[llvm] r233447 - [SCEV] Look at backedge dominating conditions.

[Evgeniy Stepanov]

You latest patch does not help.
Attaching a sample source file (this is a pre-processed bn_asm.c from
openssl with a custom config).
Build with -fsanitize=memory -O1.



On Tue, Mar 31, 2015 at 1:27 AM, Sanjoy Das
<sanjoy at playingwithpointers.com> wrote:
>> The isSingleEdge() call you make in this patch will be linear time, sadly ;(
>
> Yes, looks like isSingleEdge is O(# of successors).  It should be
> possible to write a faster but less precise version of isSingleEdge
> such that it only looks at blocks with two successors.  I think I can
> also exploit LoopInfo::isLoopExiting to make this faster.
>
> However, before I do any of the above, I want to understand what
> actually is causing the slowdown. :)
>
> -- Sanjoy
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