[PowerPC][LegalizeFloatTypes] Move the PPC hacks for (i32 fp_to_sint/fp_to_uint ...

[PowerPC][LegalizeFloatTypes] Move the PPC hacks for (i32 fp_to_sint/fp_to_uint (ppcf128 X)) out of LegalizeFloatTypes and into PPC specific code

I'm not entirely sure these hacks are still needed. If you remove the hacks completely, the name of the library call that gets generated doesn't match the grep the test previously had. So the test wasn't really checking anything.

If the hack is still needed it belongs in PPC specific code. I believe the FP_TO_SINT code here is the only place in the tree where a FP_ROUND_INREG node is created today. And I don't think its even being used correctly because the legalization returned a BUILD_PAIR with the same value twice. That doesn't seem right to me. By moving the code entirely to PPC we can avoid creating the FP_ROUND_INREG at all.

I replaced the grep in the existing test with full checks generated by hacking update_llc_test_check.py to support ppc32 just long enough to generate it.

Differential Revision: https://reviews.llvm.org/D44061

llvm-svn: 328017