69 lines
1.9 KiB
Odin
69 lines
1.9 KiB
Odin
package sim_8086
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import "core:os"
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import "core:fmt"
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import "core:math"
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import "core:strings"
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get_operand_value :: proc(operand: Operand) -> u16 {
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#partial switch opr in operand {
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case Immediate:
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return opr.value
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case RegisterId:
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switch opr.access {
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case .Low, .High:
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val := opr.access == .Low ? registers[opr.id].value.low : registers[opr.id].value.high
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return u16(val)
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case .Full:
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return registers[opr.id].value.full
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}
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}
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return 0
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}
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set_register_value :: proc(reg_id: RegisterId, value: u16) {
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switch reg_id.access {
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case .Low:
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registers[reg_id.id].value.low = u8(value)
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case .High:
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registers[reg_id.id].value.high = u8(value)
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case .Full:
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registers[reg_id.id].value.full = u16(value)
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}
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}
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check_zero_flag :: proc(value: u16) {
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CPU.flags.ZF = value == 0
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}
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check_sign_flag :: proc(value: u16) {
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CPU.flags.SF = value >> 15 == 1
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}
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execute_instruction :: proc(inst: Instruction) {
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if reg,ok := inst.dst.(RegisterId); ok {
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#partial switch inst.opname {
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case .MOV:
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src_val := get_operand_value(inst.src)
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set_register_value(reg, src_val)
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case .ADD:
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src_val := get_operand_value(inst.src)
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val := registers[reg.id].value.full + src_val
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set_register_value(reg, val)
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check_zero_flag(val)
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check_sign_flag(val)
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case .SUB:
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src_val := get_operand_value(inst.src)
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val := registers[reg.id].value.full - src_val
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set_register_value(reg, val)
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check_zero_flag(val)
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check_sign_flag(val)
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case .CMP:
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src_val := get_operand_value(inst.src)
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val := registers[reg.id].value.full - src_val
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check_zero_flag(val)
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check_sign_flag(val)
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}
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}
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}
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