[PATCH] SelectionDAG: fold (fp_to_u/sint (u/sint_to_fp val)) when possible

[Owen Anderson]

> On Feb 11, 2015, at 12:24 PM, Mehdi Amini <mehdi.amini at apple.com> wrote:
> 
>> 
>> 2) should the DAG combine be enhanced too to match the InstCombine? That is, are we allowed to take advantage of undefined behavior in the DAGCombine, or is that bad because the target may shuffle around the DAG in ways that relies on target-specific behavior?
> 
> I assume that if a target wants “target specific” behavior, they have to use their own ISD node.


This gets into thorny semantic areas, but yes, the semantics of the DAG match the semantics of LLVM IR unless and until target-specific nodes are introduced.

—Owen
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