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feat(cpu): implement SUB in THUMB format 3

This commit is contained in:
Rekai Nyangadzayi Musuka 2022-01-17 11:36:02 -04:00
parent 9098a55ae3
commit 85ffdf44f5
1 changed files with 10 additions and 1 deletions
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11
src/cpu/thumb/format3.zig
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@ -28,6 +28,7 @@ pub fn format3(comptime op: u2, comptime rd: u3) InstrFn {
cpu.cpsr.v.write(((left ^ result) & (~offset ^ result)) >> 31 & 1 == 1);
},
0b10 => {
// ADD
const left = cpu.r[rd];
var result: u32 = undefined;
@ -40,7 +41,15 @@ pub fn format3(comptime op: u2, comptime rd: u3) InstrFn {
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 });
// SUB
const left = cpu.r[rd];
const result = left -% offset;
cpu.r[rd] = result;
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);
},
}
}