When testcases (such as libgomp.c-c++-common/for-11.c) use unsigned types for
loop counters then the vectorizer will also use unsigned types for the offsets
passed to gather/scatter instructions. This is a problem if the loop step is
negative and the offset type is narrower than a pointer.
This commit ensures that negative offsets are labelled as signed.
gcc/ChangeLog:
PR target/121393
* tree-vect-stmts.cc (vect_get_strided_load_store_ops): Use signed
offsets for negative steps.
---
This fixes a problem observed on amdgcn, but there doesn't seem to be
anything about it that is target-specific.
OK for mainline?
Andrew
gcc/tree-vect-stmts.cc | 8 ++++++++
1 file changed, 8 insertions(+)
diff --git a/gcc/tree-vect-stmts.cc b/gcc/tree-vect-stmts.cc
index cfc4f323a22..254fe6e6c0f 100644
--- a/gcc/tree-vect-stmts.cc
+++ b/gcc/tree-vect-stmts.cc
@@ -2969,6 +2969,14 @@ vect_get_strided_load_store_ops (stmt_vec_info
stmt_info, slp_tree node,
type of the vector instead. */
tree offset_type = TREE_TYPE (offset_vectype);
+ if (TREE_CODE (DR_STEP (dr)) == INTEGER_CST
+ && compare_step_with_zero (loop_vinfo, stmt_info) < 0
+ && TYPE_SIGN (offset_type) == UNSIGNED)
+ {
+ offset_type = signed_type_for (offset_type);
+ offset_vectype = signed_type_for (offset_vectype);
+ }
+
/* Calculate X = DR_STEP / SCALE and convert it to the appropriate type. */
tree step = size_binop (EXACT_DIV_EXPR, unshare_expr (DR_STEP (dr)),
ssize_int (SLP_TREE_GS_SCALE (node)));
--
2.51.0
