cfglayout.c (function_tail_eff_head): Rename to ...

	* cfglayout.c (function_tail_eff_head): Rename to ...
	(function_footer): ... this one.
	(unlink_insn_chain): New functions.
	(label_for_bb): Only call block_label and emit debug message.
	(record_effective_endpoints): Actually unlink the headers and footers.
	(fixup_reorder_cahin): Re-insert the unlinked sequences.
	(cfg_layout_duplicate_bb): Use duplicate_insn_chain.
	* cfglayout.h (struct reorder_block_def): New fields footer/header;
	remove eff_head/eff_end.
	* rtl.h (set_first_insn): Declare.
	* emit-rtl.c (set_first_insn): New function.

	* cfglayout.c (fixup_reorder_chain): Dump duplicated
	(cfg_layout_can_duplicate_bb_p, cfg_layout_rerirect_edge,
	cfg_layout_duplicate_bb): New global function.
	(duplicate_insn_chain): New static function.
	* cfglayout.h (cfg_layout_can_duplicate_bb_p, cfg_layout_rerirect_edge,
	cfg_layout_duplicate_bb): Declare.
	(struct reorder_block_def): Add "original" field.
	* emit-rtl.c (emit_copy_of_insn_after): New function.
	* rtl.h (emit_copy_of_insn_after): Declare.

	* cfglayout.c (fixup_fallthru_exit_predecessor): Kill.
	(fixup_reorder_chain): properly handle edges to exit block.

Wed May  8 11:10:31 CEST 2002  Zdenek Dvorak  <rakdver@atrey.karlin.mff.cuni.cz>
			       Jan Hubicka  <jh@suse.cz>

	* basic-block.h (note_prediction_to_br_prob): declare.
	* c-semantics.c: Inlucde predit.h
	(expand_stmt): predict GOTO_STMT as not taken.
	* cfgcleanup.c: (delete_unreachable_blocks): Make global.
	(cleanup_cfg): Do not free tail_recursion_list.
	* cfgrtl.c (can_delete_note_p): Delete NOTE_INSN_PREDICTION.
	(flow_delete_block): Kill predictions past end of basic block.
	* output.h (delete_unreachable_blocks): Declare.
	* predict.c (predicted_by_p, process_note_predictions,
	process_note_prediction, last_block_p): New function.
	(estimate_probability): Bypass loop on PRED_CONTINUE;
	do not handle noreturn heuristics; kill PRED_RETURN; add
	PRED_EARLY_RETURN.
	* predict.def (PRED_CONTINUE, PRED_EARLY_RETURN, PRED_GOTO,
	PRED_CONST_RETURN, PRED_NEGATIVE_RETURN, PRED_NULL_RETURN): New.
	* predict.h (IS_TAKEN): New constant.
	* print-rtl.c (print_rtx): Pretty print NOTE_INSN_PREDICTION.
	* rtl.c (NOTE_INSN_PREDICTION): New.
	* rtl.h (NOTE_PREDICTION, NOTE_PREDICTION_ALG, NOTE_PREDICTION_FLAGS):
	New macro.
	(insn_note): add NOTE_INSN_PREDICTION.
	* sibcall.c (optimize_sibling_and_tail_recursive_call): Do not build
	CFG; free tail_recursion_label_list.
	* stmt.c: Include predict.h;
	(return_prediction): New.
	(expand_value_return): Use it.
	* toplev.c: Lower NOTE_INSN_PREDICTION before sibcall.

From-SVN: r53285

1 files changed, 56 insertions, 3 deletions

diff --git a/gcc/stmt.c b/gcc/stmt.c
index 42a9659ade6..639587aa45e 100644
--- a/gcc/stmt.c
+++ b/gcc/stmt.c
@@ -54,6 +54,7 @@ Software Foundation, 59 Temple Place - Suite 330, Boston, MA
 #include "output.h"
 #include "ggc.h"
 #include "langhooks.h"
+#include "predict.h"
 
 #define obstack_chunk_alloc xmalloc
 #define obstack_chunk_free free
@@ -414,6 +415,7 @@ static tree resolve_operand_names	PARAMS ((tree, tree, tree,
 						 const char **));
 static char *resolve_operand_name_1	PARAMS ((char *, tree, tree));
 static void expand_null_return_1	PARAMS ((rtx));
+static enum br_predictor return_prediction PARAMS ((rtx));
 static void expand_value_return		PARAMS ((rtx));
 static int tail_recursion_args		PARAMS ((tree, tree));
 static void expand_cleanups		PARAMS ((tree, tree, int, int));
@@ -2824,6 +2826,11 @@ int
 expand_continue_loop (whichloop)
      struct nesting *whichloop;
 {
+  /* Emit information for branch prediction.  */
+  rtx note;
+
+  note = emit_note (NULL, NOTE_INSN_PREDICTION);
+  NOTE_PREDICTION (note) = NOTE_PREDICT (PRED_CONTINUE, IS_TAKEN);
   last_expr_type = 0;
   if (whichloop == 0)
     whichloop = loop_stack;
@@ -2965,7 +2972,9 @@ expand_exit_something ()
 void
 expand_null_return ()
 {
-  rtx last_insn = get_last_insn ();
+  rtx last_insn;
+
+  last_insn = get_last_insn ();
 
   /* If this function was declared to return a value, but we
      didn't, clobber the return registers so that they are not
@@ -2975,14 +2984,58 @@ expand_null_return ()
   expand_null_return_1 (last_insn);
 }
 
+/* Try to guess whether the value of return means error code.  */
+static enum br_predictor
+return_prediction (val)
+     rtx val;
+{
+  /* Different heuristics for pointers and scalars.  */
+  if (POINTER_TYPE_P (TREE_TYPE (DECL_RESULT (current_function_decl))))
+    {
+      /* NULL is usually not returned.  */
+      if (val == const0_rtx)
+	return PRED_NULL_RETURN;
+    }
+  else
+    {
+      /* Negative return values are often used to indicate
+         errors.  */
+      if (GET_CODE (val) == CONST_INT
+	  && INTVAL (val) < 0)
+	return PRED_NEGATIVE_RETURN;
+      /* Constant return values are also usually erors,
+         zero/one often mean booleans so exclude them from the
+	 heuristics.  */
+      if (CONSTANT_P (val)
+	  && (val != const0_rtx && val != const1_rtx))
+	return PRED_CONST_RETURN;
+    }
+  return PRED_NO_PREDICTION;
+}
+
 /* Generate RTL to return from the current function, with value VAL.  */
 
 static void
 expand_value_return (val)
      rtx val;
 {
-  rtx last_insn = get_last_insn ();
-  rtx return_reg = DECL_RTL (DECL_RESULT (current_function_decl));
+  rtx last_insn;
+  rtx return_reg;
+  enum br_predictor pred;
+
+  if ((pred = return_prediction (val)) != PRED_NO_PREDICTION)
+    {
+      /* Emit information for branch prediction.  */
+      rtx note;
+
+      note = emit_note (NULL, NOTE_INSN_PREDICTION);
+
+      NOTE_PREDICTION (note) = NOTE_PREDICT (pred, NOT_TAKEN);
+
+    }
+
+  last_insn = get_last_insn ();
+  return_reg = DECL_RTL (DECL_RESULT (current_function_decl));
 
   /* Copy the value to the return location
      unless it's already there.  */