[LLVMbugs] [Bug 11166] New: Lots of compile time spent in LazyValueInfo::eraseBlock

[bugzilla-daemon at llvm.org]

http://llvm.org/bugs/show_bug.cgi?id=11166

           Summary: Lots of compile time spent in
                    LazyValueInfo::eraseBlock
           Product: new-bugs
           Version: unspecified
          Platform: PC
        OS/Version: Linux
            Status: NEW
          Severity: normal
          Priority: P
         Component: new bugs
        AssignedTo: unassignedbugs at nondot.org
        ReportedBy: baldrick at free.fr
                CC: llvmbugs at cs.uiuc.edu


When compiling gcc-as-one-big-file at -O3, my profiler shows that most of the
compile time is spent in llvm::LazyValueInfo::eraseBlock:

     5.47%         llvm::LazyValueInfo::eraseBlock(llvm::BasicBlock*)
     3.43%         _int_malloc
     2.10%         llvm::Use::getImpliedUser() const
     1.51%         llvm::MachineInstr::addRegisterDead(unsigned int,
llvm::TargetRegisterInfo const*, bool)
...


Within LazyValueInfo::eraseBlock, most of the time is spent in this loop:

  for (DenseMap<LVIValueHandle, ValueCacheEntryTy>::iterator
       I = ValueCache.begin(), E = ValueCache.end(); I != E; ++I)
    I->second.erase(BB);

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