https://gcc.gnu.org/bugzilla/show_bug.cgi?id=29186
Andrew Pinski changed:
What|Removed |Added
CC||pavel.morozkin at gmail dot com
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=29186
--- Comment #26 from Richard Biener ---
(In reply to Richard B. Kreckel from comment #25)
> (In reply to Richard Biener from comment #24)
> > So you're just lucky indeed ...
>
> This makes me wonder if there is still a way to trigger this.
>
>
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=29186
--- Comment #25 from Richard B. Kreckel ---
(In reply to Richard Biener from comment #24)
> So you're just lucky indeed ...
This makes me wonder if there is still a way to trigger this.
You suggest this has been fixed for the division (is
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=29186
--- Comment #24 from Richard Biener ---
For the division when GCC doesn't know the divident is not zero I think we
actually fixed the bug but yes, in general FP operation reordering wrt FP
env access isn't fixed.
But GCC needs to consider that
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=29186
--- Comment #23 from Marc Glisse ---
(In reply to Richard B. Kreckel from comment #22)
> I can't reproduce this bug any more,
I think you are just lucky, I am sure it hasn't been fixed and gcc will still
happily swap FP operations with function
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=29186
--- Comment #22 from Richard B. Kreckel ---
I can't reproduce this bug any more, with any of the optimization settings on
x86 or x86_64 going back as far as GCC 4.9.2. Delighted to see that this has
been addressed in the meantime (even without
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=29186
--- Comment #21 from Eric Gallager ---
(In reply to Richard B. Kreckel from comment #20)
> So, Joseph explained that the code should execute as expected, at least with
> -frounding-math as a workaround. However, with GCC 4.4 it is still not
>
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fxcoudert at gcc dot gnu dot org changed:
What|Removed |Added
Status|UNCONFIRMED |NEW
Ever Confirmed|0 |1
Last
--- Comment #20 from kreckel at ginac dot de 2009-05-04 06:47 ---
So, Joseph explained that the code should execute as expected, at least with
-frounding-math as a workaround. However, with GCC 4.4 it is still not possible
to write code that takes advantage of those advanced features of
--- Comment #18 from kreckel at ginac dot de 2006-11-19 11:22 ---
An idea: Would it help if feholdexcept, fetestexcept and all those standard
functions accessing the status and control flags were implemented as builtins,
not as extern libcalls?
This probably wouldn't help against
--- Comment #19 from rguenth at gcc dot gnu dot org 2006-11-19 12:14
---
The problem is that the division is in no ways special to optimizers. One
possibility I see would be to introduce either a builtin function or a new
tree-code to access the exception flags. Of course the fact
--- Comment #17 from kreckel at ginac dot de 2006-11-06 22:23 ---
(In reply to comment #15)
Maybe scheduling would have the same issue. The fact that the result of the
division is not used is a red herring, though. Of course, the assumption is
that it's actually used.
For the
--- Comment #16 from kreckel at ginac dot de 2006-10-31 11:48 ---
A quote from http://www.cs.berkeley.edu/~wkahan/ieee754status/IEEE754.PDF:
While on the subject of miscreant compilers, we should remark their
increasingly common tendency to reorder operations that can be executed
--- Comment #13 from kreckel at ginac dot de 2006-10-25 07:54 ---
(In reply to comment #12)
It doesn't disappear with -fno-tree-ter, as I would assume if it were a TER
bug.
I just discovered that it does disappear with -fno-tree-sink, though.
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--- Comment #14 from pinskia at gcc dot gnu dot org 2006-10-25 07:57
---
So what is happening is there explict barrier for the divide so we assume we
can move it. I don't know what the correct thing is really, scheduling will
have the same issue and so will being able to delete the
--- Comment #15 from kreckel at ginac dot de 2006-10-25 13:22 ---
(In reply to comment #14)
Maybe scheduling would have the same issue. The fact that the result of the
division is not used is a red herring, though. Of course, the assumption is
that it's actually used.
--
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kreckel at ginac dot de changed:
What|Removed |Added
Severity|enhancement |normal
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=29186
--- Comment #12 from kreckel at ginac dot de 2006-09-24 16:51 ---
(In reply to comment #11)
This is a TER bug then and I really doubt it can be fixed easy.
It doesn't disappear with -fno-tree-ter, as I would assume if it were a TER
bug.
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kreckel at ginac dot de changed:
--- Comment #5 from kreckel at ginac dot de 2006-09-23 21:41 ---
(In reply to comment #3)
So this is not a bug except for the fact GCC does not implement #pragma STDC
FENV_ACCESS
According to C99, 7.6.1, you are technically right. But still: an
implementation that does not allow
--- Comment #6 from joseph at codesourcery dot com 2006-09-23 21:52 ---
Subject: Re: optimzation breaks floating point exception flag
reading
On Sat, 23 Sep 2006, kreckel at ginac dot de wrote:
According to C99, 7.6.1, you are technically right. But still: an
implementation that
--- Comment #7 from kreckel at ginac dot de 2006-09-23 22:11 ---
(In reply to comment #6)
Use -frounding-math to enable FENV_ACCESS for the whole translation unit,
Sorry, I fail to see what -frounding-math has to do with this. The example in
comment #5 was about overflows and
--- Comment #8 from joseph at codesourcery dot com 2006-09-23 22:19 ---
Subject: Re: optimzation breaks floating point exception flag
reading
On Sat, 23 Sep 2006, kreckel at ginac dot de wrote:
--- Comment #7 from kreckel at ginac dot de 2006-09-23 22:11 ---
(In reply
--- Comment #9 from kreckel at ginac dot de 2006-09-23 22:58 ---
(In reply to comment #8)
I am still not entirely sure whether we are really talking about the same
problem. The original problem was that the compiler optimized assuming that the
floating point division cannot have side
--- Comment #10 from joseph at codesourcery dot com 2006-09-23 23:02
---
Subject: Re: optimzation breaks floating point exception flag
reading
On Sat, 23 Sep 2006, kreckel at ginac dot de wrote:
I am still not entirely sure whether we are really talking about the same
problem.
--- Comment #11 from pinskia at gmail dot com 2006-09-24 00:34 ---
Subject: Re: optimzation breaks floating point exception flag
reading
On Sat, 2006-09-23 at 23:02 +, joseph at codesourcery dot com wrote:
In that case you have a bug that is not a duplicate of the lack of
--- Comment #1 from pinskia at gcc dot gnu dot org 2006-09-22 19:24 ---
This is not really a bug in C99 unless you use:
#pragma STDC FENV_ACCESS on
But then again we don't implement that pramgma yet
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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=29186
--- Comment #2 from pinskia at gcc dot gnu dot org 2006-09-22 19:25 ---
PR 20785 has a patch but it has not been applied.
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pinskia at gcc dot gnu dot org changed:
What|Removed |Added
--- Comment #3 from pinskia at gcc dot gnu dot org 2006-09-22 19:27 ---
So this is not a bug except for the fact GCC does not implement #pragma STDC
FENV_ACCESS
*** This bug has been marked as a duplicate of 20785 ***
--
pinskia at gcc dot gnu dot org changed:
What
--- Comment #4 from kreckel at ginac dot de 2006-09-22 22:34 ---
(In reply to comment #1)
This is not really a bug in C99 unless you use:
#pragma STDC FENV_ACCESS on
But then again we don't implement that pramgma yet
Okay, I was not aware of that pragma. Thank you for
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