[SystemZ] Rename subregs and add subreg_h32

Use subreg_hNN and subreg_lNN for the high and low NN bits of a register.
List the low registers first, so that subreg_l32 also means the low 32
bits of a 128-bit register.

Floats are stored in the upper 32 bits of a 64-bit register, so they
should use subreg_h32 rather than subreg_l32.

No behavioral change intended.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@191659 91177308-0d34-0410-b5e6-96231b3b80d8
[SystemZ] Add GRH32 for the high word of a GR64

The only thing this does on its own is make the definitions of RISB[HL]G
a bit more precise.  Those instructions are only used by the MC layer at
the moment, so no behavioral change is intended.  The class is needed by
later patches though.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@191660 91177308-0d34-0410-b5e6-96231b3b80d8
[SystemZ] Add definitions of LFH and STFH


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@191661 91177308-0d34-0410-b5e6-96231b3b80d8