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Replace hard coded probability threshold with parameter /NFC 

llvm-svn: 271751
This commit is contained in:
Xinliang David Li 2016-06-03 23:48:36 +00:00
parent 7bae9adb08
commit ff2873742e
2 changed files with 13 additions and 8 deletions
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4
llvm/lib/CodeGen/MachineBlockPlacement.cpp
View File

@ -116,6 +116,8 @@ static cl::opt<unsigned> JumpInstCost("jump-inst-cost",
cl::desc("Cost of jump instructions."), cl::desc("Cost of jump instructions."),
cl::init(1), cl::Hidden); cl::init(1), cl::Hidden);
extern cl::opt<unsigned> StaticLikelyProb;
namespace { namespace {
class BlockChain; class BlockChain;
/// \brief Type for our function-wide basic block -> block chain mapping. /// \brief Type for our function-wide basic block -> block chain mapping.
@ -405,7 +407,7 @@ MachineBasicBlock *
MachineBlockPlacement::selectBestSuccessor(MachineBasicBlock *BB, MachineBlockPlacement::selectBestSuccessor(MachineBasicBlock *BB,
BlockChain &Chain, BlockChain &Chain,
const BlockFilterSet *BlockFilter) { const BlockFilterSet *BlockFilter) {
const BranchProbability HotProb(4, 5); // 80% const BranchProbability HotProb(StaticLikelyProb, 100);
MachineBasicBlock *BestSucc = nullptr; MachineBasicBlock *BestSucc = nullptr;
auto BestProb = BranchProbability::getZero(); auto BestProb = BranchProbability::getZero();

17
llvm/lib/CodeGen/MachineBranchProbabilityInfo.cpp
View File

@ -24,9 +24,14 @@ INITIALIZE_PASS_BEGIN(MachineBranchProbabilityInfo, "machine-branch-prob",
INITIALIZE_PASS_END(MachineBranchProbabilityInfo, "machine-branch-prob", INITIALIZE_PASS_END(MachineBranchProbabilityInfo, "machine-branch-prob",
"Machine Branch Probability Analysis", false, true) "Machine Branch Probability Analysis", false, true)
cl::opt<unsigned> StaticLikelyProb(
"static-likely-prob",
cl::desc("branch probability threshold to be considered very likely"),
cl::init(80), cl::Hidden);
char MachineBranchProbabilityInfo::ID = 0; char MachineBranchProbabilityInfo::ID = 0;
void MachineBranchProbabilityInfo::anchor() { } void MachineBranchProbabilityInfo::anchor() {}
BranchProbability MachineBranchProbabilityInfo::getEdgeProbability( BranchProbability MachineBranchProbabilityInfo::getEdgeProbability(
const MachineBasicBlock *Src, const MachineBasicBlock *Src,
@ -42,11 +47,9 @@ BranchProbability MachineBranchProbabilityInfo::getEdgeProbability(
std::find(Src->succ_begin(), Src->succ_end(), Dst)); std::find(Src->succ_begin(), Src->succ_end(), Dst));
} }
bool bool MachineBranchProbabilityInfo::isEdgeHot(
MachineBranchProbabilityInfo::isEdgeHot(const MachineBasicBlock *Src, const MachineBasicBlock *Src, const MachineBasicBlock *Dst) const {
const MachineBasicBlock *Dst) const { BranchProbability HotProb(StaticLikelyProb, 100);
// Hot probability is at least 4/5 = 80%
static BranchProbability HotProb(4, 5);
return getEdgeProbability(Src, Dst) > HotProb; return getEdgeProbability(Src, Dst) > HotProb;
} }
@ -63,7 +66,7 @@ MachineBranchProbabilityInfo::getHotSucc(MachineBasicBlock *MBB) const {
} }
} }
static BranchProbability HotProb(4, 5); BranchProbability HotProb(StaticLikelyProb, 100);
if (getEdgeProbability(MBB, MaxSucc) >= HotProb) if (getEdgeProbability(MBB, MaxSucc) >= HotProb)
return MaxSucc; return MaxSucc;