FranLMSP/snes
1
0
Fork 0
mirror of https://github.com/FranLMSP/snes.git synced 2026-08-03 08:30:01 -04:00
Code Issues Packages Projects Releases Wiki Activity

Branch instructions

Browse Source
This commit is contained in:
Franco Colmenarez
2022-11-25 21:52:57 -05:00
parent ab6c526892
commit e13b93d9e3
3 changed files with 429 additions and 0 deletions
Download Patch File Download Diff File Expand all files Collapse all files
snes-core/src/cpu/cycles.rs
+15
View File
@@ -164,6 +164,21 @@ impl CPU {
pub fn increment_cycles_clear(&mut self) {
self.registers.increment_pc(1); self.cycles += 2;
}
pub fn increment_cycles_branch(&mut self) {
self.registers.increment_pc(2); self.cycles += 2;
}
pub fn increment_cycles_branch_taken(&mut self, page_boundary_crossed: bool) {
self.cycles += 1;
if page_boundary_crossed {
self.cycles += 1;
}
}
pub fn increment_cycles_branch_long(&mut self) {
self.registers.increment_pc(3); self.cycles += 4;
}
}
#[cfg(test)]
snes-core/src/cpu/instructions.rs
+410
View File
@@ -144,6 +144,104 @@ impl CPU {
self.increment_cycles_bit(addressing_mode);
}
pub fn do_branch(&mut self, bus: &Bus) -> bool {
let nearlabel = bus.read(self.registers.get_pc_address());
let is_negative = (nearlabel >> 7) != 0;
let old_pc = self.registers.get_pc_address();
if is_negative {
let nearlabel = !nearlabel + 1;
self.registers.decrement_pc(nearlabel as u16);
} else {
self.registers.increment_pc(nearlabel as u16);
}
let new_pc = self.registers.get_pc_address();
let page_boundary_crossed = (old_pc & 0xFF00) != (new_pc & 0xFF00);
return page_boundary_crossed
}
pub fn bcc(&mut self, bus: &Bus) {
self.increment_cycles_branch();
if !self.registers.get_carry_flag() {
let page_boundary_crossed = self.do_branch(bus);
self.increment_cycles_branch_taken(page_boundary_crossed);
}
}
pub fn bcs(&mut self, bus: &Bus) {
self.increment_cycles_branch();
if self.registers.get_carry_flag() {
let page_boundary_crossed = self.do_branch(bus);
self.increment_cycles_branch_taken(page_boundary_crossed);
}
}
pub fn beq(&mut self, bus: &Bus) {
self.increment_cycles_branch();
if self.registers.get_zero_flag() {
let page_boundary_crossed = self.do_branch(bus);
self.increment_cycles_branch_taken(page_boundary_crossed);
}
}
pub fn bne(&mut self, bus: &Bus) {
self.increment_cycles_branch();
if !self.registers.get_zero_flag() {
let page_boundary_crossed = self.do_branch(bus);
self.increment_cycles_branch_taken(page_boundary_crossed);
}
}
pub fn bmi(&mut self, bus: &Bus) {
self.increment_cycles_branch();
if self.registers.get_negative_flag() {
let page_boundary_crossed = self.do_branch(bus);
self.increment_cycles_branch_taken(page_boundary_crossed);
}
}
pub fn bpl(&mut self, bus: &Bus) {
self.increment_cycles_branch();
if !self.registers.get_negative_flag() {
let page_boundary_crossed = self.do_branch(bus);
self.increment_cycles_branch_taken(page_boundary_crossed);
}
}
pub fn bra(&mut self, bus: &Bus) {
self.increment_cycles_branch();
let page_boundary_crossed = self.do_branch(bus);
self.increment_cycles_branch_taken(page_boundary_crossed);
}
pub fn brl(&mut self, bus: &Bus) {
let label = bus.read(self.registers.get_pc_address()) as u16 |
((bus.read(self.registers.get_pc_address() + 1) as u16) << 8);
let is_negative = (label >> 15) != 0;
if is_negative {
let label = !label + 1;
self.registers.decrement_pc(label);
} else {
self.registers.increment_pc(label);
}
self.increment_cycles_branch_long();
}
pub fn bvc(&mut self, bus: &Bus) {
self.increment_cycles_branch();
if !self.registers.get_overflow_flag() {
let page_boundary_crossed = self.do_branch(bus);
self.increment_cycles_branch_taken(page_boundary_crossed);
}
}
pub fn bvs(&mut self, bus: &Bus) {
self.increment_cycles_branch();
if self.registers.get_overflow_flag() {
let page_boundary_crossed = self.do_branch(bus);
self.increment_cycles_branch_taken(page_boundary_crossed);
}
}
pub fn clc(&mut self) {
self.registers.set_carry_flag(false);
self.increment_cycles_clear();
@@ -222,6 +320,26 @@ impl CPU {
0x06 => self.asl(bus, A::DirectPage),
0x1E => self.asl(bus, A::AbsoluteIndexed(I::X)),
0x16 => self.asl(bus, A::DirectPageIndexed(I::X)),
// BCC
0x90 => self.bcc(bus),
// BCS
0xB0 => self.bcs(bus),
// BEQ
0xF0 => self.beq(bus),
// BNE
0xD0 => self.bne(bus),
// BMI
0x30 => self.bmi(bus),
// BPL
0x10 => self.bpl(bus),
// BRA
0x80 => self.bra(bus),
// BRL
0x82 => self.brl(bus),
// BVC
0x50 => self.bvc(bus),
// BVS
0x70 => self.bvs(bus),
// BIT
0x89 => self.bit(bus, A::Immediate),
0x2C => self.bit(bus, A::Absolute),
@@ -397,4 +515,296 @@ mod cpu_instructions_tests {
assert_eq!(cpu.registers.pc, 1);
assert_eq!(cpu.cycles, 2);
}
#[test]
fn test_bcc() {
// test with positive nearlabel
// branch not taken
let mut cpu = CPU::new();
let mut bus = Bus::new();
cpu.registers.pc = 0x0000;
cpu.cycles = 0;
cpu.registers.set_carry_flag(true);
bus.write(0x02, 0b00001111);
cpu.bcc(&bus);
assert_eq!(cpu.registers.pc, 0x02);
assert_eq!(cpu.cycles, 2);
// branch taken
cpu.registers.pc = 0x0000;
cpu.cycles = 0;
cpu.registers.set_carry_flag(false);
bus.write(0x02, 0b00001111);
cpu.bcc(&bus);
assert_eq!(cpu.registers.pc, 0x02 + 0b00001111);
assert_eq!(cpu.cycles, 3);
// test with negative nearlabel and boundary cross
cpu.registers.pc = 0x00FE;
cpu.cycles = 0;
cpu.registers.set_carry_flag(false);
bus.write(0x100, 0xFF); // write -1
cpu.bcc(&bus);
assert_eq!(cpu.registers.pc, 0xFF);
assert_eq!(cpu.cycles, 4);
}
#[test]
fn test_bcs() {
// test with positive nearlabel
// branch not taken
let mut cpu = CPU::new();
let mut bus = Bus::new();
cpu.registers.pc = 0x0000;
cpu.cycles = 0;
cpu.registers.set_carry_flag(false);
bus.write(0x02, 0b00001111);
cpu.bcs(&bus);
assert_eq!(cpu.registers.pc, 0x02);
assert_eq!(cpu.cycles, 2);
// branch taken
cpu.registers.pc = 0x0000;
cpu.cycles = 0;
cpu.registers.set_carry_flag(true);
bus.write(0x02, 0b00001111);
cpu.bcs(&bus);
assert_eq!(cpu.registers.pc, 0x02 + 0b00001111);
assert_eq!(cpu.cycles, 3);
// test with negative nearlabel and boundary cross
cpu.registers.pc = 0x00FE;
cpu.cycles = 0;
cpu.registers.set_carry_flag(true);
bus.write(0x100, 0xFF); // write -1
cpu.bcs(&bus);
assert_eq!(cpu.registers.pc, 0xFF);
assert_eq!(cpu.cycles, 4);
}
#[test]
fn test_beq() {
// test with positive nearlabel
// branch not taken
let mut cpu = CPU::new();
let mut bus = Bus::new();
cpu.registers.pc = 0x0000;
cpu.cycles = 0;
cpu.registers.set_zero_flag(false);
bus.write(0x02, 0b00001111);
cpu.beq(&bus);
assert_eq!(cpu.registers.pc, 0x02);
assert_eq!(cpu.cycles, 2);
// branch taken
cpu.registers.pc = 0x0000;
cpu.cycles = 0;
cpu.registers.set_zero_flag(true);
bus.write(0x02, 0b00001111);
cpu.beq(&bus);
assert_eq!(cpu.registers.pc, 0x02 + 0b00001111);
assert_eq!(cpu.cycles, 3);
// test with negative nearlabel and boundary cross
cpu.registers.pc = 0x00FE;
cpu.cycles = 0;
cpu.registers.set_zero_flag(true);
bus.write(0x100, 0xFF); // write -1
cpu.beq(&bus);
assert_eq!(cpu.registers.pc, 0xFF);
assert_eq!(cpu.cycles, 4);
}
#[test]
fn test_bne() {
// test with positive nearlabel
// branch not taken
let mut cpu = CPU::new();
let mut bus = Bus::new();
cpu.registers.pc = 0x0000;
cpu.cycles = 0;
cpu.registers.set_zero_flag(true);
bus.write(0x02, 0b00001111);
cpu.bne(&bus);
assert_eq!(cpu.registers.pc, 0x02);
assert_eq!(cpu.cycles, 2);
// branch taken
cpu.registers.pc = 0x0000;
cpu.cycles = 0;
cpu.registers.set_zero_flag(false);
bus.write(0x02, 0b00001111);
cpu.bne(&bus);
assert_eq!(cpu.registers.pc, 0x02 + 0b00001111);
assert_eq!(cpu.cycles, 3);
// test with negative nearlabel and boundary cross
cpu.registers.pc = 0x00FE;
cpu.cycles = 0;
cpu.registers.set_zero_flag(false);
bus.write(0x100, 0xFF); // write -1
cpu.bne(&bus);
assert_eq!(cpu.registers.pc, 0xFF);
assert_eq!(cpu.cycles, 4);
}
#[test]
fn test_bmi() {
// test with positive nearlabel
// branch not taken
let mut cpu = CPU::new();
let mut bus = Bus::new();
cpu.registers.pc = 0x0000;
cpu.cycles = 0;
cpu.registers.set_negative_flag(false);
bus.write(0x02, 0b00001111);
cpu.bmi(&bus);
assert_eq!(cpu.registers.pc, 0x02);
assert_eq!(cpu.cycles, 2);
// branch taken
cpu.registers.pc = 0x0000;
cpu.cycles = 0;
cpu.registers.set_negative_flag(true);
bus.write(0x02, 0b00001111);
cpu.bmi(&bus);
assert_eq!(cpu.registers.pc, 0x02 + 0b00001111);
assert_eq!(cpu.cycles, 3);
// test with negative nearlabel and boundary cross
cpu.registers.pc = 0x00FE;
cpu.cycles = 0;
cpu.registers.set_negative_flag(true);
bus.write(0x100, 0xFF); // write -1
cpu.bmi(&bus);
assert_eq!(cpu.registers.pc, 0xFF);
assert_eq!(cpu.cycles, 4);
}
#[test]
fn test_bpl() {
// test with positive nearlabel
// branch not taken
let mut cpu = CPU::new();
let mut bus = Bus::new();
cpu.registers.pc = 0x0000;
cpu.cycles = 0;
cpu.registers.set_negative_flag(true);
bus.write(0x02, 0b00001111);
cpu.bpl(&bus);
assert_eq!(cpu.registers.pc, 0x02);
assert_eq!(cpu.cycles, 2);
// branch taken
cpu.registers.pc = 0x0000;
cpu.cycles = 0;
cpu.registers.set_negative_flag(false);
bus.write(0x02, 0b00001111);
cpu.bpl(&bus);
assert_eq!(cpu.registers.pc, 0x02 + 0b00001111);
assert_eq!(cpu.cycles, 3);
// test with negative nearlabel and boundary cross
cpu.registers.pc = 0x00FE;
cpu.cycles = 0;
cpu.registers.set_negative_flag(false);
bus.write(0x100, 0xFF); // write -1
cpu.bpl(&bus);
assert_eq!(cpu.registers.pc, 0xFF);
assert_eq!(cpu.cycles, 4);
}
#[test]
fn test_bra() {
// test with positive nearlabel
// branch always taken
let mut cpu = CPU::new();
let mut bus = Bus::new();
cpu.registers.pc = 0x0000;
cpu.cycles = 0;
bus.write(0x02, 0b00001111);
cpu.bra(&bus);
assert_eq!(cpu.registers.pc, 0x02 + 0b00001111);
assert_eq!(cpu.cycles, 3);
// test with negative nearlabel and boundary cross
cpu.registers.pc = 0x00FE;
cpu.cycles = 0;
bus.write(0x100, 0xFF); // write -1
cpu.bra(&bus);
assert_eq!(cpu.registers.pc, 0xFF);
assert_eq!(cpu.cycles, 4);
}
#[test]
fn test_brl() {
// test with positive nearlabel
// branch always taken
let mut cpu = CPU::new();
let mut bus = Bus::new();
cpu.registers.pc = 0x0001;
cpu.cycles = 0;
bus.write(0x01, 0b00000000);
bus.write(0x02, 0b00001111);
cpu.brl(&bus);
assert_eq!(cpu.registers.pc, 0x04 + 0b00001111_00000000);
assert_eq!(cpu.cycles, 4);
// test with negative nearlabel and boundary cross
cpu.registers.pc = 0x00FD;
cpu.cycles = 0;
bus.write(0xFD, 0xFF); // write -1
bus.write(0xFE, 0xFF); // write -1
cpu.brl(&bus);
assert_eq!(cpu.registers.pc, 0xFF);
assert_eq!(cpu.cycles, 4);
}
#[test]
fn test_bvc() {
// test with positive nearlabel
// branch not taken
let mut cpu = CPU::new();
let mut bus = Bus::new();
cpu.registers.pc = 0x0000;
cpu.cycles = 0;
cpu.registers.set_overflow_flag(true);
bus.write(0x02, 0b00001111);
cpu.bvc(&bus);
assert_eq!(cpu.registers.pc, 0x02);
assert_eq!(cpu.cycles, 2);
// branch taken
cpu.registers.pc = 0x0000;
cpu.cycles = 0;
cpu.registers.set_overflow_flag(false);
bus.write(0x02, 0b00001111);
cpu.bvc(&bus);
assert_eq!(cpu.registers.pc, 0x02 + 0b00001111);
assert_eq!(cpu.cycles, 3);
// test with negative nearlabel and boundary cross
cpu.registers.pc = 0x00FE;
cpu.cycles = 0;
cpu.registers.set_overflow_flag(false);
bus.write(0x100, 0xFF); // write -1
cpu.bvc(&bus);
assert_eq!(cpu.registers.pc, 0xFF);
assert_eq!(cpu.cycles, 4);
}
#[test]
fn test_bvs() {
// test with positive nearlabel
// branch not taken
let mut cpu = CPU::new();
let mut bus = Bus::new();
cpu.registers.pc = 0x0000;
cpu.cycles = 0;
cpu.registers.set_overflow_flag(false);
bus.write(0x02, 0b00001111);
cpu.bvs(&bus);
assert_eq!(cpu.registers.pc, 0x02);
assert_eq!(cpu.cycles, 2);
// branch taken
cpu.registers.pc = 0x0000;
cpu.cycles = 0;
cpu.registers.set_overflow_flag(true);
bus.write(0x02, 0b00001111);
cpu.bvs(&bus);
assert_eq!(cpu.registers.pc, 0x02 + 0b00001111);
assert_eq!(cpu.cycles, 3);
// test with negative nearlabel and boundary cross
cpu.registers.pc = 0x00FE;
cpu.cycles = 0;
cpu.registers.set_overflow_flag(true);
bus.write(0x100, 0xFF); // write -1
cpu.bvs(&bus);
assert_eq!(cpu.registers.pc, 0xFF);
assert_eq!(cpu.cycles, 4);
}
}
snes-core/src/cpu/registers.rs
+4
View File
@@ -130,6 +130,10 @@ impl Registers {
self.pc = self.pc.wrapping_add(bytes);
}
pub fn decrement_pc(&mut self, bytes: u16) {
self.pc = self.pc.wrapping_sub(bytes);
}
pub fn direct_page_low(&self) -> u8 {
self.d as u8
}