⟦80e4ba53f⟧

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/*          Hey EMACS, this is -*- C -*- code!                 */

/****************************************************************
*                                                               *
*                         Copyright (c) 1984                    *
*               Massachusetts Institute of Technology           *
*                                                               *
* This material was developed by the Scheme project at the      *
* Massachusetts Institute of Technology, Department of          *
* Electrical Engineering and Computer Science.  Permission to   *
* copy this software, to redistribute it, and to use it for any *
* purpose is granted, subject to the following restrictions and *
* understandings.                                               *
*                                                               *
* 1. Any copy made of this software must include this copyright *
* notice in full.                                               *
*                                                               *
* 2. Users of this software agree to make their best efforts (a)*
* to return to the MIT Scheme project any improvements or       *
* extensions that they make, so that these may be included in   *
* future releases; and (b) to inform MIT of noteworthy uses of  *
* this software.                                                *
*                                                               *
* 3.  All materials developed as a consequence of the use of    *
* this software shall duly acknowledge such use, in accordance  *
* with the usual standards of acknowledging credit in academic  *
* research.                                                     *
*                                                               *
* 4. MIT has made no warrantee or representation that the       *
* operation of this software will be error-free, and MIT is     *
* under no obligation to provide any services, by way of        *
* maintenance, update, or otherwise.                            *
*                                                               *
* 5.  In conjunction with products arising from the use of this *
* material, there shall be no use of the name of the            *
* Massachusetts Institute of Technology nor of any adaptation   *
* thereof in any advertising, promotional, or sales literature  *
* without prior written consent from MIT in each case.          *
*                                                               *
****************************************************************/
\f


/* File: PURIFY.C
 *
 * This file contains the code for primitives dealing with pure
 * and constant space.
 */
#include "scheme.h"
#include "primitive.h"
#include "gccode.h"
#include "zones.h"

/* This is a copy of GCLoop, with GC_Mode handling added, and
   debugging printout removed.
*/

#define Setup_Pointer_for_Purify(Extra_Code)			\
Old = Get_Pointer(Temp);					\
if ((GC_Mode == CONSTANT_COPY) &&				\
    (Old > Low_Constant))					\
  continue;							\
Setup_Pointer(false, Extra_Code)

#define Indirect_BH(In_GC)					\
if (Type_Code(*Old) == TC_BROKEN_HEART) continue;	  

#define Transport_Indirect()					\
Real_Transport_Vector();					\
*Get_Pointer(Temp) = New_Address
\f


Pointer *PurifyLoop(Scan, To_Pointer, GC_Mode)
fast Pointer *Scan;
Pointer **To_Pointer;
int GC_Mode;
{ fast Pointer *To, *Old, Temp, *Low_Constant, New_Address;

  To = *To_Pointer;
  Low_Constant = Constant_Space;
  for ( ; Scan != To; Scan++)
  { Temp = *Scan;
    Switch_by_GC_Type(Temp)
    { case TC_BROKEN_HEART:
        if (Scan == (Get_Pointer(Temp)))
	{ *To_Pointer = To;
	  return Scan;
	}
        fprintf(stderr, "Purify: Broken heart in scan.\n");
	Microcode_Termination(TERM_BROKEN_HEART);

      case TC_MANIFEST_NM_VECTOR:
      case TC_MANIFEST_SPECIAL_NM_VECTOR:
	Scan += Get_Integer(Temp);
	break;

      case_Non_Pointer:
	break;

      case_Cell:
	Setup_Pointer_for_Purify(Transport_Cell());

/* PurifyLoop continues on the next page */
\f


/* PurifyLoop, continued */

      case TC_INTERNED_SYMBOL:
      case TC_UNINTERNED_SYMBOL:
	if (GC_Mode == PURE_COPY)
        { Temp = Vector_Ref(Temp, SYMBOL_NAME);
	  Old = Get_Pointer(Temp);
	  Setup_Internal(false, Transport_Indirect(), Indirect_BH(false));
	}
	/* Fall through */
      case_Fasdump_Pair:
	Setup_Pointer_for_Purify(Transport_Pair());

/* Because variables no longer contain pointers (except for the symbol),
   they are permitted into pure space now.  This changed when we stopped
   compiling references to auxilliary variables. */

      case TC_VARIABLE:					
#if false
	if (GC_Mode == PURE_COPY) break;
#endif
	/* Fall through */
      case_Purify_Triple:
	Setup_Pointer_for_Purify(Transport_Triple());

/* PurifyLoop continues on the next page */
\f


/* PurifyLoop, continued */

#ifdef QUADRUPLE
      case_Quadruple:
	Setup_Pointer_for_Purify(Transport_Quadruple());
#endif

	/* No need to handle futures specially here, since PurifyLoop
	   is always invoked after running GCLoop, which will have
	   spliced all spliceable futures unless the GC itself of the
	   GC dameons spliced them, but this should not occur.
	 */

      case TC_FUTURE:
      case TC_ENVIRONMENT:
	if (GC_Mode == PURE_COPY) break;
	/* Fall through */
      case_Purify_Vector:
	Setup_Pointer_for_Purify(Transport_Vector());

      default:
	fprintf(stderr,
		"Purify_Loop: Bad type code = 0x%02x\n",
		Type_Code(Temp));
	Invalid_Type_Code();
      } /* Switch_by_GC_Type */
  } /* For loop */
  *To_Pointer = To;
  return To;
} /* PurifyLoop */
\f


Pointer Purify(Object, Purify_Object)
Pointer Object, Purify_Object;

/* The algorithm is trickier than would first appear necessary.  This
   is because the size of the object being purified must be
   calculated.  The idea is that the entire object is copied into the
   new heap, and then a normal GC is done (the broken hearts created
   by the copy will, of course, now be used to relocate references to
   parts of the object).  If there is not enough room in constant
   space for the object, processing stops with a #!false return and
   the world flipped into the new heap.  Otherwise, the
   process is repeated, moving the object into constant space on the
   first pass and then doing a GC back into the original heap.

   Notice that in order to make a pure object, the copy process
   proceeds in two halves.  During the first half (which collects the
   pure part) Environments, Symbols, and Variables (i.e.  things whose
   contents change) are NOT copied.  Then a header is put down
   indicating constant (not pure) area, and then they ARE copied.

Purify continues on the next page
\f


Purify, continued

   The constant area contains a contiguous set of blocks of the
   following format:

  >>Top of Memory (Stack above here)<<

                   . (direction of growth)
                   .  ^
                   . / \
                   .  |
                   .  |
        |----------------------|...
        | END   | Total Size M |   . Where END   = TC_FIXNUM
        |----------------------|    .      SNMH  = TC_MANIFEST_SPECIAL_...
        | SNMH  |      1       |    |      CONST = TC_TRUE
        |----------------------|    |      PURE  = TC_FALSE
        |                      |    |
        |                      |    |
        |    CONSTANT AREA     |    |
        |                      |    |
        |                      |     .
     ...|----------------------|      >  M
    .   | CONST | Pure Size N  |     .
   .    |----------------------|    |
   |    | SNMH  |      1       |    |
   |    |----------------------|    |
   |    |                      |    |
N <     |                      |    |
   |    |      PURE AREA       |    |
   |    |                      |    |
   .    |                      |    .
    .   |----------------------|   .
     ...| PURE  | Total Size M |...
        |----------------------|
        | SNMH  | Pure Size N  |
        |----------------------|

  >>Base of Memory (Heap below here)<<

Purify continues on the next page
\f


Purify, continued */

{ long i, Length;
  Pointer *Heap_Start, *Result;

/* Pass 1 -- Copy object to new heap, then GC into that heap */

  GCFlip();
  Heap_Start = Free;
  *Free++ = Object;
  Result = GCLoop(Heap_Start, &Free);
  if (Free != Result)
  { fprintf(stderr, "\Purify: Pure Scan ended too early.\n");
    Microcode_Termination(TERM_BROKEN_HEART);
  }
  Length = (Free-Heap_Start)-1;		/* Length of object */
  GC();
  *Free++ = Make_Non_Pointer(TC_MANIFEST_VECTOR, 2);
  *Free++ = FIXNUM_0 + Length;
  *Free++ = Purify_Object;
  return Make_Pointer(TC_VECTOR, Free-3);
 }
\f


Pointer Purify_Pass_2(Info)
Pointer Info;
{ long Length = Get_Integer(Fast_Vector_Ref(Info, 1));
  Boolean Purify_Object = (Fast_Vector_Ref(Info, 2) == NIL) ? false : true;
  Pointer *New_Object, Relocated_Object, *Result;
  long Pure_Length;

  Relocated_Object = *Heap_Bottom;
  if (!Test_Pure_Space_Top(Free_Constant+Length+6)) return NIL;
  New_Object = Free_Constant;
  *Free_Constant++ = NIL;	/* Will hold pure space header */
  *Free_Constant++ = Relocated_Object;
  if (Purify_Object)
  { Result = PurifyLoop(New_Object+1, &Free_Constant, PURE_COPY);
    if (Free_Constant != Result)
    { fprintf(stderr, "\Purify: Pure Copy ended too early.\n");
      Microcode_Termination(TERM_BROKEN_HEART);
    }
    Pure_Length = (Free_Constant-New_Object) + 1;
  }
  else Pure_Length = 3;
  *Free_Constant++ = Make_Non_Pointer(TC_MANIFEST_SPECIAL_NM_VECTOR, 1);
  *Free_Constant++ = Make_Non_Pointer(CONSTANT_PART, Pure_Length);
  if (Purify_Object)
  { Result = PurifyLoop(New_Object + 1, &Free_Constant, CONSTANT_COPY);
    if (Result != Free_Constant)
    { fprintf(stderr, "\Purify: Constant Copy ended too early.\n");
      Microcode_Termination(TERM_BROKEN_HEART);
    }
  }
  else
  { Result = GCLoop(New_Object + 1, &Free_Constant);
    if (Result != Free_Constant)
    { fprintf(stderr, "\Purify: Constant Copy ended too early.\n");
      Microcode_Termination(TERM_BROKEN_HEART);
    }
  }
  *Free_Constant++ = Make_Non_Pointer(TC_MANIFEST_SPECIAL_NM_VECTOR, 1);
  *Free_Constant++ = Make_Non_Pointer(END_OF_BLOCK, Length+5);
  if (Length+6 != (Free_Constant-New_Object))
  { printf("Purify phase error %x, %x\n", Length, Free_Constant-New_Object);
    Microcode_Termination(TERM_EXIT);
  }
  *New_Object++ =
    Make_Non_Pointer(TC_MANIFEST_SPECIAL_NM_VECTOR, Pure_Length);
  *New_Object = Make_Non_Pointer(PURE_PART, Length+5);
  GCFlip();
  GC();
  Set_Pure_Top(Free_Constant);
  return TRUTH;
}
\f


Boolean Pure_Test(Obj_Address)
fast Pointer *Obj_Address;
{ fast Pointer *Where;
  Where = Free_Constant;
  while (Where > Constant_Space)
  { Where -= 1+Get_Integer(*(Where-1));
    if (Where < Obj_Address)
      return(Obj_Address <= (Where+Get_Integer(*Where)));
  }
  /* Not really needed, but ... */
  return false;
}

/* (PURE_P OBJECT)
      [Primitive number 0xBB]
      Returns #!TRUE if the object is pure (ie it doesn't point to any
      other object, or it is in a pure section of the constant space).
*/
Built_In_Primitive(Prim_Pure_P, 1, "PURE?")
{ Pointer Object;
  Primitive_1_Arg();

  if (GC_Type(Arg1) == GC_Non_Pointer) return TRUTH;
  Touch_In_Primitive(Arg1, Arg1);
  { Pointer *Obj_Address;
    Obj_Address = Get_Pointer(Arg1);
    if ((Is_Constant(Obj_Address)) && Pure_Test(Obj_Address))
      return TRUTH;
  }
  return NIL;
}
\f


Pointer Make_Impure(Object)
Pointer Object;
{ Pointer *Obj_Address, *New_Object, *New_Address, *P;
  long Length, Block_Length, i;

/* Calculate size of object to be "impurified" */
  Switch_by_GC_Type(Object)
  { case TC_BROKEN_HEART:
    case TC_MANIFEST_NM_VECTOR:
    case TC_MANIFEST_SPECIAL_NM_VECTOR:
    case_Non_Pointer:
      printf("Impurify Non-Pointer.\n");
      Microcode_Termination(TERM_NON_POINTER_RELOCATION);
    case TC_FUTURE:
    case_Vector:     Length = Vector_Length(Object) + 1; break;
    case_Quadruple:  Length = 4; break;
    case_Triple:     Length = 3; break;
    case_Pair:       Length = 2; break;
    case_Cell:       Length = 1; break;
    default:
      fprintf(stderr, "Impurify: Bad type code = 0x%02x\n",
	      Type_Code(Object));
      Invalid_Type_Code();
  }

/* Add a copy of the object to the last constant block in memory. */
  Obj_Address = Get_Pointer(Object);
  if (!Test_Pure_Space_Top(Free_Constant+Length)) return NIL;
  Block_Length = Get_Integer(*(Free_Constant-1));
  Free_Constant = Free_Constant-2;
  New_Address = Free_Constant;
  for (i=0; i < Length; i++) *Free_Constant++ = *Obj_Address++;
  *Free_Constant++ = Make_Non_Pointer(TC_MANIFEST_SPECIAL_NM_VECTOR, 1);
  *Free_Constant++ = Make_Non_Pointer(END_OF_BLOCK, Block_Length+Length);
  *(New_Address+2-Block_Length) =
	Make_Non_Pointer(PURE_PART, Block_Length+Length);
  Obj_Address -= Length;
  Set_Pure_Top(Free_Constant+Length);

/* Run through memory relocating pointers to this object, including
 * those in pure areas. */
  Update(Heap_Bottom, Free, Obj_Address, New_Address);
  Update(Stack_Pointer, Stack_Top, Obj_Address, New_Address);
  Update(Constant_Space, Free_Constant, Obj_Address, New_Address);
  return Make_Pointer(Type_Code(Object), New_Address);
}
\f


/* (IMPURIFY OBJECT)
      [Primitive number 0xBD]
*/
Built_In_Primitive(Prim_Impurify, 1, "IMPURIFY")
{ Pointer Result;
  Primitive_1_Arg();
  Touch_In_Primitive(Arg1, Arg1);
  Result = Make_Impure(Arg1);
  if (Result != NIL) return Result;
  Primitive_Error(ERR_IMPURIFY_OUT_OF_SPACE);
}

Update(From, To, Was, Will_Be)
fast Pointer *From, *To, *Was, *Will_Be;
{ for (; From < To; From++)
  { if (GC_Type(*From) == GC_Non_Pointer)
     { if (Safe_Type_Code(*From) == TC_MANIFEST_NM_VECTOR)
        From += Get_Integer(*From);
     }
     else if (Get_Pointer(*From) == Was)
          *From = Make_Pointer(Type_Code(*From), Will_Be);
  }
}
\f


/* (PRIMITIVE_PURIFY OBJECT PURE?)
      [Primitive number 0xB4]
      Copy an object from the heap into constant space.  This requires
      a spare heap, and is tricky to use -- it should only be used
      through the wrapper provided in the Scheme runtime system.

      To purify an object we just copy it into Pure Space in two
      parts with the appropriate headers and footers.  The actual
      copying is done by PurifyLoop above.  If we run out of room
      SCHEME crashes.

      Once the copy is complete we run a full GC which handles the
      broken hearts which now point into pure space.  On a 
      multiprocessor, this primitive uses the master-gc-loop and it
      should only be used as one would use master-gc-loop i.e. with
      everyone else halted.
*/

Built_In_Primitive(Prim_Primitive_Purify, 2, "PRIMITIVE-PURIFY")
{ long Result, Saved_Zone, Length;
  Pointer Object, *New_Object;

  Primitive_2_Args();
  Save_Time_Zone(Zone_Purify);
  if ((Arg2 != TRUTH) && (Arg2 != NIL))
    Primitive_Error(ERR_ARG_2_WRONG_TYPE);

  /* Pass 1 (Purify, above) does a first copy.  Then any GC daemons
     run, and then Purify_Pass_2 is called to copy back.
  */

  Touch_In_Primitive(Arg1, Object);
  if (Get_Fixed_Obj_Slot(GC_Daemon)==NIL)
    return Purify_Pass_2(Purify(Object, Arg2));
  Pop_Primitive_Frame(2);
 Will_Push(CONTINUATION_SIZE + STACK_ENV_EXTRA_SLOTS + 1);
  Store_Expression(Purify(Object, Arg2));
  Store_Return(RC_PURIFY_GC_1);
  Save_Cont();
  Push(Get_Fixed_Obj_Slot(GC_Daemon));
  Push(STACK_FRAME_HEADER);
 Pushed();
  longjmp(*Back_To_Eval, PRIM_APPLY);
}
\f


/* (CONSTANT? OBJECT)
      [Primitive number 0xBA]
      Returns #!TRUE if the object is in constant space or isn't a
      pointer.
*/
Built_In_Primitive(Prim_Constant_P, 1, "CONSTANT?")
{ Primitive_1_Arg();
  Touch_In_Primitive(Arg1, Arg1);
  return ((GC_Type(Arg1) == GC_Non_Pointer) ||
          ((Get_Pointer(Arg1) >= Constant_Space) &&
           (Get_Pointer(Arg1) < Free_Constant))) ?
         TRUTH : NIL;
}
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