[Bug ada/51483] New: [4.7 regression] Ada's cstand.adb:Register_Float_Type makes invalid assumptions about FP representation

[Bug ada/51483] New: [4.7 regression] Ada's cstand.adb:Register_Float_Type makes invalid assumptions about FP representation

[mikpe at it dot uu.se]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=51483

             Bug #: 51483
           Summary: [4.7 regression] Ada's cstand.adb:Register_Float_Type
                    makes invalid assumptions about FP representation
    Classification: Unclassified
           Product: gcc
           Version: 4.7.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: ada
        AssignedTo: unassigned@gcc.gnu.org
        ReportedBy: mikpe@it.uu.se


Redirected from PR48835:

Attempting to build an Ada-enabled gcc-4.7 cross to m68k-linux fails with:

/tmp/objdir/./gcc/xgcc -B/tmp/objdir/./gcc/
-B/home/mikpe/pkgs/linux-x86/cross-m68k/m68k-unknown-linux/bin/
-B/home/mikpe/pkgs/linux-x86/cross-m68k/m68k-unknown-linux/lib/ -isystem
/home/mikpe/pkgs/linux-x86/cross-m68k/m68k-unknown-linux/include -isystem
/home/mikpe/pkgs/linux-x86/cross-m68k/m68k-unknown-linux/sys-include    -c -g
-O2   -W -Wall -gnatpg -nostdinc   a-assert.adb -o a-assert.o
+===========================GNAT BUG DETECTED==============================+
| 4.7.0 20111203 (experimental) (m68k-unknown-linux) GCC error:            |
| in fp_size_to_prec, at ada/gcc-interface/misc.c:781                      |

(you don't need the m68k-linux Ada support patch for this, vanilla upstream gcc
sources suffice)

This worked up to r177136, but broke due to r177137+177141.

Eric Botcazou commented:
> No, but the new code (cstand.adb:Register_Float_Type) makes an invalid
> assumption about the size of a FP mode given its precision and alignment,
> instead of using the proper interface.  enumerate_modes should probably pass
> GET_MODE_BITSIZE to its callback.  I'd suggest opening a new regression PR for
> this problem.

[Bug ada/51483] [4.7 regression] Ada's cstand.adb:Register_Float_Type makes invalid assumptions about FP representation

[rguenth at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=51483

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
   Target Milestone|---                         |4.7.0

[Bug ada/51483] [4.7 regression] cstand.adb:Register_Float_Type makes invalid assumptions about FP representation

[ebotcazou at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=51483

Eric Botcazou <ebotcazou at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Keywords|                            |build
             Status|UNCONFIRMED                 |NEW
   Last reconfirmed|                            |2011-12-09
                 CC|                            |bosch at gcc dot gnu.org,
                   |                            |ebotcazou at gcc dot
                   |                            |gnu.org
             Blocks|                            |48835
            Summary|[4.7 regression] Ada's      |[4.7 regression]
                   |cstand.adb:Register_Float_T |cstand.adb:Register_Float_T
                   |ype makes invalid           |ype makes invalid
                   |assumptions about FP        |assumptions about FP
                   |representation              |representation
     Ever Confirmed|0                           |1
      Known to fail|                            |4.7.0

--- Comment #1 from Eric Botcazou <ebotcazou at gcc dot gnu.org> 2011-12-09 14:30:29 UTC ---
This doesn't show up on i386 because XFmode is overaligned for this arch.

[Bug ada/51483] [4.7 regression] cstand.adb:Register_Float_Type makes invalid assumptions about FP representation

[jakub at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=51483

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Priority|P3                          |P4
                 CC|                            |jakub at gcc dot gnu.org

[Bug ada/51483] [4.7 regression] cstand.adb:Register_Float_Type makes invalid assumptions about FP representation

[schwab@linux-m68k.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=51483

--- Comment #2 from Andreas Schwab <schwab@linux-m68k.org> 2012-01-09 21:35:02 UTC ---
Created attachment 26285
  --> http://gcc.gnu.org/bugzilla/attachment.cgi?id=26285
Patch

[Bug ada/51483] [4.7 regression] cstand.adb:Register_Float_Type makes invalid assumptions about FP representation

[ebotcazou at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=51483

--- Comment #3 from Eric Botcazou <ebotcazou at gcc dot gnu.org> 2012-01-09 23:45:23 UTC ---
> Created attachment 26285 [details]
> Patch

I don't think it's correct.  Like the middle-end, the Ada front-end has a
notion of precision (RM_Size) and a notion of size (Esize), so we need to pass
both to the front-end.  But I'll let Geert comment here.

[Bug ada/51483] [4.7 regression] cstand.adb:Register_Float_Type makes invalid assumptions about FP representation

[schwab@linux-m68k.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=51483

--- Comment #4 from Andreas Schwab <schwab@linux-m68k.org> 2012-01-10 00:16:58 UTC ---
The front-end has never made that distinction for floating point types.

[Bug ada/51483] [4.7 regression] cstand.adb:Register_Float_Type makes invalid assumptions about FP representation

[bosch at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=51483

--- Comment #5 from Geert Bosch <bosch at gcc dot gnu.org> 2012-01-10 02:55:46 UTC ---
If I understand correctly, you're changing the interface to pass the object
size (Esize) instead of the precision (RM_Size). That is not correct.

Right now, we have the assumption that we can derive the Esize from the RM_Size
rounded up to the alignment. What I don't quite understand right now is what
the properties of the M68K type are. What is the precision, size and alignment?

If necessary, we can pass both Esize and RM_Size, but the current change seems
like it would break other targets.

  -Geert

[Bug ada/51483] [4.7 regression] cstand.adb:Register_Float_Type makes invalid assumptions about FP representation

[schwab@linux-m68k.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=51483

--- Comment #6 from Andreas Schwab <schwab@linux-m68k.org> 2012-01-10 09:24:48 UTC ---
> If I understand correctly, you're changing the interface to pass the object
> size (Esize) instead of the precision (RM_Size). That is not correct.

I'm just restoring previous behaviour.

> Right now, we have the assumption that we can derive the Esize from the RM_Size
> rounded up to the alignment.

That completely ignores padding.

> If necessary, we can pass both Esize and RM_Size, but the current change seems
> like it would break other targets.

Those targets would have been broken before.  Since nobody appeared to complain
so far, those targets don't exit.

[Bug ada/51483] [4.7 regression] cstand.adb:Register_Float_Type makes invalid assumptions about FP representation

[mikpe at it dot uu.se]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=51483

--- Comment #7 from Mikael Pettersson <mikpe at it dot uu.se> 2012-01-30 10:51:11 UTC ---
Any chance this could be resolved before the 4.7.0 release?  It would be a
shame if Ada support for m68k would be impossible due to something as lame as
FP format confusion/disagreement.

[Bug ada/51483] [4.7 regression] cstand.adb:Register_Float_Type makes invalid assumptions about FP representation

[mikpe at it dot uu.se]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=51483

--- Comment #8 from Mikael Pettersson <mikpe at it dot uu.se> 2012-01-30 23:56:33 UTC ---
Created attachment 26524
  --> http://gcc.gnu.org/bugzilla/attachment.cgi?id=26524
pass both precision and storage size to Register_Float_Type

Patch I'm testing.  Works on i686-linux.  Unfortunately all post-20110730
snapshots seem to suffer from additional build failures (for m68k at least) so
I haven't been able to build a cross yet.  The first one I need to figure out
is:

/tmp/gcc-4.7-20110820/gcc/ada -g -O2 -W -Wall -Wwrite-strings
-Wstrict-prototypes -Wmissing-prototypes -gnatpg -gnata -I-
/tmp/gcc-4.7-20110820/gcc/ada/ali-util.adb
scng.adb:1799:47: "SPARK" is undefined
gnatmake: "/tmp/gcc-4.7-20110820/gcc/ada/ali-util.adb" compilation error

[Bug ada/51483] [4.7 regression] cstand.adb:Register_Float_Type makes invalid assumptions about FP representation

[mikpe at it dot uu.se]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=51483

--- Comment #9 from Mikael Pettersson <mikpe at it dot uu.se> 2012-02-01 12:42:44 UTC ---
(In reply to comment #8)
> /tmp/gcc-4.7-20110820/gcc/ada -g -O2 -W -Wall -Wwrite-strings
> -Wstrict-prototypes -Wmissing-prototypes -gnatpg -gnata -I-
> /tmp/gcc-4.7-20110820/gcc/ada/ali-util.adb
> scng.adb:1799:47: "SPARK" is undefined
> gnatmake: "/tmp/gcc-4.7-20110820/gcc/ada/ali-util.adb" compilation error

This is a generic problem affecting all cross-builds, caused by r177183.  For
instance, a gcc-4.6.2 host gcc fails to build gcc-4.7-20120128 as a cross to
sparc64-linux with the above error, even though native builds on sparc64-linux
have no problems building the same gcc-4.7-20120128 with an even older
gcc-4.4.6 host compiler.

However, in the brief period between r177141 and r177183, applying my tentative
patch did allow a successful build of a gcc-4.7 cross to m68k w/ ada, so I'll
try a native bootstrap with it soonish.

[Bug ada/51483] [4.7 regression] cstand.adb:Register_Float_Type makes invalid assumptions about FP representation

[mikpe at it dot uu.se]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=51483

--- Comment #10 from Mikael Pettersson <mikpe at it dot uu.se> 2012-02-29 19:18:37 UTC ---
(In reply to comment #9)
> applying my tentative
> patch did allow a successful build of a gcc-4.7 cross to m68k w/ ada, so I'll
> try a native bootstrap with it soonish.

Native bootstrap of 4.7-20120225 plus my proposed fix for this PR, the base
m68k-linux Ada support patch from PR48835, and the proposed fix for the cc0 bug
in PR49847, with Ada enabled, did succeed.

[Bug ada/51483] [4.7/4.8 regression] cstand.adb:Register_Float_Type makes invalid assumptions about FP representation

[rguenth at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=51483

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
   Target Milestone|4.7.0                       |4.7.1

--- Comment #11 from Richard Guenther <rguenth at gcc dot gnu.org> 2012-03-22 08:26:05 UTC ---
GCC 4.7.0 is being released, adjusting target milestone.

[Bug ada/51483] [4.7/4.8 regression] cstand.adb:Register_Float_Type makes invalid assumptions about FP representation

[rguenth at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=51483

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
   Target Milestone|4.7.1                       |4.7.2

--- Comment #12 from Richard Guenther <rguenth at gcc dot gnu.org> 2012-06-14 08:13:02 UTC ---
GCC 4.7.1 is being released, adjusting target milestone.

[Bug ada/51483] [4.7/4.8 regression] cstand.adb:Register_Float_Type makes invalid assumptions about FP representation

[jakub at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=51483

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
   Target Milestone|4.7.2                       |4.7.3

--- Comment #13 from Jakub Jelinek <jakub at gcc dot gnu.org> 2012-09-20 10:13:04 UTC ---
GCC 4.7.2 has been released.

[Bug ada/51483] [4.7/4.8 regression] cstand.adb:Register_Float_Type makes invalid assumptions about FP representation

[cynt6007 at vandals dot uidaho.edu]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=51483

cynt6007 at vandals dot uidaho.edu changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |cynt6007 at vandals dot
                   |                            |uidaho.edu

--- Comment #14 from cynt6007 at vandals dot uidaho.edu 2013-02-04 00:07:31 UTC ---
Can't build Ada/gnat-4.7 on Ubuntu 12.10 because of SPARK issue, although there
are long and complicated directions for how to build Ada/gnat-4.7 on Ubuntu,
some work and some don't.  Per GNU standards, the build system should be
changed so that it's possible to build gnat-4.7 with gnat-4.6. Also, if a
native compiler of the same version number must be built to build gnat, then
the build system should (but fails to) automatically build the native version
first, then use that to build the cross compiler.

[Bug ada/51483] [4.7/4.8 regression] cstand.adb:Register_Float_Type makes invalid assumptions about FP representation

[ebotcazou at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=51483

--- Comment #15 from Eric Botcazou <ebotcazou at gcc dot gnu.org> 2013-02-04 07:15:31 UTC ---
> Can't build Ada/gnat-4.7 on Ubuntu 12.10 because of SPARK issue, although there
> are long and complicated directions for how to build Ada/gnat-4.7 on Ubuntu,
> some work and some don't.  Per GNU standards, the build system should be
> changed so that it's possible to build gnat-4.7 with gnat-4.6. Also, if a
> native compiler of the same version number must be built to build gnat, then
> the build system should (but fails to) automatically build the native version
> first, then use that to build the cross compiler.

This PR has nothing to do with the build system though.

[Bug ada/51483] [4.7/4.8/4.9 regression] cstand.adb:Register_Float_Type makes invalid assumptions about FP representation

[rguenth at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=51483

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
   Target Milestone|4.7.3                       |4.7.4

--- Comment #16 from Richard Biener <rguenth at gcc dot gnu.org> 2013-04-11 07:58:53 UTC ---
GCC 4.7.3 is being released, adjusting target milestone.

[Bug ada/51483] [4.7/4.8/4.9 regression] cstand.adb:Register_Float_Type makes invalid assumptions about FP representation

[law at redhat dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=51483

--- Comment #17 from Jeffrey A. Law <law at redhat dot com> ---
Eric, there's an updated patch in c#8 which reportedly fixes the problem by
passing both the precision and storage size of Register_Float_Type.

I'm nowhere near versed enough in Ada to know if Mikael's on the right track
with that patch. It's been sitting there for ~2 years now ;(

The SPARK issues in c#14 is separate and we should probably create a distinct
BZ for that since I believe it completely stands in the way bootstrapping Ada
on platforms without a functional Ada compiler.

If you could help move along these issues, it'd be appreciated.

Thanks,
Jeff

[Bug ada/51483] [4.7/4.8/4.9 regression] cstand.adb:Register_Float_Type makes invalid assumptions about FP representation

[ebotcazou at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=51483

--- Comment #18 from Eric Botcazou <ebotcazou at gcc dot gnu.org> ---
> Eric, there's an updated patch in c#8 which reportedly fixes the problem by
> passing both the precision and storage size of Register_Float_Type.

Right, this is the way to go.

> I'm nowhere near versed enough in Ada to know if Mikael's on the right track
> with that patch. It's been sitting there for ~2 years now ;(
> 
> The SPARK issues in c#14 is separate and we should probably create a
> distinct BZ for that since I believe it completely stands in the way
> bootstrapping Ada on platforms without a functional Ada compiler.
> 
> If you could help move along these issues, it'd be appreciated.

Geert, could you have a look at the patch?

[Bug ada/51483] [4.7/4.8/4.9 regression] cstand.adb:Register_Float_Type makes invalid assumptions about FP representation

[ebotcazou at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=51483

Eric Botcazou <ebotcazou at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|ebotcazou at gcc dot gnu.org       |
           Assignee|unassigned at gcc dot gnu.org      |ebotcazou at gcc dot gnu.org

--- Comment #19 from Eric Botcazou <ebotcazou at gcc dot gnu.org> ---
Taking care of it.

[Bug ada/51483] [4.7/4.8/4.9 regression] cstand.adb:Register_Float_Type makes invalid assumptions about FP representation

[ebotcazou at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=51483

Eric Botcazou <ebotcazou at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |ASSIGNED

[Bug ada/51483] [4.7/4.8/4.9 regression] cstand.adb:Register_Float_Type makes invalid assumptions about FP representation

[bosch at adacore dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=51483

--- Comment #20 from bosch at adacore dot com <bosch at adacore dot com> ---
On Mar 10, 2014, at 16:11, ebotcazou at gcc dot gnu.org
<gcc-bugzilla@gcc.gnu.org> wrote:

> --- Comment #19 from Eric Botcazou <ebotcazou at gcc dot gnu.org> ---
> Taking care of it.
> 

Thank you!

  -Geert

[Bug ada/51483] [4.7/4.8/4.9 regression] cstand.adb:Register_Float_Type makes invalid assumption about FP modes

[ebotcazou at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=51483

--- Comment #21 from Eric Botcazou <ebotcazou at gcc dot gnu.org> ---
Author: ebotcazou
Date: Thu Mar 13 15:42:21 2014
New Revision: 208546

URL: http://gcc.gnu.org/viewcvs?rev=208546&root=gcc&view=rev
Log:
    PR ada/51483
    * cstand.adb (Register_Float_Type): Add 'precision' parameter and use
    it to set the RM size.  Use directly 'size' for the Esize.
    (Create_Back_End_Float_Types): Adjust call to above.
    * get_targ.ads (Register_Type_Proc): Add 'precision' parameter.
    * set_targ.ads (FPT_Mode_Entry): Add 'precision' component.
    (Write_Target_Dependent_Values): Adjust comment.
    * set_targ.adb (Register_Float_Type): Add 'precision' parameter and
    deal with it.
    (Write_Target_Dependent_Values): Write the precision in lieu of size.
    (Initialization): Read the precision in lieu of size and compute the
    size from the precision and the alignment.
    * gcc-interface/gigi.h (enumerate_modes): Add integer parameter.
    * gcc-interface/misc.c (enumerate_modes): Likewise.  Do not register
    types for vector modes, pass the size in addition to the precision.

Modified:
    trunk/gcc/ada/ChangeLog
    trunk/gcc/ada/cstand.adb
    trunk/gcc/ada/gcc-interface/gigi.h
    trunk/gcc/ada/gcc-interface/misc.c
    trunk/gcc/ada/get_targ.ads
    trunk/gcc/ada/set_targ.adb
    trunk/gcc/ada/set_targ.ads

[Bug ada/51483] [4.7/4.8/4.9 regression] cstand.adb:Register_Float_Type makes invalid assumption about FP modes

[ebotcazou at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=51483

--- Comment #22 from Eric Botcazou <ebotcazou at gcc dot gnu.org> ---
Author: ebotcazou
Date: Thu Mar 13 15:42:42 2014
New Revision: 208547

URL: http://gcc.gnu.org/viewcvs?rev=208547&root=gcc&view=rev
Log:
    PR ada/51483
    * back_end.ads (Register_Type_Proc): Add 'precision' parameter.
    * cstand.adb (Register_Float_Type): Add 'precision' parameter and use
    it to set the RM size.  Use directly 'size' for the Esize.
    * gcc-interface/gigi.h (enumerate_modes): Add integer parameter.
    * gcc-interface/misc.c (enumerate_modes): Likewise.  Do not register
    types for vector modes, pass the size in addition to the precision.

Modified:
    branches/gcc-4_8-branch/gcc/ada/ChangeLog
    branches/gcc-4_8-branch/gcc/ada/back_end.ads
    branches/gcc-4_8-branch/gcc/ada/cstand.adb
    branches/gcc-4_8-branch/gcc/ada/gcc-interface/gigi.h
    branches/gcc-4_8-branch/gcc/ada/gcc-interface/misc.c

[Bug ada/51483] [4.7/4.8/4.9 regression] cstand.adb:Register_Float_Type makes invalid assumption about FP modes

[ebotcazou at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=51483

--- Comment #23 from Eric Botcazou <ebotcazou at gcc dot gnu.org> ---
Author: ebotcazou
Date: Thu Mar 13 15:43:01 2014
New Revision: 208548

URL: http://gcc.gnu.org/viewcvs?rev=208548&root=gcc&view=rev
Log:
    PR ada/51483
    * back_end.ads (Register_Type_Proc): Add 'precision' parameter.
    * cstand.adb (Register_Float_Type): Add 'precision' parameter and use
    it to set the RM size.  Use directly 'size' for the Esize.
    * gcc-interface/gigi.h (enumerate_modes): Add integer parameter.
    * gcc-interface/misc.c (enumerate_modes): Likewise.  Do not register
    types for vector modes, pass the size in addition to the precision.

Modified:
    branches/gcc-4_7-branch/gcc/ada/ChangeLog
    branches/gcc-4_7-branch/gcc/ada/back_end.ads
    branches/gcc-4_7-branch/gcc/ada/cstand.adb
    branches/gcc-4_7-branch/gcc/ada/gcc-interface/gigi.h
    branches/gcc-4_7-branch/gcc/ada/gcc-interface/misc.c

[Bug ada/51483] [4.7/4.8/4.9 regression] cstand.adb:Register_Float_Type makes invalid assumption about FP modes

[ebotcazou at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=51483

Eric Botcazou <ebotcazou at gcc dot gnu.org> changed:

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

--- Comment #24 from Eric Botcazou <ebotcazou at gcc dot gnu.org> ---
Patch applied everywhere.

[Bug ada/51483] [4.7/4.8/4.9 regression] cstand.adb:Register_Float_Type makes invalid assumption about FP modes

[mikpelinux at gmail dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=51483

--- Comment #25 from Mikael Pettersson <mikpelinux at gmail dot com> ---
Thanks!