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feat(cpu): implement some already decoded format 3 instructions

This commit is contained in:
Rekai Nyangadzayi Musuka 2022-01-17 09:29:11 -04:00
parent e55d2dc323
commit ea5f0ce552
1 changed files with 19 additions and 2 deletions
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21
src/cpu/thumb/format3.zig
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@ -11,16 +11,33 @@ pub fn format3(comptime op: u2, comptime rd: u3) InstrFn {
switch (op) {
0b00 => {
// MOV
cpu.r[rd] = offset;
cpu.cpsr.n.unset();
cpu.cpsr.z.write(offset == 0);
},
0b01 => {
std.debug.panic("TODO: Implement cmp R{}, #0x{X:0>2}", .{ rd, offset });
// CMP
const left = cpu.r[rd];
const result = left -% offset;
cpu.cpsr.n.write(result >> 31 & 1 == 1);
cpu.cpsr.z.write(result == 0);
cpu.cpsr.c.write(offset <= left);
cpu.cpsr.v.write(((left ^ result) & (~offset ^ result)) >> 31 & 1 == 1);
},
0b10 => {
std.debug.panic("TODO: Implement add R{}, #0x{X:0>2}", .{ rd, offset });
const left = cpu.r[rd];
var result: u32 = undefined;
const didOverflow = @addWithOverflow(u32, left, offset, &result);
cpu.r[rd] = result;
cpu.cpsr.n.write(result >> 31 & 1 == 1);
cpu.cpsr.z.write(result == 0);
cpu.cpsr.c.write(didOverflow);
cpu.cpsr.v.write(((left ^ result) & (offset ^ result)) >> 31 & 1 == 1);
},
0b11 => {
std.debug.panic("TODO: Implement sub R{}, #0x{X:0>2}", .{ rd, offset });