[llvm-commits] [llvm] r108109 - /llvm/trunk/lib/CodeGen/MachineLICM.cpp

Evan Cheng evan.cheng at apple.com
Mon Jul 12 20:55:37 PDT 2010


On Jul 12, 2010, at 8:46 PM, Chris Lattner wrote:

> 
> On Jul 12, 2010, at 4:53 PM, Evan Cheng wrote:
> 
>>> I can't imagine why we would want to keep IMPLICIT_DEFs around, but I can imagine ProcessImplicitDefs getting confused because the code is not SSA.
>>> 
>>> 
>> 
>> 
>> RA, or rather ProcessImplicitDef pass, turn them into trivial short live ranges when it's possible. But it does miss some cases. It's relatively rare but it does happen.
> 
> I don't think that LICM should be complicated by a deficiency handling implicit defs.

I agree. But it's already neutered by register allocator deficiency. We are only hoisting some of the loop invariants for fear of increasing register pressure. We should remove all such restrictions only after live range splitting work lands.

Evan

> 
> -Chris





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