cmp

snes-core/src/cpu/instructionstemp/cmp.rs

@@ -0,0 +1,98 @@
+use crate::{cpu::{bus::Bus, registers::Registers}, utils::addressing::AddressingMode};
+
+use crate::cpu::cycles;
+use super::{CPUInstruction, Decode, read_8bit_from_address, read_16bit_from_address};
+use super::decoder_common;
+use super::comp_common;
+
+static INSTR_NAME: &'static str = "CMP";
+
+pub struct CMP8 {
+    addressing_mode: AddressingMode,
+}
+
+impl CPUInstruction for CMP8 {
+    fn execute(&self, registers: &mut Registers, bus: &mut Bus) {
+        comp_common::do_comp(
+            registers,
+            registers.a as u8,
+            read_8bit_from_address(registers, bus, self.addressing_mode),
+        );
+        let (bytes, cycles) = cycles::increment_cycles_arithmetic(&registers, self.addressing_mode);
+        registers.increment_pc(bytes); registers.cycles += cycles;
+    }
+}
+
+impl Decode for CMP8 {
+    fn mnemonic(&self, registers: &Registers, bus: &Bus, opcode: u8) -> String {
+        decoder_common::mnemonic_arithmetic(false, opcode, INSTR_NAME, self.addressing_mode, registers, bus)
+    }
+}
+
+pub struct CMP16 {
+    addressing_mode: AddressingMode,
+}
+
+impl CPUInstruction for CMP16 {
+    fn execute(&self, registers: &mut Registers, bus: &mut Bus) {
+        comp_common::do_comp(
+            registers,
+            registers.a,
+            read_16bit_from_address(registers, bus, self.addressing_mode),
+        );
+        let (bytes, cycles) = cycles::increment_cycles_arithmetic(&registers, self.addressing_mode);
+        registers.increment_pc(bytes); registers.cycles += cycles;
+    }
+}
+
+impl Decode for CMP16 {
+    fn mnemonic(&self, registers: &Registers, bus: &Bus, opcode: u8) -> String {
+        decoder_common::mnemonic_arithmetic(true, opcode, INSTR_NAME, self.addressing_mode, registers, bus)
+    }
+}
+
+
+#[cfg(test)]
+mod cpu_instructions_tests {
+    use super::*;
+
+    #[test]
+    fn test_8bit() {
+        // CMP is basically an SBC instruction but it doesn't
+        // store the result nor it affects the overflow flag
+        let mut registers = Registers::new();
+        let mut bus = Bus::new();
+        registers.a   = 0x0001;
+        registers.pbr = 0x00;
+        registers.pc  = 0x0000;
+        registers.set_memory_select_flag(true);
+        bus.write(0x000001, 1);
+        let instruction = CMP8{addressing_mode: AddressingMode::Immediate};
+        instruction.execute(&mut registers, &mut bus);
+        assert_eq!(registers.a, 0x0001); // check A is not affected
+        assert_eq!(registers.pc, 0x02);
+        assert_eq!(registers.cycles, 2);
+        assert!(!registers.get_carry_flag());
+        assert!(registers.get_zero_flag());
+    }
+
+    #[test]
+    fn test_and_16bit() {
+        let mut registers = Registers::new();
+        let mut bus = Bus::new();
+        registers.a   = 0x0050;
+        registers.pbr = 0x00;
+        registers.pc  = 0x0000;
+        registers.set_16bit_mode(false);
+        registers.set_overflow_flag(false);
+        bus.write(0x000001, 0xB0);
+        let instruction = CMP16{addressing_mode: AddressingMode::Immediate};
+        instruction.execute(&mut registers, &mut bus);
+        assert_eq!(registers.a, 0x0050); // check A is not affected
+        assert_eq!(registers.pc, 0x02);
+        assert_eq!(registers.cycles, 2);
+        assert!(registers.get_carry_flag());
+        assert!(!registers.get_zero_flag());
+        assert!(!registers.get_overflow_flag());
+    }
+}

snes-core/src/cpu/instructionstemp/comp_common.rs

@@ -0,0 +1,12 @@
+use crate::{cpu::registers::Registers, utils::{num_trait::SnesNum, alu}, common::flags::Flags};
+
+
+pub fn do_comp<T: SnesNum>(registers: &mut Registers, target: T, value: T) {
+    let (_, affected_flags) = alu::sbc_bin(target, value, false);
+    for flag in affected_flags {
+        match flag {
+            Flags::Overflow(_) => {},
+            _ => registers.set_flags(&[flag]),
+        }
+    }
+}

snes-core/src/cpu/instructionstemp/mod.rs

@@ -21,10 +21,12 @@ pub mod clc;
 pub mod cld;
 pub mod cli;
 pub mod clv;
+pub mod cmp;
 pub mod bit_common;
 pub mod decoder_common;
 pub mod branch_common;
 pub mod push_common;
+pub mod comp_common;
 
 pub trait CPUInstruction {
     fn execute(&self, registers: &mut Registers, bus: &mut Bus);