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GeezerVison is showing github.com — Implement LOAD_ATTR inline caching with adaptive specialization by youknowone · Pull Request #7292 · RustPython/RustPython

Implement LOAD_ATTR inline caching with adaptive specialization #7292

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Merged
youknowone merged 6 commits into RustPython:main from youknowone:load-attr
Mar 2, 2026

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Merged

Implement LOAD_ATTR inline caching with adaptive specialization #7292

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023bbd4
Implement LOAD_ATTR inline caching with adaptive specialization
youknowone Mar 1, 2026
ff073c8
Add BINARY_OP and CALL adaptive specialization
youknowone Mar 1, 2026
0fa6fa7
Lazy quickening for adaptive specialization counters
youknowone Mar 1, 2026
5f23161
Add Instruction::deoptimize() and CodeUnits::original_bytes()
youknowone Mar 1, 2026
a831e4f
Fix monitoring and specialization interaction
youknowone Mar 1, 2026
79ca9c1
Address review: bounds checks, UB fix, version overflow, error handling
youknowone Mar 2, 2026
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1 change: 1 addition & 0 deletions 1 .cspell.dict/cpython.txt
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Original file line number Diff line number Diff line change
Expand Up @@ -44,6 +44,7 @@ copyslot
cpucount
defaultdict
denom
deopt
dictbytype
DICTFLAG
dictoffset
Expand Down
2 changes: 2 additions & 0 deletions 2 .cspell.json
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Original file line number Diff line number Diff line change
Expand Up @@ -60,6 +60,7 @@
"dedentations",
"dedents",
"deduped",
"deoptimize",
"downcastable",
"downcasted",
"dumpable",
Expand All @@ -73,6 +74,7 @@
"interps",
"jitted",
"jitting",
"kwonly",
"lossily",
"makeunicodedata",
"microbenchmark",
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12 changes: 7 additions & 5 deletions 12 crates/codegen/src/ir.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -457,11 +457,13 @@ impl CodeInfo {
.map(|byte| CodeUnit::new(Instruction::ExtendedArg, byte))
.chain([CodeUnit { op, arg: lo_arg }]),
);
// Emit CACHE code units after the instruction
instructions.extend(core::iter::repeat_n(
CodeUnit::new(Instruction::Cache, 0.into()),
cache_count,
));
// Emit CACHE code units after the instruction (all zeroed)
if cache_count > 0 {
instructions.extend(core::iter::repeat_n(
CodeUnit::new(Instruction::Cache, 0.into()),
cache_count,
));
}
current_offset = offset_after;
}
next_block = block.next;
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145 changes: 144 additions & 1 deletion 145 crates/compiler-core/src/bytecode.rs
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Expand Up @@ -343,6 +343,11 @@ pub struct CodeUnit {

const _: () = assert!(mem::size_of::<CodeUnit>() == 2);

/// Adaptive specialization: number of executions before attempting specialization.
pub const ADAPTIVE_WARMUP_VALUE: u8 = 50;
/// Adaptive specialization: backoff counter after de-optimization.
pub const ADAPTIVE_BACKOFF_VALUE: u8 = 250;

impl CodeUnit {
pub const fn new(op: Instruction, arg: OpArgByte) -> Self {
Self { op, arg }
Expand Down Expand Up @@ -391,7 +396,11 @@ impl TryFrom<&[u8]> for CodeUnits {
return Err(Self::Error::InvalidBytecode);
}

value.chunks_exact(2).map(CodeUnit::try_from).collect()
let units: Self = value
.chunks_exact(2)
.map(CodeUnit::try_from)
.collect::<Result<_, _>>()?;
Ok(units)
}
}

Expand Down Expand Up @@ -441,6 +450,140 @@ impl CodeUnits {
core::ptr::write(op_ptr, new_op.into());
}
}

/// Write a u16 value into a CACHE code unit at `index`.
/// Each CodeUnit is 2 bytes (#[repr(C)]: op u8 + arg u8), so one u16 fits exactly.
///
/// # Safety
/// - `index` must be in bounds and point to a CACHE entry.
/// - The caller must ensure no concurrent reads/writes to the same slot.
pub unsafe fn write_cache_u16(&self, index: usize, value: u16) {
unsafe {
let units = &mut *self.0.get();
let ptr = units.as_mut_ptr().add(index) as *mut u8;
core::ptr::write_unaligned(ptr as *mut u16, value);
}
}

/// Read a u16 value from a CACHE code unit at `index`.
///
/// # Panics
/// Panics if `index` is out of bounds.
pub fn read_cache_u16(&self, index: usize) -> u16 {
let units = unsafe { &*self.0.get() };
assert!(index < units.len(), "read_cache_u16: index out of bounds");
let ptr = units.as_ptr().wrapping_add(index) as *const u8;
unsafe { core::ptr::read_unaligned(ptr as *const u16) }
}

/// Write a u32 value across two consecutive CACHE code units starting at `index`.
///
/// # Safety
/// Same requirements as `write_cache_u16`.
pub unsafe fn write_cache_u32(&self, index: usize, value: u32) {
unsafe {
self.write_cache_u16(index, value as u16);
self.write_cache_u16(index + 1, (value >> 16) as u16);
}
}

/// Read a u32 value from two consecutive CACHE code units starting at `index`.
///
/// # Panics
/// Panics if `index + 1` is out of bounds.
pub fn read_cache_u32(&self, index: usize) -> u32 {
let lo = self.read_cache_u16(index) as u32;
let hi = self.read_cache_u16(index + 1) as u32;
lo | (hi << 16)
}
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/// Write a u64 value across four consecutive CACHE code units starting at `index`.
///
/// # Safety
/// Same requirements as `write_cache_u16`.
pub unsafe fn write_cache_u64(&self, index: usize, value: u64) {
unsafe {
self.write_cache_u32(index, value as u32);
self.write_cache_u32(index + 2, (value >> 32) as u32);
}
}

/// Read a u64 value from four consecutive CACHE code units starting at `index`.
///
/// # Panics
/// Panics if `index + 3` is out of bounds.
pub fn read_cache_u64(&self, index: usize) -> u64 {
let lo = self.read_cache_u32(index) as u64;
let hi = self.read_cache_u32(index + 2) as u64;
lo | (hi << 32)
}

/// Read the adaptive counter from the first CACHE entry's `arg` byte.
/// This preserves `op = Instruction::Cache`, unlike `read_cache_u16`.
pub fn read_adaptive_counter(&self, index: usize) -> u8 {
let units = unsafe { &*self.0.get() };
u8::from(units[index].arg)
}

/// Write the adaptive counter to the first CACHE entry's `arg` byte.
/// This preserves `op = Instruction::Cache`, unlike `write_cache_u16`.
///
/// # Safety
/// - `index` must be in bounds and point to a CACHE entry.
pub unsafe fn write_adaptive_counter(&self, index: usize, value: u8) {
let units = unsafe { &mut *self.0.get() };
units[index].arg = OpArgByte::from(value);
}

/// Produce a clean copy of the bytecode suitable for serialization
/// (marshal) and `co_code`. Specialized opcodes are mapped back to their
/// base variants via `deoptimize()` and all CACHE entries are zeroed.
pub fn original_bytes(&self) -> Vec<u8> {
let units = unsafe { &*self.0.get() };
let mut out = Vec::with_capacity(units.len() * 2);
let len = units.len();
let mut i = 0;
while i < len {
let op = units[i].op.deoptimize();
let caches = op.cache_entries();
out.push(u8::from(op));
out.push(u8::from(units[i].arg));
// Zero-fill all CACHE entries (counter + cached data)
for _ in 0..caches {
i += 1;
out.push(0); // op = Cache = 0
out.push(0); // arg = 0
}
i += 1;
}
out
}

/// Initialize adaptive warmup counters for all cacheable instructions.
/// Called lazily at RESUME (first execution of a code object).
/// Uses the `arg` byte of the first CACHE entry, preserving `op = Instruction::Cache`.
pub fn quicken(&self) {
let units = unsafe { &mut *self.0.get() };
let len = units.len();
let mut i = 0;
while i < len {
let op = units[i].op;
let caches = op.cache_entries();
if caches > 0 {
// Don't write adaptive counter for instrumented opcodes;
// specialization is skipped while monitoring is active.
if !op.is_instrumented() {
let cache_base = i + 1;
if cache_base < len {
units[cache_base].arg = OpArgByte::from(ADAPTIVE_WARMUP_VALUE);
}
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}
i += 1 + caches;
} else {
i += 1;
}
}
}
}

/// A Constant (which usually encapsulates data within it)
Expand Down
127 changes: 125 additions & 2 deletions 127 crates/compiler-core/src/bytecode/instruction.rs
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Expand Up @@ -512,6 +512,126 @@ impl Instruction {
})
}

/// Map a specialized opcode back to its adaptive (base) variant.
/// `_PyOpcode_Deopt`
pub fn deoptimize(self) -> Self {
match self {
// LOAD_ATTR specializations
Self::LoadAttrClass
| Self::LoadAttrClassWithMetaclassCheck
| Self::LoadAttrGetattributeOverridden
| Self::LoadAttrInstanceValue
| Self::LoadAttrMethodLazyDict
| Self::LoadAttrMethodNoDict
| Self::LoadAttrMethodWithValues
| Self::LoadAttrModule
| Self::LoadAttrNondescriptorNoDict
| Self::LoadAttrNondescriptorWithValues
| Self::LoadAttrProperty
| Self::LoadAttrSlot
| Self::LoadAttrWithHint => Self::LoadAttr { idx: Arg::marker() },
// BINARY_OP specializations
Self::BinaryOpAddFloat
| Self::BinaryOpAddInt
| Self::BinaryOpAddUnicode
| Self::BinaryOpExtend
| Self::BinaryOpInplaceAddUnicode
| Self::BinaryOpMultiplyFloat
| Self::BinaryOpMultiplyInt
| Self::BinaryOpSubscrDict
| Self::BinaryOpSubscrGetitem
| Self::BinaryOpSubscrListInt
| Self::BinaryOpSubscrListSlice
| Self::BinaryOpSubscrStrInt
| Self::BinaryOpSubscrTupleInt
| Self::BinaryOpSubtractFloat
| Self::BinaryOpSubtractInt => Self::BinaryOp { op: Arg::marker() },
// CALL specializations
Self::CallAllocAndEnterInit
| Self::CallBoundMethodExactArgs
| Self::CallBoundMethodGeneral
| Self::CallBuiltinClass
| Self::CallBuiltinFast
| Self::CallBuiltinFastWithKeywords
| Self::CallBuiltinO
| Self::CallIsinstance
| Self::CallLen
| Self::CallListAppend
| Self::CallMethodDescriptorFast
| Self::CallMethodDescriptorFastWithKeywords
| Self::CallMethodDescriptorNoargs
| Self::CallMethodDescriptorO
| Self::CallNonPyGeneral
| Self::CallPyExactArgs
| Self::CallPyGeneral
| Self::CallStr1
| Self::CallTuple1
| Self::CallType1 => Self::Call {
nargs: Arg::marker(),
},
// CALL_KW specializations
Self::CallKwBoundMethod | Self::CallKwNonPy | Self::CallKwPy => Self::CallKw {
nargs: Arg::marker(),
},
// TO_BOOL specializations
Self::ToBoolAlwaysTrue
| Self::ToBoolBool
| Self::ToBoolInt
| Self::ToBoolList
| Self::ToBoolNone
| Self::ToBoolStr => Self::ToBool,
// COMPARE_OP specializations
Self::CompareOpFloat | Self::CompareOpInt | Self::CompareOpStr => {
Self::CompareOp { op: Arg::marker() }
}
// CONTAINS_OP specializations
Self::ContainsOpDict | Self::ContainsOpSet => Self::ContainsOp(Arg::marker()),
// FOR_ITER specializations
Self::ForIterGen | Self::ForIterList | Self::ForIterRange | Self::ForIterTuple => {
Self::ForIter {
target: Arg::marker(),
}
}
// LOAD_GLOBAL specializations
Self::LoadGlobalBuiltin | Self::LoadGlobalModule => Self::LoadGlobal(Arg::marker()),
// STORE_ATTR specializations
Self::StoreAttrInstanceValue | Self::StoreAttrSlot | Self::StoreAttrWithHint => {
Self::StoreAttr { idx: Arg::marker() }
}
// LOAD_SUPER_ATTR specializations
Self::LoadSuperAttrAttr | Self::LoadSuperAttrMethod => {
Self::LoadSuperAttr { arg: Arg::marker() }
}
// STORE_SUBSCR specializations
Self::StoreSubscrDict | Self::StoreSubscrListInt => Self::StoreSubscr,
// UNPACK_SEQUENCE specializations
Self::UnpackSequenceList | Self::UnpackSequenceTuple | Self::UnpackSequenceTwoTuple => {
Self::UnpackSequence {
size: Arg::marker(),
}
}
// SEND specializations
Self::SendGen => Self::Send {
target: Arg::marker(),
},
// LOAD_CONST specializations
Self::LoadConstImmortal | Self::LoadConstMortal => {
Self::LoadConst { idx: Arg::marker() }
}
// RESUME specializations
Self::ResumeCheck => Self::Resume { arg: Arg::marker() },
// JUMP_BACKWARD specializations
Self::JumpBackwardJit | Self::JumpBackwardNoJit => Self::JumpBackward {
target: Arg::marker(),
},
// Instrumented opcodes map back to their base
_ => match self.to_base() {
Some(base) => base,
None => self,
},
}
}
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/// Number of CACHE code units that follow this instruction.
/// _PyOpcode_Caches
pub fn cache_entries(self) -> usize {
Expand Down Expand Up @@ -626,8 +746,11 @@ impl Instruction {
| Self::UnpackSequenceTuple
| Self::UnpackSequenceTwoTuple => 1,

// Everything else: 0 cache entries
_ => 0,
// Instrumented opcodes have the same cache entries as their base
_ => match self.to_base() {
Some(base) => base.cache_entries(),
None => 0,
},
}
}
}
Expand Down
5 changes: 2 additions & 3 deletions 5 crates/compiler-core/src/marshal.rs
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Expand Up @@ -662,9 +662,8 @@ pub fn serialize_value<W: Write, D: Dumpable>(

pub fn serialize_code<W: Write, C: Constant>(buf: &mut W, code: &CodeObject<C>) {
write_len(buf, code.instructions.len());
// SAFETY: it's ok to transmute CodeUnit to [u8; 2]
let (_, instructions_bytes, _) = unsafe { code.instructions.align_to() };
buf.write_slice(instructions_bytes);
let original = code.instructions.original_bytes();
buf.write_slice(&original);

write_len(buf, code.locations.len());
for (start, end) in &*code.locations {
Expand Down
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