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fix(cpu): improve LDR/STR write-back logic

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This commit is contained in:
Rekai Nyangadzayi Musuka
2022-01-04 03:55:41 -06:00
parent 5ea888f68c
commit 28bb410dfd
2 changed files with 7 additions and 8 deletions
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13
src/cpu/half_signed_data_transfer.zig
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@@ -34,18 +34,17 @@ pub fn comptimeHalfSignedDataTransfer(comptime P: bool, comptime U: bool, compti
}, },
0b01 => { 0b01 => {
// LDRH // LDRH
const halfword = bus.read16(address); cpu.r[rd] = bus.read16(address);
cpu.r[rd] = @as(u32, halfword);
}, },
0b10 => { 0b10 => {
// LDRSB // LDRSB
const byte = bus.read8(address); cpu.r[rd] = util.u32SignExtend(8, @as(u32, bus.read8(address)));
cpu.r[rd] = util.u32SignExtend(8, @as(u32, byte)); std.debug.panic("TODO: Affect the CPSR", .{});
}, },
0b11 => { 0b11 => {
// LDRSH // LDRSH
const halfword = bus.read16(address); cpu.r[rd] = util.u32SignExtend(16, @as(u32, bus.read16(address)));
cpu.r[rd] = util.u32SignExtend(16, @as(u32, halfword)); std.debug.panic("TODO: Affect the CPSR", .{});
}, },
} }
} else { } else {
@@ -58,7 +57,7 @@ pub fn comptimeHalfSignedDataTransfer(comptime P: bool, comptime U: bool, compti
} }
address = modified_base; address = modified_base;
if (W and P) cpu.r[rn] = address; if (W and P or !P) cpu.r[rn] = address;
} }
}.halfSignedDataTransfer; }.halfSignedDataTransfer;
} }

2
src/cpu/single_data_transfer.zig
View File

@@ -40,7 +40,7 @@ pub fn comptimeSingleDataTransfer(comptime I: bool, comptime P: bool, comptime U
} }
address = modified_base; address = modified_base;
if (W and P or !W) cpu.r[rn] = address; if (W and P or !P) cpu.r[rn] = address;
// TODO: W-bit forces non-privledged mode for the transfer // TODO: W-bit forces non-privledged mode for the transfer
} }