[PATCH] D21189: Create subranges for new intervals resulting from live interval splitting

[Krzysztof Parzyszek via llvm-commits]

kparzysz added a comment.

In http://reviews.llvm.org/D21189#466695, @kparzysz wrote:

> In http://reviews.llvm.org/D21189#466694, @MatzeB wrote:
>
> > Maybe if we had a way to clean extra unused dead-defs...
>
>
> I thought of having such defs (including those created by IMPLICIT_DEFs) as always dead in a live range, and have them be non-extendable.


I may have misread your comment.  You are saying that the existence of these defs (dead or not) can cause regressions in the register allocator?  I don't think that the allocator can actually assign two different (unrelated) registers to sub-ranges of a single large virtual register, can it?  There is a pass that would separate independent lanes, I guess that would help here: a read-undef could become an actual IMPLICIT_DEF, and then, if it's removable, it could be deleted completely.


Repository:
  rL LLVM

http://reviews.llvm.org/D21189