New: Missed optimisation with power jv244 at cam dot ac dot uk
` (15 preceding siblings ...)
2006-11-27 16:49 ` jv244 at cam dot ac dot uk
@ 2007-01-22 22:02 ` fxcoudert at gcc dot gnu dot org
2010-03-18 14:37 ` vincent at vinc17 dot org
17 siblings, 0 replies; 19+ messages in thread
From: fxcoudert at gcc dot gnu dot org @ 2007-01-22 22:02 UTC (permalink / raw)
To: gcc-bugs
------- Comment #17 from fxcoudert at gcc dot gnu dot org 2007-01-22 22:02 -------
cbrt is now available in the front-end (among others), thanks again to Richard!
Closing this PR, as the optimization appears to be working fully:
$ cat a.f90
REAL*8 :: a(6),b(6)
read(*,*) a(:)
b(1)=a(1)**(1.D0/3.D0)
b(2)=a(2)**(1/3.D0)
b(3)=a(3)**(2.D0/3.D0)
b(4)=a(4)**(1/2.D0)
b(5)=a(5)**(1.D0/2.D0)
b(6)=a(6)**(3.D0/2.D0)
write(*,*) b
END
$ gfortran -O2 -ffast-math a.f90 -S
$ grep -c pow a.s
0
$ grep -c cbrt a.s
3
$ grep -c sqrt a.s
3
--
fxcoudert at gcc dot gnu dot org changed:
What |Removed |Added
----------------------------------------------------------------------------
Status|NEW |RESOLVED
Resolution| |FIXED
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=25620
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* [Bug fortran/25620] Missed optimization with power
2006-01-01 12:29 [Bug tree-optimization/25620] New: Missed optimisation with power jv244 at cam dot ac dot uk
` (16 preceding siblings ...)
2007-01-22 22:02 ` fxcoudert at gcc dot gnu dot org
@ 2010-03-18 14:37 ` vincent at vinc17 dot org
17 siblings, 0 replies; 19+ messages in thread
From: vincent at vinc17 dot org @ 2010-03-18 14:37 UTC (permalink / raw)
To: gcc-bugs
------- Comment #18 from vincent at vinc17 dot org 2010-03-18 14:37 -------
The patch affected C, where the transformation of pow(x, 0.5) into sqrt(x) is
incorrect. See PR 43419.
--
vincent at vinc17 dot org changed:
What |Removed |Added
----------------------------------------------------------------------------
CC| |vincent at vinc17 dot org
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=25620
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2006-01-01 12:29 [Bug tree-optimization/25620] New: Missed optimisation with power jv244 at cam dot ac dot uk
2006-01-06 14:07 ` [Bug tree-optimization/25620] Missed optimization with power (only with -ffast-math) pinskia at gcc dot gnu dot org
2006-01-13 16:37 ` [Bug tree-optimization/25620] Missed optimization with power pinskia at gcc dot gnu dot org
2006-01-13 16:44 ` [Bug fortran/25620] " rguenth at gcc dot gnu dot org
2006-01-13 17:33 ` jv244 at cam dot ac dot uk
2006-01-13 17:38 ` jv244 at cam dot ac dot uk
2006-01-13 18:15 ` jv244 at cam dot ac dot uk
2006-01-13 18:42 ` rguenth at gcc dot gnu dot org
2006-01-13 19:58 ` kargl at gcc dot gnu dot org
2006-09-04 14:10 ` jv244 at cam dot ac dot uk
2006-09-04 14:17 ` rguenther at suse dot de
2006-11-04 15:01 ` rguenth at gcc dot gnu dot org
2006-11-05 20:39 ` [Bug middle-end/25620] " patchapp at dberlin dot org
2006-11-26 14:30 ` patchapp at dberlin dot org
2006-11-27 11:39 ` rguenth at gcc dot gnu dot org
2006-11-27 11:52 ` [Bug fortran/25620] " rguenth at gcc dot gnu dot org
2006-11-27 16:49 ` jv244 at cam dot ac dot uk
2007-01-22 22:02 ` fxcoudert at gcc dot gnu dot org
2010-03-18 14:37 ` vincent at vinc17 dot org
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