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PerformanceAwareProgramming/part1/sim8086.c

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C
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#define WIN32_MEAN_AND_LEAN
#define NOMINMAX
#include <Windows.h>
#include <stdint.h>
#include <stdio.h>
#include <stdarg.h>
#include <stdbool.h>
typedef struct S86_Buffer S86_Buffer;
struct S86_Buffer {
char *data;
size_t size;
};
typedef struct S86_Str8 S86_Str8;
struct S86_Str8 {
char *data;
size_t size;
};
typedef struct S86_Globals S86_Globals;
struct S86_Globals {
HANDLE stdout_handle;
bool write_to_console;
};
S86_Globals s86_globals;
#define S86_STRINGIFY2(token) #token
#define S86_STRINGIFY(token) S86_STRINGIFY2(token)
#define S86_ASSERT(expr) \
if (!(expr)) { \
S86_PrintLnFmt("Assertion triggered [file=" __FILE__ ", line=" S86_STRINGIFY(__LINE__) ", expr=" #expr "]"); \
__debugbreak(); \
} \
#define S86_ARRAY_UCOUNT(array) sizeof((array)) / sizeof((array)[0])
#define S86_STR8(string) (S86_Str8){.data = (string), .size = S86_ARRAY_UCOUNT(string) - 1 }
#define S86_STR8_FMT(string) (int)((string).size), (string).data
#define S86_CAST(Type) (Type)
S86_Buffer S86_ReadFile(char const *file_path);
void S86_PrintLn(S86_Str8 string);
void S86_PrintLnFmt(char const *fmt, ...);
S86_Buffer S86_ReadFile(char const *file_path)
{
S86_Buffer result = {0};
// NOTE: Determine file size
// =========================================================================
WIN32_FILE_ATTRIBUTE_DATA file_attrib_data = {0};
if (GetFileAttributesEx(file_path, GetFileExInfoStandard, &file_attrib_data) == 0)
return result;
// NOTE: Open file
// =========================================================================
HANDLE file_handle = CreateFile(
/*LPCSTR lpFileName*/ file_path,
/*DWORD dwDesiredAccess*/ GENERIC_READ,
/*DWORD dwShareMode*/ 0,
/*LPSECURITY_ATTRIBUTES lpSecurityAttributes*/ NULL,
/*DWORD dwCreationDisposition*/ OPEN_EXISTING,
/*DWORD dwFlagsAndAttributes*/ 0,
/*HANDLE hTemplateFile*/ NULL
);
if (file_handle == INVALID_HANDLE_VALUE)
return result;
// NOTE: Allocate buffer
// =========================================================================
uint64_t file_size = (uint64_t)file_attrib_data.nFileSizeHigh << 32 | (uint64_t)file_attrib_data.nFileSizeLow << 0;
S86_ASSERT(file_size < (DWORD)-1);
char *buffer = VirtualAlloc(
/*LPVOID lpAddress*/ NULL,
/*SIZE_T dwSize*/ file_size,
/*DWORD flAllocationType*/ MEM_COMMIT | MEM_RESERVE,
/*DWORD flProtect*/ PAGE_READWRITE
);
if (!buffer)
goto end;
// NOTE: Read file to buffer
// =========================================================================
DWORD bytes_read = 0;
BOOL read_file_result = ReadFile(
/*HANDLE hFile*/ file_handle,
/*LPVOID lpBuffer*/ buffer,
/*DWORD nNumberOfBytesToRead*/ S86_CAST(DWORD)file_size,
/*LPDWORD lpNumberOfBytesRead*/ &bytes_read,
/*LPOVERLAPPED lpOverlapped*/ NULL
);
// NOTE: Handle read result
// =========================================================================
if (read_file_result == 0) {
VirtualFree(buffer, 0, MEM_RELEASE);
} else {
result.data = buffer;
result.size = file_size;
}
end:
CloseHandle(file_handle);
return result;
};
bool S86_BufferIsValid(S86_Buffer buffer)
{
bool result = buffer.data && buffer.size;
return result;
}
void S86_PrintLn(S86_Str8 string)
{
if (s86_globals.stdout_handle == NULL) {
s86_globals.stdout_handle = GetStdHandle(STD_OUTPUT_HANDLE);
DWORD mode = 0;
BOOL get_console_mode_result = GetConsoleMode(
/*HANDLE hConsoleHandle*/ s86_globals.stdout_handle,
/*LPDWORD lpMode*/ &mode
);
s86_globals.write_to_console = get_console_mode_result != 0;
}
S86_ASSERT(string.size < S86_CAST(DWORD)-1);
if (s86_globals.write_to_console) {
DWORD chars_written = 0;
WriteConsoleA(s86_globals.stdout_handle, string.data, (DWORD)string.size, &chars_written, NULL);
WriteConsoleA(s86_globals.stdout_handle, "\n", 1, &chars_written, NULL);
} else {
DWORD bytes_written = 0;
WriteFile(s86_globals.stdout_handle, string.data, (DWORD)string.size, &bytes_written, NULL);
WriteFile(s86_globals.stdout_handle, "\n", 1, &bytes_written, NULL);
}
}
void S86_PrintLnFmt(char const *fmt, ...)
{
va_list args, args_copy;
va_start(args, fmt);
va_copy(args_copy, args);
int string_size = vsnprintf(NULL, 0, fmt, args_copy);
va_end(args_copy);
char buffer[8192];
S86_ASSERT(string_size >= 0 && string_size < S86_ARRAY_UCOUNT(buffer));
if (string_size) {
vsnprintf(buffer, sizeof(buffer), fmt, args);
S86_Str8 string = {.data = buffer, .size = string_size};
S86_PrintLn(string);
}
va_end(args);
}
typedef enum S86_ModEncoding S86_ModEncoding;
enum S86_ModEncoding {
S86_ModEncoding_MemModeNoDisplace = 0b00,
S86_ModEncoding_MemMode8 = 0b01,
S86_ModEncoding_MemMode16 = 0b10,
S86_ModEncoding_RegisterMode = 0b11,
};
typedef enum S86_InstructionType S86_InstructionType;
enum S86_InstructionType {
S86_InstructionType_MOVRegOrMemToOrFromReg,
S86_InstructionType_MOVImmediateToRegOrMem,
S86_InstructionType_MOVImmediateToReg,
S86_InstructionType_MOVMemToAccum,
S86_InstructionType_MOVAccumToMem,
S86_InstructionType_MOVRegOrMemToSegReg,
S86_InstructionType_MOVSegRegToRegOrMem,
S86_InstructionType_Count,
};
typedef struct S86_Instruction S86_Instruction;
struct S86_Instruction {
uint16_t op_mask;
uint16_t op_bits;
} S86_INSTRUCTIONS[S86_InstructionType_Count] = {
[S86_InstructionType_MOVRegOrMemToOrFromReg] = {.op_mask = 0b1111'1100'0000'0000,
.op_bits = 0b1000'1000'0000'0000},
[S86_InstructionType_MOVImmediateToRegOrMem] = {.op_mask = 0b1111'1110'0011'1000,
.op_bits = 0b1100'0110'0000'0000},
[S86_InstructionType_MOVImmediateToReg] = {.op_mask = 0b1111'0000'0000'0000,
.op_bits = 0b1011'0000'0000'0000},
[S86_InstructionType_MOVMemToAccum] = {.op_mask = 0b1111'1110'0000'0000,
.op_bits = 0b1010'0000'0000'0000},
[S86_InstructionType_MOVAccumToMem] = {.op_mask = 0b1111'1110'0000'0000,
.op_bits = 0b1010'0010'0000'0000},
[S86_InstructionType_MOVRegOrMemToSegReg] = {.op_mask = 0b1111'1111'0010'0000,
.op_bits = 0b1000'1110'0000'0000},
[S86_InstructionType_MOVSegRegToRegOrMem] = {.op_mask = 0b1111'1111'0010'0000,
.op_bits = 0b1000'1100'0000'0000},
};
typedef enum S86_OpDataSize S86_OpDataSize;
enum S86_OpDataSize { S86_OpDataSize_Byte, S86_OpDataSize_Word };
int main(int argc, char **argv)
{
if (argc != 2) {
S86_PrintLn(S86_STR8("usage: sim8086.exe <binary asm file>"));
return -1;
}
S86_Str8 const REGISTER_FIELD_ENCODING[2][8] = {
[0b0] =
{
S86_STR8("al"),
S86_STR8("cl"),
S86_STR8("dl"),
S86_STR8("bl"),
S86_STR8("ah"),
S86_STR8("ch"),
S86_STR8("dh"),
S86_STR8("bh"),
},
[0b1] =
{
S86_STR8("ax"),
S86_STR8("cx"),
S86_STR8("dx"),
S86_STR8("bx"),
S86_STR8("sp"),
S86_STR8("bp"),
S86_STR8("si"),
S86_STR8("di"),
},
};
char const *file_path = argv[1];
S86_Buffer buffer = S86_ReadFile(file_path);
if (!S86_BufferIsValid(buffer)) {
S86_PrintLnFmt("File read failed [path=\"%s\"]", argv[1], buffer.size);
return -1;
}
S86_PrintLn(S86_STR8("bits 16"));
S86_ASSERT(buffer.size % 2 == 0); // We expect 2 byte instructions
for (size_t buffer_index = 0; buffer_index < (buffer.size / 2); buffer_index++) {
uint8_t byte0 = (uint8_t)buffer.data[buffer_index + 0];
uint8_t byte1 = (uint8_t)buffer.data[buffer_index + 1];
uint16_t byte01 = (uint16_t)byte0 << 8 | (uint16_t)byte1 << 0;
for (size_t instruction_index = 0;
instruction_index < S86_ARRAY_UCOUNT(S86_INSTRUCTIONS);
instruction_index++)
{
S86_Instruction instruction = S86_INSTRUCTIONS[instruction_index];
if ((byte01 & instruction.op_mask) != instruction.op_bits)
continue;
S86_InstructionType type = S86_CAST(S86_InstructionType)instruction_index;
switch (type) {
case S86_InstructionType_MOVRegOrMemToOrFromReg: {
uint8_t d = (byte0 & 0b0000'0010) >> 1;
uint8_t w = (byte0 & 0b0000'0001) >> 0;
uint8_t mod = (byte1 & 0b1100'0000) >> 6;
uint8_t reg = (byte1 & 0b0011'1000) >> 3;
uint8_t rm = (byte1 & 0b0000'0111) >> 0;
S86_ASSERT(d < 2);
S86_ASSERT(w < 2);
S86_ASSERT(mod < 4);
S86_ASSERT(reg < 8);
S86_ASSERT(rm < 8);
uint8_t instr_dest = d ? reg : rm;
uint8_t instr_src = d ? rm : reg;
// S86_OpDataSize data_size = w ? S86_OpDataSize_Word : S86_OpDataSize_Byte;
S86_ASSERT(mod == 0b11); // register-to-register
S86_Str8 src_register = REGISTER_FIELD_ENCODING[w][instr_src];
S86_Str8 dest_register = REGISTER_FIELD_ENCODING[w][instr_dest];
S86_PrintLnFmt("mov %.*s, %.*s", S86_STR8_FMT(dest_register), S86_STR8_FMT(src_register));
#if 0
if (mod == 0b01) {
// 8 bit displacement
} else if (mode == 0b10) {
// 16 bit displacement
}
#endif
} break;
case S86_InstructionType_MOVImmediateToRegOrMem: {
} break;
case S86_InstructionType_MOVImmediateToReg: {
} break;
case S86_InstructionType_MOVMemToAccum: {
} break;
case S86_InstructionType_MOVAccumToMem: {
} break;
case S86_InstructionType_MOVRegOrMemToSegReg: {
} break;
case S86_InstructionType_MOVSegRegToRegOrMem: {
} break;
default: {
S86_ASSERT(!"Unknown instruction");
} break;
}
}
}
}
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