JDK-8366111 : Look into Clang -ftime-trace output
  • Type: Enhancement
  • Component: hotspot
  • Sub-Component: other
  • Priority: P4
  • Status: New
  • Resolution: Unresolved
  • Submitted: 2025-08-25
  • Updated: 2025-08-25
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Other
tbdUnresolved
Related Reports
Relates :  
JDK-8365053 - Refresh hotspot precompiled.hpp with headers based on current frequency
Description
Clang provides some options to investigate compilation time. See "shenandoahOldGC.json" for an example. 

ClangBuildAnalyzer allows aggregating this data and extracting human-readable information from it. I attached an example output to this ticket (clang_build_analyzer.txt).

In JDK-8365053 I investigated the "Expensive headers" section. Other sections may be interesting to explore too to reduce build time.

**** Templates that took longest to instantiate:
 45007 ms: AccessInternal::OopLoadProxy<oopDesc *, 524288>::operator oopDesc * (1232 times, avg 36 ms)
 44433 ms: AccessInternal::load<524292UL, oopDesc *, oopDesc *> (1232 times, avg 36 ms)

**** Template sets that took longest to instantiate:
371271 ms: AccessInternal::BarrierResolver<$>::resolve_barrier (24728 times, avg 15 ms)
370278 ms: AccessInternal::BarrierResolver<$>::resolve_barrier_rt (24728 times, avg 14 ms)

**** Functions that took longest to compile:
  2550 ms: State::MachNodeGenerator(int) (/jdk/build/trace/hotspot/variant-server/gensrc/adfiles/ad_x86_gen.cpp)
  2539 ms: CompilerToVM::initialize_intrinsics(JVMCIEnv*) (/jdk/src/hotspot/share/jvmci/jvmciCompilerToVMInit.cpp)

References:
- https://clang.llvm.org/docs/analyzer/developer-docs/PerformanceInvestigation.html
- https://github.com/aras-p/ClangBuildAnalyzer