https://gcc.gnu.org/bugzilla/show_bug.cgi?id=81196
Richard Biener <rguenth at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Status|UNCONFIRMED |NEW
Last reconfirmed| |2017-06-26
CC| |amker at gcc dot gnu.org,
| |rguenth at gcc dot gnu.org
Ever confirmed|0 |1
--- Comment #1 from Richard Biener <rguenth at gcc dot gnu.org> ---
Probably some more elaborate handling in number_of_iterations_cond is required:
/* We can handle the case when neither of the sides of the comparison is
invariant, provided that the test is NE_EXPR. This rarely occurs in
practice, but it is simple enough to manage. */
if (!integer_zerop (iv0->step) && !integer_zerop (iv1->step))
{
tree step_type = POINTER_TYPE_P (type) ? sizetype : type;
if (code != NE_EXPR)
return false;
iv0->step = fold_binary_to_constant (MINUS_EXPR, step_type,
iv0->step, iv1->step);
iv0->no_overflow = false;
iv1->step = build_int_cst (step_type, 0);
iv1->no_overflow = true;
}
I think this exit is premature and the following works for the testcase.
I suppose exiting is still required but can be moved to a later point,
or the helpers now fully handle the case of non-constant iv1 ...
Vectorization still fails with this due to runtime aliasing so it
probably exposes some wrong-code issue. CCing Bin who is now most
familiar with the niter code.
Index: gcc/tree-ssa-loop-niter.c
===================================================================
--- gcc/tree-ssa-loop-niter.c (revision 249638)
+++ gcc/tree-ssa-loop-niter.c (working copy)
@@ -1674,14 +1674,14 @@ number_of_iterations_cond (struct loop *
if (!integer_zerop (iv0->step) && !integer_zerop (iv1->step))
{
tree step_type = POINTER_TYPE_P (type) ? sizetype : type;
- if (code != NE_EXPR)
- return false;
-
- iv0->step = fold_binary_to_constant (MINUS_EXPR, step_type,
- iv0->step, iv1->step);
- iv0->no_overflow = false;
- iv1->step = build_int_cst (step_type, 0);
- iv1->no_overflow = true;
+ if (code == NE_EXPR)
+ {
+ iv0->step = fold_binary_to_constant (MINUS_EXPR, step_type,
+ iv0->step, iv1->step);
+ iv0->no_overflow = false;
+ iv1->step = build_int_cst (step_type, 0);
+ iv1->no_overflow = true;
+ }
}
/* If the result of the comparison is a constant, the loop is weird. More
