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[JumpThreading] Handle zero !prof branch_weights

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Avoid division by zero in updatePredecessorProfileMetadata().

Reviewers: yamauchi
Tags: #llvm
Differential Revision: https://reviews.llvm.org/D81499
This commit is contained in:
Yevgeny Rouban
2020-06-12 11:55:15 +07:00
parent 0ce9bf6eed
commit 707836ed4e
1 changed files with 11 additions and 5 deletions
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16
llvm/lib/Transforms/Scalar/JumpThreading.cpp
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@@ -214,11 +214,16 @@ static void updatePredecessorProfileMetadata(PHINode *PN, BasicBlock *BB) {
if (!CondBr)
return;
BranchProbability BP;
uint64_t TrueWeight, FalseWeight;
if (!CondBr->extractProfMetadata(TrueWeight, FalseWeight))
return;
if (TrueWeight + FalseWeight == 0)
// Zero branch_weights do not give a hint for getting branch probabilities.
// Technically it would result in division by zero denominator, which is
// TrueWeight + FalseWeight.
return;
// Returns the outgoing edge of the dominating predecessor block
// that leads to the PhiNode's incoming block:
auto GetPredOutEdge =
@@ -253,10 +258,11 @@ static void updatePredecessorProfileMetadata(PHINode *PN, BasicBlock *BB) {
if (!CI || !CI->getType()->isIntegerTy(1))
continue;
BP = (CI->isOne() ? BranchProbability::getBranchProbability(
TrueWeight, TrueWeight + FalseWeight)
: BranchProbability::getBranchProbability(
FalseWeight, TrueWeight + FalseWeight));
BranchProbability BP =
(CI->isOne() ? BranchProbability::getBranchProbability(
TrueWeight, TrueWeight + FalseWeight)
: BranchProbability::getBranchProbability(
FalseWeight, TrueWeight + FalseWeight));
auto PredOutEdge = GetPredOutEdge(PN->getIncomingBlock(i), BB);
if (!PredOutEdge.first)