2015-12-16 Richard Biener <rguenther@suse.de>

	PR tree-optimization/68870
	* tree-cfgcleanup.c (cleanup_control_expr_graph): Add first_p
	parameter, if set only perform trivial constant folding.
	Queue other blocks with conditions for later processing.
	(cleanup_control_flow_bb): Add first_p parameter and pass it through.
	(cleanup_tree_cfg_1): Pass true for the first iteration
	cleanup_control_expr_graph.

	* gcc.dg/torture/pr68870.c: New testcase.


git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/trunk@231695 138bc75d-0d04-0410-961f-82ee72b054a4

4 files changed, 70 insertions, 14 deletions

diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index c04c01f86ea..90399d58f49 100644
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,3 +1,13 @@
+2015-12-16  Richard Biener  <rguenther@suse.de>
+
+	PR tree-optimization/68870
+	* tree-cfgcleanup.c (cleanup_control_expr_graph): Add first_p
+	parameter, if set only perform trivial constant folding.
+	Queue other blocks with conditions for later processing.
+	(cleanup_control_flow_bb): Add first_p parameter and pass it through.
+	(cleanup_tree_cfg_1): Pass true for the first iteration
+	cleanup_control_expr_graph.
+
 2015-12-16  Nathan Sidwell  <nathan@acm.org>
 
 	* config/nvptx/nvptx-protos.h (nvptx_hard_regno_mode_ok): Delete.
diff --git a/gcc/testsuite/ChangeLog b/gcc/testsuite/ChangeLog
index 4a058fb7a01..d4ee11c6ecb 100644
--- a/gcc/testsuite/ChangeLog
+++ b/gcc/testsuite/ChangeLog
@@ -1,3 +1,8 @@
+2015-12-16  Richard Biener  <rguenther@suse.de>
+
+	PR tree-optimization/68870
+	* gcc.dg/torture/pr68870.c: New testcase.
+
 2015-12-16  Tom de Vries  <tom@codesourcery.com>
 
 	* g++.dg/ipa/devirt-37.C: Update for new fre2 pass.
diff --git a/gcc/testsuite/gcc.dg/torture/pr68870.c b/gcc/testsuite/gcc.dg/torture/pr68870.c
new file mode 100644
index 00000000000..1ad0f7b604b
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/torture/pr68870.c
@@ -0,0 +1,29 @@
+/* { dg-do compile } */
+
+int printf (const char *, ...);
+
+int a, f, g;
+char b, d;
+short c;
+static short e;
+
+char
+fn1 ()
+{
+  for (; b; b++)
+    {
+      int h = 5;
+      for (a = 0; a < 1; a++)
+	{
+	  for (d = 0; d < 1; d++)
+	    for (c = 0; c < 1; c++)
+	      for (; e >= 0;)
+		return 5;
+	  if (f)
+	    h = 0;
+	}
+      if (h)
+	printf ("%d", 0);
+    }
+  return g;
+}
diff --git a/gcc/tree-cfgcleanup.c b/gcc/tree-cfgcleanup.c
index 3f50c66af60..c5d94d07c82 100644
--- a/gcc/tree-cfgcleanup.c
+++ b/gcc/tree-cfgcleanup.c
@@ -78,7 +78,8 @@ remove_fallthru_edge (vec<edge, va_gc> *ev)
    at block BB.  */
 
 static bool
-cleanup_control_expr_graph (basic_block bb, gimple_stmt_iterator gsi)
+cleanup_control_expr_graph (basic_block bb, gimple_stmt_iterator gsi,
+			    bool first_p)
 {
   edge taken_edge;
   bool retval = false;
@@ -95,15 +96,26 @@ cleanup_control_expr_graph (basic_block bb, gimple_stmt_iterator gsi)
       switch (gimple_code (stmt))
 	{
 	case GIMPLE_COND:
-	  {
-	    code_helper rcode;
-	    tree ops[3] = {};
-	    if (gimple_simplify (stmt, &rcode, ops, NULL, no_follow_ssa_edges,
-				 no_follow_ssa_edges)
-		&& rcode == INTEGER_CST)
-	      val = ops[0];
-	    break;
-	  }
+	  /* During a first iteration on the CFG only remove trivially
+	     dead edges but mark other conditions for re-evaluation.  */
+	  if (first_p)
+	    {
+	      val = const_binop (gimple_cond_code (stmt), boolean_type_node,
+				 gimple_cond_lhs (stmt),
+				 gimple_cond_rhs (stmt));
+	      if (! val)
+		bitmap_set_bit (cfgcleanup_altered_bbs, bb->index);
+	    }
+	  else
+	    {
+	      code_helper rcode;
+	      tree ops[3] = {};
+	      if (gimple_simplify (stmt, &rcode, ops, NULL, no_follow_ssa_edges,
+				   no_follow_ssa_edges)
+		  && rcode == INTEGER_CST)
+		val = ops[0];
+	    }
+	  break;
 
 	case GIMPLE_SWITCH:
 	  val = gimple_switch_index (as_a <gswitch *> (stmt));
@@ -176,7 +188,7 @@ cleanup_call_ctrl_altering_flag (gimple *bb_end)
    true if anything changes.  */
 
 static bool
-cleanup_control_flow_bb (basic_block bb)
+cleanup_control_flow_bb (basic_block bb, bool first_p)
 {
   gimple_stmt_iterator gsi;
   bool retval = false;
@@ -199,7 +211,7 @@ cleanup_control_flow_bb (basic_block bb)
       || gimple_code (stmt) == GIMPLE_SWITCH)
     {
       gcc_checking_assert (gsi_stmt (gsi_last_bb (bb)) == stmt);
-      retval |= cleanup_control_expr_graph (bb, gsi);
+      retval |= cleanup_control_expr_graph (bb, gsi, first_p);
     }
   else if (gimple_code (stmt) == GIMPLE_GOTO
 	   && TREE_CODE (gimple_goto_dest (stmt)) == ADDR_EXPR
@@ -680,7 +692,7 @@ cleanup_tree_cfg_1 (void)
     {
       bb = BASIC_BLOCK_FOR_FN (cfun, i);
       if (bb)
-	retval |= cleanup_control_flow_bb (bb);
+	retval |= cleanup_control_flow_bb (bb, true);
     }
 
   /* After doing the above SSA form should be valid (or an update SSA
@@ -708,7 +720,7 @@ cleanup_tree_cfg_1 (void)
       if (!bb)
 	continue;
 
-      retval |= cleanup_control_flow_bb (bb);
+      retval |= cleanup_control_flow_bb (bb, false);
       retval |= cleanup_tree_cfg_bb (bb);
     }