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use std::collections::HashMap;
use crate::{
ir::{
expressions::{Expr, ExprKind, Operator},
memory::Memory,
Guard, IfStmt, LivetimeEquivalences, Stmt, StreamReference,
},
rewrite_rules::{CombineSeq, RemoveSkip},
};
use super::{ChangeSet, RewriteError, RewriteRule};
#[derive(Debug, Clone, Copy)]
/// A rewriting rule that transforms an iterate statement into an assign if the parameter is uniquely defined by an
/// conditional directly inside the iterate.
pub struct IterateAssign;
impl RewriteRule for IterateAssign {
fn rewrite_stmt(
&self,
stmt: Stmt,
memory: &HashMap<StreamReference, Memory>,
_liveness_equivalences: &LivetimeEquivalences,
) -> Result<(Stmt, ChangeSet), RewriteError> {
match stmt {
Stmt::Iterate { sr, stmt } => match *stmt {
Stmt::If(IfStmt { guard, cons, alt }) if matches!(*alt, Stmt::Skip) => {
match guard
.split_unique_parameter(memory.get(&sr[0].sr()).unwrap().num_parameters())
{
Ok((assignment, remaining)) => Ok((
Stmt::Assign {
parameter_expr: assignment,
sr,
stmt: Box::new(Stmt::If(IfStmt {
guard: remaining,
cons,
alt,
})),
},
ChangeSet::local_change(),
)),
Err(guard) => Ok((
Stmt::Iterate {
sr,
stmt: Box::new(Stmt::If(IfStmt { guard, cons, alt })),
},
ChangeSet::default(),
)),
}
}
other => Ok((
Stmt::Iterate {
sr,
stmt: Box::new(other),
},
ChangeSet::default(),
)),
},
stmt => Ok((stmt, ChangeSet::default())),
}
}
fn cleanup_rules(&self) -> Vec<Box<dyn RewriteRule>> {
vec![Box::new(RemoveSkip), Box::new(CombineSeq)]
}
}
impl Guard {
fn split_unique_parameter(self, num_parameters: usize) -> Result<(Vec<Expr>, Guard), Guard> {
match self.clone().split_unique_parameter_prime() {
Ok((assignment, remaining)) => {
let parameter_exprs = assignment
.into_iter()
.try_fold(vec![None; num_parameters], |mut exprs, (idx, expr)| {
if exprs[idx].is_none() {
exprs[idx] = Some(expr);
Ok(exprs)
} else {
Err(())
}
})
.and_then(|exprs| {
exprs
.into_iter()
.map(|i| i.ok_or(()))
.collect::<Result<Vec<_>, ()>>()
});
match parameter_exprs {
Ok(exprs) => Ok((exprs, remaining)),
Err(()) => Err(self),
}
}
Err(e) => Err(e),
}
}
fn split_unique_parameter_prime(self) -> Result<(Vec<(usize, Expr)>, Guard), Guard> {
match self {
Guard::Constant(_)
| Guard::Stream(_)
| Guard::Alive(_)
| Guard::GlobalFreq(_)
| Guard::LocalFreq(_)
| Guard::FastAnd(_)
| Guard::FastOr(_) => Err(self),
Guard::Dynamic(Expr {
kind: ExprKind::BinaryOperation(Operator::Eq, lhs, rhs),
ty,
}) => match (*lhs, *rhs) {
(
Expr {
kind: ExprKind::ParameterAccess(_, idx),
..
},
other,
)
| (
other,
Expr {
kind: ExprKind::ParameterAccess(_, idx),
..
},
) => Ok((vec![(idx, other)], Guard::Constant(true))),
(lhs, rhs) => Err(Guard::Dynamic(Expr {
kind: ExprKind::BinaryOperation(Operator::Eq, Box::new(lhs), Box::new(rhs)),
ty,
})),
},
Guard::Dynamic(_) => Err(self),
Guard::And { lhs, rhs } => {
let lhs = lhs.split_unique_parameter_prime();
let rhs = rhs.split_unique_parameter_prime();
match (lhs, rhs) {
(Ok((mut l_assignment, lhs)), Ok((r_assignment, rhs))) => {
l_assignment.extend(r_assignment);
Ok((
l_assignment,
Guard::And {
lhs: Box::new(lhs),
rhs: Box::new(rhs),
},
))
}
(Ok((assignment, remaining)), Err(other))
| (Err(other), Ok((assignment, remaining))) => Ok((
assignment,
Guard::And {
lhs: Box::new(remaining),
rhs: Box::new(other),
},
)),
(Err(lhs), Err(rhs)) => Err(Guard::And {
lhs: Box::new(lhs),
rhs: Box::new(rhs),
}),
}
}
Guard::Or { lhs, rhs } => Err(Guard::Or { lhs, rhs }),
}
}
}
#[cfg(test)]
mod tests {
use crate::{
ir::parse::parse_ir,
rewrite_rules::{
assign::IterateAssign, skip::RemoveSkip, RemoveIfs, Rewriter, SimplifyGuard,
},
};
#[test]
fn not_enough_assignments() {
// NOTE: in the test setup every stream has 3 parameters
let ir = parse_ir(
"
iterate 0
if Expr(p0 == s0) then
input 0
fi
",
);
let rewriter = Rewriter::new(vec![Box::new(IterateAssign {})]);
let (res, changed) = rewriter.apply(ir.clone()).unwrap();
assert!(!changed);
assert!(res.stmt.eq(&ir.stmt));
}
#[test]
fn enough_assignments() {
// NOTE: in the test setup every stream has 3 parameters
let ir = parse_ir(
"
iterate 0
if Expr(p0 == s0) && Expr(s0 == p1) && Expr(p2 == s1) then
input 0
fi
",
);
let reference = parse_ir(
"
assign 0 (s0,s0,s1)
input 0
",
);
let rewriter = Rewriter::new(vec![
Box::new(IterateAssign {}),
Box::new(SimplifyGuard {}),
Box::new(RemoveIfs {}),
Box::new(RemoveSkip {}),
]);
let (res, changed) = rewriter.apply(ir).unwrap();
assert!(changed);
assert!(res.stmt.eq(&reference.stmt));
}
}