rhai/src/optimizer.rs
Stephen Chung f49ff28b82 Fix test.
2021-11-28 10:49:48 +08:00

1205 lines
46 KiB
Rust

//! Module implementing the [`AST`] optimizer.
#![cfg(not(feature = "no_optimize"))]
use crate::ast::{Expr, OpAssignment, ScriptFnDef, Stmt, AST_OPTION_FLAGS::*};
use crate::engine::{
EvalState, Imports, KEYWORD_DEBUG, KEYWORD_EVAL, KEYWORD_FN_PTR, KEYWORD_PRINT, KEYWORD_TYPE_OF,
};
use crate::func::builtin::get_builtin_binary_op_fn;
use crate::func::hashing::get_hasher;
use crate::tokenizer::Token;
use crate::types::dynamic::AccessMode;
use crate::{
calc_fn_hash, calc_fn_params_hash, combine_hashes, Dynamic, Engine, FnPtr, ImmutableString,
Module, Position, Scope, Shared, StaticVec, AST,
};
#[cfg(feature = "no_std")]
use std::prelude::v1::*;
use std::{
any::TypeId,
hash::{Hash, Hasher},
mem,
ops::DerefMut,
};
#[cfg(not(feature = "no_closure"))]
use crate::engine::KEYWORD_IS_SHARED;
/// Level of optimization performed.
#[derive(Debug, Eq, PartialEq, Hash, Clone, Copy)]
pub enum OptimizationLevel {
/// No optimization performed.
None,
/// Only perform simple optimizations without evaluating functions.
Simple,
/// Full optimizations performed, including evaluating functions.
/// Take care that this may cause side effects as it essentially assumes that all functions are pure.
Full,
}
impl Default for OptimizationLevel {
#[inline(always)]
fn default() -> Self {
if cfg!(feature = "no_optimize") {
Self::None
} else {
Self::Simple
}
}
}
/// Mutable state throughout an optimization pass.
#[derive(Debug, Clone)]
struct OptimizerState<'a> {
/// Has the [`AST`] been changed during this pass?
changed: bool,
/// Collection of constants to use for eager function evaluations.
variables: StaticVec<(String, AccessMode, Option<Dynamic>)>,
/// Activate constants propagation?
propagate_constants: bool,
/// An [`Engine`] instance for eager function evaluation.
engine: &'a Engine,
/// [Module] containing script-defined functions.
lib: &'a [&'a Module],
/// Optimization level.
optimization_level: OptimizationLevel,
}
impl<'a> OptimizerState<'a> {
/// Create a new State.
#[inline(always)]
pub const fn new(
engine: &'a Engine,
lib: &'a [&'a Module],
optimization_level: OptimizationLevel,
) -> Self {
Self {
changed: false,
variables: StaticVec::new_const(),
propagate_constants: true,
engine,
lib,
optimization_level,
}
}
/// Set the [`AST`] state to be dirty (i.e. changed).
#[inline(always)]
pub fn set_dirty(&mut self) {
self.changed = true;
}
/// Set the [`AST`] state to be not dirty (i.e. unchanged).
#[inline(always)]
pub fn clear_dirty(&mut self) {
self.changed = false;
}
/// Is the [`AST`] dirty (i.e. changed)?
#[inline(always)]
pub const fn is_dirty(&self) -> bool {
self.changed
}
/// Prune the list of constants back to a specified size.
#[inline(always)]
pub fn restore_var(&mut self, len: usize) {
self.variables.truncate(len)
}
/// Add a new constant to the list.
#[inline(always)]
pub fn push_var(
&mut self,
name: impl Into<String>,
access: AccessMode,
value: Option<Dynamic>,
) {
self.variables.push((name.into(), access, value))
}
/// Look up a constant from the list.
#[inline]
pub fn find_constant(&self, name: impl AsRef<str>) -> Option<&Dynamic> {
if !self.propagate_constants {
return None;
}
let name = name.as_ref();
for (n, access, value) in self.variables.iter().rev() {
if n == name {
return match access {
AccessMode::ReadWrite => None,
AccessMode::ReadOnly => value.as_ref(),
};
}
}
None
}
/// Call a registered function
#[inline]
pub fn call_fn_with_constant_arguments(
&self,
fn_name: impl AsRef<str>,
arg_values: &mut [Dynamic],
) -> Option<Dynamic> {
self.engine
.call_native_fn(
&mut Imports::new(),
&mut EvalState::new(),
self.lib,
&fn_name,
calc_fn_hash(&fn_name, arg_values.len()),
&mut arg_values.iter_mut().collect::<StaticVec<_>>(),
false,
false,
Position::NONE,
)
.ok()
.map(|(v, _)| v)
}
// Has a system function a Rust-native override?
pub fn has_native_fn_override(&self, hash_script: u64, arg_types: &[TypeId]) -> bool {
let hash_params = calc_fn_params_hash(arg_types.iter().cloned());
let hash = combine_hashes(hash_script, hash_params);
// First check the global namespace and packages, but skip modules that are standard because
// they should never conflict with system functions.
self.engine.global_modules.iter().filter(|m| !m.standard).any(|m| m.contains_fn(hash))
// Then check sub-modules
|| self.engine.global_sub_modules.values().any(|m| m.contains_qualified_fn(hash))
}
}
/// Optimize a block of [statements][Stmt].
fn optimize_stmt_block(
mut statements: StaticVec<Stmt>,
state: &mut OptimizerState,
preserve_result: bool,
is_internal: bool,
reduce_return: bool,
) -> StaticVec<Stmt> {
if statements.is_empty() {
return statements;
}
let mut is_dirty = state.is_dirty();
let is_pure = if is_internal {
Stmt::is_internally_pure
} else {
Stmt::is_pure
};
loop {
state.clear_dirty();
let orig_constants_len = state.variables.len(); // Original number of constants in the state, for restore later
let orig_propagate_constants = state.propagate_constants;
// Remove everything following control flow breaking statements
let mut dead_code = false;
statements.retain(|stmt| {
if dead_code {
state.set_dirty();
false
} else if stmt.is_control_flow_break() {
dead_code = true;
true
} else {
true
}
});
// Optimize each statement in the block
statements.iter_mut().for_each(|stmt| {
match stmt {
Stmt::Var(value_expr, x, options, _) => {
if options.contains(AST_OPTION_CONSTANT) {
// Add constant literals into the state
optimize_expr(value_expr, state, false);
if value_expr.is_constant() {
state.push_var(
x.name.as_str(),
AccessMode::ReadOnly,
value_expr.get_literal_value(),
);
}
} else {
// Add variables into the state
optimize_expr(value_expr, state, false);
state.push_var(x.name.as_str(), AccessMode::ReadWrite, None);
}
}
// Optimize the statement
_ => optimize_stmt(stmt, state, preserve_result),
}
});
// Remove all pure statements except the last one
let mut index = 0;
let mut first_non_constant = statements
.iter()
.rev()
.enumerate()
.find_map(|(i, stmt)| match stmt {
stmt if !is_pure(stmt) => Some(i),
Stmt::Var(e, _, _, _) | Stmt::Expr(e) if !e.is_constant() => Some(i),
#[cfg(not(feature = "no_module"))]
Stmt::Import(e, _, _) if !e.is_constant() => Some(i),
_ => None,
})
.map_or(0, |n| statements.len() - n - 1);
while index < statements.len() {
if preserve_result && index >= statements.len() - 1 {
break;
} else {
match statements[index] {
ref stmt if is_pure(stmt) && index >= first_non_constant => {
state.set_dirty();
statements.remove(index);
}
ref stmt if stmt.is_pure() => {
state.set_dirty();
if index < first_non_constant {
first_non_constant -= 1;
}
statements.remove(index);
}
_ => index += 1,
}
}
}
// Remove all pure statements that do not return values at the end of a block.
// We cannot remove anything for non-pure statements due to potential side-effects.
if preserve_result {
loop {
match statements[..] {
// { return; } -> {}
[Stmt::Return(options, None, _)]
if reduce_return && !options.contains(AST_OPTION_BREAK_OUT) =>
{
state.set_dirty();
statements.clear();
}
[ref stmt] if !stmt.returns_value() && is_pure(stmt) => {
state.set_dirty();
statements.clear();
}
// { ...; return; } -> { ... }
[.., ref last_stmt, Stmt::Return(options, None, _)]
if reduce_return
&& !options.contains(AST_OPTION_BREAK_OUT)
&& !last_stmt.returns_value() =>
{
state.set_dirty();
statements.pop().expect(">= 2 elements");
}
// { ...; return val; } -> { ...; val }
[.., Stmt::Return(options, ref mut expr, pos)]
if reduce_return && !options.contains(AST_OPTION_BREAK_OUT) =>
{
state.set_dirty();
*statements.last_mut().expect(">= 2 elements") = if let Some(expr) = expr {
Stmt::Expr(mem::take(expr))
} else {
Stmt::Noop(pos)
};
}
// { ...; stmt; noop } -> done
[.., ref second_last_stmt, Stmt::Noop(_)]
if second_last_stmt.returns_value() =>
{
break
}
// { ...; stmt_that_returns; pure_non_value_stmt } -> { ...; stmt_that_returns; noop }
// { ...; stmt; pure_non_value_stmt } -> { ...; stmt }
[.., ref second_last_stmt, ref last_stmt]
if !last_stmt.returns_value() && is_pure(last_stmt) =>
{
state.set_dirty();
if second_last_stmt.returns_value() {
*statements.last_mut().expect(">= 2 elements") =
Stmt::Noop(last_stmt.position());
} else {
statements.pop().expect(">= 2 elements");
}
}
_ => break,
}
}
} else {
loop {
match statements[..] {
[ref stmt] if is_pure(stmt) => {
state.set_dirty();
statements.clear();
}
// { ...; return; } -> { ... }
[.., Stmt::Return(options, None, _)]
if reduce_return && !options.contains(AST_OPTION_BREAK_OUT) =>
{
state.set_dirty();
statements.pop().expect(">= 2 elements");
}
// { ...; return pure_val; } -> { ... }
[.., Stmt::Return(options, Some(ref expr), _)]
if reduce_return
&& !options.contains(AST_OPTION_BREAK_OUT)
&& expr.is_pure() =>
{
state.set_dirty();
statements.pop().expect(">= 2 elements");
}
[.., ref last_stmt] if is_pure(last_stmt) => {
state.set_dirty();
statements.pop().expect("not empty");
}
_ => break,
}
}
}
// Pop the stack and remove all the local constants
state.restore_var(orig_constants_len);
state.propagate_constants = orig_propagate_constants;
if !state.is_dirty() {
break;
}
is_dirty = true;
}
if is_dirty {
state.set_dirty();
}
statements.shrink_to_fit();
statements
}
/// Optimize a [statement][Stmt].
fn optimize_stmt(stmt: &mut Stmt, state: &mut OptimizerState, preserve_result: bool) {
match stmt {
// var = var op expr => var op= expr
Stmt::Assignment(x, _)
if x.1.is_none()
&& x.0.is_variable_access(true)
&& matches!(&x.2, Expr::FnCall(x2, _)
if Token::lookup_from_syntax(&x2.name).map(|t| t.has_op_assignment()).unwrap_or(false)
&& x2.args.len() == 2
&& x2.args[0].get_variable_name(true) == x.0.get_variable_name(true)
) =>
{
match x.2 {
Expr::FnCall(ref mut x2, _) => {
state.set_dirty();
let op = Token::lookup_from_syntax(&x2.name).expect("operator");
let op_assignment = op.make_op_assignment().expect("operator");
x.1 = Some(OpAssignment::new(op_assignment));
let value = mem::take(&mut x2.args[1]);
if let Expr::Stack(slot, pos) = value {
let value = mem::take(x2.constants.get_mut(slot).expect("valid slot"));
x.2 = Expr::from_dynamic(value, pos);
} else {
x.2 = value;
}
}
_ => unreachable!(),
}
}
// expr op= expr
Stmt::Assignment(x, _) => match x.0 {
Expr::Variable(_, _, _) => optimize_expr(&mut x.2, state, false),
_ => {
optimize_expr(&mut x.0, state, false);
optimize_expr(&mut x.2, state, false);
}
},
// if expr {}
Stmt::If(condition, x, _) if x.0.is_empty() && x.1.is_empty() => {
state.set_dirty();
let pos = condition.position();
let mut expr = mem::take(condition);
optimize_expr(&mut expr, state, false);
*stmt = if preserve_result {
// -> { expr, Noop }
Stmt::Block([Stmt::Expr(expr), Stmt::Noop(pos)].into(), pos)
} else {
// -> expr
Stmt::Expr(expr)
};
}
// if false { if_block } -> Noop
Stmt::If(Expr::BoolConstant(false, pos), x, _) if x.1.is_empty() => {
state.set_dirty();
*stmt = Stmt::Noop(*pos);
}
// if false { if_block } else { else_block } -> else_block
Stmt::If(Expr::BoolConstant(false, _), x, _) => {
state.set_dirty();
let else_block = mem::take(&mut *x.1);
*stmt = match optimize_stmt_block(else_block, state, preserve_result, true, false) {
statements if statements.is_empty() => Stmt::Noop(x.1.position()),
statements => Stmt::Block(statements.into_boxed_slice(), x.1.position()),
}
}
// if true { if_block } else { else_block } -> if_block
Stmt::If(Expr::BoolConstant(true, _), x, _) => {
state.set_dirty();
let if_block = mem::take(&mut *x.0);
*stmt = match optimize_stmt_block(if_block, state, preserve_result, true, false) {
statements if statements.is_empty() => Stmt::Noop(x.0.position()),
statements => Stmt::Block(statements.into_boxed_slice(), x.0.position()),
}
}
// if expr { if_block } else { else_block }
Stmt::If(condition, x, _) => {
optimize_expr(condition, state, false);
let if_block = mem::take(x.0.deref_mut());
*x.0 = optimize_stmt_block(if_block, state, preserve_result, true, false);
let else_block = mem::take(x.1.deref_mut());
*x.1 = optimize_stmt_block(else_block, state, preserve_result, true, false);
}
// switch const { ... }
Stmt::Switch(match_expr, x, pos) if match_expr.is_constant() => {
let value = match_expr.get_literal_value().expect("constant");
let hasher = &mut get_hasher();
value.hash(hasher);
let hash = hasher.finish();
state.set_dirty();
let table = &mut x.0;
if let Some(block) = table.get_mut(&hash) {
if let Some(mut condition) = mem::take(&mut block.0) {
// switch const { case if condition => stmt, _ => def } => if condition { stmt } else { def }
optimize_expr(&mut condition, state, false);
let def_block = mem::take(&mut *x.1);
let def_stmt = optimize_stmt_block(def_block, state, true, true, false);
let def_pos = if x.1.position().is_none() {
*pos
} else {
x.1.position()
};
*stmt = Stmt::If(
condition,
Box::new((
mem::take(&mut block.1),
Stmt::Block(def_stmt.into_boxed_slice(), def_pos).into(),
)),
match_expr.position(),
);
} else {
// Promote the matched case
let new_pos = block.1.position();
let statements = mem::take(&mut *block.1);
let statements = optimize_stmt_block(statements, state, true, true, false);
*stmt = Stmt::Block(statements.into_boxed_slice(), new_pos);
}
} else {
// Promote the default case
let def_block = mem::take(&mut *x.1);
let def_stmt = optimize_stmt_block(def_block, state, true, true, false);
let def_pos = if x.1.position().is_none() {
*pos
} else {
x.1.position()
};
*stmt = Stmt::Block(def_stmt.into_boxed_slice(), def_pos);
}
}
// switch
Stmt::Switch(match_expr, x, _) => {
optimize_expr(match_expr, state, false);
x.0.values_mut().for_each(|block| {
let condition = mem::take(&mut block.0).map_or_else(
|| Expr::Unit(Position::NONE),
|mut condition| {
optimize_expr(&mut condition, state, false);
condition
},
);
match condition {
Expr::Unit(_) | Expr::BoolConstant(true, _) => (),
_ => {
block.0 = Some(condition);
*block.1 = optimize_stmt_block(
mem::take(block.1.deref_mut()),
state,
preserve_result,
true,
false,
);
}
}
});
// Remove false cases
while let Some((&key, _)) = x.0.iter().find(|(_, block)| match block.0 {
Some(Expr::BoolConstant(false, _)) => true,
_ => false,
}) {
state.set_dirty();
x.0.remove(&key);
}
let def_block = mem::take(x.1.deref_mut());
*x.1 = optimize_stmt_block(def_block, state, preserve_result, true, false);
}
// while false { block } -> Noop
Stmt::While(Expr::BoolConstant(false, pos), _, _) => {
state.set_dirty();
*stmt = Stmt::Noop(*pos)
}
// while expr { block }
Stmt::While(condition, body, _) => {
optimize_expr(condition, state, false);
if let Expr::BoolConstant(true, pos) = condition {
*condition = Expr::Unit(*pos);
}
let block = mem::take(body.as_mut().deref_mut());
*body.as_mut().deref_mut() = optimize_stmt_block(block, state, false, true, false);
if body.len() == 1 {
match body[0] {
// while expr { break; } -> { expr; }
Stmt::BreakLoop(options, pos) if options.contains(AST_OPTION_BREAK_OUT) => {
// Only a single break statement - turn into running the guard expression once
state.set_dirty();
if !condition.is_unit() {
let mut statements = vec![Stmt::Expr(mem::take(condition))];
if preserve_result {
statements.push(Stmt::Noop(pos))
}
*stmt = Stmt::Block(statements.into_boxed_slice(), pos);
} else {
*stmt = Stmt::Noop(pos);
};
}
_ => (),
}
}
}
// do { block } while false | do { block } until true -> { block }
Stmt::Do(body, Expr::BoolConstant(x, _), options, _)
if *x == options.contains(AST_OPTION_NEGATED) =>
{
state.set_dirty();
let block_pos = body.position();
let block = mem::take(body.as_mut().deref_mut());
*stmt = Stmt::Block(
optimize_stmt_block(block, state, false, true, false).into_boxed_slice(),
block_pos,
);
}
// do { block } while|until expr
Stmt::Do(body, condition, _, _) => {
optimize_expr(condition, state, false);
let block = mem::take(body.as_mut().deref_mut());
*body.as_mut().deref_mut() = optimize_stmt_block(block, state, false, true, false);
}
// for id in expr { block }
Stmt::For(iterable, x, _) => {
optimize_expr(iterable, state, false);
let body = mem::take(x.2.deref_mut());
*x.2 = optimize_stmt_block(body, state, false, true, false);
}
// let id = expr;
Stmt::Var(expr, _, options, _) if !options.contains(AST_OPTION_CONSTANT) => {
optimize_expr(expr, state, false)
}
// import expr as var;
#[cfg(not(feature = "no_module"))]
Stmt::Import(expr, _, _) => optimize_expr(expr, state, false),
// { block }
Stmt::Block(statements, pos) => {
let statements = mem::take(statements).into_vec().into();
let mut block = optimize_stmt_block(statements, state, preserve_result, true, false);
match block.as_mut_slice() {
[] => {
state.set_dirty();
*stmt = Stmt::Noop(*pos);
}
// Only one statement - promote
[s] => {
state.set_dirty();
*stmt = mem::take(s);
}
_ => *stmt = Stmt::Block(block.into_boxed_slice(), *pos),
}
}
// try { pure try_block } catch ( var ) { catch_block } -> try_block
Stmt::TryCatch(x, _) if x.0.iter().all(Stmt::is_pure) => {
// If try block is pure, there will never be any exceptions
state.set_dirty();
let try_pos = x.0.position();
let try_block = mem::take(&mut *x.0);
*stmt = Stmt::Block(
optimize_stmt_block(try_block, state, false, true, false).into_boxed_slice(),
try_pos,
);
}
// try { try_block } catch ( var ) { catch_block }
Stmt::TryCatch(x, _) => {
let try_block = mem::take(x.0.deref_mut());
*x.0 = optimize_stmt_block(try_block, state, false, true, false);
let catch_block = mem::take(x.2.deref_mut());
*x.2 = optimize_stmt_block(catch_block, state, false, true, false);
}
// func(...)
Stmt::Expr(expr @ Expr::FnCall(_, _)) => {
optimize_expr(expr, state, false);
match expr {
Expr::FnCall(x, pos) => {
state.set_dirty();
*stmt = Stmt::FnCall(mem::take(x), *pos);
}
_ => (),
}
}
// {}
Stmt::Expr(Expr::Stmt(x)) if x.is_empty() => {
state.set_dirty();
*stmt = Stmt::Noop(x.position());
}
// {...};
Stmt::Expr(Expr::Stmt(x)) => {
state.set_dirty();
*stmt = mem::take(x.as_mut()).into();
}
// expr;
Stmt::Expr(expr) => optimize_expr(expr, state, false),
// return expr;
Stmt::Return(_, Some(ref mut expr), _) => optimize_expr(expr, state, false),
// All other statements - skip
_ => (),
}
}
/// Optimize an [expression][Expr].
fn optimize_expr(expr: &mut Expr, state: &mut OptimizerState, chaining: bool) {
// These keywords are handled specially
const DONT_EVAL_KEYWORDS: &[&str] = &[
KEYWORD_PRINT, // side effects
KEYWORD_DEBUG, // side effects
KEYWORD_EVAL, // arbitrary scripts
];
let _chaining = chaining;
match expr {
// {}
Expr::Stmt(x) if x.is_empty() => { state.set_dirty(); *expr = Expr::Unit(x.position()) }
// { stmt; ... } - do not count promotion as dirty because it gets turned back into an array
Expr::Stmt(x) => {
*x.as_mut().deref_mut() =
optimize_stmt_block(mem::take(x.as_mut().deref_mut()), state, true, true, false);
// { Stmt(Expr) } - promote
match x.as_mut().as_mut() {
[ Stmt::Expr(e) ] => { state.set_dirty(); *expr = mem::take(e); }
_ => ()
}
}
// lhs.rhs
#[cfg(not(feature = "no_object"))]
Expr::Dot(x,_, _) if !_chaining => match (&mut x.lhs, &mut x.rhs) {
// map.string
(Expr::Map(m, pos), Expr::Property(p)) if m.0.iter().all(|(_, x)| x.is_pure()) => {
let prop = p.2.0.as_str();
// Map literal where everything is pure - promote the indexed item.
// All other items can be thrown away.
state.set_dirty();
*expr = mem::take(&mut m.0).into_iter().find(|(x, _)| x.name == prop)
.map(|(_, mut expr)| { expr.set_position(*pos); expr })
.unwrap_or_else(|| Expr::Unit(*pos));
}
// var.rhs
(Expr::Variable(_, _, _), rhs) => optimize_expr(rhs, state, true),
// lhs.rhs
(lhs, rhs) => { optimize_expr(lhs, state, false); optimize_expr(rhs, state, true); }
}
// ....lhs.rhs
#[cfg(not(feature = "no_object"))]
Expr::Dot(x,_, _) => { optimize_expr(&mut x.lhs, state, false); optimize_expr(&mut x.rhs, state, _chaining); }
// lhs[rhs]
#[cfg(not(feature = "no_index"))]
Expr::Index(x, _, _) if !_chaining => match (&mut x.lhs, &mut x.rhs) {
// array[int]
(Expr::Array(a, pos), Expr::IntegerConstant(i, _))
if *i >= 0 && (*i as usize) < a.len() && a.iter().all(Expr::is_pure) =>
{
// Array literal where everything is pure - promote the indexed item.
// All other items can be thrown away.
state.set_dirty();
let mut result = mem::take(&mut a[*i as usize]);
result.set_position(*pos);
*expr = result;
}
// array[-int]
(Expr::Array(a, pos), Expr::IntegerConstant(i, _))
if *i < 0 && i.checked_abs().map(|n| n as usize <= a.len()).unwrap_or(false) && a.iter().all(Expr::is_pure) =>
{
// Array literal where everything is pure - promote the indexed item.
// All other items can be thrown away.
state.set_dirty();
let index = a.len() - i.abs() as usize;
let mut result = mem::take(&mut a[index]);
result.set_position(*pos);
*expr = result;
}
// map[string]
(Expr::Map(m, pos), Expr::StringConstant(s, _)) if m.0.iter().all(|(_, x)| x.is_pure()) => {
// Map literal where everything is pure - promote the indexed item.
// All other items can be thrown away.
state.set_dirty();
*expr = mem::take(&mut m.0).into_iter().find(|(x, _)| x.name.as_str() == s.as_str())
.map(|(_, mut expr)| { expr.set_position(*pos); expr })
.unwrap_or_else(|| Expr::Unit(*pos));
}
// int[int]
(Expr::IntegerConstant(n, pos), Expr::IntegerConstant(i, _)) if *i >= 0 && (*i as usize) < (std::mem::size_of_val(n) * 8) => {
// Bit-field literal indexing - get the bit
state.set_dirty();
*expr = Expr::BoolConstant((*n & (1 << (*i as usize))) != 0, *pos);
}
// int[-int]
(Expr::IntegerConstant(n, pos), Expr::IntegerConstant(i, _)) if *i < 0 && i.checked_abs().map(|i| i as usize <= (std::mem::size_of_val(n) * 8)).unwrap_or(false) => {
// Bit-field literal indexing - get the bit
state.set_dirty();
*expr = Expr::BoolConstant((*n & (1 << (std::mem::size_of_val(n) * 8 - i.abs() as usize))) != 0, *pos);
}
// string[int]
(Expr::StringConstant(s, pos), Expr::IntegerConstant(i, _)) if *i >= 0 && (*i as usize) < s.chars().count() => {
// String literal indexing - get the character
state.set_dirty();
*expr = Expr::CharConstant(s.chars().nth(*i as usize).expect("valid index"), *pos);
}
// string[-int]
(Expr::StringConstant(s, pos), Expr::IntegerConstant(i, _)) if *i < 0 && i.checked_abs().map(|n| n as usize <= s.chars().count()).unwrap_or(false) => {
// String literal indexing - get the character
state.set_dirty();
*expr = Expr::CharConstant(s.chars().rev().nth(i.abs() as usize - 1).expect("valid index"), *pos);
}
// var[rhs]
(Expr::Variable(_, _, _), rhs) => optimize_expr(rhs, state, true),
// lhs[rhs]
(lhs, rhs) => { optimize_expr(lhs, state, false); optimize_expr(rhs, state, true); }
},
// ...[lhs][rhs]
#[cfg(not(feature = "no_index"))]
Expr::Index(x, _, _) => { optimize_expr(&mut x.lhs, state, false); optimize_expr(&mut x.rhs, state, _chaining); }
// ``
Expr::InterpolatedString(x, pos) if x.is_empty() => {
state.set_dirty();
*expr = Expr::StringConstant(state.engine.const_empty_string(), *pos);
}
// `...`
Expr::InterpolatedString(x, _) if x.len() == 1 && matches!(x[0], Expr::StringConstant(_, _)) => {
state.set_dirty();
*expr = mem::take(&mut x[0]);
}
// `... ${ ... } ...`
Expr::InterpolatedString(x, _) => {
x.iter_mut().for_each(|expr| optimize_expr(expr, state, false));
let mut n = 0;
// Merge consecutive strings
while n < x.len()-1 {
match (mem::take(&mut x[n]), mem::take(&mut x[n+1])) {
(Expr::StringConstant(mut s1, pos), Expr::StringConstant(s2, _)) => {
s1 += s2;
x[n] = Expr::StringConstant(s1, pos);
x.remove(n+1);
state.set_dirty();
}
(expr1, Expr::Unit(_)) => {
x[n] = expr1;
x.remove(n+1);
state.set_dirty();
}
(Expr::Unit(_), expr2) => {
x[n+1] = expr2;
x.remove(n);
state.set_dirty();
}
(expr1, Expr::StringConstant(s, _)) if s.is_empty() => {
x[n] = expr1;
x.remove(n+1);
state.set_dirty();
}
(Expr::StringConstant(s, _), expr2) if s.is_empty()=> {
x[n+1] = expr2;
x.remove(n);
state.set_dirty();
}
(expr1, expr2) => {
x[n] = expr1;
x[n+1] = expr2;
n += 1;
}
}
}
x.shrink_to_fit();
}
// [ constant .. ]
#[cfg(not(feature = "no_index"))]
Expr::Array(_, _) if expr.is_constant() => {
state.set_dirty();
*expr = Expr::DynamicConstant(expr.get_literal_value().expect("constant").into(), expr.position());
}
// [ items .. ]
#[cfg(not(feature = "no_index"))]
Expr::Array(x, _) => x.iter_mut().for_each(|expr| optimize_expr(expr, state, false)),
// #{ key:constant, .. }
#[cfg(not(feature = "no_object"))]
Expr::Map(_, _) if expr.is_constant() => {
state.set_dirty();
*expr = Expr::DynamicConstant(expr.get_literal_value().expect("constant").into(), expr.position());
}
// #{ key:value, .. }
#[cfg(not(feature = "no_object"))]
Expr::Map(x, _) => x.0.iter_mut().for_each(|(_, expr)| optimize_expr(expr, state, false)),
// lhs && rhs
Expr::And(x, _) => match (&mut x.lhs, &mut x.rhs) {
// true && rhs -> rhs
(Expr::BoolConstant(true, _), rhs) => {
state.set_dirty();
optimize_expr(rhs, state, false);
*expr = mem::take(rhs);
}
// false && rhs -> false
(Expr::BoolConstant(false, pos), _) => {
state.set_dirty();
*expr = Expr::BoolConstant(false, *pos);
}
// lhs && true -> lhs
(lhs, Expr::BoolConstant(true, _)) => {
state.set_dirty();
optimize_expr(lhs, state, false);
*expr = mem::take(lhs);
}
// lhs && rhs
(lhs, rhs) => { optimize_expr(lhs, state, false); optimize_expr(rhs, state, false); }
},
// lhs || rhs
Expr::Or(ref mut x, _) => match (&mut x.lhs, &mut x.rhs) {
// false || rhs -> rhs
(Expr::BoolConstant(false, _), rhs) => {
state.set_dirty();
optimize_expr(rhs, state, false);
*expr = mem::take(rhs);
}
// true || rhs -> true
(Expr::BoolConstant(true, pos), _) => {
state.set_dirty();
*expr = Expr::BoolConstant(true, *pos);
}
// lhs || false
(lhs, Expr::BoolConstant(false, _)) => {
state.set_dirty();
optimize_expr(lhs, state, false);
*expr = mem::take(lhs);
}
// lhs || rhs
(lhs, rhs) => { optimize_expr(lhs, state, false); optimize_expr(rhs, state, false); }
},
// eval!
Expr::FnCall(x, _) if x.name == KEYWORD_EVAL => {
state.propagate_constants = false;
}
// Fn
Expr::FnCall(x, pos)
if !x.is_qualified() // Non-qualified
&& state.optimization_level == OptimizationLevel::Simple // simple optimizations
&& x.args.len() == 1
&& x.args[0].is_constant()
&& x.name == KEYWORD_FN_PTR
=> {
let fn_name = match x.args[0] {
Expr::Stack(slot, _) => Some(x.constants[slot].clone()),
Expr::StringConstant(ref s, _) => Some(s.clone().into()),
_ => None
};
if let Some(fn_name) = fn_name {
if fn_name.is::<ImmutableString>() {
state.set_dirty();
let fn_ptr = FnPtr::new_unchecked(
fn_name.as_str_ref().expect("`ImmutableString`").into(),
StaticVec::new_const()
);
*expr = Expr::DynamicConstant(Box::new(fn_ptr.into()), *pos);
}
}
}
// Do not call some special keywords
Expr::FnCall(x, _) if DONT_EVAL_KEYWORDS.contains(&x.name.as_ref()) => {
x.args.iter_mut().for_each(|a| optimize_expr(a, state, false));
}
// Call built-in operators
Expr::FnCall(x, pos)
if !x.is_qualified() // Non-qualified
&& state.optimization_level == OptimizationLevel::Simple // simple optimizations
&& x.args.iter().all(Expr::is_constant) // all arguments are constants
//&& !is_valid_identifier(x.name.chars()) // cannot be scripted
=> {
let arg_values = &mut x.args.iter().map(|e| match e {
Expr::Stack(slot, _) => x.constants[*slot].clone(),
_ => e.get_literal_value().expect("constant")
}).collect::<StaticVec<_>>();
let arg_types: StaticVec<_> = arg_values.iter().map(Dynamic::type_id).collect();
match x.name.as_str() {
KEYWORD_TYPE_OF if arg_values.len() == 1 => {
state.set_dirty();
*expr = Expr::from_dynamic(state.engine.map_type_name(arg_values[0].type_name()).into(), *pos);
return;
}
#[cfg(not(feature = "no_closure"))]
KEYWORD_IS_SHARED if arg_values.len() == 1 => {
state.set_dirty();
*expr = Expr::from_dynamic(Dynamic::FALSE, *pos);
return;
}
// Overloaded operators can override built-in.
_ if x.args.len() == 2 && !state.has_native_fn_override(x.hashes.native, arg_types.as_ref()) => {
if let Some(result) = get_builtin_binary_op_fn(x.name.as_ref(), &arg_values[0], &arg_values[1])
.and_then(|f| {
let context = (state.engine, x.name.as_str(), state.lib).into();
let (first, second) = arg_values.split_first_mut().expect("not empty");
(f)(context, &mut [ first, &mut second[0] ]).ok()
}) {
state.set_dirty();
*expr = Expr::from_dynamic(result, *pos);
return;
}
}
_ => ()
}
x.args.iter_mut().for_each(|a| optimize_expr(a, state, false));
// Move constant arguments
let constants = &mut x.constants;
x.args.iter_mut().for_each(|arg| {
if let Some(value) = arg.get_literal_value() {
state.set_dirty();
constants.push(value);
*arg = Expr::Stack(constants.len()-1, arg.position());
}
});
}
// Eagerly call functions
Expr::FnCall(x, pos)
if !x.is_qualified() // Non-qualified
&& state.optimization_level == OptimizationLevel::Full // full optimizations
&& x.args.iter().all(Expr::is_constant) // all arguments are constants
=> {
// First search for script-defined functions (can override built-in)
#[cfg(not(feature = "no_function"))]
let has_script_fn = state.lib.iter().any(|&m| m.get_script_fn(&x.name, x.args.len()).is_some());
#[cfg(feature = "no_function")]
let has_script_fn = false;
if !has_script_fn {
let arg_values = &mut x.args.iter().map(|e| match e {
Expr::Stack(slot, _) => x.constants[*slot].clone(),
_ => e.get_literal_value().expect("constant")
}).collect::<StaticVec<_>>();
let result = match x.name.as_str() {
KEYWORD_TYPE_OF if arg_values.len() == 1 => Some(state.engine.map_type_name(arg_values[0].type_name()).into()),
#[cfg(not(feature = "no_closure"))]
KEYWORD_IS_SHARED if arg_values.len() == 1 => Some(Dynamic::FALSE),
_ => state.call_fn_with_constant_arguments(&x.name, arg_values)
};
if let Some(result) = result {
state.set_dirty();
*expr = Expr::from_dynamic(result, *pos);
return;
}
}
x.args.iter_mut().for_each(|a| optimize_expr(a, state, false));
}
// id(args ..) -> optimize function call arguments
Expr::FnCall(x, _) => for arg in x.args.iter_mut() {
optimize_expr(arg, state, false);
// Move constant arguments
if let Some(value) = arg.get_literal_value() {
state.set_dirty();
x.constants.push(value);
*arg = Expr::Stack(x.constants.len()-1, arg.position());
}
},
// constant-name
Expr::Variable(_, pos, x) if x.1.is_none() && state.find_constant(&x.2).is_some() => {
// Replace constant with value
*expr = Expr::from_dynamic(state.find_constant(&x.2).expect("exists").clone(), *pos);
state.set_dirty();
}
// Custom syntax
Expr::Custom(x, _) => {
if x.scope_may_be_changed {
state.propagate_constants = false;
}
x.inputs.iter_mut().for_each(|expr| optimize_expr(expr, state, false));
}
// All other expressions - skip
_ => (),
}
}
/// Optimize a block of [statements][Stmt] at top level.
///
/// Constants and variables from the scope are added.
fn optimize_top_level(
statements: StaticVec<Stmt>,
engine: &Engine,
scope: &Scope,
lib: &[&Module],
optimization_level: OptimizationLevel,
) -> StaticVec<Stmt> {
let mut statements = statements;
// If optimization level is None then skip optimizing
if optimization_level == OptimizationLevel::None {
statements.shrink_to_fit();
return statements;
}
// Set up the state
let mut state = OptimizerState::new(engine, lib, optimization_level);
// Add constants and variables from the scope
scope.iter().for_each(|(name, constant, value)| {
if !constant {
state.push_var(name, AccessMode::ReadWrite, None);
} else {
state.push_var(name, AccessMode::ReadOnly, Some(value));
}
});
statements = optimize_stmt_block(statements, &mut state, true, false, true);
statements
}
/// Optimize an [`AST`].
pub fn optimize_into_ast(
engine: &Engine,
scope: &Scope,
statements: StaticVec<Stmt>,
functions: StaticVec<Shared<ScriptFnDef>>,
optimization_level: OptimizationLevel,
) -> AST {
let level = if cfg!(feature = "no_optimize") {
OptimizationLevel::default()
} else {
optimization_level
};
let mut statements = statements;
let _functions = functions;
#[cfg(not(feature = "no_function"))]
let lib = {
let mut module = Module::new();
if level != OptimizationLevel::None {
// We only need the script library's signatures for optimization purposes
let mut lib2 = Module::new();
_functions
.iter()
.map(|fn_def| ScriptFnDef {
name: fn_def.name.clone(),
access: fn_def.access,
body: crate::ast::StmtBlock::NONE,
params: fn_def.params.clone(),
lib: None,
#[cfg(not(feature = "no_module"))]
mods: Imports::new(),
#[cfg(not(feature = "no_function"))]
#[cfg(feature = "metadata")]
comments: None,
})
.for_each(|fn_def| {
lib2.set_script_fn(fn_def);
});
let lib2 = &[&lib2];
_functions
.into_iter()
.map(|fn_def| {
let mut fn_def = crate::func::native::shared_take_or_clone(fn_def);
// Optimize the function body
let body = mem::take(fn_def.body.deref_mut());
*fn_def.body = optimize_top_level(body, engine, scope, lib2, level);
fn_def
})
.for_each(|fn_def| {
module.set_script_fn(fn_def);
});
} else {
_functions.into_iter().for_each(|fn_def| {
module.set_script_fn(fn_def);
});
}
module
};
#[cfg(feature = "no_function")]
let lib = Module::new();
statements.shrink_to_fit();
AST::new(
match level {
OptimizationLevel::None => statements,
OptimizationLevel::Simple | OptimizationLevel::Full => {
optimize_top_level(statements, engine, &scope, &[&lib], level)
}
},
lib,
)
}