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Fix branching bug

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This commit is contained in:
Franco Colmenarez
2023-06-20 21:51:40 -05:00
parent 92929af185
commit bc47d374e0
1 changed files with 55 additions and 47 deletions
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snes-core/src/cpu/instructions.rs
+55 -47
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@@ -372,8 +372,7 @@ impl CPU {
self.increment_cycles_bit(addressing_mode);
}
fn do_branch(&mut self, bus: &Bus) -> bool {
let nearlabel = bus.read(self.registers.get_pc_address());
fn do_branch(&mut self, nearlabel: u8) -> bool {
let is_negative = (nearlabel >> 7) != 0;
let old_pc = self.registers.get_pc_address();
if is_negative {
@@ -388,56 +387,63 @@ impl CPU {
}
fn bcc(&mut self, bus: &Bus) {
let nearlabel = bus.read(self.registers.get_pc_address().wrapping_add(1));
self.increment_cycles_branch();
if !self.registers.get_carry_flag() {
let page_boundary_crossed = self.do_branch(bus);
let page_boundary_crossed = self.do_branch(nearlabel);
self.increment_cycles_branch_taken(page_boundary_crossed);
}
}
fn bcs(&mut self, bus: &Bus) {
let nearlabel = bus.read(self.registers.get_pc_address().wrapping_add(1));
self.increment_cycles_branch();
if self.registers.get_carry_flag() {
let page_boundary_crossed = self.do_branch(bus);
let page_boundary_crossed = self.do_branch(nearlabel);
self.increment_cycles_branch_taken(page_boundary_crossed);
}
}
fn beq(&mut self, bus: &Bus) {
let nearlabel = bus.read(self.registers.get_pc_address().wrapping_add(1));
self.increment_cycles_branch();
if self.registers.get_zero_flag() {
let page_boundary_crossed = self.do_branch(bus);
let page_boundary_crossed = self.do_branch(nearlabel);
self.increment_cycles_branch_taken(page_boundary_crossed);
}
}
fn bne(&mut self, bus: &Bus) {
let nearlabel = bus.read(self.registers.get_pc_address().wrapping_add(1));
self.increment_cycles_branch();
if !self.registers.get_zero_flag() {
let page_boundary_crossed = self.do_branch(bus);
let page_boundary_crossed = self.do_branch(nearlabel);
self.increment_cycles_branch_taken(page_boundary_crossed);
}
}
fn bmi(&mut self, bus: &Bus) {
let nearlabel = bus.read(self.registers.get_pc_address().wrapping_add(1));
self.increment_cycles_branch();
if self.registers.get_negative_flag() {
let page_boundary_crossed = self.do_branch(bus);
let page_boundary_crossed = self.do_branch(nearlabel);
self.increment_cycles_branch_taken(page_boundary_crossed);
}
}
fn bpl(&mut self, bus: &Bus) {
let nearlabel = bus.read(self.registers.get_pc_address().wrapping_add(1));
self.increment_cycles_branch();
if !self.registers.get_negative_flag() {
let page_boundary_crossed = self.do_branch(bus);
let page_boundary_crossed = self.do_branch(nearlabel);
self.increment_cycles_branch_taken(page_boundary_crossed);
}
}
fn bra(&mut self, bus: &Bus) {
let nearlabel = bus.read(self.registers.get_pc_address().wrapping_add(1));
self.increment_cycles_branch();
let page_boundary_crossed = self.do_branch(bus);
let page_boundary_crossed = self.do_branch(nearlabel);
self.increment_cycles_branch_taken(page_boundary_crossed);
}
@@ -455,17 +461,19 @@ impl CPU {
}
fn bvc(&mut self, bus: &Bus) {
let nearlabel = bus.read(self.registers.get_pc_address().wrapping_add(1));
self.increment_cycles_branch();
if !self.registers.get_overflow_flag() {
let page_boundary_crossed = self.do_branch(bus);
let page_boundary_crossed = self.do_branch(nearlabel);
self.increment_cycles_branch_taken(page_boundary_crossed);
}
}
fn bvs(&mut self, bus: &Bus) {
let nearlabel = bus.read(self.registers.get_pc_address().wrapping_add(1));
self.increment_cycles_branch();
if self.registers.get_overflow_flag() {
let page_boundary_crossed = self.do_branch(bus);
let page_boundary_crossed = self.do_branch(nearlabel);
self.increment_cycles_branch_taken(page_boundary_crossed);
}
}
@@ -1733,17 +1741,17 @@ mod cpu_instructions_tests {
cpu.registers.pc = 0x0000;
cpu.cycles = 0;
cpu.registers.set_carry_flag(false);
bus.write(0x02, 0b00001111);
bus.write(0x01, 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.registers.pc = 0x0100;
cpu.cycles = 0;
cpu.registers.set_carry_flag(false);
bus.write(0x100, 0xFF); // write -1
bus.write(0x101, 0xFB); // write -5
cpu.bcc(&bus);
assert_eq!(cpu.registers.pc, 0xFF);
assert_eq!(cpu.registers.pc, 0xFD);
assert_eq!(cpu.cycles, 4);
}
@@ -1764,17 +1772,17 @@ mod cpu_instructions_tests {
cpu.registers.pc = 0x0000;
cpu.cycles = 0;
cpu.registers.set_carry_flag(true);
bus.write(0x02, 0b00001111);
bus.write(0x01, 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.registers.pc = 0x0100;
cpu.cycles = 0;
cpu.registers.set_carry_flag(true);
bus.write(0x100, 0xFF); // write -1
bus.write(0x101, 0xFB); // write -5
cpu.bcs(&bus);
assert_eq!(cpu.registers.pc, 0xFF);
assert_eq!(cpu.registers.pc, 0xFD);
assert_eq!(cpu.cycles, 4);
}
@@ -1795,17 +1803,17 @@ mod cpu_instructions_tests {
cpu.registers.pc = 0x0000;
cpu.cycles = 0;
cpu.registers.set_zero_flag(true);
bus.write(0x02, 0b00001111);
bus.write(0x01, 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.registers.pc = 0x0100;
cpu.cycles = 0;
cpu.registers.set_zero_flag(true);
bus.write(0x100, 0xFF); // write -1
bus.write(0x101, 0xFB); // write -5
cpu.beq(&bus);
assert_eq!(cpu.registers.pc, 0xFF);
assert_eq!(cpu.registers.pc, 0xFD);
assert_eq!(cpu.cycles, 4);
}
@@ -1826,17 +1834,17 @@ mod cpu_instructions_tests {
cpu.registers.pc = 0x0000;
cpu.cycles = 0;
cpu.registers.set_zero_flag(false);
bus.write(0x02, 0b00001111);
bus.write(0x01, 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.registers.pc = 0x0100;
cpu.cycles = 0;
cpu.registers.set_zero_flag(false);
bus.write(0x100, 0xFF); // write -1
bus.write(0x101, 0xFB); // write -5
cpu.bne(&bus);
assert_eq!(cpu.registers.pc, 0xFF);
assert_eq!(cpu.registers.pc, 0xFD);
assert_eq!(cpu.cycles, 4);
}
@@ -1857,17 +1865,17 @@ mod cpu_instructions_tests {
cpu.registers.pc = 0x0000;
cpu.cycles = 0;
cpu.registers.set_negative_flag(true);
bus.write(0x02, 0b00001111);
bus.write(0x01, 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.registers.pc = 0x0100;
cpu.cycles = 0;
cpu.registers.set_negative_flag(true);
bus.write(0x100, 0xFF); // write -1
bus.write(0x101, 0xFB); // write -5
cpu.bmi(&bus);
assert_eq!(cpu.registers.pc, 0xFF);
assert_eq!(cpu.registers.pc, 0xFD);
assert_eq!(cpu.cycles, 4);
}
@@ -1888,17 +1896,17 @@ mod cpu_instructions_tests {
cpu.registers.pc = 0x0000;
cpu.cycles = 0;
cpu.registers.set_negative_flag(false);
bus.write(0x02, 0b00001111);
bus.write(0x01, 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.registers.pc = 0x0100;
cpu.cycles = 0;
cpu.registers.set_negative_flag(false);
bus.write(0x100, 0xFF); // write -1
bus.write(0x101, 0xFB); // write -5
cpu.bpl(&bus);
assert_eq!(cpu.registers.pc, 0xFF);
assert_eq!(cpu.registers.pc, 0xFD);
assert_eq!(cpu.cycles, 4);
}
@@ -1910,16 +1918,16 @@ mod cpu_instructions_tests {
let mut bus = Bus::new();
cpu.registers.pc = 0x0000;
cpu.cycles = 0;
bus.write(0x02, 0b00001111);
bus.write(0x01, 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.registers.pc = 0x0100;
cpu.cycles = 0;
bus.write(0x100, 0xFF); // write -1
bus.write(0x101, 0xFB); // write -5
cpu.bra(&bus);
assert_eq!(cpu.registers.pc, 0xFF);
assert_eq!(cpu.registers.pc, 0xFD);
assert_eq!(cpu.cycles, 4);
}
@@ -1963,17 +1971,17 @@ mod cpu_instructions_tests {
cpu.registers.pc = 0x0000;
cpu.cycles = 0;
cpu.registers.set_overflow_flag(false);
bus.write(0x02, 0b00001111);
bus.write(0x01, 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.registers.pc = 0x0100;
cpu.cycles = 0;
cpu.registers.set_overflow_flag(false);
bus.write(0x100, 0xFF); // write -1
bus.write(0x101, 0xFB); // write -5
cpu.bvc(&bus);
assert_eq!(cpu.registers.pc, 0xFF);
assert_eq!(cpu.registers.pc, 0xFD);
assert_eq!(cpu.cycles, 4);
}
@@ -1994,17 +2002,17 @@ mod cpu_instructions_tests {
cpu.registers.pc = 0x0000;
cpu.cycles = 0;
cpu.registers.set_overflow_flag(true);
bus.write(0x02, 0b00001111);
bus.write(0x01, 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.registers.pc = 0x0100;
cpu.cycles = 0;
cpu.registers.set_overflow_flag(true);
bus.write(0x100, 0xFF); // write -1
bus.write(0x101, 0xFB); // write -5
cpu.bvs(&bus);
assert_eq!(cpu.registers.pc, 0xFF);
assert_eq!(cpu.registers.pc, 0xFD);
assert_eq!(cpu.cycles, 4);
}