--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/gcc/combine-stack-adj.c	Fri Jul 17 14:47:48 2009 +0900
@@ -0,0 +1,564 @@
+/* Combine stack adjustments.
+   Copyright (C) 1987, 1988, 1989, 1992, 1993, 1994, 1995, 1996, 1997,
+   1998, 1999, 2000, 2001, 2002, 2003, 2004, 2005, 2006, 2007, 2008
+   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 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/>.  */
+
+/* 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+   (a) no longer valid because we've exceeded their range, (b) a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 "df.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_rtx = XVECEXP (tmp, 0, i);
+
+      /* The special case is allowing a no-op set.  */
+      if (GET_CODE (this_rtx) == SET
+	  && SET_SRC (this_rtx) == SET_DEST (this_rtx))
+	;
+      else if (GET_CODE (this_rtx) != CLOBBER
+	       && GET_CODE (this_rtx) != 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;
+}
+
+/* Adjust or create REG_FRAME_RELATED_EXPR note when merging a stack
+   adjustment into a frame related insn.  */
+
+static void
+adjust_frame_related_expr (rtx last_sp_set, rtx insn,
+			   HOST_WIDE_INT this_adjust)
+{
+  rtx note = find_reg_note (last_sp_set, REG_FRAME_RELATED_EXPR, NULL_RTX);
+  rtx new_expr = NULL_RTX;
+
+  if (note == NULL_RTX && RTX_FRAME_RELATED_P (insn))
+    return;
+
+  if (note
+      && GET_CODE (XEXP (note, 0)) == SEQUENCE
+      && XVECLEN (XEXP (note, 0), 0) >= 2)
+    {
+      rtx expr = XEXP (note, 0);
+      rtx last = XVECEXP (expr, 0, XVECLEN (expr, 0) - 1);
+      int i;
+
+      if (GET_CODE (last) == SET
+	  && RTX_FRAME_RELATED_P (last) == RTX_FRAME_RELATED_P (insn)
+	  && SET_DEST (last) == stack_pointer_rtx
+	  && GET_CODE (SET_SRC (last)) == PLUS
+	  && XEXP (SET_SRC (last), 0) == stack_pointer_rtx
+	  && GET_CODE (XEXP (SET_SRC (last), 1)) == CONST_INT)
+	{
+	  XEXP (SET_SRC (last), 1)
+	    = GEN_INT (INTVAL (XEXP (SET_SRC (last), 1)) + this_adjust);
+	  return;
+	}
+
+      new_expr = gen_rtx_SEQUENCE (VOIDmode,
+				   rtvec_alloc (XVECLEN (expr, 0) + 1));
+      for (i = 0; i < XVECLEN (expr, 0); i++)
+	XVECEXP (new_expr, 0, i) = XVECEXP (expr, 0, i);
+    }
+  else
+    {
+      new_expr = gen_rtx_SEQUENCE (VOIDmode, rtvec_alloc (2));
+      if (note)
+	XVECEXP (new_expr, 0, 0) = XEXP (note, 0);
+      else
+	{
+	  rtx expr = copy_rtx (single_set_for_csa (last_sp_set));
+
+	  XEXP (SET_SRC (expr), 1)
+	    = GEN_INT (INTVAL (XEXP (SET_SRC (expr), 1)) - this_adjust);
+	  RTX_FRAME_RELATED_P (expr) = 1;
+	  XVECEXP (new_expr, 0, 0) = expr;
+	}
+    }
+
+  XVECEXP (new_expr, 0, XVECLEN (new_expr, 0) - 1)
+    = copy_rtx (single_set_for_csa (insn));
+  RTX_FRAME_RELATED_P (XVECEXP (new_expr, 0, XVECLEN (new_expr, 0) - 1))
+    = RTX_FRAME_RELATED_P (insn);
+  if (note)
+    XEXP (note, 0) = new_expr;
+  else
+    REG_NOTES (last_sp_set)
+      = gen_rtx_EXPR_LIST (REG_FRAME_RELATED_EXPR, new_expr,
+			   REG_NOTES (last_sp_set));
+}
+
+/* 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))
+		    {
+		      if (RTX_FRAME_RELATED_P (last_sp_set))
+			adjust_frame_related_expr (last_sp_set, insn,
+						   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 (last_sp_set);
+	      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)
+{
+  cleanup_cfg (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
+    {
+      df_note_add_problem ();
+      df_analyze ();
+      combine_stack_adjustments ();
+    }
+  return 0;
+}
+
+struct rtl_opt_pass pass_stack_adjustments =
+{
+ {
+  RTL_PASS,
+  "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_df_finish | TODO_verify_rtl_sharing |
+  TODO_dump_func |
+  TODO_ggc_collect,                     /* todo_flags_finish */
+ }
+};
+