[Bug fortran/28276] New: EXPONENT() broken for real constants

[Bug fortran/28276] New: EXPONENT() broken for real constants

[anlauf at gmx dot de]

Hi *,

there is a nasty bug with EXPONENT():
EXPONENT(1.0) evaluates to 0 (which is wrong), while
real :: a=1.0; EXPONENT(a) evaluates to 1 (which is correct).

For more details and a further example see the attached
code sample.

Cheers,
-ha


-- 
           Summary: EXPONENT() broken for real constants
           Product: gcc
           Version: 4.2.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: fortran
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: anlauf at gmx dot de
  GCC host triplet: i686-pc-linux-gnu


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=28276

[Bug fortran/28276] EXPONENT() broken for real constants

[anlauf at gmx dot de]

------- Comment #1 from anlauf at gmx dot de  2006-07-05 20:01 -------
Created an attachment (id=11838)
 --> (http://gcc.gnu.org/bugzilla/attachment.cgi?id=11838&action=view)
Example code


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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=28276

[Bug fortran/28276] EXPONENT() broken for real constants

[kargl at gcc dot gnu dot org]

------- Comment #2 from kargl at gcc dot gnu dot org  2006-07-05 21:53 -------
Confirmed.

I have a patch, but it may depend on MPFR 2.2.0.


-- 

kargl at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
         AssignedTo|unassigned at gcc dot gnu   |kargl at gcc dot gnu dot org
                   |dot org                     |
             Status|UNCONFIRMED                 |ASSIGNED
     Ever Confirmed|0                           |1
   Last reconfirmed|0000-00-00 00:00:00         |2006-07-05 21:53:34
               date|                            |


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=28276

[Bug fortran/28276] EXPONENT() broken for real constants

[steven at gcc dot gnu dot org]

-- 

steven at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Keywords|                            |wrong-code
           Priority|P3                          |P1


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=28276

[Bug fortran/28276] EXPONENT() broken for real constants

[tobias dot burnus at physik dot fu-berlin dot de]

------- Comment #3 from tobias dot burnus at physik dot fu-berlin dot de  2006-07-17 17:54 -------
(CC myself)
I see the same problem for real(8) and for real(10) as for real = real(4),
except for
   print *, scale (fraction (a),   exponent (a))   / a
where I get "NaN" with real(10) instead of the correct "1.0", which one gets
for real and real(8).


-- 

tobias dot burnus at physik dot fu-berlin dot de changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |tobias dot burnus at physik
                   |                            |dot fu-berlin dot de


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=28276

[Bug fortran/28276] EXPONENT() broken for real constants

[sgk at troutmask dot apl dot washington dot edu]

------- Comment #4 from sgk at troutmask dot apl dot washington dot edu  2006-07-17 18:11 -------
Subject: Re:  EXPONENT() broken for real constants

On Mon, Jul 17, 2006 at 05:54:46PM -0000, tobias dot burnus at physik dot
fu-berlin dot de wrote:
> 
> I see the same problem for real(8) and for real(10) as for real = real(4),
> except for
>    print *, scale (fraction (a),   exponent (a))   / a
> where I get "NaN" with real(10) instead of the correct "1.0", which one gets
> for real and real(8).
> 

Can you try this patch?  It required MPFR 2.2.0.


Index: gcc4x/gcc/fortran/simplify.c
===================================================================
--- gcc4x/gcc/fortran/simplify.c        (revision 115505)
+++ gcc4x/gcc/fortran/simplify.c        (working copy)
@@ -1049,12 +1049,10 @@ gfc_simplify_exp (gfc_expr * x)
   return range_check (result, "EXP");
 }

-/* FIXME:  MPFR should be able to do this better */
 gfc_expr *
 gfc_simplify_exponent (gfc_expr * x)
 {
   int i;
-  mpfr_t tmp;
   gfc_expr *result;

   if (x->expr_type != EXPR_CONSTANT)
@@ -1071,20 +1069,9 @@ gfc_simplify_exponent (gfc_expr * x)
       return result;
     }

-  mpfr_init (tmp);
-
-  mpfr_abs (tmp, x->value.real, GFC_RND_MODE);
-  mpfr_log2 (tmp, tmp, GFC_RND_MODE);
-
-  gfc_mpfr_to_mpz (result->value.integer, tmp);
-
-  /* The model number for tiny(x) is b**(emin - 1) where b is the base and
emin
-     is the smallest exponent value.  So, we need to add 1 if x is tiny(x). 
*/
-  i = gfc_validate_kind (x->ts.type, x->ts.kind, false);
-  if (mpfr_cmp (x->value.real, gfc_real_kinds[i].tiny) == 0)
-    mpz_add_ui (result->value.integer,result->value.integer, 1);
-
-  mpfr_clear (tmp);
+  /* Requires MPFR 2.2.0 or newer.  */
+  i = (int) mpfr_get_exp (x->value.real);
+  mpz_set_si (result->value.integer, i);

   return range_check (result, "EXPONENT");
 }


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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=28276

[Bug fortran/28276] EXPONENT() broken for real constants

[tobias dot burnus at physik dot fu-berlin dot de]

------- Comment #5 from tobias dot burnus at physik dot fu-berlin dot de  2006-09-10 22:43 -------
> Can you try this patch?  It required MPFR 2.2.0.
Tested on openSUSE/AMD64 with current gfortran trunk + patch and mpfr-2.2.0-9.

It works ok with kind = 4 and kind = 8. However, with kind = 10 I get a NaN for
  print *, scale (fraction (a),   exponent (a))   / a

My test case:
----------------
integer, parameter :: k = 10
real(k), parameter :: one = 1.0_k
real(k) :: a
a = one
print *, "This ratio should be 1:"
print *, scale (fraction (a),   exponent (a))   / a
end


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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=28276

[Bug fortran/28276] EXPONENT() broken for real constants

[sgk at troutmask dot apl dot washington dot edu]

------- Comment #6 from sgk at troutmask dot apl dot washington dot edu  2006-09-11 19:19 -------
Subject: Re:  EXPONENT() broken for real constants

On Sun, Sep 10, 2006 at 10:43:21PM -0000, tobias dot burnus at physik dot
fu-berlin dot de wrote:
> 
> Comment #5 from tobias dot burnus at physik dot fu-berlin dot de  2006-09-10 22:43 -------
> > Can you try this patch?  It required MPFR 2.2.0.
> Tested on openSUSE/AMD64 with current gfortran trunk + patch and mpfr-2.2.0-9.
> 
> It works ok with kind = 4 and kind = 8. However, with kind = 10 I get a
> NaN for
>   print *, scale (fraction (a),   exponent (a))   / a
> 
> My test case:
> ----------------
> integer, parameter :: k = 10
> real(k), parameter :: one = 1.0_k
> real(k) :: a
> a = one
> print *, "This ratio should be 1:"
> print *, scale (fraction (a),   exponent (a))   / a
> end
> 
> 

gfortran is calling the wrong libm function.  -fdump-tree-original 
on FreeBSD shows

{
  real10 D.1254;

  D.1254 = scalbn(_gfortran_fraction_r10(a10),_gfortran_exponent_r10(a10))/a10;
  _gfortran_transfer_real (&dt_parm.2, &D.1254, 10);
}

That should be scalbnl().  I'll see if I can track down the bug.


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=28276

[Bug fortran/28276] EXPONENT() broken for real constants

[sgk at troutmask dot apl dot washington dot edu]

------- Comment #7 from sgk at troutmask dot apl dot washington dot edu  2006-09-11 19:33 -------
Subject: Re:  EXPONENT() broken for real constants

On Mon, Sep 11, 2006 at 07:19:41PM -0000, sgk at troutmask dot apl dot
washington dot edu wrote:
> 
> gfortran is calling the wrong libm function.  -fdump-tree-original 
> on FreeBSD shows
> 
> {
>   real10 D.1254;
> 
>   D.1254 = scalbn(_gfortran_fraction_r10(a10),_gfortran_exponent_r10(a10))/a10;
>   _gfortran_transfer_real (&dt_parm.2, &D.1254, 10);
> }
> 
> That should be scalbnl().  I'll see if I can track down the bug.
> 

I should also note that the parsing is correct as shown by -fdump-parse-tree


ASSIGN MAIN__:a10 1.00000000000000000000_10
ASSIGN MAIN__:a10 (/ __scale_10[[((__fraction_10[[((MAIN__:a10))]])
(__exponent_10[[((MAIN__:a10))]]))]] MAIN__:a10)

So it's the translation of __scale_10 to scalbnl.


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=28276

[Bug fortran/28276] EXPONENT() broken for real constants

[sgk at troutmask dot apl dot washington dot edu]

------- Comment #8 from sgk at troutmask dot apl dot washington dot edu  2006-09-11 20:31 -------
Subject: Re:  EXPONENT() broken for real constants

On Mon, Sep 11, 2006 at 07:33:35PM -0000, sgk at troutmask dot apl dot
washington dot edu wrote:
> 
> I should also note that the parsing is correct as shown by -fdump-parse-tree
> 
> 
> ASSIGN MAIN__:a10 1.00000000000000000000_10
> ASSIGN MAIN__:a10 (/ __scale_10[[((__fraction_10[[((MAIN__:a10))]])
> (__exponent_10[[((MAIN__:a10))]]))]] MAIN__:a10)
> 
> So it's the translation of __scale_10 to scalbnl.
> 

I have a patch for this problem.


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=28276

[Bug fortran/28276] EXPONENT() broken for real constants

[kargl at gcc dot gnu dot org]

------- Comment #9 from kargl at gcc dot gnu dot org  2006-09-27 20:15 -------
Subject: Bug 28276

Author: kargl
Date: Wed Sep 27 20:15:22 2006
New Revision: 117257

URL: http://gcc.gnu.org/viewcvs?root=gcc&view=rev&rev=117257
Log:
        * configure.in: Check for GMP 4.1 or newer.  Check for MPFR 2.2.0 
        or newer.
        * configure: Regenerated.
        * doc/install.texi: Document required versions of GMP and MPFR.
        * fortran/arith.c: Conditionally include arctangent2().
        (gfc_check_real_range): Use mpfr_subnormalize in preference to local
        hack.
        * fortran/trans-intrinsic.c (gfc_get_intrinsic_lib_fndecl): Append
        l for long double functions.
        * fortran/simplify.c: Wrap Copyright to new line.
        (gfc_simplify_atan2): Use mpfr_atan2 in preference to arctangent2().
        (gfc_simplify_log): Ditto.


        PR fortran/28276
        * fortran/simplify.c (gfc_simplify_exponent): Use mpfr_get_exp in
        preference to broken local hack.

        PR fortran/27021
        * fortran/simplify.c (gfc_simplify_nearest): Use mpfr_nexttoward and
        mpfr_subnormalize to handle numbers near zero in preference to broken
         local hack.

        PR fortran/28276
        * testsuite/gfortran.dg/exponent_1.f90: New test.

        PR fortran/27021
        * testsuite/gfortran.dg/nearest_1.f90: New test.


Added:
    trunk/gcc/testsuite/gfortran.dg/exponent_1.f90
    trunk/gcc/testsuite/gfortran.dg/nearest_1.f90
Modified:
    trunk/ChangeLog
    trunk/configure
    trunk/configure.in
    trunk/gcc/ChangeLog
    trunk/gcc/doc/install.texi
    trunk/gcc/fortran/ChangeLog
    trunk/gcc/fortran/arith.c
    trunk/gcc/fortran/simplify.c
    trunk/gcc/fortran/trans-intrinsic.c
    trunk/gcc/testsuite/ChangeLog


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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=28276

[Bug fortran/28276] EXPONENT() broken for real constants

[kargl at gcc dot gnu dot org]

------- Comment #10 from kargl at gcc dot gnu dot org  2006-09-27 20:38 -------
Fixed on trunk.  Won't be fixed on 4.1.


-- 

kargl at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|ASSIGNED                    |RESOLVED
         Resolution|                            |FIXED
   Target Milestone|---                         |4.2.0


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=28276