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/*

    Copyright (c) 1993 Open Software Foundation, Inc.

    All Rights Reserved

    Permission to use, copy, modify, and distribute this software

    and its documentation for any purpose and without fee is hereby

    granted, provided that the above copyright notice appears in all

    copies and that both the copyright notice and this permission

    notice appear in supporting documentation.

    OSF DISCLAIMS ALL WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING

    ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A

    PARTICULAR PURPOSE.

    IN NO EVENT SHALL OSF BE LIABLE FOR ANY SPECIAL, INDIRECT, OR

    CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM

    LOSS OF USE, DATA OR PROFITS, WHETHER IN ACTION OF CONTRACT,

    NEGLIGENCE, OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION

    WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.

*/

/*

    		 Crown Copyright (c) 1997

    This TenDRA(r) Computer Program is subject to Copyright

    owned by the United Kingdom Secretary of State for Defence

    acting through the Defence Evaluation and Research Agency

    (DERA).  It is made available to Recipients with a

    royalty-free licence for its use, reproduction, transfer

    to other parties and amendment for any purpose not excluding

    product development provided that any such use et cetera

    shall be deemed to be acceptance of the following conditions:-

        (1) Its Recipients shall ensure that this Notice is

        reproduced upon any copies or amended versions of it;

        (2) Any amended version of it shall be clearly marked to

        show both the nature of and the organisation responsible

        for the relevant amendment or amendments;

        (3) Its onward transfer from a recipient to another

        party shall be deemed to be that party's acceptance of

        these conditions;

        (4) DERA gives no warranty or assurance as to its

        quality or suitability for any purpose and DERA accepts

        no liability whatsoever in relation to any use to which

        it may be put.

*/

/**********************************************************************

$Author: release $

$Date: 1998/02/04 15:48:53 $

$Revision: 1.2 $

$Log: locate.c,v $

 * Revision 1.2  1998/02/04  15:48:53  release

 * Added OSF copyright message.

 *

 * Revision 1.1.1.1  1998/01/17  15:55:57  release

 * First version to be checked into rolling release.

 *

 * Revision 1.2  1996/10/04  16:01:52  pwe

 * add banners and mod for PWE ownership

 *

**********************************************************************/

/* locate.c

     discovers "where" an "exp" is;

     The where coding of an address tells one whether the result of

      evaluating an exp is in a register or directly or literally in store,

*/

#include "config.h"

#include "memtdf.h"

#include "codegen.h"

#include "geninst.h"

#include "proc.h"

#include "myassert.h"

#include "comment.h"

#include "stack.h"

#include "locate.h"

#include "frames.h"

/******************************************************************************

For non globals, boff encodes things in the following way.

The number of bytes gives a displacement from different positions on 

the stack depending on whether it is relative to R_SP R_FP or R_TP

The stack below gives the worst case of the stack i.e a general_proc with 

alloca

  |           |

  |           | #

  |           | |  x relative to R_TP i.e caller parameters

  |-----------| |                     in input caller parameter area

  | STACK     | |

  | LINK      | | STACK_ARG_AREA

  | AREA      | |

  |-----------|<--------R_TP

  | Input     |

  | Callees   |

  |           |

  |           |

  |           |

  |           |

  |-----------|<--------R_FP

  |           | |

  |           | |

  |           | |                          #

  |           | |                          | displacement x relative to R_FP

  |           | |                          | coded like this in regalloc

  |           | | p_frame_size          #

  |           | |                          |

  |           | |                          | p_locals_offset

  |           | |                          |

  |           | |                          |

  |           | # <--initial R_SP was here

  |-----------|

  |           | #

  |           | | x relative to R_SP i.e output caller parameter construction

  |-----------| |

  | STACK     | |

  | LINK      | | STACK_ARG_AREA

  | AREA      | |

  |-----------|<--------R_SP

******************************************************************************/

/* decodes e to give a baseoff suitable for xxx_ins functions */

baseoff boff PROTO_N ((e)) PROTO_T (exp e)

{

  baseoff an;

  if (isglob(e))

  {

    dec *gl = brog(e);

    long sno = gl->dec_u.dec_val.sym_number;

    /* an.base is negated global sym number, positive used for base reg number */

    an.base = -(sno + 1);

    an.offset = 0;

  }

  else

  {

    return boff_location(no(e));

  }

  return an;

}

baseoff boff_location PROTO_N ((n)) PROTO_T (int n)

{ 

  baseoff an;

  int br = n & 0x3f;		/* base reg in bottom 6 bits */

  long off = (n>>6);		/* offset in bytes from br in rest */

  ASSERT((n<0)==(off<0));	/* any sign propagated */

  if(br<0)

    br = -br;

  /* There are three possiblilities for br */

  /* i.e R_TP R_FP R_SP */

  /* R_TP|

     -----

     if something is relative to R_TP it is a caller of the previous proc

     since R_TP is the top of the frame

     R_FP|

     -----

     This is all locals to the current procedure

     R_SP|

     -----

     This is used for constructing argument lists for calling parameters

     It is possible that all three are the same

     i.e they are all calculated from the stack pointer.

     However in a general_proc

     things get nasty and all three will point to different places

     */

  if (br == R_SP)

  {

    an.base = R_SP;

    an.offset = off;

    ASSERT(off >= 0);

  }

  else if(br == R_FP)

  {

    if(p_has_fp)

    {

      an.base = R_FP;

      an.offset = p_locals_offset + off - p_frame_size;

    }

    else

    {

      an.base = R_SP;

      an.offset = p_locals_offset + off;

    }

  }

  else if(br == R_TP)

  {

    if (p_has_tp)

    {

      an.base = R_TP;

      an.offset = off;

    }

    else if(p_has_fp)

    {

      an.base = R_FP;

      an.offset = off;

    }

    else 

    {

      an.base = R_SP;

      an.offset = off + p_frame_size;

    }

  }

  else

  {

    fail("Error:boff_location: Unknown base");

  }

  return an;

}

int ENCODE_FOR_BOFF PROTO_N ((off,type)) PROTO_T (int off X int type)

{

  /* type is either */

  /* INPUT_CALLER_PARAMETER, INPUT_CALLEE_PARAMETER, OUTPUT_CALLER_PARAMETER */

  /* offset shoulb be in bytes */

  int encode_offset;

  int encode_base;

  switch(type)

  {

   case INPUT_CALLER_PARAMETER:

    {

      encode_base = R_TP;

      encode_offset = off + STACK_ARG_AREA;

      break;

    }

   case INPUT_CALLEE_PARAMETER:

    {

      encode_base = R_FP;

      encode_offset = p_frame_size - p_locals_offset + EXTRA_CALLEE_BYTES + off;

      break;

    }

   case OUTPUT_CALLER_PARAMETER:

    {

      encode_base = R_SP;

      encode_offset = STACK_ARG_AREA + off;

      break;

    }

   default:

    fail("Unknown encodeing for ENCODE_FOR_BOFF");

  }

  return (encode_offset<<6) + encode_base;

}

/* mutual recursion between locate1() and locate() */

where locate PROTO_S ((exp, space, shape, int));

 /*

  * finds the address of e using shape s; sp gives available t-regs for any

  * inner evaluation. dreg is historical.

  */

static where locate1 PROTO_N ((e,sp,s,dreg)) PROTO_T (exp e X space sp X shape s X int dreg)

{

  ash a;

  ans aa;

  where wans;

  FULLCOMMENT3("locate1: name(e)=%d, name(s)=%d, dreg=%d", name(e), name(s), dreg);

  a = ashof(s);

  switch (name(e))

  {

    /***********************************************/

   case name_tag:

    { 

      /* NAME_TAG */

      exp dc = son(e);

      bool var = isvar(dc);

      FULLCOMMENT2("locate1 name_tag: name(dc)=%d, var=%d", name(dc), var);

      if (props(dc) & defer_bit)

      {

	/*

	 * ... it has been identified with a simple expression which is

	 * better evaluated every time

	 */

	where w;

	w = locate(son(dc), sp, sh(son(dc)), dreg);

	if (no(e) == 0)

	{

	  aa = w.answhere;

	}

	else

	{

	  instore is;

	  switch (w.answhere.discrim)

	  {

	   case notinreg:

	    {

	      is = insalt(w.answhere);

	      is.b.offset += (no(e) / 8);

	      break;

	    }

	   default:

	    fail("name not deferable");

	  }

	  setinsalt(aa, is);

	}

      }

      else if (props(dc) & inreg_bits)

      {

	/* ... it has been allocated in a fixed point reg */

	if (var)

	{

	  setregalt(aa, no(dc));

	}

	else

	{

	  instore b;

	  b.b.base = no(dc);

	  b.b.offset = 0;

	  b.adval = 1;

	  setinsalt(aa, b);

	}

      }

      else if (props(dc) & infreg_bits)

      {

	/* ... it has been allocated in a floating point reg */

	freg fr;

	fr.fr = no(dc);

	fr.dble = (a.ashsize == 64) ? 1 : 0;

	setfregalt(aa, fr);

      }

      else

      {

	/* ... it is in memory */

	instore is;

	if (var|| (name(sh(e)) == prokhd &&

		      (son(dc) == nilexp || IS_A_PROC(son(dc)))))

	{

	  is.adval = 1;

	  /* If it is a var tag you can get address of it */

	}

	else

	{

	  is.adval = 0;

	}

	is.b = boff(dc);

	is.b.offset += (no(e) / 8);

#if 1

	if (var && name(sh(e)) != prokhd && !IS_FIXREG(is.b.base) && is.b.offset == 0)

	{

	  /*

	   * A global which has to be accessed via TOC.

	   * We load it explicitly into reg here so we can

	   * use the reg contents tracking mechanism for

	   * addresses found in the TOC.

	   * If we did not do this, we would still generate correct code,

	   * but needlessly reload from TOC.

	   * +++ offset != 0 -> keepglob for 0 offset & keepreg for offset

	   */

	  if (dreg == 0)

	    dreg = getreg(sp.fixed);

	  set_ins(is.b, dreg);

	  keepreg(e, dreg);

	  FULLCOMMENT3("locate1 name_tag: keepreg glob adval=%d bo={%d,%d}", is.adval, is.b.base, is.b.offset);

	  is.b.base = dreg;

	  is.b.offset = 0;

	}

#endif

	setinsalt(aa, is);

      }

      wans.answhere = aa;

      wans.ashwhere = a;

      return wans;

    }

    /***********************************************/

  case addptr_tag:

    {

      exp sum = son(e);

      where wsum;

      int addend;

      space nsp;

      int reg;

      int ind = R_NO_REG;

      instore is;

      ans asum;

      wsum = locate(sum, sp, sh(sum), 0);

      asum = wsum.answhere;

      /*

       * answer is going to be wsum displaced by integer result of evaluating

       * bro(sum)

       */

      switch (asum.discrim)

      {

      case notinreg:

	{

	  is = insalt(asum);

	  if (is.adval)

	  {

	    /* wsum is a literal address in store ... */

	    baseoff b;

	    b = is.b;

	    if (!IS_FIXREG(b.base))

	    {

	      /* ... it is not a base-offset, so make it one */

	      reg = getreg(sp.fixed);

	      set_ins(b, reg);

	      keepreg(sum, reg);

	      b.base = reg;

	      b.offset = 0;

	    }

	    nsp = guardreg(b.base, sp);

	    addend = reg_operand(bro(sum), nsp);

	    /* evaluate the displacement ... */

	    if (dreg == 0)

	      dreg = getreg(nsp.fixed);

	    rrr_ins(i_a, b.base, addend, dreg);

	    /* ... add it to the base register into new reg */

	    b.base = dreg;

	    is.b = b;

	    setinsalt(aa, is);

	    wans.answhere = aa;

	    wans.ashwhere = a;

	    /* ...and use it as base a literal base-offset result */

	    keepexp(e, aa);

	    return wans;

	  }

	  else

	  {

	    /* wsum represents an actual pointer in store... */

	    /* ... so load it into a good register */

	    ind = getreg(sp.fixed);

	    ld_ins(i_l, is.b, ind);

	  }

	  break;

	}			/* end notinreg */

      case inreg:

	{

	  /* wsum is already in reg */

	  ind = regalt(asum);

	  break;

	}

      default:

	{

	  fail("locate ? reg");

	}

      }				/* end case */

      /* register ind contains the evaluation of 1st operand of addptr */

      nsp = guardreg(ind, sp);

      if (name(bro(sum)) == env_offset_tag || name(bro(sum))==general_env_offset_tag)

      {

	is.b.base = ind;

	is.b.offset = frame_offset(son(bro(sum)));

      }

      else

      {

	addend = reg_operand(bro(sum), nsp);

	/* evaluate displacement, add it to ind in new reg */

	if (dreg == 0)

	  dreg = getreg(nsp.fixed);

	rrr_ins(i_a, ind, addend, dreg);

	is.b.base = dreg;

	is.b.offset = 0;

      }

      is.adval = 1;

      setinsalt(aa, is);

      wans.answhere = aa;

      wans.ashwhere = a;

      /* ... and deliver literal base_offset */

      keepexp(e, aa);

      return wans;

    }				/* end add_ptr */

  case subptr_tag:		/* this is nugatory - previous transforms make

				 * it into addptr or reff */

    {

      exp sum = son(e);

      int ind = reg_operand(sum, sp);

      instore isa;

      isa.adval = 1;

      sum = bro(sum);

      if (name(sum) == val_tag)

      {

	instore isa;

	isa.b.base = ind;

	isa.b.offset = -no(e);

	setinsalt(aa, isa);

      }

      else

      {

	if (dreg == 0)

	  dreg = getreg(sp.fixed);

	rrr_ins(i_s, ind, reg_operand(sum, guardreg(ind, sp)), dreg);

	isa.b.base = dreg;

	isa.b.offset = 0;

      }

      setinsalt(aa, isa);

      wans.answhere = aa;

      wans.ashwhere = a;

      keepexp(e, aa);

      return wans;

    }				/* end subptr */

  case reff_tag:

    {

      instore isa;

      bool bitfield;

      /* answer is going to be wans displaced by no(e) */

      wans = locate(son(e), sp, sh(son(e)), 0);

      bitfield = ((name(sh(e)) == ptrhd) && (al1(sh(e)) == 1));

      switch (wans.answhere.discrim)

      {

      case notinreg:

	{

	  isa = insalt(wans.answhere);

	  if (!isa.adval)

	  {

	    /*

	     * wans is an actual pointer  in store, so make it into a literal

	     * address....

	     */

	    int reg = getreg(sp.fixed);

	    ld_ins(i_l, isa.b, reg);

	    isa.b.offset = 0;

	    isa.b.base = reg;

	    isa.adval = 1;

	  }

	  /*

	   * ... and add appropriate displacement to give result

	   */

	  isa.b.offset += no(e) / 8;

	  setinsalt(wans.answhere, isa);

	  keepexp(e, wans.answhere);

	  break;

	}

      case inreg:

	{

	  /* wans is a pointer in a register */

	  isa.b.base = regalt(wans.answhere);

	  isa.adval = 1;

	  isa.b.offset = no(e) / 8;

	  setinsalt(wans.answhere, isa);

	  break;

	}

      default:

	{

	  fail("locate ? reg ");

	}

      }

      wans.ashwhere = a;

      return wans;

    }				/* end reff */

   case cont_tag:

   case contvol_tag:

    {

      exp p = son(e);

      ans ason;

      instore isa;

      int reg;

      where fc;

      fc = locate(p, sp, sh(e) , 0);

      ason = fc.answhere;

      /*

       * answer is going to be the contents of address represented by fc

       */

      switch (ason.discrim)

      {

       case notinreg:

	{

	  isa = insalt(ason);

	  FULLCOMMENT3("locate1 cont_tag: adval=%d bo={%d,%d}", isa.adval, isa.b.base, isa.b.offset);

	  if (isa.adval)

	  {

	    /* literal store address, so make it into a direct one */

	    isa.adval = 0;

	    setinsalt(aa, isa);

	  }

	  else

	  {

	    /*

	     * actual pointer in store

	     * so load it into reg and deliver direct base-offset (reg,0)

	     */

	    reg = getreg(sp.fixed);

	    ld_ins(i_l, isa.b, reg);

	    isa.b.base = reg;

	    isa.b.offset = 0;

	    setinsalt(aa, isa);

	    if (name(e) != contvol_tag && fc.ashwhere.ashalign != 1)

	      keepexp(e, aa);

	  }

	  goto breakson;

	}			/* end notinrg */

      case inreg:

	/*

	 * this one is fraught

	 * - it depends on only being used in lh-value positions from vars

	 * - take care

	 */

	{

	  isa.b.base = regalt(ason);

	  isa.b.offset = 0;

	  isa.adval = 1;

	  setinsalt(aa, isa);

	  /* fc is in register, so deliver literal(!? ) base-offset */

	  goto breakson;

	}

      case infreg:		/* ditto caveat above */

	{

	  aa = ason;

	  goto breakson;

	}

      default:

	{

	  fail("locate ? reg");

	}

      }

  breakson:

      wans.answhere = aa;

      wans.ashwhere = a;

      return wans;

    }				/* end cont */

  case top_tag:		/* does this ever happen ? */

    {

      setregalt(aa, 0);

      wans.answhere = aa;

      wans.ashwhere = a;

      return wans;

    }				/* end top */

  case field_tag:

    {

      instore isa;

      wans = locate(son(e), sp, sh(son(e)), 0);

      /*

       * answer is wans displace literally by no(e);

       * it should always be a literal store address

       */

      switch (wans.answhere.discrim)

      {

      case notinreg:

	{

	  isa = insalt(wans.answhere);

	  isa.b.offset += no(e) / 8;

	  setinsalt(wans.answhere, isa);

	  FULLCOMMENT1("locate field_tag: adjusting byte offset to %d", isa.b.offset);

	  break;

	}

       default:

	fail("field should be transformed");

      }

      wans.ashwhere = a;

      return wans;

    }				/* end field */

  default:

    {

      /*

       * general catch all; 

       * evaluate e into register and deliver it as a literal

       * store address

       */

      int r = reg_operand(e, sp);

      instore is;

      if (r == R_RESULT)

      {

	/* guard possible result from proc - can do better +++ */

	FULLCOMMENT("guarding possible result");

	r = getreg(sp.fixed);

	if (r != R_RESULT)

	{

	  mov_rr_ins(R_RESULT, r);comment("move R_RESULT to reg");

	}

      }

      is.b.base = r;

      is.b.offset = 0;

      is.adval = 1;

      setinsalt(aa, is);

      wans.answhere = aa;

      wans.ashwhere = a;

      return wans;

    }

  }

}

 /*

  * locate differs from locate1 only in that it looks to see if e has already

  * been evaluated and remembered by register contents tracking scheme

  */

where locate PROTO_N ((e,sp,s,dreg)) PROTO_T (exp e X space sp X shape s X int dreg)

{

  ans ak;

  where w;

  /* Check to see if e has already been evaluated and remembered */

  if (!IS_R_NO_REG(dreg))

  {

    /* first try for exact reg */

    ak = iskept_inreg(e, dreg);

    if (ak.discrim == inreg && (regalt(ak) == 0))

      ak = iskept(e);			/* no luck, try anywhere */

  }

  else

  {

    ak = iskept(e);

  }

  if (ak.discrim == inreg && (regalt(ak) == 0))	/* See if we found a register */

  {

    w = locate1(e, sp, s, dreg);/* No register found so we must use locate1 */

  }

  else

  {

    FULLCOMMENT2("locate: iskept() found value inreg=%d [reg=%d]", ak.discrim == inreg, regalt(ak));

    w.answhere = ak;

    w.ashwhere = ashof(s);

  }

  return w;

}