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feat(cpu): Pass all LDR/STR ARMwrestler tests

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This commit is contained in:
Rekai Nyangadzayi Musuka
2022-02-02 14:00:43 -04:00
parent 30bad76e44
commit 237beb9caa
3 changed files with 16 additions and 30 deletions
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24
src/cpu/arm/single_data_transfer.zig
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@@ -20,19 +20,20 @@ pub fn singleDataTransfer(comptime I: bool, comptime P: bool, comptime U: bool,
base = cpu.r[rn];
}
const offset = if (I) registerOffset(cpu, opcode) else opcode & 0xFFF;
const offset = if (I) shifter.immShift(false, cpu, opcode) else opcode & 0xFFF;
const modified_base = if (U) base + offset else base - offset;
const modified_base = if (U) base +% offset else base -% offset;
var address = if (P) modified_base else base;
var result: u32 = undefined;
if (L) {
if (B) {
// LDRB
cpu.r[rd] = bus.read8(address);
result = bus.read8(address);
} else {
// LDR
const value = bus.read32(address & 0xFFFF_FFFC);
cpu.r[rd] = std.math.rotr(u32, value, 8 * (address & 0x3));
result = std.math.rotr(u32, value, 8 * (address & 0x3));
}
} else {
if (B) {
@@ -47,20 +48,7 @@ pub fn singleDataTransfer(comptime I: bool, comptime P: bool, comptime U: bool,
address = modified_base;
if (W and P or !P) cpu.r[rn] = address;
// TODO: W-bit forces non-privledged mode for the transfer
if (L) cpu.r[rd] = result; // This emulates the LDR rd == rn behaviour
}
}.inner;
}
fn registerOffset(cpu: *Arm7tdmi, opcode: u32) u32 {
const amount = @truncate(u8, opcode >> 7 & 0x1F);
const rm = cpu.r[opcode & 0xF];
return switch (@truncate(u2, opcode >> 5)) {
0b00 => shifter.logicalLeft(false, &cpu.cpsr, rm, amount),
0b01 => shifter.logicalRight(false, &cpu.cpsr, rm, amount),
0b10 => shifter.arithmeticRight(false, &cpu.cpsr, rm, amount),
0b11 => shifter.rotateRight(false, &cpu.cpsr, rm, amount),
};
}