diff options
Diffstat (limited to 'tvix/eval/src/vm')
| -rw-r--r-- | tvix/eval/src/vm/mod.rs | 307 |
1 files changed, 189 insertions, 118 deletions
diff --git a/tvix/eval/src/vm/mod.rs b/tvix/eval/src/vm/mod.rs index a6d0941e8d7a..7ac6d493fa1f 100644 --- a/tvix/eval/src/vm/mod.rs +++ b/tvix/eval/src/vm/mod.rs @@ -28,7 +28,7 @@ use crate::{ lifted_pop, nix_search_path::NixSearchPath, observer::RuntimeObserver, - opcode::{CodeIdx, Count, JumpOffset, OpCode, StackIdx, UpvalueIdx}, + opcode::{CodeIdx, Op, Position, UpvalueIdx}, upvalues::Upvalues, value::{ Builtin, BuiltinResult, Closure, CoercionKind, Lambda, NixAttrs, NixContext, NixList, @@ -146,10 +146,32 @@ impl CallFrame { /// Increment this frame's instruction pointer and return the operation that /// the pointer moved past. - fn inc_ip(&mut self) -> OpCode { - let op = self.chunk()[self.ip]; + fn inc_ip(&mut self) -> Op { + debug_assert!( + self.ip.0 < self.chunk().code.len(), + "out of bounds code at IP {} in {:p}", + self.ip.0, + self.lambda + ); + + let op = self.chunk().code[self.ip.0]; self.ip += 1; - op + op.into() + } + + /// Read a varint-encoded operand and return it. The frame pointer is + /// incremented internally. + fn read_uvarint(&mut self) -> u64 { + let (arg, size) = self.chunk().read_uvarint(self.ip.0); + self.ip += size; + arg + } + + /// Read a fixed-size u16 and increment the frame pointer. + fn read_u16(&mut self) -> u16 { + let arg = self.chunk().read_u16(self.ip.0); + self.ip += 2; + arg } /// Construct an error result from the given ErrorKind and the source span @@ -443,17 +465,25 @@ where self.observer.observe_execute_op(frame.ip, &op, &self.stack); match op { - OpCode::OpThunkSuspended(idx) | OpCode::OpThunkClosure(idx) => { - let blueprint = match &frame.chunk()[idx] { + Op::ThunkSuspended | Op::ThunkClosure => { + let idx = frame.read_uvarint() as usize; + + let blueprint = match &frame.chunk().constants[idx] { Value::Blueprint(lambda) => lambda.clone(), _ => panic!("compiler bug: non-blueprint in blueprint slot"), }; - let upvalue_count = blueprint.upvalue_count; - let thunk = if matches!(op, OpCode::OpThunkClosure(_)) { + let upvalue_count = frame.read_uvarint(); + + debug_assert!( + (upvalue_count >> 1) == blueprint.upvalue_count as u64, + "TODO: new upvalue count not correct", + ); + + let thunk = if op == Op::ThunkClosure { debug_assert!( - upvalue_count > 0, - "OpThunkClosure should not be called for plain lambdas" + (((upvalue_count >> 1) > 0) || (upvalue_count & 0b1 == 1)), + "OpThunkClosure should not be called for plain lambdas", ); Thunk::new_closure(blueprint) } else { @@ -470,7 +500,7 @@ where self.populate_upvalues(&mut frame, upvalue_count, upvalues)?; } - OpCode::OpForce => { + Op::Force => { if let Some(Value::Thunk(_)) = self.stack.last() { let thunk = match self.stack_pop() { Value::Thunk(t) => t, @@ -488,25 +518,35 @@ where } } - OpCode::OpGetUpvalue(upv_idx) => { - let value = frame.upvalue(upv_idx).clone(); + Op::GetUpvalue => { + let idx = UpvalueIdx(frame.read_uvarint() as usize); + let value = frame.upvalue(idx).clone(); self.stack.push(value); } // Discard the current frame. - OpCode::OpReturn => { + Op::Return => { // TODO(amjoseph): I think this should assert `==` rather // than `<=` but it fails with the stricter condition. debug_assert!(self.stack.len() - 1 <= frame.stack_offset); return Ok(true); } - OpCode::OpConstant(idx) => { - let c = frame.chunk()[idx].clone(); + Op::Constant => { + let idx = frame.read_uvarint() as usize; + + debug_assert!( + idx < frame.chunk().constants.len(), + "out of bounds constant at IP {} in {:p}", + frame.ip.0, + frame.lambda + ); + + let c = frame.chunk().constants[idx].clone(); self.stack.push(c); } - OpCode::OpCall => { + Op::Call => { let callable = self.stack_pop(); self.call_value(frame.current_span(), Some((span, frame)), callable)?; @@ -516,7 +556,8 @@ where // Remove the given number of elements from the stack, // but retain the top value. - OpCode::OpCloseScope(Count(count)) => { + Op::CloseScope => { + let count = frame.read_uvarint() as usize; // Immediately move the top value into the right // position. let target_idx = self.stack.len() - 1 - count; @@ -528,15 +569,22 @@ where } } - OpCode::OpClosure(idx) => { - let blueprint = match &frame.chunk()[idx] { + Op::Closure => { + let idx = frame.read_uvarint() as usize; + let blueprint = match &frame.chunk().constants[idx] { Value::Blueprint(lambda) => lambda.clone(), _ => panic!("compiler bug: non-blueprint in blueprint slot"), }; - let upvalue_count = blueprint.upvalue_count; + let upvalue_count = frame.read_uvarint(); + + debug_assert!( + (upvalue_count >> 1) == blueprint.upvalue_count as u64, + "TODO: new upvalue count not correct in closure", + ); + debug_assert!( - upvalue_count > 0, + ((upvalue_count >> 1) > 0 || (upvalue_count & 0b1 == 1)), "OpClosure should not be called for plain lambdas" ); @@ -549,7 +597,7 @@ where )))); } - OpCode::OpAttrsSelect => lifted_pop! { + Op::AttrsSelect => lifted_pop! { self(key, attrs) => { let key = key.to_str().with_span(&frame, self)?; let attrs = attrs.to_attrs().with_span(&frame, self)?; @@ -569,21 +617,24 @@ where } }, - OpCode::OpJumpIfFalse(JumpOffset(offset)) => { + Op::JumpIfFalse => { + let offset = frame.read_u16() as usize; debug_assert!(offset != 0); if !self.stack_peek(0).as_bool().with_span(&frame, self)? { frame.ip += offset; } } - OpCode::OpJumpIfCatchable(JumpOffset(offset)) => { + Op::JumpIfCatchable => { + let offset = frame.read_u16() as usize; debug_assert!(offset != 0); if self.stack_peek(0).is_catchable() { frame.ip += offset; } } - OpCode::OpJumpIfNoFinaliseRequest(JumpOffset(offset)) => { + Op::JumpIfNoFinaliseRequest => { + let offset = frame.read_u16() as usize; debug_assert!(offset != 0); match self.stack_peek(0) { Value::FinaliseRequest(finalise) => { @@ -595,11 +646,11 @@ where } } - OpCode::OpPop => { + Op::Pop => { self.stack.pop(); } - OpCode::OpAttrsTrySelect => { + Op::AttrsTrySelect => { let key = self.stack_pop().to_str().with_span(&frame, self)?; let value = match self.stack_pop() { Value::Attrs(attrs) => match attrs.select(&key) { @@ -613,12 +664,14 @@ where self.stack.push(value); } - OpCode::OpGetLocal(StackIdx(local_idx)) => { + Op::GetLocal => { + let local_idx = frame.read_uvarint() as usize; let idx = frame.stack_offset + local_idx; self.stack.push(self.stack[idx].clone()); } - OpCode::OpJumpIfNotFound(JumpOffset(offset)) => { + Op::JumpIfNotFound => { + let offset = frame.read_u16() as usize; debug_assert!(offset != 0); if matches!(self.stack_peek(0), Value::AttrNotFound) { self.stack_pop(); @@ -626,12 +679,13 @@ where } } - OpCode::OpJump(JumpOffset(offset)) => { + Op::Jump => { + let offset = frame.read_u16() as usize; debug_assert!(offset != 0); frame.ip += offset; } - OpCode::OpEqual => lifted_pop! { + Op::Equal => lifted_pop! { self(b, a) => { let gen_span = frame.current_span(); self.push_call_frame(span, frame); @@ -646,7 +700,7 @@ where // top is not of the expected type. This is necessary // to implement some specific behaviours of Nix // exactly. - OpCode::OpAssertBool => { + Op::AssertBool => { let val = self.stack_peek(0); // TODO(edef): propagate this into is_bool, since bottom values *are* values of any type if !val.is_catchable() && !val.is_bool() { @@ -660,7 +714,7 @@ where } } - OpCode::OpAssertAttrs => { + Op::AssertAttrs => { let val = self.stack_peek(0); // TODO(edef): propagate this into is_attrs, since bottom values *are* values of any type if !val.is_catchable() && !val.is_attrs() { @@ -674,9 +728,9 @@ where } } - OpCode::OpAttrs(Count(count)) => self.run_attrset(&frame, count)?, + Op::Attrs => self.run_attrset(frame.read_uvarint() as usize, &frame)?, - OpCode::OpAttrsUpdate => lifted_pop! { + Op::AttrsUpdate => lifted_pop! { self(rhs, lhs) => { let rhs = rhs.to_attrs().with_span(&frame, self)?; let lhs = lhs.to_attrs().with_span(&frame, self)?; @@ -684,28 +738,30 @@ where } }, - OpCode::OpInvert => lifted_pop! { + Op::Invert => lifted_pop! { self(v) => { let v = v.as_bool().with_span(&frame, self)?; self.stack.push(Value::Bool(!v)); } }, - OpCode::OpList(Count(count)) => { + Op::List => { + let count = frame.read_uvarint() as usize; let list = NixList::construct(count, self.stack.split_off(self.stack.len() - count)); self.stack.push(Value::List(list)); } - OpCode::OpJumpIfTrue(JumpOffset(offset)) => { + Op::JumpIfTrue => { + let offset = frame.read_u16() as usize; debug_assert!(offset != 0); if self.stack_peek(0).as_bool().with_span(&frame, self)? { frame.ip += offset; } } - OpCode::OpHasAttr => lifted_pop! { + Op::HasAttr => lifted_pop! { self(key, attrs) => { let key = key.to_str().with_span(&frame, self)?; let result = match attrs { @@ -720,7 +776,7 @@ where } }, - OpCode::OpConcat => lifted_pop! { + Op::Concat => lifted_pop! { self(rhs, lhs) => { let rhs = rhs.to_list().with_span(&frame, self)?.into_inner(); let lhs = lhs.to_list().with_span(&frame, self)?.into_inner(); @@ -728,7 +784,7 @@ where } }, - OpCode::OpResolveWith => { + Op::ResolveWith => { let ident = self.stack_pop().to_str().with_span(&frame, self)?; // Re-enqueue this frame. @@ -755,13 +811,19 @@ where return Ok(false); } - OpCode::OpFinalise(StackIdx(idx)) => match &self.stack[frame.stack_offset + idx] { - Value::Closure(_) => panic!("attempted to finalise a closure"), - Value::Thunk(thunk) => thunk.finalise(&self.stack[frame.stack_offset..]), - _ => panic!("attempted to finalise a non-thunk"), - }, + Op::Finalise => { + let idx = frame.read_uvarint() as usize; + match &self.stack[frame.stack_offset + idx] { + Value::Closure(_) => panic!("attempted to finalise a closure"), + Value::Thunk(thunk) => thunk.finalise(&self.stack[frame.stack_offset..]), + _ => panic!("attempted to finalise a non-thunk"), + } + } + + Op::CoerceToString => { + let kind: CoercionKind = frame.chunk().code[frame.ip.0].into(); + frame.ip.0 += 1; - OpCode::OpCoerceToString(kind) => { let value = self.stack_pop(); let gen_span = frame.current_span(); self.push_call_frame(span, frame); @@ -773,9 +835,9 @@ where return Ok(false); } - OpCode::OpInterpolate(Count(count)) => self.run_interpolate(&frame, count)?, + Op::Interpolate => self.run_interpolate(frame.read_uvarint(), &frame)?, - OpCode::OpValidateClosedFormals => { + Op::ValidateClosedFormals => { let formals = frame.lambda.formals.as_ref().expect( "OpValidateClosedFormals called within the frame of a lambda without formals", ); @@ -799,7 +861,7 @@ where } } - OpCode::OpAdd => lifted_pop! { + Op::Add => lifted_pop! { self(b, a) => { let gen_span = frame.current_span(); self.push_call_frame(span, frame); @@ -812,21 +874,21 @@ where } }, - OpCode::OpSub => lifted_pop! { + Op::Sub => lifted_pop! { self(b, a) => { let result = arithmetic_op!(&a, &b, -).with_span(&frame, self)?; self.stack.push(result); } }, - OpCode::OpMul => lifted_pop! { + Op::Mul => lifted_pop! { self(b, a) => { let result = arithmetic_op!(&a, &b, *).with_span(&frame, self)?; self.stack.push(result); } }, - OpCode::OpDiv => lifted_pop! { + Op::Div => lifted_pop! { self(b, a) => { match b { Value::Integer(0) => return frame.error(self, ErrorKind::DivisionByZero), @@ -841,7 +903,7 @@ where } }, - OpCode::OpNegate => match self.stack_pop() { + Op::Negate => match self.stack_pop() { Value::Integer(i) => self.stack.push(Value::Integer(-i)), Value::Float(f) => self.stack.push(Value::Float(-f)), Value::Catchable(cex) => self.stack.push(Value::Catchable(cex)), @@ -856,12 +918,12 @@ where } }, - OpCode::OpLess => cmp_op!(self, frame, span, <), - OpCode::OpLessOrEq => cmp_op!(self, frame, span, <=), - OpCode::OpMore => cmp_op!(self, frame, span, >), - OpCode::OpMoreOrEq => cmp_op!(self, frame, span, >=), + Op::Less => cmp_op!(self, frame, span, <), + Op::LessOrEq => cmp_op!(self, frame, span, <=), + Op::More => cmp_op!(self, frame, span, >), + Op::MoreOrEq => cmp_op!(self, frame, span, >=), - OpCode::OpFindFile => match self.stack_pop() { + Op::FindFile => match self.stack_pop() { Value::UnresolvedPath(path) => { let resolved = self .nix_search_path @@ -873,7 +935,7 @@ where _ => panic!("tvix compiler bug: OpFindFile called on non-UnresolvedPath"), }, - OpCode::OpResolveHomePath => match self.stack_pop() { + Op::ResolveHomePath => match self.stack_pop() { Value::UnresolvedPath(path) => { match dirs::home_dir() { None => { @@ -896,24 +958,23 @@ where } }, - OpCode::OpPushWith(StackIdx(idx)) => self.with_stack.push(frame.stack_offset + idx), + Op::PushWith => self + .with_stack + .push(frame.stack_offset + frame.read_uvarint() as usize), - OpCode::OpPopWith => { + Op::PopWith => { self.with_stack.pop(); } - OpCode::OpAssertFail => { + Op::AssertFail => { self.stack .push(Value::from(CatchableErrorKind::AssertionFailed)); } - // Data-carrying operands should never be executed, - // that is a critical error in the VM/compiler. - OpCode::DataStackIdx(_) - | OpCode::DataDeferredLocal(_) - | OpCode::DataUpvalueIdx(_) - | OpCode::DataCaptureWith => { - panic!("Tvix bug: attempted to execute data-carrying operand") + // Encountering an invalid opcode is a critical error in the + // VM/compiler. + Op::Invalid => { + panic!("Tvix bug: attempted to execute invalid opcode") } } } @@ -933,7 +994,7 @@ where &self.stack[self.stack.len() - 1 - offset] } - fn run_attrset(&mut self, frame: &CallFrame, count: usize) -> EvalResult<()> { + fn run_attrset(&mut self, count: usize, frame: &CallFrame) -> EvalResult<()> { let attrs = NixAttrs::construct(count, self.stack.split_off(self.stack.len() - count * 2)) .with_span(frame, self)? .map(Value::attrs) @@ -971,7 +1032,7 @@ where /// Interpolate string fragments by popping the specified number of /// fragments of the stack, evaluating them to strings, and pushing /// the concatenated result string back on the stack. - fn run_interpolate(&mut self, frame: &CallFrame, count: usize) -> EvalResult<()> { + fn run_interpolate(&mut self, count: u64, frame: &CallFrame) -> EvalResult<()> { let mut out = BString::default(); // Interpolation propagates the context and union them. let mut context: NixContext = NixContext::new(); @@ -1090,64 +1151,74 @@ where } /// Populate the upvalue fields of a thunk or closure under construction. + /// + /// See the closely tied function `emit_upvalue_data` in the compiler + /// implementation for details on the argument processing. fn populate_upvalues( &mut self, frame: &mut CallFrame, - count: usize, + count: u64, mut upvalues: impl DerefMut<Target = Upvalues>, ) -> EvalResult<()> { - for _ in 0..count { - match frame.inc_ip() { - OpCode::DataStackIdx(StackIdx(stack_idx)) => { - let idx = frame.stack_offset + stack_idx; - - let val = match self.stack.get(idx) { - Some(val) => val.clone(), - None => { - return frame.error( - self, - ErrorKind::TvixBug { - msg: "upvalue to be captured was missing on stack", - metadata: Some(Rc::new(json!({ - "ip": format!("{:#x}", frame.ip.0 - 1), - "stack_idx(relative)": stack_idx, - "stack_idx(absolute)": idx, - }))), - }, - ); - } - }; + // Determine whether to capture the with stack, and then shift the + // actual count of upvalues back. + let capture_with = count & 0b1 == 1; + let count = count >> 1; + if capture_with { + // Start the captured with_stack off of the + // current call frame's captured with_stack, ... + let mut captured_with_stack = frame + .upvalues + .with_stack() + .cloned() + // ... or make an empty one if there isn't one already. + .unwrap_or_else(|| Vec::with_capacity(self.with_stack.len())); + + for idx in &self.with_stack { + captured_with_stack.push(self.stack[*idx].clone()); + } - upvalues.deref_mut().push(val); - } + upvalues.deref_mut().set_with_stack(captured_with_stack); + } - OpCode::DataUpvalueIdx(upv_idx) => { - upvalues.deref_mut().push(frame.upvalue(upv_idx).clone()); - } + for _ in 0..count { + let pos = Position(frame.read_uvarint()); - OpCode::DataDeferredLocal(idx) => { - upvalues.deref_mut().push(Value::DeferredUpvalue(idx)); - } + if let Some(stack_idx) = pos.runtime_stack_index() { + let idx = frame.stack_offset + stack_idx.0; - OpCode::DataCaptureWith => { - // Start the captured with_stack off of the - // current call frame's captured with_stack, ... - let mut captured_with_stack = frame - .upvalues - .with_stack() - .cloned() - // ... or make an empty one if there isn't one already. - .unwrap_or_else(|| Vec::with_capacity(self.with_stack.len())); - - for idx in &self.with_stack { - captured_with_stack.push(self.stack[*idx].clone()); + let val = match self.stack.get(idx) { + Some(val) => val.clone(), + None => { + return frame.error( + self, + ErrorKind::TvixBug { + msg: "upvalue to be captured was missing on stack", + metadata: Some(Rc::new(json!({ + "ip": format!("{:#x}", frame.ip.0 - 1), + "stack_idx(relative)": stack_idx.0, + "stack_idx(absolute)": idx, + }))), + }, + ); } + }; - upvalues.deref_mut().set_with_stack(captured_with_stack); - } + upvalues.deref_mut().push(val); + continue; + } - _ => panic!("compiler error: missing closure operand"), + if let Some(idx) = pos.runtime_deferred_local() { + upvalues.deref_mut().push(Value::DeferredUpvalue(idx)); + continue; } + + if let Some(idx) = pos.runtime_upvalue_index() { + upvalues.deref_mut().push(frame.upvalue(idx).clone()); + continue; + } + + panic!("Tvix bug: invalid capture position emitted") } Ok(()) |