tcg: Do not recreate INDEX_op_neg_vec unless supported

Use tcg_can_emit_vec_op instead of just TCG_TARGET_HAS_neg_vec,
so that we check the type and vece for the actual operation.
Reviewed-by: NAlex Bennée <alex.bennee@linaro.org>
Signed-off-by: NRichard Henderson <richard.henderson@linaro.org>

tcg/optimize.c

@@ -734,9 +734,13 @@ void tcg_optimize(TCGContext *s)
                 } else if (opc == INDEX_op_sub_i64) {
                     neg_op = INDEX_op_neg_i64;
                     have_neg = TCG_TARGET_HAS_neg_i64;
-                } else {
+                } else if (TCG_TARGET_HAS_neg_vec) {
+                    TCGType type = TCGOP_VECL(op) + TCG_TYPE_V64;
+                    unsigned vece = TCGOP_VECE(op);
                     neg_op = INDEX_op_neg_vec;
-                    have_neg = TCG_TARGET_HAS_neg_vec;
+                    have_neg = tcg_can_emit_vec_op(neg_op, type, vece) > 0;
+                } else {
+                    break;
                 }
                 if (!have_neg) {
                     break;