[PATCH] D30633: [BPI] Reduce the probability of unreachable edge to minimal value greater than 0

[Duncan P. N. Exon Smith via Phabricator via llvm-commits]

dexonsmith accepted this revision.
dexonsmith added a comment.

Tests LGTM.



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Comment at: lib/Analysis/BranchProbabilityInfo.cpp:202-206
+  auto UnreachableProb = UR_TAKEN_PROB;
+  auto ReachableProb =
+      (BranchProbability::getOne() - UR_TAKEN_PROB * UnreachableEdges.size()) /
+      ReachableEdges.size();
 
----------------
skatkov wrote:
> dexonsmith wrote:
> > This doesn't look to me like it will add up to `BranchProbability::getOne()` in the end.  Is that a problem?
> The sum of probabilities might be different than 1 and this consistent with all other heuristics in this file.
> It seems that it was not considered as problem before.
> 
> If you think it should be fixed I can come up with a follow-up patch fixing all cases. The question is actually where to add the remainder.
A follow-up patch seems fine.  I suggest spreading the remainder among the branches, 1 each until you run out, skipping the unreachable branch.


https://reviews.llvm.org/D30633