Add TargetRegisterInfo::getCoveringLanes().

This lane mask provides information about which register lanes
completely cover super-registers. See the block comment before
getCoveringLanes().

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@182034 91177308-0d34-0410-b5e6-96231b3b80d8
[mips] Delete unused enum value.



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@182035 91177308-0d34-0410-b5e6-96231b3b80d8
[mips] Fix indentation.



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@182036 91177308-0d34-0410-b5e6-96231b3b80d8
DAGCombine: Also shrink eq compares where the constant is exactly as large as the smaller type.

if ((x & 255) == 255)

before: movzbl  %al, %eax
        cmpl  $255, %eax

after:  cmpb  $-1, %al

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@182038 91177308-0d34-0410-b5e6-96231b3b80d8