added add_eb_gb and add_ev_gv instructions, fixed some stuff ig

2025-06-08 22:28:03 +03:00
parent 930cd451a9
commit 500ffda8c2
4 changed files with 226 additions and 24 deletions
--- a/instructions.h
+++ b/instructions.h
@@ -7,4 +7,79 @@ void add_eb_gb() {

    ModRM modrm = parse_modrm(modrm_byte);
    uint8_t gb_value = get_reg_byte(modrm.reg);
+    uint8_t eb_value;
+    uint32_t eb_addr;
+    bool eb_is_mem = false;
+
+    if (modrm.mod == 3) {
+        // eb is a reg
+        eb_value = get_reg_byte(modrm.rm);
+    } else {
+        // eb is an addr
+        uint32_t eff_addr = calc_effective_addr(modrm);
+        uint16_t segment = (modrm.rm == 2 || modrm.rm == 3 || modrm.rm == 6) ? SS : DS;
+        uint32_t phys_addr = physical_addr(segment, eff_addr);
+        eb_value = ram[phys_addr];
+        eb_is_mem = true;
+    }
+
+    uint8_t result = eb_value + gb_value;
+
+    if (eb_is_mem) {
+        ram[eb_addr] = result;
+    } else {
+        set_reg_byte(modrm.rm, result);
+    }
+
+    update_flags_add(eb_value, gb_value, result);
+}
+
+void add_ev_gv() {
+    uint32_t addr = physical_addr(CS, IP);
+    uint8_t modrm_byte = ram[addr];
+    IP ++;
+
+    ModRM modrm = parse_modrm(modrm_byte);
+    uint16_t gv_value = get_reg_word(modrm.reg);
+    uint16_t ev_value;
+    uint32_t ev_addr;
+    bool ev_is_mem = false;
+
+    if (modrm.mod == 3) {
+        ev_value = get_reg_word(modrm.rm);
+    } else {
+        uint16_t seg = (modrm.rm == 4 || modrm.rm == 5 || modrm.rm == 6) ? SS : DS;
+        uint16_t eff_addr = calc_effective_addr(modrm);
+        ev_addr = physical_addr(seg, eff_addr);
+        
+        ev_value = ram[ev_addr] | (ram[ev_addr + 1] << 8);
+        ev_is_mem = true;
+    }
+
+    uint16_t result = ev_value + gv_value;
+
+    if (ev_is_mem) {
+        ram[ev_addr] = result & 0xFF;
+        ram[ev_addr + 1] = result >> 8;
+    } else {
+        set_reg_word(modrm.rm, result);
+    }
+
+    update_flags_add16(ev_value, gv_value, result);
+    std::cout << "AX = " << std::hex << AX.value 
+              << " (AL=" << (int)AX.low << ")\n";
+}
+
+void hlt() {
+    std::cout << "HLT\n";
+    exit(0);
+}
+
+using instrHandler = void(*)();
+instrHandler instr_table[256] = { nullptr };
+
+void init_instr_table() {
+    instr_table[0x00] = add_eb_gb;
+    instr_table[0x01] = add_ev_gv;
+    instr_table[0xf4] = hlt;
 }