Module tier 

Tiered compilation support for Shape VM.

Functions start in Tier 0 (interpreted) and are promoted to JIT compilation tiers based on call frequency:

• Tier 0: Interpreted (all functions start here)
• Tier 1: Baseline JIT (per-function, no cross-function optimization) — after 100 calls
• Tier 2: Optimizing JIT (inlining, constant propagation) — after 10,000 calls

Structs

CompilationRequest

Request to compile a function at a higher tier.

CompilationResult

Result of background compilation.

FunctionTierState

Per-function call counter and tier tracking.

TierManager

Manages tiered compilation state for all functions in a program.

TierStats

Summary statistics for the tiered compilation system.

Enums

Tier

Execution tier for a function.

Traits

CompilationBackend

Backend trait for pluggable JIT compilation.