re PR tree-optimization/42719 ("-fcompare-debug failure" with "-O2 -ftracer")

	PR tree-optimization/42719
	* tree-outof-ssa.c (trivially_conflicts_p): Don't consider debug
	stmt uses.

	* gcc.dg/pr42719.c: New test.

From-SVN: r156038

gcc/ChangeLog

 2010-01-19  Jakub Jelinek  <jakub@redhat.com>
 
+	PR tree-optimization/42719
+	* tree-outof-ssa.c (trivially_conflicts_p): Don't consider debug
+	stmt uses.
+
 	PR debug/42728
 	* fwprop.c (all_uses_available_at): Return false if def_set dest
 	is a REG that is used in def_insn.

gcc/testsuite/ChangeLog

 2010-01-19  Jakub Jelinek  <jakub@redhat.com>
 
+	PR tree-optimization/42719
+	* gcc.dg/pr42719.c: New test.
+
 	PR debug/42728
 	* gcc.dg/pr42728.c: New test.
 

gcc/testsuite/gcc.dg/pr42719.c

+/* PR tree-optimization/42719 */
+/* { dg-do compile } */
+/* { dg-options "-O2 -ftracer -fcompare-debug" } */
+
+int *v;
+
+void
+foo (int a)
+{
+  int i, j;
+  for (j = i = a; i != -1; j = i, i = v[i])
+    ;
+  v[j] = v[a];
+}

gcc/tree-outof-ssa.c

@@ -956,6 +956,8 @@ trivially_conflicts_p (basic_block bb, tree result, tree arg)
   FOR_EACH_IMM_USE_FAST (use, imm_iter, result)
     {
       gimple use_stmt = USE_STMT (use);
+      if (is_gimple_debug (use_stmt))
+	continue;
       /* Now, if there's a use of RESULT that lies outside this basic block,
 	 then there surely is a conflict with ARG.  */
       if (gimple_bb (use_stmt) != bb)