From 4fb334efdbfa9c1d8e6563923478036113c9bc5d Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Jo=C3=A3o=20Magalh=C3=A3es?= <joamag@gmail.com>
Date: Tue, 5 Jul 2022 09:33:00 +0100
Subject: [PATCH] fix: major intruction fixes!
---
examples/sdl/src/main.rs | 6 +-
src/inst.rs | 356 +++++++++++++++++++++++++++++++++------
2 files changed, 307 insertions(+), 55 deletions(-)
diff --git a/examples/sdl/src/main.rs b/examples/sdl/src/main.rs
index a35592ab..4b1648e2 100644
--- a/examples/sdl/src/main.rs
+++ b/examples/sdl/src/main.rs
@@ -83,16 +83,18 @@ fn main() {
//game_boy.load_rom_file("../../res/roms.prop/tetris.gb");
//game_boy.load_rom_file("../../res/roms.prop/alleyway.gb");
-
+
//game_boy.load_rom_file("../../res/roms/firstwhite.gb");
//game_boy.load_rom_file("../../res/roms/opus5.gb");
//game_boy.load_rom_file("../../res/roms/ld_r_r.gb");
//game_boy.load_rom_file("../../res/roms/special.gb");
- game_boy.load_rom_file("../../res/roms/paradius/cpu/03-op sp,hl.gb");
+ //game_boy.load_rom_file("../../res/roms/paradius/cpu/03-op sp,hl.gb"); // NO FINISH
//game_boy.load_rom_file("../../res/roms/paradius/cpu/04-op r,imm.gb"); // PASSED
//game_boy.load_rom_file("../../res/roms/paradius/cpu/06-ld r,r.gb"); // PASSED
//game_boy.load_rom_file("../../res/roms/paradius/cpu/07-jr,jp,call,ret,rst.gb"); // PASSED
+ //game_boy.load_rom_file("../../res/roms/paradius/cpu/08-misc instrs.gb"); // PASSED
+ game_boy.load_rom_file("../../res/roms/paradius/cpu/09-op r,r.gb");
let mut counter = 0;
diff --git a/src/inst.rs b/src/inst.rs
index 3dd9d5d5..02d77314 100644
--- a/src/inst.rs
+++ b/src/inst.rs
@@ -1,3 +1,6 @@
+use core::time;
+use std::thread;
+
use crate::cpu::Cpu;
pub const INSTRUCTIONS: [(fn(&mut Cpu), u8, &'static str); 256] = [
@@ -17,7 +20,7 @@ pub const INSTRUCTIONS: [(fn(&mut Cpu), u8, &'static str); 256] = [
(inc_c, 4, "INC C"),
(dec_c, 4, "DEC C"),
(ld_c_u8, 8, "LD C, u8"),
- (noimpl, 4, "! UNIMP !"),
+ (rrca, 4, "RRCA"),
// 0x1 opcodes
(stop, 4, "STOP"),
(ld_de_u16, 12, "LD DE, u16"),
@@ -68,7 +71,7 @@ pub const INSTRUCTIONS: [(fn(&mut Cpu), u8, &'static str); 256] = [
(inc_a, 4, "INC A"),
(dec_a, 4, "DEC A"),
(ld_a_u8, 8, "LD A, u8"),
- (noimpl, 4, "! UNIMP !"),
+ (ccf, 4, "CCF"),
// 0x4 opcodes
(ld_b_b, 4, "LD B, B"),
(ld_b_c, 4, "LD B, C"),
@@ -146,31 +149,31 @@ pub const INSTRUCTIONS: [(fn(&mut Cpu), u8, &'static str); 256] = [
(add_a_l, 4, "ADD A, L"),
(add_a_mhl, 8, "ADD A, [HL]"),
(add_a_a, 4, "ADD A, A"),
- (add_a_b, 4, "ADD A, B"),
- (add_a_c, 4, "ADD A, C"),
- (add_a_d, 4, "ADD A, D"),
- (add_a_e, 4, "ADD A, E"),
- (add_a_h, 4, "ADD A, H"),
- (add_a_l, 4, "ADD A, L"),
- (add_a_mhl, 8, "ADD A, [HL]"),
- (add_a_a, 4, "ADD A, A"),
+ (adc_a_b, 4, "ADC A, B"),
+ (adc_a_c, 4, "ADC A, C"),
+ (adc_a_d, 4, "ADC A, D"),
+ (adc_a_e, 4, "ADC A, E"),
+ (adc_a_h, 4, "ADC A, H"),
+ (adc_a_l, 4, "ADC A, L"),
+ (adc_a_mhl, 8, "ADC A, [HL]"),
+ (adc_a_a, 4, "ADC A, A"),
// 0x9 opcodes
(sub_a_b, 4, "SUB A, B"),
- (noimpl, 4, "! UNIMP !"),
- (noimpl, 4, "! UNIMP !"),
- (noimpl, 4, "! UNIMP !"),
- (noimpl, 4, "! UNIMP !"),
- (noimpl, 4, "! UNIMP !"),
- (noimpl, 4, "! UNIMP !"),
+ (sub_a_c, 4, "SUB A, C"),
+ (sub_a_d, 4, "SUB A, D"),
+ (sub_a_e, 4, "SUB A, E"),
+ (sub_a_h, 4, "SUB A, H"),
+ (sub_a_l, 4, "SUB A, L"),
+ (sub_a_mhl, 8, "SUB A, [HL]"),
(sub_a_a, 4, "SUB A, A"),
- (noimpl, 4, "! UNIMP !"),
- (noimpl, 4, "! UNIMP !"),
- (noimpl, 4, "! UNIMP !"),
- (noimpl, 4, "! UNIMP !"),
- (noimpl, 4, "! UNIMP !"),
- (noimpl, 4, "! UNIMP !"),
- (noimpl, 4, "! UNIMP !"),
- (noimpl, 4, "! UNIMP !"),
+ (sbc_a_b, 4, "SBC A, B"),
+ (sbc_a_c, 4, "SBC A, C"),
+ (sbc_a_d, 4, "SBC A, D"),
+ (sbc_a_e, 4, "SBC A, E"),
+ (sbc_a_h, 4, "SBC A, H"),
+ (sbc_a_l, 4, "SBC A, L"),
+ (sbc_a_mhl, 8, "SBC A, [HL]"),
+ (sbc_a_a, 4, "SBC A, A"),
// 0xa opcodes
(and_a_b, 4, "AND A, B"),
(and_a_c, 4, "AND A, C"),
@@ -180,21 +183,21 @@ pub const INSTRUCTIONS: [(fn(&mut Cpu), u8, &'static str); 256] = [
(and_a_l, 4, "AND A, L"),
(and_a_mhl, 4, "AND A, [HL]"),
(and_a_a, 4, "AND A, A"),
- (noimpl, 4, "! UNIMP !"),
+ (xor_a_b, 4, "XOR A, B"),
(xor_a_c, 4, "XOR A, C"),
- (noimpl, 4, "! UNIMP !"),
- (noimpl, 4, "! UNIMP !"),
- (noimpl, 4, "! UNIMP !"),
+ (xor_a_d, 4, "XOR A, D"),
+ (xor_a_e, 4, "XOR A, E"),
+ (xor_a_h, 4, "XOR A, H"),
(xor_a_l, 4, "XOR A, L"),
(xor_a_mhl, 8, "XOR A, [HL]"),
(xor_a_a, 4, "XOR A, A"),
// 0xb opcodes
(or_a_b, 4, "OR A, B"),
(or_a_c, 4, "OR A, C"),
- (noimpl, 4, "! UNIMP !"),
- (noimpl, 4, "! UNIMP !"),
- (noimpl, 4, "! UNIMP !"),
- (noimpl, 4, "! UNIMP !"),
+ (or_a_d, 4, "OR A, D"),
+ (or_a_e, 4, "OR A, E"),
+ (or_a_h, 4, "OR A, H"),
+ (or_a_l, 4, "OR A, L"),
(or_a_mhl, 8, "OR A, [HL]"),
(or_a_a, 4, "OR A, A"),
(cp_a_b, 4, "CP A, B"),
@@ -248,7 +251,7 @@ pub const INSTRUCTIONS: [(fn(&mut Cpu), u8, &'static str); 256] = [
(push_hl, 16, "PUSH HL"),
(and_a_u8, 8, "AND A, u8"),
(rst_20h, 16, "RST 20h"),
- (noimpl, 4, "! UNIMP !"),
+ (add_sp_i8, 16, "ADD SP, i8"),
(jp_hl, 4, "JP HL"),
(ld_mu16_a, 16, "LD [u16], A"),
(illegal, 4, "ILLEGAL"),
@@ -259,7 +262,7 @@ pub const INSTRUCTIONS: [(fn(&mut Cpu), u8, &'static str); 256] = [
// 0xf opcodes
(ld_a_mff00u8, 12, "LD A, [FF00+u8]"),
(pop_af, 12, "POP AF"),
- (noimpl, 4, "! UNIMP !"),
+ (ld_a_mff00c, 8, "LD A, [FF00+C]"),
(di, 4, "DI"),
(illegal, 4, "ILLEGAL"),
(push_af, 16, "PUSH AF"),
@@ -277,14 +280,14 @@ pub const INSTRUCTIONS: [(fn(&mut Cpu), u8, &'static str); 256] = [
pub const EXTENDED: [(fn(&mut Cpu), u8, &'static str); 256] = [
// 0x0 opcodes
+ (rlc_b, 8, "RLC B"),
+ (rlc_c, 8, "RLC C"),
+ (rlc_d, 8, "RLC D"),
+ (rlc_e, 8, "RLC E"),
+ (rlc_h, 8, "RLC H"),
+ (rlc_l, 8, "RLC L"),
(noimpl, 4, "! UNIMP !"),
- (noimpl, 4, "! UNIMP !"),
- (noimpl, 4, "! UNIMP !"),
- (noimpl, 4, "! UNIMP !"),
- (noimpl, 4, "! UNIMP !"),
- (noimpl, 4, "! UNIMP !"),
- (noimpl, 4, "! UNIMP !"),
- (noimpl, 4, "! UNIMP !"),
+ (rlc_a, 8, "RLC A"),
(noimpl, 4, "! UNIMP !"),
(noimpl, 4, "! UNIMP !"),
(noimpl, 4, "! UNIMP !"),
@@ -553,6 +556,8 @@ pub const EXTENDED: [(fn(&mut Cpu), u8, &'static str); 256] = [
fn nop(_cpu: &mut Cpu) {}
fn noimpl(_cpu: &mut Cpu) {
+ let ten_millis = time::Duration::from_millis(10000);
+ thread::sleep(ten_millis); // @todo remove this hack
todo!("Instruction not implemented");
}
@@ -574,11 +579,12 @@ fn inc_bc(cpu: &mut Cpu) {
}
fn inc_b(cpu: &mut Cpu) {
- let value = cpu.b.wrapping_add(1);
+ let b = cpu.b;
+ let value = b.wrapping_add(1);
cpu.set_sub(false);
cpu.set_zero(value == 0);
- cpu.set_half_carry((value & 0xf) == 0xf);
+ cpu.set_half_carry((b & 0xf) == 0xf);
cpu.b = value;
}
@@ -631,11 +637,12 @@ fn dec_bc(cpu: &mut Cpu) {
}
fn inc_c(cpu: &mut Cpu) {
+ let c = cpu.c;
let value = cpu.c.wrapping_add(1);
cpu.set_sub(false);
cpu.set_zero(value == 0);
- cpu.set_half_carry((value & 0xf) == 0xf);
+ cpu.set_half_carry((c & 0xf) == 0xf);
cpu.c = value;
}
@@ -656,6 +663,16 @@ fn ld_c_u8(cpu: &mut Cpu) {
cpu.c = byte;
}
+fn rrca(cpu: &mut Cpu) {
+ let carry = cpu.a & 0x1;
+ cpu.a = (cpu.a >> 1) | (carry << 7);
+
+ cpu.set_sub(false);
+ cpu.set_zero(false);
+ cpu.set_half_carry(false);
+ cpu.set_carry(carry != 0x0);
+}
+
fn stop(cpu: &mut Cpu) {
cpu.stop();
}
@@ -674,11 +691,12 @@ fn inc_de(cpu: &mut Cpu) {
}
fn inc_d(cpu: &mut Cpu) {
- let value = cpu.d.wrapping_add(1);
+ let d = cpu.d;
+ let value = d.wrapping_add(1);
cpu.set_sub(false);
cpu.set_zero(value == 0);
- cpu.set_half_carry((value & 0xf) == 0xf);
+ cpu.set_half_carry((d & 0xf) == 0xf);
cpu.d = value;
}
@@ -731,11 +749,12 @@ fn dec_de(cpu: &mut Cpu) {
}
fn inc_e(cpu: &mut Cpu) {
+ let e = cpu.e;
let value = cpu.e.wrapping_add(1);
cpu.set_sub(false);
cpu.set_zero(value == 0);
- cpu.set_half_carry((value & 0xf) == 0xf);
+ cpu.set_half_carry((e & 0xf) == 0xf);
cpu.e = value;
}
@@ -794,11 +813,12 @@ fn inc_hl(cpu: &mut Cpu) {
}
fn inc_h(cpu: &mut Cpu) {
+ let h = cpu.h;
let value = cpu.h.wrapping_add(1);
cpu.set_sub(false);
cpu.set_zero(value == 0);
- cpu.set_half_carry((value & 0xf) == 0xf);
+ cpu.set_half_carry((h & 0xf) == 0xf);
cpu.h = value;
}
@@ -842,11 +862,12 @@ fn ld_a_mhli(cpu: &mut Cpu) {
}
fn inc_l(cpu: &mut Cpu) {
- let value = cpu.l.wrapping_add(1);
+ let l = cpu.l;
+ let value = l.wrapping_add(1);
cpu.set_sub(false);
cpu.set_zero(value == 0);
- cpu.set_half_carry((value & 0xf) == 0xf);
+ cpu.set_half_carry((l & 0xf) == 0xf);
cpu.l = value;
}
@@ -857,7 +878,7 @@ fn dec_l(cpu: &mut Cpu) {
cpu.set_sub(true);
cpu.set_zero(value == 0);
- cpu.set_half_carry((l & 0xf) == 0xf);
+ cpu.set_half_carry((l & 0xf) == 0x0);
cpu.l = value;
}
@@ -952,11 +973,12 @@ fn dec_sp(cpu: &mut Cpu) {
}
fn inc_a(cpu: &mut Cpu) {
- let value = cpu.a.wrapping_add(1);
+ let a = cpu.a;
+ let value = a.wrapping_add(1);
cpu.set_sub(false);
cpu.set_zero(value == 0);
- cpu.set_half_carry((value & 0xf) == 0xf);
+ cpu.set_half_carry((a & 0xf) == 0xf);
cpu.a = value;
}
@@ -977,6 +999,12 @@ fn ld_a_u8(cpu: &mut Cpu) {
cpu.a = byte;
}
+fn ccf(cpu: &mut Cpu) {
+ cpu.set_sub(false);
+ cpu.set_half_carry(false);
+ cpu.set_carry(!cpu.get_carry());
+}
+
fn ld_b_b(cpu: &mut Cpu) {
cpu.b = cpu.b;
}
@@ -1273,14 +1301,105 @@ fn add_a_a(cpu: &mut Cpu) {
cpu.a = add_set_flags(cpu, cpu.a, cpu.a);
}
+fn adc_a_b(cpu: &mut Cpu) {
+ cpu.a = add_carry_set_flags(cpu, cpu.a, cpu.b);
+}
+
+fn adc_a_c(cpu: &mut Cpu) {
+ cpu.a = add_carry_set_flags(cpu, cpu.a, cpu.c);
+}
+
+fn adc_a_d(cpu: &mut Cpu) {
+ cpu.a = add_carry_set_flags(cpu, cpu.a, cpu.d);
+}
+
+fn adc_a_e(cpu: &mut Cpu) {
+ cpu.a = add_carry_set_flags(cpu, cpu.a, cpu.e);
+}
+
+fn adc_a_h(cpu: &mut Cpu) {
+ cpu.a = add_carry_set_flags(cpu, cpu.a, cpu.h);
+}
+
+fn adc_a_l(cpu: &mut Cpu) {
+ cpu.a = add_carry_set_flags(cpu, cpu.a, cpu.l);
+}
+
+fn adc_a_mhl(cpu: &mut Cpu) {
+ let byte = cpu.mmu.read(cpu.hl());
+ cpu.a = add_carry_set_flags(cpu, cpu.a, byte);
+}
+
+fn adc_a_a(cpu: &mut Cpu) {
+ cpu.a = add_carry_set_flags(cpu, cpu.a, cpu.a);
+}
+
fn sub_a_b(cpu: &mut Cpu) {
cpu.a = sub_set_flags(cpu, cpu.a, cpu.b);
}
+fn sub_a_c(cpu: &mut Cpu) {
+ cpu.a = sub_set_flags(cpu, cpu.a, cpu.c);
+}
+
+fn sub_a_d(cpu: &mut Cpu) {
+ cpu.a = sub_set_flags(cpu, cpu.a, cpu.d);
+}
+
+fn sub_a_e(cpu: &mut Cpu) {
+ cpu.a = sub_set_flags(cpu, cpu.a, cpu.e);
+}
+
+fn sub_a_h(cpu: &mut Cpu) {
+ cpu.a = sub_set_flags(cpu, cpu.a, cpu.h);
+}
+
+fn sub_a_l(cpu: &mut Cpu) {
+ cpu.a = sub_set_flags(cpu, cpu.a, cpu.l);
+}
+
+fn sub_a_mhl(cpu: &mut Cpu) {
+ let byte = cpu.mmu.read(cpu.hl());
+ cpu.a = sub_set_flags(cpu, cpu.a, byte);
+}
+
fn sub_a_a(cpu: &mut Cpu) {
cpu.a = sub_set_flags(cpu, cpu.a, cpu.a);
}
+fn sbc_a_b(cpu: &mut Cpu) {
+ cpu.a = sub_carry_set_flags(cpu, cpu.a, cpu.b);
+}
+
+fn sbc_a_c(cpu: &mut Cpu) {
+ cpu.a = sub_carry_set_flags(cpu, cpu.a, cpu.c);
+}
+
+fn sbc_a_d(cpu: &mut Cpu) {
+ cpu.a = sub_carry_set_flags(cpu, cpu.a, cpu.d);
+}
+
+fn sbc_a_e(cpu: &mut Cpu) {
+ cpu.a = sub_carry_set_flags(cpu, cpu.a, cpu.e);
+}
+
+fn sbc_a_h(cpu: &mut Cpu) {
+ cpu.a = sub_carry_set_flags(cpu, cpu.a, cpu.h);
+}
+
+fn sbc_a_l(cpu: &mut Cpu) {
+ cpu.a = sub_carry_set_flags(cpu, cpu.a, cpu.l);
+}
+
+fn sbc_a_mhl(cpu: &mut Cpu) {
+ let byte = cpu.mmu.read(cpu.hl());
+ cpu.a = sub_carry_set_flags(cpu, cpu.a, byte);
+}
+
+fn sbc_a_a(cpu: &mut Cpu) {
+ cpu.a = sub_carry_set_flags(cpu, cpu.a, cpu.a);
+}
+
fn and_a_b(cpu: &mut Cpu) {
cpu.a &= cpu.b;
@@ -1354,6 +1473,15 @@ fn and_a_a(cpu: &mut Cpu) {
cpu.set_carry(false);
}
+fn xor_a_b(cpu: &mut Cpu) {
+ cpu.a ^= cpu.b;
+
+ cpu.set_sub(false);
+ cpu.set_zero(cpu.a == 0);
+ cpu.set_half_carry(false);
+ cpu.set_carry(false);
+}
+
fn xor_a_c(cpu: &mut Cpu) {
cpu.a ^= cpu.c;
@@ -1363,6 +1491,33 @@ fn xor_a_c(cpu: &mut Cpu) {
cpu.set_carry(false);
}
+fn xor_a_d(cpu: &mut Cpu) {
+ cpu.a ^= cpu.d;
+
+ cpu.set_sub(false);
+ cpu.set_zero(cpu.a == 0);
+ cpu.set_half_carry(false);
+ cpu.set_carry(false);
+}
+
+fn xor_a_e(cpu: &mut Cpu) {
+ cpu.a ^= cpu.e;
+
+ cpu.set_sub(false);
+ cpu.set_zero(cpu.a == 0);
+ cpu.set_half_carry(false);
+ cpu.set_carry(false);
+}
+
+fn xor_a_h(cpu: &mut Cpu) {
+ cpu.a ^= cpu.h;
+
+ cpu.set_sub(false);
+ cpu.set_zero(cpu.a == 0);
+ cpu.set_half_carry(false);
+ cpu.set_carry(false);
+}
+
fn xor_a_l(cpu: &mut Cpu) {
cpu.a ^= cpu.l;
@@ -1409,6 +1564,42 @@ fn or_a_c(cpu: &mut Cpu) {
cpu.set_carry(false);
}
+fn or_a_d(cpu: &mut Cpu) {
+ cpu.a |= cpu.d;
+
+ cpu.set_sub(false);
+ cpu.set_zero(cpu.a == 0);
+ cpu.set_half_carry(false);
+ cpu.set_carry(false);
+}
+
+fn or_a_e(cpu: &mut Cpu) {
+ cpu.a |= cpu.e;
+
+ cpu.set_sub(false);
+ cpu.set_zero(cpu.a == 0);
+ cpu.set_half_carry(false);
+ cpu.set_carry(false);
+}
+
+fn or_a_h(cpu: &mut Cpu) {
+ cpu.a |= cpu.h;
+
+ cpu.set_sub(false);
+ cpu.set_zero(cpu.a == 0);
+ cpu.set_half_carry(false);
+ cpu.set_carry(false);
+}
+
+fn or_a_l(cpu: &mut Cpu) {
+ cpu.a |= cpu.l;
+
+ cpu.set_sub(false);
+ cpu.set_zero(cpu.a == 0);
+ cpu.set_half_carry(false);
+ cpu.set_carry(false);
+}
+
fn or_a_mhl(cpu: &mut Cpu) {
let byte = cpu.mmu.read(cpu.hl());
cpu.a |= byte;
@@ -1696,6 +1887,21 @@ fn rst_20h(cpu: &mut Cpu) {
rst(cpu, 0x0020);
}
+fn add_sp_i8(cpu: &mut Cpu) {
+ let sp = cpu.sp as i32;
+ let byte = cpu.read_u8() as i8;
+ let byte_i32 = byte as i32;
+
+ let result = sp.wrapping_add(byte_i32);
+
+ cpu.set_sub(false);
+ cpu.set_zero(false);
+ cpu.set_half_carry((sp ^ byte_i32 ^ result) & 0x10 == 0x10);
+ cpu.set_carry((sp ^ byte_i32 ^ result) & 0x100 == 0x100);
+
+ cpu.sp = result as u16;
+}
+
fn jp_hl(cpu: &mut Cpu) {
cpu.pc = cpu.hl();
}
@@ -1729,6 +1935,10 @@ fn pop_af(cpu: &mut Cpu) {
cpu.set_af(word);
}
+fn ld_a_mff00c(cpu: &mut Cpu) {
+ cpu.a = cpu.mmu.read(0xff00 + cpu.c as u16);
+}
+
fn di(cpu: &mut Cpu) {
cpu.disable_int();
}
@@ -1774,6 +1984,34 @@ fn rst_38h(cpu: &mut Cpu) {
rst(cpu, 0x0038);
}
+fn rlc_b(cpu: &mut Cpu) {
+ cpu.b = rlc(cpu, cpu.b);
+}
+
+fn rlc_c(cpu: &mut Cpu) {
+ cpu.c = rlc(cpu, cpu.c);
+}
+
+fn rlc_d(cpu: &mut Cpu) {
+ cpu.d = rlc(cpu, cpu.d);
+}
+
+fn rlc_e(cpu: &mut Cpu) {
+ cpu.e = rlc(cpu, cpu.e);
+}
+
+fn rlc_h(cpu: &mut Cpu) {
+ cpu.h = rlc(cpu, cpu.h);
+}
+
+fn rlc_l(cpu: &mut Cpu) {
+ cpu.l = rlc(cpu, cpu.l);
+}
+
+fn rlc_a(cpu: &mut Cpu) {
+ cpu.a = rlc(cpu, cpu.a);
+}
+
fn rl_c(cpu: &mut Cpu) {
cpu.c = rl(cpu, cpu.c);
}
@@ -1863,6 +2101,18 @@ fn rl(cpu: &mut Cpu, value: u8) -> u8 {
result
}
+fn rlc(cpu: &mut Cpu, value: u8) -> u8 {
+ cpu.set_carry(value & 0x80 == 0x80);
+
+ let result = (value << 1) | (value >> 7);
+
+ cpu.set_sub(false);
+ cpu.set_zero(result == 0);
+ cpu.set_half_carry(false);
+
+ result
+}
+
/// Helper function that rotates (shifts) right the given
/// byte (probably from a register) and updates the
/// proper flag registers.
--
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