[PATCH] Fix latent issue in call vectorization

When the first argument of a call happens to be a SLP permute node
vect_is_simple_use will assign error_mark_node to the scalar op
(because there's no representative).  This causes subsequent argument
processing to ICE because rhs_type ends up as error_mark_node as well.

Fix this by getting the scalar argument type from the representative
call stmt instead (the scalar 'op' result of vect_is_simple_use is
legacy).

The testcase runs into this with the SLP subgraph merging patch,
reduced from SPEC CPU 2017.

Bootstrapped and tested on x86_64-unknown-linux-gnu, pushed.

	* tree-vect-stmts.cc (vectorizable_call): Get scalar argument
	type from the representative call stmt.

	* gcc.dg/vect/bb-slp-78.c: New testcase.
---
 gcc/testsuite/gcc.dg/vect/bb-slp-78.c | 19 +++++++++++++++++++
 gcc/tree-vect-stmts.cc                |  4 ++--
 2 files changed, 21 insertions(+), 2 deletions(-)
 create mode 100644 gcc/testsuite/gcc.dg/vect/bb-slp-78.c

diff --git a/gcc/testsuite/gcc.dg/vect/bb-slp-78.c b/gcc/testsuite/gcc.dg/vect/bb-slp-78.c
new file mode 100644
index 00000000000..6ca04d87e77
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/vect/bb-slp-78.c
@@ -0,0 +1,19 @@
+/* { dg-do compile } */
+/* { dg-additional-options "-march=x86-64-v2" { target { x86_64-*-* i?86-*-* } } } */
+
+typedef struct {
+  float xmin, xmax;
+  float ymin, ymax;
+} rctf;
+short U_0;
+int node_find_indicated_socket_in_out;
+void BLI_rctf_isect_pt(rctf *);
+void node_find_indicated_socket(float cursor[])
+{
+  rctf rect;
+  rect.xmin = rect.ymin = cursor[1] - 4;
+  rect.xmax = rect.ymax = cursor[1] + 0;
+  if (node_find_indicated_socket_in_out)
+    rect.xmax += rect.xmin -= U_0;
+  BLI_rctf_isect_pt(&rect);
+}
diff --git a/gcc/tree-vect-stmts.cc b/gcc/tree-vect-stmts.cc
index 57026ba8b0f..7ecbc8fb391 100644
--- a/gcc/tree-vect-stmts.cc
+++ b/gcc/tree-vect-stmts.cc
@@ -3412,7 +3412,6 @@ vectorizable_call (vec_info *vinfo,
   gcall *stmt;
   tree vec_dest;
   tree scalar_dest;
-  tree op;
   tree vec_oprnd0 = NULL_TREE;
   tree vectype_out, vectype_in;
   poly_uint64 nunits_in;
@@ -3504,7 +3503,7 @@ vectorizable_call (vec_info *vinfo,
 	}
 
       if (!vect_is_simple_use (vinfo, slp_node,
-			       i, &op, &slp_op[i], &dt[i], &vectypes[i]))
+			       i, &slp_op[i], &dt[i], &vectypes[i]))
 	{
 	  if (dump_enabled_p ())
 	    dump_printf_loc (MSG_MISSED_OPTIMIZATION, vect_location,
@@ -3513,6 +3512,7 @@ vectorizable_call (vec_info *vinfo,
 	}
 
       /* We can only handle calls with arguments of the same type.  */
+      tree op = gimple_call_arg (stmt, i);
       if (rhs_type
 	  && !types_compatible_p (rhs_type, TREE_TYPE (op)))
 	{
-- 
2.51.0