- Fix interaction between r371813 and r371814.
- [TargetRegisterInfo] Remove SVT argument from getCommonSubClass. This was added to support fp128 on x86-64, but appears to be unneeded now. This may be because the FR128 register class added back then was merged with the VR128 register class later.
- Remove reliance on lax vector conversions from altivec.h and its test.
- Revert "For PR17164: split -fno-lax-vector-conversion into three different" This breaks the LLDB build. I tried reaching out to Richard, but haven't gotten a reply yet.