vm/quotations.cpp

   1 #include "master.hpp"
   2
   3 namespace factor
   4 {
   5
   6 /* Simple non-optimizing compiler.
   7
   8 This is one of the two compilers implementing Factor; the second one is written
   9 in Factor and performs advanced optimizations. See basis/compiler/compiler.factor.
  10
  11 The non-optimizing compiler compiles a quotation at a time by concatenating
  12 machine code chunks; prolog, epilog, call word, jump to word, etc. These machine
  13 code chunks are generated from Factor code in basis/cpu/.../bootstrap.factor.
  14
  15 Calls to words and constant quotations (referenced by conditionals and dips)
  16 are direct jumps to machine code blocks. Literals are also referenced directly
  17 without going through the literal table.
  18
  19 It actually does do a little bit of very simple optimization:
  20
  21 1) Tail call optimization.
  22
  23 2) If a quotation is determined to not call any other words (except for a few
  24 special words which are open-coded, see below), then no prolog/epilog is
  25 generated.
  26
  27 3) When in tail position and immediately preceded by literal arguments, the
  28 'if' is generated inline, instead of as a call to the 'if' word.
  29
  30 4) When preceded by a quotation, calls to 'dip', '2dip' and '3dip' are
  31 open-coded as retain stack manipulation surrounding a subroutine call.
  32
  33 5) Sub-primitives are primitive words which are implemented in assembly and not
  34 in the VM. They are open-coded and no subroutine call is generated. This
  35 includes stack shufflers, some fixnum arithmetic words, and words such as tag,
  36 slot and eq?. A primitive call is relatively expensive (two subroutine calls)
  37 so this results in a big speedup for relatively little effort. */
  38
  39 void quotation_jit::init_quotation(cell quot)
  40 {
  41         elements = untag<quotation>(quot)->array;
  42 }
  43
  44 bool quotation_jit::primitive_call_p(cell i, cell length)
  45 {
  46         return (i + 2) == length && array_nth(elements.untagged(),i + 1) == parent->special_objects[JIT_PRIMITIVE_WORD];
  47 }
  48
  49 bool quotation_jit::fast_if_p(cell i, cell length)
  50 {
  51         return (i + 3) == length
  52                 && tagged<object>(array_nth(elements.untagged(),i + 1)).type_p(QUOTATION_TYPE)
  53                 && array_nth(elements.untagged(),i + 2) == parent->special_objects[JIT_IF_WORD];
  54 }
  55
  56 bool quotation_jit::fast_dip_p(cell i, cell length)
  57 {
  58         return (i + 2) <= length && array_nth(elements.untagged(),i + 1) == parent->special_objects[JIT_DIP_WORD];
  59 }
  60
  61 bool quotation_jit::fast_2dip_p(cell i, cell length)
  62 {
  63         return (i + 2) <= length && array_nth(elements.untagged(),i + 1) == parent->special_objects[JIT_2DIP_WORD];
  64 }
  65
  66 bool quotation_jit::fast_3dip_p(cell i, cell length)
  67 {
  68         return (i + 2) <= length && array_nth(elements.untagged(),i + 1) == parent->special_objects[JIT_3DIP_WORD];
  69 }
  70
  71 bool quotation_jit::mega_lookup_p(cell i, cell length)
  72 {
  73         return (i + 4) <= length
  74                 && tagged<object>(array_nth(elements.untagged(),i + 1)).type_p(FIXNUM_TYPE)
  75                 && tagged<object>(array_nth(elements.untagged(),i + 2)).type_p(ARRAY_TYPE)
  76                 && array_nth(elements.untagged(),i + 3) == parent->special_objects[MEGA_LOOKUP_WORD];
  77 }
  78
  79 bool quotation_jit::declare_p(cell i, cell length)
  80 {
  81         return (i + 2) <= length
  82                 && array_nth(elements.untagged(),i + 1) == parent->special_objects[JIT_DECLARE_WORD];
  83 }
  84
  85 bool quotation_jit::word_stack_frame_p(cell obj)
  86 {
  87         return to_boolean(untag<word>(obj)->subprimitive)
  88                 || obj == parent->special_objects[JIT_PRIMITIVE_WORD];
  89 }
  90
  91 bool quotation_jit::stack_frame_p()
  92 {
  93         fixnum length = array_capacity(elements.untagged());
  94
  95         for(fixnum i = 0; i < length; i++)
  96         {
  97                 cell obj = array_nth(elements.untagged(),i);
  98                 switch(tagged<object>(obj).type())
  99                 {
 100                 case WORD_TYPE:
 101                         if(i != length - 1 || word_stack_frame_p(obj))
 102                                 return true;
 103                         break;
 104                 case QUOTATION_TYPE:
 105                         if(fast_dip_p(i,length) || fast_2dip_p(i,length) || fast_3dip_p(i,length))
 106                                 return true;
 107                         break;
 108                 default:
 109                         break;
 110                 }
 111         }
 112
 113         return false;
 114 }
 115
 116 bool quotation_jit::trivial_quotation_p(array *elements)
 117 {
 118         return array_capacity(elements) == 1 && tagged<object>(array_nth(elements,0)).type_p(WORD_TYPE);
 119 }
 120
 121 void quotation_jit::emit_quot(cell quot_)
 122 {
 123         data_root<quotation> quot(quot_,parent);
 124
 125         array *elements = untag<array>(quot->array);
 126
 127         /* If the quotation consists of a single word, compile a direct call
 128         to the word. */
 129         if(trivial_quotation_p(elements))
 130                 literal(array_nth(elements,0));
 131         else
 132         {
 133                 if(compiling) parent->jit_compile_quot(quot.value(),relocate);
 134                 literal(quot.value());
 135         }
 136 }
 137
 138 /* Allocates memory */
 139 void quotation_jit::iterate_quotation()
 140 {
 141         bool stack_frame = stack_frame_p();
 142
 143         set_position(0);
 144
 145         if(stack_frame)
 146                 emit(parent->special_objects[JIT_PROLOG]);
 147
 148         cell i;
 149         cell length = array_capacity(elements.untagged());
 150         bool tail_call = false;
 151
 152         for(i = 0; i < length; i++)
 153         {
 154                 set_position(i);
 155
 156                 data_root<object> obj(array_nth(elements.untagged(),i),parent);
 157
 158                 switch(obj.type())
 159                 {
 160                 case WORD_TYPE:
 161                         /* Sub-primitives */
 162                         if(to_boolean(obj.as<word>()->subprimitive))
 163                         {
 164                                 tail_call = emit_subprimitive(obj.value(), /* word */
 165                                         i == length - 1, /* tail_call_p */
 166                                         stack_frame); /* stack_frame_p */
 167                         }
 168                         /* Everything else */
 169                         else if(i == length - 1)
 170                         {
 171                                 if(stack_frame) emit(parent->special_objects[JIT_EPILOG]);
 172                                 tail_call = true;
 173                                 word_jump(obj.value());
 174                         }
 175                         else
 176                                 word_call(obj.value());
 177                         break;
 178                 case WRAPPER_TYPE:
 179                         push(obj.as<wrapper>()->object);
 180                         break;
 181                 case FIXNUM_TYPE:
 182                         /* Primitive calls */
 183                         if(primitive_call_p(i,length))
 184                         {
 185                                 /* On PowerPC, the VM pointer is stored as a register; on other
 186                                    platforms, the RT_VM relocation is used and it needs an offset
 187                                    parameter */
 188 #ifndef FACTOR_PPC
 189                                 parameter(tag_fixnum(0));
 190 #endif
 191                                 parameter(obj.value());
 192                                 emit(parent->special_objects[JIT_PRIMITIVE]);
 193
 194                                 i++;
 195                         }
 196                         else
 197                                 push(obj.value());
 198                         break;
 199                 case QUOTATION_TYPE:
 200                         /* 'if' preceeded by two literal quotations (this is why if and ? are
 201                            mutually recursive in the library, but both still work) */
 202                         if(fast_if_p(i,length))
 203                         {
 204                                 if(stack_frame) emit(parent->special_objects[JIT_EPILOG]);
 205                                 tail_call = true;
 206
 207                                 emit_quot(array_nth(elements.untagged(),i));
 208                                 emit_quot(array_nth(elements.untagged(),i + 1));
 209                                 emit(parent->special_objects[JIT_IF]);
 210
 211                                 i += 2;
 212                         }
 213                         /* dip */
 214                         else if(fast_dip_p(i,length))
 215                         {
 216                                 emit_quot(obj.value());
 217                                 emit(parent->special_objects[JIT_DIP]);
 218                                 i++;
 219                         }
 220                         /* 2dip */
 221                         else if(fast_2dip_p(i,length))
 222                         {
 223                                 emit_quot(obj.value());
 224                                 emit(parent->special_objects[JIT_2DIP]);
 225                                 i++;
 226                         }
 227                         /* 3dip */
 228                         else if(fast_3dip_p(i,length))
 229                         {
 230                                 emit_quot(obj.value());
 231                                 emit(parent->special_objects[JIT_3DIP]);
 232                                 i++;
 233                         }
 234                         else
 235                                 push(obj.value());
 236                         break;
 237                 case ARRAY_TYPE:
 238                         /* Method dispatch */
 239                         if(mega_lookup_p(i,length))
 240                         {
 241                                 if(stack_frame) emit(parent->special_objects[JIT_EPILOG]);
 242                                 tail_call = true;
 243                                 emit_mega_cache_lookup(
 244                                         array_nth(elements.untagged(),i),
 245                                         untag_fixnum(array_nth(elements.untagged(),i + 1)),
 246                                         array_nth(elements.untagged(),i + 2));
 247                                 i += 3;
 248                         }
 249                         /* Non-optimizing compiler ignores declarations */
 250                         else if(declare_p(i,length))
 251                                 i++;
 252                         else
 253                                 push(obj.value());
 254                         break;
 255                 default:
 256                         push(obj.value());
 257                         break;
 258                 }
 259         }
 260
 261         if(!tail_call)
 262         {
 263                 set_position(length);
 264
 265                 if(stack_frame) emit(parent->special_objects[JIT_EPILOG]);
 266                 emit(parent->special_objects[JIT_RETURN]);
 267         }
 268 }
 269
 270 void factor_vm::set_quot_xt(quotation *quot, code_block *code)
 271 {
 272         quot->code = code;
 273         quot->xt = code->xt();
 274 }
 275
 276 /* Allocates memory */
 277 code_block *factor_vm::jit_compile_quot(cell owner_, cell quot_, bool relocating)
 278 {
 279         data_root<object> owner(owner_,this);
 280         data_root<quotation> quot(quot_,this);
 281
 282         quotation_jit compiler(owner.value(),true,relocating,this);
 283         compiler.init_quotation(quot.value());
 284         compiler.iterate_quotation();
 285
 286         code_block *compiled = compiler.to_code_block();
 287
 288         if(relocating) initialize_code_block(compiled);
 289
 290         return compiled;
 291 }
 292
 293 void factor_vm::jit_compile_quot(cell quot_, bool relocating)
 294 {
 295         data_root<quotation> quot(quot_,this);
 296
 297         if(quot->code == NULL || quot->code == lazy_jit_compile_block())
 298         {
 299                 code_block *compiled = jit_compile_quot(quot.value(),quot.value(),relocating);
 300                 set_quot_xt(quot.untagged(),compiled);
 301         }
 302 }
 303
 304 void factor_vm::primitive_jit_compile()
 305 {
 306         jit_compile_quot(ctx->pop(),true);
 307 }
 308
 309 code_block *factor_vm::lazy_jit_compile_block()
 310 {
 311         return untag<word>(special_objects[LAZY_JIT_COMPILE_WORD])->code;
 312 }
 313
 314 /* push a new quotation on the stack */
 315 void factor_vm::primitive_array_to_quotation()
 316 {
 317         quotation *quot = allot<quotation>(sizeof(quotation));
 318
 319         quot->array = ctx->peek();
 320         quot->cached_effect = false_object;
 321         quot->cache_counter = false_object;
 322         set_quot_xt(quot,lazy_jit_compile_block());
 323
 324         ctx->replace(tag<quotation>(quot));
 325 }
 326
 327 void factor_vm::primitive_quotation_xt()
 328 {
 329         quotation *quot = untag_check<quotation>(ctx->peek());
 330         ctx->replace(allot_cell((cell)quot->xt));
 331 }
 332
 333 /* Allocates memory */
 334 fixnum factor_vm::quot_code_offset_to_scan(cell quot_, cell offset)
 335 {
 336         data_root<quotation> quot(quot_,this);
 337         data_root<array> array(quot->array,this);
 338
 339         quotation_jit compiler(quot.value(),false,false,this);
 340         compiler.init_quotation(quot.value());
 341         compiler.compute_position(offset);
 342         compiler.iterate_quotation();
 343
 344         return compiler.get_position();
 345 }
 346
 347 cell factor_vm::lazy_jit_compile(cell quot_)
 348 {
 349         data_root<quotation> quot(quot_,this);
 350         jit_compile_quot(quot.value(),true);
 351         return quot.value();
 352 }
 353
 354 VM_C_API cell lazy_jit_compile(cell quot, factor_vm *parent)
 355 {
 356         return parent->lazy_jit_compile(quot);
 357 }
 358
 359 void factor_vm::primitive_quot_compiled_p()
 360 {
 361         tagged<quotation> quot(ctx->pop());
 362         quot.untag_check(this);
 363         ctx->push(tag_boolean(quot->code != lazy_jit_compile_block()));
 364 }
 365
 366 cell factor_vm::find_all_quotations()
 367 {
 368         return instances(QUOTATION_TYPE);
 369 }
 370
 371 void factor_vm::initialize_all_quotations()
 372 {
 373         data_root<array> quotations(find_all_quotations(),this);
 374
 375         cell length = array_capacity(quotations.untagged());
 376         for(cell i = 0; i < length; i++)
 377         {
 378                 data_root<quotation> quot(array_nth(quotations.untagged(),i),this);
 379                 if(!quot->code)
 380                         set_quot_xt(quot.untagged(),lazy_jit_compile_block());
 381         }
 382 }
 383
 384 }