[LLVMdev] Recalculating live intervals

[Fernando Magno Quintao Pereira]

Well, someone correct me if am wrong, but, you still have to allocate
physical registers to them, because their values must be reloaded before
been used. But after you spill a register, you break its live ranges, so,
each use of that register can be loaded into a different physical. In my
register allocator, after I spill reg_v:

For each use of reg_v:
    create a new reg_v'
    replace reg_v by reg_v'

If the instruction containing reg_v' hasn't been scanned by the register
allocator, when it happens, reg_v' will receive a physical register. You
must assign to reg_v' a weight such that is is not spilled again,
otherwise you may enter on an infinite loop, always spilling the same
spilled register.

Fernando

>
> So, as far as I understood live intervals with weight equal to HUGE_VAL are
> spilled and I don't need to allocate physical registers for them, right?
> Shoud hasStackSlot method of VirtRegMap return true for these intervals' reg
> members?
>