doc/ref/compiler.texi

   1 @c -*-texinfo-*-
   2 @c This is part of the GNU Guile Reference Manual.
   3 @c Copyright (C)  2008
   4 @c   Free Software Foundation, Inc.
   5 @c See the file guile.texi for copying conditions.
   6
   7 @node Compiling to the Virtual Machine
   8 @section Compiling to the Virtual Machine
   9
  10 Compilers have a mystique about them that is attractive and
  11 off-putting at the same time. They are attractive because they are
  12 magical -- they transform inert text into live results, like throwing
  13 the switch on Frankenstein. However, this magic is perceived by many
  14 to be impenetrable.
  15
  16 This section aims to pull back the veil from over Guile's compiler
  17 implementation, some reference to the wizard of oz FIXME.
  18
  19 REFFIXME, if you're lost and you just wanted to know how to compile
  20 your .scm file.
  21
  22 @menu
  23 * Compiler Tower::
  24 * The Scheme Compiler::
  25 * GHIL::
  26 * GLIL::
  27 * Object Code::
  28 @end menu
  29
  30 @node Compiler Tower
  31 @subsection Compiler Tower
  32
  33 Guile's compiler is quite simple, actually -- its @emph{compilers}, to
  34 put it more accurately. Guile defines a tower of languages, starting
  35 at Scheme and progressively simplifying down to languages that
  36 resemble the VM instruction set (REFFIXME).
  37
  38 Each language knows how to compile to the next, so each step is simple
  39 and understandable. Furthermore, this set of languages is not
  40 hardcoded into Guile, so it is possible for the user to add new
  41 high-level languages, new passes, or even different compilation
  42 targets.
  43
  44 lookup-language
  45 (lang xxx spec)
  46
  47 (system-base-language)
  48
  49 describe:
  50
  51 (define-record <language>
  52   name
  53   title
  54   version
  55   reader
  56   printer
  57   (parser #f)
  58   (read-file #f)
  59   (compilers '())
  60   (evaluator #f))
  61
  62 (define-macro (define-language name . spec)
  63
  64 (lookup-compilation-order from to)
  65
  66 language definition
  67
  68 compiling from here to there
  69
  70 the normal tower: scheme, ghil, glil, object code
  71 maybe from there serialized to disk
  72 or if at repl, brought back to life by compiling to ``value''
  73
  74 compile-file defaults to compiling to objcode
  75 compile defaults to compiling to value
  76
  77 ((lambda (x) ((compile x) x)) '(lambda (x) ((compile x) x)))
  78 quine
  79
  80 @node The Scheme Compiler
  81 @subsection The Scheme Compiler
  82
  83 macro expansion
  84
  85 define-scheme-translator
  86
  87 inlining
  88
  89 format of the environment
  90
  91 compile-time-environment
  92
  93 symbols resolved as local, external, or toplevel
  94
  95 @node GHIL
  96 @subsection GHIL
  97
  98 ghil environments
  99
 100 structured, typed intermediate language, close to scheme
 101 with an s-expression representation
 102
 103 ,lang ghil
 104
 105 some pre-optimization
 106
 107 real name of the game is closure elimination -- fixing letrec
 108
 109 @node GLIL
 110 @subsection GLIL
 111
 112 structured, typed intermediate language, close to object code
 113
 114 passes through the env
 115
 116 no let, no lambda, no closures, just labels and branches and constants
 117 and code. Well, there's a bit more, but that's the flavor of GLIL.
 118
 119 Compiled code will effectively be a thunk, of no arguments, but
 120 optionally closing over some number of variables (which should be
 121 captured via `make-closure' REFFIXME.
 122
 123 @node Object Code
 124 @subsection Object Code
 125
 126 describe the env -- module + externals (the actual values!)
 127
 128 The env is used when compiling to value -- effectively calling the
 129 thunk from objcode->program with a certain current module and with
 130 those externals. so you can recompile a closure at runtime, a trick
 131 that goops uses.
 132