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use super::{op_flags::OpFlags, EvaluationFrame, Vec};
use crate::{
stack::EvaluationFrameExt,
utils::{are_equal, binary_not},
};
use vm_core::FieldElement;
use winter_air::TransitionConstraintDegree;
#[cfg(test)]
pub mod tests;
// CONSTANTS
// ================================================================================================
/// The number of unique transition constraints in stack manipulation operations.
pub const NUM_CONSTRAINTS: usize = 49;
/// The degrees of constraints in individual stack manipulation operations.
pub const CONSTRAINT_DEGREES: [usize; NUM_CONSTRAINTS] = [
// Given it is a degree 7 operation, 7 is added to all the individual constraints
// degree.
8, // 1 constraint for PAD operation
8, 8, 8, 7, 7, 8, 7, 8, 8, 8, 8, 8, 8, // 13 constraints for DUPn and MOVUPn operations
8, 8, // 2 constraints in SWAP operations
8, 8, 8, 8, 8, 8, 8,
8, // 8 constraints for SWAPWX operations including 8 constraints of SWAPDW operation
8, 8, 8, 8, 8, 8, 8, 8, // 8 constraints for SWAPDW operations
8, 8, 8, 8, 8, 8, 8, // 7 constraints for MOVDNn operations
9, 9, 9, 9, 9, 9, 9, 9, 9, 9, // 10 constraints for CSWAP and CSWAPW operations
];
// STACK MANIPULATION OPERATIONS TRANSITION CONSTRAINTS
// ================================================================================================
/// Builds the transition constraint degrees for the stack manipulation operations.
pub fn get_transition_constraint_degrees() -> Vec<TransitionConstraintDegree> {
CONSTRAINT_DEGREES
.iter()
.map(|°ree| TransitionConstraintDegree::new(degree))
.collect()
}
/// Returns the number of transition constraints for the stack manipulation operations.
pub fn get_transition_constraint_count() -> usize {
NUM_CONSTRAINTS
}
/// Enforces constraints for the stack manipulation operations.
pub fn enforce_constraints<E: FieldElement>(
frame: &EvaluationFrame<E>,
result: &mut [E],
op_flag: &OpFlags<E>,
) -> usize {
let mut index = 0;
// Enforce constaints of the PAD operations.
index += enforce_pad_constraints(frame, result, op_flag.pad());
// Enforce constaints of the DUP(n) and MOVUP(n) operations.
index += enforce_dup_movup_n_constraints(frame, &mut result[index..], op_flag);
// Enforce constaints of the SWAP operations.
index += enforce_swap_constraints(frame, &mut result[index..], op_flag.swap());
// Enforce constaints of all the SWAP{W, W2, W3, DW} operations.
index += enforce_swapwx_constraints(frame, &mut result[index..], op_flag);
// Enforce constaints of the MOVDN(n) operations.
index += enforce_movdnn_constraints(frame, &mut result[index..], op_flag);
// Enforce constaints of the CSWAP and CSWAPW operations.
index += enforce_cswapx_constraints(frame, &mut result[index..], op_flag);
index
}
// TRANSITION CONSTRAINT HELPERS
// ================================================================================================
/// Enforces constraints of the PAD operation. The PAD operation pushes a ZERO onto
/// the stack. Therefore, the following constraints are enforced:
/// - The top element in the next frame should be ZERO. s0` = 0.
pub fn enforce_pad_constraints<E: FieldElement>(
frame: &EvaluationFrame<E>,
result: &mut [E],
op_flag: E,
) -> usize {
// Enforces the top element in the next frame is ZERO.
result[0] = op_flag * are_equal(frame.stack_item_next(0), E::ZERO);
1
}
/// Enforces constraints of the DUPn and MOVUPn operations. The DUPn operation copies the element
/// at depth n in the stack and pushes the copy onto the stack, whereas MOVUPn opearation moves the
/// element at depth n to the top of the stack. Therefore, the following constraints are enforced:
/// - The top element in the next frame should be equal to the element at depth n in the
/// current frame. s0` - sn = 0.
pub fn enforce_dup_movup_n_constraints<E: FieldElement>(
frame: &EvaluationFrame<E>,
result: &mut [E],
op_flag: &OpFlags<E>,
) -> usize {
// combined flag of respective movupn and dupn operation.
let dup_movup_2 = op_flag.movup2() + op_flag.dup2();
let dup_movup_3 = op_flag.movup3() + op_flag.dup3();
let dup_movup_4 = op_flag.movup4() + op_flag.dup4();
let dup_movup_5 = op_flag.movup5() + op_flag.dup5();
let dup_movup_6 = op_flag.movup6() + op_flag.dup6();
let dup_movup_7 = op_flag.movup7() + op_flag.dup7();
// Enforces the top element in the next frame is equal to the 1st element in the current
// frame.
result[0] = op_flag.dup() * are_equal(frame.stack_item_next(0), frame.stack_item(0));
// Enforces the top element in the next frame is equal to the 2nd element in the current
// frame.
result[1] = op_flag.dup1() * are_equal(frame.stack_item_next(0), frame.stack_item(1));
// Enforces the top element in the next frame is equal to the 3rd element in the current
// frame.
result[2] = dup_movup_2 * are_equal(frame.stack_item_next(0), frame.stack_item(2));
// Enforces the top element in the next frame is equal to the 4th element in the current
// frame.
result[3] = dup_movup_3 * are_equal(frame.stack_item_next(0), frame.stack_item(3));
// Enforces the top element in the next frame is equal to the 5th element in the current
// frame.
result[4] = dup_movup_4 * are_equal(frame.stack_item_next(0), frame.stack_item(4));
// Enforces the top element in the next frame is equal to the 6th element in the current
// frame.
result[5] = dup_movup_5 * are_equal(frame.stack_item_next(0), frame.stack_item(5));
// Enforces the top element in the next frame is equal to the 7th element in the current
// frame.
result[6] = dup_movup_6 * are_equal(frame.stack_item_next(0), frame.stack_item(6));
// Enforces the top element in the next frame is equal to the 8th element in the current
// frame.
result[7] = dup_movup_7 * are_equal(frame.stack_item_next(0), frame.stack_item(7));
// Enforces the top element in the next frame is equal to the 8th element in the current
// frame.
result[8] = op_flag.movup8() * are_equal(frame.stack_item_next(0), frame.stack_item(8));
// Enforces the top element in the next frame is equal to the 10th element in the current
// frame.
result[9] = op_flag.dup9() * are_equal(frame.stack_item_next(0), frame.stack_item(9));
// Enforces the top element in the next frame is equal to the 12th element in the current
// frame.
result[10] = op_flag.dup11() * are_equal(frame.stack_item_next(0), frame.stack_item(11));
// Enforces the top element in the next frame is equal to the 14th element in the current
// frame.
result[11] = op_flag.dup13() * are_equal(frame.stack_item_next(0), frame.stack_item(13));
// Enforces the top element in the next frame is equal to the 16th element in the current
// frame.
result[12] = op_flag.dup15() * are_equal(frame.stack_item_next(0), frame.stack_item(15));
13
}
/// Enforces constraints of the SWAP operation. The SWAP operation swaps the first
/// two elements in the stack. Therefore, the following constraints are enforced:
/// - The first element in the current frame should be equal to the second element in the
/// next frame.
/// - The second element in the current frame should be equal to the first element in the
/// next frame.
pub fn enforce_swap_constraints<E: FieldElement>(
frame: &EvaluationFrame<E>,
result: &mut [E],
op_flag: E,
) -> usize {
// Enforces the first element in the current frame is same as to the second element in the
// next frame.
result[0] = op_flag * are_equal(frame.stack_item(0), frame.stack_item_next(1));
// Enforces the second element in the current frame is same as to the first element in the
// next frame.
result[1] = op_flag * are_equal(frame.stack_item(1), frame.stack_item_next(0));
2
}
/// Enforces constraints of all the SWAP{W, W2, W3, DW} operations. Each of the operation
/// effects the stack in the following way:
/// - The SWAPW operation swaps the elements 0,1,2,3 with 4,5,6,7 in the stack.
/// - The SWAPW2 operation swaps the elements 0,1,2,3 with 8,9,10,11 in the stack.
/// - The SWAPW3 operation swaps the elements 0,1,2,3 with 12,13,14,15 in the stack.
/// - The SWAPDW operation swaps the elements 0,1,2,3,4,5,6,7 with 8,9,10,11,12,13,14,15
/// in the stack.
///
/// Therefore, the following constraints are enforced:
/// - During any frame, only one of these operation can be present (it is possible that
/// none of these operations are present), therefore, the respective stack item can only
/// transition into certain state and we can use this to combine these transition into
/// one constraints where each transition are weighted by their respective flag. for eg.
/// in the case of SWAPW3 the first item of the stack gets replaced with the 12 items and
/// vice versa, therefore, only SWAPW3 transition will be ONE and rest all flags would be
/// ZERO.
#[allow(clippy::needless_range_loop)]
pub fn enforce_swapwx_constraints<E: FieldElement>(
frame: &EvaluationFrame<E>,
result: &mut [E],
op_flag: &OpFlags<E>,
) -> usize {
let swapw_or_swapw3 = op_flag.swapw() + op_flag.swapw3();
let swapw2_or_swapdw = op_flag.swapw2() + op_flag.swapdw();
let swapwx = swapw_or_swapw3 + swapw2_or_swapdw;
// enforce that the first four element in the stack have transitioned correctly.
for i in 0..4 {
let next_item = op_flag.swapw() * frame.stack_item_next(i + 4)
+ swapw2_or_swapdw * frame.stack_item_next(i + 8)
+ op_flag.swapw3() * frame.stack_item_next(i + 12);
result[i] = are_equal(next_item, frame.stack_item(i) * swapwx);
}
// enforce that the transition into the first four elements in the next frame are done
// correctly.
for i in 0..4 {
let current_item = op_flag.swapw() * frame.stack_item(i + 4)
+ swapw2_or_swapdw * frame.stack_item(i + 8)
+ op_flag.swapw3() * frame.stack_item(i + 12);
result[i + 4] = are_equal(current_item, frame.stack_item_next(i) * swapwx);
}
// enforce that stack items 4,5,6,7 are swapped correctly.
for i in 0..4 {
result[i + 8] =
op_flag.swapdw() * are_equal(frame.stack_item(i + 4), frame.stack_item_next(i + 12));
}
// enforce that stack items 12,13,14,15 are swapped correctly.
for i in 0..4 {
result[i + 12] =
op_flag.swapdw() * are_equal(frame.stack_item(i + 12), frame.stack_item_next(i + 4));
}
16
}
/// Enforces constraints of the MOVDNn operation. The MOVDNn operation moves the top element
/// to depth n in the stack. Therefore, the following constraints are enforced:
/// - The top element in the current frame should be equal to the element at depth n in the
/// next frame. s0 - sn` = 0.
pub fn enforce_movdnn_constraints<E: FieldElement>(
frame: &EvaluationFrame<E>,
result: &mut [E],
op_flag: &OpFlags<E>,
) -> usize {
// Enforces the top element in the current frame is equal to the nth element in the next
// frame.
result[0] = op_flag.movdn2() * are_equal(frame.stack_item(0), frame.stack_item_next(2));
result[1] = op_flag.movdn3() * are_equal(frame.stack_item(0), frame.stack_item_next(3));
result[2] = op_flag.movdn4() * are_equal(frame.stack_item(0), frame.stack_item_next(4));
result[3] = op_flag.movdn5() * are_equal(frame.stack_item(0), frame.stack_item_next(5));
result[4] = op_flag.movdn6() * are_equal(frame.stack_item(0), frame.stack_item_next(6));
result[5] = op_flag.movdn7() * are_equal(frame.stack_item(0), frame.stack_item_next(7));
result[6] = op_flag.movdn8() * are_equal(frame.stack_item(0), frame.stack_item_next(8));
7
}
/// Enforces constraints of the CSWAP and CSWAPW operation. Each of the operation effects
/// the stack in the following way:
/// - The top element in the stack should be binary and is enforced as a general constraint.
/// - The CSWAP operation swaps the elements 1,2 in the stack if the first element is 1. The stack
/// remains the same if the top element is 0.
/// - The CSWAP operation swaps the elements 1,2,3,4 with 5,6,7,8 in the stack if the first element
/// is 1. The stack remains the same if the top element is 0.
///
/// Therefore, the following constraints are enforced:
/// - The top two elements or elements 1,2,3,4 should be swapped in the case of CSWAP and
/// CSWAPW respectively if the top element is 1, the state remains the same if the top
/// element is 0.
#[allow(clippy::needless_range_loop)]
pub fn enforce_cswapx_constraints<E: FieldElement>(
frame: &EvaluationFrame<E>,
result: &mut [E],
op_flag: &OpFlags<E>,
) -> usize {
// condition should be binary and is enforced as a general constraint. It is used to
// decide if the respective elements/words needs to be swapped or not.
let condition = frame.stack_item(0);
let not_condition = binary_not(frame.stack_item(0));
let a = frame.stack_item(1);
let b = frame.stack_item(2);
let c = frame.stack_item_next(0);
let d = frame.stack_item_next(1);
// Enforces that b is moved to the top of the stack if the condition is 1 else a is
// moved to the top.
result[0] = op_flag.cswap() * are_equal(c, a * not_condition + b * condition);
// Enforces that b is at depth 2 in the stack if the condition is 0 else a should be
// at depth 2.
result[1] = op_flag.cswap() * are_equal(d, a * condition + b * not_condition);
// Enforces the correct transition of a and b into item at index 0,1,2,3 in the next frame.
for i in 0..4 {
let a = frame.stack_item(i + 1);
let b = frame.stack_item(i + 5);
let c = frame.stack_item_next(i);
result[i + 2] = op_flag.cswapw() * are_equal(c, a * not_condition + b * condition);
}
// Enforces the correct transition of a and b into item at index 4,5,6,7 in the next frame.
for i in 0..4 {
let a = frame.stack_item(i + 1);
let b = frame.stack_item(i + 5);
let c = frame.stack_item_next(i + 4);
result[i + 6] = op_flag.cswapw() * are_equal(c, a * condition + b * not_condition);
}
10
}