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fix: resolve decoding mixup in THUMB format 8 instructions

This commit is contained in:
Rekai Nyangadzayi Musuka 2022-02-05 14:50:34 -04:00
parent 3a51707280
commit 5ec8d4b0a5
1 changed files with 6 additions and 4 deletions
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10
src/cpu/thumb/data_transfer.zig
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@ -28,26 +28,28 @@ pub fn format78(comptime op: u2, comptime T: bool) InstrFn {
const address = cpu.r[rb] + cpu.r[ro]; const address = cpu.r[rb] + cpu.r[ro];
if (T) { if (T) {
// Format 8
switch (op) { switch (op) {
0b00 => { 0b00 => {
// STRH // STRH
bus.write16(address & 0xFFFF_FFFE, @truncate(u16, cpu.r[rd])); bus.write16(address & 0xFFFF_FFFE, @truncate(u16, cpu.r[rd]));
}, },
0b01 => { 0b01 => {
// LDSB
cpu.r[rd] = u32SignExtend(8, @as(u32, bus.read8(address)));
},
0b10 => {
// LDRH // LDRH
const value = bus.read16(address & 0xFFFF_FFFE); const value = bus.read16(address & 0xFFFF_FFFE);
cpu.r[rd] = std.math.rotr(u32, @as(u32, value), 8 * (address & 1)); cpu.r[rd] = std.math.rotr(u32, @as(u32, value), 8 * (address & 1));
}, },
0b10 => {
// LDSB
cpu.r[rd] = u32SignExtend(8, @as(u32, bus.read8(address)));
},
0b11 => { 0b11 => {
// LDSH // LDSH
cpu.r[rd] = u32SignExtend(16, @as(u32, bus.read16(address & 0xFFFF_FFFE))); cpu.r[rd] = u32SignExtend(16, @as(u32, bus.read16(address & 0xFFFF_FFFE)));
}, },
} }
} else { } else {
// Format 7
switch (op) { switch (op) {
0b00 => { 0b00 => {
// STR // STR