http://gcc.gnu.org/bugzilla/show_bug.cgi?id=55022
Richard Biener <rguenth at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Status|NEW |ASSIGNED
Assignee|unassigned at gcc dot gnu.org |rguenth at gcc dot
gnu.org
--- Comment #18 from Richard Biener <rguenth at gcc dot gnu.org> ---
(In reply to Mircea Namolaru from comment #17)
> Vladimir Kargov, Tobias Grosser and me found that the problem is caused by
> incorrect folding of the floord operator. As a result Cloog translates the
> expression
> -4294967296*floord(_19-i_17,4294967296)
> to the tree-SSA expression
> 4294967296*floord(_19-i_17,-4294967296)
>
> This is wrong, in the first case floord is 0 and in the second is -1.
Not sure where that "folding" happens or what "floord" is, but if you
are refering to negate_expr () negating a /[fl] CST as a /[fl] -CST
then yes, that looks suspicious. OTOH the division variant tree codes
don't appear in the IL very often so it's hard to notice these mistakes.
Testing
Index: gcc/fold-const.c
===================================================================
*** gcc/fold-const.c (revision 209292)
--- gcc/fold-const.c (working copy)
*************** negate_expr_p (tree t)
*** 484,491 ****
case TRUNC_DIV_EXPR:
case ROUND_DIV_EXPR:
- case FLOOR_DIV_EXPR:
- case CEIL_DIV_EXPR:
case EXACT_DIV_EXPR:
/* In general we can't negate A / B, because if A is INT_MIN and
B is 1, we may turn this into INT_MIN / -1 which is undefined
--- 484,489 ----
*************** fold_negate_expr (location_t loc, tree t
*** 682,689 ****
case TRUNC_DIV_EXPR:
case ROUND_DIV_EXPR:
- case FLOOR_DIV_EXPR:
- case CEIL_DIV_EXPR:
case EXACT_DIV_EXPR:
/* In general we can't negate A / B, because if A is INT_MIN and
B is 1, we may turn this into INT_MIN / -1 which is undefined
--- 680,685 ----
