Use Hint Bridge for Constraining HintLoad

[darth-cy]

• Add a LookupBus encapsulation to constrain the values loaded from hint_space.
• Change NativeSumcheck to use hint space loading by default. Make opcode's writeback operation optional to reduce cycles.

[Copilot]

Pull request overview

This PR introduces a new “hint bus/bridge” mechanism to constrain values read from hint_space, and updates Native sumcheck to source inputs from hint space by default with optional witness-array writeback.

Changes:

• Add HintBus/HintBridge to the system port and plumb it through circuit extensions.
• Update NativeSumcheck to always read prod/logup inputs from hint_space, make writeback optional, and add hint-bus lookups for those reads.
• Introduce a HintSpaceProvider AIR/chip intended to provide hint keys for the lookup table.

Reviewed changes

Copilot reviewed 22 out of 22 changed files in this pull request and generated 7 comments.

Show a summary per file

File	Description
extensions/sha256/circuit/src/sha256_chip/air.rs	Ignore new hint_bridge system port field.
extensions/rv32im/circuit/src/extension/mod.rs	Ignore new hint_bridge system port field in RV32 extensions.
extensions/native/circuit/src/sumcheck/execution.rs	Sumcheck executor now reads prod/logup evals from hint_space and gates writeback.
extensions/native/circuit/src/sumcheck/columns.rs	Replace is_hint_src_id with is_writeback + hint-id columns.
extensions/native/circuit/src/sumcheck/chip.rs	Tracegen updated for hint-space inputs, optional writeback, and hint-provider requests.
extensions/native/circuit/src/sumcheck/air.rs	Sumcheck AIR adds HintBridge lookups and optional writeback behavior.
extensions/native/circuit/src/poseidon2/air.rs	Plumb HintBridge into Native Poseidon2 AIR constructor/state.
extensions/native/circuit/src/lib.rs	Export new hint_space_provider module.
extensions/native/circuit/src/hint_space_provider.rs	New provider AIR/chip to supply (hint_id, offset, value) keys on the hint bus.
extensions/native/circuit/src/extension/mod.rs	Wire hint bridge/provider AIR + chip into Native extension (CPU).
extensions/keccak256/circuit/src/extension/mod.rs	Ignore new hint_bridge system port field.
extensions/ecc/circuit/src/extension/weierstrass.rs	Ignore new hint_bridge system port field.
extensions/bigint/circuit/src/extension/mod.rs	Ignore new hint_bridge system port field.
extensions/algebra/circuit/src/extension/modular.rs	Ignore new hint_bridge system port field.
extensions/algebra/circuit/src/extension/fp2.rs	Ignore new hint_bridge system port field.
crates/vm/src/system/mod.rs	Add HintBus/HintBridge to system config, inventory, and SystemPort.
crates/vm/src/system/memory/offline_checker/columns.rs	Add hint read/write aux column structs.
crates/vm/src/system/memory/offline_checker/bus.rs	Add HintBus wrapper over LookupBus.
crates/vm/src/system/memory/offline_checker/bridge.rs	Add HintBridge wrapper exposing lookup/provide API.
crates/vm/src/arch/testing/mod.rs	Reserve HINT_BUS bus index for tests.
crates/vm/src/arch/testing/cuda.rs	Add hint_bridge() and include it in SystemPort for GPU tests.
crates/vm/src/arch/testing/cpu.rs	Add hint bridge to SystemPort for CPU tests.

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[kunxian-xia]

You have to make sure that the tuple (hint_id, offset) is monotonically increasing s.t. two different lookups with key (hint_id, offset) will not return different value.

[darth-cy]

Monotonicity constraints are now available

[Copilot]

Pull request overview

Copilot reviewed 25 out of 26 changed files in this pull request and generated 3 comments.

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[kunxian-xia]

LGTM 🎉