[Bug other/29534] [4.1 Regression] ICE in "gcc -O -ftrapv" with decreasing array index

[rguenth at gcc dot gnu dot org]

------- Comment #1 from rguenth at gcc dot gnu dot org  2006-10-21 12:12 -------
Confirmed.  Works with 4.2.

We endlessly fold

#5  0x08206aa1 in fold_unary (code=NEGATE_EXPR, type=0xb7c5c284,
    op0=0xb7cd3258) at /home/richard/src/gcc-4_1-branch/gcc/fold-const.c:6876
#6  0x08212e3e in fold_build1_stat (code=NEGATE_EXPR, type=0xb7c5c284,
    op0=0xb7cd3258) at /home/richard/src/gcc-4_1-branch/gcc/fold-const.c:10475
#7  0x081f8a05 in negate_expr (t=0xb7cd3258)
    at /home/richard/src/gcc-4_1-branch/gcc/fold-const.c:1167
#8  0x08206aa1 in fold_unary (code=NEGATE_EXPR, type=0xb7c5c284,
    op0=0xb7cd3258) at /home/richard/src/gcc-4_1-branch/gcc/fold-const.c:6876
#9  0x08212e3e in fold_build1_stat (code=NEGATE_EXPR, type=0xb7c5c284,
    op0=0xb7cd3258) at /home/richard/src/gcc-4_1-branch/gcc/fold-const.c:10475
#10 0x081f8a05 in negate_expr (t=0xb7cd3258)
...
#28 0x081f8a05 in negate_expr (t=0xb7cd3258)
    at /home/richard/src/gcc-4_1-branch/gcc/fold-const.c:1167
1167                  tree temp = fold_convert (ntype, TREE_OPERAND (t, 0));
(gdb) call debug_generic_expr (t)
-07fffffff

which has overflowed.

#29 0x08206aa1 in fold_unary (code=NEGATE_EXPR, type=0xb7c5c284,
    op0=0xb7cd3258) at /home/richard/src/gcc-4_1-branch/gcc/fold-const.c:6876
#30 0x08212e3e in fold_build1_stat (code=NEGATE_EXPR, type=0xb7c5c284,
    op0=0xb7cd3258) at /home/richard/src/gcc-4_1-branch/gcc/fold-const.c:10475
#31 0x081f8a05 in negate_expr (t=0xb7cd3258)
    at /home/richard/src/gcc-4_1-branch/gcc/fold-const.c:1167
#32 0x0820cb87 in fold_binary (code=CEIL_DIV_EXPR, type=0xb7c5c284,
    op0=0xb7cd3258, op1=0xb7c4da50)
    at /home/richard/src/gcc-4_1-branch/gcc/fold-const.c:8420
#33 0x08212e8e in fold_build2_stat (code=CEIL_DIV_EXPR, type=0xb7c5c284,
    op0=0xb7cd3258, op1=0xb7c4da50)
    at /home/richard/src/gcc-4_1-branch/gcc/fold-const.c:10521
#34 0x080fe243 in infer_loop_bounds_from_undefined (loop=0x86a5310)

#32 0x0820cb87 in fold_binary (code=CEIL_DIV_EXPR, type=0xb7c5c284,
    op0=0xb7cd3258, op1=0xb7c4da50)
    at /home/richard/src/gcc-4_1-branch/gcc/fold-const.c:8420
8420        case ROUND_DIV_EXPR:
(gdb) call debug_generic_expr (op0)
-07fffffff
(gdb) call debug_generic_expr (op1)
-1


-- 

rguenth at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |rguenth at gcc dot gnu dot
                   |                            |org, rakdver at gcc dot gnu
                   |                            |dot org
             Status|UNCONFIRMED                 |NEW
     Ever Confirmed|0                           |1
           Keywords|                            |ice-on-valid-code
      Known to fail|                            |4.1.2
      Known to work|                            |4.0.3 4.2.0
   Last reconfirmed|0000-00-00 00:00:00         |2006-10-21 12:12:55
               date|                            |
            Summary|ICE in "gcc -O -ftrapv" with|[4.1 Regression] ICE in "gcc
                   |decreasing array index      |-O -ftrapv" with decreasing
                   |                            |array index


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=29534