[PATCH] [RFC] Lame fix for PR20376

[Tim Northover]

We actually do have a last-ditch EFLAGS copy available (though with worrying implications for the red-zone, if we ever start using it). It's used by test/CodeGen/Generic/2011-07-07-ScheduleDAGCrash.ll for example.

Enabling it more generally is probably just a matter of tweaking getCopyCost. Which might be an idea for robustness anyway.

But I'm not sure that actually affects the best solution here. I rather suspect performing the comparison again would be quicker in general. I suppose the question is how common and performance-critical such fragments are.

Cheers.

Tim.

http://reviews.llvm.org/D4611