//
//===----------------------------------------------------------------------===//
-#include "llvm/Instructions.h"
#include "llvm/CodeGen/MachineBranchProbabilityInfo.h"
#include "llvm/CodeGen/MachineBasicBlock.h"
+#include "llvm/IR/Instructions.h"
#include "llvm/Support/Debug.h"
#include "llvm/Support/raw_ostream.h"
void MachineBranchProbabilityInfo::anchor() { }
-uint32_t MachineBranchProbabilityInfo::
-getSumForBlock(const MachineBasicBlock *MBB, uint32_t &Scale) const {
- // First we compute the sum with 64-bits of precision, ensuring that cannot
- // overflow by bounding the number of weights considered. Hopefully no one
- // actually needs 2^32 successors.
- assert(MBB->succ_size() < UINT32_MAX);
- uint64_t Sum = 0;
- Scale = 1;
- for (MachineBasicBlock::const_succ_iterator I = MBB->succ_begin(),
- E = MBB->succ_end(); I != E; ++I) {
- uint32_t Weight = getEdgeWeight(MBB, *I);
- Sum += Weight;
- }
-
- // If the computed sum fits in 32-bits, we're done.
- if (Sum <= UINT32_MAX)
- return Sum;
-
- // Otherwise, compute the scale necessary to cause the weights to fit, and
- // re-sum with that scale applied.
- assert((Sum / UINT32_MAX) < UINT32_MAX);
- Scale = (Sum / UINT32_MAX) + 1;
- Sum = 0;
- for (MachineBasicBlock::const_succ_iterator I = MBB->succ_begin(),
- E = MBB->succ_end(); I != E; ++I) {
- uint32_t Weight = getEdgeWeight(MBB, *I);
- Sum += Weight / Scale;
- }
- assert(Sum <= UINT32_MAX);
- return Sum;
+BranchProbability MachineBranchProbabilityInfo::getEdgeProbability(
+ const MachineBasicBlock *Src,
+ MachineBasicBlock::const_succ_iterator Dst) const {
+ return Src->getSuccProbability(Dst);
}
-uint32_t
-MachineBranchProbabilityInfo::getEdgeWeight(const MachineBasicBlock *Src,
- const MachineBasicBlock *Dst) const {
- uint32_t Weight = Src->getSuccWeight(Dst);
- if (!Weight)
- return DEFAULT_WEIGHT;
- return Weight;
+BranchProbability MachineBranchProbabilityInfo::getEdgeProbability(
+ const MachineBasicBlock *Src, const MachineBasicBlock *Dst) const {
+ // This is a linear search. Try to use the const_succ_iterator version when
+ // possible.
+ return getEdgeProbability(Src,
+ std::find(Src->succ_begin(), Src->succ_end(), Dst));
}
-bool MachineBranchProbabilityInfo::isEdgeHot(MachineBasicBlock *Src,
- MachineBasicBlock *Dst) const {
+bool
+MachineBranchProbabilityInfo::isEdgeHot(const MachineBasicBlock *Src,
+ const MachineBasicBlock *Dst) const {
// Hot probability is at least 4/5 = 80%
- // FIXME: Compare against a static "hot" BranchProbability.
- return getEdgeProbability(Src, Dst) > BranchProbability(4, 5);
+ static BranchProbability HotProb(4, 5);
+ return getEdgeProbability(Src, Dst) > HotProb;
}
MachineBasicBlock *
MachineBranchProbabilityInfo::getHotSucc(MachineBasicBlock *MBB) const {
- uint32_t MaxWeight = 0;
- MachineBasicBlock *MaxSucc = 0;
+ auto MaxProb = BranchProbability::getZero();
+ MachineBasicBlock *MaxSucc = nullptr;
for (MachineBasicBlock::const_succ_iterator I = MBB->succ_begin(),
E = MBB->succ_end(); I != E; ++I) {
- uint32_t Weight = getEdgeWeight(MBB, *I);
- if (Weight > MaxWeight) {
- MaxWeight = Weight;
+ auto Prob = getEdgeProbability(MBB, I);
+ if (Prob > MaxProb) {
+ MaxProb = Prob;
MaxSucc = *I;
}
}
- if (getEdgeProbability(MBB, MaxSucc) >= BranchProbability(4, 5))
+ static BranchProbability HotProb(4, 5);
+ if (getEdgeProbability(MBB, MaxSucc) >= HotProb)
return MaxSucc;
- return 0;
-}
-
-BranchProbability
-MachineBranchProbabilityInfo::getEdgeProbability(MachineBasicBlock *Src,
- MachineBasicBlock *Dst) const {
- uint32_t Scale = 1;
- uint32_t D = getSumForBlock(Src, Scale);
- uint32_t N = getEdgeWeight(Src, Dst) / Scale;
-
- return BranchProbability(N, D);
+ return nullptr;
}
-raw_ostream &MachineBranchProbabilityInfo::
-printEdgeProbability(raw_ostream &OS, MachineBasicBlock *Src,
- MachineBasicBlock *Dst) const {
+raw_ostream &MachineBranchProbabilityInfo::printEdgeProbability(
+ raw_ostream &OS, const MachineBasicBlock *Src,
+ const MachineBasicBlock *Dst) const {
const BranchProbability Prob = getEdgeProbability(Src, Dst);
OS << "edge MBB#" << Src->getNumber() << " -> MBB#" << Dst->getNumber()
- << " probability is " << Prob
+ << " probability is " << Prob
<< (isEdgeHot(Src, Dst) ? " [HOT edge]\n" : "\n");
return OS;