rhai/src/optimizer.rs

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//! Module implementing the [`AST`] optimizer.
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#![cfg(not(feature = "no_optimize"))]
use crate::ast::{Expr, OpAssignment, Stmt, AST_OPTION_FLAGS::*};
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use crate::engine::{KEYWORD_DEBUG, KEYWORD_EVAL, KEYWORD_FN_PTR, KEYWORD_PRINT, KEYWORD_TYPE_OF};
use crate::eval::{EvalState, GlobalRuntimeState};
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use crate::func::builtin::get_builtin_binary_op_fn;
use crate::func::hashing::get_hasher;
use crate::tokenizer::Token;
use crate::types::dynamic::AccessMode;
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use crate::{
calc_fn_hash, calc_fn_params_hash, combine_hashes, Dynamic, Engine, FnPtr, Position, Scope,
StaticVec, AST, INT,
};
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#[cfg(feature = "no_std")]
use std::prelude::v1::*;
use std::{
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any::TypeId,
convert::TryFrom,
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hash::{Hash, Hasher},
mem,
};
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/// Level of optimization performed.
#[derive(Debug, Eq, PartialEq, Hash, Clone, Copy)]
pub enum OptimizationLevel {
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/// No optimization performed.
None,
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/// Only perform simple optimizations without evaluating functions.
Simple,
/// Full optimizations performed, including evaluating functions.
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/// Take care that this may cause side effects as it essentially assumes that all functions are pure.
Full,
}
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impl Default for OptimizationLevel {
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#[inline(always)]
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fn default() -> Self {
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Self::Simple
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}
}
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/// Mutable state throughout an optimization pass.
#[derive(Debug, Clone)]
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struct OptimizerState<'a> {
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/// Has the [`AST`] been changed during this pass?
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changed: bool,
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/// Collection of constants to use for eager function evaluations.
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variables: StaticVec<(String, AccessMode, Option<Dynamic>)>,
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/// Activate constants propagation?
propagate_constants: bool,
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/// An [`Engine`] instance for eager function evaluation.
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engine: &'a Engine,
/// [Module][crate::Module] containing script-defined functions.
#[cfg(not(feature = "no_function"))]
lib: &'a [&'a crate::Module],
/// Optimization level.
optimization_level: OptimizationLevel,
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}
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impl<'a> OptimizerState<'a> {
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/// Create a new State.
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#[inline(always)]
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pub const fn new(
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engine: &'a Engine,
#[cfg(not(feature = "no_function"))] lib: &'a [&'a crate::Module],
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optimization_level: OptimizationLevel,
) -> Self {
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Self {
changed: false,
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variables: StaticVec::new_const(),
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propagate_constants: true,
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engine,
#[cfg(not(feature = "no_function"))]
lib,
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optimization_level,
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}
}
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/// Set the [`AST`] state to be dirty (i.e. changed).
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#[inline(always)]
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pub fn set_dirty(&mut self) {
self.changed = true;
}
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/// Set the [`AST`] state to be not dirty (i.e. unchanged).
#[inline(always)]
pub fn clear_dirty(&mut self) {
self.changed = false;
}
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/// Is the [`AST`] dirty (i.e. changed)?
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#[inline(always)]
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pub const fn is_dirty(&self) -> bool {
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self.changed
}
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/// Prune the list of constants back to a specified size.
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#[inline(always)]
pub fn restore_var(&mut self, len: usize) {
self.variables.truncate(len)
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}
/// Add a new variable to the list.
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#[inline(always)]
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pub fn push_var(
&mut self,
name: impl Into<String>,
access: AccessMode,
value: Option<Dynamic>,
) {
self.variables.push((name.into(), access, value))
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}
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/// Look up a constant from the list.
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#[inline]
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pub fn find_constant(&self, name: &str) -> Option<&Dynamic> {
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if !self.propagate_constants {
return None;
}
for (n, access, value) in self.variables.iter().rev() {
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if n == name {
return match access {
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AccessMode::ReadWrite => None,
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AccessMode::ReadOnly => value.as_ref(),
};
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}
}
None
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}
/// Call a registered function
#[inline]
pub fn call_fn_with_constant_arguments(
&self,
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fn_name: &str,
arg_values: &mut [Dynamic],
) -> Option<Dynamic> {
#[cfg(not(feature = "no_function"))]
let lib = self.lib;
#[cfg(feature = "no_function")]
let lib = &[];
self.engine
.call_native_fn(
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&mut GlobalRuntimeState::new(),
&mut EvalState::new(),
lib,
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fn_name,
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calc_fn_hash(&fn_name, arg_values.len()),
&mut arg_values.iter_mut().collect::<StaticVec<_>>(),
false,
false,
Position::NONE,
)
.ok()
.map(|(v, _)| v)
}
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}
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// Has a system function a Rust-native override?
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fn has_native_fn_override(
engine: &Engine,
hash_script: u64,
arg_types: impl AsRef<[TypeId]>,
) -> bool {
let hash_params = calc_fn_params_hash(arg_types.as_ref().iter().cloned());
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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.
engine.global_modules.iter().filter(|m| !m.standard).any(|m| m.contains_fn(hash))
// Then check sub-modules
|| engine.global_sub_modules.values().any(|m| m.contains_qualified_fn(hash))
}
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/// Optimize a block of [statements][Stmt].
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fn optimize_stmt_block(
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mut statements: StaticVec<Stmt>,
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state: &mut OptimizerState,
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preserve_result: bool,
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is_internal: bool,
reduce_return: bool,
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) -> StaticVec<Stmt> {
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if statements.is_empty() {
return statements;
}
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let mut is_dirty = state.is_dirty();
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let is_pure = if is_internal {
Stmt::is_internally_pure
} else {
Stmt::is_pure
};
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// Flatten blocks
loop {
if let Some(n) = statements.iter().enumerate().find_map(|(i, s)| match s {
Stmt::Block(block, _) if !block.iter().any(Stmt::is_block_dependent) => Some(i),
_ => None,
}) {
let (first, second) = statements.split_at_mut(n);
let stmt = mem::take(&mut second[0]);
let mut stmts = match stmt {
Stmt::Block(block, _) => block,
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stmt => unreachable!("Stmt::Block expected but gets {:?}", stmt),
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};
statements = first
.iter_mut()
.map(mem::take)
.chain(stmts.iter_mut().map(mem::take))
.chain(second.iter_mut().skip(1).map(mem::take))
.collect();
} else {
break;
}
is_dirty = true;
}
// Optimize
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loop {
state.clear_dirty();
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let orig_constants_len = state.variables.len(); // Original number of constants in the state, for restore later
let orig_propagate_constants = state.propagate_constants;
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// Remove everything following control flow breaking statements
let mut dead_code = false;
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statements.retain(|stmt| {
if dead_code {
state.set_dirty();
false
} else if stmt.is_control_flow_break() {
dead_code = true;
true
} else {
true
}
});
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// 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(
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x.name.as_str(),
AccessMode::ReadOnly,
value_expr.get_literal_value(),
);
}
} else {
// Add variables into the state
optimize_expr(value_expr, state, false);
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state.push_var(x.name.as_str(), AccessMode::ReadWrite, None);
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}
}
// Optimize the statement
_ => optimize_stmt(stmt, state, preserve_result),
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}
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});
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// 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),
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#[cfg(not(feature = "no_module"))]
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Stmt::Import(e, _, _) if !e.is_constant() => Some(i),
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_ => None,
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})
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.map_or(0, |n| statements.len() - n - 1);
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while index < statements.len() {
if preserve_result && index >= statements.len() - 1 {
break;
} else {
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match statements[index] {
ref stmt if is_pure(stmt) && index >= first_non_constant => {
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state.set_dirty();
statements.remove(index);
}
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ref stmt if stmt.is_pure() => {
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state.set_dirty();
if index < first_non_constant {
first_non_constant -= 1;
}
statements.remove(index);
}
_ => index += 1,
}
}
}
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// 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 {
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match statements[..] {
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// { return; } -> {}
[Stmt::Return(options, None, _)]
if reduce_return && !options.contains(AST_OPTION_BREAK_OUT) =>
{
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state.set_dirty();
statements.clear();
}
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[ref stmt] if !stmt.returns_value() && is_pure(stmt) => {
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state.set_dirty();
statements.clear();
}
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// { ...; return; } -> { ... }
[.., ref last_stmt, Stmt::Return(options, None, _)]
if reduce_return
&& !options.contains(AST_OPTION_BREAK_OUT)
&& !last_stmt.returns_value() =>
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{
state.set_dirty();
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statements.pop().unwrap();
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}
// { ...; return val; } -> { ...; val }
[.., Stmt::Return(options, ref mut expr, pos)]
if reduce_return && !options.contains(AST_OPTION_BREAK_OUT) =>
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{
state.set_dirty();
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*statements.last_mut().unwrap() = expr
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.as_mut()
.map_or_else(|| Stmt::Noop(pos), |e| Stmt::Expr(mem::take(e)));
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}
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// { ...; stmt; noop } -> done
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[.., ref second_last_stmt, Stmt::Noop(_)]
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if second_last_stmt.returns_value() =>
{
break
}
// { ...; stmt_that_returns; pure_non_value_stmt } -> { ...; stmt_that_returns; noop }
// { ...; stmt; pure_non_value_stmt } -> { ...; stmt }
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[.., ref second_last_stmt, ref last_stmt]
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if !last_stmt.returns_value() && is_pure(last_stmt) =>
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{
state.set_dirty();
if second_last_stmt.returns_value() {
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*statements.last_mut().unwrap() = Stmt::Noop(last_stmt.position());
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} else {
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statements.pop().unwrap();
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}
}
_ => break,
}
}
} else {
loop {
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match statements[..] {
[ref stmt] if is_pure(stmt) => {
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state.set_dirty();
statements.clear();
}
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// { ...; return; } -> { ... }
[.., Stmt::Return(options, None, _)]
if reduce_return && !options.contains(AST_OPTION_BREAK_OUT) =>
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{
state.set_dirty();
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statements.pop().unwrap();
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}
// { ...; return pure_val; } -> { ... }
[.., Stmt::Return(options, Some(ref expr), _)]
if reduce_return
&& !options.contains(AST_OPTION_BREAK_OUT)
&& expr.is_pure() =>
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{
state.set_dirty();
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statements.pop().unwrap();
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}
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[.., ref last_stmt] if is_pure(last_stmt) => {
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state.set_dirty();
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statements.pop().unwrap();
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}
_ => break,
}
}
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}
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// Pop the stack and remove all the local constants
state.restore_var(orig_constants_len);
state.propagate_constants = orig_propagate_constants;
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if !state.is_dirty() {
break;
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}
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is_dirty = true;
}
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if is_dirty {
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state.set_dirty();
}
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statements.shrink_to_fit();
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statements
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}
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/// Optimize a [statement][Stmt].
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fn optimize_stmt(stmt: &mut Stmt, state: &mut OptimizerState, preserve_result: bool) {
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match stmt {
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// 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, _)
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if Token::lookup_from_syntax(&x2.name).map(|t| t.has_op_assignment()).unwrap_or(false)
&& x2.args.len() == 2
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&& x2.args[0].get_variable_name(true) == x.0.get_variable_name(true)
) =>
{
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match x.2 {
Expr::FnCall(ref mut x2, _) => {
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state.set_dirty();
x.1 = Some(OpAssignment::new_from_base(&x2.name));
let value = mem::take(&mut x2.args[1]);
if let Expr::Stack(slot, pos) = value {
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x.2 =
Expr::from_dynamic(mem::take(x2.constants.get_mut(slot).unwrap()), pos);
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} else {
x.2 = value;
}
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}
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ref expr => unreachable!("Expr::FnCall expected but gets {:?}", expr),
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}
}
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// expr op= expr
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Stmt::Assignment(x, _) => match x.0 {
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Expr::Variable(_, _, _) => optimize_expr(&mut x.2, state, false),
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_ => {
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optimize_expr(&mut x.0, state, false);
optimize_expr(&mut x.2, state, false);
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}
},
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// if expr {}
Stmt::If(condition, x, _) if x.0.is_empty() && x.1.is_empty() => {
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state.set_dirty();
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let pos = condition.position();
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let mut expr = mem::take(condition);
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optimize_expr(&mut expr, state, false);
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*stmt = if preserve_result {
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// -> { expr, Noop }
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Stmt::Block([Stmt::Expr(expr), Stmt::Noop(pos)].into(), pos)
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} else {
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// -> expr
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Stmt::Expr(expr)
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};
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}
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// if false { if_block } -> Noop
Stmt::If(Expr::BoolConstant(false, pos), x, _) if x.1.is_empty() => {
state.set_dirty();
*stmt = Stmt::Noop(*pos);
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}
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// if false { if_block } else { else_block } -> else_block
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Stmt::If(Expr::BoolConstant(false, _), x, _) => {
state.set_dirty();
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*stmt =
match optimize_stmt_block(mem::take(&mut *x.1), 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()),
}
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}
// if true { if_block } else { else_block } -> if_block
Stmt::If(Expr::BoolConstant(true, _), x, _) => {
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state.set_dirty();
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*stmt =
match optimize_stmt_block(mem::take(&mut *x.0), 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()),
}
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}
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// if expr { if_block } else { else_block }
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Stmt::If(condition, x, _) => {
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optimize_expr(condition, state, false);
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*x.0 = optimize_stmt_block(mem::take(&mut *x.0), state, preserve_result, true, false);
*x.1 = optimize_stmt_block(mem::take(&mut *x.1), state, preserve_result, true, false);
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}
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// switch const { ... }
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Stmt::Switch(match_expr, x, pos) if match_expr.is_constant() => {
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let value = match_expr.get_literal_value().unwrap();
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let hasher = &mut get_hasher();
value.hash(hasher);
let hash = hasher.finish();
let table = &mut x.0;
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// First check hashes
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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 }
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optimize_expr(&mut condition, state, false);
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let def_stmt =
optimize_stmt_block(mem::take(&mut *x.1), state, true, true, false);
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*stmt = Stmt::If(
condition,
Box::new((
mem::take(&mut block.1),
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Stmt::Block(def_stmt.into_boxed_slice(), x.1.position().or_else(*pos))
.into(),
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)),
match_expr.position(),
);
} else {
// Promote the matched case
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let statements =
optimize_stmt_block(mem::take(&mut *block.1), state, true, true, false);
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*stmt = Stmt::Block(statements.into_boxed_slice(), block.1.position());
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}
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state.set_dirty();
return;
}
// Then check ranges
let ranges = &mut x.2;
if value.is::<INT>() && !ranges.is_empty() {
let value = value.as_int().expect("`INT`");
// Only one range or all ranges without conditions
if ranges.len() == 1 || ranges.iter().all(|(_, _, _, c, _)| c.is_none()) {
for (_, _, _, condition, stmt_block) in
ranges
.iter_mut()
.filter(|&&mut (start, end, inclusive, _, _)| {
(!inclusive && (start..end).contains(&value))
|| (inclusive && (start..=end).contains(&value))
})
{
if let Some(mut condition) = mem::take(condition) {
// switch const { range if condition => stmt, _ => def } => if condition { stmt } else { def }
optimize_expr(&mut condition, state, false);
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let def_stmt =
optimize_stmt_block(mem::take(&mut *x.1), state, true, true, false);
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*stmt = Stmt::If(
condition,
Box::new((
mem::take(stmt_block),
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Stmt::Block(
def_stmt.into_boxed_slice(),
x.1.position().or_else(*pos),
)
.into(),
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)),
match_expr.position(),
);
} else {
// Promote the matched case
let statements = mem::take(&mut **stmt_block);
let statements =
optimize_stmt_block(statements, state, true, true, false);
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*stmt =
Stmt::Block(statements.into_boxed_slice(), stmt_block.position());
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}
state.set_dirty();
return;
}
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} else {
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// Multiple ranges - clear the table and just keep the right ranges
if !table.is_empty() {
state.set_dirty();
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table.clear();
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}
let old_ranges_len = ranges.len();
ranges.retain(|&mut (start, end, inclusive, _, _)| {
(!inclusive && (start..end).contains(&value))
|| (inclusive && (start..=end).contains(&value))
});
if ranges.len() != old_ranges_len {
state.set_dirty();
}
for (_, _, _, condition, stmt_block) in ranges.iter_mut() {
let statements = mem::take(&mut **stmt_block);
**stmt_block =
optimize_stmt_block(statements, state, preserve_result, true, false);
if let Some(mut c) = mem::take(condition) {
optimize_expr(&mut c, state, false);
match c {
Expr::Unit(_) | Expr::BoolConstant(true, _) => state.set_dirty(),
_ => *condition = Some(c),
}
}
}
return;
}
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}
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// Promote the default case
state.set_dirty();
let def_stmt = optimize_stmt_block(mem::take(&mut *x.1), state, true, true, false);
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*stmt = Stmt::Block(def_stmt.into_boxed_slice(), x.1.position().or_else(*pos));
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}
// switch
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Stmt::Switch(match_expr, x, _) => {
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optimize_expr(match_expr, state, false);
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x.0.values_mut().for_each(|block| {
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let statements = mem::take(&mut *block.1);
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*block.1 = optimize_stmt_block(statements, state, preserve_result, true, false);
if let Some(mut condition) = mem::take(&mut block.0) {
optimize_expr(&mut condition, state, false);
match condition {
Expr::Unit(_) | Expr::BoolConstant(true, _) => state.set_dirty(),
_ => block.0 = Some(condition),
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}
}
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});
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// 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);
}
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*x.1 = optimize_stmt_block(mem::take(&mut *x.1), state, preserve_result, true, false);
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}
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// while false { block } -> Noop
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Stmt::While(Expr::BoolConstant(false, pos), _, _) => {
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state.set_dirty();
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*stmt = Stmt::Noop(*pos)
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}
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// while expr { block }
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Stmt::While(condition, body, _) => {
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optimize_expr(condition, state, false);
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if let Expr::BoolConstant(true, pos) = condition {
*condition = Expr::Unit(*pos);
}
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***body = optimize_stmt_block(mem::take(&mut **body), state, false, true, false);
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if body.len() == 1 {
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match body[0] {
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// while expr { break; } -> { expr; }
Stmt::BreakLoop(options, pos) if options.contains(AST_OPTION_BREAK_OUT) => {
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// 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))
}
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*stmt = Stmt::Block(statements.into_boxed_slice(), pos);
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} else {
*stmt = Stmt::Noop(pos);
};
}
_ => (),
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}
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}
}
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// do { block } while false | do { block } until true -> { block }
Stmt::Do(body, Expr::BoolConstant(x, _), options, _)
if *x == options.contains(AST_OPTION_NEGATED) =>
{
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state.set_dirty();
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*stmt = Stmt::Block(
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optimize_stmt_block(mem::take(&mut **body), state, false, true, false)
.into_boxed_slice(),
body.position(),
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);
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}
// do { block } while|until expr
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Stmt::Do(body, condition, _, _) => {
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optimize_expr(condition, state, false);
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***body = optimize_stmt_block(mem::take(&mut **body), state, false, true, false);
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}
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// for id in expr { block }
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Stmt::For(iterable, x, _) => {
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optimize_expr(iterable, state, false);
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*x.2 = optimize_stmt_block(mem::take(&mut *x.2), state, false, true, false);
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}
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// let id = expr;
Stmt::Var(expr, _, options, _) if !options.contains(AST_OPTION_CONSTANT) => {
optimize_expr(expr, state, false)
}
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// import expr as var;
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#[cfg(not(feature = "no_module"))]
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Stmt::Import(expr, _, _) => optimize_expr(expr, state, false),
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// { block }
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Stmt::Block(statements, pos) => {
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let statements = mem::take(statements).into_vec().into();
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let mut block = optimize_stmt_block(statements, state, preserve_result, true, false);
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match block.as_mut_slice() {
[] => {
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state.set_dirty();
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*stmt = Stmt::Noop(*pos);
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}
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// Only one statement which is not block-dependent - promote
[s] if !s.is_block_dependent() => {
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state.set_dirty();
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*stmt = mem::take(s);
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}
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_ => *stmt = Stmt::Block(block.into_boxed_slice(), *pos),
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}
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}
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// try { pure try_block } catch ( var ) { catch_block } -> try_block
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Stmt::TryCatch(x, _) if x.0.iter().all(Stmt::is_pure) => {
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// If try block is pure, there will never be any exceptions
state.set_dirty();
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*stmt = Stmt::Block(
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optimize_stmt_block(mem::take(&mut *x.0), state, false, true, false)
.into_boxed_slice(),
x.0.position(),
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);
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}
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// try { try_block } catch ( var ) { catch_block }
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Stmt::TryCatch(x, _) => {
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*x.0 = optimize_stmt_block(mem::take(&mut *x.0), state, false, true, false);
*x.2 = optimize_stmt_block(mem::take(&mut *x.2), state, false, true, false);
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}
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// func(...)
Stmt::Expr(expr @ Expr::FnCall(_, _)) => {
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optimize_expr(expr, state, false);
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match expr {
Expr::FnCall(x, pos) => {
state.set_dirty();
*stmt = Stmt::FnCall(mem::take(x), *pos);
}
_ => (),
}
}
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// {}
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Stmt::Expr(Expr::Stmt(x)) if x.is_empty() => {
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state.set_dirty();
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*stmt = Stmt::Noop(x.position());
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}
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// {...};
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Stmt::Expr(Expr::Stmt(x)) => {
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state.set_dirty();
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*stmt = mem::take(&mut **x).into();
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}
// expr;
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Stmt::Expr(expr) => optimize_expr(expr, state, false),
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// return expr;
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Stmt::Return(_, Some(ref mut expr), _) => optimize_expr(expr, state, false),
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// All other statements - skip
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_ => (),
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}
}
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/// Optimize an [expression][Expr].
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fn optimize_expr(expr: &mut Expr, state: &mut OptimizerState, chaining: bool) {
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// These keywords are handled specially
const DONT_EVAL_KEYWORDS: &[&str] = &[
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KEYWORD_PRINT, // side effects
KEYWORD_DEBUG, // side effects
KEYWORD_EVAL, // arbitrary scripts
];
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let _chaining = chaining;
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match expr {
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// {}
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Expr::Stmt(x) if x.is_empty() => { state.set_dirty(); *expr = Expr::Unit(x.position()) }
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// { stmt; ... } - do not count promotion as dirty because it gets turned back into an array
Expr::Stmt(x) => {
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***x = optimize_stmt_block(mem::take(&mut **x), state, true, true, false);
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// { Stmt(Expr) } - promote
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match x.as_mut().as_mut() {
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[ Stmt::Expr(e) ] => { state.set_dirty(); *expr = mem::take(e); }
_ => ()
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}
}
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// lhs.rhs
#[cfg(not(feature = "no_object"))]
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Expr::Dot(x,_, _) if !_chaining => match (&mut x.lhs, &mut x.rhs) {
// map.string
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(Expr::Map(m, pos), Expr::Property(p)) if m.0.iter().all(|(_, x)| x.is_pure()) => {
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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();
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*expr = mem::take(&mut m.0).into_iter().find(|(x, _)| x.name == prop)
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.map(|(_, mut expr)| { expr.set_position(*pos); expr })
.unwrap_or_else(|| Expr::Unit(*pos));
}
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// var.rhs
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(Expr::Variable(_, _, _), rhs) => optimize_expr(rhs, state, true),
// lhs.rhs
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(lhs, rhs) => { optimize_expr(lhs, state, false); optimize_expr(rhs, state, true); }
}
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// ....lhs.rhs
#[cfg(not(feature = "no_object"))]
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Expr::Dot(x,_, _) => { optimize_expr(&mut x.lhs, state, false); optimize_expr(&mut x.rhs, state, _chaining); }
2020-03-11 04:03:18 +01:00
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// lhs[rhs]
#[cfg(not(feature = "no_index"))]
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Expr::Index(x, _, _) if !_chaining => match (&mut x.lhs, &mut x.rhs) {
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// array[int]
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(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.
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// All other items can be thrown away.
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state.set_dirty();
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let mut result = mem::take(&mut a[*i as usize]);
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result.set_position(*pos);
*expr = result;
}
// array[-int]
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(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();
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let index = a.len() - i.abs() as usize;
let mut result = mem::take(&mut a[index]);
result.set_position(*pos);
*expr = result;
}
// map[string]
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(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();
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*expr = mem::take(&mut m.0).into_iter().find(|(x, _)| x.name.as_str() == s.as_str())
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.map(|(_, mut expr)| { expr.set_position(*pos); expr })
.unwrap_or_else(|| Expr::Unit(*pos));
}
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// 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);
}
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// string[int]
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(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();
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*expr = Expr::CharConstant(s.chars().nth(*i as usize).unwrap(), *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();
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*expr = Expr::CharConstant(s.chars().rev().nth(i.abs() as usize - 1).unwrap(), *pos);
}
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// var[rhs]
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(Expr::Variable(_, _, _), rhs) => optimize_expr(rhs, state, true),
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// lhs[rhs]
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(lhs, rhs) => { optimize_expr(lhs, state, false); optimize_expr(rhs, state, true); }
},
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// ...[lhs][rhs]
#[cfg(not(feature = "no_index"))]
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Expr::Index(x, _, _) => { optimize_expr(&mut x.lhs, state, false); optimize_expr(&mut x.rhs, state, _chaining); }
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// ``
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Expr::InterpolatedString(x, pos) if x.is_empty() => {
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state.set_dirty();
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*expr = Expr::StringConstant(state.engine.const_empty_string(), *pos);
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}
// `...`
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Expr::InterpolatedString(x, _) if x.len() == 1 && matches!(x[0], Expr::StringConstant(_, _)) => {
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state.set_dirty();
*expr = mem::take(&mut x[0]);
}
// `... ${ ... } ...`
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Expr::InterpolatedString(x, _) => {
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x.iter_mut().for_each(|expr| optimize_expr(expr, state, false));
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let mut n = 0;
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// Merge consecutive strings
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while n < x.len() - 1 {
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match (mem::take(&mut x[n]), mem::take(&mut x[n+1])) {
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(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; }
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}
}
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x.shrink_to_fit();
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}
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// [ constant .. ]
#[cfg(not(feature = "no_index"))]
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Expr::Array(_, _) if expr.is_constant() => {
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state.set_dirty();
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*expr = Expr::DynamicConstant(expr.get_literal_value().unwrap().into(), expr.position());
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}
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// [ items .. ]
#[cfg(not(feature = "no_index"))]
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Expr::Array(x, _) => x.iter_mut().for_each(|expr| optimize_expr(expr, state, false)),
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// #{ key:constant, .. }
#[cfg(not(feature = "no_object"))]
Expr::Map(_, _) if expr.is_constant() => {
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state.set_dirty();
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*expr = Expr::DynamicConstant(expr.get_literal_value().unwrap().into(), expr.position());
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}
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// #{ key:value, .. }
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#[cfg(not(feature = "no_object"))]
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Expr::Map(x, _) => x.0.iter_mut().for_each(|(_, expr)| optimize_expr(expr, state, false)),
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// lhs && rhs
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Expr::And(x, _) => match (&mut x.lhs, &mut x.rhs) {
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// true && rhs -> rhs
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(Expr::BoolConstant(true, _), rhs) => { state.set_dirty(); optimize_expr(rhs, state, false); *expr = mem::take(rhs); }
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// false && rhs -> false
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(Expr::BoolConstant(false, pos), _) => { state.set_dirty(); *expr = Expr::BoolConstant(false, *pos); }
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// lhs && true -> lhs
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(lhs, Expr::BoolConstant(true, _)) => { state.set_dirty(); optimize_expr(lhs, state, false); *expr = mem::take(lhs); }
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// lhs && rhs
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(lhs, rhs) => { optimize_expr(lhs, state, false); optimize_expr(rhs, state, false); }
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},
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// lhs || rhs
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Expr::Or(ref mut x, _) => match (&mut x.lhs, &mut x.rhs) {
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// false || rhs -> rhs
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(Expr::BoolConstant(false, _), rhs) => { state.set_dirty(); optimize_expr(rhs, state, false); *expr = mem::take(rhs); }
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// true || rhs -> true
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(Expr::BoolConstant(true, pos), _) => { state.set_dirty(); *expr = Expr::BoolConstant(true, *pos); }
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// lhs || false
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(lhs, Expr::BoolConstant(false, _)) => { state.set_dirty(); optimize_expr(lhs, state, false); *expr = mem::take(lhs); }
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// lhs || rhs
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(lhs, rhs) => { optimize_expr(lhs, state, false); optimize_expr(rhs, state, false); }
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},
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// eval!
Expr::FnCall(x, _) if x.name == KEYWORD_EVAL => {
state.propagate_constants = false;
}
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// Fn
Expr::FnCall(x, pos)
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if !x.is_qualified() // Non-qualified
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&& state.optimization_level == OptimizationLevel::Simple // simple optimizations
&& x.args.len() == 1
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&& x.name == KEYWORD_FN_PTR
&& x.args[0].is_constant()
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=> {
let fn_name = match x.args[0] {
Expr::Stack(slot, _) => x.constants[slot].clone(),
Expr::StringConstant(ref s, _) => s.clone().into(),
_ => Dynamic::UNIT
};
if let Ok(fn_ptr) = fn_name.into_immutable_string().map_err(|err| err.into()).and_then(FnPtr::try_from) {
state.set_dirty();
*expr = Expr::DynamicConstant(Box::new(fn_ptr.into()), *pos);
} else {
optimize_expr(&mut x.args[0], state, false);
}
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}
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// Do not call some special keywords
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Expr::FnCall(x, _) if DONT_EVAL_KEYWORDS.contains(&x.name.as_ref()) => {
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x.args.iter_mut().for_each(|a| optimize_expr(a, state, false));
}
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// Call built-in operators
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Expr::FnCall(x, pos)
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if !x.is_qualified() // Non-qualified
&& state.optimization_level == OptimizationLevel::Simple // simple optimizations
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&& 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(),
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_ => e.get_literal_value().unwrap()
}).collect::<StaticVec<_>>();
let arg_types: StaticVec<_> = arg_values.iter().map(Dynamic::type_id).collect();
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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;
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}
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#[cfg(not(feature = "no_closure"))]
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crate::engine::KEYWORD_IS_SHARED if arg_values.len() == 1 => {
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state.set_dirty();
*expr = Expr::from_dynamic(Dynamic::FALSE, *pos);
return;
}
// Overloaded operators can override built-in.
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_ if x.args.len() == 2 && !has_native_fn_override(state.engine, x.hashes.native, arg_types.as_ref()) => {
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if let Some(result) = get_builtin_binary_op_fn(x.name.as_ref(), &arg_values[0], &arg_values[1])
.and_then(|f| {
#[cfg(not(feature = "no_function"))]
let lib = state.lib;
#[cfg(feature = "no_function")]
let lib = &[];
let context = (state.engine, x.name.as_str(), lib).into();
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let (first, second) = arg_values.split_first_mut().unwrap();
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(f)(context, &mut [ first, &mut second[0] ]).ok()
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}) {
state.set_dirty();
*expr = Expr::from_dynamic(result, *pos);
return;
}
}
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_ => ()
}
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x.args.iter_mut().for_each(|a| optimize_expr(a, state, false));
// Move constant arguments
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let constants = &mut x.constants;
x.args.iter_mut().for_each(|arg| {
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if let Some(value) = arg.get_literal_value() {
state.set_dirty();
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constants.push(value);
*arg = Expr::Stack(constants.len()-1, arg.position());
}
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});
}
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// Eagerly call functions
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Expr::FnCall(x, pos)
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if !x.is_qualified() // Non-qualified
&& state.optimization_level == OptimizationLevel::Full // full optimizations
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&& x.args.iter().all(Expr::is_constant) // all arguments are constants
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=> {
// First search for script-defined functions (can override built-in)
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#[cfg(not(feature = "no_function"))]
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let has_script_fn = state.lib.iter().any(|&m| m.get_script_fn(&x.name, x.args.len()).is_some());
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#[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(),
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_ => e.get_literal_value().unwrap()
}).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()),
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#[cfg(not(feature = "no_closure"))]
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crate::engine::KEYWORD_IS_SHARED if arg_values.len() == 1 => Some(Dynamic::FALSE),
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_ => state.call_fn_with_constant_arguments(&x.name, arg_values)
};
if let Some(result) = result {
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state.set_dirty();
*expr = Expr::from_dynamic(result, *pos);
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return;
}
}
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x.args.iter_mut().for_each(|a| optimize_expr(a, state, false));
}
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// id(args ..) -> optimize function call arguments
Expr::FnCall(x, _) => for arg in x.args.iter_mut() {
optimize_expr(arg, state, false);
// Move constant arguments
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if let Some(value) = arg.get_literal_value() {
state.set_dirty();
x.constants.push(value);
*arg = Expr::Stack(x.constants.len()-1, arg.position());
}
},
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// constant-name
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Expr::Variable(_, pos, x) if x.1.is_none() && state.find_constant(&x.2).is_some() => {
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// Replace constant with value
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*expr = Expr::from_dynamic(state.find_constant(&x.2).unwrap().clone(), *pos);
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state.set_dirty();
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}
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// Custom syntax
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Expr::Custom(x, _) => {
if x.scope_may_be_changed {
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state.propagate_constants = false;
}
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x.inputs.iter_mut().for_each(|expr| optimize_expr(expr, state, false));
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}
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// All other expressions - skip
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_ => (),
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}
}
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/// Optimize a block of [statements][Stmt] at top level.
///
/// Constants and variables from the scope are added.
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fn optimize_top_level(
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statements: StaticVec<Stmt>,
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engine: &Engine,
scope: &Scope,
#[cfg(not(feature = "no_function"))] lib: &[&crate::Module],
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optimization_level: OptimizationLevel,
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) -> StaticVec<Stmt> {
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let mut statements = statements;
// If optimization level is None then skip optimizing
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if optimization_level == OptimizationLevel::None {
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statements.shrink_to_fit();
return statements;
}
// Set up the state
let mut state = OptimizerState::new(
engine,
#[cfg(not(feature = "no_function"))]
lib,
optimization_level,
);
// Add constants and variables from the scope
scope.iter().for_each(|(name, constant, value)| {
if !constant {
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state.push_var(name, AccessMode::ReadWrite, None);
} else {
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state.push_var(name, AccessMode::ReadOnly, Some(value));
}
});
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statements = optimize_stmt_block(statements, &mut state, true, false, true);
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statements
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}
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/// Optimize an [`AST`].
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pub fn optimize_into_ast(
engine: &Engine,
scope: &Scope,
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statements: StaticVec<Stmt>,
#[cfg(not(feature = "no_function"))] functions: StaticVec<
crate::Shared<crate::ast::ScriptFnDef>,
>,
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optimization_level: OptimizationLevel,
) -> AST {
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let mut statements = statements;
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#[cfg(not(feature = "no_function"))]
let lib = {
let mut module = crate::Module::new();
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if optimization_level != OptimizationLevel::None {
// We only need the script library's signatures for optimization purposes
let mut lib2 = crate::Module::new();
functions
.iter()
.map(|fn_def| crate::ast::ScriptFnDef {
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name: fn_def.name.clone(),
access: fn_def.access,
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body: crate::ast::StmtBlock::NONE,
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params: fn_def.params.clone(),
lib: None,
#[cfg(not(feature = "no_module"))]
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global: None,
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#[cfg(not(feature = "no_function"))]
#[cfg(feature = "metadata")]
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comments: None,
})
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.for_each(|fn_def| {
lib2.set_script_fn(fn_def);
});
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let lib2 = &[&lib2];
functions
.into_iter()
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.map(|fn_def| {
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let mut fn_def = crate::func::native::shared_take_or_clone(fn_def);
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// Optimize the function body
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let body = mem::take(&mut *fn_def.body);
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*fn_def.body =
optimize_top_level(body, engine, scope, lib2, optimization_level);
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fn_def
})
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.for_each(|fn_def| {
module.set_script_fn(fn_def);
});
} else {
functions.into_iter().for_each(|fn_def| {
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module.set_script_fn(fn_def);
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});
}
module
};
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statements.shrink_to_fit();
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AST::new(
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match optimization_level {
OptimizationLevel::None => statements,
OptimizationLevel::Simple | OptimizationLevel::Full => optimize_top_level(
statements,
engine,
&scope,
#[cfg(not(feature = "no_function"))]
&[&lib],
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optimization_level,
),
},
#[cfg(not(feature = "no_function"))]
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lib,
)
}