text: /* Register to Stack convert for GNU compiler.
     Copyright (C) 1992, 1993, 1994, 1995, 1996, 1997, 1998, 1999,
     2000, 2001, 2002, 2003, 2004 Free Software Foundation, Inc.
  
     This file is part of GCC.
  
     GCC is free software; you can redistribute it and/or modify it
     under the terms of the GNU General Public License as published by
     the Free Software Foundation; either version 2, or (at your option)
     any later version.
  
     GCC is distributed in the hope that it will be useful, but WITHOUT
     ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
     or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public
     License for more details.
  
     You should have received a copy of the GNU General Public License
     along with GCC; see the file COPYING.  If not, write to the Free
     Software Foundation, 59 Temple Place - Suite 330, Boston, MA
     02111-1307, USA.  */
  
  /* This pass converts stack-like registers from the "flat register
     file" model that gcc uses, to a stack convention that the 387 uses.
  
     * The form of the input:
  
     On input, the function consists of insn that have had their
     registers fully allocated to a set of "virtual" registers.  Note that
     the word "virtual" is used differently here than elsewhere in gcc: for
     each virtual stack reg, there is a hard reg, but the mapping between
     them is not known until this pass is run.  On output, hard register
     numbers have been substituted, and various pop and exchange insns have
     been emitted.  The hard register numbers and the virtual register
     numbers completely overlap - before this pass, all stack register
     numbers are virtual, and afterward they are all hard.
  
     The virtual registers can be manipulated normally by gcc, and their
     semantics are the same as for normal registers.  After the hard
     register numbers are substituted, the semantics of an insn containing
     stack-like regs are not the same as for an insn with normal regs: for
     instance, it is not safe to delete an insn that appears to be a no-op
     move.  In general, no insn containing hard regs should be changed
     after this pass is done.
  
     * The form of the output:
  
     After this pass, hard register numbers represent the distance from
     the current top of stack to the desired register.  A reference to
     FIRST_STACK_REG references the top of stack, FIRST_STACK_REG + 1,
     represents the register just below that, and so forth.  Also, REG_DEAD
     notes indicate whether or not a stack register should be popped.
  
     A "swap" insn looks like a parallel of two patterns, where each
     pattern is a SET: one sets A to B, the other B to A.
  
     A "push" or "load" insn is a SET whose SET_DEST is FIRST_STACK_REG
     and whose SET_DEST is REG or MEM.  Any other SET_DEST, such as PLUS,
     will replace the existing stack top, not push a new value.
  
     A store insn is a SET whose SET_DEST is FIRST_STACK_REG, and whose
     SET_SRC is REG or MEM.
  
     The case where the SET_SRC and SET_DEST are both FIRST_STACK_REG
     appears ambiguous.  As a special case, the presence of a REG_DEAD note
     for FIRST_STACK_REG differentiates between a load insn and a pop.
  
     If a REG_DEAD is present, the insn represents a "pop" that discards
     the top of the register stack.  If there is no REG_DEAD note, then the
     insn represents a "dup" or a push of the current top of stack onto the
     stack.
  
     * Methodology:
  
     Existing REG_DEAD and REG_UNUSED notes for stack registers are
     deleted and recreated from scratch.  REG_DEAD is never created for a
     SET_DEST, only REG_UNUSED.
  
     * asm_operands:
  
     There are several rules on the usage of stack-like regs in
     asm_operands insns.  These rules apply only to the operands that are
     stack-like regs:
  
     1. Given a set of input regs that die in an asm_operands, it is
        necessary to know which are implicitly popped by the asm, and
        which must be explicitly popped by gcc.
  
  	An input reg that is implicitly popped by the asm must be
  	explicitly clobbered, unless it is constrained to match an
  	output operand.
  
     2. For any input reg that is implicitly popped by an asm, it is
        necessary to know how to adjust the stack to compensate for the pop.
        If any non-popped input is closer to the top of the reg-stack than
        the implicitly popped reg, it would not be possible to know what the
        stack looked like - it's not clear how the rest of the stack "slides
        up".
  
  	All implicitly popped input regs must be closer to the top of
  	the reg-stack than any input that is not implicitly popped.
  
     3. It is possible that if an input dies in an insn, reload might
        use the input reg for an output reload.  Consider this example:
  
  		asm ("foo" : "=t" (a) : "f" (b));
  
        This asm says that input B is not popped by the asm, and that
        the asm pushes a result onto the reg-stack, ie, the stack is one
        deeper after the asm than it was before.  But, it is possible that
        reload will think that it can use the same reg for both the input and
        the output, if input B dies in this insn.
  
  	If any input operand uses the "f" constraint, all output reg
  	constraints must use the "&" earlyclobber.
  
        The asm above would be written as
  
  		asm ("foo" : "=&t" (a) : "f" (b));
  
     4. Some operands need to be in particular places on the stack.  All
        output operands fall in this category - there is no other way to
        know which regs the outputs appear in unless the user indicates
        this in the constraints.
  
  	Output operands must specifically indicate which reg an output
  	appears in after an asm.  "=f" is not allowed: the operand
  	constraints must select a class with a single reg.
  
     5. Output operands may not be "inserted" between existing stack regs.
        Since no 387 opcode uses a read/write operand, all output operands
        are dead before the asm_operands, and are pushed by the asm_operands.
        It makes no sense to push anywhere but the top of the reg-stack.
  
  	Output operands must start at the top of the reg-stack: output
  	operands may not "skip" a reg.
  
     6. Some asm statements may need extra stack space for internal
        calculations.  This can be guaranteed by clobbering stack registers
        unrelated to the inputs and outputs.
  
     Here are a couple of reasonable asms to want to write.  This asm
     takes one input, which is internally popped, and produces two outputs.
  
  	asm ("fsincos" : "=t" (cos), "=u" (sin) : "0" (inp));
  
     This asm takes two inputs, which are popped by the fyl2xp1 opcode,
     and replaces them with one output.  The user must code the "st(1)"
     clobber for reg-stack.c to know that fyl2xp1 pops both inputs.
  
  	asm ("fyl2xp1" : "=t" (result) : "0" (x), "u" (y) : "st(1)");
  
  */
  
  #include "config.h"
  #include "system.h"
  #include "coretypes.h"
  #include "tm.h"
  #include "tree.h"
  #include "rtl.h"
  #include "tm_p.h"
  #include "function.h"
  #include "insn-config.h"
  #include "regs.h"
  #include "hard-reg-set.h"
  #include "flags.h"
  #include "toplev.h"
  #include "recog.h"
  #include "output.h"
  #include "basic-block.h"
  #include "varray.h"
  #include "reload.h"
  #include "ggc.h"
  
  /* We use this array to cache info about insns, because otherwise we
     spend too much time in stack_regs_mentioned_p.
  
     Indexed by insn UIDs.  A value of zero is uninitialized, one indicates
     the insn uses stack registers, two indicates the insn does not use
     stack registers.  */
  static GTY(()) varray_type stack_regs_mentioned_data;
  
  #ifdef STACK_REGS
  
  #define REG_STACK_SIZE (LAST_STACK_REG - FIRST_STACK_REG + 1)
  
  /* This is the basic stack record.  TOP is an index into REG[] such
     that REG[TOP] is the top of stack.  If TOP is -1 the stack is empty.
  
     If TOP is -2, REG[] is not yet initialized.  Stack initialization
     consists of placing each live reg in array `reg' and setting `top'
     appropriately.
  
     REG_SET indicates which registers are live.  */
  
  typedef struct stack_def
  {
    int top;			/* index to top stack element */
    HARD_REG_SET reg_set;		/* set of live registers */
    unsigned char reg[REG_STACK_SIZE];/* register - stack mapping */
  } *stack;
  
  /* This is used to carry information about basic blocks.  It is
     attached to the AUX field of the standard CFG block.  */
  
  typedef struct block_info_def
  {
    struct stack_def stack_in;	/* Input stack configuration.  */
    struct stack_def stack_out;	/* Output stack configuration.  */
    HARD_REG_SET out_reg_set;	/* Stack regs live on output.  */
    int done;			/* True if block already converted.  */
    int predecessors;		/* Number of predecessors that needs
  				   to be visited.  */
  } *block_info;
  
  #define BLOCK_INFO(B)	((block_info) (B)->aux)
  
  /* Passed to change_stack to indicate where to emit insns.  */
  enum emit_where
  {
    EMIT_AFTER,
    EMIT_BEFORE
  };
  
  /* The block we're currently working on.  */
  static basic_block current_block;
  
  /* This is the register file for all register after conversion.  */
  static rtx
    FP_mode_reg[LAST_STACK_REG+1-FIRST_STACK_REG][(int) MAX_MACHINE_MODE];
  
  #define FP_MODE_REG(regno,mode)	\
    (FP_mode_reg[(regno)-FIRST_STACK_REG][(int) (mode)])
  
  /* Used to initialize uninitialized registers.  */
  static rtx nan;
  
  /* Forward declarations */
  
  static int stack_regs_mentioned_p (rtx pat);
  static void straighten_stack (rtx, stack);
  static void pop_stack (stack, int);
  static rtx *get_true_reg (rtx *);
  
  static int check_asm_stack_operands (rtx);
  static int get_asm_operand_n_inputs (rtx);
  static rtx stack_result (tree);
  static void replace_reg (rtx *, int);
  static void remove_regno_note (rtx, enum reg_note, unsigned int);
  static int get_hard_regnum (stack, rtx);
  static rtx emit_pop_insn (rtx, stack, rtx, enum emit_where);
  static void emit_swap_insn (rtx, stack, rtx);
  static bool move_for_stack_reg (rtx, stack, rtx);
  static int swap_rtx_condition_1 (rtx);
  static int swap_rtx_condition (rtx);
  static void compare_for_stack_reg (rtx, stack, rtx);
  static bool subst_stack_regs_pat (rtx, stack, rtx);
  static void subst_asm_stack_regs (rtx, stack);
  static bool subst_stack_regs (rtx, stack);
  static void change_stack (rtx, stack, stack, enum emit_where);
  static int convert_regs_entry (void);
  static void convert_regs_exit (void);
  static int convert_regs_1 (FILE *, basic_block);
  static int convert_regs_2 (FILE *, basic_block);
  static int convert_regs (FILE *);
  static void print_stack (FILE *, stack);
  static rtx next_flags_user (rtx);
  static void record_label_references (rtx, rtx);
  static bool compensate_edge (edge, FILE *);
  
  /* Return nonzero if any stack register is mentioned somewhere within PAT.  */
  
  static int
  stack_regs_mentioned_p (rtx pat)
  {
    const char *fmt;
    int i;
  
    if (STACK_REG_P (pat))
      return 1;
  
    fmt = GET_RTX_FORMAT (GET_CODE (pat));
    for (i = GET_RTX_LENGTH (GET_CODE (pat)) - 1; i >= 0; i--)
      {
        if (fmt[i] == 'E')
  	{
  	  int j;
  
  	  for (j = XVECLEN (pat, i) - 1; j >= 0; j--)
  	    if (stack_regs_mentioned_p (XVECEXP (pat, i, j)))
  	      return 1;
  	}
        else if (fmt[i] == 'e' && stack_regs_mentioned_p (XEXP (pat, i)))
  	return 1;
      }
  
    return 0;
  }
  
  /* Return nonzero if INSN mentions stacked registers, else return zero.  */
  
  int
  stack_regs_mentioned (rtx insn)
  {
    unsigned int uid, max;
    int test;
  
    if (! INSN_P (insn) || !stack_regs_mentioned_data)
      return 0;
  
    uid = INSN_UID (insn);
    max = VARRAY_SIZE (stack_regs_mentioned_data);
    if (uid >= max)
      {
        /* Allocate some extra size to avoid too many reallocs, but
  	 do not grow too quickly.  */
        max = uid + uid / 20;
        VARRAY_GROW (stack_regs_mentioned_data, max);
      }
  
    test = VARRAY_CHAR (stack_regs_mentioned_data, uid);
    if (test == 0)
      {
        /* This insn has yet to be examined.  Do so now.  */
        test = stack_regs_mentioned_p (PATTERN (insn)) ? 1 : 2;
        VARRAY_CHAR (stack_regs_mentioned_data, uid) = test;
      }
  
    return test == 1;
  }
  
  static rtx ix86_flags_rtx;
  
  static rtx
  next_flags_user (rtx insn)
  {
    /* Search forward looking for the first use of this value.
       Stop at block boundaries.  */
  
    while (insn != BB_END (current_block))
      {
        insn = NEXT_INSN (insn);
  
        if (INSN_P (insn) && reg_mentioned_p (ix86_flags_rtx, PATTERN (insn)))
  	return insn;
  
        if (GET_CODE (insn) == CALL_INSN)
  	return NULL_RTX;
      }
    return NULL_RTX;
  }
  
  /* Reorganize the stack into ascending numbers,
     after this insn.  */
  
  static void
  straighten_stack (rtx insn, stack regstack)
  {
    struct stack_def temp_stack;
    int top;
  
    /* If there is only a single register on the stack, then the stack is
       already in increasing order and no reorganization is needed.
  
       Similarly if the stack is empty.  */
    if (regstack->top <= 0)
      return;
  
    COPY_HARD_REG_SET (temp_stack.reg_set, regstack->reg_set);
  
    for (top = temp_stack.top = regstack->top; top >= 0; top--)
      temp_stack.reg[top] = FIRST_STACK_REG + temp_stack.top - top;
  
    change_stack (insn, regstack, &temp_stack, EMIT_AFTER);
  }
  
  /* Pop a register from the stack.  */
  
  static void
  pop_stack (stack regstack, int regno)
  {
    int top = regstack->top;
  
    CLEAR_HARD_REG_BIT (regstack->reg_set, regno);
    regstack->top--;
    /* If regno was not at the top of stack then adjust stack.  */
    if (regstack->reg [top] != regno)
      {
        int i;
        for (i = regstack->top; i >= 0; i--)
  	if (regstack->reg [i] == regno)
  	  {
  	    int j;
  	    for (j = i; j < top; j++)
  	      regstack->reg [j] = regstack->reg [j + 1];
  	    break;
  	  }
      }
  }
  
  /* Convert register usage from "flat" register file usage to a "stack
     register file.  FIRST is the first insn in the function, FILE is the
     dump file, if used.
  
     Construct a CFG and run life analysis.  Then convert each insn one
     by one.  Run a last cleanup_cfg pass, if optimizing, to eliminate
     code duplication created when the converter inserts pop insns on
     the edges.  */
  
  bool
  reg_to_stack (rtx first, FILE *file)
  {
    basic_block bb;
    int i;
    int max_uid;
  
    /* Clean up previous run.  */
    stack_regs_mentioned_data = 0;
  
    /* See if there is something to do.  Flow analysis is quite
       expensive so we might save some compilation time.  */
    for (i = FIRST_STACK_REG; i <= LAST_STACK_REG; i++)
      if (regs_ever_live[i])
        break;
    if (i > LAST_STACK_REG)
      return false;
  
    /* Ok, floating point instructions exist.  If not optimizing,
       build the CFG and run life analysis.
       Also need to rebuild life when superblock scheduling is done
       as it don't update liveness yet.  */
    if (!optimize
        || (flag_sched2_use_superblocks
  	  && flag_schedule_insns_after_reload))
      {
        count_or_remove_death_notes (NULL, 1);
        life_analysis (first, file, PROP_DEATH_NOTES);
      }
    mark_dfs_back_edges ();
  
    /* Set up block info for each basic block.  */
    alloc_aux_for_blocks (sizeof (struct block_info_def));
    FOR_EACH_BB_REVERSE (bb)
      {
        edge e;
        for (e = bb->pred; e; e = e->pred_next)
  	if (!(e->flags & EDGE_DFS_BACK)
  	    && e->src != ENTRY_BLOCK_PTR)
  	  BLOCK_INFO (bb)->predecessors++;
      }
  
    /* Create the replacement registers up front.  */
    for (i = FIRST_STACK_REG; i <= LAST_STACK_REG; i++)
      {
        enum machine_mode mode;
        for (mode = GET_CLASS_NARROWEST_MODE (MODE_FLOAT);
  	   mode != VOIDmode;
  	   mode = GET_MODE_WIDER_MODE (mode))
  	FP_MODE_REG (i, mode) = gen_rtx_REG (mode, i);
        for (mode = GET_CLASS_NARROWEST_MODE (MODE_COMPLEX_FLOAT);
  	   mode != VOIDmode;
  	   mode = GET_MODE_WIDER_MODE (mode))
  	FP_MODE_REG (i, mode) = gen_rtx_REG (mode, i);
      }
  
    ix86_flags_rtx = gen_rtx_REG (CCmode, FLAGS_REG);
  
    /* A QNaN for initializing uninitialized variables.
  
       ??? We can't load from constant memory in PIC mode, because
       we're inserting these instructions before the prologue and
       the PIC register hasn't been set up.  In that case, fall back
       on zero, which we can get from `ldz'.  */
  
    if (flag_pic)
      nan = CONST0_RTX (SFmode);
    else
      {
        nan = gen_lowpart (SFmode, GEN_INT (0x7fc00000));
        nan = force_const_mem (SFmode, nan);
      }
  
    /* Allocate a cache for stack_regs_mentioned.  */
    max_uid = get_max_uid ();
    VARRAY_CHAR_INIT (stack_regs_mentioned_data, max_uid + 1,
  		    "stack_regs_mentioned cache");
  
    convert_regs (file);
  
    free_aux_for_blocks ();
    return true;
  }
  
  /* Check PAT, which is in INSN, for LABEL_REFs.  Add INSN to the
     label's chain of references, and note which insn contains each
     reference.  */
  
  static void
  record_label_references (rtx insn, rtx pat)
  {
    enum rtx_code code = GET_CODE (pat);
    int i;
    const char *fmt;
  
    if (code == LABEL_REF)
      {
        rtx label = XEXP (pat, 0);
        rtx ref;
  
        if (GET_CODE (label) != CODE_LABEL)
  	abort ();
  
        /* If this is an undefined label, LABEL_REFS (label) contains
           garbage.  */
        if (INSN_UID (label) == 0)
  	return;
  
        /* Don't make a duplicate in the code_label's chain.  */
  
        for (ref = LABEL_REFS (label);
  	   ref && ref != label;
  	   ref = LABEL_NEXTREF (ref))
  	if (CONTAINING_INSN (ref) == insn)
  	  return;
  
        CONTAINING_INSN (pat) = insn;
        LABEL_NEXTREF (pat) = LABEL_REFS (label);
        LABEL_REFS (label) = pat;
  
        return;
      }
  
    fmt = GET_RTX_FORMAT (code);
    for (i = GET_RTX_LENGTH (code) - 1; i >= 0; i--)
      {
        if (fmt[i] == 'e')
  	record_label_references (insn, XEXP (pat, i));
        if (fmt[i] == 'E')
  	{
  	  int j;
  	  for (j = 0; j < XVECLEN (pat, i); j++)
  	    record_label_references (insn, XVECEXP (pat, i, j));
  	}
      }
  }
  
  /* Return a pointer to the REG expression within PAT.  If PAT is not a
     REG, possible enclosed by a conversion rtx, return the inner part of
     PAT that stopped the search.  */
  
  static rtx *
  get_true_reg (rtx *pat)
  {
    for (;;)
      switch (GET_CODE (*pat))
        {
        case SUBREG:
  	/* Eliminate FP subregister accesses in favor of the
  	   actual FP register in use.  */
  	{
  	  rtx subreg;
  	  if (FP_REG_P (subreg = SUBREG_REG (*pat)))
  	    {
  	      int regno_off = subreg_regno_offset (REGNO (subreg),
  						   GET_MODE (subreg),
  						   SUBREG_BYTE (*pat),
  						   GET_MODE (*pat));
  	      *pat = FP_MODE_REG (REGNO (subreg) + regno_off,
  				  GET_MODE (subreg));
  	    default:
  	      return pat;
  	    }
  	}
        case FLOAT:
        case FIX:
        case FLOAT_EXTEND:
  	pat = & XEXP (*pat, 0);
        }
  }
  
  /* Set if we find any malformed asms in a block.  */
  static bool any_malformed_asm;
  
  /* There are many rules that an asm statement for stack-like regs must
     follow.  Those rules are explained at the top of this file: the rule
     numbers below refer to that explanation.  */
  
  static int
  check_asm_stack_operands (rtx insn)
  {
    int i;
    int n_clobbers;
    int malformed_asm = 0;
    rtx body = PATTERN (insn);
  
    char reg_used_as_output[FIRST_PSEUDO_REGISTER];
    char implicitly_dies[FIRST_PSEUDO_REGISTER];
    int alt;
  
    rtx *clobber_reg = 0;
    int n_inputs, n_outputs;
  
    /* Find out what the constraints require.  If no constraint
       alternative matches, this asm is malformed.  */
    extract_insn (insn);
    constrain_operands (1);
    alt = which_alternative;
  
    preprocess_constraints ();
  
    n_inputs = get_asm_operand_n_inputs (body);
    n_outputs = recog_data.n_operands - n_inputs;
  
    if (alt < 0)
      {
        malformed_asm = 1;
        /* Avoid further trouble with this insn.  */
        PATTERN (insn) = gen_rtx_USE (VOIDmode, const0_rtx);
        return 0;
      }
  
    /* Strip SUBREGs here to make the following code simpler.  */
    for (i = 0; i < recog_data.n_operands; i++)
      if (GET_CODE (recog_data.operand[i]) == SUBREG
  	&& GET_CODE (SUBREG_REG (recog_data.operand[i])) == REG)
        recog_data.operand[i] = SUBREG_REG (recog_data.operand[i]);
  
    /* Set up CLOBBER_REG.  */
  
    n_clobbers = 0;
  
    if (GET_CODE (body) == PARALLEL)
      {
        clobber_reg = alloca (XVECLEN (body, 0) * sizeof (rtx));
  
        for (i = 0; i < XVECLEN (body, 0); i++)
  	if (GET_CODE (XVECEXP (body, 0, i)) == CLOBBER)
  	  {
  	    rtx clobber = XVECEXP (body, 0, i);
  	    rtx reg = XEXP (clobber, 0);
  
  	    if (GET_CODE (reg) == SUBREG && GET_CODE (SUBREG_REG (reg)) == REG)
  	      reg = SUBREG_REG (reg);
  
  	    if (STACK_REG_P (reg))
  	      {
  		clobber_reg[n_clobbers] = reg;
  		n_clobbers++;
  	      }
  	  }
      }
  
    /* Enforce rule #4: Output operands must specifically indicate which
       reg an output appears in after an asm.  "=f" is not allowed: the
       operand constraints must select a class with a single reg.
  
       Also enforce rule #5: Output operands must start at the top of
       the reg-stack: output operands may not "skip" a reg.  */
  
    memset (reg_used_as_output, 0, sizeof (reg_used_as_output));
    for (i = 0; i < n_outputs; i++)
      if (STACK_REG_P (recog_data.operand[i]))
        {
  	if (reg_class_size[(int) recog_op_alt[i][alt].class] != 1)
  	  {
  	    error_for_asm (insn, "output constraint %d must specify a single register", i);
  	    malformed_asm = 1;
  	  }
  	else
  	  {
  	    int j;
  
  	    for (j = 0; j < n_clobbers; j++)
  	      if (REGNO (recog_data.operand[i]) == REGNO (clobber_reg[j]))
  		{
  		  error_for_asm (insn, "output constraint %d cannot be specified together with \"%s\" clobber",
  				 i, reg_names [REGNO (clobber_reg[j])]);
  		  malformed_asm = 1;
  		  break;
  		}
  	    if (j == n_clobbers)
  	      reg_used_as_output[REGNO (recog_data.operand[i])] = 1;
  	  }
        }
  
  
    /* Search for first non-popped reg.  */
    for (i = FIRST_STACK_REG; i < LAST_STACK_REG + 1; i++)
      if (! reg_used_as_output[i])
        break;
  
    /* If there are any other popped regs, that's an error.  */
    for (; i < LAST_STACK_REG + 1; i++)
      if (reg_used_as_output[i])
        break;
  
    if (i != LAST_STACK_REG + 1)
      {
        error_for_asm (insn, "output regs must be grouped at top of stack");
        malformed_asm = 1;
      }
  
    /* Enforce rule #2: All implicitly popped input regs must be closer
       to the top of the reg-stack than any input that is not implicitly
       popped.  */
  
    memset (implicitly_dies, 0, sizeof (implicitly_dies));
    for (i = n_outputs; i < n_outputs + n_inputs; i++)
      if (STACK_REG_P (recog_data.operand[i]))
        {
  	/* An input reg is implicitly popped if it is tied to an
  	   output, or if there is a CLOBBER for it.  */
  	int j;
  
  	for (j = 0; j < n_clobbers; j++)
  	  if (operands_match_p (clobber_reg[j], recog_data.operand[i]))
  	    break;
  
  	if (j < n_clobbers || recog_op_alt[i][alt].matches >= 0)
  	  implicitly_dies[REGNO (recog_data.operand[i])] = 1;
        }
  
    /* Search for first non-popped reg.  */
    for (i = FIRST_STACK_REG; i < LAST_STACK_REG + 1; i++)
      if (! implicitly_dies[i])
        break;
  
    /* If there are any other popped regs, that's an error.  */
    for (; i < LAST_STACK_REG + 1; i++)
      if (implicitly_dies[i])
        break;
  
    if (i != LAST_STACK_REG + 1)
      {
        error_for_asm (insn,
  		     "implicitly popped regs must be grouped at top of stack");
        malformed_asm = 1;
      }
  
    /* Enforce rule #3: If any input operand uses the "f" constraint, all
       output constraints must use the "&" earlyclobber.
  
       ??? Detect this more deterministically by having constrain_asm_operands
       record any earlyclobber.  */
  
    for (i = n_outputs; i < n_outputs + n_inputs; i++)
      if (recog_op_alt[i][alt].matches == -1)
        {
  	int j;
  
  	for (j = 0; j < n_outputs; j++)
  	  if (operands_match_p (recog_data.operand[j], recog_data.operand[i]))
  	    {
  	      error_for_asm (insn,
  			     "output operand %d must use `&' constraint", j);
  	      malformed_asm = 1;
  	    }
        }
  
    if (malformed_asm)
      {
        /* Avoid further trouble with this insn.  */
        PATTERN (insn) = gen_rtx_USE (VOIDmode, const0_rtx);
        any_malformed_asm = true;
        return 0;
      }
  
    return 1;
  }
  
  /* Calculate the number of inputs and outputs in BODY, an
     asm_operands.  N_OPERANDS is the total number of operands, and
     N_INPUTS and N_OUTPUTS are pointers to ints into which the results are
     placed.  */
  
  static int
  get_asm_operand_n_inputs (rtx body)
  {
    if (GET_CODE (body) == SET && GET_CODE (SET_SRC (body)) == ASM_OPERANDS)
      return ASM_OPERANDS_INPUT_LENGTH (SET_SRC (body));
  
    else if (GET_CODE (body) == ASM_OPERANDS)
      return ASM_OPERANDS_INPUT_LENGTH (body);
  
    else if (GET_CODE (body) == PARALLEL
  	   && GET_CODE (XVECEXP (body, 0, 0)) == SET)
      return ASM_OPERANDS_INPUT_LENGTH (SET_SRC (XVECEXP (body, 0, 0)));
  
    else if (GET_CODE (body) == PARALLEL
  	   && GET_CODE (XVECEXP (body, 0, 0)) == ASM_OPERANDS)
      return ASM_OPERANDS_INPUT_LENGTH (XVECEXP (body, 0, 0));
  
    abort ();
  }
  
  /* If current function returns its result in an fp stack register,
     return the REG.  Otherwise, return 0.  */
  
  static rtx
  stack_result (tree decl)
  {
    rtx result;
  
    /* If the value is supposed to be returned in memory, then clearly
       it is not returned in a stack register.  */
    if (aggregate_value_p (DECL_RESULT (decl), decl))
      return 0;
  
    result = DECL_RTL_IF_SET (DECL_RESULT (decl));
    if (result != 0)
      {
  #ifdef FUNCTION_OUTGOING_VALUE
        result
  	= FUNCTION_OUTGOING_VALUE (TREE_TYPE (DECL_RESULT (decl)), decl);
  #else
        result = FUNCTION_VALUE (TREE_TYPE (DECL_RESULT (decl)), decl);
  #endif
      }
  
    return result != 0 && STACK_REG_P (result) ? result : 0;
  }
  
  
  /*
   * This section deals with stack register substitution, and forms the second
   * pass over the RTL.
   */
  
  /* Replace REG, which is a pointer to a stack reg RTX, with an RTX for
     the desired hard REGNO.  */
  
  static void
  replace_reg (rtx *reg, int regno)
  {
    if (regno < FIRST_STACK_REG || regno > LAST_STACK_REG
        || ! STACK_REG_P (*reg))
      abort ();
  
    switch (GET_MODE_CLASS (GET_MODE (*reg)))
      {
      default: abort ();
      case MODE_FLOAT:
      case MODE_COMPLEX_FLOAT:;
      }
  
    *reg = FP_MODE_REG (regno, GET_MODE (*reg));
  }
  
  /* Remove a note of type NOTE, which must be found, for register
     number REGNO from INSN.  Remove only one such note.  */
  
  static void
  remove_regno_note (rtx insn, enum reg_note note, unsigned int regno)
  {
    rtx *note_link, this;
  
    note_link = &REG_NOTES (insn);
    for (this = *note_link; this; this = XEXP (this, 1))
      if (REG_NOTE_KIND (this) == note
  	&& REG_P (XEXP (this, 0)) && REGNO (XEXP (this, 0)) == regno)
        {
  	*note_link = XEXP (this, 1);
  	return;
        }
      else
        note_link = &XEXP (this, 1);
  
    abort ();
  }
  
  /* Find the hard register number of virtual register REG in REGSTACK.
     The hard register number is relative to the top of the stack.  -1 is
     returned if the register is not found.  */
  
  static int
  get_hard_regnum (stack regstack, rtx reg)
  {
    int i;
  
    if (! STACK_REG_P (reg))
      abort ();
  
    for (i = regstack->top; i >= 0; i--)
      if (regstack->reg[i] == REGNO (reg))
        break;
  
    return i >= 0 ? (FIRST_STACK_REG + regstack->top - i) : -1;
  }
  
  /* Emit an insn to pop virtual register REG before or after INSN.
     REGSTACK is the stack state after INSN and is updated to reflect this
     pop.  WHEN is either emit_insn_before or emit_insn_after.  A pop insn
     is represented as a SET whose destination is the register to be popped
     and source is the top of stack.  A death note for the top of stack
     cases the movdf pattern to pop.  */
  
  static rtx
  emit_pop_insn (rtx insn, stack regstack, rtx reg, enum emit_where where)
  {
    rtx pop_insn, pop_rtx;
    int hard_regno;
  
    /* For complex types take care to pop both halves.  These may survive in
       CLOBBER and USE expressions.  */
    if (COMPLEX_MODE_P (GET_MODE (reg)))
      {
        rtx reg1 = FP_MODE_REG (REGNO (reg), DFmode);
        rtx reg2 = FP_MODE_REG (REGNO (reg) + 1, DFmode);
  
        pop_insn = NULL_RTX;
        if (get_hard_regnum (regstack, reg1) >= 0)
  	pop_insn = emit_pop_insn (insn, regstack, reg1, where);
        if (get_hard_regnum (regstack, reg2) >= 0)
  	pop_insn = emit_pop_insn (insn, regstack, reg2, where);
        if (!pop_insn)
  	abort ();
        return pop_insn;
      }
  
    hard_regno = get_hard_regnum (regstack, reg);
  
    if (hard_regno < FIRST_STACK_REG)
      abort ();
  
    pop_rtx = gen_rtx_SET (VOIDmode, FP_MODE_REG (hard_regno, DFmode),
  			 FP_MODE_REG (FIRST_STACK_REG, DFmode));
  
    if (where == EMIT_AFTER)
      pop_insn = emit_insn_after (pop_rtx, insn);
    else
      pop_insn = emit_insn_before (pop_rtx, insn);
  
    REG_NOTES (pop_insn)
      = gen_rtx_EXPR_LIST (REG_DEAD, FP_MODE_REG (FIRST_STACK_REG, DFmode),
  			 REG_NOTES (pop_insn));
  
    regstack->reg[regstack->top - (hard_regno - FIRST_STACK_REG)]
      = regstack->reg[regstack->top];
    regstack->top -= 1;
    CLEAR_HARD_REG_BIT (regstack->reg_set, REGNO (reg));
  
    return pop_insn;
  }
  
  /* Emit an insn before or after INSN to swap virtual register REG with
     the top of stack.  REGSTACK is the stack state before the swap, and
     is updated to reflect the swap.  A swap insn is represented as a
     PARALLEL of two patterns: each pattern moves one reg to the other.
  
     If REG is already at the top of the stack, no insn is emitted.  */
  
  static void
  emit_swap_insn (rtx insn, stack regstack, rtx reg)
  {
    int hard_regno;
    rtx swap_rtx;
    int tmp, other_reg;		/* swap regno temps */
    rtx i1;			/* the stack-reg insn prior to INSN */
    rtx i1set = NULL_RTX;		/* the SET rtx within I1 */
  
    hard_regno = get_hard_regnum (regstack, reg);
  
    if (hard_regno < FIRST_STACK_REG)
      abort ();
    if (hard_regno == FIRST_STACK_REG)
      return;
  
    other_reg = regstack->top - (hard_regno - FIRST_STACK_REG);
  
    tmp = regstack->reg[other_reg];
    regstack->reg[other_reg] = regstack->reg[regstack->top];
    regstack->reg[regstack->top] = tmp;
  
    /* Find the previous insn involving stack regs, but don't pass a
       block boundary.  */
    i1 = NULL;
    if (current_block && insn != BB_HEAD (current_block))
      {
        rtx tmp = PREV_INSN (insn);
        rtx limit = PREV_INSN (BB_HEAD (current_block));
        while (tmp != limit)
  	{
  	  if (GET_CODE (tmp) == CODE_LABEL
  	      || GET_CODE (tmp) == CALL_INSN
  	      || NOTE_INSN_BASIC_BLOCK_P (tmp)
  	      || (GET_CODE (tmp) == INSN
  		  && stack_regs_mentioned (tmp)))
  	    {
  	      i1 = tmp;
  	      break;
  	    }
  	  tmp = PREV_INSN (tmp);
  	}
      }
  
    if (i1 != NULL_RTX
        && (i1set = single_set (i1)) != NULL_RTX)
      {
        rtx i1src = *get_true_reg (&SET_SRC (i1set));
        rtx i1dest = *get_true_reg (&SET_DEST (i1set));
  
        /* If the previous register stack push was from the reg we are to
  	 swap with, omit the swap.  */
  
        if (GET_CODE (i1dest) == REG && REGNO (i1dest) == FIRST_STACK_REG
  	  && GET_CODE (i1src) == REG
  	  && REGNO (i1src) == (unsigned) hard_regno - 1
  	  && find_regno_note (i1, REG_DEAD, FIRST_STACK_REG) == NULL_RTX)
  	return;
  
        /* If the previous insn wrote to the reg we are to swap with,
  	 omit the swap.  */
  
        if (GET_CODE (i1dest) == REG && REGNO (i1dest) == (unsigned) hard_regno
  	  && GET_CODE (i1src) == REG && REGNO (i1src) == FIRST_STACK_REG
  	  && find_regno_note (i1, REG_DEAD, FIRST_STACK_REG) == NULL_RTX)
  	return;
      }
  
    swap_rtx = gen_swapxf (FP_MODE_REG (hard_regno, XFmode),
  			 FP_MODE_REG (FIRST_STACK_REG, XFmode));
  
    if (i1)
      emit_insn_after (swap_rtx, i1);
    else if (current_block)
      emit_insn_before (swap_rtx, BB_HEAD (current_block));
    else
      emit_insn_before (swap_rtx, insn);
  }
  
  /* Handle a move to or from a stack register in PAT, which is in INSN.
     REGSTACK is the current stack.  Return whether a control flow insn
     was deleted in the process.  */
  
  static bool
  move_for_stack_reg (rtx insn, stack regstack, rtx pat)
  {
    rtx *psrc =  get_true_reg (&SET_SRC (pat));
    rtx *pdest = get_true_reg (&SET_DEST (pat));
    rtx src, dest;
    rtx note;
    bool control_flow_insn_deleted = false;
  
    src = *psrc; dest = *pdest;
  
    if (STACK_REG_P (src) && STACK_REG_P (dest))
      {
        /* Write from one stack reg to another.  If SRC dies here, then
  	 just change the register mapping and delete the insn.  */
  
        note = find_regno_note (insn, REG_DEAD, REGNO (src));
        if (note)
  	{
  	  int i;
  
  	  /* If this is a no-op move, there must not be a REG_DEAD note.  */
  	  if (REGNO (src) == REGNO (dest))
  	    abort ();
  
  	  for (i = regstack->top; i >= 0; i--)
  	    if (regstack->reg[i] == REGNO (src))
  	      break;
  
  	  /* The destination must be dead, or life analysis is borked.  */
  	  if (get_hard_regnum (regstack, dest) >= FIRST_STACK_REG)
  	    abort ();
  
  	  /* If the source is not live, this is yet another case of
  	     uninitialized variables.  Load up a NaN instead.  */
  	  if (i < 0)
  	    {
  	      PATTERN (insn) = pat
  	        = gen_rtx_SET (VOIDmode,
  			       FP_MODE_REG (REGNO (dest), SFmode), nan);
  	      INSN_CODE (insn) = -1;
  	      return move_for_stack_reg (insn, regstack, pat);
  	    }
  
  	  /* It is possible that the dest is unused after this insn.
  	     If so, just pop the src.  */
  
  	  if (find_regno_note (insn, REG_UNUSED, REGNO (dest)))
  	    emit_pop_insn (insn, regstack, src, EMIT_AFTER);
  	  else
  	    {
  	      regstack->reg[i] = REGNO (dest);
  	      SET_HARD_REG_BIT (regstack->reg_set, REGNO (dest));
  	      CLEAR_HARD_REG_BIT (regstack->reg_set, REGNO (src));
  	    }
  
  	  control_flow_insn_deleted |= control_flow_insn_p (insn);
  	  delete_insn (insn);
  	  return control_flow_insn_deleted;
  	}
  
        /* The source reg does not die.  */
  
        /* If this appears to be a no-op move, delete it, or else it
  	 will confuse the machine description output patterns. But if
  	 it is REG_UNUSED, we must pop the reg now, as per-insn processing
  	 for REG_UNUSED will not work for deleted insns.  */
  
        if (REGNO (src) == REGNO (dest))
  	{
  	  if (find_regno_note (insn, REG_UNUSED, REGNO (dest)))
  	    emit_pop_insn (insn, regstack, dest, EMIT_AFTER);
  
  	  control_flow_insn_deleted |= control_flow_insn_p (insn);
  	  delete_insn (insn);
  	  return control_flow_insn_deleted;
  	}
  
        /* The destination ought to be dead.  */
        if (get_hard_regnum (regstack, dest) >= FIRST_STACK_REG)
  	abort ();
  
        replace_reg (psrc, get_hard_regnum (regstack, src));
  
        regstack->reg[++regstack->top] = REGNO (dest);
        SET_HARD_REG_BIT (regstack->reg_set, REGNO (dest));
        replace_reg (pdest, FIRST_STACK_REG);
      }
    else if (STACK_REG_P (src))
      {
        /* Save from a stack reg to MEM, or possibly integer reg.  Since
  	 only top of stack may be saved, emit an exchange first if
  	 needs be.  */
  
        emit_swap_insn (insn, regstack, src);
  
        note = find_regno_note (insn, REG_DEAD, REGNO (src));
        if (note)
  	{
  	  replace_reg (&XEXP (note, 0), FIRST_STACK_REG);
  	  regstack->top--;
  	  CLEAR_HARD_REG_BIT (regstack->reg_set, REGNO (src));
  	}
        else if ((GET_MODE (src) == XFmode)
  	       && regstack->top < REG_STACK_SIZE - 1)
  	{
  	  /* A 387 cannot write an XFmode value to a MEM without
  	     clobbering the source reg.  The output code can handle
  	     this by reading back the value from the MEM.
  	     But it is more efficient to use a temp register if one is
  	     available.  Push the source value here if the register
  	     stack is not full, and then write the value to memory via
  	     a pop.  */
  	  rtx push_rtx, push_insn;
  	  rtx top_stack_reg = FP_MODE_REG (FIRST_STACK_REG, GET_MODE (src));
  
  	  push_rtx = gen_movxf (top_stack_reg, top_stack_reg);
  	  push_insn = emit_insn_before (push_rtx, insn);
  	  REG_NOTES (insn) = gen_rtx_EXPR_LIST (REG_DEAD, top_stack_reg,
  						REG_NOTES (insn));
  	}
  
        replace_reg (psrc, FIRST_STACK_REG);
      }
    else if (STACK_REG_P (dest))
      {
        /* Load from MEM, or possibly integer REG or constant, into the
  	 stack regs.  The actual target is always the top of the
  	 stack. The stack mapping is changed to reflect that DEST is
  	 now at top of stack.  */
  
        /* The destination ought to be dead.  */
        if (get_hard_regnum (regstack, dest) >= FIRST_STACK_REG)
  	abort ();
  
        if (regstack->top >= REG_STACK_SIZE)
  	abort ();
  
        regstack->reg[++regstack->top] = REGNO (dest);
        SET_HARD_REG_BIT (regstack->reg_set, REGNO (dest));
        replace_reg (pdest, FIRST_STACK_REG);
      }
    else
      abort ();
  
    return control_flow_insn_deleted;
  }
  
  /* Swap the condition on a branch, if there is one.  Return true if we
     found a condition to swap.  False if the condition was not used as
     such.  */
  
  static int
  swap_rtx_condition_1 (rtx pat)
  {
    const char *fmt;
    int i, r = 0;
  
    if (GET_RTX_CLASS (GET_CODE (pat)) == '<')
      {
        PUT_CODE (pat, swap_condition (GET_CODE (pat)));
        r = 1;
      }
    else
      {
        fmt = GET_RTX_FORMAT (GET_CODE (pat));
        for (i = GET_RTX_LENGTH (GET_CODE (pat)) - 1; i >= 0; i--)
  	{
  	  if (fmt[i] == 'E')
  	    {
  	      int j;
  
  	      for (j = XVECLEN (pat, i) - 1; j >= 0; j--)
  		r |= swap_rtx_condition_1 (XVECEXP (pat, i, j));
  	    }
  	  else if (fmt[i] == 'e')
  	    r |= swap_rtx_condition_1 (XEXP (pat, i));
  	}
      }
  
    return r;
  }
  
  static int
  swap_rtx_condition (rtx insn)
  {
    rtx pat = PATTERN (insn);
  
    /* We're looking for a single set to cc0 or an HImode temporary.  */
  
    if (GET_CODE (pat) == SET
        && GET_CODE (SET_DEST (pat)) == REG
        && REGNO (SET_DEST (pat)) == FLAGS_REG)
      {
        insn = next_flags_user (insn);
        if (insn == NULL_RTX)
  	return 0;
        pat = PATTERN (insn);
      }
  
    /* See if this is, or ends in, a fnstsw, aka unspec 9.  If so, we're
       not doing anything with the cc value right now.  We may be able to
       search for one though.  */
  
    if (GET_CODE (pat) == SET
        && GET_CODE (SET_SRC (pat)) == UNSPEC
        && XINT (SET_SRC (pat), 1) == UNSPEC_FNSTSW)
      {
        rtx dest = SET_DEST (pat);
  
        /* Search forward looking for the first use of this value.
  	 Stop at block boundaries.  */
        while (insn != BB_END (current_block))
  	{
  	  insn = NEXT_INSN (insn);
  	  if (INSN_P (insn) && reg_mentioned_p (dest, insn))
  	    break;
  	  if (GET_CODE (insn) == CALL_INSN)
  	    return 0;
  	}
  
        /* So we've found the insn using this value.  If it is anything
  	 other than sahf, aka unspec 10, or the value does not die
  	 (meaning we'd have to search further), then we must give up.  */
        pat = PATTERN (insn);
        if (GET_CODE (pat) != SET
  	  || GET_CODE (SET_SRC (pat)) != UNSPEC
  	  || XINT (SET_SRC (pat), 1) != UNSPEC_SAHF
  	  || ! dead_or_set_p (insn, dest))
  	return 0;
  
        /* Now we are prepared to handle this as a normal cc0 setter.  */
        insn = next_flags_user (insn);
        if (insn == NULL_RTX)
  	return 0;
        pat = PATTERN (insn);
      }
  
    if (swap_rtx_condition_1 (pat))
      {
        int fail = 0;
        INSN_CODE (insn) = -1;
        if (recog_memoized (insn) == -1)
  	fail = 1;
        /* In case the flags don't die here, recurse to try fix
           following user too.  */
        else if (! dead_or_set_p (insn, ix86_flags_rtx))
  	{
  	  insn = next_flags_user (insn);
  	  if (!insn || !swap_rtx_condition (insn))
  	    fail = 1;
  	}
        if (fail)
  	{
  	  swap_rtx_condition_1 (pat);
  	  return 0;
  	}
        return 1;
      }
    return 0;
  }
  
  /* Handle a comparison.  Special care needs to be taken to avoid
     causing comparisons that a 387 cannot do correctly, such as EQ.
  
     Also, a pop insn may need to be emitted.  The 387 does have an
     `fcompp' insn that can pop two regs, but it is sometimes too expensive
     to do this - a `fcomp' followed by a `fstpl %st(0)' may be easier to
     set up.  */
  
  static void
  compare_for_stack_reg (rtx insn, stack regstack, rtx pat_src)
  {
    rtx *src1, *src2;
    rtx src1_note, src2_note;
    rtx flags_user;
  
    src1 = get_true_reg (&XEXP (pat_src, 0));
    src2 = get_true_reg (&XEXP (pat_src, 1));
    flags_user = next_flags_user (insn);
  
    /* ??? If fxch turns out to be cheaper than fstp, give priority to
       registers that die in this insn - move those to stack top first.  */
    if ((! STACK_REG_P (*src1)
         || (STACK_REG_P (*src2)
  	   && get_hard_regnum (regstack, *src2) == FIRST_STACK_REG))
        && swap_rtx_condition (insn))
      {
        rtx temp;
        temp = XEXP (pat_src, 0);
        XEXP (pat_src, 0) = XEXP (pat_src, 1);
        XEXP (pat_src, 1) = temp;
  
        src1 = get_true_reg (&XEXP (pat_src, 0));
        src2 = get_true_reg (&XEXP (pat_src, 1));
  
        INSN_CODE (insn) = -1;
      }
  
    /* We will fix any death note later.  */
  
    src1_note = find_regno_note (insn, REG_DEAD, REGNO (*src1));
  
    if (STACK_REG_P (*src2))
      src2_note = find_regno_note (insn, REG_DEAD, REGNO (*src2));
    else
      src2_note = NULL_RTX;
  
    emit_swap_insn (insn, regstack, *src1);
  
    replace_reg (src1, FIRST_STACK_REG);
  
    if (STACK_REG_P (*src2))
      replace_reg (src2, get_hard_regnum (regstack, *src2));
  
    if (src1_note)
      {
        pop_stack (regstack, REGNO (XEXP (src1_note, 0)));
        replace_reg (&XEXP (src1_note, 0), FIRST_STACK_REG);
      }
  
    /* If the second operand dies, handle that.  But if the operands are
       the same stack register, don't bother, because only one death is
       needed, and it was just handled.  */
  
    if (src2_note
        && ! (STACK_REG_P (*src1) && STACK_REG_P (*src2)
  	    && REGNO (*src1) == REGNO (*src2)))
      {
        /* As a special case, two regs may die in this insn if src2 is
  	 next to top of stack and the top of stack also dies.  Since
  	 we have already popped src1, "next to top of stack" is really
  	 at top (FIRST_STACK_REG) now.  */
  
        if (get_hard_regnum (regstack, XEXP (src2_note, 0)) == FIRST_STACK_REG
  	  && src1_note)
  	{
  	  pop_stack (regstack, REGNO (XEXP (src2_note, 0)));
  	  replace_reg (&XEXP (src2_note, 0), FIRST_STACK_REG + 1);
  	}
        else
  	{
  	  /* The 386 can only represent death of the first operand in
  	     the case handled above.  In all other cases, emit a separate
  	     pop and remove the death note from here.  */
  
  	  /* link_cc0_insns (insn); */
  
  	  remove_regno_note (insn, REG_DEAD, REGNO (XEXP (src2_note, 0)));
  
  	  emit_pop_insn (insn, regstack, XEXP (src2_note, 0),
  			 EMIT_AFTER);
  	}
      }
  }
  
  /* Substitute new registers in PAT, which is part of INSN.  REGSTACK
     is the current register layout.  Return whether a control flow insn
     was deleted in the process.  */
  
  static bool
  subst_stack_regs_pat (rtx insn, stack regstack, rtx pat)
  {
    rtx *dest, *src;
    bool control_flow_insn_deleted = false;
  
    switch (GET_CODE (pat))
      {
      case USE:
        /* Deaths in USE insns can happen in non optimizing compilation.
  	 Handle them by popping the dying register.  */
        src = get_true_reg (&XEXP (pat, 0));
        if (STACK_REG_P (*src)
  	  && find_regno_note (insn, REG_DEAD, REGNO (*src)))
  	{
  	  emit_pop_insn (insn, regstack, *src, EMIT_AFTER);
  	  return control_flow_insn_deleted;
  	}
        /* ??? Uninitialized USE should not happen.  */
        else if (get_hard_regnum (regstack, *src) == -1)
  	abort ();
        break;
  
      case CLOBBER:
        {
  	rtx note;
  
  	dest = get_true_reg (&XEXP (pat, 0));
  	if (STACK_REG_P (*dest))
  	  {
  	    note = find_reg_note (insn, REG_DEAD, *dest);
  
  	    if (pat != PATTERN (insn))
  	      {
  		/* The fix_truncdi_1 pattern wants to be able to allocate
  		   it's own scratch register.  It does this by clobbering
  		   an fp reg so that it is assured of an empty reg-stack
  		   register.  If the register is live, kill it now.
  		   Remove the DEAD/UNUSED note so we don't try to kill it
  		   later too.  */
  
  		if (note)
  		  emit_pop_insn (insn, regstack, *dest, EMIT_BEFORE);
  		else
  		  {
  		    note = find_reg_note (insn, REG_UNUSED, *dest);
  		    if (!note)
  		      abort ();
  		  }
  		remove_note (insn, note);
  		replace_reg (dest, FIRST_STACK_REG + 1);
  	      }
  	    else
  	      {
  		/* A top-level clobber with no REG_DEAD, and no hard-regnum
  		   indicates an uninitialized value.  Because reload removed
  		   all other clobbers, this must be due to a function
  		   returning without a value.  Load up a NaN.  */
  
  		if (! note
  		    && get_hard_regnum (regstack, *dest) == -1)
  		  {
  		    pat = gen_rtx_SET (VOIDmode,
  				       FP_MODE_REG (REGNO (*dest), SFmode),
  				       nan);
  		    PATTERN (insn) = pat;
  		    control_flow_insn_deleted |= move_for_stack_reg (insn, regstack, pat);
  		  }
  		if (! note && COMPLEX_MODE_P (GET_MODE (*dest))
  		    && get_hard_regnum (regstack, FP_MODE_REG (REGNO (*dest), DFmode)) == -1)
  		  {
  		    pat = gen_rtx_SET (VOIDmode,
  				       FP_MODE_REG (REGNO (*dest) + 1, SFmode),
  				       nan);
  		    PATTERN (insn) = pat;
  		    control_flow_insn_deleted |= move_for_stack_reg (insn, regstack, pat);
  		  }
  	      }
  	  }
  	break;
        }
  
      case SET:
        {
  	rtx *src1 = (rtx *) 0, *src2;
  	rtx src1_note, src2_note;
  	rtx pat_src;
  
  	dest = get_true_reg (&SET_DEST (pat));
  	src  = get_true_reg (&SET_SRC (pat));
  	pat_src = SET_SRC (pat);
  
  	/* See if this is a `movM' pattern, and handle elsewhere if so.  */
  	if (STACK_REG_P (*src)
  	    || (STACK_REG_P (*dest)
  		&& (GET_CODE (*src) == REG || GET_CODE (*src) == MEM
  		    || GET_CODE (*src) == CONST_DOUBLE)))
  	  {
  	    control_flow_insn_deleted |= move_for_stack_reg (insn, regstack, pat);
  	    break;
  	  }
  
  	switch (GET_CODE (pat_src))
  	  {
  	  case COMPARE:
  	    compare_for_stack_reg (insn, regstack, pat_src);
  	    break;
  
  	  case CALL:
  	    {
  	      int count;
  	      for (count = HARD_REGNO_NREGS (REGNO (*dest), GET_MODE (*dest));
  		   --count >= 0;)
  		{
  		  regstack->reg[++regstack->top] = REGNO (*dest) + count;
  		  SET_HARD_REG_BIT (regstack->reg_set, REGNO (*dest) + count);
  		}
  	    }
  	    replace_reg (dest, FIRST_STACK_REG);
  	    break;
  
  	  case REG:
  	    /* This is a `tstM2' case.  */
  	    if (*dest != cc0_rtx)
  	      abort ();
  	    src1 = src;
  
  	    /* Fall through.  */
  
  	  case FLOAT_TRUNCATE:
  	  case SQRT:
  	  case ABS:
  	  case NEG:
  	    /* These insns only operate on the top of the stack. DEST might
  	       be cc0_rtx if we're processing a tstM pattern. Also, it's
  	       possible that the tstM case results in a REG_DEAD note on the
  	       source.  */
  
  	    if (src1 == 0)
  	      src1 = get_true_reg (&XEXP (pat_src, 0));
  
  	    emit_swap_insn (insn, regstack, *src1);
  
  	    src1_note = find_regno_note (insn, REG_DEAD, REGNO (*src1));
  
  	    if (STACK_REG_P (*dest))
  	      replace_reg (dest, FIRST_STACK_REG);
  
  	    if (src1_note)
  	      {
  		replace_reg (&XEXP (src1_note, 0), FIRST_STACK_REG);
  		regstack->top--;
  		CLEAR_HARD_REG_BIT (regstack->reg_set, REGNO (*src1));
  	      }
  
  	    replace_reg (src1, FIRST_STACK_REG);
  	    break;
  
  	  case MINUS:
  	  case DIV:
  	    /* On i386, reversed forms of subM3 and divM3 exist for
  	       MODE_FLOAT, so the same code that works for addM3 and mulM3
  	       can be used.  */
  	  case MULT:
  	  case PLUS:
  	    /* These insns can accept the top of stack as a destination
  	       from a stack reg or mem, or can use the top of stack as a
  	       source and some other stack register (possibly top of stack)
  	       as a destination.  */
  
  	    src1 = get_true_reg (&XEXP (pat_src, 0));
  	    src2 = get_true_reg (&XEXP (pat_src, 1));
  
  	    /* We will fix any death note later.  */
  
  	    if (STACK_REG_P (*src1))
  	      src1_note = find_regno_note (insn, REG_DEAD, REGNO (*src1));
  	    else
  	      src1_note = NULL_RTX;
  	    if (STACK_REG_P (*src2))
  	      src2_note = find_regno_note (insn, REG_DEAD, REGNO (*src2));
  	    else
  	      src2_note = NULL_RTX;
  
  	    /* If either operand is not a stack register, then the dest
  	       must be top of stack.  */
  
  	    if (! STACK_REG_P (*src1) || ! STACK_REG_P (*src2))
  	      emit_swap_insn (insn, regstack, *dest);
  	    else
  	      {
  		/* Both operands are REG.  If neither operand is already
  		   at the top of stack, choose to make the one that is the dest
  		   the new top of stack.  */
  
  		int src1_hard_regnum, src2_hard_regnum;
  
  		src1_hard_regnum = get_hard_regnum (regstack, *src1);
  		src2_hard_regnum = get_hard_regnum (regstack, *src2);
  		if (src1_hard_regnum == -1 || src2_hard_regnum == -1)
  		  abort ();
  
  		if (src1_hard_regnum != FIRST_STACK_REG
  		    && src2_hard_regnum != FIRST_STACK_REG)
  		  emit_swap_insn (insn, regstack, *dest);
  	      }
  
  	    if (STACK_REG_P (*src1))
  	      replace_reg (src1, get_hard_regnum (regstack, *src1));
  	    if (STACK_REG_P (*src2))
  	      replace_reg (src2, get_hard_regnum (regstack, *src2));
  
  	    if (src1_note)
  	      {
  		rtx src1_reg = XEXP (src1_note, 0);
  
  		/* If the register that dies is at the top of stack, then
  		   the destination is somewhere else - merely substitute it.
  		   But if the reg that dies is not at top of stack, then
  		   move the top of stack to the dead reg, as though we had
  		   done the insn and then a store-with-pop.  */
  
  		if (REGNO (src1_reg) == regstack->reg[regstack->top])
  		  {
  		    SET_HARD_REG_BIT (regstack->reg_set, REGNO (*dest));
  		    replace_reg (dest, get_hard_regnum (regstack, *dest));
  		  }
  		else
  		  {
  		    int regno = get_hard_regnum (regstack, src1_reg);
  
  		    SET_HARD_REG_BIT (regstack->reg_set, REGNO (*dest));
  		    replace_reg (dest, regno);
  
  		    regstack->reg[regstack->top - (regno - FIRST_STACK_REG)]
  		      = regstack->reg[regstack->top];
  		  }
  
  		CLEAR_HARD_REG_BIT (regstack->reg_set,
  				    REGNO (XEXP (src1_note, 0)));
  		replace_reg (&XEXP (src1_note, 0), FIRST_STACK_REG);
  		regstack->top--;
  	      }
  	    else if (src2_note)
  	      {
  		rtx src2_reg = XEXP (src2_note, 0);
  		if (REGNO (src2_reg) == regstack->reg[regstack->top])
  		  {
  		    SET_HARD_REG_BIT (regstack->reg_set, REGNO (*dest));
  		    replace_reg (dest, get_hard_regnum (regstack, *dest));
  		  }
  		else
  		  {
  		    int regno = get_hard_regnum (regstack, src2_reg);
  
  		    SET_HARD_REG_BIT (regstack->reg_set, REGNO (*dest));
  		    replace_reg (dest, regno);
  
  		    regstack->reg[regstack->top - (regno - FIRST_STACK_REG)]
  		      = regstack->reg[regstack->top];
  		  }
  
  		CLEAR_HARD_REG_BIT (regstack->reg_set,
  				    REGNO (XEXP (src2_note, 0)));
  		replace_reg (&XEXP (src2_note, 0), FIRST_STACK_REG);
  		regstack->top--;
  	      }
  	    else
  	      {
  		SET_HARD_REG_BIT (regstack->reg_set, REGNO (*dest));
  		replace_reg (dest, get_hard_regnum (regstack, *dest));
  	      }
  
  	    /* Keep operand 1 matching with destination.  */
  	    if (GET_RTX_CLASS (GET_CODE (pat_src)) == 'c'
  		&& REG_P (*src1) && REG_P (*src2)
  		&& REGNO (*src1) != REGNO (*dest))
  	     {
  		int tmp = REGNO (*src1);
  		replace_reg (src1, REGNO (*src2));
  		replace_reg (src2, tmp);
  	     }
  	    break;
  
  	  case UNSPEC:
  	    switch (XINT (pat_src, 1))
  	      {
  	      case UNSPEC_SIN:
  	      case UNSPEC_COS:
  	      case UNSPEC_FRNDINT:
  	      case UNSPEC_F2XM1:
  		/* These insns only operate on the top of the stack.  */
  
  		src1 = get_true_reg (&XVECEXP (pat_src, 0, 0));
  
  		emit_swap_insn (insn, regstack, *src1);
  
  		src1_note = find_regno_note (insn, REG_DEAD, REGNO (*src1));
  
  		if (STACK_REG_P (*dest))
  		  replace_reg (dest, FIRST_STACK_REG);
  
  		if (src1_note)
  		  {
  		    replace_reg (&XEXP (src1_note, 0), FIRST_STACK_REG);
  		    regstack->top--;
  		    CLEAR_HARD_REG_BIT (regstack->reg_set, REGNO (*src1));
  		  }
  
  		replace_reg (src1, FIRST_STACK_REG);
  		break;
  
  	      case UNSPEC_FPATAN:
  	      case UNSPEC_FYL2X:
  	      case UNSPEC_FSCALE:
  		/* These insns operate on the top two stack slots.  */
  
  		src1 = get_true_reg (&XVECEXP (pat_src, 0, 0));
  		src2 = get_true_reg (&XVECEXP (pat_src, 0, 1));
  
  		src1_note = find_regno_note (insn, REG_DEAD, REGNO (*src1));
  		src2_note = find_regno_note (insn, REG_DEAD, REGNO (*src2));
  
  		{
  		  struct stack_def temp_stack;
  		  int regno, j, k, temp;
  
  		  temp_stack = *regstack;
  
  		  /* Place operand 1 at the top of stack.  */
  		  regno = get_hard_regnum (&temp_stack, *src1);
  		  if (regno < 0)
  		    abort ();
  		  if (regno != FIRST_STACK_REG)
  		    {
  		      k = temp_stack.top - (regno - FIRST_STACK_REG);
  		      j = temp_stack.top;
  
  		      temp = temp_stack.reg[k];
  		      temp_stack.reg[k] = temp_stack.reg[j];
  		      temp_stack.reg[j] = temp;
  		    }
  
  		  /* Place operand 2 next on the stack.  */
  		  regno = get_hard_regnum (&temp_stack, *src2);
  		  if (regno < 0)
  		    abort ();
  		  if (regno != FIRST_STACK_REG + 1)
  		    {
  		      k = temp_stack.top - (regno - FIRST_STACK_REG);
  		      j = temp_stack.top - 1;
  
  		      temp = temp_stack.reg[k];
  		      temp_stack.reg[k] = temp_stack.reg[j];
  		      temp_stack.reg[j] = temp;
  		    }
  
  		  change_stack (insn, regstack, &temp_stack, EMIT_BEFORE);
  		}
  
  		replace_reg (src1, FIRST_STACK_REG);
  		replace_reg (src2, FIRST_STACK_REG + 1);
  
  		if (src1_note)
  		  replace_reg (&XEXP (src1_note, 0), FIRST_STACK_REG);
  		if (src2_note)
  		  replace_reg (&XEXP (src2_note, 0), FIRST_STACK_REG + 1);
  
  		/* Pop both input operands from the stack.  */
  		CLEAR_HARD_REG_BIT (regstack->reg_set,
  				    regstack->reg[regstack->top]);
  		CLEAR_HARD_REG_BIT (regstack->reg_set,
  				    regstack->reg[regstack->top - 1]);
  		regstack->top -= 2;
  
  		/* Push the result back onto the stack.  */
  		regstack->reg[++regstack->top] = REGNO (*dest);
  		SET_HARD_REG_BIT (regstack->reg_set, REGNO (*dest));
  		replace_reg (dest, FIRST_STACK_REG);
  		break;
  
  	      case UNSPEC_SAHF:
  		/* (unspec [(unspec [(compare)] UNSPEC_FNSTSW)] UNSPEC_SAHF)
  		   The combination matches the PPRO fcomi instruction.  */
  
  		pat_src = XVECEXP (pat_src, 0, 0);
  		if (GET_CODE (pat_src) != UNSPEC
  		    || XINT (pat_src, 1) != UNSPEC_FNSTSW)
  		  abort ();
  		/* Fall through.  */
  
  	      case UNSPEC_FNSTSW:
  		/* Combined fcomp+fnstsw generated for doing well with
  		   CSE.  When optimizing this would have been broken
  		   up before now.  */
  
  		pat_src = XVECEXP (pat_src, 0, 0);
  		if (GET_CODE (pat_src) != COMPARE)
  		  abort ();
  
  		compare_for_stack_reg (insn, regstack, pat_src);
  		break;
  
  	      default:
  		abort ();
  	      }
  	    break;
  
  	  case IF_THEN_ELSE:
  	    /* This insn requires the top of stack to be the destination.  */
  
  	    src1 = get_true_reg (&XEXP (pat_src, 1));
  	    src2 = get_true_reg (&XEXP (pat_src, 2));
  
  	    src1_note = find_regno_note (insn, REG_DEAD, REGNO (*src1));
  	    src2_note = find_regno_note (insn, REG_DEAD, REGNO (*src2));
  
  	    /* If the comparison operator is an FP comparison operator,
  	       it is handled correctly by compare_for_stack_reg () who
  	       will move the destination to the top of stack. But if the
  	       comparison operator is not an FP comparison operator, we
  	       have to handle it here.  */
  	    if (get_hard_regnum (regstack, *dest) >= FIRST_STACK_REG
  		&& REGNO (*dest) != regstack->reg[regstack->top])
  	      {
  		/* In case one of operands is the top of stack and the operands
  		   dies, it is safe to make it the destination operand by
  		   reversing the direction of cmove and avoid fxch.  */
  		if ((REGNO (*src1) == regstack->reg[regstack->top]
  		     && src1_note)
  		    || (REGNO (*src2) == regstack->reg[regstack->top]
  			&& src2_note))
  		  {
  		    int idx1 = (get_hard_regnum (regstack, *src1)
  				- FIRST_STACK_REG);
  		    int idx2 = (get_hard_regnum (regstack, *src2)
  				- FIRST_STACK_REG);
  
  		    /* Make reg-stack believe that the operands are already
  		       swapped on the stack */
  		    regstack->reg[regstack->top - idx1] = REGNO (*src2);
  		    regstack->reg[regstack->top - idx2] = REGNO (*src1);
  
  		    /* Reverse condition to compensate the operand swap.
  		       i386 do have comparison always reversible.  */
  		    PUT_CODE (XEXP (pat_src, 0),
  			      reversed_comparison_code (XEXP (pat_src, 0), insn));
  		  }
  		else
  	          emit_swap_insn (insn, regstack, *dest);
  	      }
  
  	    {
  	      rtx src_note [3];
  	      int i;
  
  	      src_note[0] = 0;
  	      src_note[1] = src1_note;
  	      src_note[2] = src2_note;
  
  	      if (STACK_REG_P (*src1))
  		replace_reg (src1, get_hard_regnum (regstack, *src1));
  	      if (STACK_REG_P (*src2))
  		replace_reg (src2, get_hard_regnum (regstack, *src2));
  
  	      for (i = 1; i <= 2; i++)
  		if (src_note [i])
  		  {
  		    int regno = REGNO (XEXP (src_note[i], 0));
  
  		    /* If the register that dies is not at the top of
  		       stack, then move the top of stack to the dead reg */
  		    if (regno != regstack->reg[regstack->top])
  		      {
  			remove_regno_note (insn, REG_DEAD, regno);
  			emit_pop_insn (insn, regstack, XEXP (src_note[i], 0),
  				       EMIT_AFTER);
  		      }
  		    else
  		      /* Top of stack never dies, as it is the
  			 destination.  */
  		      abort ();
  		  }
  	    }
  
  	    /* Make dest the top of stack.  Add dest to regstack if
  	       not present.  */
  	    if (get_hard_regnum (regstack, *dest) < FIRST_STACK_REG)
  	      regstack->reg[++regstack->top] = REGNO (*dest);
  	    SET_HARD_REG_BIT (regstack->reg_set, REGNO (*dest));
  	    replace_reg (dest, FIRST_STACK_REG);
  	    break;
  
  	  default:
  	    abort ();
  	  }
  	break;
        }
  
      default:
        break;
      }
  
    return control_flow_insn_deleted;
  }
  
  /* Substitute hard regnums for any stack regs in INSN, which has
     N_INPUTS inputs and N_OUTPUTS outputs.  REGSTACK is the stack info
     before the insn, and is updated with changes made here.
  
     There are several requirements and assumptions about the use of
     stack-like regs in asm statements.  These rules are enforced by
     record_asm_stack_regs; see comments there for details.  Any
     asm_operands left in the RTL at this point may be assume to meet the
     requirements, since record_asm_stack_regs removes any problem asm.  */
  
  static void
  subst_asm_stack_regs (rtx insn, stack regstack)
  {
    rtx body = PATTERN (insn);
    int alt;
  
    rtx *note_reg;		/* Array of note contents */
    rtx **note_loc;		/* Address of REG field of each note */
    enum reg_note *note_kind;	/* The type of each note */
  
    rtx *clobber_reg = 0;
    rtx **clobber_loc = 0;
  
    struct stack_def temp_stack;
    int n_notes;
    int n_clobbers;
    rtx note;
    int i;
    int n_inputs, n_outputs;
  
    if (! check_asm_stack_operands (insn))
      return;
  
    /* Find out what the constraints required.  If no constraint
       alternative matches, that is a compiler bug: we should have caught
       such an insn in check_asm_stack_operands.  */
    extract_insn (insn);
    constrain_operands (1);
    alt = which_alternative;
  
    preprocess_constraints ();
  
    n_inputs = get_asm_operand_n_inputs (body);
    n_outputs = recog_data.n_operands - n_inputs;
  
    if (alt < 0)
      abort ();
  
    /* Strip SUBREGs here to make the following code simpler.  */
    for (i = 0; i < recog_data.n_operands; i++)
      if (GET_CODE (recog_data.operand[i]) == SUBREG
  	&& GET_CODE (SUBREG_REG (recog_data.operand[i])) == REG)
        {
  	recog_data.operand_loc[i] = & SUBREG_REG (recog_data.operand[i]);
  	recog_data.operand[i] = SUBREG_REG (recog_data.operand[i]);
        }
  
    /* Set up NOTE_REG, NOTE_LOC and NOTE_KIND.  */
  
    for (i = 0, note = REG_NOTES (insn); note; note = XEXP (note, 1))
      i++;
  
    note_reg = alloca (i * sizeof (rtx));
    note_loc = alloca (i * sizeof (rtx *));
    note_kind = alloca (i * sizeof (enum reg_note));
  
    n_notes = 0;
    for (note = REG_NOTES (insn); note; note = XEXP (note, 1))
      {
        rtx reg = XEXP (note, 0);
        rtx *loc = & XEXP (note, 0);
  
        if (GET_CODE (reg) == SUBREG && GET_CODE (SUBREG_REG (reg)) == REG)
  	{
  	  loc = & SUBREG_REG (reg);
  	  reg = SUBREG_REG (reg);
  	}
  
        if (STACK_REG_P (reg)
  	  && (REG_NOTE_KIND (note) == REG_DEAD
  	      || REG_NOTE_KIND (note) == REG_UNUSED))
  	{
  	  note_reg[n_notes] = reg;
  	  note_loc[n_notes] = loc;
  	  note_kind[n_notes] = REG_NOTE_KIND (note);
  	  n_notes++;
  	}
      }
  
    /* Set up CLOBBER_REG and CLOBBER_LOC.  */
  
    n_clobbers = 0;
  
    if (GET_CODE (body) == PARALLEL)
      {
        clobber_reg = alloca (XVECLEN (body, 0) * sizeof (rtx));
        clobber_loc = alloca (XVECLEN (body, 0) * sizeof (rtx *));
  
        for (i = 0; i < XVECLEN (body, 0); i++)
  	if (GET_CODE (XVECEXP (body, 0, i)) == CLOBBER)
  	  {
  	    rtx clobber = XVECEXP (body, 0, i);
  	    rtx reg = XEXP (clobber, 0);
  	    rtx *loc = & XEXP (clobber, 0);
  
  	    if (GET_CODE (reg) == SUBREG && GET_CODE (SUBREG_REG (reg)) == REG)
  	      {
  		loc = & SUBREG_REG (reg);
  		reg = SUBREG_REG (reg);
  	      }
  
  	    if (STACK_REG_P (reg))
  	      {
  		clobber_reg[n_clobbers] = reg;
  		clobber_loc[n_clobbers] = loc;
  		n_clobbers++;
  	      }
  	  }
      }
  
    temp_stack = *regstack;
  
    /* Put the input regs into the desired place in TEMP_STACK.  */
  
    for (i = n_outputs; i < n_outputs + n_inputs; i++)
      if (STACK_REG_P (recog_data.operand[i])
  	&& reg_class_subset_p (recog_op_alt[i][alt].class,
  			       FLOAT_REGS)
  	&& recog_op_alt[i][alt].class != FLOAT_REGS)
        {
  	/* If an operand needs to be in a particular reg in
  	   FLOAT_REGS, the constraint was either 't' or 'u'.  Since
  	   these constraints are for single register classes, and
  	   reload guaranteed that operand[i] is already in that class,
  	   we can just use REGNO (recog_data.operand[i]) to know which
  	   actual reg this operand needs to be in.  */
  
  	int regno = get_hard_regnum (&temp_stack, recog_data.operand[i]);
  
  	if (regno < 0)
  	  abort ();
  
  	if ((unsigned int) regno != REGNO (recog_data.operand[i]))
  	  {
  	    /* recog_data.operand[i] is not in the right place.  Find
  	       it and swap it with whatever is already in I's place.
  	       K is where recog_data.operand[i] is now.  J is where it
  	       should be.  */
  	    int j, k, temp;
  
  	    k = temp_stack.top - (regno - FIRST_STACK_REG);
  	    j = (temp_stack.top
  		 - (REGNO (recog_data.operand[i]) - FIRST_STACK_REG));
  
  	    temp = temp_stack.reg[k];
  	    temp_stack.reg[k] = temp_stack.reg[j];
  	    temp_stack.reg[j] = temp;
  	  }
        }
  
    /* Emit insns before INSN to make sure the reg-stack is in the right
       order.  */
  
    change_stack (insn, regstack, &temp_stack, EMIT_BEFORE);
  
    /* Make the needed input register substitutions.  Do death notes and
       clobbers too, because these are for inputs, not outputs.  */
  
    for (i = n_outputs; i < n_outputs + n_inputs; i++)
      if (STACK_REG_P (recog_data.operand[i]))
        {
  	int regnum = get_hard_regnum (regstack, recog_data.operand[i]);
  
  	if (regnum < 0)
  	  abort ();
  
  	replace_reg (recog_data.operand_loc[i], regnum);
        }
  
    for (i = 0; i < n_notes; i++)
      if (note_kind[i] == REG_DEAD)
        {
  	int regnum = get_hard_regnum (regstack, note_reg[i]);
  
  	if (regnum < 0)
  	  abort ();
  
  	replace_reg (note_loc[i], regnum);
        }
  
    for (i = 0; i < n_clobbers; i++)
      {
        /* It's OK for a CLOBBER to reference a reg that is not live.
           Don't try to replace it in that case.  */
        int regnum = get_hard_regnum (regstack, clobber_reg[i]);
  
        if (regnum >= 0)
  	{
  	  /* Sigh - clobbers always have QImode.  But replace_reg knows
  	     that these regs can't be MODE_INT and will abort.  Just put
  	     the right reg there without calling replace_reg.  */
  
  	  *clobber_loc[i] = FP_MODE_REG (regnum, DFmode);
  	}
      }
  
    /* Now remove from REGSTACK any inputs that the asm implicitly popped.  */
  
    for (i = n_outputs; i < n_outputs + n_inputs; i++)
      if (STACK_REG_P (recog_data.operand[i]))
        {
  	/* An input reg is implicitly popped if it is tied to an
  	   output, or if there is a CLOBBER for it.  */
  	int j;
  
  	for (j = 0; j < n_clobbers; j++)
  	  if (operands_match_p (clobber_reg[j], recog_data.operand[i]))
  	    break;
  
  	if (j < n_clobbers || recog_op_alt[i][alt].matches >= 0)
  	  {
  	    /* recog_data.operand[i] might not be at the top of stack.
  	       But that's OK, because all we need to do is pop the
  	       right number of regs off of the top of the reg-stack.
  	       record_asm_stack_regs guaranteed that all implicitly
  	       popped regs were grouped at the top of the reg-stack.  */
  
  	    CLEAR_HARD_REG_BIT (regstack->reg_set,
  				regstack->reg[regstack->top]);
  	    regstack->top--;
  	  }
        }
  
    /* Now add to REGSTACK any outputs that the asm implicitly pushed.
       Note that there isn't any need to substitute register numbers.
       ???  Explain why this is true.  */
  
    for (i = LAST_STACK_REG; i >= FIRST_STACK_REG; i--)
      {
        /* See if there is an output for this hard reg.  */
        int j;
  
        for (j = 0; j < n_outputs; j++)
  	if (STACK_REG_P (recog_data.operand[j])
  	    && REGNO (recog_data.operand[j]) == (unsigned) i)
  	  {
  	    regstack->reg[++regstack->top] = i;
  	    SET_HARD_REG_BIT (regstack->reg_set, i);
  	    break;
  	  }
      }
  
    /* Now emit a pop insn for any REG_UNUSED output, or any REG_DEAD
       input that the asm didn't implicitly pop.  If the asm didn't
       implicitly pop an input reg, that reg will still be live.
  
       Note that we can't use find_regno_note here: the register numbers
       in the death notes have already been substituted.  */
  
    for (i = 0; i < n_outputs; i++)
      if (STACK_REG_P (recog_data.operand[i]))
        {
  	int j;
  
  	for (j = 0; j < n_notes; j++)
  	  if (REGNO (recog_data.operand[i]) == REGNO (note_reg[j])
  	      && note_kind[j] == REG_UNUSED)
  	    {
  	      insn = emit_pop_insn (insn, regstack, recog_data.operand[i],
  				    EMIT_AFTER);
  	      break;
  	    }
        }
  
    for (i = n_outputs; i < n_outputs + n_inputs; i++)
      if (STACK_REG_P (recog_data.operand[i]))
        {
  	int j;
  
  	for (j = 0; j < n_notes; j++)
  	  if (REGNO (recog_data.operand[i]) == REGNO (note_reg[j])
  	      && note_kind[j] == REG_DEAD
  	      && TEST_HARD_REG_BIT (regstack->reg_set,
  				    REGNO (recog_data.operand[i])))
  	    {
  	      insn = emit_pop_insn (insn, regstack, recog_data.operand[i],
  				    EMIT_AFTER);
  	      break;
  	    }
        }
  }
  
  /* Substitute stack hard reg numbers for stack virtual registers in
     INSN.  Non-stack register numbers are not changed.  REGSTACK is the
     current stack content.  Insns may be emitted as needed to arrange the
     stack for the 387 based on the contents of the insn.  Return whether
     a control flow insn was deleted in the process.  */
  
  static bool
  subst_stack_regs (rtx insn, stack regstack)
  {
    rtx *note_link, note;
    bool control_flow_insn_deleted = false;
    int i;
  
    if (GET_CODE (insn) == CALL_INSN)
      {
        int top = regstack->top;
  
        /* If there are any floating point parameters to be passed in
  	 registers for this call, make sure they are in the right
  	 order.  */
  
        if (top >= 0)
  	{
  	  straighten_stack (PREV_INSN (insn), regstack);
  
  	  /* Now mark the arguments as dead after the call.  */
  
  	  while (regstack->top >= 0)
  	    {
  	      CLEAR_HARD_REG_BIT (regstack->reg_set, FIRST_STACK_REG + regstack->top);
  	      regstack->top--;
  	    }
  	}
      }
  
    /* Do the actual substitution if any stack regs are mentioned.
       Since we only record whether entire insn mentions stack regs, and
       subst_stack_regs_pat only works for patterns that contain stack regs,
       we must check each pattern in a parallel here.  A call_value_pop could
       fail otherwise.  */
  
    if (stack_regs_mentioned (insn))
      {
        int n_operands = asm_noperands (PATTERN (insn));
        if (n_operands >= 0)
  	{
  	  /* This insn is an `asm' with operands.  Decode the operands,
  	     decide how many are inputs, and do register substitution.
  	     Any REG_UNUSED notes will be handled by subst_asm_stack_regs.  */
  
  	  subst_asm_stack_regs (insn, regstack);
  	  return control_flow_insn_deleted;
  	}
  
        if (GET_CODE (PATTERN (insn)) == PARALLEL)
  	for (i = 0; i < XVECLEN (PATTERN (insn), 0); i++)
  	  {
  	    if (stack_regs_mentioned_p (XVECEXP (PATTERN (insn), 0, i)))
  	      control_flow_insn_deleted
  		|= subst_stack_regs_pat (insn, regstack,
  					 XVECEXP (PATTERN (insn), 0, i));
  	  }
        else
  	control_flow_insn_deleted
  	  |= subst_stack_regs_pat (insn, regstack, PATTERN (insn));
      }
  
    /* subst_stack_regs_pat may have deleted a no-op insn.  If so, any
       REG_UNUSED will already have been dealt with, so just return.  */
  
    if (GET_CODE (insn) == NOTE || INSN_DELETED_P (insn))
      return control_flow_insn_deleted;
  
    /* If there is a REG_UNUSED note on a stack register on this insn,
       the indicated reg must be popped.  The REG_UNUSED note is removed,
       since the form of the newly emitted pop insn references the reg,
       making it no longer `unset'.  */
  
    note_link = &REG_NOTES (insn);
    for (note = *note_link; note; note = XEXP (note, 1))
      if (REG_NOTE_KIND (note) == REG_UNUSED && STACK_REG_P (XEXP (note, 0)))
        {
  	*note_link = XEXP (note, 1);
  	insn = emit_pop_insn (insn, regstack, XEXP (note, 0), EMIT_AFTER);
        }
      else
        note_link = &XEXP (note, 1);
  
    return control_flow_insn_deleted;
  }
  
  /* Change the organization of the stack so that it fits a new basic
     block.  Some registers might have to be popped, but there can never be
     a register live in the new block that is not now live.
  
     Insert any needed insns before or after INSN, as indicated by
     WHERE.  OLD is the original stack layout, and NEW is the desired
     form.  OLD is updated to reflect the code emitted, ie, it will be
     the same as NEW upon return.
  
     This function will not preserve block_end[].  But that information
     is no longer needed once this has executed.  */
  
  static void
  change_stack (rtx insn, stack old, stack new, enum emit_where where)
  {
    int reg;
    int update_end = 0;
  
    /* We will be inserting new insns "backwards".  If we are to insert
       after INSN, find the next insn, and insert before it.  */
  
    if (where == EMIT_AFTER)
      {
        if (current_block && BB_END (current_block) == insn)
  	update_end = 1;
        insn = NEXT_INSN (insn);
      }
  
    /* Pop any registers that are not needed in the new block.  */
  
    for (reg = old->top; reg >= 0; reg--)
      if (! TEST_HARD_REG_BIT (new->reg_set, old->reg[reg]))
        emit_pop_insn (insn, old, FP_MODE_REG (old->reg[reg], DFmode),
  		     EMIT_BEFORE);
  
    if (new->top == -2)
      {
        /* If the new block has never been processed, then it can inherit
  	 the old stack order.  */
  
        new->top = old->top;
        memcpy (new->reg, old->reg, sizeof (new->reg));
      }
    else
      {
        /* This block has been entered before, and we must match the
  	 previously selected stack order.  */
  
        /* By now, the only difference should be the order of the stack,
  	 not their depth or liveliness.  */
  
        GO_IF_HARD_REG_EQUAL (old->reg_set, new->reg_set, win);
        abort ();
      win:
        if (old->top != new->top)
  	abort ();
  
        /* If the stack is not empty (new->top != -1), loop here emitting
  	 swaps until the stack is correct.
  
  	 The worst case number of swaps emitted is N + 2, where N is the
  	 depth of the stack.  In some cases, the reg at the top of
  	 stack may be correct, but swapped anyway in order to fix
  	 other regs.  But since we never swap any other reg away from
  	 its correct slot, this algorithm will converge.  */
  
        if (new->top != -1)
  	do
  	  {
  	    /* Swap the reg at top of stack into the position it is
  	       supposed to be in, until the correct top of stack appears.  */
  
  	    while (old->reg[old->top] != new->reg[new->top])
  	      {
  		for (reg = new->top; reg >= 0; reg--)
  		  if (new->reg[reg] == old->reg[old->top])
  		    break;
  
  		if (reg == -1)
  		  abort ();
  
  		emit_swap_insn (insn, old,
  				FP_MODE_REG (old->reg[reg], DFmode));
  	      }
  
  	    /* See if any regs remain incorrect.  If so, bring an
  	     incorrect reg to the top of stack, and let the while loop
  	     above fix it.  */
  
  	    for (reg = new->top; reg >= 0; reg--)
  	      if (new->reg[reg] != old->reg[reg])
  		{
  		  emit_swap_insn (insn, old,
  				  FP_MODE_REG (old->reg[reg], DFmode));
  		  break;
  		}
  	  } while (reg >= 0);
  
        /* At this point there must be no differences.  */
  
        for (reg = old->top; reg >= 0; reg--)
  	if (old->reg[reg] != new->reg[reg])
  	  abort ();
      }
  
    if (update_end)
      BB_END (current_block) = PREV_INSN (insn);
  }
  
  /* Print stack configuration.  */
  
  static void
  print_stack (FILE *file, stack s)
  {
    if (! file)
      return;
  
    if (s->top == -2)
      fprintf (file, "uninitialized\n");
    else if (s->top == -1)
      fprintf (file, "empty\n");
    else
      {
        int i;
        fputs ("[ ", file);
        for (i = 0; i <= s->top; ++i)
  	fprintf (file, "%d ", s->reg[i]);
        fputs ("]\n", file);
      }
  }
  
  /* This function was doing life analysis.  We now let the regular live
     code do it's job, so we only need to check some extra invariants
     that reg-stack expects.  Primary among these being that all registers
     are initialized before use.
  
     The function returns true when code was emitted to CFG edges and
     commit_edge_insertions needs to be called.  */
  
  static int
  convert_regs_entry (void)
  {
    int inserted = 0;
    edge e;
    basic_block block;
  
    FOR_EACH_BB_REVERSE (block)
      {
        block_info bi = BLOCK_INFO (block);
        int reg;
  
        /* Set current register status at last instruction `uninitialized'.  */
        bi->stack_in.top = -2;
  
        /* Copy live_at_end and live_at_start into temporaries.  */
        for (reg = FIRST_STACK_REG; reg <= LAST_STACK_REG; reg++)
  	{
  	  if (REGNO_REG_SET_P (block->global_live_at_end, reg))
  	    SET_HARD_REG_BIT (bi->out_reg_set, reg);
  	  if (REGNO_REG_SET_P (block->global_live_at_start, reg))
  	    SET_HARD_REG_BIT (bi->stack_in.reg_set, reg);
  	}
      }
  
    /* Load something into each stack register live at function entry.
       Such live registers can be caused by uninitialized variables or
       functions not returning values on all paths.  In order to keep
       the push/pop code happy, and to not scrog the register stack, we
       must put something in these registers.  Use a QNaN.
  
       Note that we are inserting converted code here.  This code is
       never seen by the convert_regs pass.  */
  
    for (e = ENTRY_BLOCK_PTR->succ; e ; e = e->succ_next)
      {
        basic_block block = e->dest;
        block_info bi = BLOCK_INFO (block);
        int reg, top = -1;
  
        for (reg = LAST_STACK_REG; reg >= FIRST_STACK_REG; --reg)
  	if (TEST_HARD_REG_BIT (bi->stack_in.reg_set, reg))
  	  {
  	    rtx init;
  
  	    bi->stack_in.reg[++top] = reg;
  
  	    init = gen_rtx_SET (VOIDmode,
  				FP_MODE_REG (FIRST_STACK_REG, SFmode),
  				nan);
  	    insert_insn_on_edge (init, e);
  	    inserted = 1;
  	  }
  
        bi->stack_in.top = top;
      }
  
    return inserted;
  }
  
  /* Construct the desired stack for function exit.  This will either
     be `empty', or the function return value at top-of-stack.  */
  
  static void
  convert_regs_exit (void)
  {
    int value_reg_low, value_reg_high;
    stack output_stack;
    rtx retvalue;
  
    retvalue = stack_result (current_function_decl);
    value_reg_low = value_reg_high = -1;
    if (retvalue)
      {
        value_reg_low = REGNO (retvalue);
        value_reg_high = value_reg_low
  	+ HARD_REGNO_NREGS (value_reg_low, GET_MODE (retvalue)) - 1;
      }
  
    output_stack = &BLOCK_INFO (EXIT_BLOCK_PTR)->stack_in;
    if (value_reg_low == -1)
      output_stack->top = -1;
    else
      {
        int reg;
  
        output_stack->top = value_reg_high - value_reg_low;
        for (reg = value_reg_low; reg <= value_reg_high; ++reg)
  	{
  	  output_stack->reg[value_reg_high - reg] = reg;
  	  SET_HARD_REG_BIT (output_stack->reg_set, reg);
  	}
      }
  }
  
  /* Adjust the stack of this block on exit to match the stack of the
     target block, or copy stack info into the stack of the successor
     of the successor hasn't been processed yet.  */
  static bool
  compensate_edge (edge e, FILE *file)
  {
    basic_block block = e->src, target = e->dest;
    block_info bi = BLOCK_INFO (block);
    struct stack_def regstack, tmpstack;
    stack target_stack = &BLOCK_INFO (target)->stack_in;
    int reg;
  
    current_block = block;
    regstack = bi->stack_out;
    if (file)
      fprintf (file, "Edge %d->%d: ", block->index, target->index);
  
    if (target_stack->top == -2)
      {
        /* The target block hasn't had a stack order selected.
           We need merely ensure that no pops are needed.  */
        for (reg = regstack.top; reg >= 0; --reg)
  	if (!TEST_HARD_REG_BIT (target_stack->reg_set, regstack.reg[reg]))
  	  break;
  
        if (reg == -1)
  	{
  	  if (file)
  	    fprintf (file, "new block; copying stack position\n");
  
  	  /* change_stack kills values in regstack.  */
  	  tmpstack = regstack;
  
  	  change_stack (BB_END (block), &tmpstack, target_stack, EMIT_AFTER);
  	  return false;
  	}
  
        if (file)
  	fprintf (file, "new block; pops needed\n");
      }
    else
      {
        if (target_stack->top == regstack.top)
  	{
  	  for (reg = target_stack->top; reg >= 0; --reg)
  	    if (target_stack->reg[reg] != regstack.reg[reg])
  	      break;
  
  	  if (reg == -1)
  	    {
  	      if (file)
  		fprintf (file, "no changes needed\n");
  	      return false;
  	    }
  	}
  
        if (file)
  	{
  	  fprintf (file, "correcting stack to ");
  	  print_stack (file, target_stack);
  	}
      }
  
    /* Care for non-call EH edges specially.  The normal return path have
       values in registers.  These will be popped en masse by the unwind
       library.  */
    if ((e->flags & (EDGE_EH | EDGE_ABNORMAL_CALL)) == EDGE_EH)
      target_stack->top = -1;
  
    /* Other calls may appear to have values live in st(0), but the
       abnormal return path will not have actually loaded the values.  */
    else if (e->flags & EDGE_ABNORMAL_CALL)
      {
        /* Assert that the lifetimes are as we expect -- one value
           live at st(0) on the end of the source block, and no
           values live at the beginning of the destination block.  */
        HARD_REG_SET tmp;
  
        CLEAR_HARD_REG_SET (tmp);
        GO_IF_HARD_REG_EQUAL (target_stack->reg_set, tmp, eh1);
        abort ();
      eh1:
  
        /* We are sure that there is st(0) live, otherwise we won't compensate.
  	 For complex return values, we may have st(1) live as well.  */
        SET_HARD_REG_BIT (tmp, FIRST_STACK_REG);
        if (TEST_HARD_REG_BIT (regstack.reg_set, FIRST_STACK_REG + 1))
          SET_HARD_REG_BIT (tmp, FIRST_STACK_REG + 1);
        GO_IF_HARD_REG_EQUAL (regstack.reg_set, tmp, eh2);
        abort ();
      eh2:
  
        target_stack->top = -1;
      }
  
    /* It is better to output directly to the end of the block
       instead of to the edge, because emit_swap can do minimal
       insn scheduling.  We can do this when there is only one
       edge out, and it is not abnormal.  */
    else if (block->succ->succ_next == NULL && !(e->flags & EDGE_ABNORMAL))
      {
        /* change_stack kills values in regstack.  */
        tmpstack = regstack;
  
        change_stack (BB_END (block), &tmpstack, target_stack,
  		    (GET_CODE (BB_END (block)) == JUMP_INSN
  		     ? EMIT_BEFORE : EMIT_AFTER));
      }
    else
      {
        rtx seq, after;
  
        /* We don't support abnormal edges.  Global takes care to
           avoid any live register across them, so we should never
           have to insert instructions on such edges.  */
        if (e->flags & EDGE_ABNORMAL)
  	abort ();
  
        current_block = NULL;
        start_sequence ();
  
        /* ??? change_stack needs some point to emit insns after.  */
        after = emit_note (NOTE_INSN_DELETED);
  
        tmpstack = regstack;
        change_stack (after, &tmpstack, target_stack, EMIT_BEFORE);
  
        seq = get_insns ();
        end_sequence ();
  
        insert_insn_on_edge (seq, e);
        return true;
      }
    return false;
  }
  
  /* Convert stack register references in one block.  */
  
  static int
  convert_regs_1 (FILE *file, basic_block block)
  {
    struct stack_def regstack;
    block_info bi = BLOCK_INFO (block);
    int deleted, inserted, reg;
    rtx insn, next;
    edge e, beste = NULL;
    bool control_flow_insn_deleted = false;
  
    inserted = 0;
    deleted = 0;
    any_malformed_asm = false;
  
    /* Find the edge we will copy stack from.  It should be the most frequent
       one as it will get cheapest after compensation code is generated,
       if multiple such exists, take one with largest count, prefer critical
       one (as splitting critical edges is more expensive), or one with lowest
       index, to avoid random changes with different orders of the edges.  */
    for (e = block->pred; e ; e = e->pred_next)
      {
        if (e->flags & EDGE_DFS_BACK)
  	;
        else if (! beste)
  	beste = e;
        else if (EDGE_FREQUENCY (beste) < EDGE_FREQUENCY (e))
  	beste = e;
        else if (EDGE_FREQUENCY (beste) > EDGE_FREQUENCY (e))
  	;
        else if (beste->count < e->count)
  	beste = e;
        else if (beste->count > e->count)
  	;
        else if ((EDGE_CRITICAL_P (e) != 0)
  	       != (EDGE_CRITICAL_P (beste) != 0))
  	{
  	  if (EDGE_CRITICAL_P (e))
  	    beste = e;
  	}
        else if (e->src->index < beste->src->index)
  	beste = e;
      }
  
    /* Initialize stack at block entry.  */
    if (bi->stack_in.top == -2)
      {
        if (beste)
  	inserted |= compensate_edge (beste, file);
        else
  	{
  	  /* No predecessors.  Create an arbitrary input stack.  */
  	  int reg;
  
  	  bi->stack_in.top = -1;
  	  for (reg = LAST_STACK_REG; reg >= FIRST_STACK_REG; --reg)
  	    if (TEST_HARD_REG_BIT (bi->stack_in.reg_set, reg))
  	      bi->stack_in.reg[++bi->stack_in.top] = reg;
  	}
      }
    else
      /* Entry blocks do have stack already initialized.  */
      beste = NULL;
  
    current_block = block;
  
    if (file)
      {
        fprintf (file, "\nBasic block %d\nInput stack: ", block->index);
        print_stack (file, &bi->stack_in);
      }
  
    /* Process all insns in this block.  Keep track of NEXT so that we
       don't process insns emitted while substituting in INSN.  */
    next = BB_HEAD (block);
    regstack = bi->stack_in;
    do
      {
        insn = next;
        next = NEXT_INSN (insn);
  
        /* Ensure we have not missed a block boundary.  */
        if (next == NULL)
  	abort ();
        if (insn == BB_END (block))
  	next = NULL;
  
        /* Don't bother processing unless there is a stack reg
  	 mentioned or if it's a CALL_INSN.  */
        if (stack_regs_mentioned (insn)
  	  || GET_CODE (insn) == CALL_INSN)
  	{
  	  if (file)
  	    {
  	      fprintf (file, "  insn %d input stack: ",
  		       INSN_UID (insn));
  	      print_stack (file, &regstack);
  	    }
  	  control_flow_insn_deleted |= subst_stack_regs (insn, &regstack);
  	}
      }
    while (next);
  
    if (file)
      {
        fprintf (file, "Expected live registers [");
        for (reg = FIRST_STACK_REG; reg <= LAST_STACK_REG; ++reg)
  	if (TEST_HARD_REG_BIT (bi->out_reg_set, reg))
  	  fprintf (file, " %d", reg);
        fprintf (file, " ]\nOutput stack: ");
        print_stack (file, &regstack);
      }
  
    insn = BB_END (block);
    if (GET_CODE (insn) == JUMP_INSN)
      insn = PREV_INSN (insn);
  
    /* If the function is declared to return a value, but it returns one
       in only some cases, some registers might come live here.  Emit
       necessary moves for them.  */
  
    for (reg = FIRST_STACK_REG; reg <= LAST_STACK_REG; ++reg)
      {
        if (TEST_HARD_REG_BIT (bi->out_reg_set, reg)
  	  && ! TEST_HARD_REG_BIT (regstack.reg_set, reg))
  	{
  	  rtx set;
  
  	  if (file)
  	    {
  	      fprintf (file, "Emitting insn initializing reg %d\n",
  		       reg);
  	    }
  
  	  set = gen_rtx_SET (VOIDmode, FP_MODE_REG (reg, SFmode),
  			     nan);
  	  insn = emit_insn_after (set, insn);
  	  control_flow_insn_deleted |= subst_stack_regs (insn, &regstack);
  	}
      }
    
    /* Amongst the insns possibly deleted during the substitution process above,
       might have been the only trapping insn in the block.  We purge the now
       possibly dead EH edges here to avoid an ICE from fixup_abnormal_edges,
       called at the end of convert_regs.  The order in which we process the
       blocks ensures that we never delete an already processed edge.
  
       Note that, at this point, the CFG may have been damaged by the emission
       of instructions after an abnormal call, which moves the basic block end
       (and is the reason why we call fixup_abnormal_edges later).  So we must
       be sure that the trapping insn has been deleted before trying to purge
       dead edges, otherwise we risk purging valid edges.
  
       ??? We are normally supposed not to delete trapping insns, so we pretend
       that the insns deleted above don't actually trap.  It would have been
       better to detect this earlier and avoid creating the EH edge in the first
       place, still, but we don't have enough information at that time.  */
  
    if (control_flow_insn_deleted)
      purge_dead_edges (block);
  
    /* Something failed if the stack lives don't match.  If we had malformed
       asms, we zapped the instruction itself, but that didn't produce the
       same pattern of register kills as before.  */
    GO_IF_HARD_REG_EQUAL (regstack.reg_set, bi->out_reg_set, win);
    if (!any_malformed_asm)
      abort ();
   win:
    bi->stack_out = regstack;
  
    /* Compensate the back edges, as those wasn't visited yet.  */
    for (e = block->succ; e ; e = e->succ_next)
      {
        if (e->flags & EDGE_DFS_BACK
  	  || (e->dest == EXIT_BLOCK_PTR))
  	{
  	  if (!BLOCK_INFO (e->dest)->done
  	      && e->dest != block)
  	    abort ();
  	  inserted |= compensate_edge (e, file);
  	}
      }
    for (e = block->pred; e ; e = e->pred_next)
      {
        if (e != beste && !(e->flags & EDGE_DFS_BACK)
  	  && e->src != ENTRY_BLOCK_PTR)
  	{
  	  if (!BLOCK_INFO (e->src)->done)
  	    abort ();
  	  inserted |= compensate_edge (e, file);
  	}
      }
  
    return inserted;
  }
  
  /* Convert registers in all blocks reachable from BLOCK.  */
  
  static int
  convert_regs_2 (FILE *file, basic_block block)
  {
    basic_block *stack, *sp;
    int inserted;
  
    /* We process the blocks in a top-down manner, in a way such that one block
       is only processed after all its predecessors.  The number of predecessors
       of every block has already been computed.  */ 
  
    stack = xmalloc (sizeof (*stack) * n_basic_blocks);
    sp = stack;
  
    *sp++ = block;
  
    inserted = 0;
    do
      {
        edge e;
  
        block = *--sp;
  
        /* Processing BLOCK is achieved by convert_regs_1, which may purge
  	 some dead EH outgoing edge after the deletion of the trapping
  	 insn inside the block.  Since the number of predecessors of
  	 BLOCK's successors was computed based on the initial edge set,
  	 we check the necessity to process some of these successors
  	 before such an edge deletion may happen.  However, there is
  	 a pitfall: if BLOCK is the only predecessor of a successor and
  	 the edge between them happens to be deleted, the successor
  	 becomes unreachable and should not be processed.  The problem
  	 is that there is no way to preventively detect this case so we
  	 stack the successor in all cases and hand over the task of
  	 fixing up the discrepancy to convert_regs_1.  */
  
        for (e = block->succ; e ; e = e->succ_next)
  	if (! (e->flags & EDGE_DFS_BACK))
  	  {
  	    BLOCK_INFO (e->dest)->predecessors--;
  	    if (!BLOCK_INFO (e->dest)->predecessors)
  	       *sp++ = e->dest;
  	  }
  
        inserted |= convert_regs_1 (file, block);
        BLOCK_INFO (block)->done = 1;
      }
    while (sp != stack);
  
    return inserted;
  }
  
  /* Traverse all basic blocks in a function, converting the register
     references in each insn from the "flat" register file that gcc uses,
     to the stack-like registers the 387 uses.  */
  
  static int
  convert_regs (FILE *file)
  {
    int inserted;
    basic_block b;
    edge e;
  
    /* Initialize uninitialized registers on function entry.  */
    inserted = convert_regs_entry ();
  
    /* Construct the desired stack for function exit.  */
    convert_regs_exit ();
    BLOCK_INFO (EXIT_BLOCK_PTR)->done = 1;
  
    /* ??? Future: process inner loops first, and give them arbitrary
       initial stacks which emit_swap_insn can modify.  This ought to
       prevent double fxch that aften appears at the head of a loop.  */
  
    /* Process all blocks reachable from all entry points.  */
    for (e = ENTRY_BLOCK_PTR->succ; e ; e = e->succ_next)
      inserted |= convert_regs_2 (file, e->dest);
  
    /* ??? Process all unreachable blocks.  Though there's no excuse
       for keeping these even when not optimizing.  */
    FOR_EACH_BB (b)
      {
        block_info bi = BLOCK_INFO (b);
  
        if (! bi->done)
  	inserted |= convert_regs_2 (file, b);
      }
    clear_aux_for_blocks ();
  
    fixup_abnormal_edges ();
    if (inserted)
      commit_edge_insertions ();
  
    if (file)
      fputc ('\n', file);
  
    return inserted;
  }
  #endif /* STACK_REGS */
  
  #include "gt-reg-stack.h"
  