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* [Bug c/53024] New: Power of 2 requirement on vector_size not documented
@ 2012-04-17 20:40 marc.glisse at normalesup dot org
2012-04-18 10:16 ` [Bug c/53024] " rguenth at gcc dot gnu.org
` (5 more replies)
0 siblings, 6 replies; 7+ messages in thread
From: marc.glisse at normalesup dot org @ 2012-04-17 20:40 UTC (permalink / raw)
To: gcc-bugs
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=53024
Bug #: 53024
Summary: Power of 2 requirement on vector_size not documented
Classification: Unclassified
Product: gcc
Version: 4.8.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c
AssignedTo: unassigned@gcc.gnu.org
ReportedBy: marc.glisse@normalesup.org
Hello,
typedef float VEC __attribute__ ((__vector_size__ (12)));
fails to compile with the message:
error: number of components of the vector not a power of two
This is quite clear, and I guess it makes sense. However,
http://gcc.gnu.org/onlinedocs/gcc/Vector-Extensions.html says:
"Specifying a combination that is not valid for the current architecture will
cause GCC to synthesize the instructions using a narrower mode."
so I was expecting gcc to handle it somehow. Could we add a sentence, anywhere
in that page, that makes the requirement that the size is a power of 2
explicit? Or if the requirement can be lifted... (I don't care so much about 3
float, I can just store 4 and ignore the last, but I do care about 12 double
and don't want to store 16 until we get 512bit vectors)
^ permalink raw reply [flat|nested] 7+ messages in thread
* [Bug c/53024] Power of 2 requirement on vector_size not documented
2012-04-17 20:40 [Bug c/53024] New: Power of 2 requirement on vector_size not documented marc.glisse at normalesup dot org
@ 2012-04-18 10:16 ` rguenth at gcc dot gnu.org
2012-09-27 10:06 ` glisse at gcc dot gnu.org
` (4 subsequent siblings)
5 siblings, 0 replies; 7+ messages in thread
From: rguenth at gcc dot gnu.org @ 2012-04-18 10:16 UTC (permalink / raw)
To: gcc-bugs
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=53024
Richard Guenther <rguenth at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Keywords| |documentation
Status|UNCONFIRMED |NEW
Last reconfirmed| |2012-04-18
Ever Confirmed|0 |1
--- Comment #1 from Richard Guenther <rguenth at gcc dot gnu.org> 2012-04-18 10:15:29 UTC ---
Confirmed as documentation issue. We can't easily lift this restriction
because we have
/* For a VECTOR_TYPE, this is the number of sub-parts of the vector. */
#define TYPE_VECTOR_SUBPARTS(VECTOR_TYPE) \
(((unsigned HOST_WIDE_INT) 1) \
<< VECTOR_TYPE_CHECK (VECTOR_TYPE)->type_common.precision)
and
struct GTY(()) tree_type_common {
...
unsigned int precision : 10;
10 bits of precision would limit us to vectors with 1024 elements if we'd
not have the power-of-two restriction. (not sure what a sane limit would be,
but 1024 byte vectors do not look too far off).
^ permalink raw reply [flat|nested] 7+ messages in thread
* [Bug c/53024] Power of 2 requirement on vector_size not documented
2012-04-17 20:40 [Bug c/53024] New: Power of 2 requirement on vector_size not documented marc.glisse at normalesup dot org
2012-04-18 10:16 ` [Bug c/53024] " rguenth at gcc dot gnu.org
@ 2012-09-27 10:06 ` glisse at gcc dot gnu.org
2012-09-27 10:14 ` glisse at gcc dot gnu.org
` (3 subsequent siblings)
5 siblings, 0 replies; 7+ messages in thread
From: glisse at gcc dot gnu.org @ 2012-09-27 10:06 UTC (permalink / raw)
To: gcc-bugs
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=53024
--- Comment #2 from Marc Glisse <glisse at gcc dot gnu.org> 2012-09-27 10:06:29 UTC ---
Author: glisse
Date: Thu Sep 27 10:06:23 2012
New Revision: 191800
URL: http://gcc.gnu.org/viewcvs?root=gcc&view=rev&rev=191800
Log:
2012-09-27 Marc Glisse <marc.glisse@inria.fr>
PR c/53024
PR c++/54427
* gcc/doc/extend.texi (Vector Extensions): C++ improvements.
Power of 2 size requirement.
Modified:
trunk/gcc/ChangeLog
trunk/gcc/doc/extend.texi
^ permalink raw reply [flat|nested] 7+ messages in thread
* [Bug c/53024] Power of 2 requirement on vector_size not documented
2012-04-17 20:40 [Bug c/53024] New: Power of 2 requirement on vector_size not documented marc.glisse at normalesup dot org
2012-04-18 10:16 ` [Bug c/53024] " rguenth at gcc dot gnu.org
2012-09-27 10:06 ` glisse at gcc dot gnu.org
@ 2012-09-27 10:14 ` glisse at gcc dot gnu.org
2012-11-16 16:06 ` [Bug middle-end/53024] Support vector_size that is not a power of 2 glisse at gcc dot gnu.org
` (2 subsequent siblings)
5 siblings, 0 replies; 7+ messages in thread
From: glisse at gcc dot gnu.org @ 2012-09-27 10:14 UTC (permalink / raw)
To: gcc-bugs
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=53024
Marc Glisse <glisse at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
CC| |glisse at gcc dot gnu.org
--- Comment #3 from Marc Glisse <glisse at gcc dot gnu.org> 2012-09-27 10:14:38 UTC ---
Documentation fixed.
It might make sense to keep it open as a RFE to support non-powers of 2 some
time in the distant future. I'll retitle the bug in a few days if there are no
comments.
^ permalink raw reply [flat|nested] 7+ messages in thread
* [Bug middle-end/53024] Support vector_size that is not a power of 2
2012-04-17 20:40 [Bug c/53024] New: Power of 2 requirement on vector_size not documented marc.glisse at normalesup dot org
` (2 preceding siblings ...)
2012-09-27 10:14 ` glisse at gcc dot gnu.org
@ 2012-11-16 16:06 ` glisse at gcc dot gnu.org
2012-11-16 18:18 ` pinskia at gcc dot gnu.org
2012-11-16 20:03 ` glisse at gcc dot gnu.org
5 siblings, 0 replies; 7+ messages in thread
From: glisse at gcc dot gnu.org @ 2012-11-16 16:06 UTC (permalink / raw)
To: gcc-bugs
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=53024
Marc Glisse <glisse at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Component|c |middle-end
Summary|Power of 2 requirement on |Support vector_size that is
|vector_size not documented |not a power of 2
Severity|normal |enhancement
--- Comment #4 from Marc Glisse <glisse at gcc dot gnu.org> 2012-11-16 16:06:28 UTC ---
Not a priority.
^ permalink raw reply [flat|nested] 7+ messages in thread
* [Bug middle-end/53024] Support vector_size that is not a power of 2
2012-04-17 20:40 [Bug c/53024] New: Power of 2 requirement on vector_size not documented marc.glisse at normalesup dot org
` (3 preceding siblings ...)
2012-11-16 16:06 ` [Bug middle-end/53024] Support vector_size that is not a power of 2 glisse at gcc dot gnu.org
@ 2012-11-16 18:18 ` pinskia at gcc dot gnu.org
2012-11-16 20:03 ` glisse at gcc dot gnu.org
5 siblings, 0 replies; 7+ messages in thread
From: pinskia at gcc dot gnu.org @ 2012-11-16 18:18 UTC (permalink / raw)
To: gcc-bugs
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=53024
--- Comment #5 from Andrew Pinski <pinskia at gcc dot gnu.org> 2012-11-16 18:18:16 UTC ---
I don't think we can ever support vector size of non power 2 size.
^ permalink raw reply [flat|nested] 7+ messages in thread
* [Bug middle-end/53024] Support vector_size that is not a power of 2
2012-04-17 20:40 [Bug c/53024] New: Power of 2 requirement on vector_size not documented marc.glisse at normalesup dot org
` (4 preceding siblings ...)
2012-11-16 18:18 ` pinskia at gcc dot gnu.org
@ 2012-11-16 20:03 ` glisse at gcc dot gnu.org
5 siblings, 0 replies; 7+ messages in thread
From: glisse at gcc dot gnu.org @ 2012-11-16 20:03 UTC (permalink / raw)
To: gcc-bugs
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=53024
--- Comment #6 from Marc Glisse <glisse at gcc dot gnu.org> 2012-11-16 20:03:05 UTC ---
(In reply to comment #5)
> I don't think we can ever support vector size of non power 2 size.
I don't think we *will* ever support them (too much work, too little benefit),
but I am not sure why we couldn't in principle.
^ permalink raw reply [flat|nested] 7+ messages in thread
end of thread, other threads:[~2012-11-16 20:03 UTC | newest]
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2012-04-17 20:40 [Bug c/53024] New: Power of 2 requirement on vector_size not documented marc.glisse at normalesup dot org
2012-04-18 10:16 ` [Bug c/53024] " rguenth at gcc dot gnu.org
2012-09-27 10:06 ` glisse at gcc dot gnu.org
2012-09-27 10:14 ` glisse at gcc dot gnu.org
2012-11-16 16:06 ` [Bug middle-end/53024] Support vector_size that is not a power of 2 glisse at gcc dot gnu.org
2012-11-16 18:18 ` pinskia at gcc dot gnu.org
2012-11-16 20:03 ` glisse at gcc dot gnu.org
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