313 lines
11 KiB
Nim
313 lines
11 KiB
Nim
# Copyright 2022 Mattia Giambirtone & All Contributors
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#
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# Licensed under the Apache License, Version 2.0 (the "License");
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# you may not use this file except in compliance with the License.
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# You may obtain a copy of the License at
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#
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# http://www.apache.org/licenses/LICENSE-2.0
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#
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# Unless required by applicable law or agreed to in writing, software
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# distributed under the License is distributed on an "AS IS" BASIS,
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# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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# See the License for the specific language governing permissions and
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# limitations under the License.
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## The Peon runtime environment
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import types
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import strformat
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import ../config
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import ../frontend/meta/bytecode
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import ../util/multibyte
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type
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PeonVM* = ref object
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## The Peon Virtual Machine
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stack: seq[PeonObject]
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ip: int # Instruction pointer
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cache: array[6, PeonObject] # Singletons cache
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chunk: Chunk # Piece of bytecode to execute
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frames: seq[int] # Stores the initial index of stack frames
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heapVars: seq[PeonObject] # Stores variables that do not have stack semantics (i.e. "static")
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proc initCache*(self: PeonVM) =
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## Initializes the VM's
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## singletons cache
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self.cache[0] = PeonObject(kind: Nil)
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self.cache[1] = PeonObject(kind: Bool, boolean: true)
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self.cache[2] = PeonObject(kind: Bool, boolean: false)
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self.cache[3] = PeonObject(kind: ObjectKind.Inf, positive: true)
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self.cache[4] = PeonObject(kind: ObjectKind.Inf, positive: false)
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self.cache[5] = PeonObject(kind: ObjectKind.Nan)
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proc newPeonVM*: PeonVM =
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## Initializes a new, blank VM
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## for executing Peon bytecode
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new(result)
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result.ip = 0
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result.frames = @[]
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result.stack = newSeq[PeonObject]()
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result.initCache()
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## Getters for singleton types (they are cached!)
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proc getNil*(self: PeonVM): PeonObject = self.cache[0]
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proc getBool*(self: PeonVM, value: bool): PeonObject =
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if value:
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return self.cache[1]
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return self.cache[2]
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proc getInf*(self: PeonVM, positive: bool): PeonObject =
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if positive:
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return self.cache[3]
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return self.cache[4]
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proc getNan*(self: PeonVM): PeonObject = self.cache[5]
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## Stack primitives. Note: all stack accessing that goes
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## through the get/set wrappers is frame-relative, meaning
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## that the index is added to the current stack frame's
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## bottom to obtain an absolute stack index.
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proc push(self: PeonVM, obj: PeonObject) =
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## Pushes a Peon object onto the
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## stack
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self.stack.add(obj)
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proc pop(self: PeonVM): PeonObject =
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## Pops a Peon object off the
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## stack, decreasing the stack
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## pointer. The object is returned
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return self.stack.pop()
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proc peek(self: PeonVM): PeonObject =
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## Returns the Peon object at the top
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## of the stack without consuming
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## it
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return self.stack[^1]
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proc get(self: PeonVM, idx: int): PeonObject =
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## Accessor method that abstracts
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## stack accessing through stack
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## frames
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return self.stack[idx + self.frames[^1]]
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proc set(self: PeonVM, idx: int, val: PeonObject) =
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## Setter method that abstracts
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## stack accessing through stack
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## frames
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self.stack[idx + self.frames[^1]] = val
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proc readByte(self: PeonVM): uint8 =
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## Reads a single byte from the
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## bytecode and returns it as an
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## unsigned 8 bit integer
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inc(self.ip)
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return self.chunk.code[self.ip - 1]
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proc readShort(self: PeonVM): uint16 =
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## Reads two bytes from the
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## bytecode and returns them
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## as an unsigned 16 bit
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## integer
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return [self.readByte(), self.readByte()].fromDouble()
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proc readLong(self: PeonVM): uint32 =
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## Reads three bytes from the
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## bytecode and returns them
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## as an unsigned 32 bit
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## integer. Note however that
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## the boundary is capped at
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## 24 bits instead of 32
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return uint32([self.readByte(), self.readByte(), self.readByte()].fromTriple())
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proc readInt64(self: PeonVM, idx: int): PeonObject =
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## Reads a constant from the
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## chunk's constant table and
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## returns a Peon object. Assumes
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## the constant is an Int64
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var arr = [self.chunk.consts[idx], self.chunk.consts[idx + 1],
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self.chunk.consts[idx + 2], self.chunk.consts[idx + 3],
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self.chunk.consts[idx + 4], self.chunk.consts[idx + 5],
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self.chunk.consts[idx + 6], self.chunk.consts[idx + 7],
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]
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result = PeonObject(kind: Int64)
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copyMem(result.long.addr, arr.addr, sizeof(arr))
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proc readUInt64(self: PeonVM, idx: int): PeonObject =
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## Reads a constant from the
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## chunk's constant table and
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## returns a Peon object. Assumes
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## the constant is an UInt64
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var arr = [self.chunk.consts[idx], self.chunk.consts[idx + 1],
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self.chunk.consts[idx + 2], self.chunk.consts[idx + 3],
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self.chunk.consts[idx + 4], self.chunk.consts[idx + 5],
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self.chunk.consts[idx + 6], self.chunk.consts[idx + 7],
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]
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result = PeonObject(kind: UInt64)
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copyMem(result.uLong.addr, arr.addr, sizeof(arr))
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proc readUInt32(self: PeonVM, idx: int): PeonObject =
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## Reads a constant from the
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## chunk's constant table and
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## returns a Peon object. Assumes
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## the constant is an UInt32
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var arr = [self.chunk.consts[idx], self.chunk.consts[idx + 1],
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self.chunk.consts[idx + 2], self.chunk.consts[idx + 3]]
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result = PeonObject(kind: UInt32)
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copyMem(result.uInt.addr, arr.addr, sizeof(arr))
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proc readInt32(self: PeonVM, idx: int): PeonObject =
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## Reads a constant from the
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## chunk's constant table and
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## returns a Peon object. Assumes
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## the constant is an Int32
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var arr = [self.chunk.consts[idx], self.chunk.consts[idx + 1],
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self.chunk.consts[idx + 2], self.chunk.consts[idx + 3]]
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result = PeonObject(kind: Int32)
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copyMem(result.`int`.addr, arr.addr, sizeof(arr))
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proc dispatch*(self: PeonVM) =
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## Main bytecode dispatch loop
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var instruction: OpCode
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while true:
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instruction = OpCode(self.readByte())
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when DEBUG_TRACE_VM:
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echo &"IP: {self.ip}"
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echo &"SP: {self.stack.high()}"
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echo &"Stack: {self.stack}"
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echo &"Instruction: {instruction}"
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discard readLine stdin
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case instruction:
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# Constant loading
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of LoadTrue:
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self.push(self.getBool(true))
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of LoadFalse:
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self.push(self.getBool(false))
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of LoadNan:
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self.push(self.getNan())
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of LoadNil:
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self.push(self.getNil())
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of LoadInf:
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self.push(self.getInf(true))
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of LoadInt64:
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self.push(self.readInt64(int(self.readLong())))
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of LoadUInt64:
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self.push(self.readUInt64(int(self.readLong())))
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of LoadUInt32:
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self.push(self.readUInt32(int(self.readLong())))
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of Call:
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# Calls a function. The calling convention for peon
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# functions is pretty simple: the return address sits
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# at the bottom of the stack frame, then follow the
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# arguments and all temporaries/local variables
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let newIp = self.readLong()
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# We do this because if we immediately changed
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# the instruction pointer, we'd read the wrong
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# value for the argument count. Storing it and
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# changing it later fixes this issue
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self.frames.add(int(self.readLong()))
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self.ip = int(newIp)
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of OpCode.Return:
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# Returns from a void function or terminates the
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# program entirely if we're at the topmost frame
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if self.frames.len() > 1:
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let frame = self.frames.pop()
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for i in countdown(self.stack.high(), frame):
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discard self.pop()
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self.ip = int(self.pop().uInt)
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else:
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return
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of ReturnValue:
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# Returns from a function which has a return value,
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# pushing it on the stack
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let retVal = self.pop()
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let frame = self.frames.pop()
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for i in countdown(frame, 1):
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discard self.pop()
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self.ip = int(self.pop().uInt)
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self.push(retVal)
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of StoreVar:
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# Stores the value at the top of the stack
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# into the given stack index
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self.set(int(self.readLong()), self.pop())
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of StoreHeap:
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self.heapVars.add(self.pop())
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of LoadHeap:
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self.push(self.heapVars[self.readLong()])
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of LoadVar:
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self.push(self.get(int(self.readLong())))
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of NoOp:
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continue
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of Pop:
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discard self.pop()
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of PopN:
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for _ in 0..<int(self.readLong()):
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discard self.pop()
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of Jump:
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self.ip = int(self.readShort())
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of JumpForwards:
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self.ip += int(self.readShort())
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of JumpBackwards:
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self.ip -= int(self.readShort())
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of JumpIfFalse:
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if not self.peek().boolean:
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self.ip += int(self.readShort())
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of JumpIfTrue:
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if self.peek().boolean:
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self.ip += int(self.readShort())
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of JumpIfFalsePop:
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if not self.peek().boolean:
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self.ip += int(self.readShort())
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discard self.pop()
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of JumpIfFalseOrPop:
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if not self.peek().boolean:
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self.ip += int(self.readShort())
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else:
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discard self.pop()
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of LongJumpIfFalse:
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if not self.peek().boolean:
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self.ip += int(self.readLong())
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of LongJumpIfFalsePop:
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if not self.peek().boolean:
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self.ip += int(self.readLong())
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discard self.pop()
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of LongJumpForwards:
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self.ip += int(self.readLong())
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of LongJumpBackwards:
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self.ip -= int(self.readLong())
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of LongJump:
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self.ip = int(self.readLong())
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of LongJumpIfFalseOrPop:
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if not self.peek().boolean:
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self.ip += int(self.readLong())
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else:
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discard self.pop()
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else:
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discard
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proc run*(self: PeonVM, chunk: Chunk) =
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## Executes a piece of Peon bytecode.
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self.chunk = chunk
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self.frames = @[0]
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self.stack = @[]
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self.ip = 0
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self.dispatch()
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