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chore(cpu): refactor barrel shifter

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This commit is contained in:
Rekai Nyangadzayi Musuka
2022-01-17 11:17:04 -04:00
parent d05a924420
commit 1025500407
3 changed files with 31 additions and 55 deletions
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14
src/cpu/arm/single_data_transfer.zig
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@@ -4,7 +4,6 @@ const util = @import("../../util.zig");
const BarrelShifter = @import("barrel_shifter.zig");
const Bus = @import("../../Bus.zig");
const Arm7tdmi = @import("../../cpu.zig").Arm7tdmi;
const CPSR = @import("../../cpu.zig").PSR;
const InstrFn = @import("../../cpu.zig").ArmInstrFn;
pub fn singleDataTransfer(comptime I: bool, comptime P: bool, comptime U: bool, comptime B: bool, comptime W: bool, comptime L: bool) InstrFn {
@@ -55,16 +54,13 @@ pub fn singleDataTransfer(comptime I: bool, comptime P: bool, comptime U: bool,
}
fn registerOffset(cpu: *Arm7tdmi, opcode: u32) u32 {
const shift_byte = @truncate(u8, opcode >> 7 & 0x1F);
const amount = @truncate(u8, opcode >> 7 & 0x1F);
const rm = cpu.r[opcode & 0xF];
var dummy = CPSR{ .raw = 0x0000_0000 };
return switch (@truncate(u2, opcode >> 5)) {
0b00 => BarrelShifter.logicalLeft(&dummy, rm, shift_byte),
0b01 => BarrelShifter.logicalRight(&dummy, rm, shift_byte),
0b10 => BarrelShifter.arithmetic_right(&dummy, rm, shift_byte),
0b11 => BarrelShifter.rotateRight(&dummy, rm, shift_byte),
0b00 => BarrelShifter.logicalLeft(false, &cpu.cpsr, rm, amount),
0b01 => BarrelShifter.logicalRight(false, &cpu.cpsr, rm, amount),
0b10 => BarrelShifter.arithmeticRight(false, &cpu.cpsr, rm, amount),
0b11 => BarrelShifter.rotateRight(false, &cpu.cpsr, rm, amount),
};
}