405 lines
13 KiB
Python
405 lines
13 KiB
Python
# Chapter 3 - Code generation to LLVM IR
|
|
|
|
from collections import namedtuple
|
|
from enum import Enum
|
|
|
|
import llvmlite.ir as ir
|
|
|
|
# Each token is a tuple of kind and value. kind is one of the enumeration values
|
|
# in TokenKind. value is the textual value of the token in the input.
|
|
class TokenKind(Enum):
|
|
EOF = -1
|
|
DEF = -2
|
|
EXTERN = -3
|
|
IDENTIFIER = -4
|
|
NUMBER = -5
|
|
OPERATOR = -6
|
|
|
|
|
|
Token = namedtuple('Token', 'kind value')
|
|
|
|
|
|
class Lexer(object):
|
|
"""Lexer for Kaleidoscope.
|
|
|
|
Initialize the lexer with a string buffer. tokens() returns a generator that
|
|
can be queried for tokens. The generator will emit an EOF token before
|
|
stopping.
|
|
"""
|
|
def __init__(self, buf):
|
|
assert len(buf) >= 1
|
|
self.buf = buf
|
|
self.pos = 0
|
|
self.lastchar = self.buf[0]
|
|
|
|
def tokens(self):
|
|
while self.lastchar:
|
|
# Skip whitespace
|
|
while self.lastchar.isspace():
|
|
self._advance()
|
|
# Identifier or keyword
|
|
if self.lastchar.isalpha():
|
|
id_str = ''
|
|
while self.lastchar.isalnum():
|
|
id_str += self.lastchar
|
|
self._advance()
|
|
if id_str == 'def':
|
|
yield Token(kind=TokenKind.DEF, value=id_str)
|
|
elif id_str == 'extern':
|
|
yield Token(kind=TokenKind.EXTERN, value=id_str)
|
|
else:
|
|
yield Token(kind=TokenKind.IDENTIFIER, value=id_str)
|
|
# Number
|
|
elif self.lastchar.isdigit() or self.lastchar == '.':
|
|
num_str = ''
|
|
while self.lastchar.isdigit() or self.lastchar == '.':
|
|
num_str += self.lastchar
|
|
self._advance()
|
|
yield Token(kind=TokenKind.NUMBER, value=num_str)
|
|
# Comment
|
|
elif self.lastchar == '#':
|
|
self._advance()
|
|
while self.lastchar and self.lastchar not in '\r\n':
|
|
self._advance()
|
|
elif self.lastchar:
|
|
# Some other char
|
|
yield Token(kind=TokenKind.OPERATOR, value=self.lastchar)
|
|
self._advance()
|
|
yield Token(kind=TokenKind.EOF, value='')
|
|
|
|
def _advance(self):
|
|
try:
|
|
self.pos += 1
|
|
self.lastchar = self.buf[self.pos]
|
|
except IndexError:
|
|
self.lastchar = ''
|
|
|
|
|
|
# AST hierarchy
|
|
class ASTNode(object):
|
|
def dump(self, indent=0):
|
|
raise NotImplementedError
|
|
|
|
|
|
class ExprAST(ASTNode):
|
|
pass
|
|
|
|
|
|
class NumberExprAST(ExprAST):
|
|
def __init__(self, val):
|
|
self.val = val
|
|
|
|
def dump(self, indent=0):
|
|
return '{0}{1}[{2}]'.format(
|
|
' ' * indent, self.__class__.__name__, self.val)
|
|
|
|
|
|
class VariableExprAST(ExprAST):
|
|
def __init__(self, name):
|
|
self.name = name
|
|
|
|
def dump(self, indent=0):
|
|
return '{0}{1}[{2}]'.format(
|
|
' ' * indent, self.__class__.__name__, self.name)
|
|
|
|
|
|
class BinaryExprAST(ExprAST):
|
|
def __init__(self, op, lhs, rhs):
|
|
self.op = op
|
|
self.lhs = lhs
|
|
self.rhs = rhs
|
|
|
|
def dump(self, indent=0):
|
|
s = '{0}{1}[{2}]\n'.format(
|
|
' ' * indent, self.__class__.__name__, self.op)
|
|
s += self.lhs.dump(indent + 2) + '\n'
|
|
s += self.rhs.dump(indent + 2)
|
|
return s
|
|
|
|
|
|
class CallExprAST(ExprAST):
|
|
def __init__(self, callee, args):
|
|
self.callee = callee
|
|
self.args = args
|
|
|
|
def dump(self, indent=0):
|
|
s = '{0}{1}[{2}]\n'.format(
|
|
' ' * indent, self.__class__.__name__, self.callee)
|
|
for arg in self.args:
|
|
s += arg.dump(indent + 2) + '\n'
|
|
return s[:-1] # snip out trailing '\n'
|
|
|
|
|
|
class PrototypeAST(ASTNode):
|
|
def __init__(self, name, argnames):
|
|
self.name = name
|
|
self.argnames = argnames
|
|
|
|
def dump(self, indent=0):
|
|
return '{0}{1}[{2}]'.format(
|
|
' ' * indent, self.__class__.__name__, ', '.join(self.argnames))
|
|
|
|
|
|
class FunctionAST(ASTNode):
|
|
def __init__(self, proto, body):
|
|
self.proto = proto
|
|
self.body = body
|
|
|
|
def dump(self, indent=0):
|
|
s = '{0}{1}[{2}]\n'.format(
|
|
' ' * indent, self.__class__.__name__, self.proto.dump())
|
|
s += self.body.dump(indent + 2) + '\n'
|
|
return s
|
|
|
|
|
|
class ParseError(Exception): pass
|
|
|
|
|
|
class Parser(object):
|
|
def __init__(self, buf):
|
|
self.token_generator = Lexer(buf).tokens()
|
|
self.cur_tok = None
|
|
self._get_next_token()
|
|
|
|
# toplevel ::= definition | external | expression | ';'
|
|
def parse_toplevel(self):
|
|
if self.cur_tok.kind == TokenKind.EXTERN:
|
|
return self._parse_external()
|
|
elif self.cur_tok.kind == TokenKind.DEF:
|
|
return self._parse_definition()
|
|
elif self._cur_tok_is_operator(';'):
|
|
self._get_next_token()
|
|
return None
|
|
else:
|
|
return self._parse_toplevel_expression()
|
|
|
|
def _get_next_token(self):
|
|
self.cur_tok = next(self.token_generator)
|
|
|
|
_precedence_map = {'<': 10, '+': 20, '-': 20, '*': 40}
|
|
|
|
def _cur_tok_precedence(self):
|
|
"""Get the operator precedence of the current token."""
|
|
try:
|
|
return Parser._precedence_map[self.cur_tok.value]
|
|
except KeyError:
|
|
return -1
|
|
|
|
def _cur_tok_is_operator(self, op):
|
|
"""Query whether the current token is the operator op"""
|
|
return (self.cur_tok.kind == TokenKind.OPERATOR and
|
|
self.cur_tok.value == op)
|
|
|
|
# identifierexpr
|
|
# ::= identifier
|
|
# ::= identifier '(' expression* ')'
|
|
def _parse_identifier_expr(self):
|
|
id_name = self.cur_tok.value
|
|
self._get_next_token()
|
|
# If followed by a '(' it's a call; otherwise, a simple variable ref.
|
|
if not self._cur_tok_is_operator('('):
|
|
return VariableExprAST(id_name)
|
|
|
|
self._get_next_token()
|
|
args = []
|
|
if not self._cur_tok_is_operator(')'):
|
|
while True:
|
|
args.append(self._parse_expression())
|
|
if self._cur_tok_is_operator(')'):
|
|
break
|
|
if not self._cur_tok_is_operator(','):
|
|
raise ParseError('Expected ")" or "," in argument list')
|
|
self._get_next_token()
|
|
|
|
self._get_next_token() # consume the ')'
|
|
return CallExprAST(id_name, args)
|
|
|
|
# numberexpr ::= number
|
|
def _parse_number_expr(self):
|
|
result = NumberExprAST(self.cur_tok.value)
|
|
self._get_next_token() # consume the number
|
|
return result
|
|
|
|
# parenexpr ::= '(' expression ')'
|
|
def _parse_paren_expr(self):
|
|
self._get_next_token() # consume the '('
|
|
expr = self._parse_expression()
|
|
if not self._cur_tok_is_operator(')'):
|
|
raise ParseError('Expected ")"')
|
|
self._get_next_token() # consume the ')'
|
|
return expr
|
|
|
|
# primary
|
|
# ::= identifierexpr
|
|
# ::= numberexpr
|
|
# ::= parenexpr
|
|
def _parse_primary(self):
|
|
if self.cur_tok.kind == TokenKind.IDENTIFIER:
|
|
return self._parse_identifier_expr()
|
|
elif self.cur_tok.kind == TokenKind.NUMBER:
|
|
return self._parse_number_expr()
|
|
elif self._cur_tok_is_operator('('):
|
|
return self._parse_paren_expr()
|
|
else:
|
|
raise ParseError('Unknown token when expecting an expression')
|
|
|
|
# binoprhs ::= (<binop> primary)*
|
|
def _parse_binop_rhs(self, expr_prec, lhs):
|
|
"""Parse the right-hand-side of a binary expression.
|
|
|
|
expr_prec: minimal precedence to keep going (precedence climbing).
|
|
lhs: AST of the left-hand-side.
|
|
"""
|
|
while True:
|
|
cur_prec = self._cur_tok_precedence()
|
|
# If this is a binary operator with precedence lower than the
|
|
# currently parsed sub-expression, bail out. If it binds at least
|
|
# as tightly, keep going.
|
|
# Note that the precedence of non-operators is defined to be -1,
|
|
# so this condition handles cases when the expression ended.
|
|
if cur_prec < expr_prec:
|
|
return lhs
|
|
op = self.cur_tok.value
|
|
self._get_next_token() # consume the operator
|
|
rhs = self._parse_primary()
|
|
|
|
next_prec = self._cur_tok_precedence()
|
|
# There are three options:
|
|
# 1. next_prec > cur_prec: we need to make a recursive call
|
|
# 2. next_prec == cur_prec: no need for a recursive call, the next
|
|
# iteration of this loop will handle it.
|
|
# 3. next_prec < cur_prec: no need for a recursive call, combine
|
|
# lhs and the next iteration will immediately bail out.
|
|
if cur_prec < next_prec:
|
|
rhs = self._parse_binop_rhs(cur_prec + 1, rhs)
|
|
|
|
# Merge lhs/rhs
|
|
lhs = BinaryExprAST(op, lhs, rhs)
|
|
|
|
# expression ::= primary binoprhs
|
|
def _parse_expression(self):
|
|
lhs = self._parse_primary()
|
|
# Start with precedence 0 because we want to bind any operator to the
|
|
# expression at this point.
|
|
return self._parse_binop_rhs(0, lhs)
|
|
|
|
# prototype ::= id '(' id* ')'
|
|
def _parse_prototype(self):
|
|
if self.cur_tok.kind != TokenKind.IDENTIFIER:
|
|
raise ParseError('Expected function name in prototype')
|
|
name = self.cur_tok.value
|
|
self._get_next_token() # consume the name
|
|
if not self._cur_tok_is_operator('('):
|
|
raise ParseError('Expected "(" in prototype')
|
|
self._get_next_token() # consume '('
|
|
argnames = []
|
|
while self.cur_tok.kind == TokenKind.IDENTIFIER:
|
|
argnames.append(self.cur_tok.value)
|
|
self._get_next_token()
|
|
if not self._cur_tok_is_operator(')'):
|
|
raise ParseError('Expected ")" in prototype')
|
|
self._get_next_token() # consume ')'
|
|
return PrototypeAST(name, argnames)
|
|
|
|
# external ::= 'extern' prototype
|
|
def _parse_external(self):
|
|
self._get_next_token() # consume 'extern'
|
|
return self._parse_prototype()
|
|
|
|
# definition ::= 'def' prototype expression
|
|
def _parse_definition(self):
|
|
self._get_next_token() # consume 'def'
|
|
proto = self._parse_prototype()
|
|
expr = self._parse_expression()
|
|
return FunctionAST(proto, expr)
|
|
|
|
# toplevel ::= expression
|
|
def _parse_toplevel_expression(self):
|
|
expr = self._parse_expression()
|
|
# Anonymous function
|
|
return FunctionAST(PrototypeAST('', []), expr)
|
|
|
|
|
|
class CodegenError(Exception): pass
|
|
|
|
|
|
class LLVMCodeGenerator(object):
|
|
def __init__(self):
|
|
"""Initialize the code generator.
|
|
|
|
This creates a new LLVM module into which code is generated. The
|
|
generate_code() method can be called multiple times. It adds the code
|
|
generated for this node into the module, and returns the module.
|
|
"""
|
|
self.module = ir.Module()
|
|
|
|
# Current IR builder.
|
|
self.builder = None
|
|
|
|
# Manages a symbol table while a function is being codegen'd. Maps var
|
|
# names to ir.Value.
|
|
self.func_symtab = {}
|
|
|
|
def generate_code(self, node):
|
|
assert isinstance(node, (PrototypeAST, FunctionAST))
|
|
self._codegen(node)
|
|
return self.module
|
|
|
|
def _codegen(self, node):
|
|
"""Node visitor. Dispathces upon node type.
|
|
|
|
For AST node of class Foo, calls self._codegen_Foo. Each visitor is
|
|
expected to return a llvmlite.ir.Value.
|
|
"""
|
|
method = 'visit_' + node.__class__.__name__
|
|
return getattr(self, method)(node)
|
|
|
|
def _codegen_NumberExprAST(self, node):
|
|
return self.builder.constant(ir.DoubleType(), float(node.val))
|
|
|
|
def _codegen_VariableExprAST(self, node):
|
|
return self.symtab[node.name]
|
|
|
|
def _codegen_PrototypeAST(self, node):
|
|
# Create a function type
|
|
func_ty = ir.FunctionType(ir.DoubleType(),
|
|
[ir.DoubleType() * len(node.argnames)])
|
|
|
|
# If a function with this name already exists in the module...
|
|
if node.name in self.module.globals:
|
|
# We only allow the case in which a declaration exists and now the
|
|
# function is defined (or redeclared) with the same number of args.
|
|
existing_func = self.module[node.name]
|
|
if not isinstance(existing_func, ir.Function):
|
|
raise CodegenError('Function/Global name collision', node.name)
|
|
if not existing_func.is_declaration():
|
|
raise CodegenError('Redifinition of {0}'.format(node.name))
|
|
if len(existing_func.function_type.args) != len(func_ty.args):
|
|
raise CodegenError(
|
|
'Redifinition with different number of arguments')
|
|
func = self.module.globals[node.name]
|
|
else:
|
|
# Otherwise create a new function
|
|
func = ir.Function(self.module, func_ty, node.name)
|
|
# Set function argument names from AST
|
|
for i in range(len(func.args)):
|
|
func.args[i].name = node.argnames[i]
|
|
return func
|
|
|
|
def _codegen_FunctionAST(self, node):
|
|
# Create the function skeleton from the prototype.
|
|
func = self._codegen(node.proto)
|
|
# Create the entry BB in the function and set the builder to it.
|
|
bb_entry = func.append_basic_block('entry')
|
|
self.builder = ir.IRBuilder(bb_entry)
|
|
|
|
# We're going to generate the function body now. Reset the symbol table.
|
|
self.func_symtab = {}
|
|
retval = self._codegen(node.body)
|
|
irbuilder.ret(retval)
|
|
return func
|
|
|
|
|
|
if __name__ == '__main__':
|
|
pass
|
|
|