[Bug libfortran/78314] [aarch64] ieee_support_halting does not report unsupported fpu traps correctly
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=78314 --- Comment #31 from rsandifo at gcc dot gnu.org --- The previous patch skips the affected tests for now, on the basis that this PR is open and tracking the problem. The bug is very much still there though.
[Bug libfortran/78314] [aarch64] ieee_support_halting does not report unsupported fpu traps correctly
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=78314 --- Comment #30 from CVS Commits --- The master branch has been updated by Richard Sandiford : https://gcc.gnu.org/g:f44a2713da7ea8f5abde5b3a98ddf1ab97b9175a commit r11-8087-gf44a2713da7ea8f5abde5b3a98ddf1ab97b9175a Author: Richard Sandiford Date: Fri Apr 9 13:43:15 2021 +0100 testsuite: Skip gfortran.dg/ieee/ieee_[68].f90 for Arm targets [PR78314] For the reasons discussed in PR78314, ieee_support_halting doesn't work correctly for arm* and aarch64*. I think the easiest thing is to skip these tests until the PR is fixed. This doesn't mean that the PR is unimportant. It just doesn't seem useful to have the unpredictable failures described in the PR trail given that the problem is known and has been analysed. gcc/testsuite/ PR libfortran/78314 * gfortran.dg/ieee/ieee_6.f90: Skip for arm* and aarch64*. * gfortran.dg/ieee/ieee_8.f90: Likewise.
[Bug libfortran/78314] [aarch64] ieee_support_halting does not report unsupported fpu traps correctly
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=78314 --- Comment #29 from Maxim Kuvyrkov --- (In reply to Richard Earnshaw from comment #28) > The last release of gcc-7 has now been made, so it's end-of-life and no > further fixes for it will be made. Well, yes, but I'm about to build the final Linaro GCC 7.5 cross-toolchain releases, and I could fix the problem there. E.g., by backporting a fix from GCC-8 or reverting Uros's patch. Backporting from gcc-8 is preferred to reverting, obviously.
[Bug libfortran/78314] [aarch64] ieee_support_halting does not report unsupported fpu traps correctly
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=78314 --- Comment #28 from Richard Earnshaw --- The last release of gcc-7 has now been made, so it's end-of-life and no further fixes for it will be made.
[Bug libfortran/78314] [aarch64] ieee_support_halting does not report unsupported fpu traps correctly
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=78314 Maxim Kuvyrkov changed: What|Removed |Added CC||mkuvyrkov at gcc dot gnu.org --- Comment #27 from Maxim Kuvyrkov --- Hi, GCC 7.5 released with this bug, manifested by === gfortran Summary === FAIL: gfortran.dg/ieee/ieee_6.f90 -O0 execution test FAIL: gfortran.dg/ieee/ieee_6.f90 -O1 execution test FAIL: gfortran.dg/ieee/ieee_6.f90 -O2 execution test FAIL: gfortran.dg/ieee/ieee_6.f90 -O3 -fomit-frame-pointer -funroll-loops -fpeel-loops -ftracer -finline-functions execution test FAIL: gfortran.dg/ieee/ieee_6.f90 -O3 -g execution test FAIL: gfortran.dg/ieee/ieee_6.f90 -Os execution test XPASS: gfortran.dg/ieee/ieee_8.f90 -O0 execution test XPASS: gfortran.dg/ieee/ieee_8.f90 -O1 execution test XPASS: gfortran.dg/ieee/ieee_8.f90 -O2 execution test XPASS: gfortran.dg/ieee/ieee_8.f90 -O3 -fomit-frame-pointer -funroll-loops -fpeel-loops -ftracer -finline-functions execution test XPASS: gfortran.dg/ieee/ieee_8.f90 -O3 -g execution test XPASS: gfortran.dg/ieee/ieee_8.f90 -Os execution test Do we care enough about this to fix on GCC-7?
[Bug libfortran/78314] [aarch64] ieee_support_halting does not report unsupported fpu traps correctly
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=78314 Richard Biener changed: What|Removed |Added Target Milestone|7.5 |---
[Bug libfortran/78314] [aarch64] ieee_support_halting does not report unsupported fpu traps correctly
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=78314 Alex Bennée changed: What|Removed |Added CC||alex.bennee at linaro dot org --- Comment #26 from Alex Bennée --- Just to clear up the confusion on QEMU, we don't model any architectures that support FPU exceptions. The ieee_6 test broke recently when we fixed writes to the fpscr to make the exception enabling bits RAZ/WI as they should have been all along. Although we can use host FPU instructions (a fairly recent addition) we don't rely on their traps and I don't believe we would have actually delivered the trap. I suspect the test might be broken in that regard that it didn't check a trap had actually been delivered but I can't be sure as my fortran foo is a little lacking. The related QEMU bug is: https://bugs.launchpad.net/qemu/+bug/1836078
[Bug libfortran/78314] [aarch64] ieee_support_halting does not report unsupported fpu traps correctly
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=78314 --- Comment #25 from Wilco --- (In reply to Steve Ellcey from comment #24) > See email strings at: > > https://gcc.gnu.org/ml/fortran/2019-01/msg00276.html > https://gcc.gnu.org/ml/fortran/2019-02/msg00057.html > > For more discussion. Sure, it looks like we simply need to reinstate Szabolc's patch with a #ifdef arm/aarch64 around it. I need to find out whether a feclearexcept (FE_ALL_EXCEPT) is necessary on Arm targets which can trap (very few exist IIRC).
[Bug libfortran/78314] [aarch64] ieee_support_halting does not report unsupported fpu traps correctly
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=78314 --- Comment #24 from Steve Ellcey --- See email strings at: https://gcc.gnu.org/ml/fortran/2019-01/msg00276.html https://gcc.gnu.org/ml/fortran/2019-02/msg00057.html For more discussion.
[Bug libfortran/78314] [aarch64] ieee_support_halting does not report unsupported fpu traps correctly
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=78314 Wilco changed: What|Removed |Added CC||wilco at gcc dot gnu.org --- Comment #23 from Wilco --- (In reply to Steve Ellcey from comment #22) > It looks like the recent checkins are causing gfortran.dg/ieee/ieee_6.f90 > to fail on aarch64. Reading through the comments it looks like this isn't a > new problem but the failure showing up in the GCC testsuite run is new. Well it's a regression since it used to work in GCC7/8/9. Note it's incorrect to allow folding of these calls, for example support_fpu_flag can return true or false depending on the flag (FE_DENORMAL if not supported on most targets), and yet the constant folding always returns true for all flags.
[Bug libfortran/78314] [aarch64] ieee_support_halting does not report unsupported fpu traps correctly
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=78314 Steve Ellcey changed: What|Removed |Added CC||sje at gcc dot gnu.org --- Comment #22 from Steve Ellcey --- It looks like the recent checkins are causing gfortran.dg/ieee/ieee_6.f90 to fail on aarch64. Reading through the comments it looks like this isn't a new problem but the failure showing up in the GCC testsuite run is new.
[Bug libfortran/78314] [aarch64] ieee_support_halting does not report unsupported fpu traps correctly
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=78314 --- Comment #21 from uros at gcc dot gnu.org --- Author: uros Date: Sun Feb 3 16:21:06 2019 New Revision: 268493 URL: https://gcc.gnu.org/viewcvs?rev=268493&root=gcc&view=rev Log: 2019-02-03 Uroš Bizjak PR libfortran/88678 Revert: 2016-11-16 Szabolcs Nagy PR libfortran/78314 * config/fpu-glibc.h (support_fpu_trap): Use feenableexcept. 2019-02-03 Uroš Bizjak PR libfortran/88678 * config/fpu-glibc.h (set_fpu_trap_exceptions): Clear stalled exception flags before changing trap mode. Optimize to call feenableexcept and fedisableexcept only once. Modified: branches/gcc-7-branch/libgfortran/ChangeLog branches/gcc-7-branch/libgfortran/config/fpu-glibc.h
[Bug libfortran/78314] [aarch64] ieee_support_halting does not report unsupported fpu traps correctly
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=78314 --- Comment #20 from uros at gcc dot gnu.org --- Author: uros Date: Sun Feb 3 16:19:36 2019 New Revision: 268492 URL: https://gcc.gnu.org/viewcvs?rev=268492&root=gcc&view=rev Log: 2019-02-03 Uroš Bizjak PR libfortran/88678 Revert: 2016-11-16 Szabolcs Nagy PR libfortran/78314 * config/fpu-glibc.h (support_fpu_trap): Use feenableexcept. 2019-02-03 Uroš Bizjak PR libfortran/88678 * config/fpu-glibc.h (set_fpu_trap_exceptions): Clear stalled exception flags before changing trap mode. Optimize to call feenableexcept and fedisableexcept only once. Modified: branches/gcc-8-branch/libgfortran/ChangeLog branches/gcc-8-branch/libgfortran/config/fpu-glibc.h
[Bug libfortran/78314] [aarch64] ieee_support_halting does not report unsupported fpu traps correctly
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=78314 --- Comment #19 from Christophe Lyon --- (In reply to nsz from comment #18) > it's not a bug in the sense that the arm architecture > allows trap support (it's just not required), but it's > buggy that it would not report the support correctly > (e.g. enabling traps always succeed under qemu but > traps don't happen if the underlying hw has no support) OK, that was my suspicion. So, it seems hard to report a bug against qemu, then.
[Bug libfortran/78314] [aarch64] ieee_support_halting does not report unsupported fpu traps correctly
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=78314 --- Comment #18 from nsz at gcc dot gnu.org --- (In reply to Christophe Lyon from comment #16) > I've noticed this problem on arm and aarch64 native builds too. > But my cross-compilers (using QEMU as simulator) still pass this test. Does > this mean there is a bug in QEMU? qemu-user will just translate each guest fp operations to host fp operations, so if the host supports traps then you will see traps working. it's not a bug in the sense that the arm architecture allows trap support (it's just not required), but it's buggy that it would not report the support correctly (e.g. enabling traps always succeed under qemu but traps don't happen if the underlying hw has no support)
[Bug libfortran/78314] [aarch64] ieee_support_halting does not report unsupported fpu traps correctly
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=78314 --- Comment #17 from Uroš Bizjak --- (In reply to Christophe Lyon from comment #16) > I've noticed this problem on arm and aarch64 native builds too. > But my cross-compilers (using QEMU as simulator) still pass this test. Does > this mean there is a bug in QEMU? Looks like QEMU generates correct exceptions.
[Bug libfortran/78314] [aarch64] ieee_support_halting does not report unsupported fpu traps correctly
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=78314
Christophe Lyon changed:
What|Removed |Added
CC||clyon at gcc dot gnu.org
--- Comment #16 from Christophe Lyon ---
(In reply to Uroš Bizjak from comment #13)
> (In reply to nsz from comment #12)
> > i don't know how to change this to false for IEEE_SUPPORT_HALTING
> > on aarch64 and arm targets, but that would be a possible fix.
>
> --cut here--
> Index: libgfortran/config/fpu-glibc.h
> ===
> --- libgfortran/config/fpu-glibc.h (revision 268424)
> +++ libgfortran/config/fpu-glibc.h (working copy)
> @@ -129,6 +129,10 @@
> int
> support_fpu_trap (int flag)
> {
> +#if defined(__arm__) || defined(__aarch64__)
> + return 0;
> +#endif
> +
>return support_fpu_flag (flag);
> }
>
> --cut here--
I've noticed this problem on arm and aarch64 native builds too.
But my cross-compilers (using QEMU as simulator) still pass this test. Does
this mean there is a bug in QEMU?
[Bug libfortran/78314] [aarch64] ieee_support_halting does not report unsupported fpu traps correctly
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=78314 nsz at gcc dot gnu.org changed: What|Removed |Added Status|ASSIGNED|NEW Assignee|nsz at gcc dot gnu.org |unassigned at gcc dot gnu.org --- Comment #15 from nsz at gcc dot gnu.org --- i unassigned myself as i'm not working on this right now.
[Bug libfortran/78314] [aarch64] ieee_support_halting does not report unsupported fpu traps correctly
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=78314 --- Comment #14 from nsz at gcc dot gnu.org --- (In reply to Uroš Bizjak from comment #13) > (In reply to nsz from comment #12) > > i don't know how to change this to false for IEEE_SUPPORT_HALTING > > on aarch64 and arm targets, but that would be a possible fix. > > --cut here-- > Index: libgfortran/config/fpu-glibc.h that only turns the runtime check into "always false" but the compile time check is still "always true". which is still broken.
[Bug libfortran/78314] [aarch64] ieee_support_halting does not report unsupported fpu traps correctly
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=78314
--- Comment #13 from Uroš Bizjak ---
(In reply to nsz from comment #12)
> i don't know how to change this to false for IEEE_SUPPORT_HALTING
> on aarch64 and arm targets, but that would be a possible fix.
--cut here--
Index: libgfortran/config/fpu-glibc.h
===
--- libgfortran/config/fpu-glibc.h (revision 268424)
+++ libgfortran/config/fpu-glibc.h (working copy)
@@ -129,6 +129,10 @@
int
support_fpu_trap (int flag)
{
+#if defined(__arm__) || defined(__aarch64__)
+ return 0;
+#endif
+
return support_fpu_flag (flag);
}
--cut here--
[Bug libfortran/78314] [aarch64] ieee_support_halting does not report unsupported fpu traps correctly
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=78314
--- Comment #12 from nsz at gcc dot gnu.org ---
this got reverted because of bug 88678
and because compile time and runtime support_halting are different.
the compile time value is unconditionally true, which is wrong for
aarch64 and arm:
gcc/fortran/simplify.c:
gfc_expr *
simplify_ieee_support (gfc_expr *expr)
{
/* We consider that if the IEEE modules are loaded, we have full support
for flags, halting and rounding, which are the three functions
(IEEE_SUPPORT_{FLAG,HALTING,ROUNDING}) allowed in constant
expressions. One day, we will need libgfortran to detect support and
communicate it back to us, allowing for partial support. */
return gfc_get_logical_expr (gfc_default_logical_kind, &expr->where,
true);
}
i don't know how to change this to false for IEEE_SUPPORT_HALTING
on aarch64 and arm targets, but that would be a possible fix.
[Bug libfortran/78314] [aarch64] ieee_support_halting does not report unsupported fpu traps correctly
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=78314 Richard Biener changed: What|Removed |Added Target Milestone|7.4 |7.5
[Bug libfortran/78314] [aarch64] ieee_support_halting does not report unsupported fpu traps correctly
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=78314 --- Comment #11 from Richard Earnshaw --- (In reply to nsz from comment #10) > it turns out the ieee_* functions are allowed in const expressions so they > need to work at compile time too (see bug 78449), which of course won't work > if they need runtime detection. > > so now compile-time and runtime behaviour of ieee_support_halting is > different. > > so far no fortran expert clarified what is the expected semantics when you > can only decide this at runtime (e.g. it might be better to always return > false on targets that may not implement trapping, rather than report things > inconsistently compile- vs runtime). > > (i think this bug can be closed, but then the other one has to be reopened). Well the 'safe' answer in this case, when you can't be sure whether or not run-time traps will occur is surely to say 'no, they can't'. You might then get redundant code in the app that can't be reached, but at least it will still execute correctly.
[Bug libfortran/78314] [aarch64] ieee_support_halting does not report unsupported fpu traps correctly
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=78314 --- Comment #10 from nsz at gcc dot gnu.org --- it turns out the ieee_* functions are allowed in const expressions so they need to work at compile time too (see bug 78449), which of course won't work if they need runtime detection. so now compile-time and runtime behaviour of ieee_support_halting is different. so far no fortran expert clarified what is the expected semantics when you can only decide this at runtime (e.g. it might be better to always return false on targets that may not implement trapping, rather than report things inconsistently compile- vs runtime). (i think this bug can be closed, but then the other one has to be reopened).
[Bug libfortran/78314] [aarch64] ieee_support_halting does not report unsupported fpu traps correctly
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=78314 Martin Liška changed: What|Removed |Added CC||marxin at gcc dot gnu.org --- Comment #9 from Martin Liška --- nsz: Can the bug be marked as resolved?
[Bug libfortran/78314] [aarch64] ieee_support_halting does not report unsupported fpu traps correctly
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=78314 Richard Biener changed: What|Removed |Added Target Milestone|7.3 |7.4 --- Comment #8 from Richard Biener --- GCC 7.3 is being released, adjusting target milestone.
[Bug libfortran/78314] [aarch64] ieee_support_halting does not report unsupported fpu traps correctly
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=78314 Richard Biener changed: What|Removed |Added Target Milestone|7.2 |7.3
[Bug libfortran/78314] [aarch64] ieee_support_halting does not report unsupported fpu traps correctly
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=78314 Richard Biener changed: What|Removed |Added Target Milestone|7.2 |7.3 --- Comment #8 from Richard Biener --- GCC 7.2 is being released, adjusting target milestone. --- Comment #9 from Richard Biener --- GCC 7.2 is being released, adjusting target milestone.
[Bug libfortran/78314] [aarch64] ieee_support_halting does not report unsupported fpu traps correctly
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=78314 Richard Biener changed: What|Removed |Added Target Milestone|7.2 |7.3 --- Comment #8 from Richard Biener --- GCC 7.2 is being released, adjusting target milestone. --- Comment #9 from Richard Biener --- GCC 7.2 is being released, adjusting target milestone.
[Bug libfortran/78314] [aarch64] ieee_support_halting does not report unsupported fpu traps correctly
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=78314 Jakub Jelinek changed: What|Removed |Added Target Milestone|7.0 |7.2 --- Comment #7 from Jakub Jelinek --- GCC 7.1 has been released.
[Bug libfortran/78314] [aarch64] ieee_support_halting does not report unsupported fpu traps correctly
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=78314 nsz at gcc dot gnu.org changed: What|Removed |Added Status|NEW |ASSIGNED --- Comment #6 from nsz at gcc dot gnu.org --- waiting with the backport for bug 78449.
[Bug libfortran/78314] [aarch64] ieee_support_halting does not report unsupported fpu traps correctly
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=78314 --- Comment #5 from nsz at gcc dot gnu.org --- i plan to backport the fix, but it seems my fix is not correct and broke the ieee_8.fp90 test.
[Bug libfortran/78314] [aarch64] ieee_support_halting does not report unsupported fpu traps correctly
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=78314 --- Comment #4 from Dominique d'Humieres --- Any plan to back-port the fix? If no, could you please close the PR?
[Bug libfortran/78314] [aarch64] ieee_support_halting does not report unsupported fpu traps correctly
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=78314 nsz at gcc dot gnu.org changed: What|Removed |Added Target Milestone|--- |7.0 Known to fail||5.4.0, 6.2.0
[Bug libfortran/78314] [aarch64] ieee_support_halting does not report unsupported fpu traps correctly
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=78314 --- Comment #3 from nsz at gcc dot gnu.org --- Author: nsz Date: Wed Nov 16 17:27:04 2016 New Revision: 242505 URL: https://gcc.gnu.org/viewcvs?rev=242505&root=gcc&view=rev Log: [PR libgfortran/78314] Fix ieee_support_halting ieee_support_halting only checked the availability of status flags, not trapping support. On some targets the later can only be checked at runtime: feenableexcept reports if enabling traps failed. So check trapping support by enabling/disabling it. Updated the test that enabled trapping to check if it is supported. gcc/testsuite/ PR libgfortran/78314 * gfortran.dg/ieee/ieee_6.f90: Use ieee_support_halting. libgfortran/ PR libgfortran/78314 * config/fpu-glibc.h (support_fpu_trap): Use feenableexcept. Modified: trunk/gcc/testsuite/ChangeLog trunk/gcc/testsuite/gfortran.dg/ieee/ieee_6.f90 trunk/libgfortran/ChangeLog trunk/libgfortran/config/fpu-glibc.h
[Bug libfortran/78314] [aarch64] ieee_support_halting does not report unsupported fpu traps correctly
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=78314
Richard Earnshaw changed:
What|Removed |Added
Status|UNCONFIRMED |NEW
Last reconfirmed||2016-11-11
Ever confirmed|0 |1
--- Comment #2 from Richard Earnshaw ---
current code has
int
support_fpu_trap (int flag)
{
return support_fpu_flag (flag);
}
In other words, it assumes that if there is a flag for noting that an exception
has occurred, then it is also possible to trap on that flag being changed.
That's not a valid assumption for AArch64.
[Bug libfortran/78314] [aarch64] ieee_support_halting does not report unsupported fpu traps correctly
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=78314 --- Comment #1 from Andrew Pinski --- No wonder that one fails on thunderx.
