Re: [PATCH V3 1/7] df: Add DF_LIVE_SUBREG problem

[Richard Sandiford <richard.sandiford@arm.com>]

Lehua Ding <lehua.ding@rivai.ai> writes:
> This patch adds a live_subreg problem to extend the original live_reg to
> track the liveness of subreg. We will only try to trace speudo registers
> who's mode size is a multiple of nature size and eventually a small portion
> of the inside will appear to use subreg. With live_reg problem, live_subreg
> prbolem will have the following output. full_in/out mean the entire pesudo
> live in/out, partial_in/out mean the subregs of the pesudo are live in/out,
> and range_in/out indicates which part of the pesudo is live. all_in/out is
> the union of full_in/out and partial_in/out:
>
>   bitmap_head all_in, full_in;
>   bitmap_head all_out, full_out;
>   bitmap_head partial_in;
>   bitmap_head partial_out;
>   subregs_live *range_in = NULL;
>   subregs_live *range_out = NULL;

I haven't fully processed the patch yet, sorry.  And I think I might be
about to cover things that you dealt with elsewhere.

My assumption going into this was that a subreg liveness tracker would
work as follows:

- First we would work out which registers need to have subreg tracking.
  This could be done ahead of time by iterating over regno_reg_rtx.
  The condition in need_track_subreg looks like the correct one.

  For every other register, subreg liveness degenerates to the existing
  liveness problems.  Such registers can be ignored.

- We would assign a unique identifier to each subreg that we want to track,
  with subregs for the same register being consecutive.

- There would be a mapping from pseudo registers to the first subreg
  that we want to track.  The mapping would probably just be a linear
  array, but perhaps there are times when something more compact is
  appropriate.

- The dataflow problem itself would then be very similar to the existing
  ones.  But rather than computing bitmaps with a single bit per register,
  we'd be computing bitmaps that have N bits for N-register pseudos
  (and no bits for single-register pseudos).

- There would be helper functions that consumers could use to iterate
  over a block.  E.g. for a backwards walk over a block, a consumer
  would start with the bitmap of live-out subregs.  It would then use
  these helper functions to keep the values up-to-date as it moves
  up through the block.

  That's done for normal liveness via the df_simulate_* helpers.
  But now that the codebase is C++, it might be more convenient for
  the subreg code to provide classes for walking a block.

That should be relatively compile-time-friendly, although I agree
with Vlad of course that DF does have efficiency problems.  The nature
of the way it works makes it at least O(#blocks * #regs).

Did you consider doing it that way?  Or does it not provide the
information that you need?

Thanks,
Richard

> gcc/ChangeLog:
>
> 	* Makefile.in: Add new object file.
> 	* df-problems.cc (struct df_live_subreg_problem_data):
> 	The data of the new live_subreg problem.
> 	(need_track_subreg): New function.
> 	(get_range): Ditto.
> 	(remove_subreg_range): Ditto.
> 	(add_subreg_range): Ditto.
> 	(df_live_subreg_free_bb_info): Ditto.
> 	(df_live_subreg_alloc): Ditto.
> 	(df_live_subreg_reset): Ditto.
> 	(df_live_subreg_bb_local_compute): Ditto.
> 	(df_live_subreg_local_compute): Ditto.
> 	(df_live_subreg_init): Ditto.
> 	(df_live_subreg_check_result): Ditto.
> 	(df_live_subreg_confluence_0): Ditto.
> 	(df_live_subreg_confluence_n): Ditto.
> 	(df_live_subreg_transfer_function): Ditto.
> 	(df_live_subreg_finalize): Ditto.
> 	(df_live_subreg_free): Ditto.
> 	(df_live_subreg_top_dump): Ditto.
> 	(df_live_subreg_bottom_dump): Ditto.
> 	(df_live_subreg_add_problem): Ditto.
> 	* df.h (enum df_problem_id): Add live_subreg id.
> 	(DF_LIVE_SUBREG_INFO): Data accessor.
> 	(DF_LIVE_SUBREG_IN): Ditto.
> 	(DF_LIVE_SUBREG_OUT): Ditto.
> 	(DF_LIVE_SUBREG_FULL_IN): Ditto.
> 	(DF_LIVE_SUBREG_FULL_OUT): Ditto.
> 	(DF_LIVE_SUBREG_PARTIAL_IN): Ditto.
> 	(DF_LIVE_SUBREG_PARTIAL_OUT): Ditto.
> 	(DF_LIVE_SUBREG_RANGE_IN): Ditto.
> 	(DF_LIVE_SUBREG_RANGE_OUT): Ditto.
> 	(class subregs_live): New class.
> 	(class basic_block_subreg_live_info): Ditto.
> 	(class df_live_subreg_bb_info): Ditto.
> 	(df_live_subreg): Ditto.
> 	(df_live_subreg_add_problem): Ditto.
> 	(df_live_subreg_finalize): Ditto.
> 	(class subreg_range): Ditto.
> 	(need_track_subreg): Ditto.
> 	(remove_subreg_range): Ditto.
> 	(add_subreg_range): Ditto.
> 	(df_live_subreg_get_bb_info): Ditto.
> 	* regs.h (get_nblocks): Helper function.
> 	* timevar.def (TV_DF_LIVE_SUBREG): New timevar.
> 	* subreg-live-range.cc: New file.
> 	* subreg-live-range.h: New file.
>
> ---
>  gcc/Makefile.in          |   1 +
>  gcc/df-problems.cc       | 889 ++++++++++++++++++++++++++++++++++++++-
>  gcc/df.h                 |  67 +++
>  gcc/regs.h               |   7 +
>  gcc/subreg-live-range.cc | 628 +++++++++++++++++++++++++++
>  gcc/subreg-live-range.h  | 333 +++++++++++++++
>  gcc/timevar.def          |   1 +
>  7 files changed, 1925 insertions(+), 1 deletion(-)
>  create mode 100644 gcc/subreg-live-range.cc
>  create mode 100644 gcc/subreg-live-range.h
>
> diff --git a/gcc/Makefile.in b/gcc/Makefile.in
> index 29cec21c825..e4403b5a30c 100644
> --- a/gcc/Makefile.in
> +++ b/gcc/Makefile.in
> @@ -1675,6 +1675,7 @@ OBJS = \
>  	store-motion.o \
>  	streamer-hooks.o \
>  	stringpool.o \
> +        subreg-live-range.o \
>  	substring-locations.o \
>  	target-globals.o \
>  	targhooks.o \
> diff --git a/gcc/df-problems.cc b/gcc/df-problems.cc
> index d2cfaf7f50f..2585c762fd1 100644
> --- a/gcc/df-problems.cc
> +++ b/gcc/df-problems.cc
> @@ -28,6 +28,7 @@ along with GCC; see the file COPYING3.  If not see
>  #include "target.h"
>  #include "rtl.h"
>  #include "df.h"
> +#include "subreg-live-range.h"
>  #include "memmodel.h"
>  #include "tm_p.h"
>  #include "insn-config.h"
> @@ -1344,8 +1345,894 @@ df_lr_verify_transfer_functions (void)
>    bitmap_clear (&all_blocks);
>  }
>  
> +/*----------------------------------------------------------------------------
> +   REGISTER AND SUBREG LIVES
> +   Like DF_RL, but fine-grained tracking of subreg lifecycle.
> +   ----------------------------------------------------------------------------*/
> +
> +/* Private data used to verify the solution for this problem.  */
> +struct df_live_subreg_problem_data
> +{
> +  /* An obstack for the bitmaps we need for this problem.  */
> +  bitmap_obstack live_subreg_bitmaps;
> +  bool has_subreg_live_p;
> +};
> +
> +/* Helper functions */
> +
> +/* Return true if REGNO is a pseudo and MODE is a multil regs size.  */
> +bool
> +need_track_subreg (int regno, machine_mode reg_mode)
> +{
> +  poly_int64 total_size = GET_MODE_SIZE (reg_mode);
> +  poly_int64 natural_size = REGMODE_NATURAL_SIZE (reg_mode);
> +  return maybe_gt (total_size, natural_size)
> +	 && multiple_p (total_size, natural_size)
> +	 && regno >= FIRST_PSEUDO_REGISTER;
> +}
> +
> +/* Return subreg_range of REF.  */
> +static subreg_range
> +get_range (df_ref ref)
> +{
> +  rtx reg = DF_REF_REAL_REG (ref);
> +  machine_mode reg_mode = GET_MODE (reg);
> +
> +  if (!read_modify_subreg_p (DF_REF_REG (ref)))
> +    return subreg_range (0, get_nblocks (reg_mode));
> +
> +  rtx subreg = DF_REF_REG (ref);
> +  machine_mode subreg_mode = GET_MODE (subreg);
> +  poly_int64 offset = SUBREG_BYTE (subreg);
> +  int nblocks = get_nblocks (reg_mode);
> +  poly_int64 unit_size = REGMODE_NATURAL_SIZE (reg_mode);
> +  poly_int64 subreg_size = GET_MODE_SIZE (subreg_mode);
> +  poly_int64 left = offset + subreg_size;
> +
> +  int subreg_start = -1;
> +  int subreg_nblocks = -1;
> +  for (int i = 0; i < nblocks; i += 1)
> +    {
> +      poly_int64 right = unit_size * (i + 1);
> +      if (subreg_start < 0 && maybe_lt (offset, right))
> +	subreg_start = i;
> +      if (subreg_nblocks < 0 && maybe_le (left, right))
> +	{
> +	  subreg_nblocks = i + 1 - subreg_start;
> +	  break;
> +	}
> +    }
> +  gcc_assert (subreg_start >= 0 && subreg_nblocks > 0);
> +
> +  return subreg_range (subreg_start, subreg_start + subreg_nblocks);
> +}
> +
> +/* Remove REF from BB_INFO use.  */
> +void
> +remove_subreg_range (basic_block_subreg_live_info *bb_info, unsigned int regno,
> +		     machine_mode mode, const subreg_range &range)
> +{
> +  int max = get_nblocks (mode);
> +  bitmap full = &bb_info->full_use;
> +  bitmap partial = &bb_info->partial_use;
> +  subregs_live *range_live = bb_info->range_use;
> +
> +  if (!range.full_p (max))
> +    {
> +      if (bitmap_bit_p (full, regno))
> +	{
> +	  bitmap_clear_bit (full, regno);
> +	  gcc_assert (!bitmap_bit_p (partial, regno));
> +	  gcc_assert (range_live->empty_p (regno));
> +	  subreg_ranges temp = subreg_ranges (max);
> +	  temp.make_full ();
> +	  temp.remove_range (max, range);
> +	  range_live->add_ranges (regno, temp);
> +	  bitmap_set_bit (partial, regno);
> +	  return;
> +	}
> +      else if (bitmap_bit_p (partial, regno))
> +	{
> +	  range_live->remove_range (regno, max, range);
> +	  if (range_live->empty_p (regno))
> +	    bitmap_clear_bit (partial, regno);
> +	}
> +    }
> +  else if (bitmap_bit_p (full, regno))
> +    {
> +      bitmap_clear_bit (full, regno);
> +      gcc_assert (!bitmap_bit_p (partial, regno));
> +    }
> +  else if (bitmap_bit_p (partial, regno))
> +    {
> +      bitmap_clear_bit (partial, regno);
> +      range_live->remove_live (regno);
> +    }
> +}
> +
> +/* Return true if ref is a tracked subreg access.  */
> +bool
> +remove_subreg_range (basic_block_subreg_live_info *bb_info, df_ref ref)
> +{
> +  unsigned int regno = DF_REF_REGNO (ref);
> +  machine_mode mode = GET_MODE (DF_REF_REAL_REG (ref));
> +  bool subreg_p = read_modify_subreg_p (DF_REF_REG (ref));
> +
> +  if (need_track_subreg (regno, mode))
> +    {
> +      remove_subreg_range (bb_info, regno, mode, get_range (ref));
> +      return subreg_p;
> +    }
> +  else
> +    {
> +      bitmap_clear_bit (&bb_info->full_use, regno);
> +      gcc_assert (!bitmap_bit_p (&bb_info->partial_use, regno));
> +      gcc_assert (!bitmap_bit_p (&bb_info->partial_def, regno));
> +      return false;
> +    }
> +}
> +
> +/* add REF to BB_INFO def/use.  */
> +void
> +add_subreg_range (basic_block_subreg_live_info *bb_info, unsigned int regno,
> +		  machine_mode mode, const subreg_range &range, bool is_def)
> +{
> +  int max = get_nblocks (mode);
> +  bitmap full = is_def ? &bb_info->full_def : &bb_info->full_use;
> +  bitmap partial = is_def ? &bb_info->partial_def : &bb_info->partial_use;
> +  subregs_live *range_live = is_def ? bb_info->range_def : bb_info->range_use;
> +
> +  if (!range.full_p (max))
> +    {
> +      if (bitmap_bit_p (full, regno))
> +	return;
> +      range_live->add_range (regno, max, range);
> +      if (range_live->full_p (regno))
> +	{
> +	  bitmap_set_bit (full, regno);
> +	  gcc_assert (bitmap_bit_p (partial, regno));
> +	  bitmap_clear_bit (partial, regno);
> +	  range_live->remove_live (regno);
> +	}
> +      else if (!bitmap_bit_p (partial, regno))
> +	bitmap_set_bit (partial, regno);
> +    }
> +  else if (!bitmap_bit_p (full, regno))
> +    {
> +      bitmap_set_bit (full, regno);
> +      if (bitmap_bit_p (partial, regno))
> +	{
> +	  bitmap_clear_bit (partial, regno);
> +	  range_live->remove_live (regno);
> +	}
> +    }
> +}
> +
> +/* Return true if ref is a tracked subreg access.  */
> +bool
> +add_subreg_range (basic_block_subreg_live_info *bb_info, df_ref ref,
> +		  bool is_def)
> +{
> +  unsigned int regno = DF_REF_REGNO (ref);
> +  machine_mode mode = GET_MODE (DF_REF_REAL_REG (ref));
> +  bool subreg_p = read_modify_subreg_p (DF_REF_REG (ref));
> +
> +  if (need_track_subreg (regno, mode))
> +    {
> +      add_subreg_range (bb_info, regno, mode, get_range (ref), is_def);
> +      return subreg_p;
> +    }
> +  else
> +    {
> +      bitmap full = is_def ? &bb_info->full_def : &bb_info->full_use;
> +      bitmap partial = is_def ? &bb_info->partial_def : &bb_info->partial_use;
> +      bitmap_set_bit (full, regno);
> +      gcc_assert (!bitmap_bit_p (partial, regno));
> +
> +      if (is_def && DF_REF_FLAGS (ref) & (DF_REF_PARTIAL | DF_REF_CONDITIONAL))
> +	add_subreg_range (bb_info, ref, false);
> +      return false;
> +    }
> +}
> +
> +/* Free basic block info.  */
> +
> +static void
> +df_live_subreg_free_bb_info (basic_block bb ATTRIBUTE_UNUSED, void *vbb_info)
> +{
> +  df_live_subreg_bb_info *bb_info = (df_live_subreg_bb_info *) vbb_info;
> +  if (bb_info)
> +    {
> +      delete bb_info->range_def;
> +      bb_info->range_def = NULL;
> +      delete bb_info->range_use;
> +      bb_info->range_use = NULL;
> +      delete bb_info->range_in;
> +      bb_info->range_in = NULL;
> +      delete bb_info->range_out;
> +      bb_info->range_out = NULL;
> +
> +      bitmap_clear (&bb_info->full_use);
> +      bitmap_clear (&bb_info->partial_use);
> +      bitmap_clear (&bb_info->full_def);
> +      bitmap_clear (&bb_info->partial_def);
> +      bitmap_clear (&bb_info->all_in);
> +      bitmap_clear (&bb_info->full_in);
> +      bitmap_clear (&bb_info->partial_in);
> +      bitmap_clear (&bb_info->all_out);
> +      bitmap_clear (&bb_info->full_out);
> +      bitmap_clear (&bb_info->partial_out);
> +    }
> +}
> +
> +/* Allocate or reset bitmaps for DF_LIVE_SUBREG blocks. The solution bits are
> +   not touched unless the block is new.  */
> +
> +static void
> +df_live_subreg_alloc (bitmap all_blocks ATTRIBUTE_UNUSED)
> +{
> +  struct df_live_subreg_problem_data *problem_data;
> +  df_grow_bb_info (df_live_subreg);
> +  if (df_live_subreg->problem_data)
> +    problem_data
> +      = (struct df_live_subreg_problem_data *) df_live_subreg->problem_data;
> +  else
> +    {
> +      problem_data = XNEW (struct df_live_subreg_problem_data);
> +      df_live_subreg->problem_data = problem_data;
> +
> +      bitmap_obstack_initialize (&problem_data->live_subreg_bitmaps);
> +      problem_data->has_subreg_live_p = false;
> +    }
> +
> +  basic_block bb;
> +  FOR_EACH_BB_FN (bb, cfun)
> +    bitmap_set_bit (df_live_subreg->out_of_date_transfer_functions, bb->index);
> +
> +  bitmap_set_bit (df_live_subreg->out_of_date_transfer_functions, ENTRY_BLOCK);
> +  bitmap_set_bit (df_live_subreg->out_of_date_transfer_functions, EXIT_BLOCK);
> +
> +  unsigned int bb_index;
> +  bitmap_iterator bi;
> +  EXECUTE_IF_SET_IN_BITMAP (df_live_subreg->out_of_date_transfer_functions, 0,
> +			    bb_index, bi)
> +    {
> +      df_live_subreg_bb_info *bb_info = df_live_subreg_get_bb_info (bb_index);
> +
> +      /* When bitmaps are already initialized, just clear them.  */
> +      if (bb_info->full_use.obstack)
> +	{
> +	  bitmap_clear (&bb_info->full_def);
> +	  bitmap_clear (&bb_info->partial_def);
> +	  bitmap_clear (&bb_info->full_use);
> +	  bitmap_clear (&bb_info->partial_use);
> +	  bitmap_clear (&bb_info->all_in);
> +	  bitmap_clear (&bb_info->full_in);
> +	  bitmap_clear (&bb_info->partial_in);
> +	  bitmap_clear (&bb_info->all_out);
> +	  bitmap_clear (&bb_info->full_out);
> +	  bitmap_clear (&bb_info->partial_out);
> +	}
> +      else
> +	{
> +	  bitmap_initialize (&bb_info->full_def,
> +			     &problem_data->live_subreg_bitmaps);
> +	  bitmap_initialize (&bb_info->partial_def,
> +			     &problem_data->live_subreg_bitmaps);
> +	  bitmap_initialize (&bb_info->full_use,
> +			     &problem_data->live_subreg_bitmaps);
> +	  bitmap_initialize (&bb_info->partial_use,
> +			     &problem_data->live_subreg_bitmaps);
> +	  bitmap_initialize (&bb_info->all_in,
> +			     &problem_data->live_subreg_bitmaps);
> +	  bitmap_initialize (&bb_info->full_in,
> +			     &problem_data->live_subreg_bitmaps);
> +	  bitmap_initialize (&bb_info->partial_in,
> +			     &problem_data->live_subreg_bitmaps);
> +	  bitmap_initialize (&bb_info->all_out,
> +			     &problem_data->live_subreg_bitmaps);
> +	  bitmap_initialize (&bb_info->full_out,
> +			     &problem_data->live_subreg_bitmaps);
> +	  bitmap_initialize (&bb_info->partial_out,
> +			     &problem_data->live_subreg_bitmaps);
> +	}
> +
> +      if (bb_info->range_def)
> +	{
> +	  bb_info->range_def->clear ();
> +	  bb_info->range_use->clear ();
> +	  bb_info->range_in->clear ();
> +	  bb_info->range_out->clear ();
> +	}
> +      else
> +	{
> +	  bb_info->range_def = new subregs_live ();
> +	  bb_info->range_use = new subregs_live ();
> +	  bb_info->range_in = new subregs_live ();
> +	  bb_info->range_out = new subregs_live ();
> +	}
> +    }
> +  df_live_subreg->optional_p = true;
> +}
> +
> +/* Reset the global solution for recalculation.  */
> +
> +static void
> +df_live_subreg_reset (bitmap all_blocks)
> +{
> +  unsigned int bb_index;
> +  bitmap_iterator bi;
> +
> +  EXECUTE_IF_SET_IN_BITMAP (all_blocks, 0, bb_index, bi)
> +    {
> +      df_live_subreg_bb_info *bb_info = df_live_subreg_get_bb_info (bb_index);
> +      gcc_assert (bb_info);
> +      bitmap_clear (&bb_info->all_in);
> +      bitmap_clear (&bb_info->full_in);
> +      bitmap_clear (&bb_info->partial_in);
> +      bitmap_clear (&bb_info->all_out);
> +      bitmap_clear (&bb_info->full_out);
> +      bitmap_clear (&bb_info->partial_out);
> +      bb_info->range_in->clear ();
> +      bb_info->range_out->clear ();
> +    }
> +}
> +
> +/* Compute local live register info for basic block BB.  */
> +
> +static void
> +df_live_subreg_bb_local_compute (unsigned int bb_index)
> +{
> +  basic_block bb = BASIC_BLOCK_FOR_FN (cfun, bb_index);
> +  df_live_subreg_bb_info *bb_info = df_live_subreg_get_bb_info (bb_index);
> +  df_live_subreg_problem_data *problem_data
> +    = (df_live_subreg_problem_data *) df_live_subreg->problem_data;
> +  rtx_insn *insn;
> +  df_ref def, use;
> +
> +  /* Process the registers set in an exception handler.  */
> +  FOR_EACH_ARTIFICIAL_DEF (def, bb_index)
> +    if ((DF_REF_FLAGS (def) & DF_REF_AT_TOP) == 0)
> +      {
> +	problem_data->has_subreg_live_p
> +	  |= add_subreg_range (bb_info, def, true);
> +	problem_data->has_subreg_live_p |= remove_subreg_range (bb_info, def);
> +      }
> +
> +  /* Process the hardware registers that are always live.  */
> +  FOR_EACH_ARTIFICIAL_USE (use, bb_index)
> +    /* Add use to set of uses in this BB.  */
> +    if ((DF_REF_FLAGS (use) & DF_REF_AT_TOP) == 0)
> +      problem_data->has_subreg_live_p |= add_subreg_range (bb_info, use);
> +
> +  FOR_BB_INSNS_REVERSE (bb, insn)
> +    {
> +      if (!NONDEBUG_INSN_P (insn))
> +	continue;
> +
> +      df_insn_info *insn_info = DF_INSN_INFO_GET (insn);
> +      FOR_EACH_INSN_INFO_DEF (def, insn_info)
> +	{
> +	  problem_data->has_subreg_live_p |= remove_subreg_range (bb_info, def);
> +	  problem_data->has_subreg_live_p
> +	    |= add_subreg_range (bb_info, def, true);
> +	}
> +
> +      FOR_EACH_INSN_INFO_USE (use, insn_info)
> +	{
> +	  unsigned int regno = DF_REF_REGNO (use);
> +	  machine_mode mode = GET_MODE (DF_REF_REAL_REG (use));
> +	  /* Ignore the use of SET_DEST which is (subreg (reg) offset).  */
> +	  if (need_track_subreg (regno, mode)
> +	      && DF_REF_FLAGS (use) & (DF_REF_READ_WRITE | DF_REF_SUBREG))
> +	    continue;
> +	  problem_data->has_subreg_live_p |= add_subreg_range (bb_info, use);
> +	}
> +    }
> +
> +  /* Process the registers set in an exception handler or the hard
> +     frame pointer if this block is the target of a non local
> +     goto.  */
> +  FOR_EACH_ARTIFICIAL_DEF (def, bb_index)
> +    if (DF_REF_FLAGS (def) & DF_REF_AT_TOP)
> +      {
> +	problem_data->has_subreg_live_p
> +	  |= add_subreg_range (bb_info, def, true);
> +	problem_data->has_subreg_live_p |= remove_subreg_range (bb_info, def);
> +      }
> +
> +#ifdef EH_USES
> +  /* Process the uses that are live into an exception handler.  */
> +  FOR_EACH_ARTIFICIAL_USE (use, bb_index)
> +    /* Add use to set of uses in this BB.  */
> +    if (DF_REF_FLAGS (use) & DF_REF_AT_TOP)
> +      problem_data->has_subreg_live_p |= add_subreg_range (bb_info, use);
> +#endif
> +}
> +
> +/* Compute local live register info for each basic block within BLOCKS.  */
> +
> +static void
> +df_live_subreg_local_compute (bitmap all_blocks ATTRIBUTE_UNUSED)
> +{
> +  unsigned int bb_index, i;
> +  bitmap_iterator bi;
> +
> +  bitmap_clear (&df->hardware_regs_used);
> +
> +  /* The all-important stack pointer must always be live.  */
> +  bitmap_set_bit (&df->hardware_regs_used, STACK_POINTER_REGNUM);
> +
> +  /* Global regs are always live, too.  */
> +  for (i = 0; i < FIRST_PSEUDO_REGISTER; i++)
> +    if (global_regs[i])
> +      bitmap_set_bit (&df->hardware_regs_used, i);
> +
> +  /* Before reload, there are a few registers that must be forced
> +     live everywhere -- which might not already be the case for
> +     blocks within infinite loops.  */
> +  if (!reload_completed)
> +    {
> +      unsigned int pic_offset_table_regnum = PIC_OFFSET_TABLE_REGNUM;
> +      /* Any reference to any pseudo before reload is a potential
> +	 reference of the frame pointer.  */
> +      bitmap_set_bit (&df->hardware_regs_used, FRAME_POINTER_REGNUM);
> +
> +      /* Pseudos with argument area equivalences may require
> +	 reloading via the argument pointer.  */
> +      if (FRAME_POINTER_REGNUM != ARG_POINTER_REGNUM
> +	  && fixed_regs[ARG_POINTER_REGNUM])
> +	bitmap_set_bit (&df->hardware_regs_used, ARG_POINTER_REGNUM);
> +
> +      /* Any constant, or pseudo with constant equivalences, may
> +	 require reloading from memory using the pic register.  */
> +      if (pic_offset_table_regnum != INVALID_REGNUM
> +	  && fixed_regs[pic_offset_table_regnum])
> +	bitmap_set_bit (&df->hardware_regs_used, pic_offset_table_regnum);
> +    }
> +
> +  EXECUTE_IF_SET_IN_BITMAP (df_live_subreg->out_of_date_transfer_functions, 0,
> +			    bb_index, bi)
> +    {
> +      if (bb_index == EXIT_BLOCK)
> +	{
> +	  /* The exit block is special for this problem and its bits are
> +	     computed from thin air.  */
> +	  class df_live_subreg_bb_info *bb_info
> +	    = df_live_subreg_get_bb_info (EXIT_BLOCK);
> +	  bitmap_copy (&bb_info->full_use, df->exit_block_uses);
> +	}
> +      else
> +	df_live_subreg_bb_local_compute (bb_index);
> +    }
> +
> +  bitmap_clear (df_live_subreg->out_of_date_transfer_functions);
> +}
> +
> +/* Initialize the solution vectors.  */
> +
> +static void
> +df_live_subreg_init (bitmap all_blocks)
> +{
> +  unsigned int bb_index;
> +  bitmap_iterator bi;
> +
> +  EXECUTE_IF_SET_IN_BITMAP (all_blocks, 0, bb_index, bi)
> +    {
> +      df_live_subreg_bb_info *bb_info = df_live_subreg_get_bb_info (bb_index);
> +      bitmap_copy (&bb_info->full_in, &bb_info->full_use);
> +      bitmap_copy (&bb_info->partial_in, &bb_info->partial_use);
> +      bb_info->range_in->copy_lives (*bb_info->range_use);
> +      bitmap_clear (&bb_info->full_out);
> +      bitmap_clear (&bb_info->partial_out);
> +      bb_info->range_out->clear ();
> +    }
> +}
> +
> +/* Check the result is golden.  */
> +static void
> +df_live_subreg_check_result (bitmap full, bitmap partial,
> +			     subregs_live *partial_live)
> +{
> +  unsigned int regno;
> +  bitmap_iterator bi;
> +  gcc_assert (!bitmap_intersect_p (full, partial));
> +  EXECUTE_IF_SET_IN_BITMAP (full, 0, regno, bi)
> +    gcc_assert (partial_live->empty_p (regno));
> +  EXECUTE_IF_SET_IN_BITMAP (partial, 0, regno, bi)
> +    gcc_assert (!partial_live->empty_p (regno));
> +}
> +
> +/* Confluence function that processes infinite loops.  This might be a
> +   noreturn function that throws.  And even if it isn't, getting the
> +   unwind info right helps debugging.  */
> +static void
> +df_live_subreg_confluence_0 (basic_block bb)
> +{
> +  bitmap full_out = &df_live_subreg_get_bb_info (bb->index)->full_out;
> +  if (bb != EXIT_BLOCK_PTR_FOR_FN (cfun))
> +    bitmap_copy (full_out, &df->hardware_regs_used);
> +}
> +
> +/* Confluence function that ignores fake edges.  */
> +
> +static bool
> +df_live_subreg_confluence_n (edge e)
> +{
> +  df_live_subreg_problem_data *problem_data
> +    = (df_live_subreg_problem_data *) df_live_subreg->problem_data;
> +  class df_live_subreg_bb_info *src_bb_info
> +    = df_live_subreg_get_bb_info (e->src->index);
> +  class df_live_subreg_bb_info *dest_bb_info
> +    = df_live_subreg_get_bb_info (e->dest->index);
> +
> +  if (!problem_data->has_subreg_live_p)
> +    {
> +      bool changed = false;
> +
> +      /* Call-clobbered registers die across exception and call edges.
> +	 Conservatively treat partially-clobbered registers as surviving
> +	 across the edges; they might or might not, depending on what
> +	 mode they have.  */
> +      /* ??? Abnormal call edges ignored for the moment, as this gets
> +	 confused by sibling call edges, which crashes reg-stack.  */
> +      if (e->flags & EDGE_EH)
> +	{
> +	  bitmap_view<HARD_REG_SET> eh_kills (eh_edge_abi.full_reg_clobbers ());
> +	  changed
> +	    = bitmap_ior_and_compl_into (&src_bb_info->full_out,
> +					 &dest_bb_info->full_in, eh_kills);
> +	}
> +      else
> +	changed
> +	  = bitmap_ior_into (&src_bb_info->full_out, &dest_bb_info->full_in);
> +
> +      changed
> +	|= bitmap_ior_into (&src_bb_info->full_out, &df->hardware_regs_used);
> +      return changed;
> +    }
> +
> +  /* If there has subreg live need be tracked. Calculation formula:
> +       temp_full mean:
> +	 1. partial in out/in, full in other in/out
> +	 2. partial in out and in, and mrege range is full
> +       temp_range mean:
> +	 the range of regno which partial live
> +       src_bb_info->partial_out = (src_bb_info->partial_out |
> +				   dest_bb_info->partial_in) & ~temp_full
> +       src_bb_info->range_out = copy(temp_range)
> +       src_bb_info->full_out |= dest_bb_info->full_in | temp_full
> +       */
> +  subregs_live temp_range;
> +  temp_range.add_lives (*src_bb_info->range_out);
> +  temp_range.add_lives (*dest_bb_info->range_in);
> +
> +  bitmap_head temp_partial_all;
> +  bitmap_initialize (&temp_partial_all, &bitmap_default_obstack);
> +  bitmap_ior (&temp_partial_all, &src_bb_info->partial_out,
> +	      &dest_bb_info->partial_in);
> +
> +  bitmap_head temp_full;
> +  bitmap_initialize (&temp_full, &bitmap_default_obstack);
> +
> +  /* Collect regno that become full after merge src_bb_info->partial_out
> +     and dest_bb_info->partial_in.  */
> +  unsigned int regno;
> +  bitmap_iterator bi;
> +  EXECUTE_IF_SET_IN_BITMAP (&temp_partial_all, FIRST_PSEUDO_REGISTER, regno, bi)
> +    {
> +      if (bitmap_bit_p (&src_bb_info->full_out, regno)
> +	  || bitmap_bit_p (&dest_bb_info->full_in, regno))
> +	{
> +	  bitmap_set_bit (&temp_full, regno);
> +	  temp_range.remove_live (regno);
> +	  continue;
> +	}
> +      else if (!bitmap_bit_p (&src_bb_info->partial_out, regno)
> +	       || !bitmap_bit_p (&dest_bb_info->partial_in, regno))
> +	continue;
> +
> +      subreg_ranges temp = src_bb_info->range_out->lives.at (regno);
> +      temp.add_ranges (dest_bb_info->range_in->lives.at (regno));
> +      if (temp.full_p ())
> +	{
> +	  bitmap_set_bit (&temp_full, regno);
> +	  temp_range.remove_live (regno);
> +	}
> +    }
> +
> +  /* Calculating src_bb_info->partial_out and src_bb_info->range_out.  */
> +  bool changed = bitmap_and_compl (&src_bb_info->partial_out, &temp_partial_all,
> +				   &temp_full);
> +  changed |= src_bb_info->range_out->copy_lives (temp_range);
> +
> +  /* Calculating src_bb_info->full_out.  */
> +  bitmap_ior_into (&temp_full, &dest_bb_info->full_in);
> +
> +  /* Call-clobbered registers die across exception and call edges.
> +     Conservatively treat partially-clobbered registers as surviving
> +     across the edges; they might or might not, depending on what
> +     mode they have.  */
> +  /* ??? Abnormal call edges ignored for the moment, as this gets
> +     confused by sibling call edges, which crashes reg-stack.  */
> +  if (e->flags & EDGE_EH)
> +    {
> +      bitmap_view<HARD_REG_SET> eh_kills (eh_edge_abi.full_reg_clobbers ());
> +      changed |= bitmap_ior_and_compl_into (&src_bb_info->full_out, &temp_full,
> +					    eh_kills);
> +    }
> +  else
> +    changed |= bitmap_ior_into (&src_bb_info->full_out, &temp_full);
> +
> +  changed |= bitmap_ior_into (&src_bb_info->full_out, &df->hardware_regs_used);
> +
> +  bitmap_clear (&temp_full);
> +  bitmap_clear (&temp_partial_all);
> +
> +  df_live_subreg_check_result (&src_bb_info->full_out,
> +			       &src_bb_info->partial_out,
> +			       src_bb_info->range_out);
> +  return changed;
> +}
> +
> +/* Transfer function.  */
> +
> +static bool
> +df_live_subreg_transfer_function (int bb_index)
> +{
> +  class df_live_subreg_bb_info *bb_info = df_live_subreg_get_bb_info (bb_index);
> +  df_live_subreg_problem_data *problem_data
> +    = (df_live_subreg_problem_data *) df_live_subreg->problem_data;
> +  if (!problem_data->has_subreg_live_p)
> +    {
> +      bitmap in = &bb_info->full_in;
> +      bitmap out = &bb_info->full_out;
> +      bitmap use = &bb_info->full_use;
> +      bitmap def = &bb_info->full_def;
> +
> +      return bitmap_ior_and_compl (in, use, out, def);
> +    }
> +
> +  /* If there has subreg live need be tracked, follow the bellow calculation
> +     formula:
> +       all_def = full_def | partial_def
> +       temp_partial_out = ((full_out & partail_def)
> +			   | (partail_out & ~all_def)
> +			   | (partial_out remove partail_def not empty))
> +			  & ~full_use
> +       temp_partial_be_full = (temp_partial_out & partial_use) merge be full
> +       full_in = full_use | full_out & ~all_def | temp_partial_be_full
> +       partail_in = (temp_partial_out | partial_use) & ~temp_partial_be_full  */
> +  unsigned int regno;
> +  bitmap_iterator bi;
> +  bool changed = false;
> +  bitmap_head temp_partial_out;
> +  bitmap_head temp_partial_be_full;
> +  bitmap_head all_def;
> +  subregs_live temp_range_out;
> +  bitmap_initialize (&temp_partial_out, &bitmap_default_obstack);
> +  bitmap_initialize (&temp_partial_be_full, &bitmap_default_obstack);
> +  bitmap_initialize (&all_def, &bitmap_default_obstack);
> +
> +  bitmap_ior (&all_def, &bb_info->full_def, &bb_info->partial_def);
> +
> +  /* temp_partial_out = (full_out & partail_def) */
> +  bitmap_and (&temp_partial_out, &bb_info->full_out, &bb_info->partial_def);
> +  EXECUTE_IF_SET_IN_BITMAP (&temp_partial_out, FIRST_PSEUDO_REGISTER, regno, bi)
> +    {
> +      subreg_ranges temp (bb_info->range_def->lives.at (regno).max);
> +      temp.make_full ();
> +      temp.remove_ranges (bb_info->range_def->lives.at (regno));
> +      temp_range_out.add_ranges (regno, temp);
> +    }
> +
> +  /* temp_partial_out |= (partail_out & ~all_def) */
> +  bitmap_ior_and_compl_into (&temp_partial_out, &bb_info->partial_out,
> +			     &all_def);
> +  EXECUTE_IF_AND_COMPL_IN_BITMAP (&bb_info->partial_out, &all_def,
> +				  FIRST_PSEUDO_REGISTER, regno, bi)
> +    {
> +      temp_range_out.add_ranges (regno, bb_info->range_out->lives.at (regno));
> +    }
> +
> +  /* temp_partial_out |= (partial_out remove partail_def not empty) */
> +  EXECUTE_IF_AND_IN_BITMAP (&bb_info->partial_out, &bb_info->partial_def, 0,
> +			    regno, bi)
> +    {
> +      subreg_ranges temp = bb_info->range_out->lives.at (regno);
> +      temp.remove_ranges (bb_info->range_def->lives.at (regno));
> +      if (!temp.empty_p ())
> +	{
> +	  bitmap_set_bit (&temp_partial_out, regno);
> +	  temp_range_out.add_ranges (regno, temp);
> +	}
> +    }
> +
> +  /* temp_partial_out = temp_partial_out & ~full_use */
> +  bitmap_and_compl_into (&temp_partial_out, &bb_info->full_use);
> +  EXECUTE_IF_SET_IN_BITMAP (&bb_info->full_use, 0, regno, bi)
> +    if (!temp_range_out.empty_p (regno))
> +      temp_range_out.remove_live (regno);
> +
> +  /* temp_partial_be_full = (temp_partial_out & partial_use) merge become full
> +   */
> +  temp_range_out.add_lives (*bb_info->range_use);
> +  /* Remove all range which in partial_use and in full_out and not in all_def.
> +   */
> +  EXECUTE_IF_SET_IN_BITMAP (&bb_info->full_out, 0, regno, bi)
> +    if (!bitmap_bit_p (&all_def, regno) && !temp_range_out.empty_p (regno))
> +      temp_range_out.remove_live (regno);
> +
> +  EXECUTE_IF_AND_IN_BITMAP (&temp_partial_out, &bb_info->partial_use, 0, regno,
> +			    bi)
> +    {
> +      subreg_ranges temp = temp_range_out.lives.at (regno);
> +      temp.add_ranges (bb_info->range_use->lives.at (regno));
> +      if (temp.full_p ())
> +	{
> +	  bitmap_set_bit (&temp_partial_be_full, regno);
> +	  temp_range_out.remove_live (regno);
> +	}
> +    }
> +
> +  /* Calculating full_in.  */
> +  bitmap_ior_and_compl_into (&temp_partial_be_full, &bb_info->full_out,
> +			     &all_def);
> +  changed |= bitmap_ior (&bb_info->full_in, &temp_partial_be_full,
> +			 &bb_info->full_use);
> +
> +  /* Calculating partial_in and range_in.  */
> +  bitmap_ior_into (&temp_partial_out, &bb_info->partial_use);
> +  changed |= bitmap_and_compl (&bb_info->partial_in, &temp_partial_out,
> +			       &temp_partial_be_full);
> +  changed |= bb_info->range_in->copy_lives (temp_range_out);
> +
> +  bitmap_clear (&temp_partial_out);
> +  bitmap_clear (&temp_partial_be_full);
> +  bitmap_clear (&all_def);
> +
> +  df_live_subreg_check_result (&bb_info->full_in, &bb_info->partial_in,
> +			       bb_info->range_in);
> +
> +  return changed;
> +}
> +
> +/* Run the fast dce as a side effect of building LR.  */
> +
> +void
> +df_live_subreg_finalize (bitmap all_blocks)
> +{
> +  unsigned int bb_index;
> +  bitmap_iterator bi;
> +  EXECUTE_IF_SET_IN_BITMAP (all_blocks, 0, bb_index, bi)
> +    {
> +      class df_live_subreg_bb_info *bb_info
> +	= df_live_subreg_get_bb_info (bb_index);
> +      gcc_assert (bb_info);
> +      bitmap_ior (&bb_info->all_in, &bb_info->full_in, &bb_info->partial_in);
> +      bitmap_ior (&bb_info->all_out, &bb_info->full_out, &bb_info->partial_out);
> +    }
> +}
> +
> +/* Free all storage associated with the problem.  */
> +
> +static void
> +df_live_subreg_free (void)
> +{
> +  df_live_subreg_problem_data *problem_data
> +    = (df_live_subreg_problem_data *) df_live_subreg->problem_data;
> +  if (df_live_subreg->block_info)
> +    {
> +      df_live_subreg->block_info_size = 0;
> +      free (df_live_subreg->block_info);
> +      df_live_subreg->block_info = NULL;
> +      bitmap_obstack_release (&problem_data->live_subreg_bitmaps);
> +      free (df_live_subreg->problem_data);
> +      df_live_subreg->problem_data = NULL;
> +    }
> +
> +  BITMAP_FREE (df_live_subreg->out_of_date_transfer_functions);
> +  free (df_live_subreg);
> +}
> +
> +/* Debugging info at top of bb.  */
> +
> +static void
> +df_live_subreg_top_dump (basic_block bb, FILE *file)
> +{
> +  df_live_subreg_bb_info *bb_info = df_live_subreg_get_bb_info (bb->index);
> +  if (!bb_info)
> +    return;
> +
> +  fprintf (file, ";; subreg live all in  \t");
> +  df_print_regset (file, &bb_info->all_in);
> +  fprintf (file, ";;   subreg live full in  \t");
> +  df_print_regset (file, &bb_info->full_in);
> +  fprintf (file, ";;   subreg live partial in  \t");
> +  df_print_regset (file, &bb_info->partial_in);
> +  fprintf (file, ";;   subreg live range in  \t");
> +  bb_info->range_in->dump (file, "");
> +
> +  fprintf (file, "\n;;   subreg live full use  \t");
> +  df_print_regset (file, &bb_info->full_use);
> +  fprintf (file, ";;   subreg live partial use  \t");
> +  df_print_regset (file, &bb_info->partial_use);
> +  fprintf (file, ";;   subreg live range use  \t");
> +  bb_info->range_use->dump (file, "");
> +
> +  fprintf (file, "\n;;   subreg live full def  \t");
> +  df_print_regset (file, &bb_info->full_def);
> +  fprintf (file, ";;   subreg live partial def  \t");
> +  df_print_regset (file, &bb_info->partial_def);
> +  fprintf (file, ";;   subreg live range def \t");
> +  bb_info->range_def->dump (file, "");
> +}
> +
> +/* Debugging info at bottom of bb.  */
> +
> +static void
> +df_live_subreg_bottom_dump (basic_block bb, FILE *file)
> +{
> +  df_live_subreg_bb_info *bb_info = df_live_subreg_get_bb_info (bb->index);
> +  if (!bb_info)
> +    return;
> +
> +  fprintf (file, ";; subreg live all out  \t");
> +  df_print_regset (file, &bb_info->all_out);
> +  fprintf (file, ";;   subreg live full out  \t");
> +  df_print_regset (file, &bb_info->full_out);
> +  fprintf (file, ";;   subreg live partial out  \t");
> +  df_print_regset (file, &bb_info->partial_out);
> +  fprintf (file, ";;   subreg live range out  \t");
> +  bb_info->range_out->dump (file, "");
> +}
> +
> +/* All of the information associated with every instance of the problem.  */
> +
> +static const struct df_problem problem_LIVE_SUBREG = {
> +  DF_LIVE_SUBREG,		    /* Problem id.  */
> +  DF_BACKWARD,			    /* Direction.  */
> +  df_live_subreg_alloc,		    /* Allocate the problem specific data.  */
> +  df_live_subreg_reset,		    /* Reset global information.  */
> +  df_live_subreg_free_bb_info,	    /* Free basic block info.  */
> +  df_live_subreg_local_compute,	    /* Local compute function.  */
> +  df_live_subreg_init,		    /* Init the solution specific data.  */
> +  df_worklist_dataflow,		    /* Worklist solver.  */
> +  df_live_subreg_confluence_0,	    /* Confluence operator 0.  */
> +  df_live_subreg_confluence_n,	    /* Confluence operator n.  */
> +  df_live_subreg_transfer_function, /* Transfer function.  */
> +  df_live_subreg_finalize,	    /* Finalize function.  */
> +  df_live_subreg_free,		    /* Free all of the problem information.  */
> +  df_live_subreg_free,	      /* Remove this problem from the stack of dataflow
> +				 problems.  */
> +  NULL,			      /* Debugging.  */
> +  df_live_subreg_top_dump,    /* Debugging start block.  */
> +  df_live_subreg_bottom_dump, /* Debugging end block.  */
> +  NULL,			      /* Debugging start insn.  */
> +  NULL,			      /* Debugging end insn.  */
> +  NULL,			      /* Incremental solution verify start.  */
> +  NULL,			      /* Incremental solution verify end.  */
> +  &problem_LR,		      /* Dependent problem.  */
> +  sizeof (df_live_subreg_bb_info), /* Size of entry of block_info array. */
> +  TV_DF_LIVE_SUBREG,		   /* Timing variable.  */
> +  false /* Reset blocks on dropping out of blocks_to_analyze.  */
> +};
> +
> +/* Create a new DATAFLOW instance and add it to an existing instance
> +   of DF.  The returned structure is what is used to get at the
> +   solution.  */
> +
> +void
> +df_live_subreg_add_problem (void)
> +{
> +  df_add_problem (&problem_LIVE_SUBREG);
> +
> +  /* These will be initialized when df_scan_blocks processes each
> +     block.  */
> +  df_live_subreg->out_of_date_transfer_functions
> +    = BITMAP_ALLOC (&df_bitmap_obstack);
> +}
>  
> -\f
>  /*----------------------------------------------------------------------------
>     LIVE AND MAY-INITIALIZED REGISTERS.
>  
> diff --git a/gcc/df.h b/gcc/df.h
> index 402657a7076..50a6cf99863 100644
> --- a/gcc/df.h
> +++ b/gcc/df.h
> @@ -47,6 +47,7 @@ enum df_problem_id
>    {
>      DF_SCAN,
>      DF_LR,                /* Live Registers backward. */
> +    DF_LIVE_SUBREG,       /* Live Ranges and Live Subreg */
>      DF_LIVE,              /* Live Registers & Uninitialized Registers */
>      DF_RD,                /* Reaching Defs. */
>      DF_CHAIN,             /* Def-Use and/or Use-Def Chains. */
> @@ -619,6 +620,7 @@ public:
>  #define DF_SCAN_BB_INFO(BB) (df_scan_get_bb_info ((BB)->index))
>  #define DF_RD_BB_INFO(BB) (df_rd_get_bb_info ((BB)->index))
>  #define DF_LR_BB_INFO(BB) (df_lr_get_bb_info ((BB)->index))
> +#define DF_LIVE_SUBREG_INFO(BB) (df_live_subreg_get_bb_info ((BB)->index))
>  #define DF_LIVE_BB_INFO(BB) (df_live_get_bb_info ((BB)->index))
>  #define DF_WORD_LR_BB_INFO(BB) (df_word_lr_get_bb_info ((BB)->index))
>  #define DF_MD_BB_INFO(BB) (df_md_get_bb_info ((BB)->index))
> @@ -632,6 +634,15 @@ public:
>  #define DF_MIR_IN(BB) (&DF_MIR_BB_INFO (BB)->in)
>  #define DF_MIR_OUT(BB) (&DF_MIR_BB_INFO (BB)->out)
>  
> +#define DF_LIVE_SUBREG_IN(BB) (&DF_LIVE_SUBREG_INFO (BB)->all_in)
> +#define DF_LIVE_SUBREG_OUT(BB) (&DF_LIVE_SUBREG_INFO (BB)->all_out)
> +#define DF_LIVE_SUBREG_FULL_IN(BB) (&DF_LIVE_SUBREG_INFO (BB)->full_in)
> +#define DF_LIVE_SUBREG_FULL_OUT(BB) (&DF_LIVE_SUBREG_INFO (BB)->full_out)
> +#define DF_LIVE_SUBREG_PARTIAL_IN(BB) (&DF_LIVE_SUBREG_INFO (BB)->partial_in)
> +#define DF_LIVE_SUBREG_PARTIAL_OUT(BB) (&DF_LIVE_SUBREG_INFO (BB)->partial_out)
> +#define DF_LIVE_SUBREG_RANGE_IN(BB) (DF_LIVE_SUBREG_INFO (BB)->range_in)
> +#define DF_LIVE_SUBREG_RANGE_OUT(BB) (DF_LIVE_SUBREG_INFO (BB)->range_out)
> +
>  /* These macros are used by passes that are not tolerant of
>     uninitialized variables.  This intolerance should eventually
>     be fixed.  */
> @@ -878,6 +889,32 @@ public:
>    bitmap_head out;   /* At the bottom of the block.  */
>  };
>  
> +class subregs_live;
> +
> +class basic_block_subreg_live_info
> +{
> +public:
> +  bitmap_head full_def;
> +  bitmap_head full_use;
> +  /* Only for pseudo registers.  */
> +  bitmap_head partial_def;
> +  bitmap_head partial_use;
> +  subregs_live *range_def = NULL;
> +  subregs_live *range_use = NULL;
> +};
> +
> +/* Live registers and live ranges including specifial subreg.  */
> +class df_live_subreg_bb_info : public basic_block_subreg_live_info
> +{
> +public:
> +  bitmap_head all_in, full_in;
> +  bitmap_head all_out, full_out;
> +  /* Only for pseudo registers.  */
> +  bitmap_head partial_in;
> +  bitmap_head partial_out;
> +  subregs_live *range_in = NULL;
> +  subregs_live *range_out = NULL;
> +};
>  
>  /* Uninitialized registers.  All bitmaps are referenced by the
>     register number.  Anded results of the forwards and backward live
> @@ -946,6 +983,7 @@ extern class df_d *df;
>  #define df_note    (df->problems_by_index[DF_NOTE])
>  #define df_md      (df->problems_by_index[DF_MD])
>  #define df_mir     (df->problems_by_index[DF_MIR])
> +#define df_live_subreg (df->problems_by_index[DF_LIVE_SUBREG])
>  
>  /* This symbol turns on checking that each modification of the cfg has
>    been identified to the appropriate df routines.  It is not part of
> @@ -1031,6 +1069,25 @@ extern void df_lr_add_problem (void);
>  extern void df_lr_verify_transfer_functions (void);
>  extern void df_live_verify_transfer_functions (void);
>  extern void df_live_add_problem (void);
> +extern void
> +df_live_subreg_add_problem (void);
> +extern void
> +df_live_subreg_finalize (bitmap all_blocks);
> +class subreg_range;
> +extern bool
> +need_track_subreg (int regno, machine_mode mode);
> +extern void
> +remove_subreg_range (basic_block_subreg_live_info *bb_info, unsigned int regno,
> +		     machine_mode mode, const subreg_range &range);
> +extern bool
> +remove_subreg_range (basic_block_subreg_live_info *bb_info, df_ref ref);
> +extern void
> +add_subreg_range (basic_block_subreg_live_info *bb_info, unsigned int regno,
> +		  machine_mode mode, const subreg_range &range,
> +		  bool is_def = false);
> +extern bool
> +add_subreg_range (basic_block_subreg_live_info *bb_info, df_ref ref,
> +		  bool is_def = false);
>  extern void df_live_set_all_dirty (void);
>  extern void df_chain_add_problem (unsigned int);
>  extern void df_word_lr_add_problem (void);
> @@ -1124,6 +1181,16 @@ df_lr_get_bb_info (unsigned int index)
>      return NULL;
>  }
>  
> +inline class df_live_subreg_bb_info *
> +df_live_subreg_get_bb_info (unsigned int index)
> +{
> +  if (index < df_live_subreg->block_info_size)
> +    return &(
> +      (class df_live_subreg_bb_info *) df_live_subreg->block_info)[index];
> +  else
> +    return NULL;
> +}
> +
>  inline class df_md_bb_info *
>  df_md_get_bb_info (unsigned int index)
>  {
> diff --git a/gcc/regs.h b/gcc/regs.h
> index aea093ed795..84c6bdb980c 100644
> --- a/gcc/regs.h
> +++ b/gcc/regs.h
> @@ -389,4 +389,11 @@ range_in_hard_reg_set_p (const_hard_reg_set set, unsigned regno, int nregs)
>    return true;
>  }
>  
> +/* Return the number of blocks the MODE overlap. One block equal mode's natural
> +   size. So, satisfy the following equation:
> +     (nblocks - 1) * natural_size < GET_MODE_SIZE (mode)
> +       <= nblocks * natural_size. */
> +#define get_nblocks(mode)                                                      \
> +  (exact_div (GET_MODE_SIZE (mode), REGMODE_NATURAL_SIZE (mode)).to_constant ())
> +
>  #endif /* GCC_REGS_H */
> diff --git a/gcc/subreg-live-range.cc b/gcc/subreg-live-range.cc
> new file mode 100644
> index 00000000000..43a5eafedf1
> --- /dev/null
> +++ b/gcc/subreg-live-range.cc
> @@ -0,0 +1,628 @@
> +/* SUBREG live range track classes for DF & IRA & LRA.
> +   Copyright (C) 2023 Free Software Foundation, Inc.
> +   Contributed by Lehua Ding (lehua.ding@rivai.ai), RiVAI Technologies Ltd.
> +
> +   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 3, 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 COPYING3.  If not see
> +   <http://www.gnu.org/licenses/>.  */
> +
> +#include "subreg-live-range.h"
> +#include "selftest.h"
> +#include "print-rtl.h"
> +
> +/* class subreg_range */
> +void
> +subreg_range::dump (FILE *file) const
> +{
> +  fprintf (file, "[%d, %d)", start, end);
> +}
> +
> +/* class subreg_ranges */
> +bool
> +subreg_ranges::add_range (int max, const subreg_range &new_range)
> +{
> +  subreg_range range = new_range;
> +  if (full_p ())
> +    return false;
> +  else if (max == 1)
> +    {
> +      gcc_assert (range.start == 0 && range.end == 1);
> +      make_full ();
> +      return true;
> +    }
> +
> +  if (this->max == 1)
> +    change_max (max);
> +
> +  gcc_assert (this->max == max);
> +  gcc_assert (range.start < range.end);
> +
> +  bool changed = empty_p ();
> +  auto it = ranges.begin ();
> +  while (it != ranges.end ())
> +    {
> +      const subreg_range &r = *it;
> +      gcc_assert (r.start < r.end);
> +
> +      /* The possible positional relationship of R and RANGE.
> +	 1~5 means R.start's possible position relative to RANGE
> +	 A~G means R.end's possible position relative to RANGE
> +	 caseN means when R.start at N positon, the R.end can be in which
> +	 positions.
> +
> +		     RANGE.start     RANGE.end
> +			  [               )
> +			  |               |
> +	R.start   1       2       3       4       5
> +	R.end             |               |
> +	  case1       A   B       C       D       E
> +	  case2           |       C       D       E
> +	  case3           |           F   D       E
> +	  case4           |               |       E
> +	  case5           |               |               G
> +
> +	*/
> +
> +      /* R.start at 1 position.   */
> +      if (r.start < range.start)
> +	{
> +	  /* R.end at A position. That means R and RANGE do not overlap.  */
> +	  if (r.end < range.start)
> +	    it++;
> +	  /* R.end at B/C position. That means RANGE's left part overlap R's
> +	     right part. Expand RANGE.start to R.start and remove R.  */
> +	  else if (r.end < range.end)
> +	    {
> +	      changed = true;
> +	      range.start = r.start;
> +	      it = ranges.erase (it);
> +	    }
> +	  /* R.end at D/E position. That means R already contains RANGE, nothing
> +	     todo.  */
> +	  else
> +	    return false;
> +	}
> +      /* R.start at 2 position.  */
> +      else if (r.start == range.start)
> +	{
> +	  /* R.end at C/D position. That means RANGE contains R, remove R and
> +	     insert RANGE.  */
> +	  if (r.end < range.end)
> +	    {
> +	      changed = true;
> +	      it = ranges.erase (it);
> +	    }
> +	  /* R.end at E position. That means R already contains RANGE, nothing
> +	     todo.  */
> +	  else
> +	    return false;
> +	}
> +      /* R.start at 3 position.  */
> +      else if (r.start > range.start && r.start < range.end)
> +	{
> +	  /* R.end at F/D position. That means RANGE contains R, just remove R
> +	     and insert RANGE later.  */
> +	  if (r.end <= range.end)
> +	    {
> +	      changed = true;
> +	      it = ranges.erase (it);
> +	    }
> +	  /* R.end at E position.  That means RANGE's right part overlap R's
> +	     left part. Expand RANGE.end to R.end and remove R.  */
> +	  else if (r.end > range.end)
> +	    {
> +	      changed = true;
> +	      range.end = r.end;
> +	      it = ranges.erase (it);
> +	      break;
> +	    }
> +	}
> +      /* R.start at 4 position and R.end at E position. That means RANGE and R
> +	 are adjacent and can be merged. */
> +      else if (r.start == range.end)
> +	{
> +	  changed = true;
> +	  range.end = r.end;
> +	  it = ranges.erase (it);
> +	}
> +      /* R.start at 5 position and R.end at G position. That means R and RANGE
> +	 do not overlap.  */
> +      else
> +	break;
> +    }
> +  ranges.insert (range);
> +  return changed;
> +}
> +
> +bool
> +subreg_ranges::remove_range (int max, const subreg_range &range)
> +{
> +  if (empty_p ())
> +    return false;
> +  else if (max == 1)
> +    {
> +      gcc_assert (range.start == 0 && range.end == 1);
> +      make_empty ();
> +      return true;
> +    }
> +
> +  if (this->max == 1)
> +    {
> +      gcc_assert (full_p ());
> +      change_max (max);
> +    }
> +  gcc_assert (this->max == max);
> +  gcc_assert (range.start < range.end);
> +
> +  bool changed = false;
> +  auto it = ranges.begin ();
> +  std::set<subreg_range> new_ranges;
> +  while (it != ranges.end ())
> +    {
> +      auto &r = *it;
> +      gcc_assert (r.start < r.end);
> +
> +      /* The possible positional relationship of R and RANGE.
> +	 1~5 means R.start's possible position relative to RANGE
> +	 A~G means R.end's possible position relative to RANGE
> +	 caseN means when R.start at N positon, the R.end can be in which
> +	 positions.
> +
> +		     RANGE.start     RANGE.end
> +			  [               )
> +			  |               |
> +	R.start   1       2       3       4       5
> +	R.end             |               |
> +	  case1       A   B       C       D       E
> +	  case2           |       C       D       E
> +	  case3           |           F   D       E
> +	  case4           |               |       E
> +	  case5           |               |               G
> +
> +	*/
> +
> +      /* R.start at 1 position.  */
> +      if (r.start < range.start)
> +	{
> +	  /* R.end at A/B position. That means RANGE and R do not overlap,
> +	     nothing to remove.  */
> +	  if (r.end <= range.start)
> +	    it++;
> +	  /* R.end at C/D position. That means R's rigth part contains RANGE,
> +	     need shrink R.end to RANGE.start.  */
> +	  else if (r.end <= range.end)
> +	    {
> +	      changed = true;
> +	      new_ranges.insert (subreg_range (r.start, range.start));
> +	      it = ranges.erase (it);
> +	    }
> +	  /* R.end at E position. That means R's center part contains RANGE,
> +	     need split R to two range, one range is [R.start, RANGE.start),
> +	     another range is [RANGE.end, R.end).  */
> +	  else
> +	    {
> +	      changed = true;
> +	      new_ranges.insert (subreg_range (r.start, range.start));
> +	      new_ranges.insert (subreg_range (range.end, r.end));
> +	      it = ranges.erase (it);
> +	      break;
> +	    }
> +	}
> +      /* R.start at 2 position.  */
> +      else if (r.start == range.start)
> +	{
> +	  /* R.end at C/D position. That means RANGE contains R, remove R.  */
> +	  if (r.end <= range.end)
> +	    {
> +	      changed = true;
> +	      it = ranges.erase (it);
> +	    }
> +	  /* R.end at E position. That means R's left part contains RANGE,
> +	     shrink R.start to RANGE.end.  */
> +	  else
> +	    {
> +	      changed = true;
> +	      new_ranges.insert (subreg_range (range.end, r.end));
> +	      it = ranges.erase (it);
> +	      break;
> +	    }
> +	}
> +      /* R.start at 3 position. */
> +      else if (r.start > range.start && r.start < range.end)
> +	{
> +	  /* R.end at F/D position. That means RANGE contains R, remove R.  */
> +	  if (r.end <= range.end)
> +	    {
> +	      changed = true;
> +	      it = ranges.erase (it);
> +	    }
> +	  /* R.end at E position. That means RANGE's right part overlap R's left
> +	     part, shrink R.start to RANGE.end.  */
> +	  else
> +	    {
> +	      changed = true;
> +	      new_ranges.insert (subreg_range (range.end, r.end));
> +	      it = ranges.erase (it);
> +	      break;
> +	    }
> +	}
> +      /* R.start at 4/5 position. That means RANGE and R do not overlap.  */
> +      else
> +	break;
> +    }
> +  for (auto &r : new_ranges)
> +    add_range (this->max, r);
> +  return changed;
> +}
> +
> +bool
> +subreg_ranges::add_ranges (const subreg_ranges &sr)
> +{
> +  gcc_assert (max == sr.max || max == 1 || sr.max == 1);
> +
> +  if (full_p () || sr.empty_p ())
> +    return false;
> +  else if (sr.full_p ())
> +    {
> +      make_full ();
> +      return true;
> +    }
> +
> +  bool changed = false;
> +  for (auto &r : sr.ranges)
> +    changed |= add_range (sr.max, r);
> +  return changed;
> +}
> +
> +bool
> +subreg_ranges::remove_ranges (const subreg_ranges &sr)
> +{
> +  if (empty_p () || sr.empty_p ())
> +    return false;
> +  else if (sr.full_p ())
> +    {
> +      make_empty ();
> +      return true;
> +    }
> +
> +  gcc_assert (max == sr.max || max == 1 || sr.max == 1);
> +
> +  bool changed = false;
> +  for (auto &r : sr.ranges)
> +    changed |= remove_range (sr.max, r);
> +  return changed;
> +}
> +
> +bool
> +subreg_ranges::same_p (const subreg_ranges &sr) const
> +{
> +  if (max == 1 || sr.max == 1)
> +    return (empty_p () && sr.empty_p ()) || (full_p () && sr.full_p ());
> +  else if (max == sr.max)
> +    {
> +      if (ranges.size () != sr.ranges.size ())
> +	return false;
> +      /* Make sure that the elements in each position are the same.  */
> +      auto it1 = ranges.begin ();
> +      auto it2 = sr.ranges.begin ();
> +      while (it1 != ranges.end ())
> +	{
> +	  const subreg_range &r1 = *it1;
> +	  const subreg_range &r2 = *it2;
> +	  if (r1.start != r2.start || r1.end != r2.end)
> +	    return false;
> +	  it1++;
> +	  it2++;
> +	}
> +      return true;
> +    }
> +  else
> +    gcc_unreachable ();
> +}
> +
> +bool
> +subreg_ranges::include_ranges_p (const subreg_ranges &sr) const
> +{
> +  gcc_assert (max == sr.max || max == 1 || sr.max == 1);
> +  if (full_p ())
> +    return true;
> +  if (empty_p () && sr.empty_p ())
> +    return true;
> +  if (same_p (sr))
> +    return true;
> +
> +  for (const auto &r : sr.ranges)
> +    if (!include_range_p (sr.max, r))
> +      return false;
> +  return true;
> +}
> +
> +bool
> +subreg_ranges::include_range_p (int max, const subreg_range &range) const
> +{
> +  gcc_assert (this->max == max);
> +  for (const auto &r : ranges)
> +    {
> +      if (r.start <= range.start && r.end >= range.end)
> +	return true;
> +      else if (r.start >= range.end)
> +	return false;
> +    }
> +  return false;
> +}
> +
> +void
> +subreg_ranges::dump (FILE *file) const
> +{
> +  if (empty_p ())
> +    {
> +      fprintf (file, "empty");
> +      return;
> +    }
> +  else if (full_p ())
> +    {
> +      fprintf (file, "full");
> +      return;
> +    }
> +
> +  fprintf (file, "patial(max:%d", max);
> +  fprintf (file, " {");
> +  for (auto &range : ranges)
> +    {
> +      fprintf (file, " ");
> +      range.dump (file);
> +    }
> +  fprintf (file, " })");
> +}
> +
> +/* class subregs_live */
> +bool
> +subregs_live::copy_lives (const subregs_live &sl)
> +{
> +  bool changed = false;
> +  subregs_live temp;
> +  for (auto &kv : sl.lives)
> +    {
> +      unsigned int regno = kv.first;
> +      const subreg_ranges &sr = kv.second;
> +      if (lives.count (regno) == 0 && !sr.empty_p ())
> +	{
> +	  changed = true;
> +	  temp.add_ranges (regno, sr);
> +	}
> +      else if (lives.count (regno) != 0)
> +	{
> +	  changed |= !lives.at (regno).same_p (sr);
> +	  temp.add_ranges (regno, sr);
> +	}
> +    }
> +
> +  for (auto &kv : lives)
> +    {
> +      unsigned int regno = kv.first;
> +      subreg_ranges &sr = kv.second;
> +      if (temp.lives.count (regno) == 0 && !sr.empty_p ())
> +	changed = true;
> +    }
> +  lives = temp.lives;
> +  return changed;
> +}
> +
> +bool
> +subregs_live::add_lives (const subregs_live &sl)
> +{
> +  bool changed = false;
> +  for (auto &kv : sl.lives)
> +    {
> +      unsigned int regno = kv.first;
> +      const subreg_ranges &sr = kv.second;
> +      if (sr.empty_p ())
> +	continue;
> +
> +      if (lives.count (regno) == 0)
> +	{
> +	  changed = true;
> +	  lives.insert ({regno, sr});
> +	}
> +      else
> +	changed |= lives.at (regno).add_ranges (sr);
> +    }
> +  return changed;
> +}
> +
> +bool
> +subregs_live::remove_lives (const subregs_live &sl)
> +{
> +  bool changed = false;
> +  for (auto &kv : sl.lives)
> +    {
> +      unsigned int regno = kv.first;
> +      const subreg_ranges &sr = kv.second;
> +      if (sr.empty_p ())
> +	continue;
> +
> +      if (lives.count (regno) != 0)
> +	{
> +	  changed |= lives.at (regno).remove_ranges (sr);
> +	  if (lives.at (regno).empty_p ())
> +	    lives.erase (regno);
> +	}
> +    }
> +  return changed;
> +}
> +
> +void
> +subregs_live::dump (FILE *file, const char *indent) const
> +{
> +  if (lives.empty ())
> +    {
> +      fprintf (file, "%sempty\n", indent);
> +      return;
> +    }
> +  fprintf (file, "%s", indent);
> +  for (auto &kv : lives)
> +    {
> +      const subreg_ranges &sr = kv.second;
> +      if (sr.empty_p ())
> +	continue;
> +      fprintf (file, "%d ", kv.first);
> +      if (!sr.full_p ())
> +	{
> +	  sr.dump (file);
> +	  fprintf (file, "  ");
> +	}
> +    }
> +  fprintf (file, "\n");
> +}
> +
> +/* class live_point */
> +void
> +live_point::dump (FILE *file) const
> +{
> +  if (!use_reg.empty_p ())
> +    {
> +      fprintf (file, "use ");
> +      use_reg.dump (file);
> +      if (!def_reg.empty_p ())
> +	{
> +	  fprintf (file, ", def ");
> +	  def_reg.dump (file);
> +	}
> +    }
> +  else if (!def_reg.empty_p ())
> +    {
> +      fprintf (file, "def ");
> +      def_reg.dump (file);
> +    }
> +  else
> +    gcc_unreachable ();
> +}
> +
> +/* class live_points */
> +void
> +live_points::dump (FILE *file) const
> +{
> +  fprintf (file, "%u :", id);
> +  if (points.empty ())
> +    {
> +      fprintf (file, " empty");
> +      return;
> +    }
> +  for (const auto &kv : points)
> +    {
> +      fprintf (file, " ");
> +      kv.second.dump (file);
> +      fprintf (file, " at point %u;", kv.first);
> +    }
> +}
> +
> +/* class reg_live_ranges */
> +void
> +subregs_live_points::dump (FILE *file) const
> +{
> +  if (subreg_points.empty ())
> +    {
> +      fprintf (file, ";;     empty\n");
> +      return;
> +    }
> +  for (const auto &kv : subreg_points)
> +    {
> +      fprintf (file, ";;     ");
> +      kv.second.dump (file);
> +      fprintf (file, "\n");
> +    }
> +}
> +
> +/* Define some usefull debug functions.  */
> +
> +DEBUG_FUNCTION void
> +debug (const subreg_range &r)
> +{
> +  r.dump (stderr);
> +}
> +
> +DEBUG_FUNCTION void
> +debug (const subreg_ranges &sr)
> +{
> +  sr.dump (stderr);
> +}
> +
> +DEBUG_FUNCTION void
> +debug (const subregs_live &l)
> +{
> +  l.dump (stderr, "");
> +}
> +
> +DEBUG_FUNCTION void
> +debug (const subregs_live *l)
> +{
> +  debug (*l);
> +}
> +
> +DEBUG_FUNCTION void
> +debug (const live_point &l)
> +{
> +  l.dump (stderr);
> +}
> +
> +DEBUG_FUNCTION void
> +debug (const live_points &ls)
> +{
> +  ls.dump (stderr);
> +}
> +
> +DEBUG_FUNCTION void
> +debug (const subregs_live_points &sls)
> +{
> +  sls.dump (stderr);
> +}
> +
> +DEBUG_FUNCTION void
> +debug (const subregs_live_points *sls)
> +{
> +  debug (*sls);
> +}
> +
> +#if CHECKING_P
> +
> +namespace selftest {
> +
> +class subreg_range_tests
> +{
> +public:
> +  static void run ()
> +  {
> +    /* class subreg_range tests.  */
> +    subreg_range r1 = subreg_range (1, 2);
> +    subreg_range r2 = subreg_range (2, 3);
> +    subreg_range r3 = subreg_range (2, 3);
> +    ASSERT_FALSE (r1.same_p (r2));
> +    ASSERT_TRUE (r2.same_p (r3));
> +    ASSERT_TRUE (r1 < r2);
> +    ASSERT_FALSE (r2 < r1);
> +
> +    /* class subreg_ranges tests.  */
> +  }
> +};
> +
> +void
> +subreg_live_range_tests ()
> +{
> +  subreg_range_tests::run ();
> +}
> +
> +} // namespace selftest
> +
> +#endif /* CHECKING_P */
> diff --git a/gcc/subreg-live-range.h b/gcc/subreg-live-range.h
> new file mode 100644
> index 00000000000..76e442d08e8
> --- /dev/null
> +++ b/gcc/subreg-live-range.h
> @@ -0,0 +1,333 @@
> +/* SUBREG live range track classes for DF & IRA & LRA.
> +   Copyright (C) 2023 Free Software Foundation, Inc.
> +   Contributed by Lehua Ding (lehua.ding@rivai.ai), RiVAI Technologies Ltd.
> +
> +   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 3, 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 COPYING3.  If not see
> +   <http://www.gnu.org/licenses/>.  */
> +
> +#ifndef GCC_SUBREG_LIVE_RANGE_H
> +#define GCC_SUBREG_LIVE_RANGE_H
> +
> +#include "config.h"
> +#include "system.h"
> +#include "coretypes.h"
> +#include <set>
> +#include <map>
> +
> +/* class subreg_range represent bytes range [start, end) of a reg.  */
> +class subreg_range
> +{
> +public:
> +  int start; /* Range start point.  */
> +  int end;   /* Range start point.  */
> +
> +  subreg_range (int start, int end) : start (start), end (end)
> +  {
> +    gcc_assert (start < end);
> +  }
> +
> +  /* For sorting.  */
> +  bool operator<(const subreg_range &r) const
> +  {
> +    if (end <= r.start)
> +      return true;
> +    else if (start >= r.end)
> +      return false;
> +    else
> +      /* Cannot sorting for overlap range.  */
> +      gcc_unreachable ();
> +  }
> +  /* Return true if R same with self.  */
> +  bool same_p (const subreg_range &r) const
> +  {
> +    return start == r.start && end == r.end;
> +  }
> +
> +  /* Return true if range is full for 0-MAX range.  */
> +  bool full_p (int max) const { return start == 0 && end == max; }
> +
> +  /* Debug methods.  */
> +  void dump (FILE *file) const;
> +};
> +
> +/* class subreg_ranges represent multiple disjoint and discontinuous
> +   subreg_range.  */
> +class subreg_ranges
> +{
> +public:
> +  /* The maximum boundary value of range. If for a unknown mode hard register,
> +     the max set to 1.  */
> +  int max;
> +  std::set<subreg_range> ranges;
> +
> +  subreg_ranges () : max (1) {}
> +  subreg_ranges (int max) : max (max) { gcc_assert (max >= 1); }
> +
> +  /* Modify ranges.  */
> +  /* Return true if ranges changed.  */
> +  bool add_range (int max, const subreg_range &range);
> +  /* Return true if ranges changed.  */
> +  bool remove_range (int max, const subreg_range &range);
> +  /* Add SR, return true if ranges changed.  */
> +  bool add_ranges (const subreg_ranges &sr);
> +  /* Clear ranges of SR, return true if ranges changed.  */
> +  bool remove_ranges (const subreg_ranges &sr);
> +  /* Make range empty.  */
> +  void make_empty () { ranges.clear (); }
> +  /* Make range full.  */
> +  void make_full ()
> +  {
> +    make_empty ();
> +    ranges.insert (subreg_range (0, max));
> +  }
> +  /* Change max to MAX, corresponding adjust ranges.  */
> +  void change_max (int max)
> +  {
> +    gcc_assert (this->max == 1);
> +    this->max = max;
> +    if (full_p ())
> +      make_full ();
> +  }
> +
> +  /* Predicators.  */
> +  bool full_p () const
> +  {
> +    if (ranges.size () != 1)
> +      return false;
> +    const subreg_range &r = *ranges.begin ();
> +    return r.start == 0 && r.end == max;
> +  }
> +  bool empty_p () const { return ranges.empty (); }
> +  bool same_p (const subreg_ranges &sr) const;
> +  bool same_p (int max, const subreg_range &range) const
> +  {
> +    subreg_ranges sr = subreg_ranges (max);
> +    sr.add_range (max, range);
> +    return same_p (sr);
> +  }
> +  bool include_ranges_p (const subreg_ranges &sr) const;
> +  bool include_range_p (int max, const subreg_range &range) const;
> +
> +  /* Debug methods.  */
> +  void dump (FILE *file) const;
> +};
> +
> +/* class subregs_live record the live subreg_ranges of registers.  */
> +class subregs_live
> +{
> +public:
> +  /* The key is usually the register's regno.  */
> +  std::map<unsigned int, subreg_ranges> lives;
> +
> +  /* Add/clear live range.  */
> +  bool add_range (unsigned int regno, int max, const subreg_range &range)
> +  {
> +    if (lives.count (regno) == 0)
> +      lives.insert ({regno, subreg_ranges (max)});
> +    return lives.at (regno).add_range (max, range);
> +  }
> +  bool remove_range (unsigned int regno, int max, const subreg_range &range)
> +  {
> +    if (lives.count (regno) != 0)
> +      {
> +	bool changed = lives.at (regno).remove_range (max, range);
> +	if (lives.at (regno).empty_p ())
> +	  remove_live (regno);
> +	return changed;
> +      }
> +    return false;
> +  }
> +  /* Add a unexist register live range.  */
> +  void add_ranges (unsigned int regno, const subreg_ranges &ranges)
> +  {
> +    if (lives.count (regno) == 0)
> +      lives.insert ({regno, ranges});
> +    else
> +      lives.at (regno).add_ranges (ranges);
> +  }
> +  bool copy_lives (const subregs_live &sl);
> +  bool add_lives (const subregs_live &sl);
> +  bool remove_lives (const subregs_live &sl);
> +  void remove_live (unsigned int regno) { lives.erase (regno); }
> +  /* Remove all register live range.  */
> +  void clear () { lives.clear (); }
> +  void clear (unsigned min_regno)
> +  {
> +    if (lives.lower_bound (min_regno) != lives.end ())
> +      lives.erase (lives.lower_bound (min_regno), lives.end ());
> +  }
> +
> +  /* Return true if regno's live range is full.  */
> +  bool full_p (unsigned int regno) const
> +  {
> +    return lives.count (regno) != 0 && lives.at (regno).full_p ();
> +  }
> +  /* Return true if regno's live range is empty.  */
> +  bool empty_p (unsigned int regno) const
> +  {
> +    return lives.count (regno) == 0 || lives.at (regno).empty_p ();
> +  }
> +  /* Return true if SL same with this.  */
> +  bool same_p (const subregs_live &sl)
> +  {
> +    if (lives.size () != sl.lives.size ())
> +      return false;
> +    for (auto &kv : lives)
> +      {
> +	unsigned int regno = kv.first;
> +	if (sl.empty_p (regno))
> +	  return false;
> +	const subreg_ranges &sr = kv.second;
> +	if (!sr.same_p (sl.lives.at (regno)))
> +	  return false;
> +      }
> +    return true;
> +  }
> +
> +  /* Debug methods.  */
> +  void dump (FILE *file, const char *indent = ";;     ") const;
> +};
> +
> +class live_point
> +{
> +public:
> +  int point;
> +  /* subreg range be defined in current point.  */
> +  subreg_ranges def_reg;
> +  /* subreg range be used in current point.  */
> +  subreg_ranges use_reg;
> +
> +  live_point (int max, const subreg_range &range, bool is_def)
> +    : def_reg (max), use_reg (max)
> +  {
> +    add_range (max, range, is_def);
> +  }
> +  live_point (const subreg_ranges &sr, bool is_def)
> +    : def_reg (sr.max), use_reg (sr.max)
> +  {
> +    add_ranges (sr, is_def);
> +  }
> +  live_point (int point, int max) : point (point), def_reg (max), use_reg (max)
> +  {}
> +
> +  void add_range (int max, const subreg_range &r, bool is_def)
> +  {
> +    if (is_def)
> +      def_reg.add_range (max, r);
> +    else
> +      use_reg.add_range (max, r);
> +  }
> +
> +  void add_ranges (const subreg_ranges &sr, bool is_def)
> +  {
> +    if (is_def)
> +      def_reg.add_ranges (sr);
> +    else
> +      use_reg.add_ranges (sr);
> +  }
> +
> +  void dump (FILE *file) const;
> +};
> +
> +class live_points
> +{
> +public:
> +  int id;
> +  int max;
> +  std::map<int, live_point> points;
> +
> +  live_points (int id, int max) : id (id), max (max) {}
> +
> +  void add_point (int max, const subreg_range &range, bool is_def, int point)
> +  {
> +    gcc_assert (this->max == max || this->max == 1 || max == 1);
> +    if (points.count (point) == 0)
> +      points.insert ({point, {max, range, is_def}});
> +    else
> +      points.at (point).add_range (max, range, is_def);
> +  }
> +  void dump (FILE *file) const;
> +};
> +
> +class subregs_live_points
> +{
> +public:
> +  std::map<int, live_points> subreg_points;
> +  std::map<int, int> last_start_points;
> +  std::map<int, subreg_ranges> subreg_live_ranges;
> +
> +  void add_point (int id, int max, const subreg_range &range, bool is_def,
> +		  int point)
> +  {
> +    if (!is_def && empty_live_p (id))
> +      {
> +	if (last_start_points.count (id) == 0)
> +	  last_start_points.insert ({id, point});
> +	else
> +	  last_start_points.at (id) = point;
> +      }
> +
> +    if (subreg_points.count (id) == 0)
> +      subreg_points.insert ({id, live_points (id, max)});
> +
> +    subreg_points.at (id).add_point (max, range, is_def, point);
> +
> +    if (subreg_live_ranges.count (id) == 0)
> +      subreg_live_ranges.insert ({id, subreg_ranges (max)});
> +
> +    if (is_def)
> +      subreg_live_ranges.at (id).remove_range (max, range);
> +    else
> +      subreg_live_ranges.at (id).add_range (max, range);
> +  }
> +
> +  void add_range (int id, int max, const subreg_range &range, bool is_def)
> +  {
> +    if (subreg_live_ranges.count (id) == 0)
> +      subreg_live_ranges.insert ({id, subreg_ranges (max)});
> +
> +    if (is_def)
> +      subreg_live_ranges.at (id).remove_range (max, range);
> +    else
> +      subreg_live_ranges.at (id).add_range (max, range);
> +  }
> +
> +  bool full_live_p (int id)
> +  {
> +    return subreg_live_ranges.count (id) != 0
> +	   && subreg_live_ranges.at (id).full_p ();
> +  }
> +
> +  bool empty_live_p (int id)
> +  {
> +    return subreg_live_ranges.count (id) == 0
> +	   || subreg_live_ranges.at (id).empty_p ();
> +  }
> +
> +  int get_start_point (int id)
> +  {
> +    int start_point = last_start_points.at (id);
> +    gcc_assert (start_point != -1);
> +    return start_point;
> +  }
> +
> +  void clear_live_ranges () { subreg_live_ranges.clear (); }
> +
> +  /* Debug methods.  */
> +  void dump (FILE *file) const;
> +};
> +
> +#endif /* GCC_SUBREG_LIVE_RANGE_H */
> diff --git a/gcc/timevar.def b/gcc/timevar.def
> index d21b08c030d..7c173d3c7c8 100644
> --- a/gcc/timevar.def
> +++ b/gcc/timevar.def
> @@ -120,6 +120,7 @@ DEFTIMEVAR (TV_DF_SCAN		     , "df scan insns")
>  DEFTIMEVAR (TV_DF_MD		     , "df multiple defs")
>  DEFTIMEVAR (TV_DF_RD		     , "df reaching defs")
>  DEFTIMEVAR (TV_DF_LR		     , "df live regs")
> +DEFTIMEVAR (TV_DF_LIVE_SUBREG	     , "df live subregs")
>  DEFTIMEVAR (TV_DF_LIVE		     , "df live&initialized regs")
>  DEFTIMEVAR (TV_DF_MIR		     , "df must-initialized regs")
>  DEFTIMEVAR (TV_DF_CHAIN		     , "df use-def / def-use chains")