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chore(cpu): implement behaviour for undefined test instruction

This commit is contained in:
Rekai Nyangadzayi Musuka 2022-01-25 08:05:42 -04:00
parent 95dd3e3df8
commit 985fefb9f6
1 changed files with 25 additions and 0 deletions
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25
src/cpu/arm/data_processing.zig
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@ -83,16 +83,31 @@ pub fn dataProcessing(comptime I: bool, comptime S: bool, comptime instrKind: u4
0x7 => cpu.r[rd] = sbc(S, cpu, rd, op2, op1, old_carry), // RSC
0x8 => {
// TST
if (rd == 0xF) {
undefinedTestBehaviour(cpu);
return;
}
const result = op1 & op2;
testFlags(S, cpu, opcode, result);
},
0x9 => {
// TEQ
if (rd == 0xF) {
undefinedTestBehaviour(cpu);
return;
}
const result = op1 ^ op2;
testFlags(S, cpu, opcode, result);
},
0xA => {
// CMP
if (rd == 0xF) {
undefinedTestBehaviour(cpu);
return;
}
const result = op1 -% op2;
cpu.cpsr.n.write(result >> 31 & 1 == 1);
@ -102,6 +117,11 @@ pub fn dataProcessing(comptime I: bool, comptime S: bool, comptime instrKind: u4
},
0xB => {
// CMN
if (rd == 0xF) {
undefinedTestBehaviour(cpu);
return;
}
var result: u32 = undefined;
const didOverflow = @addWithOverflow(u32, op1, op2, &result);
@ -192,3 +212,8 @@ fn testFlags(comptime S: bool, cpu: *Arm7tdmi, opcode: u32, result: u32) void {
// Barrel Shifter should always calc CPSR C in TST
if (!S) _ = shifter.execute(true, cpu, opcode);
}
fn undefinedTestBehaviour(cpu: *Arm7tdmi) void {
@setCold(true);
cpu.setCpsr(cpu.spsr.raw);
}