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feat(cpu): Implement RSC

This commit is contained in:
Rekai Nyangadzayi Musuka 2022-01-18 14:46:40 -04:00
parent 212bc9e11d
commit 8d786cbe25
1 changed files with 16 additions and 15 deletions
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31
src/cpu/arm/data_processing.zig
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@ -74,20 +74,8 @@ pub fn dataProcessing(comptime I: bool, comptime S: bool, comptime instrKind: u4
cpu.cpsr.v.write(((op1 ^ result) & (op2 ^ result)) >> 31 & 1 == 1); cpu.cpsr.v.write(((op1 ^ result) & (op2 ^ result)) >> 31 & 1 == 1);
} }
}, },
0x6 => { 0x6 => sbc(S, cpu, rd, op1, op2, old_carry), // SBC
// SBC 0x7 => sbc(S, cpu, rd, op2, op1, old_carry), // RSC
// TODO: Make your own
const subtrahend = @as(u64, op2) - old_carry + 1;
const result = @truncate(u32, op1 -% subtrahend);
cpu.r[rd] = result;
if (S and rd != 0xF) {
cpu.cpsr.n.write(result >> 31 & 1 == 1);
cpu.cpsr.z.write(result == 0);
cpu.cpsr.c.write(subtrahend <= op1);
cpu.cpsr.v.write(((op1 ^ result) & (~op2 ^ result)) >> 31 & 1 == 1);
}
},
0x8 => { 0x8 => {
// TST // TST
const result = op1 & op2; const result = op1 & op2;
@ -158,12 +146,25 @@ pub fn dataProcessing(comptime I: bool, comptime S: bool, comptime instrKind: u4
// C set by Barrel Shifter, V is unaffected // C set by Barrel Shifter, V is unaffected
} }
}, },
else => std.debug.panic("[CPU] TODO: implement data processing type {}", .{instrKind}),
} }
} }
}.inner; }.inner;
} }
fn sbc(comptime S: bool, cpu: *Arm7tdmi, rd: u4, left: u32, right: u32, old_carry: u1) void {
// TODO: Make your own version (thanks peach.bot)
const subtrahend = @as(u64, right) - old_carry + 1;
const result = @truncate(u32, left -% subtrahend);
cpu.r[rd] = result;
if (S and rd != 0xF) {
cpu.cpsr.n.write(result >> 31 & 1 == 1);
cpu.cpsr.z.write(result == 0);
cpu.cpsr.c.write(subtrahend <= left);
cpu.cpsr.v.write(((left ^ result) & (~right ^ result)) >> 31 & 1 == 1);
}
}
fn sub(comptime S: bool, cpu: *Arm7tdmi, rd: u4, left: u32, right: u32) void { fn sub(comptime S: bool, cpu: *Arm7tdmi, rd: u4, left: u32, right: u32) void {
const result = left -% right; const result = left -% right;
cpu.r[rd] = result; cpu.r[rd] = result;