X86: Improve BT instruction selection for 64-bit values.

If a 64-bit value is tested against a bit which is known to be in the range
[0..31) (modulo 64), we can use the 32-bit BT instruction, which has a slightly
shorter encoding.

Differential Revision: https://reviews.llvm.org/D25862

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@284864 91177308-0d34-0410-b5e6-96231b3b80d8
2 files changed