[llvm-commits] [llvm] r134516 - in /llvm/trunk: include/llvm/ include/llvm/Support/ include/llvm/Transforms/ lib/CodeGen/ lib/CodeGen/SelectionDAG/ lib/Transforms/Scalar/ lib/Transforms/Utils/ lib/VMCore/ test/CodeGen/Generic/ test/Transforms/LowerExpectIntrinsic/

[Jakub Staszak]

Hi Chris,

Right now clang creates "expect" intrinsic for every __builtin_expect instruction. These intrinsics must be lowered early because in other case they can harm other optimizations. During the lowering we also create "branch_weight" metadata, which can be used by other optimizations using BranchProbability analysis.

-Kuba

On Jul 6, 2011, at 5:31 PM, Chris Lattner wrote:

> 
> On Jul 6, 2011, at 11:22 AM, Jakub Staszak wrote:
> 
>> Author: kuba
>> Date: Wed Jul  6 13:22:43 2011
>> New Revision: 134516
>> 
>> URL: http://llvm.org/viewvc/llvm-project?rev=134516&view=rev
>> Log:
>> Introduce "expect" intrinsic instructions.
>> 
> 
> Hi Kuba,
> 
> Why is this introducing a new pass to do lowering?
> 
> -Chris

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