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Remove indirection in structs

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* libguile/gc.c (scm_storage_prehistory): Register struct displacement
  here.
* libguile/goops.c (scm_sys_modify_instance): Fix the format of a
  comment.
* libguile/modules.c (scm_post_boot_init_modules): Update for new format
  of struct vtable references.
* libguile/struct.c (scm_i_alloc_struct): Update to include slots
  directly, instead of being indirected by an embedded pointer.
  (scm_c_make_structv, scm_allocate_struct, scm_i_make_vtable_vtable):
  Adapt to pass vtable bits as argument to scm_i_alloc_struct, not
  vtable data bits.
  (scm_init_struct): Remove two-word displacement from libgc.
* libguile/struct.h: Update comment.
  (SCM_STRUCT_SLOTS, SCM_STRUCT_DATA): Update definitions.
  (SCM_STRUCT_VTABLE_DATA, SCM_STRUCT_VTABLE_SLOTS): Remove.
  (SCM_STRUCT_VTABLE, SCM_STRUCT_LAYOUT, SCM_STRUCT_PRINTER)
  (SCM_STRUCT_FINALIZER, SCM_STRUCT_VTABLE_FLAGS)
  (SCM_STRUCT_VTABLE_FLAG_IS_SET): Simplify definitions.
* module/system/base/types.scm (cell->object, address->inferior-struct):
  Adapt to struct representation change.
This commit is contained in:
Andy Wingo 2017-09-07 16:55:30 +02:00
parent 4898959901
commit 7e91ff651b
6 changed files with 51 additions and 95 deletions
Download patch file Download diff file Expand all files Collapse all files

73
libguile/struct.h
View file

@ -3,7 +3,7 @@
#ifndef SCM_STRUCT_H
#define SCM_STRUCT_H
/* Copyright (C) 1995,1997,1999,2000,2001, 2006, 2007, 2008, 2009, 2010, 2011, 2012, 2013, 2015 Free Software Foundation, Inc.
/* Copyright (C) 1995,1997,1999,2000,2001, 2006, 2007, 2008, 2009, 2010, 2011, 2012, 2013, 2015, 2017 Free Software Foundation, Inc.
*
* This library is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public License
@ -28,42 +28,28 @@
/* The relationship between a struct and its vtable is a bit complicated,
because we want structs to be used as GOOPS' native representation -- which
in turn means we need support for changing the "class" (vtable) of an
"instance" (struct). This necessitates some indirection and trickery.
/* Structs are sequences of words where the first word points to the
struct's vtable, and the rest are its slots. The vtable indicates
how many words are in the struct among other meta-information. A
vtable is itself a struct and as such has a vtable, and so on until
you get to a root struct that is its own vtable.
To summarize, structs are laid out this way:
.-------.
| |
.----------------+---v------------- -
| vtable | data | slot0 | slot1 |
`----------------+----------------- -
| .-------.
| | |
.---v------------+---v------------- -
| vtable | data | slot0 | slot1 |
`----------------+----------------- -
.--------+----------------- -
| vtable | slot0 | slot1 |
`--------+----------------- -
|
|
.---v----+----------------- -
| vtable | slot0 | slot1 |
`--------+----------------- -
|
v
...
.-------.
| | |
.---v------------+---v------------- -
.-| vtable | data | slot0 | slot1 |
| `----------------+----------------- -
|
.---v----+----------------- -
.-| vtable | slot0 | slot1 |
| `--------+----------------- -
| ^
`-----'
The DATA indirection (which corresponds to `SCM_STRUCT_DATA ()') is necessary
to implement class redefinition.
For more details, see:
http://wingolog.org/archives/2009/11/09/class-redefinition-in-guile
*/
/* All vtables have the following fields. */
@ -123,10 +109,10 @@
typedef void (*scm_t_struct_finalize) (SCM obj);
#define SCM_STRUCTP(X) (!SCM_IMP(X) && (SCM_TYP3(X) == scm_tc3_struct))
#define SCM_STRUCT_SLOTS(X) ((SCM*)SCM_CELL_WORD_1 ((X)))
#define SCM_STRUCT_SLOTS(X) (SCM_CELL_OBJECT_LOC(X, 1))
#define SCM_STRUCT_SLOT_REF(X,I) (SCM_STRUCT_SLOTS (X)[(I)])
#define SCM_STRUCT_SLOT_SET(X,I,V) SCM_STRUCT_SLOTS (X)[(I)]=(V)
#define SCM_STRUCT_DATA(X) ((scm_t_bits*)SCM_CELL_WORD_1 (X))
#define SCM_STRUCT_DATA(X) ((scm_t_bits*)SCM_STRUCT_SLOTS (X))
#define SCM_STRUCT_DATA_REF(X,I) (SCM_STRUCT_DATA (X)[(I)])
#define SCM_STRUCT_DATA_SET(X,I,V) SCM_STRUCT_DATA (X)[(I)]=(V)
@ -145,18 +131,12 @@ typedef void (*scm_t_struct_finalize) (SCM obj);
#define SCM_VTABLE_NAME(X) (SCM_STRUCT_SLOT_REF (X, scm_vtable_index_name))
#define SCM_SET_VTABLE_NAME(X,V) (SCM_STRUCT_SLOT_SET (X, scm_vtable_index_name, V))
/* Structs hold a pointer to their vtable's data, not the vtable itself. To get
the vtable we have to do an indirection through the self slot. */
#define SCM_STRUCT_VTABLE_DATA(X) ((scm_t_bits*)(SCM_CELL_WORD_0 (X) - scm_tc3_struct))
#define SCM_STRUCT_VTABLE_SLOTS(X) ((SCM*)(SCM_CELL_WORD_0 (X) - scm_tc3_struct))
#define SCM_STRUCT_VTABLE(X) (SCM_STRUCT_VTABLE_SLOTS(X)[scm_vtable_index_self])
/* But often we just need to access the vtable's data; we can do that without
the data->self->data indirection. */
#define SCM_STRUCT_LAYOUT(X) (SCM_STRUCT_VTABLE_SLOTS (X)[scm_vtable_index_layout])
#define SCM_STRUCT_PRINTER(X) (SCM_STRUCT_VTABLE_SLOTS (X)[scm_vtable_index_instance_printer])
#define SCM_STRUCT_FINALIZER(X) ((scm_t_struct_finalize)SCM_STRUCT_VTABLE_DATA (X)[scm_vtable_index_instance_finalize])
#define SCM_STRUCT_VTABLE_FLAGS(X) (SCM_STRUCT_VTABLE_DATA (X)[scm_vtable_index_flags])
#define SCM_STRUCT_VTABLE_FLAG_IS_SET(X,F) (SCM_STRUCT_VTABLE_DATA (X)[scm_vtable_index_flags]&(F))
#define SCM_STRUCT_VTABLE(X) (SCM_PACK (SCM_CELL_WORD_0 (X) - scm_tc3_struct))
#define SCM_STRUCT_LAYOUT(X) (SCM_VTABLE_LAYOUT (SCM_STRUCT_VTABLE (X)))
#define SCM_STRUCT_PRINTER(X) (SCM_VTABLE_INSTANCE_PRINTER (SCM_STRUCT_VTABLE (X)))
#define SCM_STRUCT_FINALIZER(X) (SCM_VTABLE_INSTANCE_FINALIZER (SCM_STRUCT_VTABLE (X)))
#define SCM_STRUCT_VTABLE_FLAGS(X) (SCM_VTABLE_FLAGS (SCM_STRUCT_VTABLE (X)))
#define SCM_STRUCT_VTABLE_FLAG_IS_SET(X,F) (SCM_VTABLE_FLAG_IS_SET (SCM_STRUCT_VTABLE (X), (F)))
#define SCM_STRUCT_APPLICABLE_P(X) (SCM_STRUCT_VTABLE_FLAG_IS_SET ((X), SCM_VTABLE_FLAG_APPLICABLE))
#define SCM_STRUCT_SETTER_P(X) (SCM_STRUCT_VTABLE_FLAG_IS_SET ((X), SCM_VTABLE_FLAG_SETTER))
@ -191,7 +171,6 @@ SCM_API void scm_print_struct (SCM exp, SCM port, scm_print_state *);
SCM_INTERNAL SCM scm_i_struct_equalp (SCM s1, SCM s2);
SCM_INTERNAL unsigned long scm_struct_ihashq (SCM, unsigned long, void *);
SCM_INTERNAL SCM scm_i_alloc_struct (scm_t_bits *vtable_data, int n_words);
SCM_INTERNAL void scm_i_struct_inherit_vtable_magic (SCM vtable, SCM obj);
SCM_INTERNAL void scm_init_struct (void);