[llvm-commits] Machine Branch Probability Info

[Jakob Olesen]

On Jun 15, 2011, at 9:53 AM, Jakub Staszak wrote:

> 
> On Jun 14, 2011, at 11:28 AM, Jakob Olesen wrote:
> 
>> +++ include/llvm/CodeGen/MachineBasicBlock.h	(working copy)
>> 
>> Please make sure that the weight vectors are not allocated in -O0 builds. We don't want to pay for profiling info that isn't there. Same thing with -use-mbpi.
>> 
> 
> Jakob,
> 
> How can I do that? I don't have any access to OptLevel in MachineBasicBlock.

When there is no profile info available, don't add weights to basic blocks.

I see the problem, but do try to think of a way to avoid allocating a lot of vectors of nulls.

One possible solution is to pretend that an empty vector means the same as a vector of nulls. Never allocate a vector just to add a 0.

/jakob