[LLVMdev] Increasing TargetRegisterInfo::FirstVirtualRegister?

[andrew at sidefx.com]

Would it be possible to increase TargetRegisterInfo::FirstVirtualRegister
to something quite a bit larger - such as 2^31?  I'm working on a target
where all SSA values need to be assigned physical registers, and the
current limit of 16384 may limit the size of programs that I'm able to
handle.  2^31 is a nice value since there are equal numbers of possible
physical and virtual registers, and registers can just inspect the high
bit to determine if it's a virtual register.  My only concern is that
there may be data structures using FirstVirtualRegister to size tables
rather than using the MachineRegisterInfo limit.

Along with this change, I would also propose subtracting
FirstVirtualRegister from the printed values of virtual registers, so that
what used to be "reg16384" would now show up as "reg0".

Andrew