[llvm-commits] [llvm] r120932 - in /llvm/trunk: lib/Target/X86/X86ISelLowering.cpp test/CodeGen/X86/select.ll

[Bob Wilson]

On Dec 6, 2010, at 12:38 PM, Chris Lattner wrote:

> 
> On Dec 6, 2010, at 9:29 AM, Bob Wilson wrote:
> 
>>>>> Along these lines, I wonder if it would be enough to just mark IR select/condbr instructions with an instruction MDNode like !highlybiased (optionally with a direction).  This could be preserved down to codegen level and used for expansion there. This would also be a straight-forward way to model __builtin_expect.
>>>> 
>>>> Do we want to make it a more generic MDNode so we can use it to encode branch probability?
>>> 
>>> Yes, making it more general than just "biased" makes sense.
>> 
>> I've been thinking about and talking with a few people about doing exactly that for recording profile information as well.  I don't yet have enough details to make a real proposal, but if you're planning to do anything like that soon, I'd be interested.
> 
> I don't have any plans or anything concrete to propose, I'd be happy for someone else to write up a proposal if they're interested.

OK.  I'm working on it in the background as time permits....  I hope to write something up soon, but it depends on what other tasks come my way.