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fix(cpu): use barrel shifter in data processing immediates

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This commit is contained in:
Rekai Nyangadzayi Musuka
2022-01-17 11:02:34 -04:00
parent 2a416fb2c6
commit d05a924420
3 changed files with 31 additions and 15 deletions
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27
src/cpu/arm/barrel_shifter.zig
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@@ -21,23 +21,23 @@ pub fn exec(comptime S: bool, cpu: *Arm7tdmi, opcode: u32) u32 {
if (S) {
return switch (@truncate(u2, opcode >> 5)) {
0b00 => logical_left(&cpu.cpsr, value, shift_amt),
0b01 => logical_right(&cpu.cpsr, value, shift_amt),
0b00 => logicalLeft(&cpu.cpsr, value, shift_amt),
0b01 => logicalRight(&cpu.cpsr, value, shift_amt),
0b10 => arithmetic_right(&cpu.cpsr, value, shift_amt),
0b11 => rotate_right(&cpu.cpsr, value, shift_amt),
0b11 => rotateRight(&cpu.cpsr, value, shift_amt),
};
} else {
var dummy = CPSR{ .raw = 0x0000_0000 };
return switch (@truncate(u2, opcode >> 5)) {
0b00 => logical_left(&dummy, value, shift_amt),
0b01 => logical_right(&dummy, value, shift_amt),
0b00 => logicalLeft(&dummy, value, shift_amt),
0b01 => logicalRight(&dummy, value, shift_amt),
0b10 => arithmetic_right(&dummy, value, shift_amt),
0b11 => rotate_right(&dummy, value, shift_amt),
0b11 => rotateRight(&dummy, value, shift_amt),
};
}
}
pub fn logical_left(cpsr: *CPSR, rm: u32, shift_byte: u8) u32 {
pub fn logicalLeft(cpsr: *CPSR, rm: u32, shift_byte: u8) u32 {
const shift_amt = @truncate(u5, shift_byte);
const bit_count: u8 = @typeInfo(u32).Int.bits;
@@ -64,7 +64,7 @@ pub fn logical_left(cpsr: *CPSR, rm: u32, shift_byte: u8) u32 {
return result;
}
pub fn logical_right(cpsr: *CPSR, rm: u32, shift_byte: u8) u32 {
pub fn logicalRight(cpsr: *CPSR, rm: u32, shift_byte: u8) u32 {
const shift_amt = @truncate(u5, shift_byte);
const bit_count: u8 = @typeInfo(u32).Int.bits;
@@ -92,7 +92,12 @@ pub fn arithmetic_right(_: *CPSR, _: u32, _: u8) u32 {
std.debug.panic("[BarrelShifter] implement arithmetic shift right", .{});
}
pub fn rotate_right(_: *CPSR, _: u32, _: u8) u32 {
// std.math.rotr(u32, r_val, amount)
std.debug.panic("[BarrelShifter] implement rotate right", .{});
pub fn rotateRight(cpsr: *CPSR, rm: u32, shift_byte: u8) u32 {
const result = std.math.rotr(u32, rm, shift_byte);
if (result != 0) {
cpsr.c.write(result >> 31 & 1 == 1);
}
return result;
}