Set ISD::FROUND to Expand by default for all types

For most libm ISD nodes, TargetLoweringBase::initActions sets the default
scalar-type action to Expand, and leaves the vector-type action default as
Legal. This is not appropriate for the new ISD::FROUND node (which no backend
but PowerPC handles explicitly).

Fixes PR16842.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@188048 91177308-0d34-0410-b5e6-96231b3b80d8
Change asserts at the top of getVectorShuffle to check that LHS and RHS have the same type as the result.

Previously the asserts were only checking that RHS and LHS were the same type and had the same element type as the result. All downstream code for ISD::VECTOR_SHUFFLE requires the types to be the same.

Also removed one unnecessary check of matched element counts that was present in the code.



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@188051 91177308-0d34-0410-b5e6-96231b3b80d8