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name: tracing-inlining-decisions description: Shows inlining decisions during compilation with call tree and reasons for inline/don't-inline. Use to verify critical calls are inlined, understand why inlining failed (too large, recursive, boundary), and optimize method sizes. Good inlining = better compilation. Recursive functions show 'not inlined' - expected behavior for Bytecode DSL limitation.

Tracing Inlining Decisions

Shows inlining decisions during compilation with call tree structure and reasons. Essential for understanding why calls aren't being optimized.

When to Use This Skill

• Verify critical calls are being inlined
• Understand why inlining failed
• Optimize method sizes for better inlining
• Debug recursive function compilation

Quick Start

Copy# Basic inlining trace
<launcher> --experimental-options \
  --engine.TraceInlining <program>

# Combined with compilation trace (RECOMMENDED)
<launcher> --experimental-options \
  --engine.TraceInlining \
  --engine.TraceCompilation \
  <program> 2>&1 | tee inlining.log

# Focus on specific function
<launcher> --experimental-options \
  --engine.TraceInlining \
  --engine.CompileOnly="*hotFunction*" \
  <program>

⚠️ REQUIRED: Fermi Verification (Every Tool Invocation)

Before running:

• Pre-calculate: Expected hot helper functions to inline (list 2-5 function names)
• Smoke test: <launcher> --experimental-options --engine.TraceInlining -c 'print 1;' → Verify inlining decisions appear

After running:

• Validate: Critical functions inlined as expected? YES / NO
• If NO: Document why (budgetExhausted, TooLarge, TruffleBoundary)
• Save output: tool-outputs/trace-inlining-[benchmark].txt

Gate: All boxes checked? → Proceed to analysis

Key Options

Understanding Output

Inlined Successfully

Copy[engine] Inlined: hasConflict
  Reason: trivialSize

Not Inlined

Copy[engine] Not inlined: recursiveFunc
  Reason: RecursiveInlining

Copy[engine] Not inlined: bigFunction
  Reason: budgetExhausted

Inlining Reasons

Good (Inlined)

Bad (Not Inlined)

Problem Patterns

Pattern 1: Budget Exhausted for Hot Functions

Symptom: Critical function not inlined due to budget Fix: Reduce sizes of other methods, or increase budget

Pattern 2: Unexpected Boundary

Symptom: Hot call not inlined due to TruffleBoundary Fix: Remove boundary if not needed, or restructure

Pattern 3: Too Many Recursive Levels

Symptom: Recursive function shows "RecursiveInlining" Expected: Normal for recursive algorithms (Bytecode DSL limitation)

Integration with Other Skills

Related Skills

• profiling-with-cpu-sampler - Identify hot functions first
• tracing-compilation-events - Overall compilation status
• detecting-performance-warnings - Find barriers
• fetching-truffle-documentation - API reference

Reference

Copy<launcher> --help:engine | grep -i inlin