zba/src/cpu/thumb/processing_branch.zig
Rekai Musuka 5ee9afcc2c feat: implement basic pipeline
passes arm.gba, thumb.gb and armwrestler, fails in actual games
TODO: run FuzzARM debug specific titles
2022-07-13 03:17:49 -03:00

43 lines
1.5 KiB
Zig

const Bus = @import("../../Bus.zig");
const Arm7tdmi = @import("../../cpu.zig").Arm7tdmi;
const InstrFn = @import("../../cpu.zig").ThumbInstrFn;
const cmp = @import("../arm/data_processing.zig").cmp;
const add = @import("../arm/data_processing.zig").add;
pub fn format5(comptime op: u2, comptime h1: u1, comptime h2: u1) InstrFn {
return struct {
fn inner(cpu: *Arm7tdmi, _: *Bus, opcode: u16) void {
const src_idx = @as(u4, h2) << 3 | (opcode >> 3 & 0x7);
const dst_idx = @as(u4, h1) << 3 | (opcode & 0x7);
const src_mask = if (src_idx == 0xF) ~@as(u32, 1) else ~@as(u32, 0);
const dst_mask = if (dst_idx == 0xF) ~@as(u32, 1) else ~@as(u32, 0);
const src = cpu.r[src_idx] & src_mask;
const dst = cpu.r[dst_idx] & dst_mask;
switch (op) {
0b00 => {
// ADD
const sum = add(false, cpu, dst, src);
cpu.r[dst_idx] = sum & dst_mask;
},
0b01 => cmp(cpu, dst, src), // CMP
0b10 => {
// MOV
cpu.r[dst_idx] = src & dst_mask;
},
0b11 => {
// BX
cpu.cpsr.t.write(src & 1 == 1);
cpu.r[15] = src & ~@as(u32, 1);
cpu.pipe.flush();
},
}
if (dst_idx == 0xF) cpu.pipe.flush();
}
}.inner;
}