diff options
Diffstat (limited to 'lib/CodeGen')
| -rw-r--r-- | lib/CodeGen/MachineBlockPlacement.cpp | 17 |
1 files changed, 13 insertions, 4 deletions
diff --git a/lib/CodeGen/MachineBlockPlacement.cpp b/lib/CodeGen/MachineBlockPlacement.cpp index ca17ad07e4..bd50ac3a4d 100644 --- a/lib/CodeGen/MachineBlockPlacement.cpp +++ b/lib/CodeGen/MachineBlockPlacement.cpp @@ -334,7 +334,15 @@ MachineBasicBlock *MachineBlockPlacement::selectBestSuccessor( const BranchProbability HotProb(4, 5); // 80% MachineBasicBlock *BestSucc = 0; - BranchProbability BestProb = BranchProbability::getZero(); + // FIXME: Due to the performance of the probability and weight routines in + // the MBPI analysis, we manually compute probabilities using the edge + // weights. This is suboptimal as it means that the somewhat subtle + // definition of edge weight semantics is encoded here as well. We should + // improve the MBPI interface to effeciently support query patterns such as + // this. + uint32_t BestWeight = 0; + uint32_t WeightScale = 0; + uint32_t SumWeight = MBPI->getSumForBlock(BB, WeightScale); DEBUG(dbgs() << "Attempting merge from: " << getBlockName(BB) << "\n"); for (MachineBasicBlock::succ_iterator SI = BB->succ_begin(), SE = BB->succ_end(); @@ -347,7 +355,8 @@ MachineBasicBlock *MachineBlockPlacement::selectBestSuccessor( continue; } - BranchProbability SuccProb = MBPI->getEdgeProbability(BB, *SI); + uint32_t SuccWeight = MBPI->getEdgeWeight(BB, *SI); + BranchProbability SuccProb(SuccWeight / WeightScale, SumWeight); // Only consider successors which are either "hot", or wouldn't violate // any CFG constraints. @@ -360,10 +369,10 @@ MachineBasicBlock *MachineBlockPlacement::selectBestSuccessor( << " (prob)" << (SuccChain.LoopPredecessors != 0 ? " (CFG break)" : "") << "\n"); - if (BestSucc && BestProb >= SuccProb) + if (BestSucc && BestWeight >= SuccWeight) continue; BestSucc = *SI; - BestProb = SuccProb; + BestWeight = SuccWeight; } return BestSucc; } |