[PATCH] D20627: Do not rename registers that do not start an independent live range

Krzysztof Parzyszek via llvm-commits llvm-commits at lists.llvm.org
Wed May 25 16:13:00 PDT 2016

kparzysz added a comment.

In http://reviews.llvm.org/D20627#440120, @MatzeB wrote:

> Just out of interested: It seems to me that we only enable anti dependenc breakers for PPC and X86 by overriding getAntiDepBreakMode(), why does this code affect hexagon?

Hexagon will use the aggressive anti-dependency breaker.  In fact, our production compiler has it enabled (as well as the post-RA scheduler).  I want to switch to using subregister liveness tracking, and it exposed this issue.  The production compiler uses some intricate code to keep the liveness up to date using implicit operands and I want to eliminate it in favor of the subregister liveness.  After I get that to work, I'll make upstream changes to enable both post-RA scheduler and anti-dependency breaker for Hexagon.  In theory I could upstream that "intricate code", but I don't think there is a point if the next step will be to delete it.



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