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paoda:april-fools
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compare: paoda:c6bb4bf8e179ea2771e4bde781e45596f9808bd4
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paoda:april-fools
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2 changed files with 8 additions and 14 deletions
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2
src/cpu.zig
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@ -453,7 +453,7 @@ fn thumbPopulate() [0x400]ThumbInstrFn {
lut[i] = format6(rd);
} else if (i >> 6 & 0xF == 0b0101) {
const op = i >> 4 & 0x3;
const op = i >> 5 & 0x3;
const T = i >> 3 & 1 == 1;
lut[i] = format78(op, T);

20
src/cpu/thumb/format5.zig
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@ -10,23 +10,17 @@ 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 = if (src_idx == 0xF) (cpu.r[src_idx] + 2) & 0xFFFF_FFFE else cpu.r[src_idx];
const dst = if (dst_idx == 0xF) (cpu.r[dst_idx] + 2) & 0xFFFF_FFFE else cpu.r[dst_idx];
const src = @as(u4, h2) << 3 | (opcode >> 3 & 0x7);
const dst = @as(u4, h1) << 3 | (opcode & 0x7);
switch (op) {
0b00 => cpu.r[dst_idx] = add(false, cpu, dst, src) & if (dst_idx == 0xF) 0xFFFF_FFFC else @as(u32, 0xFFF_FFFF), // ADD
0b01 => cmp(cpu, dst, src), // CMP
0b10 => {
// MOV
cpu.r[dst_idx] = if (dst_idx == 0xF) src & 0xFFFF_FFFC else src;
},
0b00 => cpu.r[dst] = add(false, cpu, cpu.r[dst], cpu.r[src]), // ADD
0b01 => cmp(cpu, cpu.r[dst], cpu.r[src]), // CMP
0b10 => cpu.r[dst] = cpu.r[src], // MOV
0b11 => {
// BX
cpu.cpsr.t.write(src & 1 == 1);
cpu.r[15] = src & 0xFFFF_FFFE;
cpu.cpsr.t.write(cpu.r[src] & 1 == 1);
cpu.r[15] = cpu.r[src] & 0xFFFF_FFFE;
},
}
}