From 63c9c81152234922b80e449f650e93e9c9bd0dca Mon Sep 17 00:00:00 2001 From: Serguei Katkov Date: Fri, 12 May 2017 07:50:06 +0000 Subject: [BPI] Ignore remainder while distributing the remaining probability from unreachanble This is a follow up patch for https://reviews.llvm.org/rL300440 to address a comment. To make implementation to be consistent with other cases we just ignore the remainder after distribution of remaining probability between reachable edges. If we reduced the probability of some edges coming to unreachable blocks we should distribute the remaining part across other edges coming to reachable blocks to satisfy the condition that sum of all probabilities should be equal to one. If this remaining part is not divided by number of "reachable" edges then we get this remainder. This remainder probability should be pretty small. Other cases just ignore if the sum of probabilities is not equal to one so we do the same. Reviewers: chandlerc, sanjoy, vsk, junbuml, reames Reviewed By: reames Subscribers: reames, llvm-commits Differential Revision: https://reviews.llvm.org/D32124 llvm-svn: 302883 --- llvm/lib/Analysis/BranchProbabilityInfo.cpp | 11 +++-------- 1 file changed, 3 insertions(+), 8 deletions(-) (limited to 'llvm/lib/Analysis/BranchProbabilityInfo.cpp') diff --git a/llvm/lib/Analysis/BranchProbabilityInfo.cpp b/llvm/lib/Analysis/BranchProbabilityInfo.cpp index 0dc4475ca0e..db87b17c156 100644 --- a/llvm/lib/Analysis/BranchProbabilityInfo.cpp +++ b/llvm/lib/Analysis/BranchProbabilityInfo.cpp @@ -301,6 +301,8 @@ bool BranchProbabilityInfo::calcMetadataWeights(const BasicBlock *BB) { WeightSum += Weights[i]; } } + assert(WeightSum <= UINT32_MAX && + "Expected weights to scale down to 32 bits"); if (WeightSum == 0 || ReachableIdxs.size() == 0) { for (unsigned i = 0, e = TI->getNumSuccessors(); i != e; ++i) @@ -328,21 +330,14 @@ bool BranchProbabilityInfo::calcMetadataWeights(const BasicBlock *BB) { // the difference between reachable blocks. if (ToDistribute > BranchProbability::getZero()) { BranchProbability PerEdge = ToDistribute / ReachableIdxs.size(); - for (auto i : ReachableIdxs) { + for (auto i : ReachableIdxs) BP[i] += PerEdge; - ToDistribute -= PerEdge; - } - // Tail goes to the first reachable edge. - BP[ReachableIdxs[0]] += ToDistribute; } } for (unsigned i = 0, e = TI->getNumSuccessors(); i != e; ++i) setEdgeProbability(BB, i, BP[i]); - assert(WeightSum <= UINT32_MAX && - "Expected weights to scale down to 32 bits"); - return true; } -- cgit v1.2.3