re PR target/71185 (ice in gimplify_modify_expr, at gimplify.c:4873)

2016-05-20  Richard Biener  <rguenther@suse.de>

	PR tree-optimization/71185
	* tree-ssa-loop-prefetch.c (gather_memory_references): Drop
	register operations.

	* gcc.dg/tree-ssa/pr71185.c: New testcase.

From-SVN: r236499

gcc/ChangeLog

 2016-05-20  Richard Biener  <rguenther@suse.de>
 
+	PR tree-optimization/71185
+	* tree-ssa-loop-prefetch.c (gather_memory_references): Drop
+	register operations.
+
+2016-05-20  Richard Biener  <rguenther@suse.de>
+
 	* tree-if-conv.c (add_bb_predicate_gimplified_stmts): Use
 	gimple_seq_add_seq_without_update.
 	(release_bb_predicate): Assert we have no operands to free.

gcc/testsuite/ChangeLog

 2016-05-20  Richard Biener  <rguenther@suse.de>
 
+	PR tree-optimization/71185
+	* gcc.dg/tree-ssa/pr71185.c: New testcase.
+
+2016-05-20  Richard Biener  <rguenther@suse.de>
+
 	* gcc.dg/tree-ssa/ifc-cd.c: Adjust.
 
 2016-05-19  Marek Polacek  <polacek@redhat.com>

gcc/testsuite/gcc.dg/tree-ssa/pr71185.c

+/* { dg-do compile } */
+/* { dg-options "-O3" } */
+/* { dg-options "-O3 -march=barcelona" { target x86_64-*-* i?86-*-* } } */
+
+union U { struct S { int l; int m; } p; long long a; } b;
+int a, c;
+
+void
+foo ()
+{
+  for (; b.p.m; b.a += c)
+    a = b.p.l / 65536.0 * 65536.0;
+}

gcc/tree-ssa-loop-prefetch.c

@@ -631,6 +631,9 @@ gather_memory_references (struct loop *loop, bool *no_other_refs, unsigned *ref_
 	      continue;
 	    }
 
+	  if (! gimple_vuse (stmt))
+	    continue;
+
 	  lhs = gimple_assign_lhs (stmt);
 	  rhs = gimple_assign_rhs1 (stmt);