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authoriximeow <me@iximeow.net>2020-12-06 02:07:02 -0800
committeriximeow <me@iximeow.net>2020-12-06 11:58:57 -0800
commitc2874f05ab0f92bbcc4c5129dbec14157af32c56 (patch)
treefd56fa6a37b36dcce3eecc99f8e37791cefb0aab /src/armv7/thumb.rs
parent268f54ec676666467fdceda5e86d89ea27d211b8 (diff)
numerous one-off mis-specializations, most of ld/prefetch hints
Diffstat (limited to 'src/armv7/thumb.rs')
-rw-r--r--src/armv7/thumb.rs563
1 files changed, 547 insertions, 16 deletions
diff --git a/src/armv7/thumb.rs b/src/armv7/thumb.rs
index bf492df..c78842d 100644
--- a/src/armv7/thumb.rs
+++ b/src/armv7/thumb.rs
@@ -137,7 +137,7 @@ pub fn decode_into<T: IntoIterator<Item=u8>>(decoder: &InstDecoder, inst: &mut I
// TODO: double check
if op2[2] {
// `Load/store dual, load/store exclusive, table branch` (`A6-236`)
- let op1op2 = (instr2[5..7].load::<u8>() << 2) | instr2[4..6].load::<u8>();
+ let op1op2 = (instr2[7..9].load::<u8>() << 2) | instr2[4..6].load::<u8>();
let imm8 = lower2[..8].load::<u16>();
let rd = lower2[8..12].load::<u8>();
let rt = lower2[12..16].load::<u8>();
@@ -436,8 +436,7 @@ pub fn decode_into<T: IntoIterator<Item=u8>>(decoder: &InstDecoder, inst: &mut I
0b1110 => {
// `STRD (immediate)` (`A8-687`)
// v6T2
- // bit 5 (w) == 1
- let w = true;
+ let w = instr2[5];
let u = instr2[7];
let p = instr2[8];
// `if P == '0' && W == '0' then SEE "Related encodings"` -> this
@@ -464,8 +463,7 @@ pub fn decode_into<T: IntoIterator<Item=u8>>(decoder: &InstDecoder, inst: &mut I
0b1111 => {
// `LDRD (immediate)` (`A8-687`)
// v6T2
- // bit 5 (w) == 1
- let w = true;
+ let w = instr2[5];
let u = instr2[7];
let p = instr2[8];
// `if P == '0' && W == '0' then SEE "Related encodings"` -> this
@@ -484,10 +482,10 @@ pub fn decode_into<T: IntoIterator<Item=u8>>(decoder: &InstDecoder, inst: &mut I
Operand::Reg(Reg::from_u8(rt)),
Operand::Reg(Reg::from_u8(rd)),
if p {
- Operand::RegDerefPostindexOffset(Reg::from_u8(rn), imm8 << 2, u, w)
+ Operand::RegDerefPreindexOffset(Reg::from_u8(rn), imm8 << 2, u, w)
} else {
// p == 0 and w == 0 is impossible, would be tbb/tbh
- Operand::RegDerefPreindexOffset(Reg::from_u8(rn), imm8 << 2, u, false)
+ Operand::RegDerefPostindexOffset(Reg::from_u8(rn), imm8 << 2, u, false)
},
Operand::Nothing,
];
@@ -1012,6 +1010,7 @@ pub fn decode_into<T: IntoIterator<Item=u8>>(decoder: &InstDecoder, inst: &mut I
0b0001 => {
// `BIC` (`A8-338`)
// v6T2
+ inst.set_w(false);
inst.opcode = Opcode::BIC;
inst.operands = [
Operand::Reg(Reg::from_u8(rd)),
@@ -2178,18 +2177,550 @@ pub fn decode_into<T: IntoIterator<Item=u8>>(decoder: &InstDecoder, inst: &mut I
// (`A7-273`)
}
} else {
- // load {byte, halfword, word}
- let size_bits = (op2[1..].load::<u8>());
- if size_bits == 0b00 {
- // `Load byte, memory hints` (`A6-239`)
- } else if size_bits == 0b01 {
- // `Load halfword, memory hints` (`A6-238`)
- } else if size_bits == 0b10 {
- // `Load word` (`A6-237`)
- } else {
+ // this section is a merger of three tables:
+ // `A6.3.9 Load byte, memory hints`
+ // `A6.3.8 Load halfword, memory hints`
+ // `A6.3.7 Load word`
+ // reached by the `00xx001`, `00xx011`, `00xx101` rows of table `A6-9`.
+
+ let op2 = lower2[6..12].load::<u16>();
+ let rt = lower2[12..16].load::<u8>();
+ let rn = instr2[0..4].load::<u8>();
+ let op1 = instr2[7..9].load::<u16>();
+
+ // load {byte, halfword, word} in table `A6-9`
+ let size = instr2[5..7].load::<usize>();
+ if size == 0b11 {
// `UNDEFINED`
return Err(DecodeError::Undefined);
}
+
+ /*
+ * trying to reorder tables a6-20, a6-19, and a6-18 to factor out operand
+ * sizes where possible...
+ *
+ * op1 | op2 | rn | rt | size| `see`
+ * 00 |000000|!=1111|!=1111| 00 |`LDRB (register) A8-423`
+ * 00 |000000|!=1111|==1111| 00 |`PLD, PLDW (register) A8-529`
+ * 00 |000000|!=1111|!=1111| 01 |`LDRH (register) A8-447`
+ * 00 |000000|!=1111|==1111| 01 |`PLD, PLDW (register) A8-529`
+ * 00 |000000|!=1111|------| 10 |`LDR (register, Thumb) A8-413`
+ *
+ * 00 |1100xx|!=1111|!=1111| 00 |`LDRB (immediate, Thumb) A8-417`
+ * 00 |1100xx|!=1111|==1111| 00 |`PLD, PLDW (immediate) A8-525`
+ * 00 |1100xx|!=1111|!=1111| 01 |`LDRH (immediate, Thumb) A8-441`
+ * 00 |1100xx|!=1111|==1111| 01 |`PLD, PLDW (immediate) A8-525`
+ * 00 |1100xx|!=1111|------| 10 |`LDR (immediate, Thumb) A8-407`
+ *
+ * 00 |1110xx|!=1111|------| 00 |`LDRBT A8-425`
+ * 00 |1110xx|!=1111|------| 01 |`LDRHT A8-449`
+ * 00 |1110xx|!=1111|------| 10 |`LDRT A8-467`
+ *
+ * 00 |1xx1xx|!=1111|------| 00 |`LDRB (immediate, Thumb) A8-417`
+ * 00 |1xx1xx|!=1111|------| 01 |`LDRH (immediate, Thumb) A8-441`
+ * 00 |1xx1xx|!=1111|------| 10 |`LDR (immediate, Thumb) A8-407`
+ *
+ * 01 |------|!=1111|!=1111| 00 |`LDRB (immediate, Thumb) A8-417`
+ * 01 |------|!=1111|==1111| 00 |`PLD, PLDW (immediate) A8-525`
+ * 01 |------|!=1111|!=1111| 01 |`LDRH (immediate, Thumb) A8-441`
+ * 01 |------|!=1111|==1111| 01 |`PLD, PLDW (immediate) A8-525`
+ * 01 |------|!=1111|------| 10 |`LDR (immediate, Thumb) A8-407`
+ *
+ * 0x |------|==1111|!=1111| 00 |`LDRB (literal) A8-421`
+ * 0x |------|==1111|==1111| 00 |`PLD (literal) A8-527`
+ * 0x |------|==1111|!=1111| 01 |`LDRH (literal) A8-445`
+ * 0x |------|==1111|==1111| 01 |`PLD (literal) A8-527`
+ * 0x |------|==1111|------| 10 |`LDR (literal) A8-411`
+ *
+ * 1x |------|------|------| 10 |`UNDEFINED (cite: A6.3.7)`
+ *
+ * 10 |000000|!=1111|!=1111| 00 |`LDRSB (register) A8-455`
+ * 10 |000000|!=1111|!=1111| 01 |`LDRSH (register) A8-463`
+ * 10 |000000|!=1111|==1111| 00 |`PLI (register) A8-553`
+ * 10 |000000|!=1111|==1111| 01 |`Unallocated memory hint (treat as NOP)`
+ *
+ * 10 |1100xx|!=1111|!=1111| 00 |`LDRSB (immediate) A8-451`
+ * 10 |1100xx|!=1111|==1111| 00 |`PLI (immediate, literal) A8-531`
+ * 10 |1100xx|!=1111|!=1111| 01 |`LDRSH (immediate) A8-459`
+ * 10 |1100xx|!=1111|==1111| 01 |`Unallocated memory hint (treat as NOP)`
+ *
+ * 10 |1110xx|!=1111|------| 00 |`LDRSBT A8-457`
+ * 10 |1110xx|!=1111|------| 01 |`LDRSHT A8-465`
+ *
+ * 10 |1xx1xx|!=1111|------| 00 |`LDRSB (immediate) A8-451`
+ * 10 |1xx1xx|!=1111|------| 01 |`LDRSH (immediate) A8-459`
+ *
+ * 11 |------|!=1111|!=1111| 00 |`LDRSB (immediate) A8-451`
+ * 11 |------|!=1111|==1111| 00 |`PLI (immediate, literal) A8-531`
+ * 11 |------|!=1111|!=1111| 01 |`LDRSH (immediate) A8-459`
+ * 11 |------|!=1111|==1111| 01 |`Unallocated memory hint (treat as NOP)`
+ * 1x |------|==1111|!=1111| 00 |`LDRSB (literal) A8-453`
+ * 1x |------|==1111|==1111| 00 |`PLI (immediate, literal) A8-531`
+ * 1x |------|==1111|!=1111| 01 |`LDRSH (literal) A8-461`
+ * 1x |------|==1111|==1111| 01 |`Unallocated memory hint (treat as NOP)`
+ */
+ if op1 == 0b00 {
+ // op1 == bits 7:8
+ /*
+ * op1 | op2 | rn | rt | size| `see`
+ * 0x |------|==1111|!=1111| 00 |`LDRB (literal) A8-421`
+ * 0x |------|==1111|==1111| 00 |`PLD (literal) A8-527`
+ * 0x |------|==1111|!=1111| 01 |`LDRH (literal) A8-445`
+ * 0x |------|==1111|==1111| 01 |`PLD (literal) A8-527`
+ * 0x |------|==1111|------| 10 |`LDR (literal) A8-411`
+ *
+ * 00 |000000|!=1111|!=1111| 00 |`LDRB (register) A8-423`
+ * 00 |000000|!=1111|==1111| 00 |`PLD, PLDW (register) A8-529`
+ * 00 |000000|!=1111|!=1111| 01 |`LDRH (register) A8-447`
+ * 00 |000000|!=1111|==1111| 01 |`PLD, PLDW (register) A8-529`
+ * 00 |000000|!=1111|------| 10 |`LDR (register, Thumb) A8-413`
+ *
+ * 00 |1100xx|!=1111|!=1111| 00 |`LDRB (immediate, Thumb) A8-417`
+ * 00 |1100xx|!=1111|==1111| 00 |`PLD, PLDW (immediate) A8-525`
+ * 00 |1100xx|!=1111|!=1111| 01 |`LDRH (immediate, Thumb) A8-441`
+ * 00 |1100xx|!=1111|==1111| 01 |`PLD, PLDW (immediate) A8-525`
+ * 00 |1100xx|!=1111|------| 10 |`LDR (immediate, Thumb) A8-407`
+ *
+ * 00 |1110xx|!=1111|------| 00 |`LDRBT A8-425`
+ * 00 |1110xx|!=1111|------| 01 |`LDRHT A8-449`
+ * 00 |1110xx|!=1111|------| 10 |`LDRT A8-467`
+ *
+ * 00 |1xx1xx|!=1111|------| 00 |`LDRB (immediate, Thumb) A8-417`
+ * 00 |1xx1xx|!=1111|------| 01 |`LDRH (immediate, Thumb) A8-441`
+ * 00 |1xx1xx|!=1111|------| 10 |`LDR (immediate, Thumb) A8-407`
+ */
+ if rn == 0b1111 {
+ // `(literal)`
+ let opcode = if rt == 0b1111 {
+ [
+ Opcode::PLD,
+ Opcode::PLD,
+ Opcode::LDR,
+ ][size]
+ } else {
+ [
+ Opcode::LDRB,
+ Opcode::LDRH,
+ Opcode::LDR,
+ ][size]
+ };
+ let u = false; // instr2[7], but known 0 here
+ let imm12 = lower2[..12].load::<u16>();
+ inst.opcode = opcode;
+ inst.operands = [
+ Operand::Reg(Reg::from_u8(rt)),
+ Operand::RegDerefPreindexOffset(Reg::from_u8(rn), imm12, false, false), // no add, no wback
+ Operand::Nothing,
+ Operand::Nothing,
+ ];
+ } else {
+ if op2 == 0b000000 {
+ // `(register, Thumb)`
+ let opcode = if rt == 0b1111 {
+ [
+ Opcode::PLD,
+ Opcode::PLD,
+ Opcode::LDR,
+ ][size]
+ } else {
+ [
+ Opcode::LDRB,
+ Opcode::LDRH,
+ Opcode::LDR,
+ ][size]
+ };
+ let rm = lower2[0..4].load::<u8>();
+ let imm2 = lower2[4..6].load::<u8>();
+ inst.opcode = opcode;
+ inst.operands = [
+ Operand::Reg(Reg::from_u8(rt)),
+ Operand::RegDerefPreindexRegShift(
+ Reg::from_u8(rn),
+ RegShift::from_raw(
+ 0b1000 | // `RegImm`
+ rm as u16 |
+ ((0 /* lsl */) << 5)|
+ ((imm2 as u16) << 7)
+ ),
+ true, // add
+ false, // wback
+ ),
+ Operand::Nothing,
+ Operand::Nothing,
+ ];
+ } else if op2 & 0b111100 == 0b110000 {
+ // `(immediate, Thumb)`
+ let opcode = if rt == 0b1111 {
+ [
+ Opcode::PLD,
+ Opcode::PLD,
+ Opcode::LDR,
+ ][size]
+ } else {
+ [
+ Opcode::LDRB,
+ Opcode::LDRH,
+ Opcode::LDR,
+ ][size]
+ };
+ let w = lower2[8];
+ let u = lower2[9];
+ let p = lower2[10];
+ let imm8 = lower2[..8].load::<u16>();
+ inst.opcode = opcode;
+ inst.operands = [
+ Operand::Reg(Reg::from_u8(rt)),
+ if p {
+ Operand::RegDerefPreindexOffset(Reg::from_u8(rn), imm8, u, w)
+ } else {
+ Operand::RegDerefPostindexOffset(Reg::from_u8(rn), imm8, u, false)
+ },
+ Operand::Nothing,
+ Operand::Nothing,
+ ];
+
+ } else if op2 & 0b111100 == 0b111000 {
+ // `(immediate, Thumb)`
+ let opcode = if rt == 0b1111 {
+ [
+ Opcode::PLD,
+ Opcode::PLD,
+ Opcode::LDRT,
+ ][size]
+ } else {
+ [
+ Opcode::LDRBT,
+ Opcode::LDRHT,
+ Opcode::LDRT,
+ ][size]
+ };
+ let w = lower2[8];
+ let u = lower2[9];
+ let p = lower2[10];
+ let imm8 = lower2[..8].load::<u16>();
+ inst.opcode = opcode;
+ inst.operands = [
+ Operand::Reg(Reg::from_u8(rt)),
+ if p {
+ Operand::RegDerefPreindexOffset(Reg::from_u8(rn), imm8, u, w)
+ } else {
+ Operand::RegDerefPostindexOffset(Reg::from_u8(rn), imm8, u, false)
+ },
+ Operand::Nothing,
+ Operand::Nothing,
+ ];
+ } else if op2 & 0b100100 == 0b100100 {
+ // `(immediate, Thumb)`
+ let opcode = if rt == 0b1111 {
+ [
+ Opcode::PLD,
+ Opcode::PLD,
+ Opcode::LDR,
+ ][size]
+ } else {
+ [
+ Opcode::LDRB,
+ Opcode::LDRH,
+ Opcode::LDR,
+ ][size]
+ };
+ let w = lower2[8];
+ let u = lower2[9];
+ let p = lower2[10];
+ let imm8 = lower2[..8].load::<u16>();
+ inst.opcode = opcode;
+ inst.operands = [
+ Operand::Reg(Reg::from_u8(rt)),
+ if p {
+ Operand::RegDerefPreindexOffset(Reg::from_u8(rn), imm8, u, w)
+ } else {
+ Operand::RegDerefPostindexOffset(Reg::from_u8(rn), imm8, u, false)
+ },
+ Operand::Nothing,
+ Operand::Nothing,
+ ];
+ } else {
+ // op2 =~ 0b1010xx or something?
+ // nothing to try decoding as for a `decoder.undefined()?`, so
+ // just error.
+ return Err(DecodeError::Undefined);
+ }
+ }
+ } else if op1 == 0b01 {
+ // op1 == bits 7:8
+ /*
+ * op1 | op2 | rn | rt | size| `see`
+ * 0x |------|==1111|!=1111| 00 |`LDRB (literal) A8-421`
+ * 0x |------|==1111|==1111| 00 |`PLD (literal) A8-527`
+ * 0x |------|==1111|!=1111| 01 |`LDRH (literal) A8-445`
+ * 0x |------|==1111|==1111| 01 |`PLD (literal) A8-527`
+ * 0x |------|==1111|------| 10 |`LDR (literal) A8-411`
+ *
+ * 01 |------|!=1111|!=1111| 00 |`LDRB (immediate, Thumb) A8-417`
+ * 01 |------|!=1111|==1111| 00 |`PLD, PLDW (immediate) A8-525`
+ * 01 |------|!=1111|!=1111| 01 |`LDRH (immediate, Thumb) A8-441`
+ * 01 |------|!=1111|==1111| 01 |`PLD, PLDW (immediate) A8-525`
+ * 01 |------|!=1111|------| 10 |`LDR (immediate, Thumb) A8-407`
+ */
+ if rn == 0b1111 {
+ let opcode = if rt == 0b1111 {
+ [
+ Opcode::PLD,
+ Opcode::PLD,
+ Opcode::LDR,
+ ][size]
+ } else {
+ [
+ Opcode::LDRB,
+ Opcode::LDRH,
+ Opcode::LDR,
+ ][size]
+ };
+ let u = true; // instr2[7], but known 1 here
+ let imm12 = lower2[..12].load::<u16>();
+ inst.opcode = opcode;
+ inst.operands = [
+ Operand::Reg(Reg::from_u8(rt)),
+ Operand::RegDerefPreindexOffset(Reg::from_u8(rn), imm12, true, false), // add, no wback
+ Operand::Nothing,
+ Operand::Nothing,
+ ];
+ } else {
+ let opcode = if rt == 0b1111 {
+ [
+ Opcode::PLD,
+ Opcode::PLD,
+ Opcode::LDR,
+ ][size]
+ } else {
+ [
+ Opcode::LDRB, // encoding T2
+ Opcode::LDRH, // encoding T2
+ Opcode::LDR, // encoding T3
+ ][size]
+ };
+ let imm12 = lower2[..12].load::<u16>();
+ inst.opcode = opcode;
+ inst.operands = [
+ Operand::Reg(Reg::from_u8(rt)),
+ Operand::RegDerefPreindexOffset(Reg::from_u8(rn), imm12, true, false), // add, no wback
+ Operand::Nothing,
+ Operand::Nothing,
+ ];
+ }
+ } else if op1 == 0b10 {
+ // op1 == bits 7:8
+ if size == 0b10 {
+ return Err(DecodeError::Undefined);
+ }
+ /*
+ * op1 | op2 | rn | rt | size| `see`
+ * 1x |------|------|------| 10 |`UNDEFINED (cite: A6.3.7)`
+ * 1x |------|==1111|!=1111| 00 |`LDRSB (literal) A8-453`
+ * 1x |------|==1111|==1111| 00 |`PLI (immediate, literal) A8-531`
+ * 1x |------|==1111|!=1111| 01 |`LDRSH (literal) A8-461`
+ * 1x |------|==1111|==1111| 01 |`Unallocated memory hint (treat as NOP)`
+ *
+ * 10 |000000|!=1111|!=1111| 00 |`LDRSB (register) A8-455`
+ * 10 |000000|!=1111|!=1111| 01 |`LDRSH (register) A8-463`
+ * 10 |000000|!=1111|==1111| 00 |`PLI (register) A8-553`
+ * 10 |000000|!=1111|==1111| 01 |`Unallocated memory hint (treat as NOP)`
+ *
+ * 10 |1100xx|!=1111|!=1111| 00 |`LDRSB (immediate) A8-451`
+ * 10 |1100xx|!=1111|==1111| 00 |`PLI (immediate, literal) A8-531`
+ * 10 |1100xx|!=1111|!=1111| 01 |`LDRSH (immediate) A8-459`
+ * 10 |1100xx|!=1111|==1111| 01 |`Unallocated memory hint (treat as NOP)`
+ *
+ * 10 |1110xx|!=1111|------| 00 |`LDRSBT A8-457`
+ * 10 |1110xx|!=1111|------| 01 |`LDRSHT A8-465`
+ *
+ * 10 |1xx1xx|!=1111|------| 00 |`LDRSB (immediate) A8-451`
+ * 10 |1xx1xx|!=1111|------| 01 |`LDRSH (immediate) A8-459`
+ */
+ if rn == 0b1111 {
+ // (literal)
+ let opcode = if rt == 0b1111 {
+ [
+ Opcode::PLI,
+ Opcode::NOP,
+ ][size]
+ } else {
+ [
+ Opcode::LDRSB,
+ Opcode::LDRSH,
+ ][size]
+ };
+ let u = false; // instr[7] known false here
+ let imm12 = lower2[..12].load::<u16>();
+ inst.opcode = opcode;
+ inst.operands = [
+ Operand::Reg(Reg::from_u8(rt)),
+ Operand::RegDerefPreindexOffset(Reg::from_u8(15), imm12, false, false), // add, no wback
+ Operand::Nothing,
+ Operand::Nothing,
+ ];
+ } else {
+ if op2 == 0b000000 {
+ let opcode = if rt == 0b1111 {
+ [
+ Opcode::PLI,
+ Opcode::NOP,
+ ][size]
+ } else {
+ [
+ Opcode::LDRSB, // encoding T2
+ Opcode::LDRSH, // encoding T2
+ ][size]
+ };
+ let rm = lower2[0..4].load::<u8>();
+ let imm2 = lower2[4..6].load::<u8>();
+ inst.opcode = opcode;
+ inst.operands = [
+ Operand::Reg(Reg::from_u8(rt)),
+ Operand::RegDerefPreindexRegShift(
+ Reg::from_u8(rn),
+ RegShift::from_raw(
+ 0b1000 | // `RegImm`
+ rm as u16 |
+ ((0 /* lsl */) << 5)|
+ ((imm2 as u16) << 7)
+ ),
+ true, // add
+ false, // wback
+ ),
+ Operand::Nothing,
+ Operand::Nothing,
+ ];
+ } else if op2 & 0b111100 == 0b110000 {
+ let opcode = if rt == 0b1111 {
+ [
+ Opcode::PLI,
+ Opcode::NOP,
+ ][size]
+ } else {
+ [
+ Opcode::LDRSB, // encoding T2
+ Opcode::LDRSH, // encoding T2
+ ][size]
+ };
+ let w = lower2[8];
+ let u = lower2[9];
+ let p = lower2[10];
+ let imm8 = lower2[..8].load::<u16>();
+ inst.opcode = opcode;
+ inst.operands = [
+ Operand::Reg(Reg::from_u8(rt)),
+ if p {
+ Operand::RegDerefPreindexOffset(Reg::from_u8(rn), imm8, u, w)
+ } else {
+ Operand::RegDerefPostindexOffset(Reg::from_u8(rn), imm8, u, false)
+ },
+ Operand::Nothing,
+ Operand::Nothing,
+ ];
+ } else if op2 & 0b111100 == 0b111000 {
+ let opcode = [
+ Opcode::LDRSBT, // encoding T1
+ Opcode::LDRSHT, // encoding T1
+ ][size];
+ let imm8 = lower2[..8].load::<u16>();
+ inst.opcode = opcode;
+ inst.operands = [
+ Operand::Reg(Reg::from_u8(rt)),
+ Operand::RegDerefPreindexOffset(Reg::from_u8(rn), imm8, true, false), // add, no wback
+ Operand::Nothing,
+ Operand::Nothing,
+ ];
+ } else if op2 & 0b100100 == 0b100100 {
+ let opcode = [
+ Opcode::LDRSB, // encoding T2
+ Opcode::LDRSH, // encoding T2
+ ][size];
+ let w = lower2[8];
+ let u = lower2[9];
+ let p = lower2[10];
+ let imm8 = lower2[..8].load::<u16>();
+ inst.opcode = opcode;
+ inst.operands = [
+ Operand::Reg(Reg::from_u8(rt)),
+ if p {
+ Operand::RegDerefPreindexOffset(Reg::from_u8(rn), imm8, u, w)
+ } else {
+ Operand::RegDerefPostindexOffset(Reg::from_u8(rn), imm8, u, false)
+ },
+ Operand::Nothing,
+ Operand::Nothing,
+ ];
+ } else {
+ // op2 =~ 0b1010xx or something?
+ // nothing to try decoding as for a `decoder.undefined()?`, so
+ // just error.
+ return Err(DecodeError::Undefined);
+ }
+ }
+ } else {
+ // op1 == bits 7:8
+ if size == 0b10 {
+ return Err(DecodeError::Undefined);
+ }
+ // op1 == 0b11
+ /*
+ * 1x |------|------|------| 10 |`UNDEFINED (cite: A6.3.7)`
+ * 1x |------|==1111|!=1111| 00 |`LDRSB (literal) A8-453`
+ * 1x |------|==1111|==1111| 00 |`PLI (immediate, literal) A8-531`
+ * 1x |------|==1111|!=1111| 01 |`LDRSH (literal) A8-461`
+ * 1x |------|==1111|==1111| 01 |`Unallocated memory hint (treat as NOP)`
+ *
+ * 11 |------|!=1111|!=1111| 00 |`LDRSB (immediate) A8-451`
+ * 11 |------|!=1111|==1111| 00 |`PLI (immediate, literal) A8-531`
+ * 11 |------|!=1111|!=1111| 01 |`LDRSH (immediate) A8-459`
+ * 11 |------|!=1111|==1111| 01 |`Unallocated memory hint (treat as NOP)`
+ */
+ if rn == 0b1111 {
+ // (literal)
+ let opcode = if rt == 0b1111 {
+ [
+ Opcode::PLI,
+ Opcode::NOP,
+ ][size]
+ } else {
+ [
+ Opcode::LDRSB,
+ Opcode::LDRSH,
+ ][size]
+ };
+ let u = true; // instr[7] known true here
+ let imm12 = lower2[..12].load::<u16>();
+ inst.opcode = opcode;
+ inst.operands = [
+ Operand::Reg(Reg::from_u8(rt)),
+ Operand::RegDerefPreindexOffset(Reg::from_u8(15), imm12, u, false), // add, no wback
+ Operand::Nothing,
+ Operand::Nothing,
+ ];
+ } else {
+ // (immediate)
+ let opcode = if rt == 0b1111 {
+ [
+ Opcode::PLI,
+ Opcode::NOP,
+ ][size]
+ } else {
+ [
+ Opcode::LDRSB, // encoding T1
+ Opcode::LDRSH, // encoding T1
+ ][size]
+ };
+ let imm12 = lower2[..12].load::<u16>();
+ inst.opcode = opcode;
+ inst.operands = [
+ Operand::Reg(Reg::from_u8(rt)),
+ Operand::RegDerefPreindexOffset(Reg::from_u8(rn), imm12, true, false), // add, no wback
+ Operand::Nothing,
+ Operand::Nothing,
+ ];
+ }
+ }
}
} else {
if !op2[4] {
generated by cgit v1.1 at 2024-11-01 04:38:12 +0000