codegen.h

PL/0源码

//////////////////////////////////////////////////////////////////////////////
//
//  codegen.[h,cc] -- naive code generation
//

#ifndef CODEGEN_H
#define CODEGEN_H

#include <fstream>

#define FIRST_REG   0
#define LAST_REG    31

typedef unsigned mips_register_t;               // FIRST_REG..LAST_REG
typedef char mips_name_t[8];
typedef enum mips_location_t {
    R_UNKNOWN,                  // Data isn't anywhere
    R_REGISTER,                 // Data is in a register
    R_NUMBER,                   // Data is to be inlined as a number
    R_OFFSET,                   // Data is at an offset from a register
    R_LABEL                     // Data is global and has a label
};

////////
// extra fields of a syntax tree record, used only for code generation
//
struct syntax_code_t {
    mips_register_t     result_register;        // used for expressions
    mips_location_t     result_place;           // "
    int                 result_value;           // value if R_NUMBER
    unsigned            registers_used;         // set of mips_register_t
    // if we were doing optimization, this record could hold lots of other
    // things, such as def-use chains or live value sets
};

////////
// extra fields of a symbol table record, used only for code generation
//
class symbol_code_t {
public:
    mips_location_t     data_place;             // How to access data?
    union
    {
        mips_name_t     label;                  // Global label for data.
        struct
        {
            mips_register_t     reg;            // Register to offset from.
            int                 pos;            // Bytes from register to data.
        }               offset;
    }                   where;                  // Where to find data?
};

extern ofstream code;

void generate_code(const char * file_name);
//  Traverse abstract syntax tree and send output to file file_name.

#endif