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fix(cpu): properly implement SUB/CMP CSPSR carry bit condition

This commit is contained in:
Rekai Nyangadzayi Musuka 2022-01-04 02:42:40 -06:00
parent 8cabcd8901
commit ed9c1413b1
1 changed files with 4 additions and 6 deletions
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10
src/cpu/data_processing.zig
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@ -33,17 +33,15 @@ pub fn comptimeDataProcessing(comptime I: bool, comptime S: bool, comptime instr
}, },
0xA => { 0xA => {
// CMP // CMP
var result: u32 = undefined;
const op1_val = cpu.r[op1]; const op1_val = cpu.r[op1];
const v_ctx = (op1_val >> 31 == 0x01) or (op2 >> 31 == 0x01); const v_ctx = (op1_val >> 31 == 0x01) or (op2 >> 31 == 0x01);
const didOverflow = @subWithOverflow(u32, op1_val, op2, &result); const result = op1_val -% op2;
cpu.cpsr.v.write(v_ctx and (result >> 31 & 0x01 == 0x01));
cpu.cpsr.c.write(didOverflow);
cpu.cpsr.z.write(result == 0x00);
cpu.cpsr.n.write(result >> 31 & 0x01 == 0x01); cpu.cpsr.n.write(result >> 31 & 0x01 == 0x01);
cpu.cpsr.z.write(result == 0x00);
cpu.cpsr.c.write(op2 <= op1_val);
cpu.cpsr.v.write(v_ctx and (result >> 31 & 0x01 == 0x01));
}, },
else => std.debug.panic("[CPU] TODO: implement data processing type {}", .{instrKind}), else => std.debug.panic("[CPU] TODO: implement data processing type {}", .{instrKind}),
} }