[Bug c/46041] New: __FP_FAST_FMA not defined with -E

[Bug c/46041] New: __FP_FAST_FMA not defined with -E

[rth at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=46041

           Summary: __FP_FAST_FMA not defined with -E
           Product: gcc
           Version: 4.6.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c
        AssignedTo: unassigned@gcc.gnu.org
        ReportedBy: rth@gcc.gnu.org


The test

  optab_handler (fma_optab, mode) != CODE_FOR_nothing

always fails with -E because we never proceed that far.  See

do_compile:
      /* Language-dependent initialization.  Returns true on success.  */
      if (lang_dependent_init (main_input_filename))
        compile_file ();

c_common_init:
  if (flag_preprocess_only)
    {
      finish_options ();
      preprocess_file (parse_in);
      return false;
    }

[Bug c/46041] __FP_FAST_FMA not defined with -E

[pinskia at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=46041

--- Comment #1 from Andrew Pinski <pinskia at gcc dot gnu.org> 2010-10-15 22:59:10 UTC ---
Doesn't that mean -save-temps is also broken?

[Bug c/46041] __FP_FAST_FMA not defined with -E

[rth at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=46041

--- Comment #2 from Richard Henderson <rth at gcc dot gnu.org> 2010-10-15 23:01:19 UTC ---
I think the easiest solution is to simply do

  switch (mode)
    {
    case SFmode:
#ifdef HAVE_fmasf4
      return HAVE_fmasf4;
#endif
      break;
    ...
    }
  return false;

instead of the optab_handler lookup.

[Bug c/46041] __FP_FAST_FMA not defined with -E

[rth at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=46041

--- Comment #3 from Richard Henderson <rth at gcc dot gnu.org> 2010-10-15 23:02:26 UTC ---
(In reply to comment #1)
> Doesn't that mean -save-temps is also broken?

Yes.

[Bug c/46041] __FP_FAST_FMA not defined with -E

[rguenth at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=46041

--- Comment #4 from Richard Guenther <rguenth at gcc dot gnu.org> 2010-10-16 09:43:25 UTC ---
Hm, the question is if it is a good idea anyway given the target and
optimization
attributes.

[Bug c/46041] __FP_FAST_FMA not defined with -E

[meissner at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=46041

Michael Meissner <meissner at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |ASSIGNED
   Last reconfirmed|                            |2010.10.18 15:11:54
     Ever Confirmed|0                           |1

[Bug c/46041] __FP_FAST_FMA not defined with -E

[meissner at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=46041

Michael Meissner <meissner at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
   Last reconfirmed|2010-10-18 15:11:54         |
         AssignedTo|unassigned at gcc dot       |meissner at gcc dot gnu.org
                   |gnu.org                     |

--- Comment #5 from Michael Meissner <meissner at gcc dot gnu.org> 2010-10-18 15:26:13 UTC ---
Yes, -save-temps would be broken.  I noticed this after submitting the bug when
I tried to patch glibc's math.h and I happened to use -save-temps, and it
didn't seem to work, and I was just about to investigate it when I needed to go
home.

The suggestion to use HAVE_fma<mode>4 instead of the check on the builtin array
will probably work for normal -save-temps.  However, for target specific
functions, we may need to go to using a conditional macro for these.

However, Richard Guenther has a point, that it really doesn't work too well
when you consider target specific attributes.  Frankly, I hadn't thought about
-save-temps when I first contemplated target attributes in the first place
(even though I originally added -save-temps many years ago).  The -save-temps
switch doesn't work in general when functions have different target attributes
that will change the macros being defined.  I would imagine -E would have the
same problem.  The only way I can see to do this 'right' is to move -save-temps
into the cpp handling in the compiler proper, rather than doing two passes like
we do now. In the old days, we had to do two passes, because cpp was a separate
process.

While this might fix -save-temps, I'm still not sure what we can do about -E.

[Bug c/46041] __FP_FAST_FMA not defined with -E

[rth at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=46041

--- Comment #6 from Richard Henderson <rth at gcc dot gnu.org> 2010-10-18 16:12:21 UTC ---
Does anyone honestly expect a pre-processor macro to change due to
attributes on a function?  I sure don't -- that would seem to be a
clear translation phase ordering violation.

Setting __FP_FAST_FMA based on the command-line compiler options
only would seem to be to be Good Enough.

[Bug c/46041] __FP_FAST_FMA not defined with -E

[meissner at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=46041

--- Comment #7 from Michael Meissner <meissner at gcc dot gnu.org> 2010-10-18 16:21:31 UTC ---
Yes, though the issue originally came up in terms of the pragma and not the
attribute, because people wanted to include the various include files that had
#ifdef's to guard against builtin functions if the target switches weren't
used.

[Bug c/46041] __FP_FAST_FMA not defined with -E

[meissner at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=46041

--- Comment #8 from Michael Meissner <meissner at gcc dot gnu.org> 2010-10-18 20:01:24 UTC ---
Created attachment 22083
  --> http://gcc.gnu.org/bugzilla/attachment.cgi?id=22083
Patch that redefines mode_has_fma so that it works with -save-temps

[Bug c/46041] __FP_FAST_FMA not defined with -E

[meissner at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=46041

--- Comment #9 from Michael Meissner <meissner at gcc dot gnu.org> 2010-10-18 22:37:36 UTC ---
Author: meissner
Date: Mon Oct 18 22:37:32 2010
New Revision: 165666

URL: http://gcc.gnu.org/viewcvs?root=gcc&view=rev&rev=165666
Log:
Fix PR 46041

Modified:
    trunk/gcc/ChangeLog
    trunk/gcc/builtins.c
    trunk/gcc/c-family/ChangeLog
    trunk/gcc/c-family/c-cppbuiltin.c
    trunk/gcc/tree.h

[Bug c/46041] __FP_FAST_FMA not defined with -E

[meissner at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=46041

Michael Meissner <meissner at gcc dot gnu.org> changed:

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

--- Comment #10 from Michael Meissner <meissner at gcc dot gnu.org> 2011-12-09 18:34:15 UTC ---
Fixed on October 18th, 2010.