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[PATCH] move combine stack adjustments pass into its own file


Hello,

This patch just moves a pass into its own file. Right now, the regmove
pass and the combine stack adjustments pass both live in regmove.c, but
they are unrelated.  My philosophy is: one pass per file.  So I moved
the stack adjustments pass to a new file.

Bootstrapped&tested on x86-64-suse-linux-gnu.  OK?

Gr.
Steven

	* regmove.c: Move all of pass_stack_adjustments from here...
	* combine-stack-adj.c: ...to this new file.
	* Makefile.in: Add rules for combine-stack-adj.o.

Index: regmove.c
===================================================================
--- regmove.c	(revision 123324)
+++ regmove.c	(working copy)
@@ -2083,408 +2083,13 @@ stable_and_no_regs_but_for_p (rtx x, rtx
     }
 }
 
-/* Track stack adjustments and stack memory references.  Attempt to
-   reduce the number of stack adjustments by back-propagating across
-   the memory references.
-
-   This is intended primarily for use with targets that do not define
-   ACCUMULATE_OUTGOING_ARGS.  It is of significantly more value to
-   targets that define PREFERRED_STACK_BOUNDARY more aligned than
-   STACK_BOUNDARY (e.g. x86), or if not all registers can be pushed
-   (e.g. x86 fp regs) which would ordinarily have to be implemented
-   as a sub/mov pair due to restrictions in calls.c.
-
-   Propagation stops when any of the insns that need adjusting are
-   (a) no longer valid because we've exceeded their range, (b) a
-   non-trivial push instruction, or (c) a call instruction.
-
-   Restriction B is based on the assumption that push instructions
-   are smaller or faster.  If a port really wants to remove all
-   pushes, it should have defined ACCUMULATE_OUTGOING_ARGS.  The
-   one exception that is made is for an add immediately followed
-   by a push.  */
-
-/* This structure records stack memory references between stack adjusting
-   instructions.  */
-
-struct csa_memlist
-{
-  HOST_WIDE_INT sp_offset;
-  rtx insn, *mem;
-  struct csa_memlist *next;
-};
-
-static int stack_memref_p (rtx);
-static rtx single_set_for_csa (rtx);
-static void free_csa_memlist (struct csa_memlist *);
-static struct csa_memlist *record_one_stack_memref (rtx, rtx *,
-						    struct csa_memlist *);
-static int try_apply_stack_adjustment (rtx, struct csa_memlist *,
-				       HOST_WIDE_INT, HOST_WIDE_INT);
-static void combine_stack_adjustments_for_block (basic_block);
-static int record_stack_memrefs (rtx *, void *);
-
-
-/* Main entry point for stack adjustment combination.  */
-
-static void
-combine_stack_adjustments (void)
-{
-  basic_block bb;
-
-  FOR_EACH_BB (bb)
-    combine_stack_adjustments_for_block (bb);
-}
-
-/* Recognize a MEM of the form (sp) or (plus sp const).  */
 
-static int
-stack_memref_p (rtx x)
-{
-  if (!MEM_P (x))
-    return 0;
-  x = XEXP (x, 0);
-
-  if (x == stack_pointer_rtx)
-    return 1;
-  if (GET_CODE (x) == PLUS
-      && XEXP (x, 0) == stack_pointer_rtx
-      && GET_CODE (XEXP (x, 1)) == CONST_INT)
-    return 1;
-
-  return 0;
-}
-
-/* Recognize either normal single_set or the hack in i386.md for
-   tying fp and sp adjustments.  */
-
-static rtx
-single_set_for_csa (rtx insn)
-{
-  int i;
-  rtx tmp = single_set (insn);
-  if (tmp)
-    return tmp;
-
-  if (!NONJUMP_INSN_P (insn)
-      || GET_CODE (PATTERN (insn)) != PARALLEL)
-    return NULL_RTX;
-
-  tmp = PATTERN (insn);
-  if (GET_CODE (XVECEXP (tmp, 0, 0)) != SET)
-    return NULL_RTX;
-
-  for (i = 1; i < XVECLEN (tmp, 0); ++i)
-    {
-      rtx this = XVECEXP (tmp, 0, i);
-
-      /* The special case is allowing a no-op set.  */
-      if (GET_CODE (this) == SET
-	  && SET_SRC (this) == SET_DEST (this))
-	;
-      else if (GET_CODE (this) != CLOBBER
-	       && GET_CODE (this) != USE)
-	return NULL_RTX;
-    }
-
-  return XVECEXP (tmp, 0, 0);
-}
-
-/* Free the list of csa_memlist nodes.  */
-
-static void
-free_csa_memlist (struct csa_memlist *memlist)
-{
-  struct csa_memlist *next;
-  for (; memlist ; memlist = next)
-    {
-      next = memlist->next;
-      free (memlist);
-    }
-}
-
-/* Create a new csa_memlist node from the given memory reference.
-   It is already known that the memory is stack_memref_p.  */
-
-static struct csa_memlist *
-record_one_stack_memref (rtx insn, rtx *mem, struct csa_memlist *next_memlist)
-{
-  struct csa_memlist *ml;
-
-  ml = XNEW (struct csa_memlist);
-
-  if (XEXP (*mem, 0) == stack_pointer_rtx)
-    ml->sp_offset = 0;
-  else
-    ml->sp_offset = INTVAL (XEXP (XEXP (*mem, 0), 1));
-
-  ml->insn = insn;
-  ml->mem = mem;
-  ml->next = next_memlist;
-
-  return ml;
-}
-
-/* Attempt to apply ADJUST to the stack adjusting insn INSN, as well
-   as each of the memories in MEMLIST.  Return true on success.  */
-
-static int
-try_apply_stack_adjustment (rtx insn, struct csa_memlist *memlist, HOST_WIDE_INT new_adjust,
-			    HOST_WIDE_INT delta)
-{
-  struct csa_memlist *ml;
-  rtx set;
-
-  set = single_set_for_csa (insn);
-  validate_change (insn, &XEXP (SET_SRC (set), 1), GEN_INT (new_adjust), 1);
-
-  for (ml = memlist; ml ; ml = ml->next)
-    validate_change
-      (ml->insn, ml->mem,
-       replace_equiv_address_nv (*ml->mem,
-				 plus_constant (stack_pointer_rtx,
-						ml->sp_offset - delta)), 1);
-
-  if (apply_change_group ())
-    {
-      /* Succeeded.  Update our knowledge of the memory references.  */
-      for (ml = memlist; ml ; ml = ml->next)
-	ml->sp_offset -= delta;
-
-      return 1;
-    }
-  else
-    return 0;
-}
-
-/* Called via for_each_rtx and used to record all stack memory references in
-   the insn and discard all other stack pointer references.  */
-struct record_stack_memrefs_data
-{
-  rtx insn;
-  struct csa_memlist *memlist;
-};
-
-static int
-record_stack_memrefs (rtx *xp, void *data)
-{
-  rtx x = *xp;
-  struct record_stack_memrefs_data *d =
-    (struct record_stack_memrefs_data *) data;
-  if (!x)
-    return 0;
-  switch (GET_CODE (x))
-    {
-    case MEM:
-      if (!reg_mentioned_p (stack_pointer_rtx, x))
-	return -1;
-      /* We are not able to handle correctly all possible memrefs containing
-         stack pointer, so this check is necessary.  */
-      if (stack_memref_p (x))
-	{
-	  d->memlist = record_one_stack_memref (d->insn, xp, d->memlist);
-	  return -1;
-	}
-      return 1;
-    case REG:
-      /* ??? We want be able to handle non-memory stack pointer
-	 references later.  For now just discard all insns referring to
-	 stack pointer outside mem expressions.  We would probably
-	 want to teach validate_replace to simplify expressions first.
-
-	 We can't just compare with STACK_POINTER_RTX because the
-	 reference to the stack pointer might be in some other mode.
-	 In particular, an explicit clobber in an asm statement will
-	 result in a QImode clobber.  */
-      if (REGNO (x) == STACK_POINTER_REGNUM)
-	return 1;
-      break;
-    default:
-      break;
-    }
-  return 0;
-}
-
-/* Subroutine of combine_stack_adjustments, called for each basic block.  */
-
-static void
-combine_stack_adjustments_for_block (basic_block bb)
-{
-  HOST_WIDE_INT last_sp_adjust = 0;
-  rtx last_sp_set = NULL_RTX;
-  struct csa_memlist *memlist = NULL;
-  rtx insn, next, set;
-  struct record_stack_memrefs_data data;
-  bool end_of_block = false;
-
-  for (insn = BB_HEAD (bb); !end_of_block ; insn = next)
-    {
-      end_of_block = insn == BB_END (bb);
-      next = NEXT_INSN (insn);
-
-      if (! INSN_P (insn))
-	continue;
-
-      set = single_set_for_csa (insn);
-      if (set)
-	{
-	  rtx dest = SET_DEST (set);
-	  rtx src = SET_SRC (set);
-
-	  /* Find constant additions to the stack pointer.  */
-	  if (dest == stack_pointer_rtx
-	      && GET_CODE (src) == PLUS
-	      && XEXP (src, 0) == stack_pointer_rtx
-	      && GET_CODE (XEXP (src, 1)) == CONST_INT)
-	    {
-	      HOST_WIDE_INT this_adjust = INTVAL (XEXP (src, 1));
-
-	      /* If we've not seen an adjustment previously, record
-		 it now and continue.  */
-	      if (! last_sp_set)
-		{
-		  last_sp_set = insn;
-		  last_sp_adjust = this_adjust;
-		  continue;
-		}
-
-	      /* If not all recorded memrefs can be adjusted, or the
-		 adjustment is now too large for a constant addition,
-		 we cannot merge the two stack adjustments.
-
-		 Also we need to be careful to not move stack pointer
-		 such that we create stack accesses outside the allocated
-		 area.  We can combine an allocation into the first insn,
-		 or a deallocation into the second insn.  We can not
-		 combine an allocation followed by a deallocation.
-
-		 The only somewhat frequent occurrence of the later is when
-		 a function allocates a stack frame but does not use it.
-		 For this case, we would need to analyze rtl stream to be
-		 sure that allocated area is really unused.  This means not
-		 only checking the memory references, but also all registers
-		 or global memory references possibly containing a stack
-		 frame address.
-
-		 Perhaps the best way to address this problem is to teach
-		 gcc not to allocate stack for objects never used.  */
-
-	      /* Combine an allocation into the first instruction.  */
-	      if (STACK_GROWS_DOWNWARD ? this_adjust <= 0 : this_adjust >= 0)
-		{
-		  if (try_apply_stack_adjustment (last_sp_set, memlist,
-						  last_sp_adjust + this_adjust,
-						  this_adjust))
-		    {
-		      /* It worked!  */
-		      delete_insn (insn);
-		      last_sp_adjust += this_adjust;
-		      continue;
-		    }
-		}
-
-	      /* Otherwise we have a deallocation.  Do not combine with
-		 a previous allocation.  Combine into the second insn.  */
-	      else if (STACK_GROWS_DOWNWARD
-		       ? last_sp_adjust >= 0 : last_sp_adjust <= 0)
-		{
-		  if (try_apply_stack_adjustment (insn, memlist,
-						  last_sp_adjust + this_adjust,
-						  -last_sp_adjust))
-		    {
-		      /* It worked!  */
-		      delete_insn (last_sp_set);
-		      last_sp_set = insn;
-		      last_sp_adjust += this_adjust;
-		      free_csa_memlist (memlist);
-		      memlist = NULL;
-		      continue;
-		    }
-		}
-
-	      /* Combination failed.  Restart processing from here.  If
-		 deallocation+allocation conspired to cancel, we can
-		 delete the old deallocation insn.  */
-	      if (last_sp_set && last_sp_adjust == 0)
-		delete_insn (insn);
-	      free_csa_memlist (memlist);
-	      memlist = NULL;
-	      last_sp_set = insn;
-	      last_sp_adjust = this_adjust;
-	      continue;
-	    }
-
-	  /* Find a predecrement of exactly the previous adjustment and
-	     turn it into a direct store.  Obviously we can't do this if
-	     there were any intervening uses of the stack pointer.  */
-	  if (memlist == NULL
-	      && MEM_P (dest)
-	      && ((GET_CODE (XEXP (dest, 0)) == PRE_DEC
-		   && (last_sp_adjust
-		       == (HOST_WIDE_INT) GET_MODE_SIZE (GET_MODE (dest))))
-		  || (GET_CODE (XEXP (dest, 0)) == PRE_MODIFY
-		      && GET_CODE (XEXP (XEXP (dest, 0), 1)) == PLUS
-		      && XEXP (XEXP (XEXP (dest, 0), 1), 0) == stack_pointer_rtx
-		      && (GET_CODE (XEXP (XEXP (XEXP (dest, 0), 1), 1))
-		          == CONST_INT)
-		      && (INTVAL (XEXP (XEXP (XEXP (dest, 0), 1), 1))
-		          == -last_sp_adjust)))
-	      && XEXP (XEXP (dest, 0), 0) == stack_pointer_rtx
-	      && ! reg_mentioned_p (stack_pointer_rtx, src)
-	      && memory_address_p (GET_MODE (dest), stack_pointer_rtx)
-	      && validate_change (insn, &SET_DEST (set),
-				  replace_equiv_address (dest,
-							 stack_pointer_rtx),
-				  0))
-	    {
-	      delete_insn (last_sp_set);
-	      free_csa_memlist (memlist);
-	      memlist = NULL;
-	      last_sp_set = NULL_RTX;
-	      last_sp_adjust = 0;
-	      continue;
-	    }
-	}
-
-      data.insn = insn;
-      data.memlist = memlist;
-      if (!CALL_P (insn) && last_sp_set
-	  && !for_each_rtx (&PATTERN (insn), record_stack_memrefs, &data))
-	{
-	   memlist = data.memlist;
-	   continue;
-	}
-      memlist = data.memlist;
-
-      /* Otherwise, we were not able to process the instruction.
-	 Do not continue collecting data across such a one.  */
-      if (last_sp_set
-	  && (CALL_P (insn)
-	      || reg_mentioned_p (stack_pointer_rtx, PATTERN (insn))))
-	{
-	  if (last_sp_set && last_sp_adjust == 0)
-	    delete_insn (last_sp_set);
-	  free_csa_memlist (memlist);
-	  memlist = NULL;
-	  last_sp_set = NULL_RTX;
-	  last_sp_adjust = 0;
-	}
-    }
-
-  if (last_sp_set && last_sp_adjust == 0)
-    delete_insn (last_sp_set);
-
-  if (memlist)
-    free_csa_memlist (memlist);
-}
-
 static bool
 gate_handle_regmove (void)
 {
   return (optimize > 0 && flag_regmove);
 }
 
-
 /* Register allocation pre-pass, to reduce number of moves necessary
    for two-address machines.  */
 static unsigned int
@@ -2513,46 +2118,3 @@ struct tree_opt_pass pass_regmove =
   'N'                                   /* letter */
 };
 
-
-static bool
-gate_handle_stack_adjustments (void)
-{
-  return (optimize > 0);
-}
-
-static unsigned int
-rest_of_handle_stack_adjustments (void)
-{
-  life_analysis (PROP_POSTRELOAD);
-  cleanup_cfg (CLEANUP_EXPENSIVE | CLEANUP_UPDATE_LIFE
-               | (flag_crossjumping ? CLEANUP_CROSSJUMP : 0));
-
-  /* This is kind of a heuristic.  We need to run combine_stack_adjustments
-     even for machines with possibly nonzero RETURN_POPS_ARGS
-     and ACCUMULATE_OUTGOING_ARGS.  We expect that only ports having
-     push instructions will have popping returns.  */
-#ifndef PUSH_ROUNDING
-  if (!ACCUMULATE_OUTGOING_ARGS)
-#endif
-    combine_stack_adjustments ();
-  return 0;
-}
-
-struct tree_opt_pass pass_stack_adjustments =
-{
-  "csa",                                /* name */
-  gate_handle_stack_adjustments,        /* gate */
-  rest_of_handle_stack_adjustments,     /* execute */
-  NULL,                                 /* sub */
-  NULL,                                 /* next */
-  0,                                    /* static_pass_number */
-  0,                                    /* tv_id */
-  0,                                    /* properties_required */
-  0,                                    /* properties_provided */
-  0,                                    /* properties_destroyed */
-  0,                                    /* todo_flags_start */
-  TODO_dump_func |
-  TODO_ggc_collect,                     /* todo_flags_finish */
-  0                                     /* letter */
-};
-
Index: Makefile.in
===================================================================
--- Makefile.in	(revision 123324)
+++ Makefile.in	(working copy)
@@ -969,6 +969,7 @@ OBJS-common = \
 	cfgloopmanip.o \
 	cfgrtl.o \
 	combine.o \
+	combine-stack-adj.o \
 	convert.o \
 	coverage.o \
 	cse.o \
@@ -2679,6 +2680,10 @@ regmove.o : regmove.c $(CONFIG_H) $(SYST
    insn-config.h $(TIMEVAR_H) tree-pass.h \
    $(RECOG_H) output.h $(REGS_H) hard-reg-set.h $(FLAGS_H) $(FUNCTION_H) \
    $(EXPR_H) $(BASIC_BLOCK_H) toplev.h $(TM_P_H) except.h reload.h
+combine-stack-adj.o : combine-stack-adj.c $(CONFIG_H) $(SYSTEM_H) coretypes.h \
+   $(TM_H) $(RTL_H) insn-config.h $(TIMEVAR_H) tree-pass.h \
+   $(RECOG_H) output.h $(REGS_H) hard-reg-set.h $(FLAGS_H) $(FUNCTION_H) \
+   $(EXPR_H) $(BASIC_BLOCK_H) toplev.h $(TM_P_H) except.h reload.h
 ddg.o : ddg.c $(DDG_H) $(CONFIG_H) $(SYSTEM_H) coretypes.h $(TARGET_H) \
    toplev.h $(RTL_H) $(TM_P_H) $(REGS_H) $(FUNCTION_H) \
    $(FLAGS_H) insn-config.h $(INSN_ATTR_H) except.h $(RECOG_H) \
Index: combine-stack-adj.c
===================================================================
--- combine-stack-adj.c	(revision 0)
+++ combine-stack-adj.c	(revision 0)
@@ -0,0 +1,489 @@
+/* Combine stack adjustments.
+   Copyright (C) 1987, 1988, 1989, 1992, 1993, 1994, 1995, 1996, 1997, 1998,
+   1999, 2000, 2001, 2002, 2003, 2004, 2005 Free Software Foundation, Inc.
+
+This file is part of GCC.
+
+GCC is free software; you can redistribute it and/or modify it under
+the terms of the GNU General Public License as published by the Free
+Software Foundation; either version 2, or (at your option) any later
+version.
+
+GCC is distributed in the hope that it will be useful, but WITHOUT ANY
+WARRANTY; without even the implied warranty of MERCHANTABILITY or
+FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+for more details.
+
+You should have received a copy of the GNU General Public License
+along with GCC; see the file COPYING.  If not, write to the Free
+Software Foundation, 51 Franklin Street, Fifth Floor, Boston, MA
+02110-1301, USA.  */
+
+/* Track stack adjustments and stack memory references.  Attempt to
+   reduce the number of stack adjustments by back-propagating across
+   the memory references.
+
+   This is intended primarily for use with targets that do not define
+   ACCUMULATE_OUTGOING_ARGS.  It is of significantly more value to
+   targets that define PREFERRED_STACK_BOUNDARY more aligned than
+   STACK_BOUNDARY (e.g. x86), or if not all registers can be pushed
+   (e.g. x86 fp regs) which would ordinarily have to be implemented
+   as a sub/mov pair due to restrictions in calls.c.
+
+   Propagation stops when any of the insns that need adjusting are
+   (a) no longer valid because we've exceeded their range, (b) a
+   non-trivial push instruction, or (c) a call instruction.
+
+   Restriction B is based on the assumption that push instructions
+   are smaller or faster.  If a port really wants to remove all
+   pushes, it should have defined ACCUMULATE_OUTGOING_ARGS.  The
+   one exception that is made is for an add immediately followed
+   by a push.  */
+
+#include "config.h"
+#include "system.h"
+#include "coretypes.h"
+#include "tm.h"
+#include "rtl.h"
+#include "tm_p.h"
+#include "insn-config.h"
+#include "recog.h"
+#include "output.h"
+#include "regs.h"
+#include "hard-reg-set.h"
+#include "flags.h"
+#include "function.h"
+#include "expr.h"
+#include "basic-block.h"
+#include "except.h"
+#include "toplev.h"
+#include "reload.h"
+#include "timevar.h"
+#include "tree-pass.h"
+
+
+/* Turn STACK_GROWS_DOWNWARD into a boolean.  */
+#ifdef STACK_GROWS_DOWNWARD
+#undef STACK_GROWS_DOWNWARD
+#define STACK_GROWS_DOWNWARD 1
+#else
+#define STACK_GROWS_DOWNWARD 0
+#endif
+
+/* This structure records stack memory references between stack adjusting
+   instructions.  */
+
+struct csa_memlist
+{
+  HOST_WIDE_INT sp_offset;
+  rtx insn, *mem;
+  struct csa_memlist *next;
+};
+
+static int stack_memref_p (rtx);
+static rtx single_set_for_csa (rtx);
+static void free_csa_memlist (struct csa_memlist *);
+static struct csa_memlist *record_one_stack_memref (rtx, rtx *,
+						    struct csa_memlist *);
+static int try_apply_stack_adjustment (rtx, struct csa_memlist *,
+				       HOST_WIDE_INT, HOST_WIDE_INT);
+static void combine_stack_adjustments_for_block (basic_block);
+static int record_stack_memrefs (rtx *, void *);
+
+
+/* Main entry point for stack adjustment combination.  */
+
+static void
+combine_stack_adjustments (void)
+{
+  basic_block bb;
+
+  FOR_EACH_BB (bb)
+    combine_stack_adjustments_for_block (bb);
+}
+
+/* Recognize a MEM of the form (sp) or (plus sp const).  */
+
+static int
+stack_memref_p (rtx x)
+{
+  if (!MEM_P (x))
+    return 0;
+  x = XEXP (x, 0);
+
+  if (x == stack_pointer_rtx)
+    return 1;
+  if (GET_CODE (x) == PLUS
+      && XEXP (x, 0) == stack_pointer_rtx
+      && GET_CODE (XEXP (x, 1)) == CONST_INT)
+    return 1;
+
+  return 0;
+}
+
+/* Recognize either normal single_set or the hack in i386.md for
+   tying fp and sp adjustments.  */
+
+static rtx
+single_set_for_csa (rtx insn)
+{
+  int i;
+  rtx tmp = single_set (insn);
+  if (tmp)
+    return tmp;
+
+  if (!NONJUMP_INSN_P (insn)
+      || GET_CODE (PATTERN (insn)) != PARALLEL)
+    return NULL_RTX;
+
+  tmp = PATTERN (insn);
+  if (GET_CODE (XVECEXP (tmp, 0, 0)) != SET)
+    return NULL_RTX;
+
+  for (i = 1; i < XVECLEN (tmp, 0); ++i)
+    {
+      rtx this = XVECEXP (tmp, 0, i);
+
+      /* The special case is allowing a no-op set.  */
+      if (GET_CODE (this) == SET
+	  && SET_SRC (this) == SET_DEST (this))
+	;
+      else if (GET_CODE (this) != CLOBBER
+	       && GET_CODE (this) != USE)
+	return NULL_RTX;
+    }
+
+  return XVECEXP (tmp, 0, 0);
+}
+
+/* Free the list of csa_memlist nodes.  */
+
+static void
+free_csa_memlist (struct csa_memlist *memlist)
+{
+  struct csa_memlist *next;
+  for (; memlist ; memlist = next)
+    {
+      next = memlist->next;
+      free (memlist);
+    }
+}
+
+/* Create a new csa_memlist node from the given memory reference.
+   It is already known that the memory is stack_memref_p.  */
+
+static struct csa_memlist *
+record_one_stack_memref (rtx insn, rtx *mem, struct csa_memlist *next_memlist)
+{
+  struct csa_memlist *ml;
+
+  ml = XNEW (struct csa_memlist);
+
+  if (XEXP (*mem, 0) == stack_pointer_rtx)
+    ml->sp_offset = 0;
+  else
+    ml->sp_offset = INTVAL (XEXP (XEXP (*mem, 0), 1));
+
+  ml->insn = insn;
+  ml->mem = mem;
+  ml->next = next_memlist;
+
+  return ml;
+}
+
+/* Attempt to apply ADJUST to the stack adjusting insn INSN, as well
+   as each of the memories in MEMLIST.  Return true on success.  */
+
+static int
+try_apply_stack_adjustment (rtx insn, struct csa_memlist *memlist, HOST_WIDE_INT new_adjust,
+			    HOST_WIDE_INT delta)
+{
+  struct csa_memlist *ml;
+  rtx set;
+
+  set = single_set_for_csa (insn);
+  validate_change (insn, &XEXP (SET_SRC (set), 1), GEN_INT (new_adjust), 1);
+
+  for (ml = memlist; ml ; ml = ml->next)
+    validate_change
+      (ml->insn, ml->mem,
+       replace_equiv_address_nv (*ml->mem,
+				 plus_constant (stack_pointer_rtx,
+						ml->sp_offset - delta)), 1);
+
+  if (apply_change_group ())
+    {
+      /* Succeeded.  Update our knowledge of the memory references.  */
+      for (ml = memlist; ml ; ml = ml->next)
+	ml->sp_offset -= delta;
+
+      return 1;
+    }
+  else
+    return 0;
+}
+
+/* Called via for_each_rtx and used to record all stack memory references in
+   the insn and discard all other stack pointer references.  */
+struct record_stack_memrefs_data
+{
+  rtx insn;
+  struct csa_memlist *memlist;
+};
+
+static int
+record_stack_memrefs (rtx *xp, void *data)
+{
+  rtx x = *xp;
+  struct record_stack_memrefs_data *d =
+    (struct record_stack_memrefs_data *) data;
+  if (!x)
+    return 0;
+  switch (GET_CODE (x))
+    {
+    case MEM:
+      if (!reg_mentioned_p (stack_pointer_rtx, x))
+	return -1;
+      /* We are not able to handle correctly all possible memrefs containing
+         stack pointer, so this check is necessary.  */
+      if (stack_memref_p (x))
+	{
+	  d->memlist = record_one_stack_memref (d->insn, xp, d->memlist);
+	  return -1;
+	}
+      return 1;
+    case REG:
+      /* ??? We want be able to handle non-memory stack pointer
+	 references later.  For now just discard all insns referring to
+	 stack pointer outside mem expressions.  We would probably
+	 want to teach validate_replace to simplify expressions first.
+
+	 We can't just compare with STACK_POINTER_RTX because the
+	 reference to the stack pointer might be in some other mode.
+	 In particular, an explicit clobber in an asm statement will
+	 result in a QImode clobber.  */
+      if (REGNO (x) == STACK_POINTER_REGNUM)
+	return 1;
+      break;
+    default:
+      break;
+    }
+  return 0;
+}
+
+/* Subroutine of combine_stack_adjustments, called for each basic block.  */
+
+static void
+combine_stack_adjustments_for_block (basic_block bb)
+{
+  HOST_WIDE_INT last_sp_adjust = 0;
+  rtx last_sp_set = NULL_RTX;
+  struct csa_memlist *memlist = NULL;
+  rtx insn, next, set;
+  struct record_stack_memrefs_data data;
+  bool end_of_block = false;
+
+  for (insn = BB_HEAD (bb); !end_of_block ; insn = next)
+    {
+      end_of_block = insn == BB_END (bb);
+      next = NEXT_INSN (insn);
+
+      if (! INSN_P (insn))
+	continue;
+
+      set = single_set_for_csa (insn);
+      if (set)
+	{
+	  rtx dest = SET_DEST (set);
+	  rtx src = SET_SRC (set);
+
+	  /* Find constant additions to the stack pointer.  */
+	  if (dest == stack_pointer_rtx
+	      && GET_CODE (src) == PLUS
+	      && XEXP (src, 0) == stack_pointer_rtx
+	      && GET_CODE (XEXP (src, 1)) == CONST_INT)
+	    {
+	      HOST_WIDE_INT this_adjust = INTVAL (XEXP (src, 1));
+
+	      /* If we've not seen an adjustment previously, record
+		 it now and continue.  */
+	      if (! last_sp_set)
+		{
+		  last_sp_set = insn;
+		  last_sp_adjust = this_adjust;
+		  continue;
+		}
+
+	      /* If not all recorded memrefs can be adjusted, or the
+		 adjustment is now too large for a constant addition,
+		 we cannot merge the two stack adjustments.
+
+		 Also we need to be careful to not move stack pointer
+		 such that we create stack accesses outside the allocated
+		 area.  We can combine an allocation into the first insn,
+		 or a deallocation into the second insn.  We can not
+		 combine an allocation followed by a deallocation.
+
+		 The only somewhat frequent occurrence of the later is when
+		 a function allocates a stack frame but does not use it.
+		 For this case, we would need to analyze rtl stream to be
+		 sure that allocated area is really unused.  This means not
+		 only checking the memory references, but also all registers
+		 or global memory references possibly containing a stack
+		 frame address.
+
+		 Perhaps the best way to address this problem is to teach
+		 gcc not to allocate stack for objects never used.  */
+
+	      /* Combine an allocation into the first instruction.  */
+	      if (STACK_GROWS_DOWNWARD ? this_adjust <= 0 : this_adjust >= 0)
+		{
+		  if (try_apply_stack_adjustment (last_sp_set, memlist,
+						  last_sp_adjust + this_adjust,
+						  this_adjust))
+		    {
+		      /* It worked!  */
+		      delete_insn (insn);
+		      last_sp_adjust += this_adjust;
+		      continue;
+		    }
+		}
+
+	      /* Otherwise we have a deallocation.  Do not combine with
+		 a previous allocation.  Combine into the second insn.  */
+	      else if (STACK_GROWS_DOWNWARD
+		       ? last_sp_adjust >= 0 : last_sp_adjust <= 0)
+		{
+		  if (try_apply_stack_adjustment (insn, memlist,
+						  last_sp_adjust + this_adjust,
+						  -last_sp_adjust))
+		    {
+		      /* It worked!  */
+		      delete_insn (last_sp_set);
+		      last_sp_set = insn;
+		      last_sp_adjust += this_adjust;
+		      free_csa_memlist (memlist);
+		      memlist = NULL;
+		      continue;
+		    }
+		}
+
+	      /* Combination failed.  Restart processing from here.  If
+		 deallocation+allocation conspired to cancel, we can
+		 delete the old deallocation insn.  */
+	      if (last_sp_set && last_sp_adjust == 0)
+		delete_insn (insn);
+	      free_csa_memlist (memlist);
+	      memlist = NULL;
+	      last_sp_set = insn;
+	      last_sp_adjust = this_adjust;
+	      continue;
+	    }
+
+	  /* Find a predecrement of exactly the previous adjustment and
+	     turn it into a direct store.  Obviously we can't do this if
+	     there were any intervening uses of the stack pointer.  */
+	  if (memlist == NULL
+	      && MEM_P (dest)
+	      && ((GET_CODE (XEXP (dest, 0)) == PRE_DEC
+		   && (last_sp_adjust
+		       == (HOST_WIDE_INT) GET_MODE_SIZE (GET_MODE (dest))))
+		  || (GET_CODE (XEXP (dest, 0)) == PRE_MODIFY
+		      && GET_CODE (XEXP (XEXP (dest, 0), 1)) == PLUS
+		      && XEXP (XEXP (XEXP (dest, 0), 1), 0) == stack_pointer_rtx
+		      && (GET_CODE (XEXP (XEXP (XEXP (dest, 0), 1), 1))
+		          == CONST_INT)
+		      && (INTVAL (XEXP (XEXP (XEXP (dest, 0), 1), 1))
+		          == -last_sp_adjust)))
+	      && XEXP (XEXP (dest, 0), 0) == stack_pointer_rtx
+	      && ! reg_mentioned_p (stack_pointer_rtx, src)
+	      && memory_address_p (GET_MODE (dest), stack_pointer_rtx)
+	      && validate_change (insn, &SET_DEST (set),
+				  replace_equiv_address (dest,
+							 stack_pointer_rtx),
+				  0))
+	    {
+	      delete_insn (last_sp_set);
+	      free_csa_memlist (memlist);
+	      memlist = NULL;
+	      last_sp_set = NULL_RTX;
+	      last_sp_adjust = 0;
+	      continue;
+	    }
+	}
+
+      data.insn = insn;
+      data.memlist = memlist;
+      if (!CALL_P (insn) && last_sp_set
+	  && !for_each_rtx (&PATTERN (insn), record_stack_memrefs, &data))
+	{
+	   memlist = data.memlist;
+	   continue;
+	}
+      memlist = data.memlist;
+
+      /* Otherwise, we were not able to process the instruction.
+	 Do not continue collecting data across such a one.  */
+      if (last_sp_set
+	  && (CALL_P (insn)
+	      || reg_mentioned_p (stack_pointer_rtx, PATTERN (insn))))
+	{
+	  if (last_sp_set && last_sp_adjust == 0)
+	    delete_insn (last_sp_set);
+	  free_csa_memlist (memlist);
+	  memlist = NULL;
+	  last_sp_set = NULL_RTX;
+	  last_sp_adjust = 0;
+	}
+    }
+
+  if (last_sp_set && last_sp_adjust == 0)
+    delete_insn (last_sp_set);
+
+  if (memlist)
+    free_csa_memlist (memlist);
+}
+
+
+static bool
+gate_handle_stack_adjustments (void)
+{
+  return (optimize > 0);
+}
+
+static unsigned int
+rest_of_handle_stack_adjustments (void)
+{
+  life_analysis (PROP_POSTRELOAD);
+  cleanup_cfg (CLEANUP_EXPENSIVE | CLEANUP_UPDATE_LIFE
+               | (flag_crossjumping ? CLEANUP_CROSSJUMP : 0));
+
+  /* This is kind of a heuristic.  We need to run combine_stack_adjustments
+     even for machines with possibly nonzero RETURN_POPS_ARGS
+     and ACCUMULATE_OUTGOING_ARGS.  We expect that only ports having
+     push instructions will have popping returns.  */
+#ifndef PUSH_ROUNDING
+  if (!ACCUMULATE_OUTGOING_ARGS)
+#endif
+    combine_stack_adjustments ();
+  return 0;
+}
+
+struct tree_opt_pass pass_stack_adjustments =
+{
+  "csa",                                /* name */
+  gate_handle_stack_adjustments,        /* gate */
+  rest_of_handle_stack_adjustments,     /* execute */
+  NULL,                                 /* sub */
+  NULL,                                 /* next */
+  0,                                    /* static_pass_number */
+  0,                                    /* tv_id */
+  0,                                    /* properties_required */
+  0,                                    /* properties_provided */
+  0,                                    /* properties_destroyed */
+  0,                                    /* todo_flags_start */
+  TODO_dump_func |
+  TODO_ggc_collect,                     /* todo_flags_finish */
+  0                                     /* letter */
+};
+


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