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* [Bug target/50302] New: inefficient float->double conversion in AVX with -mtune=generic
@ 2011-09-05 23:08 andi-gcc at firstfloor dot org
  2011-09-06  7:53 ` [Bug target/50302] " rguenth at gcc dot gnu.org
                   ` (5 more replies)
  0 siblings, 6 replies; 7+ messages in thread
From: andi-gcc at firstfloor dot org @ 2011-09-05 23:08 UTC (permalink / raw)
  To: gcc-bugs

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=50302

             Bug #: 50302
           Summary: inefficient float->double conversion in AVX with
                    -mtune=generic
    Classification: Unclassified
           Product: gcc
           Version: unknown
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: target
        AssignedTo: unassigned@gcc.gnu.org
        ReportedBy: andi-gcc@firstfloor.org


I noticed that with AVX and -mtune=generic and converting a single float to a
double gcc still generates

vunpcklps reg,reg
vcvtps2pd reg,reg

instead of the more straight forward and likely more power efficient

vcvtss2sd reg,reg

AFAIK the first sequence was only needed on some older AMD CPUs with SSE
to avoid a conversion penalty, does it really still make sense for AVX?

Perhaps that should be fixed for tune=generic ?

Test case:

#include <stdio.h>
float a = 1, b = 2;
float c;

int main(void)
{
        c = a + b;
        printf("%f\n", c);
        return 0;
}


^ permalink raw reply	[flat|nested] 7+ messages in thread
* [Bug target/50302] inefficient float->double conversion in AVX with -mtune=generic
  2011-09-05 23:08 [Bug target/50302] New: inefficient float->double conversion in AVX with -mtune=generic andi-gcc at firstfloor dot org
@ 2011-09-06  7:53 ` rguenth at gcc dot gnu.org
  2011-10-07  5:52 ` andi-gcc at firstfloor dot org
                   ` (4 subsequent siblings)
  5 siblings, 0 replies; 7+ messages in thread
From: rguenth at gcc dot gnu.org @ 2011-09-06  7:53 UTC (permalink / raw)
  To: gcc-bugs

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=50302

Richard Guenther <rguenth at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |NEW
   Last reconfirmed|                            |2011-09-06
                 CC|                            |harsha.jagasia at amd dot
                   |                            |com, hubicka at gcc dot
                   |                            |gnu.org
     Ever Confirmed|0                           |1

--- Comment #1 from Richard Guenther <rguenth at gcc dot gnu.org> 2011-09-06 07:51:46 UTC ---
Good question.  Probably even with -msseN we could tweak some generic settings
when we know no "old" CPUs have those issues.  Of course the question is
whether
we still need to care for those today or whether we should simply change
generic.


^ permalink raw reply	[flat|nested] 7+ messages in thread
* [Bug target/50302] inefficient float->double conversion in AVX with -mtune=generic
  2011-09-05 23:08 [Bug target/50302] New: inefficient float->double conversion in AVX with -mtune=generic andi-gcc at firstfloor dot org
  2011-09-06  7:53 ` [Bug target/50302] " rguenth at gcc dot gnu.org
@ 2011-10-07  5:52 ` andi-gcc at firstfloor dot org
  2011-10-07  5:58 ` jakub at gcc dot gnu.org
                   ` (3 subsequent siblings)
  5 siblings, 0 replies; 7+ messages in thread
From: andi-gcc at firstfloor dot org @ 2011-10-07  5:52 UTC (permalink / raw)
  To: gcc-bugs

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=50302

Andi Kleen <andi-gcc at firstfloor dot org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |RESOLVED
         Resolution|                            |DUPLICATE

--- Comment #2 from Andi Kleen <andi-gcc at firstfloor dot org> 2011-10-07 05:47:54 UTC ---
Was actually a dup of the GC problem.

I tried fixing the one-off cache, but it didn't fix the fragmentation

*** This bug has been marked as a duplicate of bug 50636 ***


^ permalink raw reply	[flat|nested] 7+ messages in thread
* [Bug target/50302] inefficient float->double conversion in AVX with -mtune=generic
  2011-09-05 23:08 [Bug target/50302] New: inefficient float->double conversion in AVX with -mtune=generic andi-gcc at firstfloor dot org
  2011-09-06  7:53 ` [Bug target/50302] " rguenth at gcc dot gnu.org
  2011-10-07  5:52 ` andi-gcc at firstfloor dot org
@ 2011-10-07  5:58 ` jakub at gcc dot gnu.org
  2011-10-07 14:42 ` andi-gcc at firstfloor dot org
                   ` (2 subsequent siblings)
  5 siblings, 0 replies; 7+ messages in thread
From: jakub at gcc dot gnu.org @ 2011-10-07  5:58 UTC (permalink / raw)
  To: gcc-bugs

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=50302

Jakub Jelinek <jakub at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|RESOLVED                    |NEW
                 CC|                            |jakub at gcc dot gnu.org
         Resolution|DUPLICATE                   |

--- Comment #3 from Jakub Jelinek <jakub at gcc dot gnu.org> 2011-10-07 05:57:40 UTC ---
(In reply to comment #2)
> Was actually a dup of the GC problem.
> 
> I tried fixing the one-off cache, but it didn't fix the fragmentation
> 
> *** This bug has been marked as a duplicate of bug 50636 ***

This is hardly a dup of PR50636.


^ permalink raw reply	[flat|nested] 7+ messages in thread
* [Bug target/50302] inefficient float->double conversion in AVX with -mtune=generic
  2011-09-05 23:08 [Bug target/50302] New: inefficient float->double conversion in AVX with -mtune=generic andi-gcc at firstfloor dot org
                   ` (2 preceding siblings ...)
  2011-10-07  5:58 ` jakub at gcc dot gnu.org
@ 2011-10-07 14:42 ` andi-gcc at firstfloor dot org
  2014-09-26 18:01 ` andi-gcc at firstfloor dot org
  2014-09-27  4:30 ` andi-gcc at firstfloor dot org
  5 siblings, 0 replies; 7+ messages in thread
From: andi-gcc at firstfloor dot org @ 2011-10-07 14:42 UTC (permalink / raw)
  To: gcc-bugs

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=50302

--- Comment #4 from Andi Kleen <andi-gcc at firstfloor dot org> 2011-10-07 14:40:02 UTC ---
Sorry yes my mistake.


^ permalink raw reply	[flat|nested] 7+ messages in thread
* [Bug target/50302] inefficient float->double conversion in AVX with -mtune=generic
  2011-09-05 23:08 [Bug target/50302] New: inefficient float->double conversion in AVX with -mtune=generic andi-gcc at firstfloor dot org
                   ` (3 preceding siblings ...)
  2011-10-07 14:42 ` andi-gcc at firstfloor dot org
@ 2014-09-26 18:01 ` andi-gcc at firstfloor dot org
  2014-09-27  4:30 ` andi-gcc at firstfloor dot org
  5 siblings, 0 replies; 7+ messages in thread
From: andi-gcc at firstfloor dot org @ 2014-09-26 18:01 UTC (permalink / raw)
  To: gcc-bugs

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=50302

--- Comment #5 from Andi Kleen <andi-gcc at firstfloor dot org> ---
Problem is still there on 

gcc version 4.8.3 20140624 (Red Hat 4.8.3-1) (GCC)


^ permalink raw reply	[flat|nested] 7+ messages in thread
* [Bug target/50302] inefficient float->double conversion in AVX with -mtune=generic
  2011-09-05 23:08 [Bug target/50302] New: inefficient float->double conversion in AVX with -mtune=generic andi-gcc at firstfloor dot org
                   ` (4 preceding siblings ...)
  2014-09-26 18:01 ` andi-gcc at firstfloor dot org
@ 2014-09-27  4:30 ` andi-gcc at firstfloor dot org
  5 siblings, 0 replies; 7+ messages in thread
From: andi-gcc at firstfloor dot org @ 2014-09-27  4:30 UTC (permalink / raw)
  To: gcc-bugs

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=50302

Andi Kleen <andi-gcc at firstfloor dot org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |RESOLVED
         Resolution|---                         |FIXED

--- Comment #6 from Andi Kleen <andi-gcc at firstfloor dot org> ---
Seems to be fixed now in 

gcc version 5.0.0 20140926 (experimental) (GCC) 


The double conversion is only generated for -mtune=amdfam10, but not for
mtune=generic


^ permalink raw reply	[flat|nested] 7+ messages in thread
end of thread, other threads:[~2014-09-27  4:30 UTC | newest]

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2011-09-05 23:08 [Bug target/50302] New: inefficient float->double conversion in AVX with -mtune=generic andi-gcc at firstfloor dot org
2011-09-06  7:53 ` [Bug target/50302] " rguenth at gcc dot gnu.org
2011-10-07  5:52 ` andi-gcc at firstfloor dot org
2011-10-07  5:58 ` jakub at gcc dot gnu.org
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