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         // Subprimitives should be flagged with whether they require a stack frame.
  88         // See #295.
  89         return (to_boolean(untag<word>(obj)->subprimitive)
  90                         && obj != parent->special_objects[SIGNAL_HANDLER_WORD]
  91                         && obj != parent->special_objects[LEAF_SIGNAL_HANDLER_WORD]
  92                         && obj != parent->special_objects[FFI_SIGNAL_HANDLER_WORD]
  93                         && obj != parent->special_objects[FFI_LEAF_SIGNAL_HANDLER_WORD])
  94                 || obj == parent->special_objects[JIT_PRIMITIVE_WORD];
  95 }
  96
  97 bool quotation_jit::stack_frame_p()
  98 {
  99         fixnum length = array_capacity(elements.untagged());
 100
 101         for(fixnum i = 0; i < length; i++)
 102         {
 103                 cell obj = array_nth(elements.untagged(),i);
 104                 switch(tagged<object>(obj).type())
 105                 {
 106                 case WORD_TYPE:
 107                         if(i != length - 1 || word_stack_frame_p(obj))
 108                                 return true;
 109                         break;
 110                 case QUOTATION_TYPE:
 111                         if(fast_dip_p(i,length) || fast_2dip_p(i,length) || fast_3dip_p(i,length))
 112                                 return true;
 113                         break;
 114                 default:
 115                         break;
 116                 }
 117         }
 118
 119         return false;
 120 }
 121
 122 bool quotation_jit::trivial_quotation_p(array *elements)
 123 {
 124         return array_capacity(elements) == 1 && tagged<object>(array_nth(elements,0)).type_p(WORD_TYPE);
 125 }
 126
 127 void quotation_jit::emit_epilog(bool stack_frame)
 128 {
 129         emit(parent->special_objects[JIT_SAFEPOINT]);
 130         if(stack_frame) emit(parent->special_objects[JIT_EPILOG]);
 131 }
 132
 133 void quotation_jit::emit_quot(cell quot_)
 134 {
 135         data_root<quotation> quot(quot_,parent);
 136
 137         array *elements = untag<array>(quot->array);
 138
 139         /* If the quotation consists of a single word, compile a direct call
 140         to the word. */
 141         if(trivial_quotation_p(elements))
 142                 literal(array_nth(elements,0));
 143         else
 144         {
 145                 if(compiling) parent->jit_compile_quot(quot.value(),relocate);
 146                 literal(quot.value());
 147         }
 148 }
 149
 150 /* Allocates memory */
 151 void quotation_jit::iterate_quotation()
 152 {
 153         bool stack_frame = stack_frame_p();
 154
 155         set_position(0);
 156
 157         if(stack_frame)
 158                 emit(parent->special_objects[JIT_PROLOG]);
 159
 160         cell i;
 161         cell length = array_capacity(elements.untagged());
 162         bool tail_call = false;
 163
 164         for(i = 0; i < length; i++)
 165         {
 166                 set_position(i);
 167
 168                 data_root<object> obj(array_nth(elements.untagged(),i),parent);
 169
 170                 switch(obj.type())
 171                 {
 172                 case WORD_TYPE:
 173                         /* Sub-primitives */
 174                         if(to_boolean(obj.as<word>()->subprimitive))
 175                         {
 176                                 tail_call = emit_subprimitive(obj.value(), /* word */
 177                                         i == length - 1, /* tail_call_p */
 178                                         stack_frame); /* stack_frame_p */
 179                         }
 180                         /* Everything else */
 181                         else if(i == length - 1)
 182                         {
 183                                 emit_epilog(stack_frame);
 184                                 tail_call = true;
 185                                 word_jump(obj.value());
 186                         }
 187                         else
 188                                 word_call(obj.value());
 189                         break;
 190                 case WRAPPER_TYPE:
 191                         push(obj.as<wrapper>()->object);
 192                         break;
 193                 case BYTE_ARRAY_TYPE:
 194                         /* Primitive calls */
 195                         if(primitive_call_p(i,length))
 196                         {
 197                                 /* On x86-64 and PowerPC, the VM pointer is stored in
 198                                 a register; on other platforms, the RT_VM relocation
 199                                 is used and it needs an offset parameter */
 200 #ifdef FACTOR_X86
 201                                 parameter(tag_fixnum(0));
 202 #endif
 203                                 parameter(obj.value());
 204                                 parameter(false_object);
 205 #ifdef FACTOR_PPC_TOC
 206                                 parameter(obj.value());
 207                                 parameter(false_object);
 208 #endif
 209                                 emit(parent->special_objects[JIT_PRIMITIVE]);
 210
 211                                 i++;
 212                         }
 213                         else
 214                                 push(obj.value());
 215                         break;
 216                 case QUOTATION_TYPE:
 217                         /* 'if' preceeded by two literal quotations (this is why if and ? are
 218                            mutually recursive in the library, but both still work) */
 219                         if(fast_if_p(i,length))
 220                         {
 221                                 emit_epilog(stack_frame);
 222                                 tail_call = true;
 223
 224                                 emit_quot(array_nth(elements.untagged(),i));
 225                                 emit_quot(array_nth(elements.untagged(),i + 1));
 226                                 emit(parent->special_objects[JIT_IF]);
 227
 228                                 i += 2;
 229                         }
 230                         /* dip */
 231                         else if(fast_dip_p(i,length))
 232                         {
 233                                 emit_quot(obj.value());
 234                                 emit(parent->special_objects[JIT_DIP]);
 235                                 i++;
 236                         }
 237                         /* 2dip */
 238                         else if(fast_2dip_p(i,length))
 239                         {
 240                                 emit_quot(obj.value());
 241                                 emit(parent->special_objects[JIT_2DIP]);
 242                                 i++;
 243                         }
 244                         /* 3dip */
 245                         else if(fast_3dip_p(i,length))
 246                         {
 247                                 emit_quot(obj.value());
 248                                 emit(parent->special_objects[JIT_3DIP]);
 249                                 i++;
 250                         }
 251                         else
 252                                 push(obj.value());
 253                         break;
 254                 case ARRAY_TYPE:
 255                         /* Method dispatch */
 256                         if(mega_lookup_p(i,length))
 257                         {
 258                                 emit_epilog(stack_frame);
 259                                 tail_call = true;
 260                                 emit_mega_cache_lookup(
 261                                         array_nth(elements.untagged(),i),
 262                                         untag_fixnum(array_nth(elements.untagged(),i + 1)),
 263                                         array_nth(elements.untagged(),i + 2));
 264                                 i += 3;
 265                         }
 266                         /* Non-optimizing compiler ignores declarations */
 267                         else if(declare_p(i,length))
 268                                 i++;
 269                         else
 270                                 push(obj.value());
 271                         break;
 272                 default:
 273                         push(obj.value());
 274                         break;
 275                 }
 276         }
 277
 278         if(!tail_call)
 279         {
 280                 set_position(length);
 281
 282                 emit_epilog(stack_frame);
 283                 emit(parent->special_objects[JIT_RETURN]);
 284         }
 285 }
 286
 287 /* Allocates memory */
 288 code_block *factor_vm::jit_compile_quot(cell owner_, cell quot_, bool relocating)
 289 {
 290         data_root<object> owner(owner_,this);
 291         data_root<quotation> quot(quot_,this);
 292
 293         quotation_jit compiler(owner.value(),true,relocating,this);
 294         compiler.init_quotation(quot.value());
 295         compiler.iterate_quotation();
 296
 297         code_block *compiled = compiler.to_code_block();
 298
 299         if(relocating) initialize_code_block(compiled);
 300
 301         return compiled;
 302 }
 303
 304 void factor_vm::jit_compile_quot(cell quot_, bool relocating)
 305 {
 306         data_root<quotation> quot(quot_,this);
 307         if(!quot_compiled_p(quot.untagged()))
 308         {
 309                 code_block *compiled = jit_compile_quot(quot.value(),quot.value(),relocating);
 310                 quot.untagged()->entry_point = compiled->entry_point();
 311         }
 312 }
 313
 314 void factor_vm::primitive_jit_compile()
 315 {
 316         jit_compile_quot(ctx->pop(),true);
 317 }
 318
 319 void *factor_vm::lazy_jit_compile_entry_point()
 320 {
 321         return untag<word>(special_objects[LAZY_JIT_COMPILE_WORD])->entry_point;
 322 }
 323
 324 /* push a new quotation on the stack */
 325 void factor_vm::primitive_array_to_quotation()
 326 {
 327         quotation *quot = allot<quotation>(sizeof(quotation));
 328
 329         quot->array = ctx->peek();
 330         quot->cached_effect = false_object;
 331         quot->cache_counter = false_object;
 332         quot->entry_point = lazy_jit_compile_entry_point();
 333
 334         ctx->replace(tag<quotation>(quot));
 335 }
 336
 337 void factor_vm::primitive_quotation_code()
 338 {
 339         quotation *quot = untag_check<quotation>(ctx->pop());
 340
 341         ctx->push(from_unsigned_cell((cell)quot->entry_point));
 342         ctx->push(from_unsigned_cell((cell)quot->code() + quot->code()->size()));
 343 }
 344
 345 /* Allocates memory */
 346 fixnum factor_vm::quot_code_offset_to_scan(cell quot_, cell offset)
 347 {
 348         data_root<quotation> quot(quot_,this);
 349         data_root<array> array(quot->array,this);
 350
 351         quotation_jit compiler(quot.value(),false,false,this);
 352         compiler.init_quotation(quot.value());
 353         compiler.compute_position(offset);
 354         compiler.iterate_quotation();
 355
 356         return compiler.get_position();
 357 }
 358
 359 cell factor_vm::lazy_jit_compile(cell quot_)
 360 {
 361         data_root<quotation> quot(quot_,this);
 362
 363         assert(!quot_compiled_p(quot.untagged()));
 364
 365         code_block *compiled = jit_compile_quot(quot.value(),quot.value(),true);
 366         quot.untagged()->entry_point = compiled->entry_point();
 367
 368         return quot.value();
 369 }
 370
 371 VM_C_API cell lazy_jit_compile(cell quot, factor_vm *parent)
 372 {
 373         return parent->lazy_jit_compile(quot);
 374 }
 375
 376 bool factor_vm::quot_compiled_p(quotation *quot)
 377 {
 378         return quot->entry_point != NULL && quot->entry_point != lazy_jit_compile_entry_point();
 379 }
 380
 381 void factor_vm::primitive_quot_compiled_p()
 382 {
 383         tagged<quotation> quot(ctx->pop());
 384         quot.untag_check(this);
 385         ctx->push(tag_boolean(quot_compiled_p(quot.untagged())));
 386 }
 387
 388 cell factor_vm::find_all_quotations()
 389 {
 390         return instances(QUOTATION_TYPE);
 391 }
 392
 393 void factor_vm::initialize_all_quotations()
 394 {
 395         data_root<array> quotations(find_all_quotations(),this);
 396
 397         cell length = array_capacity(quotations.untagged());
 398         for(cell i = 0; i < length; i++)
 399         {
 400                 data_root<quotation> quot(array_nth(quotations.untagged(),i),this);
 401                 if(!quot->entry_point)
 402                         quot.untagged()->entry_point = lazy_jit_compile_entry_point();
 403         }
 404 }
 405
 406 }