[Bug target/115936] [15 Regression] GCN vs. ivopts: replace constant_multiple_of with aff_combination_constant_multiple_p [PR114932]

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

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=115936

--- Comment #6 from Tamar Christina <tnfchris at gcc dot gnu.org> ---
(In reply to Richard Biener from comment #3)
> iv->step should never be a pointer type

This is created by SCEV.

simple_iv_with_niters in the case where no CHREC is found creates an IV with
base == ev, offset == 0;

however in this case EV is a POINTER_PLUS_EXPR and so the type is a pointer.
it ends up creating an unusable expression.

following the remaining code, it looks like this should be

diff --git a/gcc/tree-scalar-evolution.cc b/gcc/tree-scalar-evolution.cc
index 5aa95a2497a..abb2bad7773 100644
--- a/gcc/tree-scalar-evolution.cc
+++ b/gcc/tree-scalar-evolution.cc
@@ -3243,7 +3243,11 @@ simple_iv_with_niters (class loop *wrto_loop, class loop
*use_loop,
   if (tree_does_not_contain_chrecs (ev))
     {
       iv->base = ev;
-      iv->step = build_int_cst (TREE_TYPE (ev), 0);
+      tree ev_type = TREE_TYPE (ev);
+      if (POINTER_TYPE_P (ev_type))
+       ev_type = sizetype;
+
+      iv->step = build_int_cst (ev_type, 0);
       iv->no_overflow = true;
       return true;
     }

So I think there are two bugs here.  I also think the IVopts one is a bug, as
it's clearly changing the type and introducing a mismatch there too.

I'm regression testing both changes.