jitvm.cxx

#include <cassert>
#include <sys/timeb.h>

#ifdef _WIN32
# include <windows.h>
#else
# include <sys/time.h>
# include <unistd.h>
#endif

#include <iostream>
#include <iomanip>

#include <map>
#include <limits>
#include <asmjit/asmjit.h>

#define HALT    0
#define SET    1
#define DEC     2
#define JUMP_NZ 3

using namespace std;
using namespace asmjit;

double time_s()
{
#if defined(_WIN32)
    struct __timeb64 time_struct;
    int64_t time_ms;
    _ftime64_s(&time_struct);
    time_ms = (int64_t)time_struct.time;
    time_ms *= 1000;
    time_ms += time_struct.millitm;
    return (time_ms / 1000.0);
#else
    struct timeval time_struct;
    int64_t time_ms;
    gettimeofday(&time_struct, 0);
    time_ms = (int64_t)time_struct.tv_sec;
    time_ms *= 1000;
    time_ms += (time_struct.tv_usec / 1000);
    return (time_ms / 1000.0);
#endif
}

void run_program(size_t* program, size_t program_len) {
    JitRuntime runtime;
    X86Assembler a(&runtime);
    X86Compiler c(&a);

    c.addFunc(FuncBuilder0<void>(kCallConvHost));

    map<size_t, Label> labels; // <addr, label>

    for (size_t i = 0; i < program_len; i++) {
        // collect labels
        if (program[i] == JUMP_NZ) {
            auto addr = program[i++ + 1];
            labels[addr] = c.newLabel();
        }
    }

    auto x = c.newInt64("x");
    for (size_t i = 0; i < program_len; i++) {
        // compile and bind
        {
            // Check whether there is a label for current position.
            auto addr = reinterpret_cast<size_t>(&program[i]);
            auto it = labels.find(addr);
            if (it != labels.end()) {
                // If we've found something then bind it.
                c.bind(it->second);
            }
        }

        // [SET x] operation
        if (program[i] == SET) {
            auto value = program[i++ + 1];
            c.mov(x, value);
            continue;
        }

        // [DEC x] operation
        if (program[i] == DEC) {
            c.dec(x);
            continue;
        }

        // [JUMP_NZ address] operation
        if (program[i] == JUMP_NZ) {
            size_t addr = program[i++ + 1];
            auto it = labels.find(addr);
            assert(it != labels.end());
            c.cmp(x, 0);
            c.jnz(it->second);
            continue;
        }

        // [HALT] operation
        if (program[i] == HALT) {
            c.ret();
            continue;
        }
    }

    // Finalize the building of instruction tree.
    c.endFunc();
    c.finalize();

    // Finally, compile code.
    typedef void(*FuncType)(void);
    auto compiled = asmjit_cast<FuncType>(a.make());

    // Run :)
    compiled();

    runtime.release((void*)compiled);
}

int main()
{
    size_t program[6];

    program[0] = SET;
    program[1] = 2000000000;
    program[2] = DEC;
    program[3] = JUMP_NZ;
    program[4] = (size_t)&program[2];
    program[5] = HALT;

    auto start_time = time_s();
    run_program(program, sizeof(program) / sizeof(size_t));
    auto end_time = time_s();

    cout << "JIT'ed code done in " << (end_time - start_time) << " seconds." << endl;

    return 0;
}