[Bug middle-end/52578] New: Fails to fold another size difference

[Bug middle-end/52578] New: Fails to fold another size difference

[rguenth at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=52578

             Bug #: 52578
           Summary: Fails to fold another size difference
    Classification: Unclassified
           Product: gcc
           Version: 4.7.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: middle-end
        AssignedTo: unassigned@gcc.gnu.org
        ReportedBy: rguenth@gcc.gnu.org


gnat.dg/opt9.adb will fail with the bitfield handling patch with -m32 because
we do not fold

long bar (long i)
{
  return (long)((unsigned long)i + 2) - (long)i;
}
long foo (int i)
{
  return (long)((unsigned long)i + 2) - (long)i;
}

to constants.  the associate: path splits the above to
var0 == (long unsigned int) i, lit0 == 2, var1 == -i

which fails to associate because of


          /* With undefined overflow we can only associate constants with one
             variable, and constants whose association doesn't overflow.  */
          if ((POINTER_TYPE_P (type) && POINTER_TYPE_OVERFLOW_UNDEFINED)
              || (INTEGRAL_TYPE_P (type) && !TYPE_OVERFLOW_WRAPS (type)))
            {
              if (var0 && var1)
                {
                  tree tmp0 = var0;
                  tree tmp1 = var1;

                  if (TREE_CODE (tmp0) == NEGATE_EXPR)
                    tmp0 = TREE_OPERAND (tmp0, 0);
                  if (TREE_CODE (tmp1) == NEGATE_EXPR)
                    tmp1 = TREE_OPERAND (tmp1, 0);
                  /* The only case we can still associate with two variables
                     is if they are the same, modulo negation.  */
                  if (!operand_equal_p (tmp0, tmp1, 0))
                    ok = false;

but we can as well strip widening and sign-changing conversions I think.

[Bug middle-end/52578] Fails to fold another size difference

[rguenth at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=52578

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |ASSIGNED
   Last reconfirmed|                            |2012-03-13
         AssignedTo|unassigned at gcc dot       |rguenth at gcc dot gnu.org
                   |gnu.org                     |
     Ever Confirmed|0                           |1

--- Comment #1 from Richard Guenther <rguenth at gcc dot gnu.org> 2012-03-13 13:25:24 UTC ---
Fixing that we still do not fold foo (), but associate it to

  return ((long int) (long unsigned int) i - (long int) i) + 2;

[Bug middle-end/52578] Fails to fold another size difference

[rguenth at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=52578

--- Comment #2 from Richard Guenther <rguenth at gcc dot gnu.org> 2012-03-14 10:51:38 UTC ---
Author: rguenth
Date: Wed Mar 14 10:51:34 2012
New Revision: 185378

URL: http://gcc.gnu.org/viewcvs?root=gcc&view=rev&rev=185378
Log:
2012-03-14  Richard Guenther  <rguenther@suse.de>

    PR middle-end/52578
    * fold-const.c (fold_unary_loc): Fold (T1)(T2)x to (T1)x if
    the outermost conversion is a sign-change only.
    (fold_binary_loc): Disregard widening and sign-changing
    conversions when we determine if two variables are equal
    for reassociation.
    * tree-ssa-forwprop.c (combine_conversions): Fold (T1)(T2)x to
    (T1)x if the outermost conversion is a sign-change only.

    * gcc.dg/pr52578.c: New testcase.

Added:
    trunk/gcc/testsuite/gcc.dg/pr52578.c
Modified:
    trunk/gcc/ChangeLog
    trunk/gcc/fold-const.c
    trunk/gcc/testsuite/ChangeLog
    trunk/gcc/tree-ssa-forwprop.c

[Bug middle-end/52578] Fails to fold another size difference

[rguenth at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=52578

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|ASSIGNED                    |RESOLVED
         Resolution|                            |FIXED
   Target Milestone|---                         |4.8.0

--- Comment #3 from Richard Guenther <rguenth at gcc dot gnu.org> 2012-03-14 10:55:36 UTC ---
Fixed.