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Re: PING^(n+1) fwprop merge (ping 6 or 7 by now)


On Sunday 07 May 2006 22:04, Ian Lance Taylor wrote:
> > +/* Return a pointer to one of the occurrences of FIND in *PX.  */
> > +
> > +rtx *
> > +find_occurrence (rtx *px, rtx find)
>
> I think it would be preferable to write this in terms for
> for_each_rtx, unless there is some reason not to.

As I said in a previous mail, I don't think we can do this because
we need to have the address of an rtx returned and I don't see how
we can do that with for_each_rtx.

> > +  /* Allow this function to work in EXPR_LISTs.  */
>
> No need for the comment--I would take it out. 

Done.

> I count six uses of DF_INSN_UID_GET in df-core.c.  You are fixing
> three of them.  Is there any reason not to fix the other three?

I've looked at this df-core.c change and found that we should have
a different fix.  That fix is now already in mainline.

FWIW we only had to fix three because those are the only three places
where we walk an insn chain (using FOR_BB_INSN*).

> > +static bool
> > +can_simplify_addr (rtx addr)
> > +{
> > +  rtx reg;
> > +
> > +  if (GET_CODE (addr) == PLUS)
> > +    reg = XEXP (addr, 0);
> > +  else
> > +    reg = addr;
> > +
> > +  return !REG_P (reg)
> > +	 || (REGNO (reg) > FIRST_PSEUDO_REGISTER
> > +	     && REGNO (reg) != FRAME_POINTER_REGNUM
> > +	     && REGNO (reg) != HARD_FRAME_POINTER_REGNUM
> > +	     && REGNO (reg) != ARG_POINTER_REGNUM);
> > +}
>
> This can't be right.  FRAME_POINTER_REGNUM, HARD_FRAME_POINTER_REGNUM,
> and ARG_POINTER_REGNUM are always < FIRST_PSEUDO_REGISTER.
>
> The test against FIRST_PSEUDO_REGISTER should be >=, not >.  Better
> would be to use HARD_REGISTER_P.
>
> There should be a parenthesis around the whole expression.

Done.

> Perhaps this is intended to be
>   return (!REG_P (reg)
>
> 	  || (!HARD_REGISTER_P (reg)
> 	  ||
> 	      || (REGNO (reg) != FRAME_POINTER_REGNUM
>
> 		  && REGNO (reg) != HARD_FRAME_POINTER_REGNUM
> 		  && REGNO (reg) != ARG_POINTER_REGNUM)));
> which can be simplified to
>   return (!REG_P (reg)
>
> 	  || (REGNO (reg) != FRAME_POINTER_REGNUM
>
> 	      && REGNO (reg) != HARD_FRAME_POINTER_REGNUM
> 	      && REGNO (reg) != ARG_POINTER_REGNUM));
>
> Of course such a change would have to be retested.
>
> In general this looks like an attempt to rewrite the test near the
> start of find_best_addr in cse.c.  If that is the case, why is it OK
> to not test CONSTANT_ADDRESS_P?

I believe we should test CONSTANT_ADDRESS_P too.  We can't simplify a
CONSTANT_ADDRESS_P address if doc/tm.texi is right.

So that whole function now looks like this:

static bool
can_simplify_addr (rtx addr)
{
  rtx reg;

  if (CONSTANT_ADDRESS_P (addr))
    return false;

  if (GET_CODE (addr) == PLUS)
    reg = XEXP (addr, 0);
  else
    reg = addr;

  return (!REG_P (reg)
          || (REGNO (reg) != FRAME_POINTER_REGNUM
              && REGNO (reg) != HARD_FRAME_POINTER_REGNUM
              && REGNO (reg) != ARG_POINTER_REGNUM));
}


> > +/* Returns a canonical version of X for the address, from the point of
> > view, +   that all multiplications are represented as MULT instead of the
> > multiply +   by a power of 2 being represented as ASHIFT.
> > +
> > +   Every ASHIFT we find has been made by simplify_gen_binary and was not
> > +   there before, so it is not shared.  So we can do this in place.  */
>
> How can you be sure of that?  Doesn't that assume that no target will
> use ASHIFT when representing an address?

The assumption was that ASHIFT in an address is not canonical.  However,
cse.c:canon_for_address uses gen_rtx_MULT.  I have no strong feelings
either way, but modifying in place works.  Generating a new RTX is a bit
cleaner perhaps.  I'll change this if you think that is better.  For now
I haven't changed it.


> > +/* Inside INSN, the expression rooted at *LOC has been changed, moving
> > some +   uses from ORIG_USES.  Find those that are present, and create
> > new items +   in the data flow object of the pass.  Mark any new uses as
> > having the +   given TYPE.  */
> > +static void
> > +update_df (rtx insn, rtx *loc, struct df_ref *orig_uses, enum
> > df_ref_type type, +	   int new_flags)
> > +{
> > +  struct df_ref *use;
> > +
> > +  /* Else, add a use for the registers that were propagated.  */
>
> Why "Else"?

Typo.  Fixed.


> > +/* Try substituting NEW into LOC, which originated from forward
> > propagation +   of USE's value from NEW_DEF_INSN.  SET_REG_EQUAL says
> > whether we are +   substituting the whole SET_SRC, so we can set a
> > REG_EQUAL note if the +   new insn is not recognized.  Return whether the
> > substitution was +   performed.  */
> > +
> > +static bool
> > +subst (struct df_ref *use, rtx *loc, rtx new, rtx def_insn, bool
> > set_reg_equal)
>
> I think the name "subst" is too generic, and in particular combine.c
> has a function named "subst".  Please use a different name.

It is now called try_fwprop_subst.

So this is the first part of the changes.  The second bits that clean
up cse.c are unchanged.  I have only tested this with a C bootstrap on
x86-linux, but I'll give it a full run tomorrow and if it passes, I'll
post it as an RFT.  I'm posting this now because if there's anything
you spot right away, I can make the changes _before_ spending another
full day of computer cycles on testing ;-)

Gr.
Steven


	* Makefile.in: Add fwprop.o.
	* common.opt (-fforward-propagate): New.
	* fwprop.c: New file.
	* opts.c (decode_options): Don't enable CSE path following by default.
	Enable forward propagation at -O2.
	* passes.c (init_optimization_passes): Schedule forward propagation.
	* rtl.h (find_occurrence): Declare.
	* rtlanal.c (find_occurrence): New.
	(loc_mentioned_in_p): Support NULL value of the second parameter.
	* timevar.def (TV_FWPROP): New.
	* tree-pass.h (pass_rtl_fwprop, pass_rtl_fwprop_with_addr): New.

	* doc/invoke.texi (Optimization Options): Document fwprop.

Index: doc/invoke.texi
===================================================================
--- doc/invoke.texi	(revision 113736)
+++ doc/invoke.texi	(working copy)
@@ -310,7 +310,7 @@ Objective-C and Objective-C++ Dialects}.
 -fcse-skip-blocks  -fcx-limited-range  -fdata-sections @gol
 -fdelayed-branch  -fdelete-null-pointer-checks -fearly-inlining @gol
 -fexpensive-optimizations  -ffast-math  -ffloat-store @gol
--fforce-addr  -ffunction-sections @gol
+-fforce-addr  -fforward-propagate  -ffunction-sections @gol
 -fgcse  -fgcse-lm  -fgcse-sm  -fgcse-las  -fgcse-after-reload @gol
 -fcrossjumping  -fif-conversion  -fif-conversion2 @gol
 -finline-functions  -finline-functions-called-once @gol
@@ -4565,6 +4565,16 @@ register-load. This option is now a nop 
 Force memory address constants to be copied into registers before
 doing arithmetic on them.
 
+@item -fforward-propagate
+@opindex fforward-propagate
+Perform a forward propagation pass on RTL, which try to combine two
+instructions and see if the result can be simplified.  If loop unrolling
+is active, two passes are performed and the second is scheduled after
+loop unrolling.
+
+This option is enabled by default at optimization levels @option{-O2},
+@option{-O3}, @option{-Os}.
+
 @item -fomit-frame-pointer
 @opindex fomit-frame-pointer
 Don't keep the frame pointer in a register for functions that
Index: tree-pass.h
===================================================================
--- tree-pass.h	(revision 113736)
+++ tree-pass.h	(working copy)
@@ -330,6 +330,8 @@ extern struct tree_opt_pass pass_rtl_eh;
 extern struct tree_opt_pass pass_initial_value_sets;
 extern struct tree_opt_pass pass_unshare_all_rtl;
 extern struct tree_opt_pass pass_instantiate_virtual_regs;
+extern struct tree_opt_pass pass_rtl_fwprop;
+extern struct tree_opt_pass pass_rtl_fwprop_addr;
 extern struct tree_opt_pass pass_jump2;
 extern struct tree_opt_pass pass_cse;
 extern struct tree_opt_pass pass_gcse;
Index: rtlanal.c
===================================================================
--- rtlanal.c	(revision 113736)
+++ rtlanal.c	(working copy)
@@ -552,6 +552,68 @@ count_occurrences (rtx x, rtx find, int 
     }
   return count;
 }
+
+/* Return a pointer to one of the occurrences of FIND in *PX.  */
+
+rtx *
+find_occurrence (rtx *px, rtx find)
+{
+  int i, j;
+  enum rtx_code code;
+  const char *format_ptr;
+  rtx x = *px;
+
+  if (x == find)
+    return px;
+
+  code = GET_CODE (x);
+  switch (code)
+    {
+    case REG:
+    case CONST_INT:
+    case CONST_DOUBLE:
+    case CONST_VECTOR:
+    case SYMBOL_REF:
+    case CODE_LABEL:
+    case PC:
+    case CC0:
+      return NULL;
+
+    case MEM:
+      if (MEM_P (find) && rtx_equal_p (x, find))
+	return px;
+      break;
+
+    default:
+      break;
+    }
+
+  format_ptr = GET_RTX_FORMAT (code);
+
+  for (i = 0; i < GET_RTX_LENGTH (code); i++)
+    {
+      rtx *result;
+      switch (*format_ptr++)
+	{
+	case 'e':
+	  result = find_occurrence (&XEXP (x, i), find);
+	  if (result)
+	    return result;
+	  break;
+
+	case 'E':
+	  for (j = 0; j < XVECLEN (x, i); j++)
+	    {
+	      result = find_occurrence (&XVECEXP (x, i, j), find);
+	      if (result)
+	        return result;
+	    }
+	  break;
+	}
+    }
+
+  return 0;
+}
 
 /* Nonzero if register REG appears somewhere within IN.
    Also works if REG is not a register; in this case it checks
@@ -2847,10 +2909,15 @@ auto_inc_p (rtx x)
 int
 loc_mentioned_in_p (rtx *loc, rtx in)
 {
-  enum rtx_code code = GET_CODE (in);
-  const char *fmt = GET_RTX_FORMAT (code);
+  enum rtx_code code;
+  const char *fmt;
   int i, j;
 
+  if (!in)
+    return 0;
+
+  code = GET_CODE (in);
+  fmt = GET_RTX_FORMAT (code);
   for (i = GET_RTX_LENGTH (code) - 1; i >= 0; i--)
     {
       if (loc == &in->u.fld[i].rt_rtx)
Index: opts.c
===================================================================
--- opts.c	(revision 113736)
+++ opts.c	(working copy)
@@ -559,8 +559,7 @@ decode_options (unsigned int argc, const
       flag_thread_jumps = 1;
       flag_crossjumping = 1;
       flag_optimize_sibling_calls = 1;
-      flag_cse_follow_jumps = 1;
-      flag_cse_skip_blocks = 1;
+      flag_forward_propagate = 1;
       flag_gcse = 1;
       flag_expensive_optimizations = 1;
       flag_ipa_type_escape = 1;
Index: timevar.def
===================================================================
--- timevar.def	(revision 113736)
+++ timevar.def	(working copy)
@@ -128,6 +128,7 @@ DEFTIMEVAR (TV_TEMPLATE_INSTANTIATION, "
 DEFTIMEVAR (TV_EXPAND		     , "expand")
 DEFTIMEVAR (TV_VARCONST              , "varconst")
 DEFTIMEVAR (TV_JUMP                  , "jump")
+DEFTIMEVAR (TV_FWPROP                , "forward prop")
 DEFTIMEVAR (TV_CSE                   , "CSE")
 DEFTIMEVAR (TV_LOOP                  , "loop analysis")
 DEFTIMEVAR (TV_GCSE                  , "global CSE")
Index: common.opt
===================================================================
--- common.opt	(revision 113736)
+++ common.opt	(working copy)
@@ -440,6 +440,10 @@ fforce-mem
 Common Report Var(flag_force_mem)
 Copy memory operands into registers before use
 
+fforward-propagate
+Common Report Var(flag_forward_propagate)
+Perform a forward propagation pass on RTL
+
 ; Nonzero means don't put addresses of constant functions in registers.
 ; Used for compiling the Unix kernel, where strange substitutions are
 ; done on the assembly output.
Index: rtl.h
===================================================================
--- rtl.h	(revision 113736)
+++ rtl.h	(working copy)
@@ -1683,6 +1683,7 @@ extern HOST_WIDE_INT get_integer_term (r
 extern rtx get_related_value (rtx);
 extern int reg_mentioned_p (rtx, rtx);
 extern int count_occurrences (rtx, rtx, int);
+extern rtx *find_occurrence (rtx *, rtx);
 extern int reg_referenced_p (rtx, rtx);
 extern int reg_used_between_p (rtx, rtx, rtx);
 extern int reg_set_between_p (rtx, rtx, rtx);
Index: Makefile.in
===================================================================
--- Makefile.in	(revision 113736)
+++ Makefile.in	(working copy)
@@ -983,7 +983,7 @@ OBJS-common = \
  debug.o df-core.o df-problems.o df-scan.o dfp.o diagnostic.o dojump.o     \
  dominance.o loop-doloop.o	   					   \
  dwarf2asm.o dwarf2out.o emit-rtl.o except.o explow.o loop-iv.o		   \
- expmed.o expr.o final.o flow.o fold-const.o function.o gcse.o		   \
+ expmed.o expr.o final.o flow.o fold-const.o function.o fwprop.o gcse.o	   \
  genrtl.o ggc-common.o global.o graph.o gtype-desc.o			   \
  haifa-sched.o hooks.o ifcvt.o insn-attrtab.o insn-emit.o insn-modes.o	   \
  insn-extract.o insn-opinit.o insn-output.o insn-peep.o insn-recog.o	   \
@@ -2311,12 +2311,15 @@ cse.o : cse.c $(CONFIG_H) $(SYSTEM_H) co
    hard-reg-set.h $(FLAGS_H) insn-config.h $(RECOG_H) $(EXPR_H) toplev.h \
    output.h $(FUNCTION_H) $(BASIC_BLOCK_H) $(GGC_H) $(TM_P_H) $(TIMEVAR_H) \
    except.h $(TARGET_H) $(PARAMS_H) rtlhooks-def.h tree-pass.h $(REAL_H)
+fwprop.o : fwprop.c $(CONFIG_H) $(SYSTEM_H) coretypes.h $(TM_H) $(RTL_H) \
+   toplev.h insn-config.h $(RECOG_H) $(FLAGS_H) $(OBSTACK_H) $(BASIC_BLOCK_H) \
+   output.h $(DF_H) alloc-pool.h $(TIMEVAR_H) tree-pass.h
 web.o : web.c $(CONFIG_H) $(SYSTEM_H) coretypes.h $(TM_H) $(RTL_H) \
    hard-reg-set.h $(FLAGS_H) $(BASIC_BLOCK_H) $(FUNCTION_H) output.h toplev.h \
    $(DF_H) $(OBSTACK_H) timevar.h tree-pass.h
 see.o : see.c $(CONFIG_H) $(SYSTEM_H) coretypes.h $(TM_H) $(RTL_H) \
    hard-reg-set.h $(FLAGS_H) $(BASIC_BLOCK_H) function.h output.h toplev.h \
-   $(DF_H) $(OBSTACK_H) timevar.h tree-pass.h
+   $(DF_H) $(OBSTACK_H) $(TIMEVAR_H) tree-pass.h
 gcse.o : gcse.c $(CONFIG_H) $(SYSTEM_H) coretypes.h $(TM_H) $(RTL_H) \
    $(REGS_H) hard-reg-set.h $(FLAGS_H) $(REAL_H) insn-config.h $(GGC_H) \
    $(RECOG_H) $(EXPR_H) $(BASIC_BLOCK_H) $(FUNCTION_H) output.h toplev.h \
Index: passes.c
===================================================================
--- passes.c	(revision 113736)
+++ passes.c	(working copy)
@@ -635,6 +635,7 @@ init_optimization_passes (void)
   NEXT_PASS (pass_instantiate_virtual_regs);
   NEXT_PASS (pass_jump2);
   NEXT_PASS (pass_cse);
+  NEXT_PASS (pass_rtl_fwprop);
   NEXT_PASS (pass_gcse);
   NEXT_PASS (pass_jump_bypass);
   NEXT_PASS (pass_rtl_ifcvt);
@@ -645,6 +646,7 @@ init_optimization_passes (void)
   NEXT_PASS (pass_loop2);
   NEXT_PASS (pass_web);
   NEXT_PASS (pass_cse2);
+  NEXT_PASS (pass_rtl_fwprop_addr);
   NEXT_PASS (pass_life);
   NEXT_PASS (pass_combine);
   NEXT_PASS (pass_if_after_combine);
Index: fwprop.c
===================================================================
--- fwprop.c	(revision 0)
+++ fwprop.c	(revision 0)
@@ -0,0 +1,976 @@
+/* RTL-based forward propagation pass for GNU compiler.
+   Copyright (C) 2005, 2006 Free Software Foundation, Inc.
+   Contributed by Paolo Bonzini and Steven Bosscher.
+
+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 "toplev.h"
+
+#include "timevar.h"
+#include "rtl.h"
+#include "tm_p.h"
+#include "emit-rtl.h"
+#include "insn-config.h"
+#include "recog.h"
+#include "flags.h"
+#include "obstack.h"
+#include "basic-block.h"
+#include "output.h"
+#include "df.h"
+#include "target.h"
+#include "cfgloop.h"
+#include "tree-pass.h"
+
+
+/* This pass does simple forward propagation and simplification when an
+   operand of an insn can only come from a single def.  This pass uses
+   df.c, so it is global.  However, we only do limited analysis of
+   available expressions.
+
+   1) The pass tries to propagate the source of the def into the use,
+   and checks if the result is independent of the substituted value.
+   For example, the high word of a (zero_extend:DI (reg:SI M)) is always
+   zero, independent of the source register.
+
+   In particular, we propagate constants into the use site.  Sometimes
+   RTL expansion did not put the constant in the same insn on purpose,
+   to satisfy a predicate, and the result will fail to be recognized;
+   but this happens rarely and in this case we can still create a
+   REG_EQUAL note.  For multi-word operations, this
+
+      (set (subreg:SI (reg:DI 120) 0) (const_int 0))
+      (set (subreg:SI (reg:DI 120) 4) (const_int -1))
+      (set (subreg:SI (reg:DI 122) 0)
+         (ior:SI (subreg:SI (reg:DI 119) 0) (subreg:SI (reg:DI 120) 0)))
+      (set (subreg:SI (reg:DI 122) 4)
+         (ior:SI (subreg:SI (reg:DI 119) 4) (subreg:SI (reg:DI 120) 4)))
+
+   can be simplified to the much simpler
+
+      (set (subreg:SI (reg:DI 122) 0) (subreg:SI (reg:DI 119)))
+      (set (subreg:SI (reg:DI 122) 4) (const_int -1))
+
+   This particular propagation is also effective at putting together
+   complex addressing modes.  We are more aggressive inside MEMs, in
+   that all definitions are propagated if the use is in a MEM; if the
+   result is a valid memory address we check address_cost to decide
+   whether the substitution is worthwhile.
+
+   2) The pass propagates register copies.  This is not as effective as
+   the copy propagation done by CSE's canon_reg, which works by walking
+   the instruction chain, it can help the other transformations.
+
+   We should consider removing this optimization, and instead reorder the
+   RTL passes, because GCSE does this transformation too.  With some luck,
+   the CSE pass at the end of rest_of_handle_gcse could also go away.
+
+   3) The pass looks for paradoxical subregs that are actually unnecessary.
+   Things like this:
+
+     (set (reg:QI 120) (subreg:QI (reg:SI 118) 0))
+     (set (reg:QI 121) (subreg:QI (reg:SI 119) 0))
+     (set (reg:SI 122) (plus:SI (subreg:SI (reg:QI 120) 0)
+                                (subreg:SI (reg:QI 121) 0)))
+
+   are very common on machines that can only do word-sized operations.
+   For each use of a paradoxical subreg (subreg:WIDER (reg:NARROW N) 0),
+   if it has a single def and it is (subreg:NARROW (reg:WIDE M) 0),
+   we can replace the paradoxical subreg with simply (reg:WIDE M).  The
+   above will simplify this to
+
+     (set (reg:QI 120) (subreg:QI (reg:SI 118) 0))
+     (set (reg:QI 121) (subreg:QI (reg:SI 119) 0))
+     (set (reg:SI 122) (plus:SI (reg:SI 118) (reg:SI 119)))
+
+   where the first two insns are now dead.  */
+
+
+static struct loops loops;
+static struct df *df;
+static int num_changes;
+
+
+/* Do not try to replace constant addresses or addresses of local and
+   argument slots.  These MEM expressions are made only once and inserted
+   in many instructions, as well as being used to control symbol table
+   output.  It is not safe to clobber them.
+
+   There are some uncommon cases where the address is already in a register
+   for some reason, but we cannot take advantage of that because we have
+   no easy way to unshare the MEM.  In addition, looking up all stack
+   addresses is costly.  */
+
+static bool
+can_simplify_addr (rtx addr)
+{
+  rtx reg;
+
+  if (CONSTANT_ADDRESS_P (addr))
+    return false;
+
+  if (GET_CODE (addr) == PLUS)
+    reg = XEXP (addr, 0);
+  else
+    reg = addr;
+
+  return (!REG_P (reg)
+	  || (REGNO (reg) != FRAME_POINTER_REGNUM
+	      && REGNO (reg) != HARD_FRAME_POINTER_REGNUM
+	      && REGNO (reg) != ARG_POINTER_REGNUM));
+}
+
+/* Returns a canonical version of X for the address, from the point of view,
+   that all multiplications are represented as MULT instead of the multiply
+   by a power of 2 being represented as ASHIFT.
+
+   Every ASHIFT we find has been made by simplify_gen_binary and was not
+   there before, so it is not shared.  So we can do this in place.  */
+
+static void
+canonicalize_address (rtx x)
+{
+  for (;;)
+    switch (GET_CODE (x))
+      {
+      case ASHIFT:
+        if (GET_CODE (XEXP (x, 1)) == CONST_INT
+            && INTVAL (XEXP (x, 1)) < GET_MODE_BITSIZE (GET_MODE (x))
+            && INTVAL (XEXP (x, 1)) >= 0)
+	  {
+	    HOST_WIDE_INT shift = INTVAL (XEXP (x, 1));
+	    PUT_CODE (x, MULT);
+	    XEXP (x, 1) = gen_int_mode ((HOST_WIDE_INT) 1 << shift,
+					GET_MODE (x));
+	  }
+
+	x = XEXP (x, 0);
+        break;
+
+      case PLUS:
+        if (GET_CODE (XEXP (x, 0)) == PLUS
+	    || GET_CODE (XEXP (x, 0)) == ASHIFT
+	    || GET_CODE (XEXP (x, 0)) == CONST)
+	  canonicalize_address (XEXP (x, 0));
+
+	x = XEXP (x, 1);
+        break;
+
+      case CONST:
+	x = XEXP (x, 0);
+        break;
+
+      default:
+        return;
+      }
+}
+
+/* OLD is a memory address.  Return whether it is good to use NEW instead,
+   for a memory access in the given MODE.  */
+
+static bool
+should_replace_address (rtx old, rtx new, enum machine_mode mode)
+{
+  int gain;
+
+  if (rtx_equal_p (old, new) || !memory_address_p (mode, new))
+    return false;
+
+  /* Copy propagation is always ok.  */
+  if (REG_P (old) && REG_P (new))
+    return true;
+
+  /* Prefer the new address if it is less expensive.  */
+  gain = address_cost (old, mode) - address_cost (new, mode);
+
+  /* If the addresses have equivalent cost, prefer the new address
+     if it has the highest `rtx_cost'.  That has the potential of
+     eliminating the most insns without additional costs, and it
+     is the same that cse.c used to do.  */
+  if (gain == 0)
+    gain = rtx_cost (new, SET) - rtx_cost (old, SET);
+
+  return (gain > 0);
+}
+
+/* Replace all occurrences of OLD in *PX with NEW and try to simplify the
+   resulting expression.  Replace *PX with a new RTL expression if an
+   occurrence of OLD was found.
+
+   If CAN_APPEAR is true, we always return true; if it is false, we
+   can return false if, for at least one occurrence OLD, we failed to
+   collapse the result to a constant.  For example, (mult:M (reg:M A)
+   (minus:M (reg:M B) (reg:M A))) may collapse to zero if replacing
+   (reg:M B) with (reg:M A).
+
+   CAN_APPEAR is disregarded inside MEMs: in that case, we always return
+   true if the simplification is a cheaper and valid memory address.
+
+   This is only a wrapper around simplify-rtx.c: do not add any pattern
+   matching code here.  (The sole exception is the handling of LO_SUM, but
+   that is because there is no simplify_gen_* function for LO_SUM).  */
+
+static bool
+propagate_rtx_1 (rtx *px, rtx old, rtx new, bool can_appear)
+{
+  rtx x = *px, tem = NULL_RTX, op0, op1, op2;
+  enum rtx_code code = GET_CODE (x);
+  enum machine_mode mode = GET_MODE (x);
+  enum machine_mode op_mode;
+  bool valid_ops = true;
+
+  /* If X is OLD_RTX, return NEW_RTX.  Otherwise, if this is an expression,
+     try to build a new expression from recursive substitution.  */
+
+  if (x == old)
+    {
+      *px = new;
+      return can_appear;
+    }
+
+  switch (GET_RTX_CLASS (code))
+    {
+    case RTX_UNARY:
+      op0 = XEXP (x, 0);
+      op_mode = GET_MODE (op0);
+      valid_ops &= propagate_rtx_1 (&op0, old, new, can_appear);
+      if (op0 == XEXP (x, 0))
+	return true;
+      tem = simplify_gen_unary (code, mode, op0, op_mode);
+      break;
+
+    case RTX_BIN_ARITH:
+    case RTX_COMM_ARITH:
+      op0 = XEXP (x, 0);
+      op1 = XEXP (x, 1);
+      valid_ops &= propagate_rtx_1 (&op0, old, new, can_appear);
+      valid_ops &= propagate_rtx_1 (&op1, old, new, can_appear);
+      if (op0 == XEXP (x, 0) && op1 == XEXP (x, 1))
+	return true;
+      tem = simplify_gen_binary (code, mode, op0, op1);
+      break;
+
+    case RTX_COMPARE:
+    case RTX_COMM_COMPARE:
+      op0 = XEXP (x, 0);
+      op1 = XEXP (x, 1);
+      op_mode = GET_MODE (op0) != VOIDmode ? GET_MODE (op0) : GET_MODE (op1);
+      valid_ops &= propagate_rtx_1 (&op0, old, new, can_appear);
+      valid_ops &= propagate_rtx_1 (&op1, old, new, can_appear);
+      if (op0 == XEXP (x, 0) && op1 == XEXP (x, 1))
+	return true;
+      tem = simplify_gen_relational (code, mode, op_mode, op0, op1);
+      break;
+
+    case RTX_TERNARY:
+    case RTX_BITFIELD_OPS:
+      op0 = XEXP (x, 0);
+      op1 = XEXP (x, 1);
+      op2 = XEXP (x, 2);
+      op_mode = GET_MODE (op0);
+      valid_ops &= propagate_rtx_1 (&op0, old, new, can_appear);
+      valid_ops &= propagate_rtx_1 (&op1, old, new, can_appear);
+      valid_ops &= propagate_rtx_1 (&op2, old, new, can_appear);
+      if (op0 == XEXP (x, 0) && op1 == XEXP (x, 1) && op2 == XEXP (x, 2))
+	return true;
+      if (op_mode == VOIDmode)
+	op_mode = GET_MODE (op0);
+      tem = simplify_gen_ternary (code, mode, op_mode, op0, op1, op2);
+      break;
+
+    case RTX_EXTRA:
+      /* The only case we try to handle is a SUBREG.  */
+      if (code == SUBREG)
+	{
+          op0 = XEXP (x, 0);
+	  valid_ops &= propagate_rtx_1 (&op0, old, new, can_appear);
+          if (op0 == XEXP (x, 0))
+	    return true;
+	  tem = simplify_gen_subreg (mode, op0, GET_MODE (SUBREG_REG (x)),
+				     SUBREG_BYTE (x));
+	}
+      break;
+
+    case RTX_OBJ:
+      if (code == MEM && x != new)
+	{
+	  rtx new_op0;
+	  op0 = XEXP (x, 0);
+
+	  /* There are some addresses that we cannot work on.  */
+	  if (!can_simplify_addr (op0))
+	    return true;
+
+	  op0 = new_op0 = targetm.delegitimize_address (op0);
+	  valid_ops &= propagate_rtx_1 (&new_op0, old, new, true);
+
+	  /* Dismiss transformation that we do not want to carry on.  */
+	  if (!valid_ops
+	      || new_op0 == op0
+	      || GET_MODE (new_op0) != GET_MODE (op0))
+	    return true;
+
+	  canonicalize_address (new_op0);
+
+	  /* Copy propagations are always ok.  Otherwise check the costs.  */
+	  if (!(REG_P (old) && REG_P (new))
+	      && !should_replace_address (op0, new_op0, GET_MODE (x)))
+	    return true;
+
+	  tem = replace_equiv_address_nv (x, new_op0);
+	}
+
+      else if (code == LO_SUM)
+	{
+          op0 = XEXP (x, 0);
+          op1 = XEXP (x, 1);
+
+	  /* The only simplification we do attempts to remove references to op0
+	     or make it constant -- in both cases, op0's invalidity will not
+	     make the result invalid.  */
+	  propagate_rtx_1 (&op0, old, new, true);
+	  valid_ops &= propagate_rtx_1 (&op1, old, new, can_appear);
+          if (op0 == XEXP (x, 0) && op1 == XEXP (x, 1))
+	    return true;
+
+	  /* (lo_sum (high x) x) -> x  */
+	  if (GET_CODE (op0) == HIGH && rtx_equal_p (XEXP (op0, 0), op1))
+	    tem = op1;
+	  else
+	    tem = gen_rtx_LO_SUM (mode, op0, op1);
+
+	  /* OP1 is likely not a legitimate address, otherwise there would have
+	     been no LO_SUM.  We want it to disappear if it is invalid, return
+	     false in that case.  */
+	  return memory_address_p (mode, tem);
+	}
+
+      else if (code == REG)
+	{
+	  if (rtx_equal_p (x, old))
+	    {
+              *px = new;
+              return can_appear;
+	    }
+	}
+      break;
+
+    default:
+      break;
+    }
+
+  /* No change, no trouble.  */
+  if (tem == NULL_RTX)
+    return true;
+
+  *px = tem;
+
+  /* The replacement we made so far is valid, if all of the recursive
+     replacements were valid, or we could simplify everything to
+     a constant.  */
+  return valid_ops || can_appear || CONSTANT_P (tem);
+}
+
+/* Replace all occurrences of OLD in X with NEW and try to simplify the
+   resulting expression (in mode MODE).  Return a new expresion if it is
+   a constant, otherwise X.
+
+   Simplifications where occurrences of NEW collapse to a constant are always
+   accepted.  All simplifications are accepted if NEW is a pseudo too.
+   Otherwise, we accept simplifications that have a lower or equal cost.  */
+
+static rtx
+propagate_rtx (rtx x, enum machine_mode mode, rtx old, rtx new)
+{
+  rtx tem;
+  bool collapsed;
+
+  if (REG_P (new) && REGNO (new) < FIRST_PSEUDO_REGISTER)
+    return NULL_RTX;
+
+  new = copy_rtx (new);
+
+  tem = x;
+  collapsed = propagate_rtx_1 (&tem, old, new, REG_P (new) || CONSTANT_P (new));
+  if (tem == x || !collapsed)
+    return NULL_RTX;
+
+  /* gen_lowpart_common will not be able to process VOIDmode entities other
+     than CONST_INTs.  */
+  if (GET_MODE (tem) == VOIDmode && GET_CODE (tem) != CONST_INT)
+    return NULL_RTX;
+
+  if (GET_MODE (tem) == VOIDmode)
+    tem = rtl_hooks.gen_lowpart_no_emit (mode, tem);
+  else
+    gcc_assert (GET_MODE (tem) == mode);
+
+  return tem;
+}
+
+
+
+
+/* Return true if the register from reference REF is killed
+   between FROM to (but not including) TO.  */
+
+static bool 
+local_ref_killed_between_p (struct df_ref * ref, rtx from, rtx to)
+{
+  while (from != to)
+    {
+      struct df_ref * def = DF_INSN_DEFS (df, from);
+      while (def)
+	{
+	  if (DF_REF_REGNO (ref) == DF_REF_REGNO (def))
+	    return true;
+	  def = def->next_ref;
+	}
+
+      from = NEXT_INSN (from);
+    }
+  return false;
+}
+
+
+/* Check if the given DEF is available in INSN.  This would require full
+   computation of available expressions; we check only restricted conditions:
+   - if DEF is the sole definition of its register, go ahead;
+   - in the same basic block, we check for no definitions killing the
+     definition of DEF_INSN;
+   - if USE's basic block has DEF's basic block as the sole predecessor,
+     we check if the definition is killed after DEF_INSN or before
+     TARGET_INSN insn, in their respective basic blocks.  */
+static bool
+use_killed_between (struct df_ref *use, rtx def_insn, rtx target_insn)
+{
+  basic_block def_bb, target_bb;
+  int regno;
+  struct df_ref * def;
+
+  /* Check if the reg in USE has only one definition.  We already
+     know that this definition reaches use, or we wouldn't be here.  */
+  regno = DF_REF_REGNO (use);
+  def = DF_REG_DEF_GET (df, regno)->reg_chain;
+  if (def && (def->next_reg == NULL))
+    return false;
+
+  /* Check if we are in the same basic block.  */
+  def_bb = BLOCK_FOR_INSN (def_insn);
+  target_bb = BLOCK_FOR_INSN (target_insn);
+  if (def_bb == target_bb)
+    return local_ref_killed_between_p (use, def_insn, target_insn);
+
+  /* Finally, if DEF_BB is the sole predecessor of TARGET_BB.  */
+  if (single_pred_p (target_bb)
+      && single_pred (target_bb) == def_bb)
+    {
+      struct df_ref *x;
+
+      /* See if USE is killed between DEF_INSN and the last insn in the
+	 basic block containing DEF_INSN.  */
+      x = df_bb_regno_last_def_find (df, def_bb, regno);
+      if (x && DF_INSN_LUID (df, x->insn) >= DF_INSN_LUID (df, def_insn))
+	return true;
+
+      /* See if USE is killed between TARGET_INSN and the first insn in the
+	 basic block containing TARGET_INSN.  */
+      x = df_bb_regno_first_def_find (df, target_bb, regno);
+      if (x && DF_INSN_LUID (df, x->insn) < DF_INSN_LUID (df, target_insn))
+	return true;
+
+      return false;
+    }
+
+  /* Otherwise assume the worst case.  */
+  return true;
+}
+
+
+/* for_each_rtx traversal function that returns 1 if BODY points to
+   a non-constant mem.  */
+
+static int
+varying_mem_p (rtx *body, void *data ATTRIBUTE_UNUSED)
+{
+  rtx x = *body;
+  return MEM_P (x) && !MEM_READONLY_P (x);
+}
+            
+/* Check if all uses in DEF_INSN can be used in TARGET_INSN.  This
+   would require full computation of available expressions;
+   we check only restricted conditions, see use_killed_between.  */
+static bool
+all_uses_available_at (rtx def_insn, rtx target_insn)
+{
+  struct df_ref * use;
+  rtx def_set = single_set (def_insn);
+
+  gcc_assert (def_set);
+
+  /* If target_insn comes right after def_insn, which is very common
+     for addresses, we can use a quicker test.  */
+  if (NEXT_INSN (def_insn) == target_insn
+      && REG_P (SET_DEST (def_set)))
+    {
+      rtx def_reg = SET_DEST (def_set);
+
+      /* If the insn uses the reg that it defines, the substitution is
+         invalid.  */
+      for (use = DF_INSN_USES (df, def_insn); use; use = use->next_ref)
+        if (rtx_equal_p (use->reg, def_reg))
+          return false;
+    }
+  else
+    {
+      /* Look at all the uses of DEF_INSN, and see if they are not
+	 killed between DEF_INSN and TARGET_INSN.  */
+      for (use = DF_INSN_USES (df, def_insn); use; use = use->next_ref)
+	if (use_killed_between (use, def_insn, target_insn))
+	  return false;
+    }
+
+  /* We don't do any analysis of memories or aliasing.  Reject any
+     instruction that involves references to non-constant memory.  */
+  return !for_each_rtx (&SET_SRC (def_set), varying_mem_p, NULL);
+}
+
+
+
+/* Inside INSN, the expression rooted at *LOC has been changed, moving some
+   uses from ORIG_USES.  Find those that are present, and create new items
+   in the data flow object of the pass.  Mark any new uses as having the
+   given TYPE.  */
+static void
+update_df (rtx insn, rtx *loc, struct df_ref *orig_uses, enum df_ref_type type,
+	   int new_flags)
+{
+  struct df_ref *use;
+
+  /* Add a use for the registers that were propagated.  */
+  for (use = orig_uses; use; use = use->next_ref)
+    {
+      struct df_ref *orig_use = use, *new_use;
+      rtx *new_loc = find_occurrence (loc, DF_REF_REG (orig_use));
+
+      if (!new_loc)
+	continue;
+
+      /* Add a new insn use.  Use the original type, because it says if the
+         use was within a MEM.  */
+      new_use = df_ref_create (df, DF_REF_REG (orig_use), new_loc,
+			       insn, BLOCK_FOR_INSN (insn),
+			       type, DF_REF_FLAGS (orig_use) | new_flags);
+
+      /* Set up the use-def chain.  */
+      df_chain_copy (df->problems_by_index[DF_CHAIN], 
+		     new_use, DF_REF_CHAIN (orig_use));
+    }
+}
+
+
+/* Try substituting NEW into LOC, which originated from forward propagation
+   of USE's value from DEF_INSN.  SET_REG_EQUAL says whether we are
+   substituting the whole SET_SRC, so we can set a REG_EQUAL note if the
+   new insn is not recognized.  Return whether the substitution was
+   performed.  */
+
+static bool
+try_fwprop_subst (struct df_ref *use, rtx *loc, rtx new, rtx def_insn, bool set_reg_equal)
+{
+  rtx insn = DF_REF_INSN (use);
+  enum df_ref_type type = DF_REF_TYPE (use);
+  int flags = DF_REF_FLAGS (use);
+
+  if (dump_file)
+    {
+      fprintf (dump_file, "\nIn insn %d, replacing\n ", INSN_UID (insn));
+      print_inline_rtx (dump_file, *loc, 2);
+      fprintf (dump_file, "\n with ");
+      print_inline_rtx (dump_file, new, 2);
+      fprintf (dump_file, "\n");
+    }
+
+  if (validate_change (insn, loc, new, false))
+    {
+      num_changes++;
+      if (dump_file)
+	fprintf (dump_file, "Changed insn %d\n", INSN_UID (insn));
+
+      /* Unlink the use that we changed.  */
+      df_ref_remove (df, use);
+      if (!CONSTANT_P (new))
+	update_df (insn, loc, DF_INSN_USES (df, def_insn), type, flags);
+
+      return true;
+    }
+  else
+    {
+      if (dump_file)
+	fprintf (dump_file, "Changes to insn %d not recognized\n",
+		 INSN_UID (insn));
+
+      /* Can also record a simplified value in a REG_EQUAL note, making a
+	 new one if one does not already exist.  */
+      if (set_reg_equal)
+	{
+	  if (dump_file)
+	    fprintf (dump_file, " Setting REG_EQUAL note\n");
+
+	  REG_NOTES (insn) = gen_rtx_EXPR_LIST (REG_EQUAL, copy_rtx (new),
+						REG_NOTES (insn));
+
+          if (!CONSTANT_P (new))
+	    update_df (insn, loc, DF_INSN_USES (df, def_insn),
+		       type, DF_REF_IN_NOTE);
+	}
+
+      return false;
+    }
+}
+
+
+/* If USE is a paradoxical subreg, see if it can be replaced by a pseudo.  */
+
+static bool
+forward_propagate_subreg (struct df_ref *use, rtx def_insn, rtx def_set)
+{
+  rtx use_reg = DF_REF_REG (use);
+  rtx use_insn, src;
+
+  /* Only consider paradoxical subregs... */
+  enum machine_mode use_mode = GET_MODE (use_reg);
+  if (GET_CODE (use_reg) != SUBREG
+      || !REG_P (SET_DEST (def_set))
+      || GET_MODE_SIZE (use_mode)
+	 <= GET_MODE_SIZE (GET_MODE (SUBREG_REG (use_reg))))
+    return false;
+
+  /* If this is a paradoxical SUBREG, we have no idea what value the
+     extra bits would have.  However, if the operand is equivalent to
+     a SUBREG whose operand is the same as our mode, and all the modes
+     are within a word, we can just use the inner operand because
+     these SUBREGs just say how to treat the register.  */
+  use_insn = DF_REF_INSN (use);
+  src = SET_SRC (def_set);
+  if (GET_CODE (src) == SUBREG
+      && REG_P (SUBREG_REG (src))
+      && GET_MODE (SUBREG_REG (src)) == use_mode
+      && subreg_lowpart_p (src)
+      && all_uses_available_at (def_insn, use_insn))
+    return try_fwprop_subst (use, DF_REF_LOC (use), SUBREG_REG (src),
+			     def_insn, false);
+  else
+    return false;
+}
+
+/* Try to replace USE with SRC (defined in DEF_INSN) and simplify the
+   result.  */
+
+static bool
+forward_propagate_and_simplify (struct df_ref *use, rtx def_insn, rtx def_set)
+{
+  rtx use_insn = DF_REF_INSN (use);
+  rtx use_set = single_set (use_insn);
+  rtx src, reg, new, *loc;
+  bool set_reg_equal;
+  enum machine_mode mode;
+
+  if (!use_set)
+    return false;
+
+  /* Do not propagate into PC, CC0, etc.  */
+  if (GET_MODE (SET_DEST (use_set)) == VOIDmode)
+    return false;
+
+  /* If def and use are subreg, check if they match.  */
+  reg = DF_REF_REG (use);
+  if (GET_CODE (reg) == SUBREG
+      && GET_CODE (SET_DEST (def_set)) == SUBREG
+      && (SUBREG_BYTE (SET_DEST (def_set)) != SUBREG_BYTE (reg)
+	  || GET_MODE (SET_DEST (def_set)) != GET_MODE (reg)))
+    return false;
+
+  /* Check if the def had a subreg, but the use has the whole reg.  */
+  if (REG_P (reg) && GET_CODE (SET_DEST (def_set)) == SUBREG)
+    return false;
+
+  /* Check if the use has a subreg, but the def had the whole reg.  Unlike the
+     previous case, the optimization is possible and often useful indeed.  */
+  if (GET_CODE (reg) == SUBREG && REG_P (SET_DEST (def_set)))
+    reg = SUBREG_REG (reg);
+
+  /* Check if the substitution is valid (last, because it's the most
+     expensive check!).  */
+  src = SET_SRC (def_set);
+  if (!CONSTANT_P (src) && !all_uses_available_at (def_insn, use_insn))
+    return false;
+
+  /* Check if the def is loading something from the constant pool; in this
+     case we would undo optimization such as compress_float_constant.
+     Still, we can set a REG_EQUAL note.  */
+  if (MEM_P (src) && MEM_READONLY_P (src))
+    {
+      rtx x = avoid_constant_pool_reference (src);
+      if (x != src)
+	{
+          rtx note = find_reg_note (use_insn, REG_EQUAL, NULL_RTX);
+	  rtx old = note ? XEXP (note, 0) : SET_SRC (use_set);
+	  rtx new = simplify_replace_rtx (old, src, x);
+	  if (old != new)	
+            set_unique_reg_note (use_insn, REG_EQUAL, copy_rtx (new));
+	}
+      return false;
+    }
+
+  /* Else try simplifying.  */
+
+  if (DF_REF_TYPE (use) == DF_REF_REG_MEM_STORE)
+    {
+      loc = &SET_DEST (use_set);
+      set_reg_equal = false;
+    }
+  else
+    {
+      rtx note = find_reg_note (use_insn, REG_EQUAL, NULL_RTX);
+      if (DF_REF_FLAGS (use) & DF_REF_IN_NOTE)
+	loc = &XEXP (note, 0);
+      else
+	loc = &SET_SRC (use_set);
+	  
+      /* Do not replace an existing REG_EQUAL note if the insn is not
+	 recognized.  Either we're already replacing in the note, or
+	 we'll separately try plugging the definition in the note and
+	 simplifying.  */
+      set_reg_equal = (note == NULL_RTX);
+    }
+
+  if (GET_MODE (*loc) == VOIDmode)
+    mode = GET_MODE (SET_DEST (use_set));
+  else
+    mode = GET_MODE (*loc);
+
+  new = propagate_rtx (*loc, mode, reg, src);
+  
+  if (!new)
+    return false;
+
+  return try_fwprop_subst (use, loc, new, def_insn, set_reg_equal);
+}
+
+
+/* Given a use USE of an insn, if it has a single reaching
+   definition, try to forward propagate it into that insn.  */
+
+static void
+forward_propagate_into (struct df_ref *use)
+{
+  struct df_link *defs;
+  struct df_ref *def;
+  rtx def_insn, def_set, use_insn;
+  rtx parent;  
+
+  if (DF_REF_FLAGS (use) & DF_REF_READ_WRITE)
+    return;
+
+  /* Only consider uses that have a single definition.  */
+  defs = DF_REF_CHAIN (use);
+  if (!defs || defs->next)
+    return;
+
+  def = defs->ref;
+  if (DF_REF_FLAGS (def) & DF_REF_READ_WRITE)
+    return;
+
+  /* Do not propagate loop invariant definitions inside the loop if
+     we are going to unroll.  */
+  if (loops.num > 0
+      && DF_REF_BB (def)->loop_father != DF_REF_BB (use)->loop_father)
+    return;
+
+  /* Check if the use is still present in the insn!  */
+  use_insn = DF_REF_INSN (use);
+  if (DF_REF_FLAGS (use) & DF_REF_IN_NOTE)
+    parent = find_reg_note (use_insn, REG_EQUAL, NULL_RTX);
+  else
+    parent = PATTERN (use_insn);
+
+  if (!loc_mentioned_in_p (DF_REF_LOC (use), parent))
+    return;
+
+  def_insn = DF_REF_INSN (def);
+  def_set = single_set (def_insn);
+  if (!def_set)
+    return;
+
+  /* Only try one kind of propagation.  If two are possible, we'll
+     do it on the following iterations.  */
+  if (!forward_propagate_and_simplify (use, def_insn, def_set))
+    forward_propagate_subreg (use, def_insn, def_set);
+}
+
+
+static void
+fwprop_init (void)
+{
+  num_changes = 0;
+
+  /* We do not always want to propagate into loops, so we have to find
+     loops and be careful about them.  But we have to call flow_loops_find
+     before df_analyze, because flow_loops_find may introduce new jump
+     insns (sadly) if we are not working in cfglayout mode.  */
+  if (flag_rerun_cse_after_loop && (flag_unroll_loops || flag_peel_loops))
+    {
+      calculate_dominance_info (CDI_DOMINATORS);
+      flow_loops_find (&loops);
+    }
+
+  /* Now set up the dataflow problem (we only want use-def chains) and
+     put the dataflow solver to work.  */
+  df = df_init (DF_SUBREGS | DF_EQUIV_NOTES);
+  df_chain_add_problem (df, DF_UD_CHAIN);
+  df_analyze (df);
+  df_dump (df, dump_file);
+}
+
+static void
+fwprop_done (void)
+{
+  df_finish (df);
+  cleanup_cfg (0);
+  delete_trivially_dead_insns (get_insns (), max_reg_num ());
+
+  if (dump_file)
+    fprintf (dump_file,
+	     "\nNumber of successful forward propagations: %d\n\n",
+	     num_changes);
+
+  if (flag_rerun_cse_after_loop && (flag_unroll_loops || flag_peel_loops))
+    {
+      flow_loops_free (&loops);
+      free_dominance_info (CDI_DOMINATORS);
+      loops.num = 0;
+    }
+
+}
+
+
+
+/* Main entry point.  */
+
+static bool
+gate_fwprop (void)
+{
+  return optimize > 0 && flag_forward_propagate;
+}
+
+static unsigned int
+fwprop (void)
+{
+  unsigned i;
+
+  fwprop_init ();
+
+  /* Go through all the uses.  update_df will create new ones at the
+     end, and we'll go through them as well.
+
+     Do not forward propagate addresses into loops until after unrolling.
+     CSE did so because it was able to fix its own mess, but we are not.  */
+
+  df_reorganize_refs (&df->use_info);
+  for (i = 0; i < DF_USES_SIZE (df); i++)
+    {
+      struct df_ref *use = DF_USES_GET (df, i);
+      if (use)
+	if (loops.num == 0
+	    || DF_REF_TYPE (use) == DF_REF_REG_USE
+	    || DF_REF_BB (use)->loop_father == NULL)
+	  forward_propagate_into (use);
+    }
+
+  fwprop_done ();
+
+  return 0;
+}
+
+struct tree_opt_pass pass_rtl_fwprop =
+{
+  "fwprop1",                            /* name */
+  gate_fwprop,				/* gate */   
+  fwprop,				/* execute */       
+  NULL,                                 /* sub */
+  NULL,                                 /* next */
+  0,                                    /* static_pass_number */
+  TV_FWPROP,                            /* tv_id */
+  0,                                    /* properties_required */
+  0,                                    /* properties_provided */
+  0,                                    /* properties_destroyed */
+  0,                                    /* todo_flags_start */
+  TODO_dump_func,                       /* todo_flags_finish */
+  0                                     /* letter */
+};
+
+static bool
+gate_fwprop_addr (void)
+{
+  return optimize > 0 && flag_forward_propagate && flag_rerun_cse_after_loop
+  	 && (flag_unroll_loops || flag_peel_loops);
+}
+
+static unsigned int
+fwprop_addr (void)
+{
+  unsigned i;
+  fwprop_init ();
+
+  /* Go through all the uses.  update_df will create new ones at the
+     end, and we'll go through them as well.  */
+  df_reorganize_refs (&df->use_info);
+  for (i = 0; i < DF_USES_SIZE (df); i++)
+    {
+      struct df_ref *use = DF_USES_GET (df, i);
+      if (use)
+	if (DF_REF_TYPE (use) != DF_REF_REG_USE
+	    && DF_REF_BB (use)->loop_father != NULL)
+	  forward_propagate_into (use);
+    }
+
+  fwprop_done ();
+
+  return 0;
+}
+
+struct tree_opt_pass pass_rtl_fwprop_addr =
+{
+  "fwprop2",                            /* name */
+  gate_fwprop_addr,			/* gate */   
+  fwprop_addr,				/* execute */       
+  NULL,                                 /* sub */
+  NULL,                                 /* next */
+  0,                                    /* static_pass_number */
+  TV_FWPROP,                            /* tv_id */
+  0,                                    /* properties_required */
+  0,                                    /* properties_provided */
+  0,                                    /* properties_destroyed */
+  0,                                    /* todo_flags_start */
+  TODO_dump_func,                       /* todo_flags_finish */
+  0                                     /* letter */
+};


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