[LoopVectorizer] Use two step casting for float to pointer types.

[LoopVectorizer] Use two step casting for float to pointer types.

Summary:
LoopVectorizer is creating casts between vec<ptr> and vec<float> types
on ARM when compiling OpenCV. Since, tIs is illegal to directly cast a
floating point type to a pointer type even if the types have same size
causing a crash. Fix the crash using a two-step casting by bitcasting
to integer and integer to pointer/float.
Fixes PR33804.

Reviewers: mkuper, Ayal, dlj, rengolin, srhines

Reviewed By: rengolin

Subscribers: aemerson, kristof.beyls, mkazantsev, Meinersbur, rengolin, mzolotukhin, llvm-commits

Differential Revision: https://reviews.llvm.org/D35498

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@312331 91177308-0d34-0410-b5e6-96231b3b80d8