| Issue |
180871
|
| Summary |
[LifetimeSafety] Build time regression (mid-single-digit)
|
| Labels |
clang:temporal-safety
|
| Assignees |
|
| Reporter |
emaxx-google
|
Adding `-Wlifetime-safety` causes a 4.5% build performance hit (~1 sec on a sample builder) on the following file from V8: https://source.chromium.org/chromium/chromium/src/+/main:v8/src/compiler/turboshaft/csa-branch-elimination-phase.cc;drc=f2d33c2193fc819b5b92f284fc7f84b37db0ee87 (with extra lifetime annotations added).
Excerpt from `perf diff` between the profiles recorded via `perf record -g` for `-Wno-lifetime-safety` and `-Wlifetime-safety`:
```
# Event 'cycles:Pu'
#
# Baseline Delta Abs Shared Object Symbol
# ........ ......... .................... ...........................................................................................................................................................
#
+0.30% clang-23 [.] clang::lifetimes::internal::LoanPropagationAnalysis::LoanPropagationAnalysis(clang::CFG const&, clang::AnalysisDeclContext&, clang::lifetimes::internal
0.79% +0.22% libc.so.6 [.] _int_malloc
+0.17% clang-23 [.] clang::lifetimes::internal::LiveOriginsAnalysis::LiveOriginsAnalysis(clang::CFG const&, clang::AnalysisDeclContext&, clang::lifetimes::internal::FactMa
+0.14% clang-23 [.] llvm::DenseMap<clang::CFGBlock const*, clang::lifetimes::internal::(anonymous namespace)::Lattice, llvm::DenseMapInfo<clang::CFGBlock const*, void>, ll
0.44% -0.12% clang-23 [.] clang::CodeGen::CodeGenModule::EmitGlobal(clang::GlobalDecl)
0.64% +0.12% libc.so.6 [.] cfree@GLIBC_2.2.5
0.49% -0.11% clang-23 [.] clang::RecordDecl::field_begin() const
0.56% -0.11% clang-23 [.] clang::TypeLoc::getFullDataSizeForType(clang::QualType)
+0.11% clang-23 [.] clang::lifetimes::internal::OriginManager::getOrCreateList(clang::Expr const*)
0.00% +0.11% clang-23 [.] clang::lifetimes::isGslPointerType(clang::QualType)
0.83% +0.10% libc.so.6 [.] malloc
+0.09% clang-23 [.] llvm::ImutAVLTree<llvm::ImutKeyValueInfo<clang::lifetimes::internal::utils::ID<clang::lifetimes::internal::OriginTag>, llvm::ImmutableSet<clang::lifeti
+0.09% clang-23 [.] clang::lifetimes::internal::FactsGenerator::run()
1.39% -0.09% clang-23 [.] clang::Sema::CheckTemplateArgumentList(clang::TemplateDecl*, clang::SourceLocation, clang::TemplateArgumentListInfo&, clang::DefaultArguments const&, b
3.12% -0.08% clang-23 [.] llvm::FoldingSetBase::FindNodeOrInsertPos(llvm::FoldingSetNodeID const&, void*&, llvm::FoldingSetBase::FoldingSetInfo const&)
+0.08% clang-23 [.] clang::StmtVisitorBase<llvm::make_const_ptr, clang::lifetimes::internal::FactsGenerator, void>::Visit(clang::Stmt const*)
1.02% -0.08% clang-23 [.] clang::FunctionProtoType::Profile(llvm::FoldingSetNodeID&, clang::ASTContext const&)
```
I won't attach the artifacts on the bug publicly, but some stats for the preprocessed file: 20MB, ~3'000 `[[clang::lifetimebound]]` annotations, ~50 `[[gsl::Owner]]`s, ~90 `[[gsl::Pointer]]`s.
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