diff --git a/decode.c b/decode.c index 9ada796..d59d2ae 100644 --- a/decode.c +++ b/decode.c @@ -30,12 +30,6 @@ static char* reg_name(Register reg, char wide) return wide == 1 ? reg.fullname : reg.bytename; } -static i16 get_data(unsigned char* buf, char wide) -{ - // Cast buf[0] to sbyte if not the conversion to i16 won't detect signedness - return wide == 1 ? (i16)buf[1] << 8 | buf[0] : (sbyte)buf[0]; -} - static u8 mask_and_shift(u8 value, u8 mask) { value &= mask; @@ -101,9 +95,18 @@ ParsedInstruction parse_instruction(u8* buf) // This is a trick because mod == 1 and mod == 2 will displace one and two bytes // respectively but mod == 3 wraps to 0 since it doesn't displace if (fmt.has_displacement) idx += mod_opt.value % 3; - u16 data = w_opt.value != 0 ? (i16)buf[idx+1] << 8 | buf[idx] : (sbyte)buf[idx]; + u16 data; + if (fmt.has_s && s_opt.value == 1) + { + data = (sbyte)buf[idx]; + bytes_read += 1; + } + else + { + data = w_opt.value != 0 ? (i16)buf[idx+1] << 8 | buf[idx] : (sbyte)buf[idx]; + bytes_read += w_opt.value == 0 ? 1 : 2; + } data_opt = some_u16(data); - bytes_read += w_opt.value == 0 ? 1 : 2; } if (fmt.has_displacement && mod_opt.value % 3 > 0) { @@ -153,7 +156,8 @@ Instruction decode_instruction(ParsedInstruction inst) opr1.tag = OPR_T_IMMEDIATE; opr1.imm.value = inst.data.value; // TODO: This is dumb, we shouldn't do it this way - opr1.imm.direct = inst.w.value + 1; + if (inst.s.value == 1) opr1.imm.direct = 0; + else opr1.imm.direct = inst.w.value + 1; } if (mod == MODE_RGSTR_MODE) { @@ -247,159 +251,6 @@ void get_instr_string(char* str_buf, Instruction inst) sprintf(str_buf, "%s %s, %s", inst.operation, dst_str, src_str); } -bool mov_inst(FILE* f, unsigned char* buf, char inst) -{ - size_t bytes_read; - // Register/memory to/from register - if ((inst & ~0x3) == (char)0b10001000) - { - // TODO: We should add some form of error handling here - bytes_read = fread(buf, sizeof(char), 1, f); - char next_byte = buf[0]; - char w = inst & 0b00000001; - char d = (inst & 0b00000010) >> 1; - char mod = (next_byte & 0b11000000) >> 6; - char reg = (next_byte & 0b00111000) >> 3; - char rm = (next_byte & 0b00000111); - if (mod == MODE_RGSTR_MODE) - { - Register src_reg = d == 0 ? registers[(size_t)reg] : registers[(size_t)rm]; - Register dst_reg = d == 0 ? registers[(size_t)rm] : registers[(size_t)reg]; - printf("mov %s, %s ;0", reg_name(dst_reg, w), reg_name(src_reg, w)); - } - else - { - bool is_direct_addr = mod == 0 && rm == 0b110; - int bytes_to_read = is_direct_addr ? 2 : mod % 3; - bytes_read = fread(buf, sizeof(char), bytes_to_read, f); - char* eac_name = is_direct_addr ? "" : get_eac_register(rm); - char disp_buf[16] = {'\0'}; - if (bytes_to_read > 0) - { - i16 disp = get_data(buf, bytes_to_read - 1); - if (is_direct_addr) sprintf(disp_buf, "%d", abs(disp)); - else sprintf(disp_buf, " %s %d", disp >= 0 ? "+" : "-", abs(disp)); - } - Register rgstr = registers[(size_t)reg]; - if (d) printf("mov %s, [%s%s] ;1", reg_name(rgstr, w), eac_name, disp_buf); - else printf("mov [%s%s], %s ;2", eac_name, disp_buf, reg_name(rgstr, w)); - } - } - // Immediate to register/memory - else if ((inst & ~0x1) == (char)0b11000110) - { - bytes_read = fread(buf, sizeof(char), 1, f); - char w = inst & 0b00000001; - char mod = (buf[0] & 0b11000000) >> 6; - char rm = (buf[0] & 0b00000111); - int bytes_to_read = 1; - bytes_to_read += w == 0 ? 0 : 1; - // Same trick from earlier, see comment - bytes_to_read += mod % 3; - bytes_read = fread(buf, sizeof(char), bytes_to_read, f); - char *eac_name = get_eac_register(rm); - i16 data = get_data(buf + (char)bytes_to_read - (w == 0 ? 1 : 2), w); - char *word_str = w == 0 ? "byte" : "word"; - char disp_str[16] = {'\0'}; - if (mod % 3 > 1) sprintf(disp_str, " + %d", get_data(buf, (mod % 3) - 1)); - printf("mov [%s%s], %s %d ;3", eac_name, disp_str, word_str, data); - } - // Immediate to register - else if ((inst & ~0xF) == (char)0b10110000) - { - char w = (inst & 0b00001000) >> 3; - Register reg = registers[(size_t)inst & 0b00000111]; - char bytes_to_read = w == 1 ? 2 : 1; - bytes_read = fread(buf, sizeof(char), bytes_to_read, f); - printf("mov %s, %d ;4", reg_name(reg, w), get_data(buf, w)); - } - // Memory/accumulator to accumulator/memory - else if ((inst & ~0x3) == (char)0b10100000) - { - // This instruction uses AX/AL register exclusively - Register ax_al = registers[0]; - char w = (inst & 0b00000001); - // The manual doesn't refer to this as `d` but it acts similarly in that this bit - // swaps the accumulator's src/dst position - char d = (inst & 0b00000010) >> 1; - char bytes_to_read = w == 1 ? 2 : 1; - bytes_read = fread(buf, sizeof(char), bytes_to_read, f); - if (d) printf("mov [%d], %s ;5", get_data(buf, w), reg_name(ax_al, w)); - else printf("mov %s, [%d] ;6", reg_name(ax_al, w), get_data(buf, w)); - } - // Register/memory to segment register or segment register to register/memory - else if ((inst & ~0x3) == (char)0b10001100) - { - // Manual doesn't refer to this as `d` but swaps like in the previous instruction - char d = (inst & 0b00000010) >> 1; - (void)d; - printf("mov regmem to segreg"); - } - else - { - return false; - } - return bytes_read > 0; -} - -bool add_inst(FILE* f, unsigned char* buf, char inst) -{ - size_t bytes_read; - if ((inst & ~0x3) == (char)0b00000000) - { - bytes_read = fread(buf, sizeof(char), 1, f); - char next_byte = buf[0]; - char w = inst & 0b00000001; - char d = (inst & 0b00000010) >> 1; - char mod = (next_byte & 0b11000000) >> 6; - char reg = (next_byte & 0b00111000) >> 3; - char rm = (next_byte & 0b00000111); - // Same trick from earlier, see comment - int bytes_to_read = mod % 3; - if (bytes_to_read > 0) bytes_read = fread(buf, sizeof(char), bytes_to_read, f); - Register rgstr = registers[(size_t)reg]; - (void)rm; - if (mod == MODE_RGSTR_MODE) - { - if (d) printf("add %s, [%d] ;7", reg_name(rgstr, w), get_data(buf, w)); - else printf("add [%d], %s ;8", get_data(buf, w), reg_name(rgstr, w)); - } - else if (mod == MODE_MEM_NO_DIS) - { - if (d) printf("add %s, [%s] ;9", reg_name(rgstr, w), get_eac_register(rm)); - else printf("add [%s], %s ;10", get_eac_register(rm), reg_name(rgstr, w)); - } - else - { - if (d) printf("add %s, [%s] ;11", reg_name(rgstr, w), get_eac_register(rm)); - else printf("add [%s], %s ;12", get_eac_register(rm), reg_name(rgstr, w)); - } - } - else if ((inst & ~0x3) == (char)0b10000000) - { - bytes_read = fread(buf, sizeof(char), 1, f); - char w = inst & 0b00000001; - char mod = (buf[0] & 0b11000000) >> 6; - char rm = (buf[0] & 0b00000111); - int bytes_to_read = 1; - bytes_to_read += w == 0 ? 1 : 2; - // Same trick from earlier, see comment - bytes_to_read += mod % 3; - bytes_read = fread(buf, sizeof(char), bytes_to_read, f); - char *eac_name = get_eac_register(rm); - i16 data = get_data(buf + (char)bytes_to_read - (w == 0 ? 1 : 2), w); - char *word_str = w == 0 ? "byte" : "word"; - char disp_str[16] = {'\0'}; - if (mod % 3 > 1) sprintf(disp_str, " + %d", get_data(buf, (mod % 3) - 1)); - printf("add [%s%s], %s %d ;13", eac_name, disp_str, word_str, data); - } - else - { - return false; - } - return bytes_read > 0; -} - char *memory[65536]; // Keep this global for debugging purposes u16 inst_count = 1; diff --git a/decode.h b/decode.h index 9318d04..645ab1f 100644 --- a/decode.h +++ b/decode.h @@ -145,7 +145,8 @@ InstFormat inst_formats[] = .has_rm=true, .parse_reg={.tag = P_REG_MASK, .mask=0b00111000}}, // Immediate to register/memory {.id=7, .name="add", .inst_enc=0b10000000, .mask_inst=0x3, .mask_w=0x1, .has_w=true, - .has_operands=true, .has_displacement=true, .has_data=true, .has_mod=true, .has_rm=true}, + .has_s=true, .has_operands=true, .has_displacement=true, + .has_data=true, .has_mod=true, .has_rm=true}, {.id=8, .name="add", .inst_enc=0b00000100, .mask_inst=0x1, .mask_w=0x1, .has_data=true, .has_w=true, .parse_reg={.tag = P_REG_FIXED, .fixed=0x0}}, };