2003-06-18 Stephen Clarke <stephen.clarke@superh.com>

            J"orn Rennecke <joern.rennecke@superh.com>

	* bt-load.c: New file.
	* Makefile.in (OBJS): Include bt-load.o
	(bt-load.o): Add dependencies.
	* flags.h (flag_branch_target_load_optimize): Declare.
	(flag_branch_target_load_optimize2): Likewise.
	* hooks.c (hook_reg_class_void_no_regs): New function.
	(hook_bool_bool_false): Likewise.
	* hooks.h (hook_reg_class_void_no_regs, hook_bool_bool_false): Declare.
	* rtl.h (branch_target_load_optimize): Declare.
	* target-def.h (TARGET_BRANCH_TARGET_REGISTER_CLASS): Define.
	(TARGET_BRANCH_TARGET_REGISTER_CALLEE_SAVED): Likewise.
	(TARGET_INITIALIZER): Include these.
	* target.h (struct gcc_target): Add branch_target_register_class
	and branch_target_register_callee_saved members.
	* toplev.c (enum dump_file_index): Add DFI_branch_target_load
	(dump_file) Add "tars" entry.
	(flag_branch_target_load_optimize): New variable.
	(flag_branch_target_load_optimize2): Likewise.
	(lang_independent_options): Add entries for new options.
	(rest_of_compilation): Call branch_target_load_optimize.
	* doc/tm.texi (TARGET_BRANCH_TARGET_REGISTER_CLASS): Document.
	(TARGET_BRANCH_TARGET_REGISTER_CALLEE_SAVED): Likewise.
	* doc/invoke.texi: Document -fbranch-target-load-optimize and
	-fbranch-target-load-optimize2.
	* rtl.h (epilogue_completed): Declare.
	* recog.c (epilogue_completed): New variable.
	* toplev.c (rest_of_compilation): Set it.
	* flow.c (mark_regs_live_at_end): Use it.
	* config/ia64/ia64.c (ia64_output_mi_thunk): Set it.
	* config/rs6000/rs6000.c (rs6000_output_mi_thunk): Likewise.
	* config/sh/sh.c (sh_output_mi_thunk): Likewise.
	* config/sparc/sparc.c (sparc_output_mi_thunk): Likewise.

	* sh.c (shmedia_space_reserved_for_target_registers): New variable.
	(sh_target_reg_class): New function.
	(sh_optimize_target_register_callee_saved): Likwise.
	(shmedia_target_regs_stack_space): Likewise.
	(shmedia_reserve_space_for_target_registers_p): Likewise.
	(shmedia_target_regs_stack_adjust): Likewise.
	(TARGET_BRANCH_TARGET_REGISTER_CLASS): Override.
	(TARGET_BRANCH_TARGET_REGISTER_CALLEE_SAVED): Likewise.
	(calc_live_regs): If flag_branch_target_load_optimize2 and
	TARGET_SAVE_ALL_TARGET_REGS is enabled, and we have space reserved
	for target registers, make sure that we save all target registers.
	(sh_expand_prologue, sh_expand_epilogue): Take target register
	optimizations into account.  Collapse stack adjustments if that
	is beneficial.
	(initial_elimination_offset): Reserve space for target registers
	if necessary.
	* sh.h (SAVE_ALL_TR_BIT, TARGET_SAVE_ALL_TARGET_REGS): Define.
	(OPTIMIZATION_OPTIONS): Enable flag_branch_target_load_optimize.


git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/trunk@68165 138bc75d-0d04-0410-961f-82ee72b054a4

1 files changed, 1380 insertions, 0 deletions

diff --git a/gcc/bt-load.c b/gcc/bt-load.c
new file mode 100644
index 00000000000..dd2dcb2b16b
--- /dev/null
+++ b/gcc/bt-load.c
@@ -0,0 +1,1380 @@
+/* Perform branch target register load optimizations.
+   Copyright (C) 2001, 2002, 2003 Free Software Foundation, Inc.
+
+This file is part of GCC.
+
+GCC is free software; you can redistribute it and/or modify it under
+the terms of the GNU General Public License as published by the Free
+Software Foundation; either version 2, or (at your option) any later
+version.
+
+GCC is distributed in the hope that it will be useful, but WITHOUT ANY
+WARRANTY; without even the implied warranty of MERCHANTABILITY or
+FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+for more details.
+
+You should have received a copy of the GNU General Public License
+along with GCC; see the file COPYING.  If not, write to the Free
+Software Foundation, 59 Temple Place - Suite 330, Boston, MA
+02111-1307, USA.  */
+
+#include "config.h"
+#include "system.h"
+#include "coretypes.h"
+#include "tm.h"
+#include "bitmap.h"
+#include "sbitmap.h"
+#include "rtl.h"
+#include "hard-reg-set.h"
+#include "basic-block.h"
+#include "regs.h"
+#include "obstack.h"
+#include "fibheap.h"
+#include "output.h"
+#include "target.h"
+#include "expr.h"
+#include "flags.h"
+#include "insn-attr.h"
+#include "function.h"
+
+/* Target register optimizations - these are performed after reload.  */
+
+typedef struct btr_def_group_s
+{
+  struct btr_def_group_s *next;
+  rtx src;
+  struct btr_def_s *members;
+} *btr_def_group;
+
+typedef struct btr_user_s
+{
+  struct btr_user_s *next;
+  basic_block bb;
+  int luid;
+  rtx insn;
+  /* If INSN has a single use of a single branch register, then
+     USE points to it within INSN.  If there is more than
+     one branch register use, or the use is in some way ambiguous,
+     then USE is NULL.  */
+  rtx use;
+  int n_reaching_defs;
+  int first_reaching_def;
+  char other_use_this_block;
+} *btr_user;
+
+/* btr_def structs appear on three lists:
+     1. A list of all btr_def structures (head is
+	ALL_BTR_DEFS, linked by the NEXT field).
+     2. A list of branch reg definitions per basic block (head is
+	BB_BTR_DEFS[i], linked by the NEXT_THIS_BB field).
+     3. A list of all branch reg definitions belonging to the same
+	group (head is in a BTR_DEF_GROUP struct, linked by
+	NEXT_THIS_GROUP field).  */
+
+typedef struct btr_def_s
+{
+  struct btr_def_s *next_this_bb;
+  struct btr_def_s *next_this_group;
+  basic_block bb;
+  int luid;
+  rtx insn;
+  int btr;
+  int cost;
+  /* For a branch register setting insn that has a constant
+     source (i.e. a label), group links together all the
+     insns with the same source.  For other branch register
+     setting insns, group is NULL.  */
+  btr_def_group group;
+  btr_user uses;
+  /* If this def has a reaching use which is not a simple use
+     in a branch instruction, then has_ambiguous_use will be true,
+     and we will not attempt to migrate this definition.       */
+  char has_ambiguous_use;
+  /* live_range is an approximation to the true live range for this
+     def/use web, because it records the set of blocks that contain
+     the live range.  There could be other live ranges for the same
+     branch register in that set of blocks, either in the block
+     containing the def (before the def), or in a block containing
+     a use (after the use).  If there are such other live ranges, then
+     other_btr_uses_before_def or other_btr_uses_after_use must be set true
+     as appropriate. */
+  char other_btr_uses_before_def;
+  char other_btr_uses_after_use;
+  bitmap live_range;
+} *btr_def;
+
+static int issue_rate;
+
+static int basic_block_freq (basic_block);
+static int insn_sets_btr_p (rtx, int, int *);
+static rtx *find_btr_use (rtx);
+static int btr_referenced_p (rtx, rtx *);
+static int find_btr_reference (rtx *, void *);
+static void find_btr_def_group (btr_def_group *, btr_def);
+static btr_def add_btr_def (fibheap_t, basic_block, int, rtx,
+			    unsigned int, int, btr_def_group *);
+static btr_user new_btr_user (basic_block, int, rtx);
+static void dump_hard_reg_set (HARD_REG_SET);
+static void dump_btrs_live (int);
+static void note_other_use_this_block (unsigned int, btr_user);
+static void compute_defs_uses_and_gen (fibheap_t, btr_def *,btr_user *,
+				       sbitmap *, sbitmap *, HARD_REG_SET *);
+static void compute_kill (sbitmap *, sbitmap *, HARD_REG_SET *);
+static void compute_out (sbitmap *bb_out, sbitmap *, sbitmap *, int);
+static void link_btr_uses (btr_def *, btr_user *, sbitmap *, sbitmap *, int);
+static void build_btr_def_use_webs (fibheap_t);
+static int block_at_edge_of_live_range_p (int, btr_def);
+static void clear_btr_from_live_range (btr_def def);
+static void add_btr_to_live_range (btr_def);
+static void augment_live_range (bitmap, HARD_REG_SET *, basic_block,
+				basic_block);
+static int choose_btr (HARD_REG_SET);
+static void combine_btr_defs (btr_def, HARD_REG_SET *);
+static void btr_def_live_range (btr_def, HARD_REG_SET *);
+static void move_btr_def (basic_block, int, btr_def, bitmap, HARD_REG_SET *);
+static int migrate_btr_def (btr_def, int);
+static void migrate_btr_defs (enum reg_class, int);
+static int can_move_up (basic_block, rtx, int);
+static void note_btr_set (rtx, rtx, void *);
+
+/* The following code performs code motion of target load instructions
+   (instructions that set branch target registers), to move them
+   forward away from the branch instructions and out of loops (or,
+   more generally, from a more frequently executed place to a less
+   frequently executed place).
+   Moving target load instructions further in front of the branch
+   instruction that uses the target register value means that the hardware
+   has a better chance of preloading the instructions at the branch
+   target by the time the branch is reached.  This avoids bubbles
+   when a taken branch needs to flush out the pipeline.
+   Moving target load instructions out of loops means they are executed
+   less frequently.  */
+
+/* An obstack to hold the def-use web data structures built up for
+   migrating branch target load instructions.  */
+static struct obstack migrate_btrl_obstack;
+
+/* Basic block dominator information used when migrating PT instructions */
+static dominance_info dom;
+
+/* Array indexed by basic block number, giving the set of registers
+   live in that block.  */
+static HARD_REG_SET *btrs_live;
+
+/* Set of all target registers that we are willing to allocate.  */
+static HARD_REG_SET all_btrs;
+
+/* Provide lower and upper bounds for target register numbers, so that
+   we don't need to search through all the hard registers all the time.  */
+static int first_btr, last_btr;
+
+
+
+/* Return an estimate of the frequency of execution of block bb.
+   If we have a profiling count available, we could use it here.  */
+static int
+basic_block_freq (basic_block bb)
+{
+  return bb->frequency;
+}
+
+static rtx *btr_reference_found;
+
+/* A subroutine of btr_referenced_p, called through for_each_rtx.
+   PREG is a pointer to an rtx that is to be excluded from the
+   traversal.  If we find a reference to a target register anywhere
+   else, return 1, and put a pointer to it into btr_reference_found.  */
+static int
+find_btr_reference (rtx *px, void *preg)
+{
+  rtx x;
+  int regno, i;
+
+  if (px == preg)
+    return -1;
+  x = *px;
+  if (GET_CODE (x) != REG)
+    return 0;
+  regno = REGNO (x);
+  for (i = HARD_REGNO_NREGS (regno, GET_MODE (x)) - 1; i >= 0; i--)
+    if (TEST_HARD_REG_BIT (all_btrs, regno+i))
+      {
+	btr_reference_found = px;
+	return 1;
+      }
+  return -1;
+}
+
+/* Return nonzero if X references (sets or reads) any branch target register.
+   If EXCLUDEP is set, disregard any references within the rtx pointed to
+   by it.  If returning nonzero, also set btr_reference_found as above.  */
+static int
+btr_referenced_p (rtx x, rtx *excludep)
+{
+  return for_each_rtx (&x, find_btr_reference, excludep);
+}
+
+/* Return true if insn is an instruction that sets a target register.
+   if CHECK_CONST is true, only return true if the source is constant.
+   If such a set is found and REGNO is nonzero, assign the register number
+   of the destination register to *REGNO.  */
+static int
+insn_sets_btr_p (rtx insn, int check_const, int *regno)
+{
+  rtx set;
+
+  if (GET_CODE (insn) == INSN
+      && (set = single_set (insn)))
+    {
+      rtx dest = SET_DEST (set);
+      rtx src = SET_SRC (set);
+
+      if (GET_CODE (dest) == SUBREG)
+	dest = XEXP (dest, 0);
+
+      if (GET_CODE (dest) == REG
+	  && TEST_HARD_REG_BIT (all_btrs, REGNO (dest)))
+	{
+	  if (btr_referenced_p (src, NULL))
+	    abort();
+	  if (!check_const || CONSTANT_P (src))
+	    {
+	      if (regno)
+		*regno = REGNO (dest);
+	      return 1;
+	    }
+	}
+    }
+  return 0;
+}
+
+/* Find and return a use of a target register within an instruction INSN. */
+static rtx *
+find_btr_use (rtx insn)
+{
+  return btr_referenced_p (insn, NULL) ? btr_reference_found : NULL;
+}
+
+/* Find the group that the target register definition DEF belongs
+   to in the list starting with *ALL_BTR_DEF_GROUPS.  If no such
+   group exists, create one.  Add def to the group.  */
+static void
+find_btr_def_group (btr_def_group *all_btr_def_groups, btr_def def)
+{
+  if (insn_sets_btr_p (def->insn, 1, NULL))
+    {
+      btr_def_group this_group;
+      rtx def_src = SET_SRC (single_set (def->insn));
+
+      /* ?? This linear search is an efficiency concern, particularly
+	 as the search will almost always fail to find a match.  */
+      for (this_group = *all_btr_def_groups;
+	   this_group != NULL;
+	   this_group = this_group->next)
+	if (rtx_equal_p (def_src, this_group->src))
+	  break;
+
+      if (!this_group)
+	{
+	  this_group = (btr_def_group)
+	    obstack_alloc (&migrate_btrl_obstack,
+			   sizeof (struct btr_def_group_s));
+	  this_group->src = def_src;
+	  this_group->members = NULL;
+	  this_group->next = *all_btr_def_groups;
+	  *all_btr_def_groups = this_group;
+	}
+      def->group = this_group;
+      def->next_this_group = this_group->members;
+      this_group->members = def;
+    }
+  else
+    def->group = NULL;
+}
+
+/* Create a new target register definition structure, for a definition in
+   block BB, instruction INSN, and insert it into ALL_BTR_DEFS.  Return
+   the new definition.  */
+static btr_def
+add_btr_def (fibheap_t all_btr_defs, basic_block bb, int insn_luid, rtx insn,
+	     unsigned int dest_reg, int other_btr_uses_before_def,
+	     btr_def_group *all_btr_def_groups)
+{
+  btr_def this = (btr_def)
+    obstack_alloc (&migrate_btrl_obstack, sizeof (struct btr_def_s));
+  this->bb = bb;
+  this->luid = insn_luid;
+  this->insn = insn;
+  this->btr = dest_reg;
+  this->cost = basic_block_freq (bb);
+  this->has_ambiguous_use = 0;
+  this->other_btr_uses_before_def = other_btr_uses_before_def;
+  this->other_btr_uses_after_use = 0;
+  this->next_this_bb = NULL;
+  this->next_this_group = NULL;
+  this->uses = NULL;
+  this->live_range = NULL;
+  find_btr_def_group (all_btr_def_groups, this);
+
+  fibheap_insert (all_btr_defs, -this->cost, this);
+
+  if (rtl_dump_file)
+    fprintf (rtl_dump_file,
+      "Found target reg definition: sets %u { bb %d, insn %d }%s priority %d\n",
+      dest_reg, bb->index, INSN_UID (insn), (this->group ? "" : ":not const"),
+      this->cost);
+
+  return this;
+}
+
+/* Create a new target register user structure, for a use in block BB,
+   instruction INSN.  Return the new user.  */
+static btr_user
+new_btr_user (basic_block bb, int insn_luid, rtx insn)
+{
+  /* This instruction reads target registers.  We need
+     to decide whether we can replace all target register
+     uses easily.
+   */
+  rtx *usep = find_btr_use (PATTERN (insn));
+  rtx use;
+  btr_user user = NULL;
+
+  if (usep)
+    {
+      int unambiguous_single_use;
+
+      /* We want to ensure that USE is the only use of a target
+	 register in INSN, so that we know that to rewrite INSN to use
+	 a different target register, all we have to do is replace USE.  */
+      unambiguous_single_use = !btr_referenced_p (PATTERN (insn), usep);
+      if (!unambiguous_single_use)
+	usep = NULL;
+    }
+  use = usep ? *usep : NULL_RTX;
+  user = (btr_user)
+    obstack_alloc (&migrate_btrl_obstack, sizeof (struct btr_user_s));
+  user->bb = bb;
+  user->luid = insn_luid;
+  user->insn = insn;
+  user->use = use;
+  user->other_use_this_block = 0;
+  user->next = NULL;
+  user->n_reaching_defs = 0;
+  user->first_reaching_def = -1;
+
+  if (rtl_dump_file)
+    {
+      fprintf (rtl_dump_file, "Uses target reg: { bb %d, insn %d }",
+	       bb->index, INSN_UID (insn));
+
+      if (user->use)
+	fprintf (rtl_dump_file, ": unambiguous use of reg %d\n",
+		 REGNO (user->use));
+    }
+
+  return user;
+}
+
+/* Write the contents of S to the dump file. */
+static void
+dump_hard_reg_set (HARD_REG_SET s)
+{
+  int reg;
+  for (reg = 0; reg < FIRST_PSEUDO_REGISTER; reg++)
+    if (TEST_HARD_REG_BIT (s, reg))
+      fprintf (rtl_dump_file, " %d", reg);
+}
+
+/* Write the set of target regs live in block BB to the dump file. */
+static void
+dump_btrs_live (int bb)
+{
+  fprintf (rtl_dump_file, "BB%d live:", bb);
+  dump_hard_reg_set (btrs_live[bb]);
+  fprintf (rtl_dump_file, "\n");
+}
+
+/* REGNO is the number of a branch target register that is being used or
+   set.  USERS_THIS_BB is a list of preceding branch target register users;
+   If any of them use the same register, set their other_use_this_block
+   flag.  */
+static void
+note_other_use_this_block (unsigned int regno, btr_user users_this_bb)
+{
+  btr_user user;
+
+  for (user = users_this_bb; user != NULL; user = user->next)
+    if (user->use && REGNO (user->use) == regno)
+      user->other_use_this_block = 1;
+}
+
+typedef struct {
+  btr_user users_this_bb;
+  HARD_REG_SET btrs_written_in_block;
+  HARD_REG_SET btrs_live_in_block;
+  sbitmap bb_gen;
+  sbitmap *btr_defset;
+} defs_uses_info;
+
+/* Called via note_stores or directly to register stores into /
+   clobbers of a branch target register DEST that are not recognized as
+   straightforward definitions.  DATA points to information about the
+   current basic block that needs updating.   */
+static void
+note_btr_set (rtx dest, rtx set ATTRIBUTE_UNUSED, void *data)
+{
+  defs_uses_info *info = data;
+  int regno, end_regno;
+
+  if (GET_CODE (dest) != REG)
+    return;
+  regno = REGNO (dest);
+  end_regno = regno + HARD_REGNO_NREGS (regno, GET_MODE (dest));
+  for (; regno < end_regno; regno++)
+    if (TEST_HARD_REG_BIT (all_btrs, regno))
+      {
+	note_other_use_this_block (regno, info->users_this_bb);
+	SET_HARD_REG_BIT (info->btrs_written_in_block, regno);
+	SET_HARD_REG_BIT (info->btrs_live_in_block, regno);
+	sbitmap_difference (info->bb_gen, info->bb_gen,
+			    info->btr_defset[regno - first_btr]);
+      }
+}
+
+static void
+compute_defs_uses_and_gen (fibheap_t all_btr_defs, btr_def *def_array,
+			   btr_user *use_array, sbitmap *btr_defset,
+			   sbitmap *bb_gen, HARD_REG_SET *btrs_written)
+{
+  /* Scan the code building up the set of all defs and all uses.
+     For each target register, build the set of defs of that register.
+     For each block, calculate the set of target registers
+     written in that block.
+     Also calculate the set of btrs ever live in that block.
+  */
+  int i;
+  int insn_luid = 0;
+  btr_def_group all_btr_def_groups = NULL;
+  defs_uses_info info;
+
+  sbitmap_vector_zero (bb_gen, n_basic_blocks);
+  for (i = 0; i < n_basic_blocks; i++)
+    {
+      basic_block bb = BASIC_BLOCK (i);
+      int reg;
+      btr_def defs_this_bb = NULL;
+      rtx insn;
+      rtx last;
+
+      info.users_this_bb = NULL;
+      info.bb_gen = bb_gen[i];
+      info.btr_defset = btr_defset;
+
+      CLEAR_HARD_REG_SET (info.btrs_live_in_block);
+      CLEAR_HARD_REG_SET (info.btrs_written_in_block);
+      for (reg = first_btr; reg <= last_btr; reg++)
+	if (TEST_HARD_REG_BIT (all_btrs, reg)
+	    && REGNO_REG_SET_P (bb->global_live_at_start, reg))
+	  SET_HARD_REG_BIT (info.btrs_live_in_block, reg);
+
+      for (insn = bb->head, last = NEXT_INSN (bb->end);
+	   insn != last;
+	   insn = NEXT_INSN (insn), insn_luid++)
+	{
+	  if (INSN_P (insn))
+	    {
+	      int regno;
+	      int insn_uid = INSN_UID (insn);
+
+	      if (insn_sets_btr_p (insn, 0, &regno))
+		{
+		  btr_def def = add_btr_def (
+		      all_btr_defs, bb, insn_luid, insn, regno,
+		      TEST_HARD_REG_BIT (info.btrs_live_in_block, regno),
+		      &all_btr_def_groups);
+
+		  def_array[insn_uid] = def;
+		  SET_HARD_REG_BIT (info.btrs_written_in_block, regno);
+		  SET_HARD_REG_BIT (info.btrs_live_in_block, regno);
+		  sbitmap_difference (bb_gen[i], bb_gen[i],
+				      btr_defset[regno - first_btr]);
+		  SET_BIT (bb_gen[i], insn_uid);
+		  def->next_this_bb = defs_this_bb;
+		  defs_this_bb = def;
+		  SET_BIT (btr_defset[regno - first_btr], insn_uid);
+		  note_other_use_this_block (regno, info.users_this_bb);
+		}
+	      else
+		{
+		  if (btr_referenced_p (PATTERN (insn), NULL))
+		    {
+		      btr_user user = new_btr_user (bb, insn_luid, insn);
+
+		      use_array[insn_uid] = user;
+		      if (user->use)
+			SET_HARD_REG_BIT (info.btrs_live_in_block,
+					  REGNO (user->use));
+		      else
+			{
+			  int reg;
+			  for (reg = first_btr; reg <= last_btr; reg++)
+			    if (TEST_HARD_REG_BIT (all_btrs, reg)
+				&& refers_to_regno_p (reg, reg + 1, user->insn,
+						      NULL))
+			      {
+				note_other_use_this_block (reg,
+							   info.users_this_bb);
+				SET_HARD_REG_BIT (info.btrs_live_in_block, reg);
+			      }
+			  note_stores (PATTERN (insn), note_btr_set, &info);
+			}
+		      user->next = info.users_this_bb;
+		      info.users_this_bb = user;
+		    }
+		  if (GET_CODE (insn) == CALL_INSN)
+		    {
+		      HARD_REG_SET *clobbered = &call_used_reg_set;
+		      HARD_REG_SET call_saved;
+		      rtx pat = PATTERN (insn);
+		      int i;
+
+		      /* Check for sibcall.  */
+		      if (GET_CODE (pat) == PARALLEL)
+			for (i = XVECLEN (pat, 0) - 1; i >= 0; i--)
+			  if (GET_CODE (XVECEXP (pat, 0, i)) == RETURN)
+			    {
+			      COMPL_HARD_REG_SET (call_saved,
+						  call_used_reg_set);
+			      clobbered = &call_saved;
+			    }
+			      
+		      for (regno = first_btr; regno <= last_btr; regno++)
+			if (TEST_HARD_REG_BIT (*clobbered, regno))
+			  note_btr_set (regno_reg_rtx[regno], NULL_RTX, &info);
+		    }
+		}
+	    }
+	}
+
+      COPY_HARD_REG_SET (btrs_live[i], info.btrs_live_in_block);
+      COPY_HARD_REG_SET (btrs_written[i], info.btrs_written_in_block);
+      if (rtl_dump_file)
+	dump_btrs_live(i);
+    }
+}
+
+static void
+compute_kill (sbitmap *bb_kill, sbitmap *btr_defset,
+	      HARD_REG_SET *btrs_written)
+{
+  int i;
+  int regno;
+
+  /* For each basic block, form the set BB_KILL - the set
+     of definitions that the block kills. */
+  sbitmap_vector_zero (bb_kill, n_basic_blocks);
+  for (i = 0; i < n_basic_blocks; i++)
+    {
+      for (regno = first_btr; regno <= last_btr; regno++)
+	if (TEST_HARD_REG_BIT (all_btrs, regno)
+	    && TEST_HARD_REG_BIT (btrs_written[i], regno))
+	  sbitmap_a_or_b (bb_kill[i], bb_kill[i],
+			  btr_defset[regno - first_btr]);
+    }
+}
+
+static void
+compute_out (sbitmap *bb_out, sbitmap *bb_gen, sbitmap *bb_kill, int max_uid)
+{
+  /* Perform iterative dataflow:
+      Initially, for all blocks, BB_OUT = BB_GEN.
+      For each block,
+	BB_IN  = union over predecessors of BB_OUT(pred)
+	BB_OUT = (BB_IN - BB_KILL) + BB_GEN
+     Iterate until the bb_out sets stop growing.   */
+  int i;
+  int changed;
+  sbitmap bb_in = sbitmap_alloc (max_uid);
+
+  for (i = 0; i < n_basic_blocks; i++)
+    sbitmap_copy (bb_out[i], bb_gen[i]);
+
+  changed = 1;
+  while (changed)
+    {
+      changed = 0;
+      for (i = 0; i < n_basic_blocks; i++)
+	{
+	  sbitmap_union_of_preds (bb_in, bb_out, i);
+	  changed |= sbitmap_union_of_diff_cg (bb_out[i], bb_gen[i],
+					       bb_in, bb_kill[i]);
+	}
+    }
+  sbitmap_free (bb_in);
+}
+
+static void
+link_btr_uses (btr_def *def_array, btr_user *use_array, sbitmap *bb_out,
+	       sbitmap *btr_defset, int max_uid)
+{
+  int i;
+  sbitmap reaching_defs = sbitmap_alloc (max_uid);
+
+  /* Link uses to the uses lists of all of their reaching defs.
+     Count up the number of reaching defs of each use. */
+  for (i = 0; i < n_basic_blocks; i++)
+    {
+      basic_block bb = BASIC_BLOCK (i);
+      rtx insn;
+      rtx last;
+
+      sbitmap_union_of_preds (reaching_defs, bb_out, i);
+      for (insn = bb->head, last = NEXT_INSN (bb->end);
+	   insn != last;
+	   insn = NEXT_INSN (insn))
+	{
+	  if (INSN_P (insn))
+	    {
+	      int insn_uid = INSN_UID (insn);
+
+	      btr_def def   = def_array[insn_uid];
+	      btr_user user = use_array[insn_uid];
+	      if (def != NULL)
+		{
+		  /* Remove all reaching defs of regno except
+		     for this one. */
+		  sbitmap_difference (reaching_defs, reaching_defs,
+				      btr_defset[def->btr - first_btr]);
+		  SET_BIT(reaching_defs, insn_uid);
+		}
+
+	      if (user != NULL)
+		{
+		  /* Find all the reaching defs for this use */
+		  sbitmap reaching_defs_of_reg = sbitmap_alloc(max_uid);
+		  int uid;
+
+		  if (user->use)
+		    sbitmap_a_and_b (
+		      reaching_defs_of_reg,
+		      reaching_defs,
+		      btr_defset[REGNO (user->use) - first_btr]);
+		  else
+		    {
+		      int reg;
+
+		      sbitmap_zero (reaching_defs_of_reg);
+		      for (reg = first_btr; reg <= last_btr; reg++)
+			if (TEST_HARD_REG_BIT (all_btrs, reg)
+			    && refers_to_regno_p (reg, reg + 1, user->insn,
+						  NULL))
+			  sbitmap_a_or_b_and_c (reaching_defs_of_reg,
+			    reaching_defs_of_reg,
+			    reaching_defs,
+			    btr_defset[reg - first_btr]);
+		    }
+		  EXECUTE_IF_SET_IN_SBITMAP (reaching_defs_of_reg, 0, uid,
+		    {
+		      btr_def def = def_array[uid];
+
+		      /* We now know that def reaches user */
+
+		      if (rtl_dump_file)
+			fprintf (rtl_dump_file,
+			  "Def in insn %d reaches use in insn %d\n",
+			  uid, insn_uid);
+
+		      user->n_reaching_defs++;
+		      if (!user->use)
+			def->has_ambiguous_use = 1;
+		      if (user->first_reaching_def != -1)
+			{ /* There is more than one reaching def.  This is
+			     a rare case, so just give up on this def/use
+			     web when it occurs. */
+			  def->has_ambiguous_use = 1;
+			  def_array[user->first_reaching_def]
+			    ->has_ambiguous_use = 1;
+			  if (rtl_dump_file)
+			    fprintf (rtl_dump_file,
+				     "(use %d has multiple reaching defs)\n",
+				     insn_uid);
+			}
+		      else
+			user->first_reaching_def = uid;
+		      if (user->other_use_this_block)
+			def->other_btr_uses_after_use = 1;
+		      user->next = def->uses;
+		      def->uses = user;
+		    });
+		  sbitmap_free (reaching_defs_of_reg);
+		}
+
+	      if (GET_CODE (insn) == CALL_INSN)
+		{
+		  int regno;
+
+		  for (regno = first_btr; regno <= last_btr; regno++)
+		    if (TEST_HARD_REG_BIT (all_btrs, regno)
+			&& TEST_HARD_REG_BIT (call_used_reg_set, regno))
+		      sbitmap_difference (reaching_defs, reaching_defs,
+					  btr_defset[regno - first_btr]);
+		}
+	    }
+	}
+    }
+  sbitmap_free (reaching_defs);
+}
+
+static void
+build_btr_def_use_webs (fibheap_t all_btr_defs)
+{
+  const int max_uid = get_max_uid ();
+  btr_def  *def_array   = xcalloc (max_uid, sizeof (btr_def));
+  btr_user *use_array   = xcalloc (max_uid, sizeof (btr_user));
+  sbitmap *btr_defset   = sbitmap_vector_alloc (
+			   (last_btr - first_btr) + 1, max_uid);
+  sbitmap *bb_gen      = sbitmap_vector_alloc (n_basic_blocks, max_uid);
+  HARD_REG_SET *btrs_written = (HARD_REG_SET *) xcalloc (
+			       n_basic_blocks, sizeof (HARD_REG_SET));
+  sbitmap *bb_kill;
+  sbitmap *bb_out;
+
+  sbitmap_vector_zero (btr_defset, (last_btr - first_btr) + 1);
+
+  compute_defs_uses_and_gen (all_btr_defs, def_array, use_array, btr_defset,
+			     bb_gen, btrs_written);
+
+  bb_kill = sbitmap_vector_alloc (n_basic_blocks, max_uid);
+  compute_kill (bb_kill, btr_defset, btrs_written);
+  free (btrs_written);
+
+  bb_out = sbitmap_vector_alloc (n_basic_blocks, max_uid);
+  compute_out (bb_out, bb_gen, bb_kill, max_uid);
+
+  sbitmap_vector_free (bb_gen);
+  sbitmap_vector_free (bb_kill);
+
+  link_btr_uses (def_array, use_array, bb_out, btr_defset, max_uid);
+
+  sbitmap_vector_free (bb_out);
+  sbitmap_vector_free (btr_defset);
+  free (use_array);
+  free (def_array);
+}
+
+/* Return true if basic block BB contains the start or end of the
+   live range of the definition DEF, AND there are other live
+   ranges of the same target register that include BB.  */
+static int
+block_at_edge_of_live_range_p (int bb, btr_def def)
+{
+  if (def->other_btr_uses_before_def && BASIC_BLOCK (bb) == def->bb)
+    return 1;
+  else if (def->other_btr_uses_after_use)
+    {
+      btr_user user;
+      for (user = def->uses; user != NULL; user = user->next)
+	if (BASIC_BLOCK (bb) == user->bb)
+	  return 1;
+    }
+  return 0;
+}
+
+/* We are removing the def/use web DEF.  The target register
+   used in this web is therefore no longer live in the live range
+   of this web, so remove it from the live set of all basic blocks
+   in the live range of the web.
+   Blocks at the boundary of the live range may contain other live
+   ranges for the same target register, so we have to be careful
+   to remove the target register from the live set of these blocks
+   only if they do not contain other live ranges for the same register. */
+static void
+clear_btr_from_live_range (btr_def def)
+{
+  int bb;
+
+  EXECUTE_IF_SET_IN_BITMAP
+    (def->live_range, 0, bb,
+     {
+       if ((!def->other_btr_uses_before_def
+	     && !def->other_btr_uses_after_use)
+	   || !block_at_edge_of_live_range_p (bb, def))
+	 {
+	   CLEAR_HARD_REG_BIT (btrs_live[bb], def->btr);
+	   if (rtl_dump_file)
+	     dump_btrs_live (bb);
+	 }
+     });
+}
+
+
+/* We are adding the def/use web DEF.  Add the target register used
+   in this web to the live set of all of the basic blocks that contain
+   the live range of the web.  */
+static void
+add_btr_to_live_range (btr_def def)
+{
+  int bb;
+  EXECUTE_IF_SET_IN_BITMAP
+    (def->live_range, 0, bb,
+     {
+       SET_HARD_REG_BIT (btrs_live[bb], def->btr);
+       if (rtl_dump_file)
+	 dump_btrs_live (bb);
+     });
+}
+
+/* Update a live range to contain the basic block NEW_BLOCK, and all
+   blocks on paths between the existing live range and NEW_BLOCK.
+   HEAD is a block contained in the existing live range that dominates
+   all other blocks in the existing live range.
+   Also add to the set BTRS_LIVE_IN_RANGE all target registers that
+   are live in the blocks that we add to the live range.
+   It is a precondition that either NEW_BLOCK dominates HEAD,or
+   HEAD dom NEW_BLOCK.  This is used to speed up the
+   implementation of this function.  */
+static void
+augment_live_range (bitmap live_range, HARD_REG_SET *btrs_live_in_range,
+		    basic_block head_bb, basic_block new_bb)
+{
+  basic_block *worklist, *tos;
+
+  tos = worklist =
+    (basic_block *) xmalloc (sizeof (basic_block) * (n_basic_blocks + 1));
+
+  if (dominated_by_p (dom, new_bb, head_bb))
+    *tos++ = new_bb;
+  else if (dominated_by_p (dom, head_bb, new_bb))
+    {
+      edge e;
+      int new_block = new_bb->index;
+
+      bitmap_set_bit (live_range, new_block);
+      IOR_HARD_REG_SET (*btrs_live_in_range, btrs_live[new_block]);
+      if (rtl_dump_file)
+	{
+	  fprintf (rtl_dump_file,
+		   "Adding block %d to live range\n", new_block);
+	  fprintf (rtl_dump_file,"Now live btrs are ");
+	  dump_hard_reg_set (*btrs_live_in_range);
+	  fprintf (rtl_dump_file, "\n");
+	}
+      for (e = head_bb->pred; e; e = e->pred_next)
+	*tos++ = e->src;
+    }
+  else
+    abort();
+
+  while (tos != worklist)
+    {
+      basic_block bb = *--tos;
+      if (!bitmap_bit_p (live_range, bb->index))
+	{
+	  edge e;
+
+	  bitmap_set_bit (live_range, bb->index);
+	  IOR_HARD_REG_SET (*btrs_live_in_range,
+	    btrs_live[bb->index]);
+	  if (rtl_dump_file)
+	    {
+	      fprintf (rtl_dump_file,
+		"Adding block %d to live range\n", bb->index);
+	      fprintf (rtl_dump_file,"Now live btrs are ");
+	      dump_hard_reg_set (*btrs_live_in_range);
+	      fprintf (rtl_dump_file, "\n");
+	    }
+
+	  for (e = bb->pred; e != NULL; e = e->pred_next)
+	    {
+	      basic_block pred = e->src;
+	      if (!bitmap_bit_p (live_range, pred->index))
+		*tos++ = pred;
+	    }
+	}
+    }
+
+  free (worklist);
+}
+
+/*  Return the most desirable target register that is not in
+    the set USED_BTRS.  */
+static int
+choose_btr (HARD_REG_SET used_btrs)
+{
+  int i;
+  GO_IF_HARD_REG_SUBSET (all_btrs, used_btrs, give_up);
+
+  for (i = 0; i < FIRST_PSEUDO_REGISTER; i++)
+    {
+#ifdef REG_ALLOC_ORDER
+      int regno = reg_alloc_order[i];
+#else
+      int regno = i;
+#endif
+      if (TEST_HARD_REG_BIT (all_btrs, regno)
+	  && !TEST_HARD_REG_BIT (used_btrs, regno))
+	return regno;
+    }
+give_up:
+  return -1;
+}
+
+/* Calculate the set of basic blocks that contain the live range of
+   the def/use web DEF.
+   Also calculate the set of target registers that are live at time
+   in this live range, but ignore the live range represented by DEF
+   when calculating this set.  */
+static void
+btr_def_live_range (btr_def def, HARD_REG_SET *btrs_live_in_range)
+{
+  if (!def->live_range)
+    {
+      btr_user user;
+
+      def->live_range = BITMAP_XMALLOC ();
+
+      bitmap_set_bit (def->live_range, def->bb->index);
+      COPY_HARD_REG_SET (*btrs_live_in_range, btrs_live[def->bb->index]);
+
+      for (user = def->uses; user != NULL; user = user->next)
+	augment_live_range (def->live_range, btrs_live_in_range,
+			    def->bb, user->bb);
+    }
+  else
+    {
+      /* def->live_range is accurate, but we need to recompute
+	 the set of target registers live over it, because migration
+	 of other PT instructions may have affected it.
+      */
+      int bb;
+
+      CLEAR_HARD_REG_SET (*btrs_live_in_range);
+      EXECUTE_IF_SET_IN_BITMAP
+	(def->live_range, 0, bb,
+	 {
+	   IOR_HARD_REG_SET (*btrs_live_in_range,
+	     btrs_live[bb]);
+	 });
+    }
+  if (!def->other_btr_uses_before_def &&
+      !def->other_btr_uses_after_use)
+    CLEAR_HARD_REG_BIT (*btrs_live_in_range, def->btr);
+}
+
+/* Merge into the def/use web DEF any other def/use webs in the same
+   group that are dominated by DEF, provided that there is a target
+   register available to allocate to the merged web.  */
+static void
+combine_btr_defs (btr_def def, HARD_REG_SET *btrs_live_in_range)
+{
+  btr_def other_def;
+
+  for (other_def = def->group->members;
+       other_def != NULL;
+       other_def = other_def->next_this_group)
+    {
+      if (other_def != def
+	  && other_def->uses != NULL
+	  && ! other_def->has_ambiguous_use
+	  && dominated_by_p (dom, other_def->bb, def->bb))
+	{
+	  /* def->bb dominates the other def, so def and other_def could
+	     be combined. */
+	  /* Merge their live ranges, and get the set of
+	     target registers live over the merged range. */
+	  int btr;
+	  HARD_REG_SET combined_btrs_live;
+	  bitmap combined_live_range = BITMAP_XMALLOC ();
+	  btr_user user;
+
+	  if (other_def->live_range == NULL)
+	    {
+	      HARD_REG_SET dummy_btrs_live_in_range;
+	      btr_def_live_range (other_def, &dummy_btrs_live_in_range);
+	    }
+	  COPY_HARD_REG_SET (combined_btrs_live, *btrs_live_in_range);
+	  bitmap_copy (combined_live_range, def->live_range);
+
+	  for (user = other_def->uses; user != NULL; user = user->next)
+	    augment_live_range (combined_live_range, &combined_btrs_live,
+				def->bb, user->bb);
+
+	  btr = choose_btr (combined_btrs_live);
+	  if (btr != -1)
+	    {
+	      /* We can combine them */
+	      if (rtl_dump_file)
+		fprintf (rtl_dump_file,
+			 "Combining def in insn %d with def in insn %d\n",
+			 INSN_UID (other_def->insn), INSN_UID (def->insn));
+
+	      def->btr = btr;
+	      user = other_def->uses;
+	      while (user != NULL)
+		{
+		  btr_user next = user->next;
+
+		  user->next = def->uses;
+		  def->uses = user;
+		  user = next;
+		}
+	      /* Combining def/use webs can make target registers live
+		 after uses where they previously were not.  This means
+		 some REG_DEAD notes may no longer be correct.  We could
+		 be more precise about this if we looked at the combined
+		 live range, but here I just delete any REG_DEAD notes
+		 in case they are no longer correct. */
+	      for (user = def->uses; user != NULL; user = user->next)
+		remove_note (user->insn,
+			     find_regno_note (user->insn, REG_DEAD,
+					      REGNO (user->use)));
+	      clear_btr_from_live_range (other_def);
+	      other_def->uses = NULL;
+	      bitmap_copy (def->live_range, combined_live_range);
+	      if (other_def->other_btr_uses_after_use)
+		def->other_btr_uses_after_use = 1;
+	      COPY_HARD_REG_SET (*btrs_live_in_range, combined_btrs_live);
+
+	      /* Delete the old target register initialization */
+	      delete_insn (other_def->insn);
+
+	    }
+	  BITMAP_XFREE (combined_live_range);
+	}
+    }
+}
+
+/* Move the definition DEF from its current position to basic
+   block NEW_DEF_BB, and modify it to use branch target register BTR.
+   Delete the old defining insn, and insert a new one in NEW_DEF_BB.
+   Update all reaching uses of DEF in the RTL to use BTR.
+   If this new position means that other defs in the
+   same group can be combined with DEF then combine them.  */
+static void
+move_btr_def (basic_block new_def_bb, int btr, btr_def def, bitmap live_range,
+	     HARD_REG_SET *btrs_live_in_range)
+{
+  /* We can move the instruction.
+     Set a target register in block NEW_DEF_BB to the value
+     needed for this target register definition.
+     Replace all uses of the old target register definition by
+     uses of the new definition.  Delete the old definition. */
+  basic_block b = new_def_bb;
+  rtx insp = b->head;
+  rtx old_insn = def->insn;
+  rtx src;
+  rtx btr_rtx;
+  rtx new_insn;
+  enum machine_mode btr_mode;
+  btr_user user;
+  rtx set;
+
+  if (rtl_dump_file)
+    fprintf(rtl_dump_file, "migrating to basic block %d, using reg %d\n",
+	    new_def_bb->index, btr);
+
+  clear_btr_from_live_range (def);
+  def->btr = btr;
+  def->bb = new_def_bb;
+  def->luid = 0;
+  def->cost = basic_block_freq (new_def_bb);
+  def->other_btr_uses_before_def = 0;
+  bitmap_copy (def->live_range, live_range);
+  combine_btr_defs (def, btrs_live_in_range);
+  btr = def->btr;
+  add_btr_to_live_range (def);
+  if (GET_CODE (insp) == CODE_LABEL)
+    insp = NEXT_INSN (insp);
+  /* N.B.: insp is expected to be NOTE_INSN_BASIC_BLOCK now.  Some
+     optimizations can result in insp being both first and last insn of
+     its basic block.  */
+  /* ?? some assertions to check that insp is sensible? */
+
+  set = single_set (old_insn);
+  src = SET_SRC (set);
+  btr_mode = GET_MODE (SET_DEST (set));
+  btr_rtx = gen_rtx (REG, btr_mode, btr);
+
+  new_insn = gen_move_insn (btr_rtx, src);
+
+  /* Insert target register initialization at head of basic block. */
+  def->insn = emit_insn_after (new_insn, insp);
+
+  regs_ever_live[btr] = 1;
+
+  if (rtl_dump_file)
+    fprintf (rtl_dump_file, "New pt is insn %d, inserted after insn %d\n",
+	     INSN_UID (def->insn), INSN_UID (insp));
+
+  /* Delete the old target register initialization */
+  delete_insn (old_insn);
+
+  /* Replace each use of the old target register by a use of the new target
+     register. */
+  for (user = def->uses; user != NULL; user = user->next)
+    {
+      /* Some extra work here to ensure consistent modes, because
+	 it seems that a target register REG rtx can be given a different
+	 mode depending on the context (surely that should not be
+	 the case?). */
+      rtx replacement_rtx;
+      if (GET_MODE (user->use) == GET_MODE (btr_rtx)
+	  || GET_MODE (user->use) == VOIDmode)
+	replacement_rtx = btr_rtx;
+      else
+	replacement_rtx = gen_rtx (REG, GET_MODE (user->use), btr);
+      replace_rtx (user->insn, user->use, replacement_rtx);
+      user->use = replacement_rtx;
+    }
+}
+
+/* We anticipate intra-block scheduling to be done.  See if INSN could move
+   up within BB by N_INSNS.  */
+static int
+can_move_up (basic_block bb, rtx insn, int n_insns)
+{
+  while (insn != bb->head && n_insns > 0)
+    {
+      insn = PREV_INSN (insn);
+      /* ??? What if we have an anti-dependency that actually prevents the
+	 scheduler from doing the move?  We'd like to re-allocate the register,
+	 but not necessarily put the load into another basic block.  */
+      if (INSN_P (insn))
+	n_insns--;
+    }
+  return n_insns <= 0;
+}
+
+/* Attempt to migrate the target register definition DEF to an
+   earlier point in the flowgraph.
+
+   It is a precondition of this function that DEF is migratable:
+   i.e. it has a constant source, and all uses are unambiguous.
+
+   Only migrations that reduce the cost of DEF will be made.
+   MIN_COST is the lower bound on the cost of the DEF after migration.
+   If we migrate DEF so that its cost falls below MIN_COST,
+   then we do not attempt to migrate further.  The idea is that
+   we migrate defintions in a priority order based on their cost,
+   when the cost of this definition falls below MIN_COST, then
+   there is another definition with cost == MIN_COST which now
+   has a higher priority than this definition.
+
+   Return non-zero if there may be benefit from attempting to
+   migrate this DEF further (i.e. we have reduced the cost below
+   MIN_COST, but we may be able to reduce it further).
+   Return zero if no further migration is possible. */
+static int
+migrate_btr_def (btr_def def, int min_cost)
+{
+  bitmap live_range;
+  HARD_REG_SET btrs_live_in_range;
+  int btr_used_near_def = 0;
+  int def_basic_block_freq;
+  basic_block try;
+  int give_up = 0;
+  int def_moved = 0;
+  btr_user user;
+  int def_latency;
+
+  if (rtl_dump_file)
+    fprintf (rtl_dump_file,
+	     "Attempting to migrate pt from insn %d (cost = %d, min_cost = %d) ... ",
+	     INSN_UID (def->insn), def->cost, min_cost);
+
+  if (!def->group || def->has_ambiguous_use)
+    /* These defs are not migratable */
+    {
+      if (rtl_dump_file)
+	fprintf (rtl_dump_file, "it's not migratable\n");
+      return 0;
+    }
+
+  if (!def->uses)
+    /* We have combined this def with another in the same group, so
+       no need to consider it further.
+    */
+    {
+      if (rtl_dump_file)
+	fprintf (rtl_dump_file, "it's already combined with another pt\n");
+      return 0;
+    }
+
+  btr_def_live_range (def, &btrs_live_in_range);
+  live_range = BITMAP_XMALLOC ();
+  bitmap_copy (live_range, def->live_range);
+
+  if ((*targetm.sched.use_dfa_pipeline_interface) ())
+    def_latency = insn_default_latency (def->insn);
+  else
+    def_latency = result_ready_cost (def->insn);
+  def_latency *= issue_rate;
+
+  for (user = def->uses; user != NULL; user = user->next)
+    {
+      if (user->bb == def->bb
+	  && user->luid > def->luid
+	  && (def->luid + def_latency) > user->luid
+	  && ! can_move_up (def->bb, def->insn,
+			    (def->luid + def_latency) - user->luid))
+	{
+	  btr_used_near_def = 1;
+	  break;
+	}
+    }
+
+  def_basic_block_freq = basic_block_freq (def->bb);
+
+  for (try = get_immediate_dominator (dom, def->bb);
+       !give_up && try && try != ENTRY_BLOCK_PTR && def->cost >= min_cost;
+       try = get_immediate_dominator (dom, try))
+    {
+      /* Try to move the instruction that sets the target register into
+	 basic block TRY. */
+      int try_freq = basic_block_freq (try);
+
+      if (rtl_dump_file)
+	fprintf (rtl_dump_file, "trying block %d ...", try->index);
+
+      if (try_freq < def_basic_block_freq
+	  || (try_freq == def_basic_block_freq && btr_used_near_def))
+	{
+	  int btr;
+	  augment_live_range (live_range, &btrs_live_in_range, def->bb, try);
+	  if (rtl_dump_file)
+	    {
+	      fprintf (rtl_dump_file, "Now btrs live in range are: ");
+	      dump_hard_reg_set (btrs_live_in_range);
+	      fprintf (rtl_dump_file, "\n");
+	    }
+	  btr = choose_btr (btrs_live_in_range);
+	  if (btr != -1)
+	    {
+	      move_btr_def (try, btr, def, live_range, &btrs_live_in_range);
+	      bitmap_copy(live_range, def->live_range);
+	      btr_used_near_def = 0;
+	      def_moved = 1;
+	      def_basic_block_freq = basic_block_freq (def->bb);
+	    }
+	  else
+	    {
+	      /* There are no free target registers available to move
+		 this far forward, so give up */
+	      give_up = 1;
+	      if (rtl_dump_file)
+		fprintf (rtl_dump_file,
+			 "giving up because there are no free target registers\n");
+	    }
+
+	}
+    }
+  if (!def_moved)
+    {
+      give_up = 1;
+      if (rtl_dump_file)
+	fprintf (rtl_dump_file, "failed to move\n");
+    }
+  BITMAP_XFREE (live_range);
+  return !give_up;
+}
+
+/* Attempt to move instructions that set target registers earlier
+   in the flowgraph, away from their corresponding uses. */
+static void
+migrate_btr_defs (enum reg_class btr_class, int allow_callee_save)
+{
+  fibheap_t all_btr_defs = fibheap_new ();
+  int reg;
+
+  gcc_obstack_init (&migrate_btrl_obstack);
+  if (rtl_dump_file)
+    {
+      int i;
+
+      for (i = 0; i < n_basic_blocks; i++)
+	{
+	  basic_block bb = BASIC_BLOCK (i);
+	  fprintf(rtl_dump_file,
+	    "Basic block %d: count = %lld loop-depth = %d idom = %d\n",
+	    i, bb->count, bb->loop_depth,
+	    get_immediate_dominator (dom, bb)->index);
+	}
+    }
+
+  CLEAR_HARD_REG_SET (all_btrs);
+  for (first_btr = -1, reg = 0; reg < FIRST_PSEUDO_REGISTER; reg++)
+    if (TEST_HARD_REG_BIT (reg_class_contents[(int) btr_class], reg)
+	&& (allow_callee_save || call_used_regs[reg] || regs_ever_live[reg]))
+      {
+	SET_HARD_REG_BIT (all_btrs, reg);
+	last_btr = reg;
+	if (first_btr < 0)
+	  first_btr = reg;
+      }
+
+  btrs_live =
+    (HARD_REG_SET *) xcalloc (n_basic_blocks, sizeof (HARD_REG_SET));
+
+  build_btr_def_use_webs (all_btr_defs);
+
+  while (!fibheap_empty (all_btr_defs))
+    {
+      btr_def def =
+	(btr_def) fibheap_extract_min (all_btr_defs);
+      int min_cost = -fibheap_min_key (all_btr_defs);
+      if (migrate_btr_def (def, min_cost))
+	{
+	  fibheap_insert (all_btr_defs, -def->cost, (void *) def);
+	  if (rtl_dump_file)
+	    {
+	      fprintf (rtl_dump_file,
+		"Putting insn %d back on queue with priority %d\n",
+		INSN_UID (def->insn), def->cost);
+	    }
+	}
+      else
+	{
+	  if (def->live_range)
+	    BITMAP_XFREE (def->live_range);
+	}
+    }
+
+  free (btrs_live);
+  obstack_free (&migrate_btrl_obstack, NULL);
+  fibheap_delete (all_btr_defs);
+}
+
+void
+branch_target_load_optimize (rtx insns, bool after_prologue_epilogue_gen)
+{
+  enum reg_class class = (*targetm.branch_target_register_class) ();
+  if (class != NO_REGS)
+    {
+      /* Initialize issue_rate.  */
+      if (targetm.sched.issue_rate)
+	issue_rate = (*targetm.sched.issue_rate) ();
+      else
+	issue_rate = 1;
+
+      /* Build the CFG for migrate_btr_defs. */
+#if 1
+      /* This may or may not be needed, depending on where we
+	 run this phase. */
+      cleanup_cfg (optimize ? CLEANUP_EXPENSIVE : 0);
+#endif
+
+      life_analysis (insns, NULL, 0);
+
+      /* Dominator info is also needed for migrate_btr_def. */
+      dom = calculate_dominance_info (CDI_DOMINATORS);
+      migrate_btr_defs (class,
+		       ((*targetm.branch_target_register_callee_saved)
+			(after_prologue_epilogue_gen)));
+
+      free_dominance_info (dom);
+
+      update_life_info (NULL, UPDATE_LIFE_GLOBAL_RM_NOTES,
+			PROP_DEATH_NOTES | PROP_REG_INFO);
+    }
+}