[llvm] r190309 - [ARMv8] Prevent generation of deprecated IT blocks on ARMv8 in Thumb mode.

[Tim Northover]

Hi Artyom & Hal,

> Hal, can you confirm that this patch restores the correct functioning on PPC?

It would also be very good to get a proper test-case for this PPC
requirement committed. We couldn't possibly have broken it if there
had already been one. ;-)

> Tim, can you review my changes to Thumb2InstrInfo? In part, should the change depend on hasV8Ops?

I think that patch looks like the right approach, after a little
thought this afternoon. Though it's not my area really.

I think it should depend on hasV8 since it looks like previously we
could convert a T1 encoding to a T2, which would increase the range
and potentially reduce the weird control-flow shenanigans performed by
ConstantIslands.

Cheers.

Tim.