1
0
Fork 0
mirror of synced 2025-09-24 04:40:05 +00:00
ZoKrates/zokrates_core/src/flatten/mod.rs
2018-10-24 20:52:24 -04:00

1567 lines
61 KiB
Rust

//! Module containing the `Flattener` to process a program that it is R1CS-able.
//!
//! @file flatten.rs
//! @author Dennis Kuhnert <dennis.kuhnert@campus.tu-berlin.de>
//! @author Jacob Eberhardt <jacob.eberhardt@tu-berlin.de>
//! @date 2017
use std::collections::{HashSet};
use typed_absy::*;
use field::Field;
use flat_absy::*;
use substitution::direct_substitution::DirectSubstitution;
use substitution::Substitution;
use helpers::{DirectiveStatement, Helper, RustHelper};
use types::Type;
use types::Signature;
use types::conversions::cast;
use absy::variable::Variable;
use absy::parameter::Parameter;
use bimap::BiMap;
/// Flattener, computes flattened program.
#[derive(Debug)]
pub struct Flattener {
/// Number of bits needed to represent the maximum value.
bits: usize,
/// Vector containing all used variables while processing the program.
variables: HashSet<FlatVariable>,
/// Map of renamings for reassigned variables while processing the program.
substitution: DirectSubstitution,
/// Index of the next introduced variable while processing the program.
next_var_idx: usize,
///
bijection: BiMap<String, FlatVariable>,
}
impl Flattener {
/// Returns a `Flattener` with fresh a fresh [substitution] and [variables].
///
/// # Arguments
///
/// * `bits` - Number of bits needed to represent the maximum value.
pub fn new(bits: usize) -> Flattener {
Flattener {
bits: bits,
variables: HashSet::new(),
substitution: DirectSubstitution::new(),
next_var_idx: 0,
bijection: BiMap::new(),
}
}
/// Loads the standard library
fn load_stdlib<T: Field>(
&mut self,
functions_flattened: &mut Vec<FlatFunction<T>>,
) -> () {
// Load type casting functions
functions_flattened.push(cast(&Type::Boolean, &Type::FieldElement));
functions_flattened.push(cast(&Type::FieldElement, &Type::Boolean));
// Load IfElse helpers
let ie = TypedFunction {
id: "_if_else_field".to_string(),
arguments: vec![Parameter {
id: Variable {
id: "condition".to_string(),
_type: Type::Boolean
},
private: true
},
Parameter {
id: Variable {
id: "consequence".to_string(),
_type: Type::FieldElement
},
private: true
},
Parameter {
id: Variable {
id: "alternative".to_string(),
_type: Type::FieldElement
},
private: true
}],
statements: vec![
TypedStatement::Definition(
Variable::field_element("condition_as_field"),
FieldElementExpression::FunctionCall(
"_bool_to_field".to_string(),
vec![
BooleanExpression::Identifier("condition".to_string()).into()
]
).into()
),
TypedStatement::Return(
vec![
FieldElementExpression::Add(
box FieldElementExpression::Mult(
box FieldElementExpression::Identifier("condition_as_field".to_string()),
box FieldElementExpression::Identifier("consequence".to_string()),
),
box FieldElementExpression::Mult(
box FieldElementExpression::Sub(
box FieldElementExpression::Number(T::one()),
box FieldElementExpression::Identifier("condition_as_field".to_string())
),
box FieldElementExpression::Identifier("alternative".to_string())
)
).into()
]
)
],
signature: Signature::new()
.inputs(vec![Type::Boolean, Type::FieldElement, Type::FieldElement])
.outputs(vec![Type::FieldElement])
};
let ief = self.flatten_function(
functions_flattened,
ie,
);
functions_flattened.push(ief);
}
/// Flattens a boolean expression
///
/// # Arguments
///
/// * `statements_flattened` - Vector where new flattened statements can be added.
/// * `condition` - `Condition` that will be flattened.
fn flatten_boolean_expression<T: Field>(
&mut self,
functions_flattened: &Vec<FlatFunction<T>>,
arguments_flattened: &Vec<FlatParameter>,
statements_flattened: &mut Vec<FlatStatement<T>>,
expression: BooleanExpression<T>,
) -> FlatExpression<T> { // those will be booleans in the future
match expression {
BooleanExpression::Identifier(x) => FlatExpression::Identifier(self.bijection.get_by_left(&x).unwrap().clone()),
BooleanExpression::Lt(box lhs, box rhs) => {
// We know from semantic checking that lhs and rhs have the same type
// What the expression will flatten to depends on that type
let lhs_flattened = self.flatten_field_expression(
functions_flattened,
arguments_flattened,
statements_flattened,
lhs,
);
let rhs_flattened = self.flatten_field_expression(
functions_flattened,
arguments_flattened,
statements_flattened,
rhs,
);
// lhs
let lhs_id = self.use_sym();
statements_flattened
.push(FlatStatement::Definition(lhs_id, lhs_flattened));
// check that lhs and rhs are within the right range, ie, their last two bits are zero
// lhs
{
// define variables for the bits
let lhs_bits: Vec<FlatVariable> = (0..self.bits).map(|_| self.use_sym()).collect();
// add a directive to get the bits
statements_flattened.push(FlatStatement::Directive(DirectiveStatement::new(
lhs_bits.clone(),
Helper::Rust(RustHelper::Bits),
vec![lhs_id]
)));
// bitness checks
for i in 0..self.bits - 2 {
statements_flattened.push(FlatStatement::Condition(
FlatExpression::Identifier(lhs_bits[i + 2]),
FlatExpression::Mult(
box FlatExpression::Identifier(lhs_bits[i + 2]),
box FlatExpression::Identifier(lhs_bits[i + 2]),
),
));
}
// bit decomposition check
let mut lhs_sum = FlatExpression::Number(T::from(0));
for i in 0..self.bits - 2 {
lhs_sum = FlatExpression::Add(
box lhs_sum,
box FlatExpression::Mult(
box FlatExpression::Identifier(lhs_bits[i + 2]),
box FlatExpression::Number(T::from(2).pow(self.bits - 2 - i - 1)),
),
);
}
statements_flattened
.push(FlatStatement::Condition(
FlatExpression::Identifier(lhs_id),
lhs_sum
)
);
}
// rhs
let rhs_id = self.use_sym();
statements_flattened
.push(FlatStatement::Definition(rhs_id, rhs_flattened));
// rhs
{
// define variables for the bits
let rhs_bits: Vec<FlatVariable> = (0..self.bits).map(|_| self.use_sym()).collect();
// add a directive to get the bits
statements_flattened.push(FlatStatement::Directive(DirectiveStatement::new(
rhs_bits.clone(),
Helper::Rust(RustHelper::Bits),
vec![rhs_id]
)));
// bitness checks
for i in 0..self.bits - 2 {
statements_flattened.push(FlatStatement::Condition(
FlatExpression::Identifier(rhs_bits[i + 2]),
FlatExpression::Mult(
box FlatExpression::Identifier(rhs_bits[i + 2]),
box FlatExpression::Identifier(rhs_bits[i + 2]),
),
));
}
// bit decomposition check
let mut rhs_sum = FlatExpression::Number(T::from(0));
for i in 0..self.bits - 2 {
rhs_sum = FlatExpression::Add(
box rhs_sum,
box FlatExpression::Mult(
box FlatExpression::Identifier(rhs_bits[i + 2]),
box FlatExpression::Number(T::from(2).pow(self.bits - 2 - i - 1)),
),
);
}
statements_flattened
.push(FlatStatement::Condition(
FlatExpression::Identifier(rhs_id),
rhs_sum
)
);
}
// sym = (lhs * 2) - (rhs * 2)
let subtraction_result_id = self.use_sym();
statements_flattened.push(FlatStatement::Definition(
subtraction_result_id,
FlatExpression::Sub(
box FlatExpression::Mult(box FlatExpression::Number(T::from(2)), box FlatExpression::Identifier(lhs_id)),
box FlatExpression::Mult(box FlatExpression::Number(T::from(2)), box FlatExpression::Identifier(rhs_id)),
),
));
// define variables for the bits
let sub_bits: Vec<FlatVariable> = (0..self.bits).map(|_| self.use_sym()).collect();
// add a directive to get the bits
statements_flattened.push(FlatStatement::Directive(DirectiveStatement::new(
sub_bits.clone(),
Helper::Rust(RustHelper::Bits),
vec![subtraction_result_id]
)));
// bitness checks
for i in 0..self.bits {
statements_flattened.push(FlatStatement::Condition(
FlatExpression::Identifier(sub_bits[i]),
FlatExpression::Mult(
box FlatExpression::Identifier(sub_bits[i]),
box FlatExpression::Identifier(sub_bits[i]),
),
));
}
// sum(sym_b{i} * 2**i)
let mut expr = FlatExpression::Number(T::from(0));
for i in 0..self.bits {
expr = FlatExpression::Add(
box expr,
box FlatExpression::Mult(
box FlatExpression::Identifier(sub_bits[i]),
box FlatExpression::Number(T::from(2).pow(self.bits - i - 1)),
),
);
}
statements_flattened
.push(FlatStatement::Condition(
FlatExpression::Identifier(subtraction_result_id),
expr
)
);
FlatExpression::Identifier(sub_bits[0])
}
BooleanExpression::Eq(box lhs, box rhs) => {
// We know from semantic checking that lhs and rhs have the same type
// What the expression will flatten to depends on that type
// Wanted: (Y = (X != 0) ? 1 : 0)
// X = a - b
// # Y = if X == 0 then 0 else 1 fi
// # M = if X == 0 then 1 else 1/X fi
// Y == X * M
// 0 == (1-Y) * X
let name_x = self.use_sym();
let name_y = self.use_sym();
let name_m = self.use_sym();
let name_1_y = self.use_sym();
let x = self.flatten_field_expression(
functions_flattened,
arguments_flattened,
statements_flattened,
FieldElementExpression::Sub(box lhs, box rhs),
);
statements_flattened.push(FlatStatement::Definition(name_x, x));
statements_flattened.push(
FlatStatement::Directive(DirectiveStatement {
outputs: vec![name_y, name_m],
inputs: vec![name_x],
helper: Helper::Rust(RustHelper::ConditionEq)
})
);
statements_flattened.push(FlatStatement::Condition(
FlatExpression::Identifier(name_y),
FlatExpression::Mult(box FlatExpression::Identifier(name_x), box FlatExpression::Identifier(name_m)),
));
statements_flattened.push(FlatStatement::Definition(
name_1_y,
FlatExpression::Sub(box FlatExpression::Number(T::one()), box FlatExpression::Identifier(name_y)),
));
statements_flattened.push(FlatStatement::Condition(
FlatExpression::Number(T::zero()),
FlatExpression::Mult(box FlatExpression::Identifier(name_1_y), box FlatExpression::Identifier(name_x)),
));
FlatExpression::Identifier(name_1_y)
},
BooleanExpression::Or(box lhs, box rhs) => {
let x = self.flatten_boolean_expression(
functions_flattened,
arguments_flattened,
statements_flattened,
lhs
);
let y = self.flatten_boolean_expression(
functions_flattened,
arguments_flattened,
statements_flattened,
rhs
);
assert!(x.is_linear() && y.is_linear());
let name_x = self.use_sym();
let name_y = self.use_sym();
let name_x_or_y = self.use_sym();
statements_flattened.push(FlatStatement::Definition(
name_x,
x
));
statements_flattened.push(FlatStatement::Definition(
name_y,
y
));
statements_flattened.push(FlatStatement::Definition(
name_x_or_y,
FlatExpression::Sub(
box FlatExpression::Add(
box FlatExpression::Identifier(name_x),
box FlatExpression::Identifier(name_y)
),
box FlatExpression::Mult(
box FlatExpression::Identifier(name_x),
box FlatExpression::Identifier(name_y)
)
)
));
FlatExpression::Identifier(name_x_or_y)
},
BooleanExpression::And(box lhs, box rhs) => {
let x = self.flatten_boolean_expression(
functions_flattened,
arguments_flattened,
statements_flattened,
lhs
);
let y = self.flatten_boolean_expression(
functions_flattened,
arguments_flattened,
statements_flattened,
rhs
);
let name_x_and_y = self.use_sym();
// flatten_boolean_expression always returns a linear term
assert!(x.is_linear() && y.is_linear());
statements_flattened.push(FlatStatement::Definition(
name_x_and_y, FlatExpression::Mult(box x, box y))
);
FlatExpression::Identifier(name_x_and_y)
},
BooleanExpression::Value(b) => {
FlatExpression::Number(match b {
true => T::from(1),
false => T::from(0)
})
},
_ => unimplemented!(),
}
}
fn flatten_function_call<T: Field>(
&mut self,
functions_flattened: &Vec<FlatFunction<T>>,
arguments_flattened: &Vec<FlatParameter>,
statements_flattened: &mut Vec<FlatStatement<T>>,
id: &String,
return_types: Vec<Type>,
param_expressions: &Vec<TypedExpression<T>>
) -> FlatExpressionList<T> {
let passed_signature = Signature::new()
.inputs(param_expressions.into_iter().map(|e| e.get_type()).collect())
.outputs(return_types);
for funct in functions_flattened {
if funct.id == *id && funct.signature == passed_signature {
// funct is now the called function
// Stores prefixed variables
let mut replacement_map = DirectSubstitution::new();
// Handle complex parameters and assign values:
// Rename Parameters, assign them to values in call. Resolve complex expressions with definitions
for (i, param_expr) in param_expressions.clone().into_iter().enumerate() {
let rhs = self.flatten_expression(
functions_flattened,
arguments_flattened,
statements_flattened,
param_expr,
).apply_recursive_substitution(&self.substitution);
let new_var = self.issue_new_variable();
statements_flattened
.push(FlatStatement::Definition(new_var, rhs));
replacement_map.insert(funct.arguments.get(i).unwrap().id.clone(), new_var);
}
// Ensure Renaming and correct returns:
// add all flattened statements, adapt return statement
for stat in funct.statements.clone() {
match stat {
// set return statements right sidreturne as expression result
FlatStatement::Return(list) => {
return FlatExpressionList {
expressions: list.expressions.into_iter().map(|x| x.apply_direct_substitution(&replacement_map)).collect()
}
},
FlatStatement::Definition(var, rhs) => {
let new_var = self.issue_new_variable();
replacement_map.insert(var, new_var);
let new_rhs = rhs.apply_direct_substitution(&replacement_map);
statements_flattened.push(
FlatStatement::Definition(new_var, new_rhs)
);
},
FlatStatement::Condition(lhs, rhs) => {
let new_lhs = lhs.apply_direct_substitution(&replacement_map);
let new_rhs = rhs.apply_direct_substitution(&replacement_map);
statements_flattened
.push(FlatStatement::Condition(new_lhs, new_rhs));
},
FlatStatement::Directive(d) => {
let new_outputs = d.outputs.into_iter().map(|o| {
let new_o = self.issue_new_variable();
replacement_map.insert(o, new_o);
new_o
}).collect();
let new_inputs = d.inputs.iter().map(|i| replacement_map.get(&i).unwrap()).collect();
statements_flattened.push(
FlatStatement::Directive(
DirectiveStatement {
outputs: new_outputs,
inputs: new_inputs,
helper: d.helper.clone()
}
)
)
}
}
}
}
}
panic!(
"TypedFunction definition for function {} with {:?} argument(s) not found. Should have been detected during semantic checking.",
id,
param_expressions
);
}
fn flatten_expression<T: Field>(
&mut self,
functions_flattened: &Vec<FlatFunction<T>>,
arguments_flattened: &Vec<FlatParameter>,
statements_flattened: &mut Vec<FlatStatement<T>>,
expr: TypedExpression<T>,
) -> FlatExpression<T> {
match expr {
TypedExpression::FieldElement(e) =>
self.flatten_field_expression(
functions_flattened,
arguments_flattened,
statements_flattened,
e,
),
TypedExpression::Boolean(e) =>
self.flatten_boolean_expression(
functions_flattened,
arguments_flattened,
statements_flattened,
e,
),
}
}
fn flatten_field_expression<T: Field>(
&mut self,
functions_flattened: &Vec<FlatFunction<T>>,
arguments_flattened: &Vec<FlatParameter>,
statements_flattened: &mut Vec<FlatStatement<T>>,
expr: FieldElementExpression<T>,
) -> FlatExpression<T> {
match expr {
FieldElementExpression::Number(x) => FlatExpression::Number(x), // force to be a field element
FieldElementExpression::Identifier(x) => FlatExpression::Identifier(self.bijection.get_by_left(&x).unwrap().clone()),
FieldElementExpression::Add(box left, box right) => {
let left_flattened = self.flatten_field_expression(
functions_flattened,
arguments_flattened,
statements_flattened,
left,
);
let right_flattened = self.flatten_field_expression(
functions_flattened,
arguments_flattened,
statements_flattened,
right,
);
let new_left = if left_flattened.is_linear() {
left_flattened
} else {
let id = self.use_sym();
statements_flattened
.push(FlatStatement::Definition(id, left_flattened));
FlatExpression::Identifier(id)
};
let new_right = if right_flattened.is_linear() {
right_flattened
} else {
let id = self.use_sym();
statements_flattened
.push(FlatStatement::Definition(id, right_flattened));
FlatExpression::Identifier(id)
};
FlatExpression::Add(box new_left, box new_right)
},
FieldElementExpression::Sub(box left, box right) => {
let left_flattened = self.flatten_field_expression(
functions_flattened,
arguments_flattened,
statements_flattened,
left,
);
let right_flattened = self.flatten_field_expression(
functions_flattened,
arguments_flattened,
statements_flattened,
right,
);
let new_left = if left_flattened.is_linear() {
left_flattened
} else {
let id = self.use_sym();
statements_flattened
.push(FlatStatement::Definition(id, left_flattened));
FlatExpression::Identifier(id)
};
let new_right = if right_flattened.is_linear() {
right_flattened
} else {
let id = self.use_sym();
statements_flattened
.push(FlatStatement::Definition(id, right_flattened));
FlatExpression::Identifier(id)
};
FlatExpression::Sub(box new_left, box new_right)
},
FieldElementExpression::Mult(box left, box right) => {
let left_flattened = self.flatten_field_expression(
functions_flattened,
arguments_flattened,
statements_flattened,
left,
);
let right_flattened = self.flatten_field_expression(
functions_flattened,
arguments_flattened,
statements_flattened,
right,
);
let new_left = if left_flattened.is_linear() {
if let FlatExpression::Sub(..) = left_flattened {
let id = self.use_sym();
statements_flattened
.push(FlatStatement::Definition(id, left_flattened));
FlatExpression::Identifier(id)
} else {
left_flattened
}
} else {
let id = self.use_sym();
statements_flattened
.push(FlatStatement::Definition(id, left_flattened));
FlatExpression::Identifier(id)
};
let new_right = if right_flattened.is_linear() {
if let FlatExpression::Sub(..) = right_flattened {
let id = self.use_sym();
statements_flattened
.push(FlatStatement::Definition(id, right_flattened));
FlatExpression::Identifier(id)
} else {
right_flattened
}
} else {
let id = self.use_sym();
statements_flattened
.push(FlatStatement::Definition(id, right_flattened));
FlatExpression::Identifier(id)
};
FlatExpression::Mult(box new_left, box new_right)
},
FieldElementExpression::Div(box left, box right) => {
let left_flattened = self.flatten_field_expression(
functions_flattened,
arguments_flattened,
statements_flattened,
left,
);
let right_flattened = self.flatten_field_expression(
functions_flattened,
arguments_flattened,
statements_flattened,
right,
);
let new_left = {
let id = self.use_sym();
statements_flattened
.push(FlatStatement::Definition(id, left_flattened));
FlatExpression::Identifier(id)
};
let new_right = {
let id = self.use_sym();
statements_flattened
.push(FlatStatement::Definition(id, right_flattened));
FlatExpression::Identifier(id)
};
FlatExpression::Div(box new_left, box new_right)
},
FieldElementExpression::Pow(box base, box exponent) => {
match exponent {
FieldElementExpression::Number(ref e) => {
// flatten the base expression
let base_flattened = self.flatten_field_expression(
functions_flattened,
arguments_flattened,
statements_flattened,
base.clone(),
).apply_recursive_substitution(&self.substitution);
// we require from the base to be linear
// TODO change that
assert!(base_flattened.is_linear());
match e {
// flatten(base ** 1) == flatten(base)
e if *e == T::one() => {
base_flattened
},
// flatten(base ** 2) == flatten(base) * flatten(base)
// in this case, no need to define an intermediate variable
// as if a is linear, a ** 2 quadratic
e if *e == T::from(2) => {
FlatExpression::Mult(box base_flattened.clone(), box base_flattened)
},
// flatten(base ** n) = flatten(base) * flatten(base ** (n-1))
e => {
// flatten(base ** (n-1))
let tmp_expression = self.flatten_field_expression(
functions_flattened,
arguments_flattened,
statements_flattened,
FieldElementExpression::Pow(
box base,
box FieldElementExpression::Number(e.clone() - T::one()),
),
).apply_recursive_substitution(&self.substitution);
let id = self.use_sym();
statements_flattened.push(
FlatStatement::Definition(id, tmp_expression));
FlatExpression::Mult(
box FlatExpression::Identifier(id),
box base_flattened,
)
}
}
},
_ => panic!("Expected number as pow exponent"),
}
},
FieldElementExpression::IfElse(box condition, box consequent, box alternative) => {
self.flatten_function_call(
functions_flattened,
arguments_flattened,
statements_flattened,
&"_if_else_field".to_string(),
vec![Type::FieldElement],
&vec![condition.into(), consequent.into(), alternative.into()],
).expressions[0].clone()
},
FieldElementExpression::FunctionCall(ref id, ref param_expressions) => {
let exprs_flattened = self.flatten_function_call(
functions_flattened,
arguments_flattened,
statements_flattened,
id,
vec![Type::FieldElement],
param_expressions
);
assert!(exprs_flattened.expressions.len() == 1); // outside of MultipleDefinition, FunctionCalls must return a single value
exprs_flattened.expressions[0].clone()
}
}
}
pub fn flatten_statement<T: Field>(
&mut self,
functions_flattened: &mut Vec<FlatFunction<T>>,
arguments_flattened: &Vec<FlatParameter>,
statements_flattened: &mut Vec<FlatStatement<T>>,
stat: TypedStatement<T>,
) {
match stat {
TypedStatement::Return(exprs) => {
let flat_expressions = exprs.into_iter().map(|expr|
self.flatten_expression(
functions_flattened,
arguments_flattened,
statements_flattened,
expr
).apply_recursive_substitution(&self.substitution)
).collect();
statements_flattened.push(
FlatStatement::Return(
FlatExpressionList {
expressions: flat_expressions
}
)
);
}
TypedStatement::Declaration(_) => {
// declarations have already been checked
()
}
TypedStatement::Definition(v, expr) => {
// define n variables with n the number of primitive types for v_type
// assign them to the n primitive types for expr
let rhs = self.flatten_expression(
functions_flattened,
arguments_flattened,
statements_flattened,
expr
).apply_recursive_substitution(&self.substitution);
let var = self.use_variable(&v.id);
// handle return of function call
let var_to_replace = self.get_latest_var_substitution(&v.id);
if !(var == var_to_replace) && self.variables.contains(&var_to_replace) && !self.substitution.contains_key(&var_to_replace){
self.substitution.insert(var_to_replace.clone(),var.clone());
}
statements_flattened.push(FlatStatement::Definition(var, rhs));
}
TypedStatement::Condition(expr1, expr2) => {
// flatten expr1 and expr2 to n flattened expressions with n the number of primitive types for expr1
// add n conditions to check equality of the n expressions
match (expr1, expr2) {
(TypedExpression::FieldElement(e1), TypedExpression::FieldElement(e2)) => {
let (lhs, rhs) =
(
self.flatten_field_expression(
functions_flattened,
arguments_flattened,
statements_flattened,
e1
).apply_recursive_substitution(&self.substitution),
self.flatten_field_expression(
functions_flattened,
arguments_flattened,
statements_flattened,
e2,
).apply_recursive_substitution(&self.substitution),
);
if lhs.is_linear() {
statements_flattened.push(FlatStatement::Condition(lhs, rhs));
} else if rhs.is_linear() {
// swap so that left side is linear
statements_flattened.push(FlatStatement::Condition(rhs, lhs));
} else {
unimplemented!()
}
},
(TypedExpression::Boolean(e1), TypedExpression::Boolean(e2)) => {
let (lhs, rhs) =
(
self.flatten_boolean_expression(
functions_flattened,
arguments_flattened,
statements_flattened,
e1
).apply_recursive_substitution(&self.substitution),
self.flatten_boolean_expression(
functions_flattened,
arguments_flattened,
statements_flattened,
e2,
).apply_recursive_substitution(&self.substitution),
);
if lhs.is_linear() {
statements_flattened.push(FlatStatement::Condition(lhs, rhs));
} else if rhs.is_linear() {
// swap so that left side is linear
statements_flattened.push(FlatStatement::Condition(rhs, lhs));
} else {
unimplemented!()
}
},
_ => panic!("non matching types in condition should have been caught at semantic stage")
}
}
TypedStatement::For(var, start, end, statements) => {
let mut current = start;
while current < end {
statements_flattened.push(FlatStatement::Definition(
self.use_variable(&var.id),
FlatExpression::Number(current.clone()),
));
for s in statements.clone() {
self.flatten_statement(
functions_flattened,
arguments_flattened,
statements_flattened,
s,
);
}
current = T::one() + &current;
}
}
TypedStatement::MultipleDefinition(vars, rhs) => {
// flatten the right side to p = sum(var_i.type.primitive_count) expressions
// define p new variables to the right side expressions
let var_types = vars.iter().map(|v| v.get_type()).collect();
match rhs {
TypedExpressionList::FunctionCall(fun_id, exprs, _) => {
let rhs_flattened = self.flatten_function_call(
functions_flattened,
arguments_flattened,
statements_flattened,
&fun_id,
var_types,
&exprs,
).apply_recursive_substitution(&self.substitution);
// this will change for types that have multiple underlying fe
for (i, v) in vars.into_iter().enumerate() {
let var = self.use_variable(&v.id);
// handle return of function call
let var_to_replace = self.get_latest_var_substitution(&v.id);
if !(var == var_to_replace) && self.variables.contains(&var_to_replace) && !self.substitution.contains_key(&var_to_replace){
self.substitution.insert(var_to_replace.clone(),var.clone());
}
statements_flattened.push(FlatStatement::Definition(var, rhs_flattened.expressions[i].clone()));
}
},
}
},
}
}
/// Returns a flattened `TypedFunction` based on the given `funct`.
///
/// # Arguments
///
/// * `functions_flattened` - Vector where new flattened functions can be added.
/// * `funct` - `TypedFunction` that will be flattened.
pub fn flatten_function<T: Field>(
&mut self,
functions_flattened: &mut Vec<FlatFunction<T>>,
funct: TypedFunction<T>,
) -> FlatFunction<T> {
self.variables = HashSet::new();
self.substitution = DirectSubstitution::new();
self.bijection = BiMap::new();
self.next_var_idx = 0;
let mut arguments_flattened: Vec<FlatParameter> = Vec::new();
let mut statements_flattened: Vec<FlatStatement<T>> = Vec::new();
// push parameters
for arg in &funct.arguments {
let arg_type = arg.id.get_type();
match arg_type {
Type::FieldElement => {
arguments_flattened.push(FlatParameter {
id: self.use_variable(&arg.id.id),
private: arg.private
});
},
Type::Boolean => {
arguments_flattened.push(FlatParameter {
id: self.use_variable(&arg.id.id),
private: arg.private
});
},
}
}
// flatten statements in functions and apply substitution
for stat in funct.statements {
self.flatten_statement(
functions_flattened,
&arguments_flattened,
&mut statements_flattened,
stat,
);
}
FlatFunction {
id: funct.id.clone(),
arguments: arguments_flattened,
statements: statements_flattened,
signature: funct.signature
}
}
/// Returns a flattened `Prog`ram based on the given `prog`.
///
/// # Arguments
///
/// * `prog` - `Prog`ram that will be flattened.
pub fn flatten_program<T: Field>(&mut self, prog: TypedProg<T>) -> FlatProg<T> {
let mut functions_flattened = Vec::new();
self.load_stdlib(&mut functions_flattened);
for func in prog.imported_functions {
functions_flattened.push(func);
}
for func in prog.functions {
let flattened_func = self.flatten_function(&mut functions_flattened, func);
functions_flattened.push(flattened_func);
}
FlatProg {
functions: functions_flattened
}
}
/// Checks if the given name is a not used variable and returns a fresh variable.
/// # Arguments
///
/// * `name` - a String that holds the name of the variable
fn use_variable(&mut self, name: &String) -> FlatVariable {
// issue the variable we'll use
let var = self.issue_new_variable();
// {
// // we check if the name was already given a variable
// let id = self.bijection.get_by_left(name);
// match id {
// Some(id) => {
// // the name was already registered. We need to find its latest substitution
// let mut id = *id;
// // loop {
// // match self.substitution.get(&id) {
// // Some(x) => id = x,
// // None => break,
// // }
// // }
// // now `id` is the latest substitution of `name`
// // link it to the previous one
// //assert!(!(id == var));
// //self.bijection.insert(name.to_string(), var);
// },
// None => {
// }
// }
// }
self.bijection.insert(name.to_string(), var);
var
}
fn issue_new_variable(&mut self) -> FlatVariable {
let var = FlatVariable::new(self.next_var_idx);
self.next_var_idx += 1;
var
}
fn use_sym(&mut self) -> FlatVariable {
let name = format!("sym_{}", self.next_var_idx);
let var = self.issue_new_variable();
self.bijection.insert(name, var);
var
}
fn get_latest_var_substitution(&mut self, name: &String) -> FlatVariable {
// start with the variable name
let latest_var = self.bijection.get_by_left(name).unwrap().clone();
// loop {
// // walk the substitutions
// match self.substitution.get(&latest_var) {
// Some(x) => latest_var = x,
// None => break,
// }
// }
latest_var
}
}
#[cfg(test)]
mod tests {
use super::*;
use field::FieldPrime;
use types::Type;
use types::Signature;
use absy::variable::Variable;
#[test]
fn multiple_definition() {
// def foo()
// return 1, 2
// def main()
// a, b = foo()
let mut flattener = Flattener::new(FieldPrime::get_required_bits());
let mut functions_flattened = vec![
FlatFunction {
id: "foo".to_string(),
arguments: vec![],
statements: vec![FlatStatement::Return(
FlatExpressionList {
expressions: vec![
FlatExpression::Number(FieldPrime::from(1)),
FlatExpression::Number(FieldPrime::from(2))
]
}
)],
signature: Signature::new()
.inputs(vec![])
.outputs(vec![Type::FieldElement, Type::FieldElement])
}
];
let arguments_flattened = vec![];
let mut statements_flattened = vec![];
let statement = TypedStatement::MultipleDefinition(
vec![
Variable::field_element("a".to_string()),
Variable::field_element("b".to_string())
],
TypedExpressionList::FunctionCall("foo".to_string(), vec![], vec![Type::FieldElement, Type::FieldElement])
);
flattener.flatten_statement(
&mut functions_flattened,
&arguments_flattened,
&mut statements_flattened,
statement,
);
let a = FlatVariable::new(0);
assert_eq!(
statements_flattened[0]
,
FlatStatement::Definition(a, FlatExpression::Number(FieldPrime::from(1)))
);
}
#[test]
fn multiple_definition2() {
// def dup(x)
// return x, x
// def main()
// a, b = dup(2)
let a = FlatVariable::new(0);
let mut flattener = Flattener::new(FieldPrime::get_required_bits());
let mut functions_flattened = vec![
FlatFunction {
id: "dup".to_string(),
arguments: vec![FlatParameter { id: a, private: true }],
statements: vec![FlatStatement::Return(
FlatExpressionList {
expressions: vec![
FlatExpression::Identifier(a),
FlatExpression::Identifier(a),
]
}
)],
signature: Signature::new()
.inputs(vec![Type::FieldElement])
.outputs(vec![Type::FieldElement, Type::FieldElement])
}
];
let statement = TypedStatement::MultipleDefinition(
vec![
Variable::field_element("a".to_string()),
Variable::field_element("b".to_string())
],
TypedExpressionList::FunctionCall("dup".to_string(), vec![TypedExpression::FieldElement(FieldElementExpression::Number(FieldPrime::from(2)))], vec![Type::FieldElement, Type::FieldElement])
);
let fun = TypedFunction {
id: String::from("main"),
arguments: vec![],
statements: vec![statement],
signature: Signature {
inputs: vec![],
outputs: vec![]
}
};
let f = flattener.flatten_function(
&mut functions_flattened,
fun,
);
let a = FlatVariable::new(0);
assert_eq!(
f.statements[0]
,
FlatStatement::Definition(a, FlatExpression::Number(FieldPrime::from(2)))
);
}
#[test]
fn simple_definition() {
// def foo()
// return 1
// def main()
// a = foo()
let mut flattener = Flattener::new(FieldPrime::get_required_bits());
let mut functions_flattened = vec![
FlatFunction {
id: "foo".to_string(),
arguments: vec![],
statements: vec![FlatStatement::Return(
FlatExpressionList {
expressions: vec![
FlatExpression::Number(FieldPrime::from(1))
]
}
)],
signature: Signature::new()
.inputs(vec![])
.outputs(vec![Type::FieldElement])
}
];
let arguments_flattened = vec![];
let mut statements_flattened = vec![];
let statement = TypedStatement::Definition(
Variable::field_element("a".to_string()),
TypedExpression::FieldElement(FieldElementExpression::FunctionCall("foo".to_string(), vec![]))
);
flattener.flatten_statement(
&mut functions_flattened,
&arguments_flattened,
&mut statements_flattened,
statement,
);
let a = FlatVariable::new(0);
assert_eq!(
statements_flattened[0]
,
FlatStatement::Definition(a, FlatExpression::Number(FieldPrime::from(1)))
);
}
#[test]
fn redefine_argument() {
// def foo(a)
// a = a + 1
// return 1
// should flatten to no redefinition
// def foo(a)
// a_0 = a + 1
// return 1
let mut flattener = Flattener::new(FieldPrime::get_required_bits());
let mut functions_flattened = vec![];
let funct = TypedFunction {
id: "foo".to_string(),
signature: Signature::new()
.inputs(vec![Type::FieldElement])
.outputs(vec![Type::FieldElement])
,
arguments: vec![Parameter { id: Variable::field_element("a"), private: true }],
statements: vec![
TypedStatement::Definition(
Variable::field_element("a".to_string()),
FieldElementExpression::Add(
box FieldElementExpression::Identifier("a".to_string()),
box FieldElementExpression::Number(FieldPrime::from(1))
).into()
),
TypedStatement::Return(
vec![FieldElementExpression::Number(FieldPrime::from(1)).into()]
)
],
};
let flat_funct = flattener.flatten_function(
&mut functions_flattened,
funct,
);
let a = FlatVariable::new(0);
let a_0 = FlatVariable::new(1);
assert_eq!(
flat_funct.statements[0],
FlatStatement::Definition(a_0, FlatExpression::Add(box FlatExpression::Identifier(a), box FlatExpression::Number(FieldPrime::from(1))))
);
}
#[test]
fn call_with_def() {
// def foo():
// a = 3
// return a
// def main():
// return foo()
let foo = TypedFunction {
id: String::from("foo"),
arguments: vec![],
statements: vec![
TypedStatement::Definition(Variable::field_element("a"), FieldElementExpression::Number(FieldPrime::from(3)).into()),
TypedStatement::Return(vec![
FieldElementExpression::Identifier(String::from("a")).into()
]
)
],
signature: Signature {
inputs: vec![],
outputs: vec![Type::FieldElement]
}
};
let main = TypedFunction {
id: String::from("main"),
arguments: vec![],
statements: vec![
TypedStatement::Return(vec![
FieldElementExpression::FunctionCall(String::from("foo"), vec![]).into()
]
)
],
signature: Signature {
inputs: vec![],
outputs: vec![Type::FieldElement]
}
};
let mut flattener = Flattener::new(FieldPrime::get_required_bits());
let foo_flattened = flattener.flatten_function(
&mut vec![],
foo
);
let expected = FlatFunction {
id: String::from("main"),
arguments: vec![],
statements: vec![
FlatStatement::Definition(FlatVariable::new(0), FlatExpression::Number(FieldPrime::from(3))),
FlatStatement::Return(FlatExpressionList {
expressions: vec![FlatExpression::Identifier(FlatVariable::new(0))]
})
],
signature: Signature::new().outputs(vec![Type::FieldElement])
};
let main_flattened = flattener.flatten_function(
&mut vec![foo_flattened],
main
);
assert_eq!(main_flattened, expected);
}
#[test]
fn powers() {
// def main():
// _0 = 7
// _1 = (_0 * _0)
// _2 = (_1 * _0)
// _3 = (_2 * _0)
// return _3
let function = TypedFunction {
id: String::from("main"),
arguments: vec![],
statements: vec![
TypedStatement::Definition(Variable::field_element("a"), FieldElementExpression::Number(FieldPrime::from(7)).into()),
TypedStatement::Definition(Variable::field_element("b"), FieldElementExpression::Pow(box FieldElementExpression::Identifier(String::from("a")), box FieldElementExpression::Number(FieldPrime::from(4))).into()),
TypedStatement::Return(vec![
FieldElementExpression::Identifier(String::from("b")).into()
]
)
],
signature: Signature {
inputs: vec![],
outputs: vec![Type::FieldElement]
}
};
let mut flattener = Flattener::new(FieldPrime::get_required_bits());
let expected = FlatFunction {
id: String::from("main"),
arguments: vec![],
statements: vec![
FlatStatement::Definition(FlatVariable::new(0), FlatExpression::Number(FieldPrime::from(7))),
FlatStatement::Definition(FlatVariable::new(1), FlatExpression::Mult(box FlatExpression::Identifier(FlatVariable::new(0)), box FlatExpression::Identifier(FlatVariable::new(0)))),
FlatStatement::Definition(FlatVariable::new(2), FlatExpression::Mult(box FlatExpression::Identifier(FlatVariable::new(1)), box FlatExpression::Identifier(FlatVariable::new(0)))),
FlatStatement::Definition(FlatVariable::new(3), FlatExpression::Mult(box FlatExpression::Identifier(FlatVariable::new(2)), box FlatExpression::Identifier(FlatVariable::new(0)))),
FlatStatement::Return(FlatExpressionList {
expressions: vec![
FlatExpression::Identifier(FlatVariable::new(3))
]
})
],
signature: Signature::new().outputs(vec![Type::FieldElement])
};
let flattened = flattener.flatten_function(
&mut vec![],
function
);
assert_eq!(flattened, expected);
}
#[test]
fn overload() {
// def foo()
// return 1
// def foo()
// return 1, 2
// def main()
// a = foo()
// b, c = foo()
// return 1
//
// should not panic
//
let mut flattener = Flattener::new(FieldPrime::get_required_bits());
let functions = vec![
TypedFunction {
id: "foo".to_string(),
arguments: vec![],
statements: vec![TypedStatement::Return(
vec![
TypedExpression::FieldElement(FieldElementExpression::Number(FieldPrime::from(1)))
]
)],
signature: Signature::new()
.inputs(vec![])
.outputs(vec![Type::FieldElement])
,
},
TypedFunction {
id: "foo".to_string(),
arguments: vec![],
statements: vec![TypedStatement::Return(
vec![
TypedExpression::FieldElement(FieldElementExpression::Number(FieldPrime::from(1))),
TypedExpression::FieldElement(FieldElementExpression::Number(FieldPrime::from(2)))
]
)],
signature: Signature::new()
.inputs(vec![])
.outputs(vec![Type::FieldElement, Type::FieldElement])
,
},
TypedFunction {
id: "main".to_string(),
arguments: vec![],
statements: vec![
TypedStatement::Definition(Variable::field_element("a".to_string()), TypedExpression::FieldElement(FieldElementExpression::FunctionCall("foo".to_string(), vec![]))),
TypedStatement::MultipleDefinition(vec![Variable::field_element("b".to_string()), Variable::field_element("c".to_string())], TypedExpressionList::FunctionCall("foo".to_string(), vec![], vec![Type::FieldElement, Type::FieldElement])),
TypedStatement::Return(
vec![TypedExpression::FieldElement(FieldElementExpression::Number(FieldPrime::from(1)))]
)
],
signature: Signature::new()
.inputs(vec![])
.outputs(vec![Type::FieldElement])
,
}
];
flattener.flatten_program(
TypedProg {
functions: functions,
imported_functions: vec![],
imports: vec![]
}
);
// shouldn't panic
}
#[test]
fn if_else() {
let expression =
FieldElementExpression::IfElse(
box BooleanExpression::Eq(
box FieldElementExpression::Number(FieldPrime::from(32)),
box FieldElementExpression::Number(FieldPrime::from(4))
),
box FieldElementExpression::Number(FieldPrime::from(12)),
box FieldElementExpression::Number(FieldPrime::from(51)),
);
let mut functions_flattened = vec![];
let mut flattener = Flattener::new(FieldPrime::get_required_bits());
flattener.load_stdlib(&mut functions_flattened);
flattener.flatten_field_expression(
&functions_flattened,
&vec![],
&mut vec![],
expression
);
}
#[test]
fn bool_and() {
let expression =
FieldElementExpression::IfElse(
box BooleanExpression::And(
box BooleanExpression::Eq(
box FieldElementExpression::Number(FieldPrime::from(4)),
box FieldElementExpression::Number(FieldPrime::from(4))
),
box BooleanExpression::Lt(
box FieldElementExpression::Number(FieldPrime::from(4)),
box FieldElementExpression::Number(FieldPrime::from(20))
),
),
box FieldElementExpression::Number(FieldPrime::from(12)),
box FieldElementExpression::Number(FieldPrime::from(51)),
);
let mut functions_flattened = vec![];
let mut flattener = Flattener::new(FieldPrime::get_required_bits());
flattener.load_stdlib(&mut functions_flattened);
flattener.flatten_field_expression(
&functions_flattened,
&vec![],
&mut vec![],
expression
);
}
#[test]
fn next_variable() {
let mut flattener = Flattener::new(FieldPrime::get_required_bits());
assert_eq!(FlatVariable::new(0), flattener.use_variable(&String::from("a")));
assert_eq!(flattener.get_latest_var_substitution(&String::from("a")), FlatVariable::new(0));
assert_eq!(FlatVariable::new(1), flattener.use_variable(&String::from("a")));
assert_eq!(flattener.get_latest_var_substitution(&String::from("a")), FlatVariable::new(1));
assert_eq!(FlatVariable::new(2), flattener.use_variable(&String::from("a")));
assert_eq!(flattener.get_latest_var_substitution(&String::from("a")), FlatVariable::new(2));
}
}