[Bug c/29186] optimzation breaks floating point exception flag reading

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=29186 Andrew Pinski changed: What|Removed |Added CC||pavel.morozkin at gmail dot com --- Comm

[Bug c/29186] optimzation breaks floating point exception flag reading

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. > >

[Bug c/29186] optimzation breaks floating point exception flag reading

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 there

[Bug c/29186] optimzation breaks floating point exception flag reading

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 f

[Bug c/29186] optimzation breaks floating point exception flag reading

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

[Bug c/29186] optimzation breaks floating point exception flag reading

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 su

[Bug c/29186] optimzation breaks floating point exception flag reading

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 > pos

[Bug c/29186] optimzation breaks floating point exception flag reading

-- fxcoudert at gcc dot gnu dot org changed: What|Removed |Added Status|UNCONFIRMED |NEW Ever Confirmed|0 |1 Last recon

[Bug c/29186] optimzation breaks floating point exception flag reading

--- 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

[Bug c/29186] optimzation breaks floating point exception flag reading

--- 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 tha

[Bug c/29186] optimzation breaks floating point exception flag reading

--- 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 elimin

[Bug c/29186] optimzation breaks floating point exception flag reading

--- 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 reco

[Bug c/29186] optimzation breaks floating point exception flag reading

--- Comment #16 from kreckel at ginac dot de 2006-10-31 11:48 --- A quote from : "While on the subject of miscreant compilers, we should remark their increasingly common tendency to reorder operations that can be executed con

[Bug c/29186] optimzation breaks floating point exception flag reading

--- 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. -- http://gcc.

[Bug c/29186] optimzation breaks floating point exception flag reading

--- 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 div

[Bug c/29186] optimzation breaks floating point exception flag reading

--- 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. -- http://gcc.gnu.org/bugzilla/show

[Bug c/29186] optimzation breaks floating point exception flag reading

-- kreckel at ginac dot de changed: What|Removed |Added Severity|enhancement |normal http://gcc.gnu.org/bugzilla/show_bug.cgi?id=29186

[Bug c/29186] optimzation breaks floating point exception flag reading

--- 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. -- kreckel at ginac dot de changed:

[Bug c/29186] optimzation breaks floating point exception flag reading

--- 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

[Bug c/29186] optimzation breaks floating point exception flag reading

--- 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. T

[Bug c/29186] optimzation breaks floating point exception flag reading

--- 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 eff

[Bug c/29186] optimzation breaks floating point exception flag reading

--- 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 re

[Bug c/29186] optimzation breaks floating point exception flag reading

--- 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 divisio

[Bug c/29186] optimzation breaks floating point exception flag reading

--- 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

[Bug c/29186] optimzation breaks floating point exception flag reading

--- 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

[Bug c/29186] optimzation breaks floating point exception flag reading

--- 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 poin

[Bug c/29186] optimzation breaks floating point exception flag reading

--- 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

[Bug c/29186] optimzation breaks floating point exception flag reading

--- 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. -- pinskia at gcc dot gnu dot org changed: What|Removed |Added ---

[Bug c/29186] optimzation breaks floating point exception flag reading

--- 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 -- http://gcc.gnu.org/bugzilla/show_bug.cgi?id=29186