Committed patch implementing live range shrinkage.

Index: common.opt
===================================================================
--- common.opt	(revision 204380)
+++ common.opt	(working copy)
@@ -1738,6 +1738,10 @@  fregmove
 Common Ignore
 Does nothing. Preserved for backward compatibility.
 
+flive-range-shrinkage
+Common Report Var(flag_live_range_shrinkage) Init(0) Optimization
+Relief of register pressure through live range shrinkage
+
 frename-registers
 Common Report Var(flag_rename_registers) Init(2) Optimization
 Perform a register renaming optimization pass
Index: doc/invoke.texi
===================================================================
--- doc/invoke.texi	(revision 204216)
+++ doc/invoke.texi	(working copy)
@@ -378,7 +378,7 @@  Objective-C and Objective-C++ Dialects}.
 -fira-region=@var{region} -fira-hoist-pressure @gol
 -fira-loop-pressure -fno-ira-share-save-slots @gol
 -fno-ira-share-spill-slots -fira-verbose=@var{n} @gol
--fivopts -fkeep-inline-functions -fkeep-static-consts @gol
+-fivopts -fkeep-inline-functions -fkeep-static-consts -flive-range-shrinkage @gol
 -floop-block -floop-interchange -floop-strip-mine -floop-nest-optimize @gol
 -floop-parallelize-all -flto -flto-compression-level @gol
 -flto-partition=@var{alg} -flto-report -flto-report-wpa -fmerge-all-constants @gol
@@ -7257,6 +7257,12 @@  registers after writing to their lower 3
 
 Enabled for x86 at levels @option{-O2}, @option{-O3}.
 
+@item -flive-range-shrinkage
+@opindex flive-range-shrinkage
+Attempt to decrease register pressure through register live range
+shrinkage.  This is helpful for fast processors with small or moderate
+size register sets.
+
 @item -fira-algorithm=@var{algorithm}
 Use the specified coloring algorithm for the integrated register
 allocator.  The @var{algorithm} argument can be @samp{priority}, which
Index: haifa-sched.c
===================================================================
--- haifa-sched.c	(revision 204380)
+++ haifa-sched.c	(working copy)
@@ -150,6 +150,24 @@  along with GCC; see the file COPYING3.
 
 #ifdef INSN_SCHEDULING
 
+/* True if we do register pressure relief through live-range
+   shrinkage.  */
+static bool live_range_shrinkage_p;
+
+/* Switch on live range shrinkage.  */
+void
+initialize_live_range_shrinkage (void)
+{
+  live_range_shrinkage_p = true;
+}
+
+/* Switch off live range shrinkage.  */
+void
+finish_live_range_shrinkage (void)
+{
+  live_range_shrinkage_p = false;
+}
+
 /* issue_rate is the number of insns that can be scheduled in the same
    machine cycle.  It can be defined in the config/mach/mach.h file,
    otherwise we set it to 1.  */
@@ -2519,7 +2537,7 @@  rank_for_schedule (const void *x, const
   rtx tmp = *(const rtx *) y;
   rtx tmp2 = *(const rtx *) x;
   int tmp_class, tmp2_class;
-  int val, priority_val, info_val;
+  int val, priority_val, info_val, diff;
 
   if (MAY_HAVE_DEBUG_INSNS)
     {
@@ -2532,6 +2550,22 @@  rank_for_schedule (const void *x, const
 	return INSN_LUID (tmp) - INSN_LUID (tmp2);
     }
 
+  if (live_range_shrinkage_p)
+    {
+      /* Don't use SCHED_PRESSURE_MODEL -- it results in much worse
+	 code.  */
+      gcc_assert (sched_pressure == SCHED_PRESSURE_WEIGHTED);
+      if ((INSN_REG_PRESSURE_EXCESS_COST_CHANGE (tmp) < 0
+	   || INSN_REG_PRESSURE_EXCESS_COST_CHANGE (tmp2) < 0)
+	  && (diff = (INSN_REG_PRESSURE_EXCESS_COST_CHANGE (tmp)
+		      - INSN_REG_PRESSURE_EXCESS_COST_CHANGE (tmp2))) != 0)
+	return diff;
+      /* Sort by INSN_LUID (original insn order), so that we make the
+	 sort stable.  This minimizes instruction movement, thus
+	 minimizing sched's effect on debugging and cross-jumping.  */
+      return INSN_LUID (tmp) - INSN_LUID (tmp2);
+    }
+
   /* The insn in a schedule group should be issued the first.  */
   if (flag_sched_group_heuristic &&
       SCHED_GROUP_P (tmp) != SCHED_GROUP_P (tmp2))
@@ -2542,8 +2576,6 @@  rank_for_schedule (const void *x, const
 
   if (sched_pressure != SCHED_PRESSURE_NONE)
     {
-      int diff;
-
       /* Prefer insn whose scheduling results in the smallest register
 	 pressure excess.  */
       if ((diff = (INSN_REG_PRESSURE_EXCESS_COST_CHANGE (tmp)
@@ -3731,7 +3763,10 @@  schedule_insn (rtx insn)
 	{
 	  fputc (':', sched_dump);
 	  for (i = 0; i < ira_pressure_classes_num; i++)
-	    fprintf (sched_dump, "%s%+d(%d)",
+	    fprintf (sched_dump, "%s%s%+d(%d)",
+		     scheduled_insns.length () > 1
+		     && INSN_LUID (insn)
+		     < INSN_LUID (scheduled_insns[scheduled_insns.length () - 2]) ? "@" : "",
 		     reg_class_names[ira_pressure_classes[i]],
 		     pressure_info[i].set_increase, pressure_info[i].change);
 	}
@@ -6578,9 +6613,11 @@  sched_init (void)
   if (targetm.sched.dispatch (NULL_RTX, IS_DISPATCH_ON))
     targetm.sched.dispatch_do (NULL_RTX, DISPATCH_INIT);
 
-  if (flag_sched_pressure
-      && !reload_completed
-      && common_sched_info->sched_pass_id == SCHED_RGN_PASS)
+  if (live_range_shrinkage_p)
+    sched_pressure = SCHED_PRESSURE_WEIGHTED;
+  else if (flag_sched_pressure
+	   && !reload_completed
+	   && common_sched_info->sched_pass_id == SCHED_RGN_PASS)
     sched_pressure = ((enum sched_pressure_algorithm)
 		      PARAM_VALUE (PARAM_SCHED_PRESSURE_ALGORITHM));
   else
Index: ira.c
===================================================================
--- ira.c	(revision 204380)
+++ ira.c	(working copy)
@@ -3794,11 +3794,12 @@  update_equiv_regs (void)
 
 		  if (! reg_equiv[regno].replace
 		      || reg_equiv[regno].loop_depth < loop_depth
-		      /* There is no sense to move insns if we did
-			 register pressure-sensitive scheduling was
-			 done because it will not improve allocation
-			 but worsen insn schedule with a big
-			 probability.  */
+		      /* There is no sense to move insns if live range
+			 shrinkage or register pressure-sensitive
+			 scheduling were done because it will not
+			 improve allocation but worsen insn schedule
+			 with a big probability.  */
+		      || flag_live_range_shrinkage
 		      || (flag_sched_pressure && flag_schedule_insns))
 		    continue;
 
Index: passes.def
===================================================================
--- passes.def	(revision 204380)
+++ passes.def	(working copy)
@@ -358,6 +358,7 @@  along with GCC; see the file COPYING3.
       NEXT_PASS (pass_mode_switching);
       NEXT_PASS (pass_match_asm_constraints);
       NEXT_PASS (pass_sms);
+      NEXT_PASS (pass_live_range_shrinkage);
       NEXT_PASS (pass_sched);
       NEXT_PASS (pass_ira);
       NEXT_PASS (pass_reload);
Index: sched-deps.c
===================================================================
--- sched-deps.c	(revision 204380)
+++ sched-deps.c	(working copy)
@@ -1938,8 +1938,8 @@  create_insn_reg_use (int regno, rtx insn
   return use;
 }
 
-/* Allocate and return reg_set_data structure for REGNO and INSN.  */
-static struct reg_set_data *
+/* Allocate reg_set_data structure for REGNO and INSN.  */
+static void
 create_insn_reg_set (int regno, rtx insn)
 {
   struct reg_set_data *set;
@@ -1949,7 +1949,6 @@  create_insn_reg_set (int regno, rtx insn
   set->insn = insn;
   set->next_insn_set = INSN_REG_SET_LIST (insn);
   INSN_REG_SET_LIST (insn) = set;
-  return set;
 }
 
 /* Set up insn register uses for INSN and dependency context DEPS.  */
Index: sched-int.h
===================================================================
--- sched-int.h	(revision 204380)
+++ sched-int.h	(working copy)
@@ -1333,6 +1333,8 @@  extern void debug_ds (ds_t);
 
 
 /* Functions in haifa-sched.c.  */
+extern void initialize_live_range_shrinkage (void);
+extern void finish_live_range_shrinkage (void);
 extern void sched_init_region_reg_pressure_info (void);
 extern int haifa_classify_insn (const_rtx);
 extern void get_ebb_head_tail (basic_block, basic_block, rtx *, rtx *);
Index: sched-rgn.c
===================================================================
--- sched-rgn.c	(revision 204380)
+++ sched-rgn.c	(working copy)
@@ -3565,6 +3565,33 @@  advance_target_bb (basic_block bb, rtx i
 #endif
 
 static bool
+gate_handle_live_range_shrinkage (void)
+{
+#ifdef INSN_SCHEDULING
+  return flag_live_range_shrinkage;
+#else
+  return 0;
+#endif
+}
+
+/* Run instruction scheduler.  */
+static unsigned int
+rest_of_handle_live_range_shrinkage (void)
+{
+#ifdef INSN_SCHEDULING
+  int saved;
+
+  initialize_live_range_shrinkage ();
+  saved = flag_schedule_interblock;
+  flag_schedule_interblock = false;
+  schedule_insns ();
+  flag_schedule_interblock = saved;
+  finish_live_range_shrinkage ();
+#endif
+  return 0;
+}
+
+static bool
 gate_handle_sched (void)
 {
 #ifdef INSN_SCHEDULING
@@ -3621,6 +3648,45 @@  rest_of_handle_sched2 (void)
 }
 
 namespace {
+
+const pass_data pass_data_live_range_shrinkage =
+{
+  RTL_PASS, /* type */
+  "lr_shrinkage", /* name */
+  OPTGROUP_NONE, /* optinfo_flags */
+  true, /* has_gate */
+  true, /* has_execute */
+  TV_LIVE_RANGE_SHRINKAGE, /* tv_id */
+  0, /* properties_required */
+  0, /* properties_provided */
+  0, /* properties_destroyed */
+  0, /* todo_flags_start */
+  ( TODO_df_finish | TODO_verify_rtl_sharing
+    | TODO_verify_flow ), /* todo_flags_finish */
+};
+
+class pass_live_range_shrinkage : public rtl_opt_pass
+{
+public:
+  pass_live_range_shrinkage(gcc::context *ctxt)
+    : rtl_opt_pass(pass_data_live_range_shrinkage, ctxt)
+  {}
+
+  /* opt_pass methods: */
+  bool gate () { return gate_handle_live_range_shrinkage (); }
+  unsigned int execute () { return rest_of_handle_live_range_shrinkage (); }
+
+}; // class pass_live_range_shrinkage
+
+} // anon namespace
+
+rtl_opt_pass *
+make_pass_live_range_shrinkage (gcc::context *ctxt)
+{
+  return new pass_live_range_shrinkage (ctxt);
+}
+
+namespace {
 
 const pass_data pass_data_sched =
 {
Index: timevar.def
===================================================================
--- timevar.def	(revision 204380)
+++ timevar.def	(working copy)
@@ -223,6 +223,7 @@  DEFTIMEVAR (TV_COMBINE               , "
 DEFTIMEVAR (TV_IFCVT		     , "if-conversion")
 DEFTIMEVAR (TV_MODE_SWITCH           , "mode switching")
 DEFTIMEVAR (TV_SMS		     , "sms modulo scheduling")
+DEFTIMEVAR (TV_LIVE_RANGE_SHRINKAGE  , "live range shrinkage")
 DEFTIMEVAR (TV_SCHED                 , "scheduling")
 DEFTIMEVAR (TV_IRA		     , "integrated RA")
 DEFTIMEVAR (TV_LRA		     , "LRA non-specific")
Index: tree-pass.h
===================================================================
--- tree-pass.h	(revision 204380)
+++ tree-pass.h	(working copy)
@@ -530,6 +530,7 @@  extern rtl_opt_pass *make_pass_lower_sub
 extern rtl_opt_pass *make_pass_mode_switching (gcc::context *ctxt);
 extern rtl_opt_pass *make_pass_sms (gcc::context *ctxt);
 extern rtl_opt_pass *make_pass_sched (gcc::context *ctxt);
+extern rtl_opt_pass *make_pass_live_range_shrinkage (gcc::context *ctxt);
 extern rtl_opt_pass *make_pass_ira (gcc::context *ctxt);
 extern rtl_opt_pass *make_pass_reload (gcc::context *ctxt);
 extern rtl_opt_pass *make_pass_clean_state (gcc::context *ctxt);