[x86] Prevent instruction selection of AVX512 cmp.ps/pd/ss/sd intrinsics with illegal immediates. Forgot to do this when I did SSE/SSE2/AVX/AVX2.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@224887 91177308-0d34-0410-b5e6-96231b3b80d8
Removing a variable that is set but never used, to silence a -Wunused-but-set-variable warning; NFC.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@224888 91177308-0d34-0410-b5e6-96231b3b80d8
Fixing another -Wunused-variable warning, this time in release builds without asserts. NFC.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@224889 91177308-0d34-0410-b5e6-96231b3b80d8