llint/LowLevelInterpreter.cpp

   1 /*
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  10  *    notice, this list of conditions and the following disclaimer in the
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  25
  26 #include "config.h"
  27 #include "LowLevelInterpreter.h"
  28
  29 #if ENABLE(LLINT)
  30
  31 #include "LLIntOfflineAsmConfig.h"
  32 #include <wtf/InlineASM.h>
  33
  34 #if ENABLE(LLINT_C_LOOP)
  35 #include "CodeBlock.h"
  36 #include "LLIntCLoop.h"
  37 #include "LLIntSlowPaths.h"
  38 #include "Operations.h"
  39 #include "VMInspector.h"
  40 #include <wtf/Assertions.h>
  41 #include <wtf/MathExtras.h>
  42
  43 using namespace JSC::LLInt;
  44
  45 // LLInt C Loop opcodes
  46 // ====================
  47 // In the implementation of the C loop, the LLint trampoline glue functions
  48 // (e.g. llint_program_prologue, llint_eval_prologue, etc) are addressed as
  49 // if they are bytecode handlers. That means the names of the trampoline
  50 // functions will be added to the OpcodeID list via the
  51 // FOR_EACH_LLINT_OPCODE_EXTENSION() macro that FOR_EACH_OPCODE_ID()
  52 // includes.
  53 //
  54 // In addition, some JIT trampoline functions which are needed by LLInt
  55 // (e.g. getHostCallReturnValue, ctiOpThrowNotCaught) are also added as
  56 // bytecodes, and the CLoop will provide bytecode handlers for them.
  57 //
  58 // In the CLoop, we can only dispatch indirectly to these bytecodes
  59 // (including the LLInt and JIT extensions). All other dispatches
  60 // (i.e. goto's) must be to a known label (i.e. local / global labels).
  61
  62
  63 // How are the opcodes named?
  64 // ==========================
  65 // Here is a table to show examples of how each of the manifestation of the
  66 // opcodes are named:
  67 //
  68 //   Type:                        Opcode            Trampoline Glue
  69 //                                ======            ===============
  70 //   [In the llint .asm files]
  71 //   llint labels:                llint_op_enter    llint_program_prologue
  72 //
  73 //   OpcodeID:                    op_enter          llint_program
  74 //                                [in Opcode.h]     [in LLIntOpcode.h]
  75 //
  76 //   When using a switch statement dispatch in the CLoop, each "opcode" is
  77 //   a case statement:
  78 //   Opcode:                      case op_enter:    case llint_program_prologue:
  79 //
  80 //   When using a computed goto dispatch in the CLoop, each opcode is a label:
  81 //   Opcode:                      op_enter:         llint_program_prologue:
  82
  83
  84 //============================================================================
  85 // Define the opcode dispatch mechanism when using the C loop:
  86 //
  87
  88 // These are for building a C Loop interpreter:
  89 #define OFFLINE_ASM_BEGIN
  90 #define OFFLINE_ASM_END
  91
  92
  93 #define OFFLINE_ASM_OPCODE_LABEL(opcode) DEFINE_OPCODE(opcode)
  94 #if ENABLE(COMPUTED_GOTO_OPCODES)
  95     #define OFFLINE_ASM_GLUE_LABEL(label)  label:
  96 #else
  97     #define OFFLINE_ASM_GLUE_LABEL(label)  case label: label:
  98 #endif
  99
 100 #define OFFLINE_ASM_LOCAL_LABEL(label)   label:
 101
 102
 103 //============================================================================
 104 // Some utilities:
 105 //
 106
 107 namespace JSC {
 108 namespace LLInt {
 109
 110 #if USE(JSVALUE32_64)
 111 static double Ints2Double(uint32_t lo, uint32_t hi)
 112 {
 113     union {
 114         double dval;
 115         uint64_t ival64;
 116     } u;
 117     u.ival64 = (static_cast<uint64_t>(hi) << 32) | lo;
 118     return u.dval;
 119 }
 120
 121 static void Double2Ints(double val, uint32_t& lo, uint32_t& hi)
 122 {
 123     union {
 124         double dval;
 125         uint64_t ival64;
 126     } u;
 127     u.dval = val;
 128     hi = static_cast<uint32_t>(u.ival64 >> 32);
 129     lo = static_cast<uint32_t>(u.ival64);
 130 }
 131 #endif // USE(JSVALUE32_64)
 132
 133 } // namespace LLint
 134
 135
 136 //============================================================================
 137 // CLoopRegister is the storage for an emulated CPU register.
 138 // It defines the policy of how ints smaller than intptr_t are packed into the
 139 // pseudo register, as well as hides endianness differences.
 140
 141 struct CLoopRegister {
 142     union {
 143         intptr_t i;
 144         uintptr_t u;
 145 #if USE(JSVALUE64)
 146 #if CPU(BIG_ENDIAN)
 147         struct {
 148             int32_t i32padding;
 149             int32_t i32;
 150         };
 151         struct {
 152             uint32_t u32padding;
 153             uint32_t u32;
 154         };
 155         struct {
 156             int8_t i8padding[7];
 157             int8_t i8;
 158         };
 159         struct {
 160             uint8_t u8padding[7];
 161             uint8_t u8;
 162         };
 163 #else // !CPU(BIG_ENDIAN)
 164         struct {
 165             int32_t i32;
 166             int32_t i32padding;
 167         };
 168         struct {
 169             uint32_t u32;
 170             uint32_t u32padding;
 171         };
 172         struct {
 173             int8_t i8;
 174             int8_t i8padding[7];
 175         };
 176         struct {
 177             uint8_t u8;
 178             uint8_t u8padding[7];
 179         };
 180 #endif // !CPU(BIG_ENDIAN)
 181 #else // !USE(JSVALUE64)
 182         int32_t i32;
 183         uint32_t u32;
 184
 185 #if CPU(BIG_ENDIAN)
 186         struct {
 187             int8_t i8padding[3];
 188             int8_t i8;
 189         };
 190         struct {
 191             uint8_t u8padding[3];
 192             uint8_t u8;
 193         };
 194
 195 #else // !CPU(BIG_ENDIAN)
 196         struct {
 197             int8_t i8;
 198             int8_t i8padding[3];
 199         };
 200         struct {
 201             uint8_t u8;
 202             uint8_t u8padding[3];
 203         };
 204 #endif // !CPU(BIG_ENDIAN)
 205 #endif // !USE(JSVALUE64)
 206
 207         int8_t* i8p;
 208         void* vp;
 209         ExecState* execState;
 210         void* instruction;
 211         NativeFunction nativeFunc;
 212 #if USE(JSVALUE64)
 213         int64_t i64;
 214         uint64_t u64;
 215         EncodedJSValue encodedJSValue;
 216         double castToDouble;
 217 #endif
 218         Opcode opcode;
 219     };
 220
 221 #if USE(JSVALUE64)
 222     inline void clearHighWord() { i32padding = 0; }
 223 #else
 224     inline void clearHighWord() { }
 225 #endif
 226 };
 227
 228 //============================================================================
 229 // The llint C++ interpreter loop:
 230 //
 231
 232 JSValue CLoop::execute(CallFrame* callFrame, OpcodeID bootstrapOpcodeId,
 233                        bool isInitializationPass)
 234 {
 235     #define CAST reinterpret_cast
 236     #define SIGN_BIT32(x) ((x) & 0x80000000)
 237
 238     // One-time initialization of our address tables. We have to put this code
 239     // here because our labels are only in scope inside this function. The
 240     // caller (or one of its ancestors) is responsible for ensuring that this
 241     // is only called once during the initialization of the VM before threads
 242     // are at play.
 243     if (UNLIKELY(isInitializationPass)) {
 244 #if ENABLE(COMPUTED_GOTO_OPCODES)
 245         Opcode* opcodeMap = LLInt::opcodeMap();
 246         #define OPCODE_ENTRY(__opcode, length) \
 247             opcodeMap[__opcode] = bitwise_cast<void*>(&&__opcode);
 248         FOR_EACH_OPCODE_ID(OPCODE_ENTRY)
 249         #undef OPCODE_ENTRY
 250
 251         #define LLINT_OPCODE_ENTRY(__opcode, length) \
 252             opcodeMap[__opcode] = bitwise_cast<void*>(&&__opcode);
 253
 254         FOR_EACH_LLINT_NATIVE_HELPER(LLINT_OPCODE_ENTRY)
 255         #undef LLINT_OPCODE_ENTRY
 256 #endif
 257         // Note: we can only set the exceptionInstructions after we have
 258         // initialized the opcodeMap above. This is because getCodePtr()
 259         // can depend on the opcodeMap.
 260         Instruction* exceptionInstructions = LLInt::exceptionInstructions();
 261         for (int i = 0; i < maxOpcodeLength + 1; ++i)
 262             exceptionInstructions[i].u.pointer =
 263                 LLInt::getCodePtr(llint_throw_from_slow_path_trampoline);
 264
 265         return JSValue();
 266     }
 267
 268     ASSERT(callFrame->vm().topCallFrame == callFrame);
 269
 270     // Define the pseudo registers used by the LLINT C Loop backend:
 271     ASSERT(sizeof(CLoopRegister) == sizeof(intptr_t));
 272
 273     union CLoopDoubleRegister {
 274         double d;
 275 #if USE(JSVALUE64)
 276         int64_t castToInt64;
 277 #endif
 278     };
 279
 280     // The CLoop llint backend is initially based on the ARMv7 backend, and
 281     // then further enhanced with a few instructions from the x86 backend to
 282     // support building for X64 targets. Hence, the shape of the generated
 283     // code and the usage convention of registers will look a lot like the
 284     // ARMv7 backend's.
 285     //
 286     // For example, on a 32-bit build:
 287     // 1. Outgoing args will be set up as follows:
 288     //    arg1 in t0 (r0 on ARM)
 289     //    arg2 in t1 (r1 on ARM)
 290     // 2. 32 bit return values will be in t0 (r0 on ARM).
 291     // 3. 64 bit return values (e.g. doubles) will be in t0,t1 (r0,r1 on ARM).
 292     //
 293     // But instead of naming these simulator registers based on their ARM
 294     // counterparts, we'll name them based on their original llint asm names.
 295     // This will make it easier to correlate the generated code with the
 296     // original llint asm code.
 297     //
 298     // On a 64-bit build, it more like x64 in that the registers are 64 bit.
 299     // Hence:
 300     // 1. Outgoing args are still the same: arg1 in t0, arg2 in t1, etc.
 301     // 2. 32 bit result values will be in the low 32-bit of t0.
 302     // 3. 64 bit result values will be in t0.
 303
 304     CLoopRegister t0, t1, t2, t3;
 305 #if USE(JSVALUE64)
 306     CLoopRegister rBasePC, tagTypeNumber, tagMask;
 307 #endif
 308     CLoopRegister rRetVPC;
 309     CLoopDoubleRegister d0, d1;
 310
 311     // Keep the compiler happy. We don't really need this, but the compiler
 312     // will complain. This makes the warning go away.
 313     t0.i = 0;
 314     t1.i = 0;
 315
 316     // Instantiate the pseudo JIT stack frame used by the LLINT C Loop backend:
 317     JITStackFrame jitStackFrame;
 318
 319     // The llint expects the native stack pointer, sp, to be pointing to the
 320     // jitStackFrame (which is the simulation of the native stack frame):
 321     JITStackFrame* const sp = &jitStackFrame;
 322     sp->vm = &callFrame->vm();
 323
 324     // Set up an alias for the vm ptr in the JITStackFrame:
 325     VM* &vm = sp->vm;
 326
 327     CodeBlock* codeBlock = callFrame->codeBlock();
 328     Instruction* vPC;
 329
 330     // rPC is an alias for vPC. Set up the alias:
 331     CLoopRegister& rPC = *CAST<CLoopRegister*>(&vPC);
 332
 333 #if USE(JSVALUE32_64)
 334     vPC = codeBlock->instructions().begin();
 335 #else // USE(JSVALUE64)
 336     vPC = 0;
 337     rBasePC.vp = codeBlock->instructions().begin();
 338
 339     // For the ASM llint, JITStubs takes care of this initialization. We do
 340     // it explicitly here for the C loop:
 341     tagTypeNumber.i = 0xFFFF000000000000;
 342     tagMask.i = 0xFFFF000000000002;
 343 #endif // USE(JSVALUE64)
 344
 345     // cfr is an alias for callFrame. Set up this alias:
 346     CLoopRegister& cfr = *CAST<CLoopRegister*>(&callFrame);
 347
 348     // Simulate a native return PC which should never be used:
 349     rRetVPC.i = 0xbbadbeef;
 350
 351     // Interpreter variables for value passing between opcodes and/or helpers:
 352     NativeFunction nativeFunc = 0;
 353     JSValue functionReturnValue;
 354     Opcode opcode;
 355
 356     opcode = LLInt::getOpcode(bootstrapOpcodeId);
 357
 358     #if ENABLE(OPCODE_STATS)
 359         #define RECORD_OPCODE_STATS(__opcode) \
 360             OpcodeStats::recordInstruction(__opcode)
 361     #else
 362         #define RECORD_OPCODE_STATS(__opcode)
 363     #endif
 364
 365     #if USE(JSVALUE32_64)
 366         #define FETCH_OPCODE() vPC->u.opcode
 367     #else // USE(JSVALUE64)
 368         #define FETCH_OPCODE() *bitwise_cast<Opcode*>(rBasePC.i8p + rPC.i * 8)
 369     #endif // USE(JSVALUE64)
 370
 371     #define NEXT_INSTRUCTION() \
 372         do {                         \
 373             opcode = FETCH_OPCODE(); \
 374             DISPATCH_OPCODE();       \
 375         } while (false)
 376
 377 #if ENABLE(COMPUTED_GOTO_OPCODES)
 378
 379     //========================================================================
 380     // Loop dispatch mechanism using computed goto statements:
 381
 382     #define DISPATCH_OPCODE() goto *opcode
 383
 384     #define DEFINE_OPCODE(__opcode) \
 385         __opcode: \
 386             RECORD_OPCODE_STATS(__opcode);
 387
 388     // Dispatch to the current PC's bytecode:
 389     DISPATCH_OPCODE();
 390
 391 #else // !ENABLE(COMPUTED_GOTO_OPCODES)
 392     //========================================================================
 393     // Loop dispatch mechanism using a C switch statement:
 394
 395     #define DISPATCH_OPCODE() goto dispatchOpcode
 396
 397     #define DEFINE_OPCODE(__opcode) \
 398         case __opcode: \
 399         __opcode: \
 400             RECORD_OPCODE_STATS(__opcode);
 401
 402     // Dispatch to the current PC's bytecode:
 403     dispatchOpcode:
 404     switch (opcode)
 405
 406 #endif // !ENABLE(COMPUTED_GOTO_OPCODES)
 407
 408     //========================================================================
 409     // Bytecode handlers:
 410     {
 411         // This is the file generated by offlineasm, which contains all of the
 412         // bytecode handlers for the interpreter, as compiled from
 413         // LowLevelInterpreter.asm and its peers.
 414
 415         #include "LLIntAssembly.h"
 416
 417         // In the ASM llint, getHostCallReturnValue() is a piece of glue
 418         // function provided by the JIT (see dfg/DFGOperations.cpp).
 419         // We simulate it here with a pseduo-opcode handler.
 420         OFFLINE_ASM_GLUE_LABEL(getHostCallReturnValue)
 421         {
 422             // The ASM part pops the frame:
 423             callFrame = callFrame->callerFrame();
 424
 425             // The part in getHostCallReturnValueWithExecState():
 426             JSValue result = vm->hostCallReturnValue;
 427 #if USE(JSVALUE32_64)
 428             t1.i = result.tag();
 429             t0.i = result.payload();
 430 #else
 431             t0.encodedJSValue = JSValue::encode(result);
 432 #endif
 433             goto doReturnHelper;
 434         }
 435
 436         OFFLINE_ASM_GLUE_LABEL(ctiOpThrowNotCaught)
 437         {
 438             return vm->exception;
 439         }
 440
 441 #if !ENABLE(COMPUTED_GOTO_OPCODES)
 442     default:
 443         ASSERT(false);
 444 #endif
 445
 446     } // END bytecode handler cases.
 447
 448     //========================================================================
 449     // Bytecode helpers:
 450
 451     doReturnHelper: {
 452         ASSERT(!!callFrame);
 453         if (callFrame->hasHostCallFrameFlag()) {
 454 #if USE(JSVALUE32_64)
 455             return JSValue(t1.i, t0.i); // returning JSValue(tag, payload);
 456 #else
 457             return JSValue::decode(t0.encodedJSValue);
 458 #endif
 459         }
 460
 461         // The normal ASM llint call implementation returns to the caller as
 462         // recorded in rRetVPC, and the caller would fetch the return address
 463         // from ArgumentCount.tag() (see the dispatchAfterCall() macro used in
 464         // the callTargetFunction() macro in the llint asm files).
 465         //
 466         // For the C loop, we don't have the JIT stub to this work for us.
 467         // So, we need to implement the equivalent of dispatchAfterCall() here
 468         // before dispatching to the PC.
 469
 470         vPC = callFrame->currentVPC();
 471
 472 #if USE(JSVALUE64)
 473         // Based on LowLevelInterpreter64.asm's dispatchAfterCall():
 474
 475         // When returning from a native trampoline call, unlike the assembly
 476         // LLInt, we can't simply return to the caller. In our case, we grab
 477         // the caller's VPC and resume execution there. However, the caller's
 478         // VPC returned by callFrame->currentVPC() is in the form of the real
 479         // address of the target bytecode, but the 64-bit llint expects the
 480         // VPC to be a bytecode offset. Hence, we need to map it back to a
 481         // bytecode offset before we dispatch via the usual dispatch mechanism
 482         // i.e. NEXT_INSTRUCTION():
 483
 484         codeBlock = callFrame->codeBlock();
 485         ASSERT(codeBlock);
 486         rPC.vp = callFrame->currentVPC();
 487         rPC.i = rPC.i8p - reinterpret_cast<int8_t*>(codeBlock->instructions().begin());
 488         rPC.i >>= 3;
 489
 490         rBasePC.vp = codeBlock->instructions().begin();
 491 #endif // USE(JSVALUE64)
 492
 493         NEXT_INSTRUCTION();
 494
 495     } // END doReturnHelper.
 496
 497
 498     // Keep the compiler happy so that it doesn't complain about unused
 499     // labels for the LLInt trampoline glue. The labels are automatically
 500     // emitted by label macros above, and some of them are referenced by
 501     // the llint generated code. Since we can't tell ahead of time which
 502     // will be referenced and which will be not, we'll just passify the
 503     // compiler on all such labels:
 504     #define LLINT_OPCODE_ENTRY(__opcode, length) \
 505         UNUSED_LABEL(__opcode);
 506         FOR_EACH_OPCODE_ID(LLINT_OPCODE_ENTRY);
 507     #undef LLINT_OPCODE_ENTRY
 508
 509
 510     #undef NEXT_INSTRUCTION
 511     #undef DEFINE_OPCODE
 512     #undef CHECK_FOR_TIMEOUT
 513     #undef CAST
 514     #undef SIGN_BIT32
 515
 516 } // Interpreter::llintCLoopExecute()
 517
 518 } // namespace JSC
 519
 520 #else // !ENABLE(LLINT_C_LOOP)
 521
 522 //============================================================================
 523 // Define the opcode dispatch mechanism when using an ASM loop:
 524 //
 525
 526 // These are for building an interpreter from generated assembly code:
 527 #define OFFLINE_ASM_BEGIN   asm (
 528 #define OFFLINE_ASM_END     );
 529
 530 #define OFFLINE_ASM_OPCODE_LABEL(__opcode) OFFLINE_ASM_GLOBAL_LABEL(llint_##__opcode)
 531 #define OFFLINE_ASM_GLUE_LABEL(__opcode)   OFFLINE_ASM_GLOBAL_LABEL(__opcode)
 532
 533 #if CPU(ARM_THUMB2)
 534 #define OFFLINE_ASM_GLOBAL_LABEL(label)          \
 535     ".globl " SYMBOL_STRING(label) "\n"          \
 536     HIDE_SYMBOL(label) "\n"                      \
 537     ".thumb\n"                                   \
 538     ".thumb_func " THUMB_FUNC_PARAM(label) "\n"  \
 539     SYMBOL_STRING(label) ":\n"
 540 #else
 541 #define OFFLINE_ASM_GLOBAL_LABEL(label)         \
 542     ".globl " SYMBOL_STRING(label) "\n"         \
 543     HIDE_SYMBOL(label) "\n"                     \
 544     SYMBOL_STRING(label) ":\n"
 545 #endif
 546
 547 #define OFFLINE_ASM_LOCAL_LABEL(label)   LOCAL_LABEL_STRING(label) ":\n"
 548
 549 // This is a file generated by offlineasm, which contains all of the assembly code
 550 // for the interpreter, as compiled from LowLevelInterpreter.asm.
 551 #include "LLIntAssembly.h"
 552
 553 #endif // !ENABLE(LLINT_C_LOOP)
 554
 555 #endif // ENABLE(LLINT)