247 lines
5.5 KiB
Python
247 lines
5.5 KiB
Python
"""The instruction set for Shogoth."""
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from abc import ABC
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from dataclasses import dataclass
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from typing import Union
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@dataclass
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class Label(object):
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name: str
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def __hash__(self):
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return hash(self.name)
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class Opcode(ABC):
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pass
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@dataclass
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class GOTO(Opcode):
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"""() -> ()
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Branch to another point within the same bytecode segment. The target MUST be
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within the same module range as the current function. Branching does NOT
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update the name or module of the current function.
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"""
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target: Union[int, Label]
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################################################################################
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# Stack manipulation
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################################################################################
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# https://wiki.laptop.org/go/Forth_stack_operators
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# https://www.forth.com/starting-forth/2-stack-manipulation-operators-arithmetic/
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# https://docs.oracle.com/javase/specs/jvms/se18/html/jvms-6.html#jvms-6.5.swap
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@dataclass
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class DUP(Opcode):
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"""(A, B, ...) -> (A, B, ...)
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Duplicate the top N items of the stack.
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"""
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nargs: int = 1
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@dataclass
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class ROT(Opcode):
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"""(A, B, ... Z) -> (Z, A, B, ...)
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Rotate the top N elements of the stack.
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"""
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nargs: int = 2
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@dataclass
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class DROP(Opcode):
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"""(*) -> ()
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Drop the top N items of the stack.
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"""
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nargs: int = 1
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@dataclass
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class SLOT(Opcode):
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"""(..., A) -> (A, ..., A)
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Copy the Nth (counting up from 0 at the bottom of the stack) item to the top
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of the stack. Intended to allow users to emulate (immutable) frame local
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slots for reused values.
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"""
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target: Union[int, Label]
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################################################################################
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# Functional abstraction
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################################################################################
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@dataclass
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class IDENTIFIERC(Opcode):
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"""() -> (IDENTIFIER)
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An inline constant which produces an identifier to the stack.
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Identifiers name functions, fields and types but are not strings.
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They are a VM-internal naming structure with reference to the module.
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"""
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val: str
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@dataclass
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class FUNREF(Opcode):
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"""(IDENTIFIER) -> (`FUNREF<... A to ... B>`)
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Construct a reference to a static codepoint.
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"""
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@dataclass
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class CALLF(Opcode):
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"""(`FUNREF<... A to ... B>`, ... A) -> (... B)
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Call [funref]
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Make a dynamic call to the function reference at the top of stack.
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The callee will see a stack containg only the provided `nargs`.
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A subsequent RETURN will return execution to the next point.
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Executing a `CALL` pushes the name and module path of the current function.
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"""
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nargs: int = 0
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@dataclass
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class RETURN(Opcode):
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"""(... A) -> ()
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Return to the source of the last `CALL`. The returnee will see the top
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`nargs` values of the present stack appended to theirs. All other values on
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the stack will be discarded.
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Executing a `RETURN` pops (restores) the name and module path of the current
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function back to that of the caller.
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If the call stack is empty, `RETURN` will exit the interpreter.
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"""
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@dataclass
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class CLOSUREF(Opcode):
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"""(`FUNREF<A, ... B to ... C>`, A) -> (`CLOSURE<... B to ... C>`)
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Construct a closure over the function reference at the top of the stack.
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This may produce nullary closures.
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"""
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nargs: int = 0
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@dataclass
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class CLOSUREC(Opcode):
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"""(`CLOSURE<A, ... B to ... C>`, A) -> (`CLOSURE<... B to ... C>`)
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Further close over the closure at the top of the stack. This may produce
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nullary closures.
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"""
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nargs: int = 0
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class CALLC(Opcode):
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"""(`CLOSURE<... A to ... B>`, ... A) -> (... B)
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Call [closure]
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Make a dynamic call to the closure at the top of stack. The callee will see
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a stack containg only the provided `nargs` and closed-overs. A subsequent
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RETURN will return execution to the next point.
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Executing a `CALL` pushes the name and module path of the current function.
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"""
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nargs: int = 0
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################################################################################
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# Structures
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################################################################################
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# FIXME: This lacks any sort of way to do dynamic type/field references
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@dataclass
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class TYPEREF(Opcode):
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"""(IDENTIFIER) -> (TYPEREF)
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Produces a TYPEREF to the type named by the provided IDENTIFIER.
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"""
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@dataclass
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class ARMREF(Opcode):
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"""(TYPEREF, IDENTIFIER) -> (VARIANTREF)
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Produce a VARIANTREF to an 'arm' of the given variant type.
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"""
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@dataclass
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class ARM(Opcode):
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"""(ARMTREF<a ⊢ A ⊂ B>, ...) -> (B)
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Construct an instance of an 'arm' of a variant.
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The type of the 'arm' is considered to be the type of the whole variant.
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The name and module path of the current function MUST match the name and
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module path of `VARIANTREF`. The arity of this opcode MUST match the arity
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of the arm. The signature of the arm MUST match the signature fo the top N
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of the stack.
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"""
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nargs: int = 0
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@dataclass
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class ATEST(Opcode):
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"""(ARMREF<a ⊢ A ⊂ B>, B) -> ()
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Test whether B is a given arm of a variant A .
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If it is, branch to the given target.
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Otherwise fall through.
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"""
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target: Union[int, Label]
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@dataclass
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class ALOAD(Opcode):
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"""(ARMREF<a ⊢ A ⊂ B>, B) -> (A)
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Load the value of the variant arm. VLOAD errors (undefined) if B is not
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within the variant. VLOAD errors (undefined) if the value in B is not an A -
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use VTEST as needed.
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"""
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@dataclass
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class BREAK(Opcode):
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"""Abort the interpreter."""
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