[PATCH] D13417: [MachineCombiner] make slack optional in critical path cost calculation (PR25016)

[Jakob Stoklund Olesen via llvm-commits]

stoklund added a comment.

In http://reviews.llvm.org/D13417#261721, @spatel wrote:

> I think that shows the intended usage: slack is limited both by a dynamic calculation and a heuristic. Without those limits, we're almost certain to increase the critical path and lose performance (as shown in the examples here).


The slack is simply computed relative to the critical path such that depth+slack+height = criticalpath.

However, figuring out latencies of values returned by different function calls mostly amounts to guessing. Without any insight into the called function, there is not much to infer.


http://reviews.llvm.org/D13417