===================================================================
@@ -2265,9 +2265,12 @@ simplify_vector_constructor (gimple_stmt
sel.quick_push (elts[i].second + elts[i].first * refnelts);
/* And fill the tail with "something". It's really don't care,
and ideally we'd allow VEC_PERM to have a smaller destination
- vector. */
+ vector. As heuristic try to preserve a uniform orig[0] which
+ facilitates later pattern-matching VEC_PERM_EXPR to a
+ BIT_INSERT_EXPR. */
for (; i < refnelts; ++i)
- sel.quick_push (i - elts.length ());
+ sel.quick_push ((elts[0].second == 0 && elts[0].first == 0
+ ? 0 : refnelts) + i);
vec_perm_indices indices (sel, orig[1] ? 2 : 1, refnelts);
if (!can_vec_perm_const_p (TYPE_MODE (perm_type), indices))
return false;
===================================================================
@@ -6049,7 +6049,7 @@ (define_operator_list COND_TERNARY
break;
if (at < encoded_nelts && sel.series_p (at + 1, 1, at + 1, 1))
{
- if (known_lt (at, nelts))
+ if (known_lt (poly_uint64 (sel[at]), nelts))
ins = fold_read_from_vector (cop0, sel[at]);
else
ins = fold_read_from_vector (cop1, sel[at] - nelts);
===================================================================
@@ -0,0 +1,14 @@
+/* { dg-do compile } */
+/* { dg-options "-O -mavx2 -fdump-tree-forwprop1" } */
+
+typedef double v4df __attribute__((vector_size (32)));
+typedef double v2df __attribute__((vector_size (16)));
+
+v2df
+bar (v4df x, double *p)
+{
+ return (v2df) { x[0], *p };
+}
+
+/* { dg-final { scan-tree-dump "BIT_INSERT_EXPR" "forwprop1" } } */
+/* { dg-final { scan-assembler "movhpd" } } */