1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
|
//! This module implements the instruction set running on the abstract
//! machine implemented by tvix.
use std::ops::{AddAssign, Sub};
/// Index of a constant in the current code chunk.
#[repr(transparent)]
#[derive(Clone, Copy, Debug, PartialEq, Eq)]
pub struct ConstantIdx(pub usize);
/// Index of an instruction in the current code chunk.
#[repr(transparent)]
#[derive(Clone, Copy, Debug)]
pub struct CodeIdx(pub usize);
impl AddAssign<usize> for CodeIdx {
fn add_assign(&mut self, rhs: usize) {
*self = CodeIdx(self.0 + rhs)
}
}
impl Sub<usize> for CodeIdx {
type Output = Self;
fn sub(self, rhs: usize) -> Self::Output {
CodeIdx(self.0 - rhs)
}
}
/// Index of a value in the runtime stack. This is an offset
/// *relative to* the VM value stack_base of the CallFrame
/// containing the opcode which contains this StackIdx.
#[repr(transparent)]
#[derive(Clone, Copy, Debug, PartialEq, Eq, PartialOrd)]
pub struct StackIdx(pub usize);
/// Index of an upvalue within a closure's bound-variable upvalue
/// list. This is an absolute index into the Upvalues of the
/// CallFrame containing the opcode which contains this UpvalueIdx.
#[repr(transparent)]
#[derive(Clone, Copy, Debug, PartialEq, Eq)]
pub struct UpvalueIdx(pub usize);
/// Offset by which an instruction pointer should change in a jump.
#[repr(transparent)]
#[derive(Clone, Copy, Debug, PartialEq, Eq)]
pub struct JumpOffset(pub usize);
/// Provided count for an instruction (could represent e.g. a number
/// of elements).
#[repr(transparent)]
#[derive(Clone, Copy, Debug, PartialEq, Eq)]
pub struct Count(pub usize);
/// All variants of this enum carry a bounded amount of data to
/// ensure that no heap allocations are needed for an Opcode.
#[warn(variant_size_differences)]
#[derive(Clone, Copy, Debug, PartialEq, Eq)]
pub enum OpCode {
/// Push a constant onto the stack.
OpConstant(ConstantIdx),
/// Discard a value from the stack.
OpPop,
// Unary operators
OpInvert,
OpNegate,
// Arithmetic binary operators
OpAdd,
OpSub,
OpMul,
OpDiv,
// Comparison operators
OpEqual,
OpLess,
OpLessOrEq,
OpMore,
OpMoreOrEq,
// Logical operators & generic jumps
OpJump(JumpOffset),
OpJumpIfTrue(JumpOffset),
OpJumpIfFalse(JumpOffset),
OpJumpIfNotFound(JumpOffset),
OpJumpIfNoFinaliseRequest(JumpOffset),
// Attribute sets
/// Construct an attribute set from the given number of key-value pairs on the top of the stack
///
/// Note that this takes the count of *pairs*, not the number of *stack values* - the actual
/// number of values popped off the stack will be twice the argument to this op
OpAttrs(Count),
OpAttrsUpdate,
OpAttrsSelect,
OpAttrsTrySelect,
OpHasAttr,
/// Throw an error if the attribute set at the top of the stack has any attributes
/// other than those listed in the formals of the current lambda
///
/// Panics if the current frame is not a lambda with formals
OpValidateClosedFormals,
// `with`-handling
OpPushWith(StackIdx),
OpPopWith,
OpResolveWith,
// Lists
OpList(Count),
OpConcat,
// Strings
OpInterpolate(Count),
/// Force the Value on the stack and coerce it to a string, always using
/// `CoercionKind::Weak`.
OpCoerceToString,
// Paths
/// Attempt to resolve the Value on the stack using the configured [`NixSearchPath`][]
///
/// [`NixSearchPath`]: crate::nix_search_path::NixSearchPath
OpFindFile,
/// Attempt to resolve a path literal relative to the home dir
OpResolveHomePath,
// Type assertion operators
OpAssertBool,
OpAssertAttrs,
/// Access local identifiers with statically known positions.
OpGetLocal(StackIdx),
/// Close scopes while leaving their expression value around.
OpCloseScope(Count), // number of locals to pop
/// Return an error indicating that an `assert` failed
OpAssertFail,
// Lambdas & closures
OpCall,
OpGetUpvalue(UpvalueIdx),
/// A Closure which has upvalues but no self-references
OpClosure(ConstantIdx),
/// A Closure which has self-references (direct or via upvalues)
OpThunkClosure(ConstantIdx),
/// A suspended thunk, used to ensure laziness
OpThunkSuspended(ConstantIdx),
OpForce,
/// Finalise initialisation of the upvalues of the value in the given stack
/// index (which must be a Value::Thunk) after the scope is fully bound.
OpFinalise(StackIdx),
/// Final instruction emitted in a chunk. Does not have an
/// inherent effect, but can simplify VM logic as a marker in some
/// cases.
///
/// Can be thought of as "returning" the value to the parent
/// frame, hence the name.
OpReturn,
// [`OpClosure`], [`OpThunkSuspended`], and [`OpThunkClosure`] have a
// variable number of arguments to the instruction, which is
// represented here by making their data part of the opcodes.
// Each of these two opcodes has a `ConstantIdx`, which must
// reference a `Value::Blueprint(Lambda)`. The `upvalue_count`
// field in that `Lambda` indicates the number of arguments it
// takes, and the opcode must be followed by exactly this number
// of `Data*` opcodes. The VM skips over these by advancing the
// instruction pointer.
//
// It is illegal for a `Data*` opcode to appear anywhere else.
/// Populate a static upvalue by copying from the stack immediately.
DataStackIdx(StackIdx),
/// Populate a static upvalue of a thunk by copying it the stack, but do
/// when the thunk is finalised (by OpFinalise) rather than immediately.
DataDeferredLocal(StackIdx),
/// Populate a static upvalue by copying it from the upvalues of an
/// enclosing scope.
DataUpvalueIdx(UpvalueIdx),
/// Populate dynamic upvalues by saving a copy of the with-stack.
DataCaptureWith,
}
|
