alexfh wrote:
Well, actually it's not a 5x increase, it's an increase from ~7s to "I got bored to wait" minutes (thus, either a superlinear from code size or an infinite loop). I ran clang under `perf`, and it seems to spend a lot of time in:
```
__libc_start_main ▒ main ▒ clang_main(int, char**, llvm::ToolContext const&) ▒ clang::driver::Driver::ExecuteCompilation(clang::driver::Compilation&, llvm::SmallVectorImpl<std::__u::pair<int, clang::driver::Command const*> >&) ▒ clang::driver::Compilation::ExecuteJobs(clang::driver::JobList const&, llvm::SmallVectorImpl<std::__u::pair<int, clang::driver::Command const*> >&, bool) const ▒ clang::driver::Compilation::ExecuteCommand(clang::driver::Command const&, clang::driver::Command const*&, bool) const ▒ clang::driver::CC1Command::Execute(llvm::ArrayRef<std::__u::optional<llvm::StringRef> >, std::__u::basic_string<char, std::__u::char_traits<char>, std::__u::allocator<char> >*, bool*) const ▒ llvm::CrashRecoveryContext::RunSafely(llvm::function_ref<void ()>) ▒ void llvm::function_ref<void ()>::callback_fn<clang::driver::CC1Command::Execute(llvm::ArrayRef<std::__u::optional<llvm::StringRef> >, std::__u::basic_string<char, std::__u::char_traits<char>, std::__u::allocator<char> >*, bool*) const:▒ ExecuteCC1Tool(llvm::SmallVectorImpl<char const*>&, llvm::ToolContext const&) ▒ cc1_main(llvm::ArrayRef<char const*>, char const*, void*) ▒ clang::ExecuteCompilerInvocation(clang::CompilerInstance*) ▒ clang::CompilerInstance::ExecuteAction(clang::FrontendAction&) ▒ clang::FrontendAction::Execute() ▒
clang::ParseAST(clang::Sema&, bool, bool) ▒
clang::BackendConsumer::HandleTranslationUnit(clang::ASTContext&) ▒
clang::EmitBackendOutput(clang::DiagnosticsEngine&, clang::HeaderSearchOptions const&, clang::CodeGenOptions const&, clang::TargetOptions const&, clang::LangOptions const&, llvm::StringRef, llvm::Module*, clang::BackendAction, llvm::Int▒
llvm::legacy::PassManagerImpl::run(llvm::Module&) ▒
llvm::FPPassManager::runOnModule(llvm::Module&) ▒
llvm::FPPassManager::runOnFunction(llvm::Function&) ▒
- llvm::MachineFunctionPass::runOnFunction(llvm::Function&) ▒
- 45.61% (anonymous namespace)::TailDuplicateBase::runOnMachineFunction(llvm::MachineFunction&) ▒
llvm::TailDuplicator::tailDuplicateBlocks() ▒
llvm::TailDuplicator::shouldTailDuplicate(bool, llvm::MachineBasicBlock&) ▒
```
https://github.com/llvm/llvm-project/pull/79993