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refactor(cast): merge upcast and downcast implementation of felt252 c… #1652

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Merged
TomerStarkware merged 1 commit into from
Aug 5, 2026
Merged

refactor(cast): merge upcast and downcast implementation of felt252 c… #1652

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137 changes: 64 additions & 73 deletions src/libfuncs/cast.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -177,49 +177,22 @@ pub fn build_downcast<'ctx, 'this>(
src_value
};

let to_range = &info.to_range;

// Check if the source type is included in the target type. If it is not
// then check if the value is in bounds. If the value is also not in
// bounds then return an error.
if dst_range.lower <= src_range.lower && dst_range.upper >= src_range.upper {
let dst_value = if dst_ty.is_bounded_int(registry)? && dst_range.lower != BigInt::ZERO {
let dst_offset = entry.const_int_from_type(
context,
location,
dst_range.lower,
src_value.r#type(),
)?;
entry.append_op_result(arith::subi(src_value, dst_offset, location))?
} else {
src_value
};

let dst_value = if dst_width < compute_width {
entry.trunci(
dst_value,
IntegerType::new(context, dst_width).into(),
location,
)?
} else {
dst_value
};

let is_in_bounds = entry.const_int(context, location, 1, 1)?;

helper.cond_br(
context,
entry,
is_in_bounds,
[0, 1],
[&[range_check, dst_value], &[range_check]],
location,
)?;
let (is_in_bounds, range_check) = if to_range.lower <= src_range.lower
&& to_range.upper >= src_range.upper
{
(entry.const_int(context, location, 1, 1)?, range_check)
} else {
// Check if the value is in bounds with respect to the lower bound.
let lower_check = if dst_range.lower > src_range.lower {
let lower_check = if to_range.lower > src_range.lower {
let dst_lower = entry.const_int_from_type(
context,
location,
dst_range.lower.clone(),
to_range.lower.clone(),
src_value.r#type(),
)?;
Some(entry.cmpi(
Expand All @@ -237,11 +210,11 @@ pub fn build_downcast<'ctx, 'this>(
None
};
// Check if the value is in bounds with respect to the upper bound.
let upper_check = if dst_range.upper < src_range.upper {
let upper_check = if to_range.upper < src_range.upper {
let dst_upper = entry.const_int_from_type(
context,
location,
dst_range.upper.clone(),
to_range.upper.clone(),
src_value.r#type(),
)?;
Some(entry.cmpi(
Expand Down Expand Up @@ -285,7 +258,7 @@ pub fn build_downcast<'ctx, 'this>(
entry,
location,
range_check,
if dst_range.size() < rc_size { 2 } else { 1 },
if to_range.size() < rc_size { 2 } else { 1 },
3,
is_in_bounds,
)?
Expand Down Expand Up @@ -317,37 +290,44 @@ pub fn build_downcast<'ctx, 'this>(
}
};

let dst_value = if dst_ty.is_bounded_int(registry)? && dst_range.lower != BigInt::ZERO {
let dst_offset = entry.const_int_from_type(
context,
location,
dst_range.lower,
src_value.r#type(),
)?;
entry.append_op_result(arith::subi(src_value, dst_offset, location))?
} else {
src_value
};
(is_in_bounds, range_check)
};

let dst_value = if dst_width < compute_width {
entry.trunci(
dst_value,
IntegerType::new(context, dst_width).into(),
location,
)?
} else {
dst_value
};
let dst_value = if dst_ty.is_bounded_int(registry)? && dst_range.lower != BigInt::ZERO {
let dst_offset =
entry.const_int_from_type(context, location, dst_range.lower, src_value.r#type())?;
entry.append_op_result(arith::subi(src_value, dst_offset, location))?
} else {
src_value
};

helper.cond_br(
context,
entry,
is_in_bounds,
[0, 1],
[&[range_check, dst_value], &[range_check]],
// When converting to a felt from a signed integer, we need to convert
// the canonical signed integer representation, to the signed felt
// representation: `negative = P - absolute`.
let dst_value = if dst_ty.is_felt252(registry)? && src_range.lower.sign() == Sign::Minus {
signed_to_felt252_repr(context, entry, location, dst_value)?
} else {
dst_value
};

let dst_value = if dst_width < compute_width {
entry.trunci(
dst_value,
IntegerType::new(context, dst_width).into(),
location,
)?;
}
)?
} else {
dst_value
};

helper.cond_br(
context,
entry,
is_in_bounds,
[0, 1],
[&[range_check, dst_value], &[range_check]],
location,
)?;

Ok(())
}
Expand Down Expand Up @@ -455,20 +435,31 @@ pub fn build_upcast<'ctx, 'this>(
// the canonical signed integer representation, to the signed felt
// representation: `negative = P - absolute`.
let dst_value = if dst_ty.is_felt252(registry)? && src_range.lower.sign() == Sign::Minus {
let k0 = entry.const_int(context, location, 0, 252)?;
let is_negative = entry.cmpi(context, CmpiPredicate::Slt, dst_value, k0, location)?;

let k_prime = entry.const_int(context, location, PRIME.clone(), 252)?;
let adj_value = entry.addi(dst_value, k_prime, location)?;

entry.append_op_result(arith::select(is_negative, adj_value, dst_value, location))?
signed_to_felt252_repr(context, entry, location, dst_value)?
} else {
dst_value
};

helper.br(entry, 0, &[dst_value], location)
}

/// Converts a value from the two's complement signed representation into the
/// canonical felt252 representation: `negative = P - absolute`.
fn signed_to_felt252_repr<'ctx, 'this>(
context: &'ctx Context,
entry: &'this Block<'ctx>,
location: Location<'ctx>,
value: Value<'ctx, 'this>,
) -> Result<Value<'ctx, 'this>> {
let k0 = entry.const_int_from_type(context, location, 0, value.r#type())?;
let is_negative = entry.cmpi(context, CmpiPredicate::Slt, value, k0, location)?;

let k_prime = entry.const_int_from_type(context, location, PRIME.clone(), value.r#type())?;
let adj_value = entry.addi(value, k_prime, location)?;

Ok(entry.append_op_result(arith::select(is_negative, adj_value, value, location))?)
}

#[cfg(test)]
mod test {
use crate::{
Expand Down
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