Technology

This chapter summarizes the current rWASM technology model as implemented in fluentlabs-xyz/rwasm.

High-level pipeline

rWASM uses a clear execution pipeline:

1. Input Wasm module
2. Parser + validator
3. rWASM translator/compiler
4. Compact rWASM module artifact
5. Execution strategy (native rWASM VM, plus optional compatibility strategy)

Core subsystems

Compiler / translator

The compiler layer parses and validates Wasm, then rewrites execution into the rWASM-oriented opcode stream and metadata layout.

Module model

rWASM modules are serialized as explicit runtime artifacts consumed by the VM. Current format includes a fixed header/magic + ordered sections (code/data/element/hints and source metadata).

Opcode model

The opcode surface is explicitly defined and version-sensitive.

Important operational rule:

• opcode ordering and module encoding are wire-compatibility concerns,
• changing them is a format-level change, not a cosmetic refactor.

Runtime VM

The native VM is a stack-machine executor with:

• value/call stack transitions,
• memory/table/global handling,
• trap model,
• host import linkage,
• resumable context hooks.

Strategy abstraction

rWASM supports a strategy layer so native execution and compatibility/comparison backends can be selected by feature/runtime setup.

Fuel and metering

Fuel is a first-class runtime primitive:

• bounded mode: deterministic out-of-fuel traps,
• unbounded mode: for controlled/testing contexts,
• reset/remaining behavior exposed by runtime store interfaces.

Fuel is consumed by both instruction paths and host-mediated operations depending on integration policy.

Tracing and observability

With tracing enabled, runtime emits instruction/memory/table-oriented execution traces for debugging and analysis.

This is useful for:

• differential checks,
• profiling,
• proving/debug instrumentation.

Feature-gated runtime surface

rWASM behavior depends on enabled features (std, wasmtime, fpu, tracing, etc.). Feature combinations are part of the effective runtime surface and should be pinned in production builds.

Security posture (architecture level)

Current rWASM docs emphasize:

• validation-first execution,
• fail-safe traps and bounds checks,
• host boundary determinism requirements,
• DoS controls via size/fuel/resource policies.

In practice, VM determinism and host determinism are both required. A deterministic VM with nondeterministic host imports is still nondeterministic at system level.

Implementation references

For exact, current behavior see:

• rwasm/docs/architecture.md
• rwasm/docs/pipeline.md
• rwasm/docs/module-format.md
• rwasm/docs/vm-and-fuel.md
• rwasm/docs/opcodes.md
• rwasm/docs/security-considerations.md