[PATCH] D15519: Replace weights by probabilities in BPI.

[Cong Hou via llvm-commits]

congh added inline comments.

================
Comment at: lib/Analysis/BranchProbabilityInfo.cpp:143
@@ -149,9 +142,3 @@
 
-  uint32_t UnreachableWeight =
-    std::max(UR_TAKEN_WEIGHT / (unsigned)UnreachableEdges.size(), MIN_WEIGHT);
-  for (SmallVectorImpl<unsigned>::iterator I = UnreachableEdges.begin(),
-                                           E = UnreachableEdges.end();
-       I != E; ++I)
-    setEdgeWeight(BB, *I, UnreachableWeight);
-
-  if (ReachableEdges.empty())
+  if (ReachableEdges.empty()) {
+    BranchProbability Prob(1, UnreachableEdges.size());
----------------
congh wrote:
> davidxl wrote:
> > Can we unify the code a little more:
> > 
> > BranchProbability UnreachableProb =
> >    ( ReachableEdges.empty() ?
> >            BranchProbability(1, UnreachableEdges.size()) :
> >            BranchProbability(UR_TAKEN_WEIGHT, (....) * UnreachableEdges.size()));
> > BranchProbability ReachableProb = (UR_NOTAKEN_WEIGHT, ReachableEdges.size() * ...);
> > 
> > for (...: UnreachableEdges) 
> >     set...
> > for (...)
> >     set ...
> > 
> OK. We can set UnreachableProb to 100% when ReachableEdges is empty.
I later found that I have to take care of the non-zero divider case here. To make the code more clear, I think the early exit solution might be better.


http://reviews.llvm.org/D15519