Add a new method which enables one to change register classes.
See the Mips16ISetLowering.cpp patch to see a use of this.
For now now the extra code in Mips16ISetLowering.cpp is a nop but is
used for test purposes. Mips32 registers are setup and then removed and
then the Mips16 registers are setup. 

Normally you need to add register classes and then call
computeRegisterProperties.



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@177120 91177308-0d34-0410-b5e6-96231b3b80d8
Prepare for adding InstrSchedModel annotations to X86 instructions.

The new InstrSchedModel is easier to use than the instruction
itineraries. It will be used to model instruction latency and throughput
in modern Intel microarchitectures like Sandy Bridge.

InstrSchedModel should be able to coexist with instruction itinerary
classes, but for cleanliness we should switch the Atom processor model
to the new InstrSchedModel as well.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@177122 91177308-0d34-0410-b5e6-96231b3b80d8
Fix r177112: Add ProcResGroup.

This is the other half of r177122 that I meant to commit at the same time.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@177123 91177308-0d34-0410-b5e6-96231b3b80d8