[llvm-commits] [llvm] r108639 - /llvm/trunk/lib/CodeGen/SelectionDAG/DAGCombiner.cpp

[Chris Lattner]

On Jul 18, 2010, at 12:44 PM, Owen Anderson wrote:

> 
> On Jul 18, 2010, at 12:04 PM, Chris Lattner wrote:
>> I agree that the xform is correct.  Why not do it on IR though?
> 
> For the reasons I laid out in the earlier email, namely that it would require adding a sqrt() -> intrinsic transform at the IR level, which SelectionDAG is already doing, so it seemed like extraneous effort on the optimizer's part.  If you really want, I can re-implement it as a SimplifyLibCalls+InstCombine xform, though.

I would prefer for this to happen in InstCombiner::visitFPTrunc.  Both because we already have the infrastructure to do this there, but also because your code only handles the -fno-math-errno case.  Normal calls to libm sqrt should be transformed, not just llvm.sqrt.

-Chris