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Remove unnecessary matches for loads/stores
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Simplify the load/store code by removing the unnecessary matches on the access size. I have not done it for float loads/stores because that requires a separate change to make the float code generic over size.
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@Timmmm
Timmmm committed May 15, 2024
1 parent 95be70b commit c062d7b
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Showing 3 changed files with 90 additions and 204 deletions.
127 changes: 36 additions & 91 deletions model/riscv_insts_aext.sail
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Original file line number Diff line number Diff line change
Expand Up @@ -53,47 +53,32 @@ mapping clause encdec = LOADRES(aq, rl, rs1, size, rd) if amo_width_valid(size)
* call to load_reservation in LR and cancel_reservation in SC.
*/

val process_loadres : forall 'n, 0 < 'n <= xlen_bytes. (regidx, xlenbits, MemoryOpResult(bits(8 * 'n)), bool) -> Retired
function process_loadres(rd, addr, value, is_unsigned) =
match extend_value(is_unsigned, value) {
MemValue(result) => { load_reservation(addr); X(rd) = result; RETIRE_SUCCESS },
MemException(e) => { handle_mem_exception(addr, e); RETIRE_FAIL }
}

function clause execute(LOADRES(aq, rl, rs1, width, rd)) = {
let width_bytes = size_bytes(width);

// This is checked during decoding.
assert(width_bytes <= sizeof(xlen_bytes));

if haveAtomics() then {
/* Get the address, X(rs1) (no offset).
* Extensions might perform additional checks on address validity.
*/
match ext_data_get_addr(rs1, zeros(), Read(Data), size_bytes(width)) {
Ext_DataAddr_Error(e) => { ext_handle_data_check_error(e); RETIRE_FAIL },
Ext_DataAddr_OK(vaddr) => {
let aligned : bool =
/* BYTE and HALF would only occur due to invalid decodes, but it doesn't hurt
* to treat them as valid here; otherwise we'd need to throw an internal_error.
*/
match width {
BYTE => true,
HALF => vaddr[0..0] == 0b0,
WORD => vaddr[1..0] == 0b00,
DOUBLE => vaddr[2..0] == 0b000
};
/* "LR faults like a normal load, even though it's in the AMO major opcode space."
* - Andrew Waterman, isa-dev, 10 Jul 2018.
*/
if not(aligned)
if not(is_aligned(vaddr, width))
then { handle_mem_exception(vaddr, E_Load_Addr_Align()); RETIRE_FAIL }
else match translateAddr(vaddr, Read(Data)) {
TR_Failure(e, _) => { handle_mem_exception(vaddr, e); RETIRE_FAIL },
TR_Address(addr, _) =>
match (width, sizeof(xlen)) {
(BYTE, _) => process_loadres(rd, vaddr, mem_read(Read(Data), addr, 1, aq, aq & rl, true), false),
(HALF, _) => process_loadres(rd, vaddr, mem_read(Read(Data), addr, 2, aq, aq & rl, true), false),
(WORD, _) => process_loadres(rd, vaddr, mem_read(Read(Data), addr, 4, aq, aq & rl, true), false),
(DOUBLE, 64) => process_loadres(rd, vaddr, mem_read(Read(Data), addr, 8, aq, aq & rl, true), false),
_ => internal_error(__FILE__, __LINE__, "Unexpected AMO width")
}
}
TR_Failure(e, _) => { handle_mem_exception(vaddr, e); RETIRE_FAIL },
TR_Address(addr, _) =>
match mem_read(Read(Data), addr, 1, aq, aq & rl, true) {
MemValue(result) => { load_reservation(addr); X(rd) = zero_extend(result); RETIRE_SUCCESS },
MemException(e) => { handle_mem_exception(addr, e); RETIRE_FAIL }
},
}
}
}
} else {
Expand All @@ -113,6 +98,11 @@ mapping clause encdec = STORECON(aq, rl, rs2, rs1, size, rd) if amo_width_valid(

/* NOTE: Currently, we only EA if address translation is successful. This may need revisiting. */
function clause execute (STORECON(aq, rl, rs2, rs1, width, rd)) = {
let width_bytes = size_bytes(width);

// This is checked during decoding.
assert(width_bytes <= sizeof(xlen_bytes));

if speculate_conditional () == false then {
/* should only happen in rmem
* rmem: allow SC to fail very early
Expand All @@ -129,17 +119,7 @@ function clause execute (STORECON(aq, rl, rs2, rs1, width, rd)) = {
match ext_data_get_addr(rs1, zeros(), Write(Data), size_bytes(width)) {
Ext_DataAddr_Error(e) => { ext_handle_data_check_error(e); RETIRE_FAIL },
Ext_DataAddr_OK(vaddr) => {
let aligned : bool =
/* BYTE and HALF would only occur due to invalid decodes, but it doesn't hurt
* to treat them as valid here; otherwise we'd need to throw an internal_error.
*/
match width {
BYTE => true,
HALF => vaddr[0..0] == 0b0,
WORD => vaddr[1..0] == 0b00,
DOUBLE => vaddr[2..0] == 0b000
};
if not(aligned)
if not(is_aligned(vaddr, width))
then { handle_mem_exception(vaddr, E_SAMO_Addr_Align()); RETIRE_FAIL }
else {
if match_reservation(vaddr) == false then {
Expand All @@ -150,25 +130,12 @@ function clause execute (STORECON(aq, rl, rs2, rs1, width, rd)) = {
* both result in a SAMO exception */
TR_Failure(e, _) => { handle_mem_exception(vaddr, e); RETIRE_FAIL },
TR_Address(addr, _) => {
let eares : MemoryOpResult(unit) = match (width, sizeof(xlen)) {
(BYTE, _) => mem_write_ea(addr, 1, aq & rl, rl, true),
(HALF, _) => mem_write_ea(addr, 2, aq & rl, rl, true),
(WORD, _) => mem_write_ea(addr, 4, aq & rl, rl, true),
(DOUBLE, 64) => mem_write_ea(addr, 8, aq & rl, rl, true),
_ => internal_error(__FILE__, __LINE__, "STORECON expected word or double")
};
let eares = mem_write_ea(addr, width_bytes, aq & rl, rl, true);
match (eares) {
MemException(e) => { handle_mem_exception(vaddr, e); RETIRE_FAIL },
MemValue(_) => {
rs2_val = X(rs2);
let res : MemoryOpResult(bool) = match (width, sizeof(xlen)) {
(BYTE, _) => mem_write_value(addr, 1, rs2_val[7..0], aq & rl, rl, true),
(HALF, _) => mem_write_value(addr, 2, rs2_val[15..0], aq & rl, rl, true),
(WORD, _) => mem_write_value(addr, 4, rs2_val[31..0], aq & rl, rl, true),
(DOUBLE, 64) => mem_write_value(addr, 8, rs2_val, aq & rl, rl, true),
_ => internal_error(__FILE__, __LINE__, "STORECON expected word or double")
};
match (res) {
let rs2_val = X(rs2);
match mem_write_value(addr, width_bytes, rs2_val[width_bytes * 8 - 1 .. 0], aq & rl, rl, true) {
MemValue(true) => { X(rd) = zero_extend(0b0); cancel_reservation(); RETIRE_SUCCESS },
MemValue(false) => { X(rd) = zero_extend(0b1); cancel_reservation(); RETIRE_SUCCESS },
MemException(e) => { handle_mem_exception(vaddr, e); RETIRE_FAIL }
Expand Down Expand Up @@ -212,47 +179,36 @@ mapping clause encdec = AMO(op, aq, rl, rs2, rs1, size, rd) if amo_width_valid(s
/* NOTE: Currently, we only EA if address translation is successful.
This may need revisiting. */
function clause execute (AMO(op, aq, rl, rs2, rs1, width, rd)) = {
let width_bytes = size_bytes(width);

// This is checked during decoding.
assert(width_bytes <= sizeof(xlen_bytes));

if haveAtomics() then {
/* Get the address, X(rs1) (no offset).
* Some extensions perform additional checks on address validity.
*/
match ext_data_get_addr(rs1, zeros(), ReadWrite(Data, Data), size_bytes(width)) {
match ext_data_get_addr(rs1, zeros(), ReadWrite(Data, Data), width_bytes) {
Ext_DataAddr_Error(e) => { ext_handle_data_check_error(e); RETIRE_FAIL },
Ext_DataAddr_OK(vaddr) => {
match translateAddr(vaddr, ReadWrite(Data, Data)) {
TR_Failure(e, _) => { handle_mem_exception(vaddr, e); RETIRE_FAIL },
TR_Address(addr, _) => {
let eares : MemoryOpResult(unit) = match (width, sizeof(xlen)) {
(BYTE, _) => mem_write_ea(addr, 1, aq & rl, rl, true),
(HALF, _) => mem_write_ea(addr, 2, aq & rl, rl, true),
(WORD, _) => mem_write_ea(addr, 4, aq & rl, rl, true),
(DOUBLE, 64) => mem_write_ea(addr, 8, aq & rl, rl, true),
_ => internal_error(__FILE__, __LINE__, "Unexpected AMO width")
};
let eares = mem_write_ea(addr, width_bytes, aq & rl, rl, true);
let is_unsigned : bool = match op {
AMOMINU => true,
AMOMAXU => true,
_ => false
};
let rs2_val : xlenbits = match width {
BYTE => if is_unsigned then zero_extend(X(rs2)[7..0]) else sign_extend(X(rs2)[7..0]),
HALF => if is_unsigned then zero_extend(X(rs2)[15..0]) else sign_extend(X(rs2)[15..0]),
WORD => if is_unsigned then zero_extend(X(rs2)[31..0]) else sign_extend(X(rs2)[31..0]),
DOUBLE => X(rs2)
};
let rs2_val = X(rs2)[width_bytes * 8 - 1 .. 0];
let rs2_val = extend_value(is_unsigned, rs2_val);
match (eares) {
MemException(e) => { handle_mem_exception(vaddr, e); RETIRE_FAIL },
MemValue(_) => {
let mval : MemoryOpResult(xlenbits) = match (width, sizeof(xlen)) {
(BYTE, _) => extend_value(is_unsigned, mem_read(ReadWrite(Data, Data), addr, 1, aq, aq & rl, true)),
(HALF, _) => extend_value(is_unsigned, mem_read(ReadWrite(Data, Data), addr, 2, aq, aq & rl, true)),
(WORD, _) => extend_value(is_unsigned, mem_read(ReadWrite(Data, Data), addr, 4, aq, aq & rl, true)),
(DOUBLE, 64) => extend_value(is_unsigned, mem_read(ReadWrite(Data, Data), addr, 8, aq, aq & rl, true)),
_ => internal_error(__FILE__, __LINE__, "Unexpected AMO width")
};
match (mval) {
match mem_read(ReadWrite(Data, Data), addr, width_bytes, aq, aq & rl, true) {
MemException(e) => { handle_mem_exception(vaddr, e); RETIRE_FAIL },
MemValue(loaded) => {
let loaded = extend_value(is_unsigned, loaded);
let result : xlenbits =
match op {
AMOSWAP => rs2_val,
Expand All @@ -269,20 +225,9 @@ function clause execute (AMO(op, aq, rl, rs2, rs1, width, rd)) = {
AMOMINU => to_bits(sizeof(xlen), min(unsigned(rs2_val), unsigned(loaded))),
AMOMAXU => to_bits(sizeof(xlen), max(unsigned(rs2_val), unsigned(loaded)))
};
let rval : xlenbits = match width {
BYTE => sign_extend(loaded[7..0]),
HALF => sign_extend(loaded[15..0]),
WORD => sign_extend(loaded[31..0]),
DOUBLE => loaded
};
let wval : MemoryOpResult(bool) = match (width, sizeof(xlen)) {
(BYTE, _) => mem_write_value(addr, 1, result[7..0], aq & rl, rl, true),
(HALF, _) => mem_write_value(addr, 2, result[15..0], aq & rl, rl, true),
(WORD, _) => mem_write_value(addr, 4, result[31..0], aq & rl, rl, true),
(DOUBLE, 64) => mem_write_value(addr, 8, result, aq & rl, rl, true),
_ => internal_error(__FILE__, __LINE__, "Unexpected AMO width")
};
match (wval) {
let rval : xlenbits = sign_extend(loaded[width_bytes * 8 - 1 .. 0]);
let wval = mem_write_value(addr, width_bytes, result[width_bytes * 8 - 1 .. 0], aq & rl, rl, true);
match wval {
MemValue(true) => { X(rd) = rval; RETIRE_SUCCESS },
MemValue(false) => { internal_error(__FILE__, __LINE__, "AMO got false from mem_write_value") },
MemException(e) => { handle_mem_exception(vaddr, e); RETIRE_FAIL }
Expand Down
79 changes: 32 additions & 47 deletions model/riscv_insts_base.sail
View file
Original file line number Diff line number Diff line change
Expand Up @@ -300,52 +300,45 @@ union clause ast = LOAD : (bits(12), regidx, regidx, bool, word_width, bool, boo
mapping clause encdec = LOAD(imm, rs1, rd, is_unsigned, size, false, false) if (size_bytes(size) < sizeof(xlen_bytes)) | (not(is_unsigned) & size_bytes(size) <= sizeof(xlen_bytes))
<-> imm @ rs1 @ bool_bits(is_unsigned) @ size_enc(size) @ rd @ 0b0000011 if (size_bytes(size) < sizeof(xlen_bytes)) | (not(is_unsigned) & size_bytes(size) <= sizeof(xlen_bytes))

val extend_value : forall 'n, 0 < 'n <= xlen_bytes. (bool, MemoryOpResult(bits(8 * 'n))) -> MemoryOpResult(xlenbits)
function extend_value(is_unsigned, value) = match (value) {
MemValue(v) => MemValue(if is_unsigned then zero_extend(v) else sign_extend(v) : xlenbits),
MemException(e) => MemException(e)
}

val process_load : forall 'n, 0 < 'n <= xlen_bytes. (regidx, xlenbits, MemoryOpResult(bits(8 * 'n)), bool) -> Retired
function process_load(rd, vaddr, value, is_unsigned) =
match extend_value(is_unsigned, value) {
MemValue(result) => { X(rd) = result; RETIRE_SUCCESS },
MemException(e) => { handle_mem_exception(vaddr, e); RETIRE_FAIL }
val extend_value : forall 'n, 0 < 'n <= xlen. (bool, bits('n)) -> xlenbits
function extend_value(is_unsigned, value) = if is_unsigned then zero_extend(value) else sign_extend(value)

function is_aligned(vaddr : xlenbits, width : word_width) -> bool =
match width {
BYTE => true,
HALF => vaddr[0..0] == 0b0,
WORD => vaddr[1..0] == 0b00,
DOUBLE => vaddr[2..0] == 0b000
}

// Return true if the address is misaligned and we don't support misaligned access.
function check_misaligned(vaddr : xlenbits, width : word_width) -> bool =
if plat_enable_misaligned_access() then false
else match width {
BYTE => false,
HALF => vaddr[0] == bitone,
WORD => vaddr[0] == bitone | vaddr[1] == bitone,
DOUBLE => vaddr[0] == bitone | vaddr[1] == bitone | vaddr[2] == bitone
}
not(plat_enable_misaligned_access()) & not(is_aligned(vaddr, width))

function clause execute(LOAD(imm, rs1, rd, is_unsigned, width, aq, rl)) = {
let offset : xlenbits = sign_extend(imm);
let width_bytes = size_bytes(width);

// This is checked during decoding.
assert(width_bytes <= sizeof(xlen_bytes));

/* Get the address, X(rs1) + offset.
Some extensions perform additional checks on address validity. */
match ext_data_get_addr(rs1, offset, Read(Data), size_bytes(width)) {
match ext_data_get_addr(rs1, offset, Read(Data), width_bytes) {
Ext_DataAddr_Error(e) => { ext_handle_data_check_error(e); RETIRE_FAIL },
Ext_DataAddr_OK(vaddr) =>
Ext_DataAddr_OK(vaddr) => {
if check_misaligned(vaddr, width)
then { handle_mem_exception(vaddr, E_Load_Addr_Align()); RETIRE_FAIL }
else match translateAddr(vaddr, Read(Data)) {
TR_Failure(e, _) => { handle_mem_exception(vaddr, e); RETIRE_FAIL },
TR_Address(paddr, _) =>
match (width) {
BYTE =>
process_load(rd, vaddr, mem_read(Read(Data), paddr, 1, aq, rl, false), is_unsigned),
HALF =>
process_load(rd, vaddr, mem_read(Read(Data), paddr, 2, aq, rl, false), is_unsigned),
WORD =>
process_load(rd, vaddr, mem_read(Read(Data), paddr, 4, aq, rl, false), is_unsigned),
DOUBLE if sizeof(xlen) >= 64 =>
process_load(rd, vaddr, mem_read(Read(Data), paddr, 8, aq, rl, false), is_unsigned),
_ => report_invalid_width(__FILE__, __LINE__, width, "load")
}

match mem_read(Read(Data), paddr, width_bytes, aq, rl, false) {
MemValue(result) => { X(rd) = extend_value(is_unsigned, result); RETIRE_SUCCESS },
MemException(e) => { handle_mem_exception(vaddr, e); RETIRE_FAIL },
},
}
},
}
}

Expand Down Expand Up @@ -380,35 +373,27 @@ mapping clause encdec = STORE(imm7 @ imm5, rs2, rs1, size, false, false)
This may need revisiting. */
function clause execute (STORE(imm, rs2, rs1, width, aq, rl)) = {
let offset : xlenbits = sign_extend(imm);
let width_bytes = size_bytes(width);

// This is checked during decoding.
assert(width_bytes <= sizeof(xlen_bytes));

/* Get the address, X(rs1) + offset.
Some extensions perform additional checks on address validity. */
match ext_data_get_addr(rs1, offset, Write(Data), size_bytes(width)) {
match ext_data_get_addr(rs1, offset, Write(Data), width_bytes) {
Ext_DataAddr_Error(e) => { ext_handle_data_check_error(e); RETIRE_FAIL },
Ext_DataAddr_OK(vaddr) =>
if check_misaligned(vaddr, width)
then { handle_mem_exception(vaddr, E_SAMO_Addr_Align()); RETIRE_FAIL }
else match translateAddr(vaddr, Write(Data)) {
TR_Failure(e, _) => { handle_mem_exception(vaddr, e); RETIRE_FAIL },
TR_Address(paddr, _) => {
let eares : MemoryOpResult(unit) = match width {
BYTE => mem_write_ea(paddr, 1, aq, rl, false),
HALF => mem_write_ea(paddr, 2, aq, rl, false),
WORD => mem_write_ea(paddr, 4, aq, rl, false),
DOUBLE => mem_write_ea(paddr, 8, aq, rl, false)
};
let eares = mem_write_ea(paddr, width_bytes, aq, rl, false);
match (eares) {
MemException(e) => { handle_mem_exception(vaddr, e); RETIRE_FAIL },
MemValue(_) => {
let rs2_val = X(rs2);
let res : MemoryOpResult(bool) = match (width) {
BYTE => mem_write_value(paddr, 1, rs2_val[7..0], aq, rl, false),
HALF => mem_write_value(paddr, 2, rs2_val[15..0], aq, rl, false),
WORD => mem_write_value(paddr, 4, rs2_val[31..0], aq, rl, false),
DOUBLE if sizeof(xlen) >= 64
=> mem_write_value(paddr, 8, rs2_val, aq, rl, false),
_ => report_invalid_width(__FILE__, __LINE__, width, "store"),
};
match (res) {
match mem_write_value(paddr, width_bytes, rs2_val[width_bytes * 8 - 1 .. 0], aq, rl, false) {
MemValue(true) => RETIRE_SUCCESS,
MemValue(false) => internal_error(__FILE__, __LINE__, "store got false from mem_write_value"),
MemException(e) => { handle_mem_exception(vaddr, e); RETIRE_FAIL }
Expand Down
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