Xcode Compile Profiler

Use when compile time, type checking, or mixed-language compilation is the bottleneck. Recommend first; do not edit source or build settings without explicit approval.

Rules

• Start from .build-benchmark/ artifacts or raw build timing output.
• Prefer ad hoc diagnostic flags over persistent project edits.
• Rank by expected wall-clock impact, not cumulative parallel compiler work.
• If compile work is parallelized, label improvements as "Reduces compiler workload (parallel)" unless wait time should drop.
• Separate code-level, project-level, and module-level recommendations.

Inspect

• clean and incremental Build Timing Summary
• long CompileSwiftSources, per-file compile tasks, SwiftEmitModule, and Planning Swift module
• mixed Swift/Objective-C boundaries, bridging headers, generated Swift-to-ObjC surfaces
• diagnostics:
• -Xfrontend -warn-long-expression-type-checking=<ms>
• -Xfrontend -warn-long-function-bodies=<ms>
• -Xfrontend -debug-time-compilation
• -Xfrontend -debug-time-function-bodies
• -Xswiftc -driver-time-compilation
• -Xfrontend -stats-output-dir <path>

Preferred script:

python3 ../../shared/build-optimization/scripts/diagnose_compilation.py \
  --project App.xcodeproj \
  --scheme MyApp \
  --configuration Debug \
  --destination "platform=iOS Simulator,name=<latest available iPhone simulator>,OS=latest" \
  --threshold 100 \
  --output-dir .build-benchmark

Checks

Look first for missing explicit types in expensive expressions, deeply chained expressions, delegates typed as AnyObject, oversized bridging surfaces, unqualified header imports, non-final classes, broad public/open symbols, monolithic SwiftUI body, and closures without helpful type annotations.

Output

For each recommendation include evidence, file/module, expected wait-time impact or parallel-work caveat, confidence, and whether approval is needed. If evidence points to project configuration, read and hand off to xcode-project-auditor.

Resources

• references/code-compilation-checks.md
• ../../shared/build-optimization/references/recommendation-format.md
• ../../shared/build-optimization/references/build-optimization-sources.md