diff options
Diffstat (limited to 'llvm/lib/CodeGen/MachineBlockPlacement.cpp')
| -rw-r--r-- | llvm/lib/CodeGen/MachineBlockPlacement.cpp | 24 |
1 files changed, 16 insertions, 8 deletions
diff --git a/llvm/lib/CodeGen/MachineBlockPlacement.cpp b/llvm/lib/CodeGen/MachineBlockPlacement.cpp index 186daa1cb8e..7379a3099b1 100644 --- a/llvm/lib/CodeGen/MachineBlockPlacement.cpp +++ b/llvm/lib/CodeGen/MachineBlockPlacement.cpp @@ -125,6 +125,7 @@ BranchFoldPlacement("branch-fold-placement", cl::init(true), cl::Hidden); extern cl::opt<unsigned> StaticLikelyProb; +extern cl::opt<unsigned> ProfileLikelyProb; namespace { class BlockChain; @@ -520,13 +521,20 @@ bool MachineBlockPlacement::shouldPredBlockBeOutlined( return false; } -// FIXME (PGO handling) -// For now this method just returns a fixed threshold. It needs to be enhanced -// such that BB and Succ is passed in so that CFG shapes are examined such that -// the threshold is computed with more precise cost model when PGO is on. -static BranchProbability getLayoutSuccessorProbThreshold() { - BranchProbability HotProb(StaticLikelyProb, 100); - return HotProb; +// When profile is not present, return the StaticLikelyProb. +// When profile is available, we need to handle the triangle-shape CFG. +static BranchProbability getLayoutSuccessorProbThreshold( + MachineBasicBlock *BB) { + if (!BB->getParent()->getFunction()->getEntryCount()) + return BranchProbability(StaticLikelyProb, 100); + if (BB->succ_size() == 2) { + const MachineBasicBlock *Succ1 = *BB->succ_begin(); + const MachineBasicBlock *Succ2 = *(BB->succ_begin() + 1); + if (Succ1->isSuccessor(Succ2) || Succ2->isSuccessor(Succ1)) + return BranchProbability( + 200 - 2 * ProfileLikelyProb, 200 - ProfileLikelyProb); + } + return BranchProbability(ProfileLikelyProb, 100); } /// Checks to see if the layout candidate block \p Succ has a better layout @@ -593,7 +601,7 @@ bool MachineBlockPlacement::hasBetterLayoutPredecessor( // edge: Prob(Succ->BB) needs to >= HotProb in order to be selected (without // profile data). - BranchProbability HotProb = getLayoutSuccessorProbThreshold(); + BranchProbability HotProb = getLayoutSuccessorProbThreshold(BB); // Forward checking. For case 2, SuccProb will be 1. if (SuccProb < HotProb) { |
