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fix(cpu): make Data Processing instructions r15-aware

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This commit is contained in:
Rekai Nyangadzayi Musuka
2022-01-12 06:54:22 -04:00
parent 229f7c3388
commit 7adc7c8802
2 changed files with 31 additions and 20 deletions
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22
src/cpu/barrel_shifter.zig
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@@ -12,21 +12,27 @@ pub fn exec(comptime S: bool, cpu: *Arm7tdmi, opcode: u32) u32 {
}
const rm = cpu.r[opcode & 0xF];
var value: u32 = undefined;
if (rm == 0xF) {
value = cpu.fakePC() + 4; // 12 ahead
} else {
value = cpu.r[opcode & 0xF];
}
if (S) {
return switch (@truncate(u2, opcode >> 5)) {
0b00 => logical_left(&cpu.cpsr, rm, shift_amt),
0b01 => logical_right(&cpu.cpsr, rm, shift_amt),
0b10 => arithmetic_right(&cpu.cpsr, rm, shift_amt),
0b11 => rotate_right(&cpu.cpsr, rm, shift_amt),
0b00 => logical_left(&cpu.cpsr, value, shift_amt),
0b01 => logical_right(&cpu.cpsr, value, shift_amt),
0b10 => arithmetic_right(&cpu.cpsr, value, shift_amt),
0b11 => rotate_right(&cpu.cpsr, value, shift_amt),
};
} else {
var dummy = CPSR{ .raw = 0x0000_0000 };
return switch (@truncate(u2, opcode >> 5)) {
0b00 => logical_left(&dummy, rm, shift_amt),
0b01 => logical_right(&dummy, rm, shift_amt),
0b10 => arithmetic_right(&dummy, rm, shift_amt),
0b11 => rotate_right(&dummy, rm, shift_amt),
0b00 => logical_left(&dummy, value, shift_amt),
0b01 => logical_right(&dummy, value, shift_amt),
0b10 => arithmetic_right(&dummy, value, shift_amt),
0b11 => rotate_right(&dummy, value, shift_amt),
};
}
}