2020-03-09 14:57:07 +01:00
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use crate::parser::{Expr, Stmt};
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fn optimize_stmt(stmt: Stmt, changed: &mut bool) -> Stmt {
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match stmt {
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Stmt::IfElse(expr, stmt1, None) => match *expr {
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Expr::False(pos) => {
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*changed = true;
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Stmt::Noop(pos)
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}
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Expr::True(_) => optimize_stmt(*stmt1, changed),
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2020-03-10 04:22:41 +01:00
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expr => Stmt::IfElse(
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Box::new(optimize_expr(expr, changed)),
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2020-03-09 14:57:07 +01:00
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Box::new(optimize_stmt(*stmt1, changed)),
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None,
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),
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},
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Stmt::IfElse(expr, stmt1, Some(stmt2)) => match *expr {
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Expr::False(_) => optimize_stmt(*stmt2, changed),
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Expr::True(_) => optimize_stmt(*stmt1, changed),
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2020-03-10 04:22:41 +01:00
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expr => Stmt::IfElse(
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Box::new(optimize_expr(expr, changed)),
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2020-03-09 14:57:07 +01:00
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Box::new(optimize_stmt(*stmt1, changed)),
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Some(Box::new(optimize_stmt(*stmt2, changed))),
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),
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},
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Stmt::While(expr, stmt) => match *expr {
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Expr::False(pos) => {
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*changed = true;
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Stmt::Noop(pos)
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}
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Expr::True(_) => Stmt::Loop(Box::new(optimize_stmt(*stmt, changed))),
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2020-03-10 04:22:41 +01:00
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expr => Stmt::While(
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Box::new(optimize_expr(expr, changed)),
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2020-03-09 14:57:07 +01:00
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Box::new(optimize_stmt(*stmt, changed)),
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),
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},
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Stmt::Loop(stmt) => Stmt::Loop(Box::new(optimize_stmt(*stmt, changed))),
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Stmt::For(id, expr, stmt) => Stmt::For(
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id,
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Box::new(optimize_expr(*expr, changed)),
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Box::new(optimize_stmt(*stmt, changed)),
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),
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Stmt::Let(id, Some(expr), pos) => {
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Stmt::Let(id, Some(Box::new(optimize_expr(*expr, changed))), pos)
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}
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Stmt::Let(_, None, _) => stmt,
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Stmt::Block(statements, pos) => {
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let original_len = statements.len();
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let mut result: Vec<_> = statements
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.into_iter() // For each statement
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.map(|s| optimize_stmt(s, changed)) // Optimize the statement
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.filter(Stmt::is_op) // Remove no-op's
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.collect();
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2020-03-10 04:22:41 +01:00
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if let Some(last_stmt) = result.pop() {
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// Remove all raw expression statements that evaluate to constants
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// except for the very last statement
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result.retain(|stmt| match stmt {
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2020-03-10 12:48:47 +01:00
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Stmt::Expr(expr) if expr.is_constant() || expr.is_identifier() => false,
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2020-03-10 04:22:41 +01:00
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_ => true,
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});
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result.push(last_stmt);
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}
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2020-03-09 14:57:07 +01:00
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*changed = *changed || original_len != result.len();
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match result[..] {
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[] => {
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// No statements in block - change to No-op
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*changed = true;
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Stmt::Noop(pos)
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}
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2020-03-10 04:22:41 +01:00
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[Stmt::Let(_, None, _)] => {
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// Only one empty variable declaration - change to No-op
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*changed = true;
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Stmt::Noop(pos)
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}
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[Stmt::Let(_, Some(_), _)] => {
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2020-03-09 14:57:07 +01:00
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// Only one let statement, but cannot promote
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// (otherwise the variable gets declared in the scope above)
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// and still need to run just in case there are side effects
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Stmt::Block(result, pos)
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}
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[_] => {
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2020-03-10 04:22:41 +01:00
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// Only one statement - promote
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2020-03-09 14:57:07 +01:00
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*changed = true;
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result.remove(0)
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}
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_ => Stmt::Block(result, pos),
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}
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}
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Stmt::Expr(expr) => Stmt::Expr(Box::new(optimize_expr(*expr, changed))),
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Stmt::ReturnWithVal(Some(expr), is_return, pos) => Stmt::ReturnWithVal(
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Some(Box::new(optimize_expr(*expr, changed))),
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is_return,
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pos,
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),
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2020-03-10 04:22:41 +01:00
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stmt @ Stmt::ReturnWithVal(None, _, _) => stmt,
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2020-03-09 14:57:07 +01:00
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2020-03-10 04:22:41 +01:00
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stmt @ Stmt::Noop(_) | stmt @ Stmt::Break(_) => stmt,
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2020-03-09 14:57:07 +01:00
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}
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}
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fn optimize_expr(expr: Expr, changed: &mut bool) -> Expr {
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match expr {
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Expr::IntegerConstant(_, _)
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| Expr::Identifier(_, _)
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| Expr::CharConstant(_, _)
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| Expr::StringConstant(_, _)
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| Expr::True(_)
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| Expr::False(_)
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| Expr::Unit(_) => expr,
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2020-03-10 11:32:01 +01:00
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#[cfg(not(feature = "no_float"))]
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Expr::FloatConstant(_, _) => expr,
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2020-03-09 14:57:07 +01:00
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Expr::Stmt(stmt, pos) => match optimize_stmt(*stmt, changed) {
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Stmt::Noop(_) => {
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*changed = true;
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Expr::Unit(pos)
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}
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Stmt::Expr(expr) => {
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*changed = true;
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*expr
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}
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stmt => Expr::Stmt(Box::new(stmt), pos),
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},
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Expr::Assignment(id, expr, pos) => {
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Expr::Assignment(id, Box::new(optimize_expr(*expr, changed)), pos)
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}
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Expr::Dot(lhs, rhs, pos) => Expr::Dot(
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Box::new(optimize_expr(*lhs, changed)),
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Box::new(optimize_expr(*rhs, changed)),
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pos,
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),
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2020-03-11 04:03:18 +01:00
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2020-03-10 10:10:33 +01:00
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#[cfg(not(feature = "no_index"))]
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Expr::Index(lhs, rhs, pos) => match (*lhs, *rhs) {
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(Expr::Array(mut items, _), Expr::IntegerConstant(i, _))
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if i >= 0
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&& (i as usize) < items.len()
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2020-03-10 11:32:01 +01:00
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&& !items.iter().any(|x| x.is_constant() || x.is_identifier()) =>
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2020-03-10 10:10:33 +01:00
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{
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2020-03-10 11:32:01 +01:00
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// Array where everything is a constant or identifier - promote the item
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2020-03-10 10:10:33 +01:00
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*changed = true;
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items.remove(i as usize)
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}
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(lhs, rhs) => Expr::Index(
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Box::new(optimize_expr(lhs, changed)),
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Box::new(optimize_expr(rhs, changed)),
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pos,
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),
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},
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2020-03-11 04:03:18 +01:00
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#[cfg(feature = "no_index")]
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Expr::Index(_, _, _) => panic!("encountered an index expression during no_index!"),
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2020-03-10 10:10:33 +01:00
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#[cfg(not(feature = "no_index"))]
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2020-03-09 14:57:07 +01:00
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Expr::Array(items, pos) => {
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let original_len = items.len();
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let items: Vec<_> = items
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.into_iter()
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.map(|expr| optimize_expr(expr, changed))
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.collect();
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*changed = *changed || original_len != items.len();
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Expr::Array(items, pos)
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}
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2020-03-11 04:03:18 +01:00
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#[cfg(feature = "no_index")]
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Expr::Array(_, _) => panic!("encountered an array during no_index!"),
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2020-03-09 14:57:07 +01:00
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Expr::And(lhs, rhs) => match (*lhs, *rhs) {
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(Expr::True(_), rhs) => {
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*changed = true;
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rhs
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}
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(Expr::False(pos), _) => {
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*changed = true;
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Expr::False(pos)
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}
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(lhs, Expr::True(_)) => {
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*changed = true;
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lhs
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}
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(lhs, rhs) => Expr::And(
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Box::new(optimize_expr(lhs, changed)),
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Box::new(optimize_expr(rhs, changed)),
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),
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},
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Expr::Or(lhs, rhs) => match (*lhs, *rhs) {
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(Expr::False(_), rhs) => {
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*changed = true;
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rhs
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}
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(Expr::True(pos), _) => {
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*changed = true;
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Expr::True(pos)
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}
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(lhs, Expr::False(_)) => {
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*changed = true;
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lhs
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}
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(lhs, rhs) => Expr::Or(
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Box::new(optimize_expr(lhs, changed)),
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Box::new(optimize_expr(rhs, changed)),
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),
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},
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Expr::FunctionCall(id, args, def_value, pos) => {
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let original_len = args.len();
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let args: Vec<_> = args
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.into_iter()
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.map(|a| optimize_expr(a, changed))
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.collect();
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*changed = *changed || original_len != args.len();
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Expr::FunctionCall(id, args, def_value, pos)
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}
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}
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}
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pub(crate) fn optimize(mut statements: Vec<Stmt>) -> Vec<Stmt> {
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loop {
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let mut changed = false;
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statements = statements
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.into_iter()
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.map(|stmt| optimize_stmt(stmt, &mut changed))
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.filter(Stmt::is_op)
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.collect();
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if !changed {
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break;
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}
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}
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statements
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}
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