Fix invalid assumption in vect_transform_stmt (PR 86871)

The handling of outer-loop uses of inner-loop definitions assumed
that anything that wasn't a PHI would be a gassign.  It's also
possible for it to be a gcall.

2018-08-08  Richard Sandiford  <richard.sandiford@arm.com>

gcc/
	PR tree-optimization/86871
	* tree-vect-stmts.c (vect_transform_stmt): Use gimple_get_lhs
	instead of gimple_assign_lhs.

gcc/testsuite/
	PR tree-optimization/86871
	* gcc.dg/vect/pr86871.c: New test.

From-SVN: r263447

gcc/ChangeLog

+2018-08-09  Richard Sandiford  <richard.sandiford@arm.com>
+
+	PR tree-optimization/86871
+	* tree-vect-stmts.c (vect_transform_stmt): Use gimple_get_lhs
+	instead of gimple_assign_lhs.
+
 2018-08-09  Richard Earnshaw  <rearnsha@arm.com>
 
 	PR target/86887

gcc/testsuite/ChangeLog

+2018-08-09  Richard Sandiford  <richard.sandiford@arm.com>
+
+	PR tree-optimization/86871
+	* gcc.dg/vect/pr86871.c: New test.
+
 2018-08-09  Paolo Carlini  <paolo.carlini@oracle.com>
 
 	* g++.old-deja/g++.mike/p784.C: Add -fpermissive.

gcc/testsuite/gcc.dg/vect/pr86871.c

+/* { dg-do compile } */
+
+extern int b[];
+extern int c[];
+void g(int f) {
+  for (; f; f++) {
+    int d = 0;
+    for (int e = -1; e <= 1; e++) {
+      int a = f + e;
+      if (a)
+        d = *(c + a);
+    }
+    *(b + f) = d;
+  }
+ }

gcc/tree-vect-stmts.c

@@ -9804,7 +9804,7 @@ vect_transform_stmt (stmt_vec_info stmt_info, gimple_stmt_iterator *gsi,
       if (gimple_code (stmt) == GIMPLE_PHI)
         scalar_dest = PHI_RESULT (stmt);
       else
-        scalar_dest = gimple_assign_lhs (stmt);
+        scalar_dest = gimple_get_lhs (stmt);
 
       FOR_EACH_IMM_USE_FAST (use_p, imm_iter, scalar_dest)
 	if (!flow_bb_inside_loop_p (innerloop, gimple_bb (USE_STMT (use_p))))