Makefile.in (toplev.o): Add value-prof.h dependency.

	* Makefile.in (toplev.o): Add value-prof.h dependency.
	(value-prof.o): Add REGS_H dependency.
	* common.opt (fprofile-values, fvpt): New.
	* flags.h (flag_value_profile_transformations): Declare.
	* opts.c (common_handle_option): Handle -fprofile_values and
	-fvpt.
	* profile.c (branch_prob): Don't remove death notes here.
	* timevar.def (TV_VPT): New.
	* value-prof.c: Include regs.h.
	(insn_divmod_values_to_profile, gen_divmod_fixed_value, gen_mod_pow2,
	gen_mod_subtract, divmod_fixed_value_transform,mod_pow2_value_transform,
	mod_subtract_transform, value_profile_transformations): New.
	(insn_values_to_profile): Call insn_divmod_values_to_profile.
	(find_values_to_profile): Add dumps.
	* value-prof.h (value_profile_transformations): Declare.
	* toplev.c: Include value-prof.h.
	(rest_of_handle_value_profile_transformations): New.
	(enum dump_file_index): Add DFI_vpt.
	(dump_file): Add vpt dump.
	(flag_value_profile_transformations): New.
	(lang_independent_options): Add flag_profile_values and
	flag_value_profile_transformations.
	(rest_of_compilation): Call
	rest_of_handle_value_profile_transformations.
	(process_options): Let -fvpt imply -fprofile-values.
	* doc/invoke.texi (-fvpt): Document.

From-SVN: r72685

11 files changed, 703 insertions, 10 deletions

diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index f65329c..5dc8b68 100644
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,3 +1,32 @@
+2003-10-19  Zdenek Dvorak  <rakdver@atrey.karlin.mff.cuni.cz>
+
+	* Makefile.in (toplev.o): Add value-prof.h dependency.
+	(value-prof.o): Add REGS_H dependency.
+	* common.opt (fprofile-values, fvpt): New.
+	* flags.h (flag_value_profile_transformations): Declare.
+	* opts.c (common_handle_option): Handle -fprofile_values and
+	-fvpt.
+	* profile.c (branch_prob): Don't remove death notes here.
+	* timevar.def (TV_VPT): New.
+	* value-prof.c: Include regs.h.
+	(insn_divmod_values_to_profile, gen_divmod_fixed_value, gen_mod_pow2,
+	gen_mod_subtract, divmod_fixed_value_transform,mod_pow2_value_transform,
+	mod_subtract_transform, value_profile_transformations): New.
+	(insn_values_to_profile): Call insn_divmod_values_to_profile.
+	(find_values_to_profile): Add dumps.
+	* value-prof.h (value_profile_transformations): Declare.
+	* toplev.c: Include value-prof.h.
+	(rest_of_handle_value_profile_transformations): New.
+	(enum dump_file_index): Add DFI_vpt.
+	(dump_file): Add vpt dump.
+	(flag_value_profile_transformations): New.
+	(lang_independent_options): Add flag_profile_values and
+	flag_value_profile_transformations.
+	(rest_of_compilation): Call
+	rest_of_handle_value_profile_transformations.
+	(process_options): Let -fvpt imply -fprofile-values.
+	* doc/invoke.texi (-fvpt): Document.
+
 2003-10-19  Jan Hubicka  <jh@suse.cz>
 
 	* i386.c (print_reg): Do not abort on certain registers.
diff --git a/gcc/Makefile.in b/gcc/Makefile.in
index 492118a..7ba6b7d 100644
--- a/gcc/Makefile.in
+++ b/gcc/Makefile.in
@@ -1499,7 +1499,7 @@ toplev.o : toplev.c $(CONFIG_H) $(SYSTEM_H) coretypes.h $(TM_H) $(TREE_H) $(RTL_
    function.h flags.h xcoffout.h input.h $(INSN_ATTR_H) output.h $(DIAGNOSTIC_H) \
    debug.h insn-config.h intl.h $(RECOG_H) Makefile toplev.h \
    dwarf2out.h sdbout.h dbxout.h $(EXPR_H) hard-reg-set.h $(BASIC_BLOCK_H) \
-   graph.h $(LOOP_H) except.h $(REGS_H) $(TIMEVAR_H) \
+   graph.h $(LOOP_H) except.h $(REGS_H) $(TIMEVAR_H) value-prof.h \
    ssa.h $(PARAMS_H) $(TM_P_H) reload.h dwarf2asm.h $(TARGET_H) \
    langhooks.h insn-flags.h cfglayout.h real.h cfgloop.h \
    hosthooks.h $(LANGHOOKS_DEF_H) cgraph.h $(COVERAGE_H)
@@ -1653,7 +1653,7 @@ profile.o : profile.c $(CONFIG_H) $(SYSTEM_H) coretypes.h $(TM_H) $(RTL_H) \
    toplev.h $(BASIC_BLOCK_H) $(COVERAGE_H) $(TREE_H) value-prof.h
 value-prof.o : value-prof.c $(CONFIG_H) $(SYSTEM_H) coretypes.h $(TM_H) $(RTL_H) \
    $(BASIC_BLOCK_H) hard-reg-set.h value-prof.h $(EXPR_H) output.h flags.h \
-   $(RECOG_H) insn-config.h $(OPTABS_H)
+   $(RECOG_H) insn-config.h $(OPTABS_H) $(REGS_H)
 loop.o : loop.c $(CONFIG_H) $(SYSTEM_H) coretypes.h $(TM_H) $(RTL_H) flags.h $(LOOP_H) \
    insn-config.h $(REGS_H) hard-reg-set.h $(RECOG_H) $(EXPR_H) \
    real.h $(PREDICT_H) $(BASIC_BLOCK_H) function.h cfgloop.h \
diff --git a/gcc/common.opt b/gcc/common.opt
index fdf28b2..2ad0e0a5 100644
--- a/gcc/common.opt
+++ b/gcc/common.opt
@@ -517,6 +517,10 @@ fprofile-arcs
 Common
 Insert arc-based program profiling code
 
+fprofile-values
+Common
+Insert code to profile values of expressions
+
 frandom-seed
 Common
 
@@ -719,6 +723,10 @@ fverbose-asm
 Common
 Add extra commentary to assembler output
 
+fvpt
+Common
+Use expression value profiles in optimizations
+
 fweb
 Common
 Construct webs and split unrelated uses of single variable
diff --git a/gcc/doc/invoke.texi b/gcc/doc/invoke.texi
index a154b7c..c99af2c 100644
--- a/gcc/doc/invoke.texi
+++ b/gcc/doc/invoke.texi
@@ -264,7 +264,7 @@ in the following sections.
 @xref{Optimize Options,,Options that Control Optimization}.
 @gccoptlist{-falign-functions=@var{n}  -falign-jumps=@var{n} @gol
 -falign-labels=@var{n}  -falign-loops=@var{n}  @gol
--fbranch-probabilities -fprofile-values -fbranch-target-load-optimize @gol
+-fbranch-probabilities -fprofile-values -fvpt -fbranch-target-load-optimize @gol
 -fbranch-target-load-optimize2 -fcaller-saves  -fcprop-registers @gol
 -fcse-follow-jumps  -fcse-skip-blocks  -fdata-sections @gol
 -fdelayed-branch  -fdelete-null-pointer-checks @gol
@@ -4564,6 +4564,16 @@ With @option{-fbranch-probabilities}, it reads back the data gathered
 from profiling values of expressions and adds @samp{REG_VALUE_PROFILE}
 notes to instructions for their later usage in optimizations.
 
+@item -fvpt
+@opindex fvpt
+If combined with @option{-fprofile-arcs}, it instructs the compiler to add
+a code to gather information about values of expressions.
+
+With @option{-fbranch-probabilities}, it reads back the data gathered
+and actually performs the optimizations based on them.
+Currently the optimizations include specialization of division operation
+using the knowledge about the value of the denominator.
+
 @item -fnew-ra
 @opindex fnew-ra
 Use a graph coloring register allocator.  Currently this option is meant
diff --git a/gcc/flags.h b/gcc/flags.h
index 2a1a10f..5b6f728 100644
--- a/gcc/flags.h
+++ b/gcc/flags.h
@@ -680,6 +680,9 @@ extern int flag_gcse_sm;
 
 extern int flag_gcse_las;
 
+/* Nonzero if value histograms should be used to optimize code.  */
+extern int flag_value_profile_transformations;
+
 /* Perform branch target register optimization before prologue / epilogue
    threading.  */
 
diff --git a/gcc/opts.c b/gcc/opts.c
index e4c9ad4..6439e26 100644
--- a/gcc/opts.c
+++ b/gcc/opts.c
@@ -1182,6 +1182,14 @@ common_handle_option (size_t scode, const char *arg,
       profile_arc_flag = value;
       break;
 
+    case OPT_fprofile_values:
+      flag_profile_values = value;
+      break;
+
+    case OPT_fvpt:
+      flag_value_profile_transformations = value;
+      break;
+
     case OPT_frandom_seed:
       /* The real switch is -fno-random-seed.  */
       if (value)
diff --git a/gcc/profile.c b/gcc/profile.c
index 082ed32..625a904 100644
--- a/gcc/profile.c
+++ b/gcc/profile.c
@@ -988,8 +988,6 @@ branch_prob (void)
       allocate_reg_info (max_reg_num (), FALSE, FALSE);
     }
 
-  if (flag_profile_values)
-    count_or_remove_death_notes (NULL, 1);
   remove_fake_edges ();
   free_aux_for_edges ();
   /* Re-merge split basic blocks and the mess introduced by
diff --git a/gcc/timevar.def b/gcc/timevar.def
index 99a0b09..74fda87 100644
--- a/gcc/timevar.def
+++ b/gcc/timevar.def
@@ -72,6 +72,7 @@ DEFTIMEVAR (TV_TRACER                , "tracer")
 DEFTIMEVAR (TV_WEB                   , "web")
 DEFTIMEVAR (TV_CSE2                  , "CSE 2")
 DEFTIMEVAR (TV_BRANCH_PROB           , "branch prediction")
+DEFTIMEVAR (TV_VPT                   , "value profile opts")
 DEFTIMEVAR (TV_FLOW                  , "flow analysis")
 DEFTIMEVAR (TV_COMBINE               , "combiner")
 DEFTIMEVAR (TV_IFCVT		     , "if-conversion")
diff --git a/gcc/toplev.c b/gcc/toplev.c
index c1a05f6..151f6c6 100644
--- a/gcc/toplev.c
+++ b/gcc/toplev.c
@@ -78,6 +78,7 @@ Software Foundation, 59 Temple Place - Suite 330, Boston, MA
 #include "cgraph.h"
 #include "opts.h"
 #include "coverage.h"
+#include "value-prof.h"
 
 #if defined (DWARF2_UNWIND_INFO) || defined (DWARF2_DEBUGGING_INFO)
 #include "dwarf2out.h"
@@ -137,6 +138,7 @@ static void rest_of_handle_null_pointer (tree, rtx);
 static void rest_of_handle_addressof (tree, rtx);
 static void rest_of_handle_cfg (tree, rtx);
 static void rest_of_handle_branch_prob (tree, rtx);
+static void rest_of_handle_value_profile_transformations (tree, rtx);
 static void rest_of_handle_if_conversion (tree, rtx);
 static void rest_of_handle_if_after_combine (tree, rtx);
 static void rest_of_handle_tracer (tree, rtx);
@@ -264,6 +266,7 @@ enum dump_file_index
   DFI_bypass,
   DFI_cfg,
   DFI_bp,
+  DFI_vpt,
   DFI_ce1,
   DFI_tracer,
   DFI_web,
@@ -296,7 +299,7 @@ enum dump_file_index
    Remaining -d letters:
 
 	"            m   q         "
-	"         JK   O Q    V  Y "
+	"         JK   O Q       Y "
 */
 
 static struct dump_file_info dump_file[DFI_MAX] =
@@ -318,6 +321,7 @@ static struct dump_file_info dump_file[DFI_MAX] =
   { "bypass",   'G', 1, 0, 0 }, /* Yes, duplicate enable switch.  */
   { "cfg",	'f', 1, 0, 0 },
   { "bp",	'b', 1, 0, 0 },
+  { "vpt",	'V', 1, 0, 0 },
   { "ce1",	'C', 1, 0, 0 },
   { "tracer",	'T', 1, 0, 0 },
   { "web",      'Z', 0, 0, 0 },
@@ -404,6 +408,9 @@ int profile_arc_flag = 0;
 
 int flag_profile_values = 0;
 
+/* Nonzero if value histograms should be used to optimize code.  */
+int flag_value_profile_transformations = 0;
+
 /* Nonzero if generating info for gcov to calculate line test coverage.  */
 
 int flag_test_coverage = 0;
@@ -1110,6 +1117,8 @@ static const lang_independent_options f_options[] =
   {"asynchronous-unwind-tables", &flag_asynchronous_unwind_tables, 1 },
   {"non-call-exceptions", &flag_non_call_exceptions, 1 },
   {"profile-arcs", &profile_arc_flag, 1 },
+  {"profile-values", &flag_profile_values, 1 },
+  {"vpt", &flag_value_profile_transformations, 1 },
   {"test-coverage", &flag_test_coverage, 1 },
   {"branch-probabilities", &flag_branch_probabilities, 1 },
   {"profile", &profile_flag, 1 },
@@ -2462,6 +2471,7 @@ rest_of_handle_branch_prob (tree decl, rtx insns)
 
   timevar_push (TV_BRANCH_PROB);
   open_dump_file (DFI_bp, decl);
+
   if (profile_arc_flag || flag_test_coverage || flag_branch_probabilities)
     branch_prob ();
 
@@ -2481,6 +2491,20 @@ rest_of_handle_branch_prob (tree decl, rtx insns)
   timevar_pop (TV_BRANCH_PROB);
 }
 
+/* Do optimizations based on expression value profiles.  */
+static void
+rest_of_handle_value_profile_transformations (tree decl, rtx insns)
+{
+  open_dump_file (DFI_vpt, decl);
+  timevar_push (TV_VPT);
+
+  if (value_profile_transformations ())
+    cleanup_cfg (CLEANUP_EXPENSIVE);
+
+  timevar_pop (TV_VPT);
+  close_dump_file (DFI_vpt, print_rtl_with_bb, insns);
+}
+
 /* Do control and data flow analysis; write some of the results to the
    dump file.  */
 static void
@@ -3345,7 +3369,18 @@ rest_of_compilation (tree decl)
 
   if (optimize > 0
       || profile_arc_flag || flag_test_coverage || flag_branch_probabilities)
-    rest_of_handle_branch_prob (decl, insns);
+    {
+      rest_of_handle_branch_prob (decl, insns);
+
+      if (flag_branch_probabilities
+	  && flag_profile_values
+	  && flag_value_profile_transformations)
+	rest_of_handle_value_profile_transformations (decl, insns);
+
+      /* Remove the death notes created for vpt.  */
+      if (flag_profile_values)
+	count_or_remove_death_notes (NULL, 1);
+    }
 
   if (optimize > 0)
     rest_of_handle_if_conversion (decl, insns);
@@ -4228,6 +4263,9 @@ process_options (void)
   if (flag_unit_at_a_time && ! lang_hooks.callgraph.expand_function)
     flag_unit_at_a_time = 0;
 
+  if (flag_value_profile_transformations)
+    flag_profile_values = 1;
+
   /* Warn about options that are not supported on this machine.  */
 #ifndef INSN_SCHEDULING
   if (flag_schedule_insns || flag_schedule_insns_after_reload)
diff --git a/gcc/value-prof.c b/gcc/value-prof.c
index 5dca281..3924fa7 100644
--- a/gcc/value-prof.c
+++ b/gcc/value-prof.c
@@ -32,6 +32,7 @@ Software Foundation, 59 Temple Place - Suite 330, Boston, MA
 #include "insn-config.h"
 #include "recog.h"
 #include "optabs.h"
+#include "regs.h"
 
 /* In this file value profile based optimizations will be placed (none are
    here just now, but they are hopefully coming soon).
@@ -49,7 +50,17 @@ Software Foundation, 59 Temple Place - Suite 330, Boston, MA
    -- the expression that is profiled
    -- list of counters starting from the first one.  */
 
+static void insn_divmod_values_to_profile (rtx, unsigned *,
+					   struct histogram_value **);
 static void insn_values_to_profile (rtx, unsigned *, struct histogram_value **);
+static rtx gen_divmod_fixed_value (enum machine_mode, enum rtx_code, rtx, rtx,
+				   rtx, gcov_type);
+static rtx gen_mod_pow2 (enum machine_mode, enum rtx_code, rtx, rtx, rtx);
+static rtx gen_mod_subtract (enum machine_mode, enum rtx_code, rtx, rtx, rtx,
+			     int);
+static bool divmod_fixed_value_transform (rtx insn);
+static bool mod_pow2_value_transform (rtx);
+static bool mod_subtract_transform (rtx);
 
 /* Release the list of VALUES of length N_VALUES for that we want to measure
    histograms.  */
@@ -60,13 +71,106 @@ free_profiled_values (unsigned n_values ATTRIBUTE_UNUSED,
   free (values);
 }
 
+/* Find values inside INSN for that we want to measure histograms for
+   division/modulo optimization.  */
+static void
+insn_divmod_values_to_profile (rtx insn, unsigned *n_values,
+			       struct histogram_value **values)
+{
+  rtx set, set_src, op1, op2;
+  enum machine_mode mode;
+
+  if (!INSN_P (insn))
+    return;
+
+  set = single_set (insn);
+  if (!set)
+    return;
+
+  mode = GET_MODE (SET_DEST (set));
+  if (!INTEGRAL_MODE_P (mode))
+    return;
+
+  set_src = SET_SRC (set);
+  switch (GET_CODE (set_src))
+    {
+    case DIV:
+    case MOD:
+    case UDIV:
+    case UMOD:
+      op1 = XEXP (set_src, 0);
+      op2 = XEXP (set_src, 1);
+      if (side_effects_p (op2))
+	return;
+
+      /* Check for a special case where the divisor is power of 2.  */
+      if ((GET_CODE (set_src) == UMOD) && !CONSTANT_P (op2))
+	{
+	  *values = xrealloc (*values,
+			      (*n_values + 1)
+				* sizeof (struct histogram_value));
+	  (*values)[*n_values].value = op2;
+	  (*values)[*n_values].seq = NULL_RTX;
+	  (*values)[*n_values].mode = mode;
+	  (*values)[*n_values].insn = insn;
+	  (*values)[*n_values].type = HIST_TYPE_POW2;
+	  (*values)[*n_values].hdata.pow2.may_be_other = 1;
+	  (*n_values)++;
+	}
+
+      /* Check whether the divisor is not in fact a constant.  */
+      if (!CONSTANT_P (op2))
+	{
+	  *values = xrealloc (*values,
+			      (*n_values + 1)
+				* sizeof (struct histogram_value));
+	  (*values)[*n_values].value = op2;
+	  (*values)[*n_values].mode = mode;
+	  (*values)[*n_values].seq = NULL_RTX;
+	  (*values)[*n_values].insn = insn;
+	  (*values)[*n_values].type = HIST_TYPE_SINGLE_VALUE;
+	  (*n_values)++;
+	}
+
+      /* For mod, check whether it is not often a noop (or replacable by
+	 a few subtractions).  */
+      if (GET_CODE (set_src) == UMOD && !side_effects_p (op1))
+	{
+	  rtx tmp;
+
+	  *values = xrealloc (*values,
+			      (*n_values + 1)
+				* sizeof (struct histogram_value));
+	  start_sequence ();
+	  tmp = simplify_gen_binary (DIV, mode, copy_rtx (op1), copy_rtx (op2));
+	  (*values)[*n_values].value = force_operand (tmp, NULL_RTX);
+	  (*values)[*n_values].seq = get_insns ();
+	  end_sequence ();
+	  (*values)[*n_values].mode = mode;
+	  (*values)[*n_values].insn = insn;
+	  (*values)[*n_values].type = HIST_TYPE_INTERVAL;
+	  (*values)[*n_values].hdata.intvl.int_start = 0;
+	  (*values)[*n_values].hdata.intvl.steps = 2;
+	  (*values)[*n_values].hdata.intvl.may_be_less = 1;
+	  (*values)[*n_values].hdata.intvl.may_be_more = 1;
+	  (*n_values)++;
+	}
+      return;
+
+    default:
+      return;
+    }
+}
+
 /* Find values inside INSN for that we want to measure histograms and adds
    them to list VALUES (increasing the record of its length in N_VALUES).  */
 static void
-insn_values_to_profile (rtx insn ATTRIBUTE_UNUSED,
-			unsigned *n_values ATTRIBUTE_UNUSED,
-			struct histogram_value **values ATTRIBUTE_UNUSED)
+insn_values_to_profile (rtx insn,
+			unsigned *n_values,
+			struct histogram_value **values)
 {
+  if (flag_value_profile_transformations)
+    insn_divmod_values_to_profile (insn, n_values, values);
 }
 
 /* Find list of values for that we want to measure histograms.  */
@@ -86,21 +190,40 @@ find_values_to_profile (unsigned *n_values, struct histogram_value **values)
       switch ((*values)[i].type)
 	{
 	case HIST_TYPE_INTERVAL:
+	  if (rtl_dump_file)
+	    fprintf (rtl_dump_file,
+		     "Interval counter for insn %d, range %d -- %d.\n",
+		     INSN_UID ((*values)[i].insn),
+		     (*values)[i].hdata.intvl.int_start,
+		     ((*values)[i].hdata.intvl.int_start
+		      + (*values)[i].hdata.intvl.steps - 1));
 	  (*values)[i].n_counters = (*values)[i].hdata.intvl.steps +
 		  ((*values)[i].hdata.intvl.may_be_less ? 1 : 0) +
 		  ((*values)[i].hdata.intvl.may_be_more ? 1 : 0);
 	  break;
 
 	case HIST_TYPE_POW2:
+	  if (rtl_dump_file)
+	    fprintf (rtl_dump_file,
+		     "Pow2 counter for insn %d.\n",
+		     INSN_UID ((*values)[i].insn));
 	  (*values)[i].n_counters = GET_MODE_BITSIZE ((*values)[i].mode) +
 		  ((*values)[i].hdata.pow2.may_be_other ? 1 : 0);
 	  break;
 
 	case HIST_TYPE_SINGLE_VALUE:
+	  if (rtl_dump_file)
+	    fprintf (rtl_dump_file,
+		     "Single value counter for insn %d.\n",
+		     INSN_UID ((*values)[i].insn));
 	  (*values)[i].n_counters = 3;
 	  break;
 
 	case HIST_TYPE_CONST_DELTA:
+	  if (rtl_dump_file)
+	    fprintf (rtl_dump_file,
+		     "Constant delta counter for insn %d.\n",
+		     INSN_UID ((*values)[i].insn));
 	  (*values)[i].n_counters = 4;
 	  break;
 
@@ -109,3 +232,477 @@ find_values_to_profile (unsigned *n_values, struct histogram_value **values)
 	}
     }
 }
+
+/* Main entry point.  Finds REG_VALUE_PROFILE notes from profiler and uses
+   them to identify and exploit properties of values that are hard to analyze
+   statically.
+
+   We do following transformations:
+
+   1)
+
+   x = a / b;
+
+   where b is almost always a constant N is transformed to
+
+   if (b == N)
+     x = a / N;
+   else
+     x = a / b;
+
+   Analogically with %
+
+   2)
+
+   x = a % b
+
+   where b is almost always a power of 2 and the division is unsigned
+   TODO -- handle signed case as well
+
+   if ((b & (b - 1)) == 0)
+     x = a & (b - 1);
+   else
+     x = x % b;
+
+   Note that when b = 0, no error will occur and x = a; this is correct,
+   as result of such operation is undefined.
+
+   3)
+
+   x = a % b
+
+   where a is almost always less then b and the division is unsigned
+   TODO -- handle signed case as well
+
+   x = a;
+   if (x >= b)
+     x %= b;
+
+   4)
+
+   x = a % b
+
+   where a is almost always less then 2 * b and the division is unsigned
+   TODO -- handle signed case as well
+
+   x = a;
+   if (x >= b)
+     x -= b;
+   if (x >= b)
+     x %= b;
+
+   It would be possible to continue analogically for K * b for other small
+   K's, but it is probably not useful.
+
+   TODO:
+
+   There are other useful cases that could be handled by a similar mechanism,
+   for example:
+   
+   for (i = 0; i < n; i++)
+     ...
+   
+   transform to (for constant N):
+   
+   if (n == N)
+     for (i = 0; i < N; i++)
+       ...
+   else
+     for (i = 0; i < n; i++)
+       ...
+   making unroller happy.  Since this may grow the code significantly,
+   we would have to be very careful here.  */
+
+bool
+value_profile_transformations ()
+{
+  rtx insn, next;
+  int changed = false;
+
+  for (insn = get_insns (); insn; insn = next)
+    {
+      next = NEXT_INSN (insn);
+
+      if (!INSN_P (insn))
+	continue;
+
+      /* Scan for insn carrying a histogram.  */
+      if (!find_reg_note (insn, REG_VALUE_PROFILE, 0))
+	continue;
+
+      /* Ignore cold areas -- we are growing a code.  */
+      if (!maybe_hot_bb_p (BLOCK_FOR_INSN (insn)))
+	continue;
+
+      if (rtl_dump_file)
+	{
+	  fprintf (rtl_dump_file, "Trying transformations on insn %d\n",
+		   INSN_UID (insn));
+	  print_rtl_single (rtl_dump_file, insn);
+	}
+
+      /* Transformations:  */
+      if (flag_value_profile_transformations
+	  && (mod_subtract_transform (insn)
+	      || divmod_fixed_value_transform (insn)
+	      || mod_pow2_value_transform (insn)))
+	changed = true;
+    }
+
+  if (changed)
+    {
+      commit_edge_insertions ();
+      allocate_reg_info (max_reg_num (), FALSE, FALSE);
+    }
+
+  return changed;
+}
+
+/* Generate code for transformation 1 (with MODE and OPERATION, operands OP1
+   and OP2 whose value is expected to be VALUE and result TARGET).  */
+static rtx
+gen_divmod_fixed_value (enum machine_mode mode, enum rtx_code operation,
+			rtx target, rtx op1, rtx op2, gcov_type value)
+{
+  rtx tmp, tmp1;
+  rtx neq_label = gen_label_rtx ();
+  rtx end_label = gen_label_rtx ();
+  rtx sequence;
+
+  start_sequence ();
+  
+  if (!REG_P (op2))
+    {
+      tmp = gen_reg_rtx (mode);
+      emit_move_insn (tmp, copy_rtx (op2));
+    }
+  else
+    tmp = op2;
+
+  do_compare_rtx_and_jump (tmp, GEN_INT (value), NE, 0, mode, NULL_RTX,
+			   NULL_RTX, neq_label);
+  tmp1 = simplify_gen_binary (operation, mode, copy_rtx (op1), GEN_INT (value));
+  tmp1 = force_operand (tmp1, target);
+  if (tmp1 != target)
+    emit_move_insn (copy_rtx (target), copy_rtx (tmp1));
+
+  emit_jump_insn (gen_jump (end_label));
+  emit_barrier ();
+
+  emit_label (neq_label);
+  tmp1 = simplify_gen_binary (operation, mode, copy_rtx (op1), copy_rtx (tmp));
+  tmp1 = force_operand (tmp1, target);
+  if (tmp1 != target)
+    emit_move_insn (copy_rtx (target), copy_rtx (tmp1));
+  
+  emit_label (end_label);
+
+  sequence = get_insns ();
+  end_sequence ();
+  rebuild_jump_labels (sequence);
+  return sequence;
+}
+
+/* Do transform 1) on INSN if applicable.  */
+static bool
+divmod_fixed_value_transform (rtx insn)
+{
+  rtx set, set_src, set_dest, op1, op2, value, histogram;
+  enum rtx_code code;
+  enum machine_mode mode;
+  gcov_type val, count, all;
+  edge e;
+
+  set = single_set (insn);
+  if (!set)
+    return false;
+
+  set_src = SET_SRC (set);
+  set_dest = SET_DEST (set);
+  code = GET_CODE (set_src);
+  mode = GET_MODE (set_dest);
+  
+  if (code != DIV && code != MOD && code != UDIV && code != UMOD)
+    return false;
+  op1 = XEXP (set_src, false);
+  op2 = XEXP (set_src, 1);
+
+  for (histogram = REG_NOTES (insn);
+       histogram;
+       histogram = XEXP (histogram, 1))
+    if (REG_NOTE_KIND (histogram) == REG_VALUE_PROFILE
+	&& XEXP (XEXP (histogram, 0), 0) == GEN_INT (HIST_TYPE_SINGLE_VALUE))
+      break;
+
+  if (!histogram)
+    return false;
+
+  histogram = XEXP (XEXP (histogram, 0), 1);
+  value = XEXP (histogram, 0);
+  histogram = XEXP (histogram, 1);
+  val = INTVAL (XEXP (histogram, 0));
+  histogram = XEXP (histogram, 1);
+  count = INTVAL (XEXP (histogram, 0));
+  histogram = XEXP (histogram, 1);
+  all = INTVAL (XEXP (histogram, 0));
+
+  /* We requiere that count is at least half of all; this means
+     that for the transformation to fire the value must be constant
+     at least 50% of time (and 75% gives the garantee of usage).  */
+  if (!rtx_equal_p (op2, value) || 2 * count < all)
+    return false;
+
+  if (rtl_dump_file)
+    fprintf (rtl_dump_file, "Div/mod by constant transformation on insn %d\n",
+	     INSN_UID (insn));
+
+  e = split_block (BLOCK_FOR_INSN (insn), PREV_INSN (insn));
+  delete_insn (insn);
+  
+  insert_insn_on_edge (
+	gen_divmod_fixed_value (mode, code, set_dest, op1, op2, val), e);
+
+  return true;
+}
+
+/* Generate code for transformation 2 (with MODE and OPERATION, operands OP1
+   and OP2 and result TARGET).  */
+static rtx
+gen_mod_pow2 (enum machine_mode mode, enum rtx_code operation, rtx target,
+	      rtx op1, rtx op2)
+{
+  rtx tmp, tmp1, tmp2, tmp3;
+  rtx neq_label = gen_label_rtx ();
+  rtx end_label = gen_label_rtx ();
+  rtx sequence;
+
+  start_sequence ();
+  
+  if (!REG_P (op2))
+    {
+      tmp = gen_reg_rtx (mode);
+      emit_move_insn (tmp, copy_rtx (op2));
+    }
+  else
+    tmp = op2;
+
+  tmp1 = expand_simple_binop (mode, PLUS, tmp, constm1_rtx, NULL_RTX,
+			      0, OPTAB_WIDEN);
+  tmp2 = expand_simple_binop (mode, AND, tmp, tmp1, NULL_RTX,
+			      0, OPTAB_WIDEN);
+  do_compare_rtx_and_jump (tmp2, const0_rtx, NE, 0, mode, NULL_RTX,
+			   NULL_RTX, neq_label);
+  tmp3 = expand_simple_binop (mode, AND, op1, tmp1, target,
+			      0, OPTAB_WIDEN);
+  if (tmp3 != target)
+    emit_move_insn (copy_rtx (target), tmp3);
+  emit_jump_insn (gen_jump (end_label));
+  emit_barrier ();
+
+  emit_label (neq_label);
+  tmp1 = simplify_gen_binary (operation, mode, copy_rtx (op1), copy_rtx (tmp));
+  tmp1 = force_operand (tmp1, target);
+  if (tmp1 != target)
+    emit_move_insn (target, tmp1);
+  
+  emit_label (end_label);
+
+  sequence = get_insns ();
+  end_sequence ();
+  rebuild_jump_labels (sequence);
+  return sequence;
+}
+
+/* Do transform 2) on INSN if applicable.  */
+static bool
+mod_pow2_value_transform (rtx insn)
+{
+  rtx set, set_src, set_dest, op1, op2, value, histogram;
+  enum rtx_code code;
+  enum machine_mode mode;
+  gcov_type wrong_values, count;
+  edge e;
+  int i;
+
+  set = single_set (insn);
+  if (!set)
+    return false;
+
+  set_src = SET_SRC (set);
+  set_dest = SET_DEST (set);
+  code = GET_CODE (set_src);
+  mode = GET_MODE (set_dest);
+  
+  if (code != UMOD)
+    return false;
+  op1 = XEXP (set_src, 0);
+  op2 = XEXP (set_src, 1);
+
+  for (histogram = REG_NOTES (insn);
+       histogram;
+       histogram = XEXP (histogram, 1))
+    if (REG_NOTE_KIND (histogram) == REG_VALUE_PROFILE
+	&& XEXP (XEXP (histogram, 0), 0) == GEN_INT (HIST_TYPE_POW2))
+      break;
+
+  if (!histogram)
+    return false;
+
+  histogram = XEXP (XEXP (histogram, 0), 1);
+  value = XEXP (histogram, 0);
+  histogram = XEXP (histogram, 1);
+  wrong_values =INTVAL (XEXP (histogram, 0));
+  histogram = XEXP (histogram, 1);
+
+  count = 0;
+  for (i = 0; i < GET_MODE_BITSIZE (mode); i++)
+    {
+      count += INTVAL (XEXP (histogram, 0));
+      histogram = XEXP (histogram, 1);
+    }
+
+  if (!rtx_equal_p (op2, value))
+    return false;
+
+  /* We require that we hit a power of two at least half of all evaluations.  */
+  if (count < wrong_values)
+    return false;
+
+  if (rtl_dump_file)
+    fprintf (rtl_dump_file, "Mod power of 2 transformation on insn %d\n",
+	     INSN_UID (insn));
+
+  e = split_block (BLOCK_FOR_INSN (insn), PREV_INSN (insn));
+  delete_insn (insn);
+  
+  insert_insn_on_edge (
+	gen_mod_pow2 (mode, code, set_dest, op1, op2), e);
+
+  return true;
+}
+
+/* Generate code for transformations 3 and 4 (with MODE and OPERATION,
+   operands OP1 and OP2, result TARGET and at most SUB subtractions).  */
+static rtx
+gen_mod_subtract (enum machine_mode mode, enum rtx_code operation,
+		  rtx target, rtx op1, rtx op2, int sub)
+{
+  rtx tmp, tmp1;
+  rtx end_label = gen_label_rtx ();
+  rtx sequence;
+  int i;
+
+  start_sequence ();
+  
+  if (!REG_P (op2))
+    {
+      tmp = gen_reg_rtx (mode);
+      emit_move_insn (tmp, copy_rtx (op2));
+    }
+  else
+    tmp = op2;
+
+  emit_move_insn (target, copy_rtx (op1));
+  do_compare_rtx_and_jump (target, tmp, LTU, 0, mode, NULL_RTX,
+			   NULL_RTX, end_label);
+  
+
+  for (i = 0; i < sub; i++)
+    {
+      tmp1 = expand_simple_binop (mode, MINUS, target, tmp, target,
+	    			  0, OPTAB_WIDEN);
+      if (tmp1 != target)
+	emit_move_insn (target, tmp1);
+      do_compare_rtx_and_jump (target, tmp, LTU, 0, mode, NULL_RTX,
+    			       NULL_RTX, end_label);
+    }
+
+  tmp1 = simplify_gen_binary (operation, mode, copy_rtx (target), copy_rtx (tmp));
+  tmp1 = force_operand (tmp1, target);
+  if (tmp1 != target)
+    emit_move_insn (target, tmp1);
+  
+  emit_label (end_label);
+
+  sequence = get_insns ();
+  end_sequence ();
+  rebuild_jump_labels (sequence);
+  return sequence;
+}
+
+/* Do transforms 3) and 4) on INSN if applicable.  */
+static bool
+mod_subtract_transform (rtx insn)
+{
+  rtx set, set_src, set_dest, op1, op2, value, histogram;
+  enum rtx_code code;
+  enum machine_mode mode;
+  gcov_type wrong_values, counts[2], count, all;
+  edge e;
+  int i;
+
+  set = single_set (insn);
+  if (!set)
+    return false;
+
+  set_src = SET_SRC (set);
+  set_dest = SET_DEST (set);
+  code = GET_CODE (set_src);
+  mode = GET_MODE (set_dest);
+  
+  if (code != UMOD)
+    return false;
+  op1 = XEXP (set_src, 0);
+  op2 = XEXP (set_src, 1);
+
+  for (histogram = REG_NOTES (insn);
+       histogram;
+       histogram = XEXP (histogram, 1))
+    if (REG_NOTE_KIND (histogram) == REG_VALUE_PROFILE
+	&& XEXP (XEXP (histogram, 0), 0) == GEN_INT (HIST_TYPE_INTERVAL))
+      break;
+
+  if (!histogram)
+    return false;
+
+  histogram = XEXP (XEXP (histogram, 0), 1);
+  value = XEXP (histogram, 0);
+  histogram = XEXP (histogram, 1);
+
+  all = 0;
+  for (i = 0; i < 2; i++)
+    {
+      counts[i] = INTVAL (XEXP (histogram, 0));
+      all += counts[i];
+      histogram = XEXP (histogram, 1);
+    }
+  wrong_values = INTVAL (XEXP (histogram, 0));
+  histogram = XEXP (histogram, 1);
+  wrong_values += INTVAL (XEXP (histogram, 0));
+  all += wrong_values;
+
+  /* We require that we use just subtractions in at least 50% of all
+     evaluations.  */
+  count = 0;
+  for (i = 0; i < 2; i++)
+    {
+      count += counts[i];
+      if (count * 2 >= all)
+	break;
+    }
+  
+  if (i == 2)
+    return false;
+
+  if (rtl_dump_file)
+    fprintf (rtl_dump_file, "Mod subtract transformation on insn %d\n",
+	     INSN_UID (insn));
+
+  e = split_block (BLOCK_FOR_INSN (insn), PREV_INSN (insn));
+  delete_insn (insn);
+  
+  insert_insn_on_edge (
+	gen_mod_subtract (mode, code, set_dest, op1, op2, i), e);
+
+  return true;
+}
diff --git a/gcc/value-prof.h b/gcc/value-prof.h
index 233895e..afbeb91 100644
--- a/gcc/value-prof.h
+++ b/gcc/value-prof.h
@@ -61,3 +61,4 @@ struct histogram_value
 
 extern void find_values_to_profile (unsigned *, struct histogram_value **);
 extern void free_profiled_values (unsigned, struct histogram_value *);
+extern bool value_profile_transformations (void);