ADD instruction sign extension bit handled and deleting old code

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;

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}},
 };