llvm dev - Aug 2010 - [LLVMdev] What is the meaning of addRegisterDead function

Now I am writing a simulator by llvm IR. That is really a wonderful
tools for us. Now I use gprof try to
find the bottleneck of the simulator, the output as the following. And
I found addRegisterDead of llvm
is called too much. What is the functionality of addRegisterDead?
 I try to understand it by reading the related code of llvm source but no idea.

  %   cumulative   self              self     total
 time   seconds   seconds    calls  Ts/call  Ts/call  name
  5.16      0.33     0.33
llvm::MachineInstr::addRegisterDead(unsigned int,
llvm::TargetRegisterInfo const*, bool)


Thanks in advance.

Michael.Kang


-- 
www.skyeye.org

On Aug 17, 2010, at 5:13 AM, Michael.Kang wrote:
> Now I am writing a simulator by llvm IR. That is really a wonderful
> tools for us. Now I use gprof try to
> find the bottleneck of the simulator, the output as the following. And
> I found addRegisterDead of llvm
> is called too much. What is the functionality of addRegisterDead?
It is called from the LiveVariables pass. It is the first part of register
allocation.

I think this has been resolved on subversion trunk. Are you using 2.7? Try
upgrading to svn.

You can also disable it by running with -regalloc=fast. That does not produce as
good code, but it is much much faster.

/jakob

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