[Bug fortran/37635] New: Fortran 2008: Support LEADZ / TRAILZ

[Bug fortran/37635] New: Fortran 2008: Support LEADZ / TRAILZ

[burnus at gcc dot gnu dot org]

Requested by Richard Townsend at
http://groups.google.com/group/comp.lang.fortran/browse_thread/thread/1e4130b9720e4f2a

LEADZ and TRAILZ are rather common vendor extensions, e.g. supported by the
Intel compiler (it also allows for logical arguments).

LEADZ (I)
  Description. Number of leading zero bits.
  Argument. I shall be of type integer.
  Result Value. If all of the bits of I are zero, the result value is
                BIT SIZE (I). [...]

TRAILZ (I)
  Description. Number of trailing zero bits.
  Argument. I shall be of type integer.


The implementation should be relatively easy using the following built-ins,
however, one presumably needs a special case for ZERO.

 BUILT_IN_CLZ*
 "These functions return the number of leading 0-bits in a, starting
  at the most significant bit position. If a is zero, the result
  is undefined."
and
 BUILT_IN_CTZ*
 "These functions return the number of trailing 0-bits in a, starting at the 
  least significant bit position. If a is zero, the result is undefined."
(Description copied from
http://gcc.gnu.org/onlinedocs/gccint/Integer-library-routines.html)

For compile-time simplification, MPFR does not seem to provide a ready-to-use
function; if one cooks up something oneself, one needs to check endian issues
(though there might be none).


-- 
           Summary: Fortran 2008: Support LEADZ / TRAILZ
           Product: gcc
           Version: 4.4.0
            Status: UNCONFIRMED
          Severity: enhancement
          Priority: P3
         Component: fortran
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: burnus at gcc dot gnu dot org


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=37635

[Bug fortran/37635] Fortran 2008: Support LEADZ / TRAILZ

[kargl at gcc dot gnu dot org]

------- Comment #1 from kargl at gcc dot gnu dot org  2008-09-24 16:19 -------
(In reply to comment #0)

> For compile-time simplification, MPFR does not seem to provide a ready-to-use
> function; if one cooks up something oneself, one needs to check endian issues
> (though there might be none).

I think you mean GMP because we're concerned with INTEGER types.
See mpz_scan0 and mpz_scan1.


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=37635

[Bug fortran/37635] Fortran 2008: Support LEADZ / TRAILZ

[steven at gcc dot gnu dot org]

------- Comment #2 from steven at gcc dot gnu dot org  2008-09-24 22:28 -------
I'll see this weekend if I can take care of this.


-- 

steven at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
         AssignedTo|unassigned at gcc dot gnu   |steven at gcc dot gnu dot
                   |dot org                     |org
             Status|UNCONFIRMED                 |ASSIGNED
     Ever Confirmed|0                           |1
   Last reconfirmed|0000-00-00 00:00:00         |2008-09-24 22:28:12
               date|                            |


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=37635

[Bug fortran/37635] Fortran 2008: Support LEADZ / TRAILZ

[steven at gcc dot gnu dot org]

------- Comment #3 from steven at gcc dot gnu dot org  2008-09-27 14:09 -------
Created an attachment (id=16414)
 --> (http://gcc.gnu.org/bugzilla/attachment.cgi?id=16414&action=view)
draft patch


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=37635

[Bug fortran/37635] Fortran 2008: Support LEADZ / TRAILZ

[burnus at gcc dot gnu dot org]

------- Comment #4 from burnus at gcc dot gnu dot org  2008-09-28 18:03 -------
Posted patch:
http://gcc.gnu.org/ml/fortran/2008-09/msg00443.html

Approved, but check in will probably deferred until 4.5 opens.


-- 

burnus at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Keywords|                            |patch


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=37635

[Bug fortran/37635] Fortran 2008: Support LEADZ / TRAILZ

[steven at gcc dot gnu dot org]

------- Comment #6 from steven at gcc dot gnu dot org  2008-10-02 18:52 -------
Subject: Bug 37635

Author: steven
Date: Thu Oct  2 18:51:12 2008
New Revision: 140837

URL: http://gcc.gnu.org/viewcvs?root=gcc&view=rev&rev=140837
Log:
testsuite
        * gfortran.fortran-torture/execute/intrinsic_leadz.f90: New test.
        * gfortran.fortran-torture/execute/intrinsic_trailz.f90: New test.

fortran/
        PR fortran/37635
        * intrinsic.c (add_functions): Add LEADZ and TRAILZ as generics.
        * intrinsic.h (gfc_simplify_leadz, gfc_simplify_trailz): New protos.
        * gfortran.h <enum gfc_isym_id>: (GFC_ISYM_LEADZ, GFC_ISYM_TRAILZ):
New.
        * f95-lang (gfc_init_builtin_functions): Add BUILT_IN_CLZ,
        BUILT_IN_CLZL, BUILT_IN_CLZLL, BUILT_IN_CTZ, BUILT_IN_CTZL, and
        BUILT_IN_CTZLL.
        * trans-intrinsic.c (gfc_conv_intrinsic_leadz,
        gfc_conv_intrinsic_trails): New code-generation functions for LEADZ
        and TRAILZ intrinsics.
        (gfc_conv_intrinsic_function): Use them
        * intrinsic.texi: Add documentation for LEADZ and TRAILZ.
        * simplify.c (gfc_simplify_leadz, gfc_simplify_trailz): New functions.

Added:
    trunk/gcc/testsuite/gfortran.fortran-torture/execute/intrinsic_leadz.f90
    trunk/gcc/testsuite/gfortran.fortran-torture/execute/intrinsic_trailz.f90
Modified:
    trunk/gcc/fortran/ChangeLog
    trunk/gcc/fortran/f95-lang.c
    trunk/gcc/fortran/gfortran.h
    trunk/gcc/fortran/intrinsic.c
    trunk/gcc/fortran/intrinsic.h
    trunk/gcc/fortran/intrinsic.texi
    trunk/gcc/fortran/simplify.c
    trunk/gcc/fortran/trans-intrinsic.c
    trunk/gcc/testsuite/ChangeLog


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=37635

[Bug fortran/37635] Fortran 2008: Support LEADZ / TRAILZ

[steven at gcc dot gnu dot org]

------- Comment #5 from steven at gcc dot gnu dot org  2008-10-02 18:52 -------
.


-- 

steven at gcc dot gnu dot org changed:

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


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=37635