Adding support to felt add mul and sub in constant propogation

[eytan-starkware]

Added constant folding for felt252 arithmetic operations (add, sub, mul) to improve compiler optimization.

What changed?

• Implemented constant folding for felt252_add and felt252_mul operations
• Enhanced the existing felt252_sub constant folding to handle more cases
• Added utility functions undet utils crate in bigint.rs to support felt252 modular arithmetic:
  • Added CAIRO_PRIME_BIGINT as a static constant
  • Added felt252_mod() function to handle modular arithmetic properly
• Added test cases to verify the constant folding behavior for all operations
• Updated existing test files to reflect the new optimized output

[reviewable-StarkWare]

This change is 

[eytan-starkware]

• (optimization): felt252_div constant propogation support #8604
• Adding support to felt add mul and sub in constant propogation #8594 👈 (View in Graphite)
• main

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[orizi]

Reviewable status: 0 of 13 files reviewed, 1 unresolved discussion (waiting on @ilyalesokhin-starkware and @TomerStarkware)

---

crates/cairo-lang-lowering/src/lower/test_data/closure line 361 at r1 (raw file):

  Return()

blk2:

add calls to some inline function to keep the test with meaning.

Code quote:

  (v1: core::felt252) <- 1
  (v2: core::felt252) <- 2
  (v3: core::felt252) <- core::felt252_sub(v1, v2)
End:
  Match(match core::felt252_is_zero(v3) {
    IsZeroResult::Zero => blk1,
    IsZeroResult::NonZero(v4) => blk2,
  })

blk1:
Statements:
End:
  Return()

blk2:

[eytan-starkware]

Reviewable status: 0 of 13 files reviewed, 1 unresolved discussion (waiting on @ilyalesokhin-starkware, @orizi, and @TomerStarkware)

---

crates/cairo-lang-lowering/src/lower/test_data/closure line 361 at r1 (raw file):

Previously, orizi wrote…

add calls to some inline function to keep the test with meaning.

Done.

[eytan-starkware]

Reviewable status: 0 of 13 files reviewed, 1 unresolved discussion (waiting on @ilyalesokhin-starkware, @orizi, and @TomerStarkware)

---

crates/cairo-lang-lowering/src/lower/test_data/closure line 361 at r1 (raw file):

Previously, eytan-starkware wrote…

Done.

I used a non-inline function to get the generated code be similar to original one (inline functions would generally get constant propagation activated and back to square one)

[orizi]

@orizi reviewed 6 of 13 files at r1, 5 of 6 files at r2, all commit messages.
Reviewable status: 11 of 13 files reviewed, 5 unresolved discussions (waiting on @ilyalesokhin-starkware and @TomerStarkware)

---

crates/cairo-lang-lowering/src/optimizations/test_data/const_folding line 59 at r2 (raw file):

//! > module_code
const Pm1: felt252 = 0x800000000000011000000000000000000000000000000000000000000000000;

is this PRIME_MINUS_1?

Suggestion:

const PRIME_MINUS_1: felt252 = -1;

---

crates/cairo-lang-lowering/src/test_data/tests line 178 at r2 (raw file):

        x;
    }
    let _y = if 1 == 1 {

prevent test degragation.

---

crates/cairo-lang-utils/src/bigint.rs line 248 at r2 (raw file):

/// The Cairo prime as a BigInt.
#[cfg(feature = "std")]
pub static CAIRO_PRIME_BIGINT: LazyLock<BigInt> = LazyLock::new(|| {

do in another PR and use everywhere.

also - possibly just direct usage of Felt252 type should be enough.

---

crates/cairo-lang-lowering/src/optimizations/const_folding.rs line 513 at r2 (raw file):

            if let (Some(lhs), Some(rhs)) =
                (self.as_int(stmt.inputs[0].var_id), self.as_int(stmt.inputs[1].var_id))
            {

if any is known to be 0 - just return the other - same as the felt_sub.

Code quote:

            if let (Some(lhs), Some(rhs)) =
                (self.as_int(stmt.inputs[0].var_id), self.as_int(stmt.inputs[1].var_id))
            {

---

crates/cairo-lang-lowering/src/optimizations/const_folding.rs line 525 at r2 (raw file):

            {
                return Some(self.propagate_zero_and_get_statement(stmt.outputs[0]));
            }

if any is one return the other - same as felt_sub.

[eytan-starkware]

Reviewable status: 7 of 17 files reviewed, 5 unresolved discussions (waiting on @ilyalesokhin-starkware, @orizi, and @TomerStarkware)

---

crates/cairo-lang-lowering/src/optimizations/const_folding.rs line 513 at r2 (raw file):

Previously, orizi wrote…

if any is known to be 0 - just return the other - same as the felt_sub.

Done.

---

crates/cairo-lang-lowering/src/optimizations/const_folding.rs line 525 at r2 (raw file):

Previously, orizi wrote…

if any is one return the other - same as felt_sub.

Done.

---

crates/cairo-lang-lowering/src/optimizations/test_data/const_folding line 59 at r2 (raw file):

Previously, orizi wrote…

is this PRIME_MINUS_1?

Done.

---

crates/cairo-lang-lowering/src/test_data/tests line 178 at r2 (raw file):

Previously, orizi wrote…

prevent test degragation.

Done.

---

crates/cairo-lang-utils/src/bigint.rs line 248 at r2 (raw file):

Previously, orizi wrote…

do in another PR and use everywhere.

also - possibly just direct usage of Felt252 type should be enough.

Just moved to wrapping values with felt, which will later provide a div operator as well

[orizi]

@orizi reviewed 6 of 9 files at r3, all commit messages.
Reviewable status: 13 of 17 files reviewed, 10 unresolved discussions (waiting on @eytan-starkware, @ilyalesokhin-starkware, and @TomerStarkware)

---

crates/cairo-lang-lowering/src/optimizations/test_data/const_folding line 59 at r2 (raw file):

Previously, eytan-starkware wrote…

Done.

no it isn't.

---

crates/cairo-lang-utils/src/lib.rs line 34 at r3 (raw file):

pub mod unordered_hash_set;

pub use starknet_types_core::felt::Felt as Felt252;

revert.
use directly where-ever needed.

---

crates/cairo-lang-lowering/src/optimizations/const_folding.rs line 511 at r3 (raw file):

                    stmt.outputs[0],
                    false,
                ));

Suggestion:

                let value = Felt252::from(lhs - rhs).to_bigint();
                return Some(self.propagate_const_and_get_statement(
                    value,
                    stmt.outputs[0],
                    false,
                ));

---

crates/cairo-lang-lowering/src/optimizations/const_folding.rs line 529 at r3 (raw file):

            if let (Some(lhs), Some(rhs)) =
                (self.as_int(stmt.inputs[0].var_id), self.as_int(stmt.inputs[1].var_id))
            {

Suggestion:

        } else if id == self.felt_add {
            if let Some(lhs) = self.as_int(stmt.inputs[0].var_id)
                && lhs.is_zero()
            {
                self.var_info.insert(stmt.outputs[0], VarInfo::Var(stmt.inputs[1]));
            } else if let Some(rhs) = self.as_int(stmt.inputs[1].var_id)
                && rhs.is_zero()
            {
                self.var_info.insert(stmt.outputs[0], VarInfo::Var(stmt.inputs[0]));
            } else if let (Some(lhs), Some(rhs)) =
                (self.as_int(stmt.inputs[0].var_id), self.as_int(stmt.inputs[1].var_id))
            {

---

crates/cairo-lang-lowering/src/optimizations/const_folding.rs line 529 at r3 (raw file):

            if let (Some(lhs), Some(rhs)) =
                (self.as_int(stmt.inputs[0].var_id), self.as_int(stmt.inputs[1].var_id))
            {

Suggestion:

            if let Some(lhs) = self.as_int(stmt.inputs[0].var_id)
                && lhs.is_zero()
            {
                self.var_info.insert(stmt.outputs[0], VarInfo::Var(stmt.inputs[1]));
            } else if let Some(rhs) = self.as_int(stmt.inputs[1].var_id)
                && rhs.is_zero()
            {
                self.var_info.insert(stmt.outputs[0], VarInfo::Var(stmt.inputs[0]));
            } else if let (Some(lhs), Some(rhs)) =
                (self.as_int(stmt.inputs[0].var_id), self.as_int(stmt.inputs[1].var_id))
            {

---

crates/cairo-lang-lowering/src/optimizations/const_folding.rs line 535 at r3 (raw file):

                    stmt.outputs[0],
                    false,
                ));

Suggestion:

                let value = Felt252::from(lhs + rhs).to_bigint();
                return Some(self.propagate_const_and_get_statement(
                    value,
                    stmt.outputs[0],
                    false,
                ));

---

crates/cairo-lang-lowering/src/optimizations/const_folding.rs line 559 at r3 (raw file):

            }

            if let (Some((lhs_val, lhs_nz)), Some((rhs_val, rhs_nz))) = (lhs, rhs) {

Suggestion:

            if let Some(rhs) = self.as_int(stmt.inputs[1].var_id)
                && rhs.is_one()
            {
                self.var_info.insert(stmt.outputs[0], VarInfo::Var(stmt.inputs[0]));
            } else if let Some(lhs) = self.as_int(stmt.inputs[0].var_id)
                && lhs.is_one()
            {
                self.var_info.insert(stmt.outputs[0], VarInfo::Var(stmt.inputs[1]));
            } else if let (Some((lhs_val, lhs_nz)), Some((rhs_val, rhs_nz))) = (lhs, rhs) {

---

crates/cairo-lang-lowering/src/optimizations/const_folding.rs line 566 at r3 (raw file):

                    stmt.outputs[0],
                    nz_ty,
                ));

Suggestion:

                let value = Felt252::from(lhs_val * rhs_val).to_bigint();
                let nz_ty = lhs_nz && rhs_nz;
                return Some(self.propagate_const_and_get_statement(
                    value,
                    stmt.outputs[0],
                    nz_ty,
                ));

[eytan-starkware]

Reviewable status: 11 of 18 files reviewed, 10 unresolved discussions (waiting on @ilyalesokhin-starkware, @orizi, and @TomerStarkware)

---

crates/cairo-lang-lowering/src/optimizations/test_data/const_folding line 59 at r2 (raw file):

Previously, orizi wrote…

no it isn't.

Now in both locations. Note that it will write -1 in the lowering statements because we are using big ints for constants, and not the felt wrap around number. I think that it is fine though.

---

crates/cairo-lang-utils/src/lib.rs line 34 at r3 (raw file):

Previously, orizi wrote…

revert.
use directly where-ever needed.

Ok

---

crates/cairo-lang-lowering/src/optimizations/const_folding.rs line 511 at r3 (raw file):

                    stmt.outputs[0],
                    false,
                ));

Done.

---

crates/cairo-lang-lowering/src/optimizations/const_folding.rs line 529 at r3 (raw file):

            if let (Some(lhs), Some(rhs)) =
                (self.as_int(stmt.inputs[0].var_id), self.as_int(stmt.inputs[1].var_id))
            {

Done.

---

crates/cairo-lang-lowering/src/optimizations/const_folding.rs line 529 at r3 (raw file):

            if let (Some(lhs), Some(rhs)) =
                (self.as_int(stmt.inputs[0].var_id), self.as_int(stmt.inputs[1].var_id))
            {

Done.

---

crates/cairo-lang-lowering/src/optimizations/const_folding.rs line 535 at r3 (raw file):

                    stmt.outputs[0],
                    false,
                ));

Done.

---

crates/cairo-lang-lowering/src/optimizations/const_folding.rs line 559 at r3 (raw file):

            }

            if let (Some((lhs_val, lhs_nz)), Some((rhs_val, rhs_nz))) = (lhs, rhs) {

Done.

---

crates/cairo-lang-lowering/src/optimizations/const_folding.rs line 566 at r3 (raw file):

                    stmt.outputs[0],
                    nz_ty,
                ));

Done.

[orizi]

@orizi reviewed 7 of 7 files at r4, all commit messages.
Reviewable status: all files reviewed, 1 unresolved discussion (waiting on @ilyalesokhin-starkware and @TomerStarkware)

[orizi]

Reviewable status: complete! all files reviewed, all discussions resolved (waiting on @ilyalesokhin-starkware and @TomerStarkware)