[PATCH] D18827: Rework/enhance stack coloring data flow analysis.

[Than McIntosh via llvm-commits]

thanm added a comment.

In http://reviews.llvm.org/D18827#429001, @wmi wrote:

> Thanks for the detailed implementation notes and spec2006 data. The spec2006 data is a overall number which looks good. I guess for individual file there is no regression anymore, right?


Correct.

> But I havn't understood quite well about the way to handle case with degenerate slot.  From my understanding, for case with degenerate slot, its liverange from startmarker to endmarker is smaller than actual, so it is possible for stackcoloring to generate incorrect code for such case (although I understand the case is never worse than without the patch).  The question is before this patch, since the case with degenerate slot always existed, why we didn't see error caused by it?


Sorry, looking back at the example I put in the comment I think I left things a bit vague. In the case that I have seen so far where uses of the stack slot are hoisted outside of the livetime start/end interval, it's only the address computation that's outside the interval-- the actual memory load/store takes place inside. So at least for all of the cases I have seen so far, the program is still correct.

I will update the comments to make this clearer.

Thanks, Than


http://reviews.llvm.org/D18827