[Bug fortran/40019] New: LEADZ and TRAILZ give wrong results

["fxcoudert at gcc dot gnu dot org" <gcc-bugzilla@gcc.gnu.org>]

LEADZ and TRAILZ can give wrong results for kinds other than 4 and 8. For
example, the following code:

  integer(kind=1) :: i1
  integer(kind=2) :: i2
  integer(kind=4) :: i4
  integer(kind=8) :: i8
  integer(kind=16) :: i16

  i1 = -1
  i2 = -1
  i4 = -1
  i8 = -1
  i16 = -1
  print *, leadz(i1), leadz(i2), leadz(i4), leadz(i8), leadz(i16)

gives "        -24         -16           0           0          64" as results,
while it should only yield zeros!

There are a few reasons:

  - for kinds 1 and 2, we should not cast directly to (unsigned int), but do a
double cast: (unsigned int)(unsigned char) for kind=1, for example; otherwise,
negative values are screwed.

  - trans-intrinsic.c uses a correspondance, kinds == 1, 2 and 4 use
BUILT_IN_CLZ, kind 8 uses BUILT_IN_CLZL and kind 16 uses BUILT_IN_CLZLL; in
reality, there is no such correspondance, as kind==16 is larger than long long!


This, of course, makes it harder, because there is no function ready for use in
kind==16.


-- 
           Summary: LEADZ and TRAILZ give wrong results
           Product: gcc
           Version: 4.5.0
            Status: UNCONFIRMED
          Keywords: wrong-code
          Severity: normal
          Priority: P3
         Component: fortran
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: fxcoudert at gcc dot gnu dot org


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=40019