[google] Add options to pattern match function name for hotness attributes

[Dehao Chen <dehao at google dot com>]

Hi,

This patch adds 4 flags to enable user to type in a list of name
patterns. Compiler will match the function name with the given
patterns, and add "hot", "cold", "likely_hot", "likely_cold"
attributes to function declaration. The static branch prediction
checks if a basic block contains call to a annotated function, and set
the branch probability accordingly.

Bootstrapped and passed gcc testsuites.

Ok for google branches?

Thanks,
Dehao

gcc/ChangeLog.google-4_6
2012-06-01  Dehao Chen  <dehao@google.com>

	* gcc/cgraph.c (cgraph_match_hotness_by_name): New function.
	(cgraph_add_hotness_attribute): New function.
	(cgraph_node): Add hotness attribute to function decl.
	* gcc/opts.c (common_handle_option): Handle new options.
	* gcc/predict.c (tree_bb_level_predictions): New prediction.
	* gcc/predict.def (PRED_LIKELY_COLD_FUNCTION): New prediction.
	* gcc/common.opt (flag_function_hot_list): New option.
	(flag_function_cold_list): New option.
	(flag_function_likely_hot_list): New option.
	(flag_function_likely_cold_list): New option.

Index: gcc/doc/invoke.texi
===================================================================
--- gcc/doc/invoke.texi	(revision 188050)
+++ gcc/doc/invoke.texi	(working copy)
@@ -362,7 +362,9 @@
 -fdelete-null-pointer-checks -fdse -fdevirtualize -fdse @gol
 -fearly-inlining -fipa-sra -fexpensive-optimizations -ffast-math @gol
 -ffinite-math-only -ffloat-store -fexcess-precision=@var{style} @gol
--fforward-propagate -ffp-contract=@var{style} -ffunction-sections @gol
+-fforward-propagate -ffp-contract=@var{style} @gol
+-ffunction-cold-list -ffunction-hot-list -ffunction-likely-cold-list @gol
+-ffunction-likely-hot-list -ffunction-sections @gol
 -fgcse -fgcse-after-reload -fgcse-las -fgcse-lm -fgraphite-identity @gol
 -fgcse-sm -fif-conversion -fif-conversion2 -findirect-inlining @gol
 -finline-functions -finline-functions-called-once -finline-limit=@var{n} @gol
@@ -8585,6 +8587,22 @@
 specify this option and you may have problems with debugging if
 you specify both this option and @option{-g}.

+@item -ffunction-cold-list
+@opindex ffunction-cold-list
+List of function name patterns that will be applied "cold" attribute.
+
+@item -ffunction-hot-list
+@opindex ffunction-hot-list
+List of function name patterns that will be applied "hot" attribute.
+
+@item -ffunction-likely-cold-list
+@opindex ffunction-likely-cold-list
+List of function name patterns that will be applied "likely_cold" attribute.
+
+@item -ffunction-likely-hot-list
+@opindex ffunction-likely-hot-list
+List of function name patterns that will be applied "likely_hot" attribute.
+
 @item -fbranch-target-load-optimize
 @opindex fbranch-target-load-optimize
 Perform branch target register load optimization before prologue / epilogue
Index: gcc/cgraph.c
===================================================================
--- gcc/cgraph.c	(revision 188050)
+++ gcc/cgraph.c	(working copy)
@@ -520,6 +520,70 @@
     }
 }

+typedef char *char_pointer;
+DEF_VEC_P(char_pointer);
+DEF_VEC_ALLOC_P(char_pointer,heap);
+
+/* Match FNDECL's name with PATTERNS. If matched, add HOTNESS attribute
+   to FNDECL.
+   name matches with pattern, iff one of the following conditions satisfy:
+     1. strcmp (name, pattern) != 0
+     2. pattern[len - 1] = '*' && strncmp (name, pattern, len - 1) != 0  */
+static bool
+cgraph_match_hotness_by_name (tree fndecl,
+			      VEC(char_pointer, heap) *patterns,
+			      const char *hotness)
+{
+  unsigned i;
+  char_pointer n;
+  const char *name = lang_hooks.decl_printable_name(fndecl, 0);
+
+  if (!name)
+    return false;
+
+  FOR_EACH_VEC_ELT (char_pointer, patterns, i, n)
+    {
+      int len = strlen (n);
+      if ((n[len - 1] == '*' && !strncmp (name, n, len - 1))
+          || !strcmp (name, n))
+        {
+          decl_attributes (&fndecl, tree_cons (
+              get_identifier (hotness), NULL, NULL), 0);
+          return true;
+        }
+    }
+  return false;
+}
+
+/* Add hotness attributes to FNDECL.  */
+static void
+cgraph_add_hotness_attribute (tree fndecl)
+{
+  if (lookup_attribute ("cold", DECL_ATTRIBUTES (fndecl))
+      || lookup_attribute ("hot", DECL_ATTRIBUTES (fndecl))
+      || lookup_attribute ("likely_cold", DECL_ATTRIBUTES (fndecl))
+      || lookup_attribute ("likely_hot", DECL_ATTRIBUTES (fndecl)))
+    return;
+
+  if (cgraph_match_hotness_by_name (fndecl,
+	(VEC(char_pointer, heap) *) flag_function_cold_list, "cold"))
+    return;
+
+  if (cgraph_match_hotness_by_name (fndecl,
+	(VEC(char_pointer, heap) *) flag_function_hot_list, "hot"))
+    return;
+
+  if (cgraph_match_hotness_by_name (fndecl,
+	(VEC(char_pointer, heap) *) flag_function_likely_cold_list,
+	"likely_cold"))
+    return;
+
+  if (cgraph_match_hotness_by_name (fndecl,
+	(VEC(char_pointer, heap) *) flag_function_likely_hot_list,
+	"likely_hot"))
+    return;
+}
+
 /* Return cgraph node assigned to DECL.  Create new one when needed.  */

 struct cgraph_node *
@@ -554,6 +618,7 @@
       node->origin->nested = node;
     }
   cgraph_add_assembler_hash_node (node);
+  cgraph_add_hotness_attribute (decl);
   return node;
 }

Index: gcc/opts.c
===================================================================
--- gcc/opts.c	(revision 188050)
+++ gcc/opts.c	(working copy)
@@ -1539,6 +1539,26 @@
 	(&opts->x_flag_instrument_functions_exclude_files, arg);
       break;

+    case OPT_ffunction_hot_list_:
+      add_comma_separated_to_vector
+	(&opts->x_flag_function_hot_list, arg);
+      break;
+
+    case OPT_ffunction_cold_list_:
+      add_comma_separated_to_vector
+	(&opts->x_flag_function_cold_list, arg);
+      break;
+
+    case OPT_ffunction_likely_hot_list_:
+      add_comma_separated_to_vector
+	(&opts->x_flag_function_likely_hot_list, arg);
+      break;
+
+    case OPT_ffunction_likely_cold_list_:
+      add_comma_separated_to_vector
+	(&opts->x_flag_function_likely_cold_list, arg);
+      break;
+
     case OPT_fmessage_length_:
       pp_set_line_maximum_length (dc->printer, value);
       break;
Index: gcc/predict.c
===================================================================
--- gcc/predict.c	(revision 188050)
+++ gcc/predict.c	(working copy)
@@ -2070,11 +2070,22 @@
 		predict_paths_leading_to (bb, PRED_NORETURN,
 					  NOT_TAKEN);
 	      decl = gimple_call_fndecl (stmt);
-	      if (decl
-		  && lookup_attribute ("cold",
-				       DECL_ATTRIBUTES (decl)))
-		predict_paths_leading_to (bb, PRED_COLD_FUNCTION,
-					  NOT_TAKEN);
+	      if (decl)
+		{
+		  tree attr = DECL_ATTRIBUTES (decl);
+		  if (lookup_attribute ("cold", attr))
+		    predict_paths_leading_to (bb, PRED_COLD_FUNCTION,
+					      NOT_TAKEN);
+		  else if (lookup_attribute ("hot", attr))
+		    predict_paths_leading_to (bb, PRED_COLD_FUNCTION,
+					      TAKEN);
+		  else if (lookup_attribute ("likely_cold", attr))
+		    predict_paths_leading_to (bb, PRED_LIKELY_COLD_FUNCTION,
+					      NOT_TAKEN);
+		  else if (lookup_attribute ("likely_hot", attr))
+		    predict_paths_leading_to (bb, PRED_LIKELY_COLD_FUNCTION,
+					      TAKEN);
+		}
 	    }
 	  else if (gimple_code (stmt) == GIMPLE_PREDICT)
 	    {
Index: gcc/ChangeLog.google-4_6
===================================================================
--- gcc/ChangeLog.google-4_6	(revision 188050)
+++ gcc/ChangeLog.google-4_6	(working copy)
@@ -1,3 +1,16 @@
+2012-06-01  Dehao Chen  <dehao@google.com>
+
+	* gcc/cgraph.c (cgraph_match_hotness_by_name): New function.
+	(cgraph_add_hotness_attribute): New function.
+	(cgraph_node): Add hotness attribute to function decl.
+	* gcc/opts.c (common_handle_option): Handle new options.
+	* gcc/predict.c (tree_bb_level_predictions): New prediction.
+	* gcc/predict.def (PRED_LIKELY_COLD_FUNCTION): New prediction.
+	* gcc/common.opt (flag_function_hot_list): New option.
+	(flag_function_cold_list): New option.
+	(flag_function_likely_hot_list): New option.
+	(flag_function_likely_cold_list): New option.
+
 2012-05-30   Cary Coutant  <ccoutant@google.com>

 	* gcc/dwarf2out.c (index_location_lists): Don't index location
Index: gcc/predict.def
===================================================================
--- gcc/predict.def	(revision 188050)
+++ gcc/predict.def	(working copy)
@@ -76,6 +76,10 @@
 DEF_PREDICTOR (PRED_COLD_FUNCTION, "cold function call", PROB_VERY_LIKELY,
 	       PRED_FLAG_FIRST_MATCH)

+/* Branch to basic block containing call marked by likely_cold
function attribute.  */
+DEF_PREDICTOR (PRED_LIKELY_COLD_FUNCTION, "likely cold function call",
+	       HITRATE (75), PRED_FLAG_FIRST_MATCH)
+
 /* Loopback edge is taken.  */
 DEF_PREDICTOR (PRED_LOOP_BRANCH, "loop branch", HITRATE (86),
 	       PRED_FLAG_FIRST_MATCH)
Index: gcc/common.opt
===================================================================
--- gcc/common.opt	(revision 188050)
+++ gcc/common.opt	(working copy)
@@ -92,6 +92,20 @@
 Variable
 void *flag_instrument_functions_exclude_files

+; These four are VEC(char_p,heap) * that indicate function hotness.
+
+Variable
+void *flag_function_hot_list
+
+Variable
+void *flag_function_cold_list
+
+Variable
+void *flag_function_likely_hot_list
+
+Variable
+void *flag_function_likely_cold_list
+
 ; Generic structs (e.g. templates not explicitly specialized)
 ; may not have a compilation unit associated with them, and so
 ; may need to be treated differently from ordinary structs.
@@ -1242,6 +1256,22 @@
 Common Report Var(flag_function_sections)
 Place each function into its own section

+ffunction-hot-list=
+Common RejectNegative Joined
+-ffunction-hot-list=name,...  Predict listed functions as hot
+
+ffunction-cold-list=
+Common RejectNegative Joined
+-ffunction-cold-list=name,...  Predict listed functions as cold
+
+ffunction-likely-hot-list=
+Common RejectNegative Joined
+-ffunction-likely-hot-list=name,...  Predict listed functions as likely_hot
+
+ffunction-likely-cold-list=
+Common RejectNegative Joined
+-ffunction-likely-cold-list=name,...  Predict listed functions as likely_cold
+
 fgcda=
 Common Joined RejectNegative Var(gcov_da_name)
 Set the gcov data file name.