C++ emitCode函数代码示例

void term() {
    // assert: n = allocatedRegisters

    // remember operator symbol
    // must be local variable to work for nested expressions
    int operatorSymbol;

    factor();

    // assert: allocatedRegisters == n + 1

    while (isSymbolAsteriskOrSlash()) {
        operatorSymbol = symbol;
        getSymbol();

        term();

        if (operatorSymbol == ASTERISK)
            emitCode(MUL, allocatedRegisters - 1, allocatedRegisters - 1, allocatedRegisters);
        else
            emitCode(DIV, allocatedRegisters - 1, allocatedRegisters - 1, allocatedRegisters);

        allocatedRegisters = allocatedRegisters - 1;
    }

    // assert: allocatedRegisters == n + 1
}

static void parse_finish_branch (git_uint32* pc, Label op, LoadReg reg, int mode)
{
    git_sint32 val;
    if (parseLoad (pc, reg, mode, size32, &val))
    {
        // The branch offset is a constant, so we can
        // check for the special values 0 and 1 right here.
        
        if (val == 0)
        {
            emitCode (op - label_jeq_var + label_jeq_return0);
        }
        else if (val == 1)
        {
            emitCode (op - label_jeq_var + label_jeq_return1);
        }
        else
        {
            // Calculate the destination address and
            // emit a constant branch opcode.
            emitConstBranch (op - label_jeq_var + label_jeq_const, *pc + val - 2);
        }
    }
    else
    {
        // The branch offset isn't a constant, so just
        // emit the normal opcode plus the current PC.
        
        emitCode (op);
        emitData(*pc);
    }
}

void emitExit() {
    int* identifierCursor;

    // "exit" is 4 characters plus null termination
    identifier = malloc(5 * 4);

    identifierCursor = identifier;

    *identifierCursor = 101; // ASCII code 101 = e
    identifierCursor = identifierCursor + 1;
    *identifierCursor = 120; // ASCII code 120 = x
    identifierCursor = identifierCursor + 1;
    *identifierCursor = 105; // ASCII code 105 = i
    identifierCursor = identifierCursor + 1;
    *identifierCursor = 116; // ASCII code 116 = t
    identifierCursor = identifierCursor + 1;
    *identifierCursor = 0; // end of identifier

    // current code length is address of next instruction
    createSymbolTableEntry(codeLength);

    // retrieve error code from stack into register 1
    emitCode(LDW, 1, SP, 0);

    // halt machine, return error code from register 1
    emitCode(HLT, 0, 0, 1);
}

//int main() {  this causes a name collision when hosted on linux...
int parser_main() {
    // pick some maximum identifier length, e.g. 42 characters
    maxIdentifierLength = 42;

    LINK = 31;
    SP = 30;
    FP = 29;
    GP = 28;
    RR = 27;
    // ...

    ZR = 0;

    allocatedRegisters = 0;
    allocatedGlobalVariables = 0;

    ADD = 7; // opcode for ADD
    SUB = 8; // opcode for SUB
    // ...

    symbolTable = 0;

    // pick some maximum code length, e.g. 16K * 4 bytes = 64KB
    // increase as needed
    maxCodeLength = 16384;

    // allocate memory for emitting code
    code = malloc(maxCodeLength * 4);
    codeLength = 0;

    // start executing by branching to main procedure
    // please do not forget: parameter c requires fixup
    // when code location for main procedure is known
    emitCode(BSR, 0, 0, 0);

    // push exit code in return register onto stack
    emitCode(PSH, RR, SP, 4);

    // halt machine by invoking exit
    emitCode(BSR, 0, 0, codeLength + 1);

    // emit library code for exit right here
    emitExit();

    // similarly, emit library code for malloc, getchar, and putchar
    // ...

    // get first symbol from scanner
    getSymbol();

    // invoke compiler, implement missing procedures
    cstar();

    // write code to standard output
    writeBinary();

    return 0;
}

void factor() {
	int symbol;
    // assert: n = allocatedRegisters

    // have we parsed an asterisk sign?
    // must be local variable to work for nested expressions
    int dereference;

    cast();

    if (symbol == ASTERISK) {
        dereference = 1;

        getSymbol();
    } else
        dereference = 0;

    if (symbol == IDENTIFIER) {
        allocatedRegisters = allocatedRegisters + 1;

        emitCode(LDW, allocatedRegisters, GP, getGlobalVariableOffset());

        getSymbol();
    } else if (symbol == INTEGER) {
        allocatedRegisters = allocatedRegisters + 1;

        emitCode(ADDI, allocatedRegisters, ZR, integer);

        getSymbol();
    } else if (symbol == LEFTPARENTHESIS) {
        getSymbol();

        expression();

        if (symbol == RIGHTPARENTHESIS)
            getSymbol();
        else
            syntaxError(FACTOR); // right parenthesis expected!
    } else
        syntaxError(FACTOR); // identifier, integer, or left parenthesis expected!

    if (dereference)
        emitCode(LDW, allocatedRegisters, allocatedRegisters, 0);

    // assert: allocatedRegisters == n + 1
}

int expression() {
	int symbol;
    // assert: n = allocatedRegisters

    // have we parsed a minus sign?
    // must be local variable to work for nested expressions
    int sign;

    // remember operator symbol
    // must be local variable to work for nested expressions
    int operatorSymbol;

    if (symbol == MINUS) {
        sign = 1;

        getSymbol();
    } else
        sign = 0;

    term();

    // assert: allocatedRegisters == n + 1

    if (sign)
        emitCode(SUB, allocatedRegisters, ZR, allocatedRegisters);

    while (isSymbolPlusOrMinus()) {
        operatorSymbol = symbol;
        getSymbol();

        term();

        if (operatorSymbol == PLUS)
            emitCode(ADD, allocatedRegisters - 1, allocatedRegisters - 1, allocatedRegisters);
        else
            emitCode(SUB, allocatedRegisters - 1, allocatedRegisters - 1, allocatedRegisters);

        allocatedRegisters = allocatedRegisters - 1;
    }

    // assert: allocatedRegisters == n + 1

    // enhance to return BEQ, BNE, etc.
    // depending on parsed comparison operator
    return 0;
}

static void emit_insn2(int64_t oc)
{
     emitCode(oc & 255);
     emitCode((oc >> 8) & 255);
     emitCode((oc >> 16) & 255);
     emitCode((oc >> 24) & 255);
     emitCode((oc >> 32) & 255);
}

static void parseL (git_uint32* pc, Label op)
{
    int modes [1];
    parseModeNibbles (pc, 1, modes);

    parseLoad (pc, reg_L1, modes [0], size32, NULL);
    emitCode (op);
}

static void parseS (git_uint32* pc, Label op)
{
    int modes [1];
    parseModeNibbles (pc, 1, modes);

    emitCode (op);
    parseStore (pc, reg_S1, modes [0], size32);
}

static void parseLS (git_uint32* pc, Label op)
{
    int modes [2];
    parseModeNibbles (pc, 2, modes);

    parseLoad (pc, reg_L1, modes [0], size32, NULL);
    emitCode (op);
    parseStore (pc, reg_S1, modes [1], size32);
}

static void emitImm0(int64_t v, int force)
{
     if (v != 0 || force) {
          emitAlignedCode(0xfd);
          emitCode(v & 255);
          emitCode((v >> 8) & 255);
          emitCode((v >> 16) & 255);
          emitCode((v >> 24) & 255);
     }

void test_emitCode_given_index_257_should_translate_to_nan_and_output_nan(){
  Dictionary *dictionary = dictionaryNew(100);
  dictionary->entries[1].code = "nan";
  OutStream out;
  int index = 257;
  
  streamWriteBits_Expect(&out, 110, 8);
  streamWriteBits_Expect(&out, 97, 8);
  streamWriteBits_Expect(&out, 110, 8);
  
  emitCode(dictionary, index, &out);
}

void test_emitCode_given_index_neg_1_should_throw_error(){
  CEXCEPTION_T e;
  Dictionary *dictionary = dictionaryNew(100);
  OutStream out;
  int index = -1;
  
  Try{
    emitCode(dictionary, index, &out);
  }Catch(e){
    TEST_ASSERT_EQUAL(ERR_INVALID_INDEX, e);
  }
}

/*
 * DoEmitCode - build callback routine thunk
 */
static CALLBACKPTR DoEmitCode( int argcnt, int bytecnt, char *array,
                               DWORD fn, int is_cdecl )
{
    int codesize;
    int i;

    /*
     * get a callback jump table entry
     */
    for( i = 0; i < MAX_CB_JUMPTABLE; i++ ) {
        if( _CBJumpTable[i] == 0L ) {
            break;
        }
    }
    if( i == MAX_CB_JUMPTABLE ) {
        return( NULL );
    }

    /*
     * build the callback code
     */
    emitWhere = NULL;
    codesize = emitCode( argcnt, bytecnt, array, fn, is_cdecl );
    emitWhere = malloc( codesize );
    if( emitWhere == NULL ) {
        return( NULL );
    }
    emitCode( argcnt, bytecnt, array, fn, is_cdecl );

    /*
     * set up the callback jump table, and return the proper callback rtn
     */
    _CBJumpTable[i] = (DWORD)emitWhere  - *_DataSelectorBaseAddr
                      + *_CodeSelectorBaseAddr;
    _CBRefsTable[i]++;  /* increase reference count */
    if( i > MaxCBIndex )  MaxCBIndex = i;
    *__32BitCallBackAddr = (FARPROCx)&__32BitCallBack;
    return( (char *)__16BitCallBackAddr - (i+1) * CB_CODE_SIZE );

} /* DoEmitCode */

void test_emitCode_given_index_97_should_translate_to_a_and_output_a(){
  CEXCEPTION_T e;
  Dictionary *dictionary = dictionaryNew(100);
  OutStream out;
  int index = 97;
  
  streamWriteBits_Expect(&out, 97, 8);
  
  Try{
    emitCode(dictionary, index, &out);
  }Catch(e){
    TEST_ASSERT_EQUAL(ERR_EXCEEDING_DICTIONARY_SIZE, e);
  }
}