PR rtl-optimization/pr55153

2013-01-15  Vladimir Makarov  <vmakarov@redhat.com>

	PR rtl-optimization/pr55153
	* sched-deps.c (sched_analyze_2): Add pending reads for prefetch.

2013-01-15  Vladimir Makarov  <vmakarov@redhat.com>

	PR rtl-optimization/pr55153
	* gcc.dg/pr55153.c: New.

From-SVN: r195211

gcc/ChangeLog

+2013-01-15  Vladimir Makarov  <vmakarov@redhat.com>
+
+	PR rtl-optimization/pr55153
+	* sched-deps.c (sched_analyze_2): Add pending reads for prefetch.
+
 2013-01-15  Martin Jambor  <mjambor@suse.cz>
 
 	PR tree-optimization/55920

gcc/sched-deps.c

@@ -2707,6 +2707,20 @@ sched_analyze_2 (struct deps_desc *deps, rtx x, rtx insn)
     case PREFETCH:
       if (PREFETCH_SCHEDULE_BARRIER_P (x))
 	reg_pending_barrier = TRUE_BARRIER;
+      /* Prefetch insn contains addresses only.  So if the prefetch
+	 address has no registers, there will be no dependencies on
+	 the prefetch insn.  This is wrong with result code
+	 correctness point of view as such prefetch can be moved below
+	 a jump insn which usually generates MOVE_BARRIER preventing
+	 to move insns containing registers or memories through the
+	 barrier.  It is also wrong with generated code performance
+	 point of view as prefetch withouth dependecies will have a
+	 tendency to be issued later instead of earlier.  It is hard
+	 to generate accurate dependencies for prefetch insns as
+	 prefetch has only the start address but it is better to have
+	 something than nothing.  */
+      add_insn_mem_dependence (deps, true, insn,
+			       gen_rtx_MEM (Pmode, XEXP (PATTERN (insn), 0)));
       break;
 
     case UNSPEC_VOLATILE:

gcc/testsuite/ChangeLog

+2013-01-15  Vladimir Makarov  <vmakarov@redhat.com>
+
+	PR rtl-optimization/pr55153
+	* gcc.dg/pr55153.c: New.
+
 2013-01-15  Jakub Jelinek  <jakub@redhat.com>
 
 	PR tree-optimization/55920

gcc/testsuite/gcc.dg/pr55153.c

+/* PR tree-optimization/55153 */
+/* { dg-do compile } */
+/* { dg-options "-O -fsched2-use-superblocks -fschedule-insns2" } */
+
+extern int a[];
+
+void
+foo (void)
+{
+  __builtin_prefetch (a, 0, 0);
+}