From 7e5a558163a150c93badca8c3381fb3e45e5e4fe Mon Sep 17 00:00:00 2001 From: Reid 'arrdem' McKenzie Date: Sat, 2 Jul 2022 00:35:03 -0600 Subject: [PATCH] Slam out a two-pass assembler --- .../shoggoth/src/python/ichor/__init__.py | 1 + .../shoggoth/src/python/ichor/assembler.py | 62 +++++++++++++++++++ .../shoggoth/src/python/ichor/bootstrap.py | 1 + .../test/python/ichor/test_assembler.py | 47 ++++++++++++++ 4 files changed, 111 insertions(+) create mode 100644 projects/shoggoth/src/python/ichor/assembler.py create mode 100644 projects/shoggoth/test/python/ichor/test_assembler.py diff --git a/projects/shoggoth/src/python/ichor/__init__.py b/projects/shoggoth/src/python/ichor/__init__.py index 375fa7c..c30965d 100644 --- a/projects/shoggoth/src/python/ichor/__init__.py +++ b/projects/shoggoth/src/python/ichor/__init__.py @@ -10,3 +10,4 @@ from ichor.bootstrap import * # noqa from ichor.impl import * # noqa from ichor.isa import * # noqa from ichor.typing import * # noqa +from ichor.assembler import * diff --git a/projects/shoggoth/src/python/ichor/assembler.py b/projects/shoggoth/src/python/ichor/assembler.py new file mode 100644 index 0000000..dc47df3 --- /dev/null +++ b/projects/shoggoth/src/python/ichor/assembler.py @@ -0,0 +1,62 @@ +#!/usr/bin/env python3 + +from dataclasses import dataclass +from random import choices +from string import ascii_lowercase, digits +from typing import List + +from ichor.isa import Opcode + + +@dataclass +class Label(object): + name: str + + def __hash__(self): + return hash(self.name) + +class FuncBuilder(object): + def __init__(self) -> None: + self._opcodes = [] + + def write(self, op: Opcode): + self._opcodes.append(op) + + def make_label(self, prefix=""): + frag = ''.join(choices(ascii_lowercase + digits, k=8)) + return Label(f"{prefix or 'gensym'}_{frag}") + + def set_label(self, label: Label): + self._opcodes.append(label) + + def build(self) -> List[Opcode]: + """Assemble the written body into fully resolved opcodes.""" + + # The trivial two-pass assembler. First pass removes labels from the + # opcode stream, marking where they occurred. + + labels = {} + unassembled = [] + for op in self._opcodes: + match op: + case Label(_) as l: + assert l not in labels # Label marks must be unique. + labels[l] = len(unassembled) + case o: + unassembled.append(o) + + # Second pass rewrites instructions (which can reference forwards OR + # backwards labels) with real targets instead of labels. + assembled = [] + for op in unassembled: + match op: + case Opcode.GOTO(Label(_) as l): + assembled.append(Opcode.GOTO(labels[l])) + + case Opcode.VTEST(Label(_) as l): + assembled.append(Opcode.VTEST(labels[l])) + + case o: + assembled.append(o) + + return assembled diff --git a/projects/shoggoth/src/python/ichor/bootstrap.py b/projects/shoggoth/src/python/ichor/bootstrap.py index d34b42f..40dc611 100644 --- a/projects/shoggoth/src/python/ichor/bootstrap.py +++ b/projects/shoggoth/src/python/ichor/bootstrap.py @@ -6,6 +6,7 @@ Hopefully no "real" interpreter ever uses this code, since it's obviously replac from ichor.isa import Opcode from ichor.state import Module, Variant +from ichor.assembler import FuncBuilder BOOTSTRAP = Module() diff --git a/projects/shoggoth/test/python/ichor/test_assembler.py b/projects/shoggoth/test/python/ichor/test_assembler.py new file mode 100644 index 0000000..c7deea5 --- /dev/null +++ b/projects/shoggoth/test/python/ichor/test_assembler.py @@ -0,0 +1,47 @@ +#!/usr/bin/env python3 + +from ichor import FuncBuilder, Opcode + +import pytest + +@pytest.fixture +def builder() -> FuncBuilder: + return FuncBuilder() + + +def test_forwards_label(builder: FuncBuilder): + l = builder.make_label() + builder.write(Opcode.GOTO(l)) + builder.write(Opcode.DROP(0)) # no-op + builder.set_label(l) + builder.write(Opcode.DROP(0)) # no-op + instrs = builder.build() + assert instrs == [ + Opcode.GOTO(2), + Opcode.DROP(0), + Opcode.DROP(0), + ] + + +def test_backwards_label(builder: FuncBuilder): + l = builder.make_label() + builder.set_label(l) + builder.write(Opcode.DROP(0)) # no-op + builder.write(Opcode.GOTO(l)) + instrs = builder.build() + assert instrs == [ + Opcode.DROP(0), + Opcode.GOTO(0), + ] + + +def test_self_label(builder: FuncBuilder): + l = builder.make_label() + builder.write(Opcode.DROP(0)) # no-op + builder.set_label(l) + builder.write(Opcode.GOTO(l)) + instrs = builder.build() + assert instrs == [ + Opcode.DROP(0), + Opcode.GOTO(1), + ]