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-rw-r--r--llvm/lib/CodeGen/IfConversion.cpp155
1 files changed, 86 insertions, 69 deletions
diff --git a/llvm/lib/CodeGen/IfConversion.cpp b/llvm/lib/CodeGen/IfConversion.cpp
index ff28f95cc33..0b2f3ea165f 100644
--- a/llvm/lib/CodeGen/IfConversion.cpp
+++ b/llvm/lib/CodeGen/IfConversion.cpp
@@ -32,7 +32,6 @@
#include "llvm/Target/TargetLowering.h"
#include "llvm/Target/TargetRegisterInfo.h"
#include "llvm/Target/TargetSubtargetInfo.h"
-#include <algorithm>
using namespace llvm;
@@ -1152,6 +1151,28 @@ bool IfConverter::IfConvertSimple(BBInfo &BBI, IfcvtKind Kind) {
return true;
}
+/// Scale down weights to fit into uint32_t. NewTrue is the new weight
+/// for successor TrueBB, and NewFalse is the new weight for successor
+/// FalseBB.
+static void ScaleWeights(uint64_t NewTrue, uint64_t NewFalse,
+ MachineBasicBlock *MBB,
+ const MachineBasicBlock *TrueBB,
+ const MachineBasicBlock *FalseBB,
+ const MachineBranchProbabilityInfo *MBPI) {
+ uint64_t NewMax = (NewTrue > NewFalse) ? NewTrue : NewFalse;
+ uint32_t Scale = (NewMax / UINT32_MAX) + 1;
+ for (MachineBasicBlock::succ_iterator SI = MBB->succ_begin(),
+ SE = MBB->succ_end();
+ SI != SE; ++SI) {
+ if (*SI == TrueBB)
+ MBB->setSuccWeight(SI, (uint32_t)(NewTrue / Scale));
+ else if (*SI == FalseBB)
+ MBB->setSuccWeight(SI, (uint32_t)(NewFalse / Scale));
+ else
+ MBB->setSuccWeight(SI, MBPI->getEdgeWeight(MBB, SI) / Scale);
+ }
+}
+
/// IfConvertTriangle - If convert a triangle sub-CFG.
///
bool IfConverter::IfConvertTriangle(BBInfo &BBI, IfcvtKind Kind) {
@@ -1208,14 +1229,16 @@ bool IfConverter::IfConvertTriangle(BBInfo &BBI, IfcvtKind Kind) {
DontKill.clear();
bool HasEarlyExit = CvtBBI->FalseBB != nullptr;
- BranchProbability CvtNext, CvtFalse, BBNext, BBCvt;
+ uint64_t CvtNext = 0, CvtFalse = 0, BBNext = 0, BBCvt = 0, SumWeight = 0;
+ uint32_t WeightScale = 0;
if (HasEarlyExit) {
- // Get probabilities before modifying CvtBBI->BB and BBI.BB.
- CvtNext = MBPI->getEdgeProbability(CvtBBI->BB, NextBBI->BB);
- CvtFalse = MBPI->getEdgeProbability(CvtBBI->BB, CvtBBI->FalseBB);
- BBNext = MBPI->getEdgeProbability(BBI.BB, NextBBI->BB);
- BBCvt = MBPI->getEdgeProbability(BBI.BB, CvtBBI->BB);
+ // Get weights before modifying CvtBBI->BB and BBI.BB.
+ CvtNext = MBPI->getEdgeWeight(CvtBBI->BB, NextBBI->BB);
+ CvtFalse = MBPI->getEdgeWeight(CvtBBI->BB, CvtBBI->FalseBB);
+ BBNext = MBPI->getEdgeWeight(BBI.BB, NextBBI->BB);
+ BBCvt = MBPI->getEdgeWeight(BBI.BB, CvtBBI->BB);
+ SumWeight = MBPI->getSumForBlock(CvtBBI->BB, WeightScale);
}
if (CvtBBI->BB->pred_size() > 1) {
@@ -1243,24 +1266,22 @@ bool IfConverter::IfConvertTriangle(BBInfo &BBI, IfcvtKind Kind) {
CvtBBI->BrCond.end());
if (TII->ReverseBranchCondition(RevCond))
llvm_unreachable("Unable to reverse branch condition!");
-
- // Update the edge probability for both CvtBBI->FalseBB and NextBBI.
- // NewNext = New_Prob(BBI.BB, NextBBI->BB) =
- // Prob(BBI.BB, NextBBI->BB) +
- // Prob(BBI.BB, CvtBBI->BB) * Prob(CvtBBI->BB, NextBBI->BB)
- // NewFalse = New_Prob(BBI.BB, CvtBBI->FalseBB) =
- // Prob(BBI.BB, CvtBBI->BB) * Prob(CvtBBI->BB, CvtBBI->FalseBB)
- auto NewTrueBB = getNextBlock(BBI.BB);
- auto NewNext = BBNext + BBCvt * CvtNext;
- auto NewTrueBBIter =
- std::find(BBI.BB->succ_begin(), BBI.BB->succ_end(), NewTrueBB);
- assert(NewTrueBBIter != BBI.BB->succ_end() &&
- "NewTrueBB is not a successor of BBI.BB.");
- BBI.BB->setSuccProbability(NewTrueBBIter, NewNext);
-
- auto NewFalse = BBCvt * CvtFalse;
TII->InsertBranch(*BBI.BB, CvtBBI->FalseBB, nullptr, RevCond, dl);
- BBI.BB->addSuccessor(CvtBBI->FalseBB, NewFalse);
+ BBI.BB->addSuccessor(CvtBBI->FalseBB);
+ // Update the edge weight for both CvtBBI->FalseBB and NextBBI.
+ // New_Weight(BBI.BB, NextBBI->BB) =
+ // Weight(BBI.BB, NextBBI->BB) * getSumForBlock(CvtBBI->BB) +
+ // Weight(BBI.BB, CvtBBI->BB) * Weight(CvtBBI->BB, NextBBI->BB)
+ // New_Weight(BBI.BB, CvtBBI->FalseBB) =
+ // Weight(BBI.BB, CvtBBI->BB) * Weight(CvtBBI->BB, CvtBBI->FalseBB)
+
+ uint64_t NewNext = BBNext * SumWeight + (BBCvt * CvtNext) / WeightScale;
+ uint64_t NewFalse = (BBCvt * CvtFalse) / WeightScale;
+ // We need to scale down all weights of BBI.BB to fit uint32_t.
+ // Here BBI.BB is connected to CvtBBI->FalseBB and will fall through to
+ // the next block.
+ ScaleWeights(NewNext, NewFalse, BBI.BB, getNextBlock(BBI.BB),
+ CvtBBI->FalseBB, MBPI);
}
// Merge in the 'false' block if the 'false' block has no other
@@ -1503,7 +1524,7 @@ bool IfConverter::IfConvertDiamond(BBInfo &BBI, IfcvtKind Kind,
MergeBlocks(BBI, TailBBI);
TailBBI.IsDone = true;
} else {
- BBI.BB->addSuccessor(TailBB, BranchProbability::getOne());
+ BBI.BB->addSuccessor(TailBB);
InsertUncondBranch(BBI.BB, TailBB, TII);
BBI.HasFallThrough = false;
}
@@ -1667,26 +1688,21 @@ void IfConverter::MergeBlocks(BBInfo &ToBBI, BBInfo &FromBBI, bool AddEdges) {
FromBBI.BB->succ_end());
MachineBasicBlock *NBB = getNextBlock(FromBBI.BB);
MachineBasicBlock *FallThrough = FromBBI.HasFallThrough ? NBB : nullptr;
- // The edge probability from ToBBI.BB to FromBBI.BB, which is only needed when
- // AddEdges is true and FromBBI.BB is a successor of ToBBI.BB.
- auto To2FromProb = BranchProbability::getZero();
- if (AddEdges && ToBBI.BB->isSuccessor(FromBBI.BB)) {
- To2FromProb = MBPI->getEdgeProbability(ToBBI.BB, FromBBI.BB);
- // Set the edge probability from ToBBI.BB to FromBBI.BB to zero to avoid the
- // edge probability being merged to other edges when this edge is removed
- // later.
- ToBBI.BB->setSuccProbability(
- std::find(ToBBI.BB->succ_begin(), ToBBI.BB->succ_end(), FromBBI.BB),
- BranchProbability::getZero());
- }
+ // The edge weight from ToBBI.BB to FromBBI.BB, which is only needed when
+ // AddEdges is true and FromBBI.BB is a successor of ToBBI.BB.
+ uint32_t To2FromWeight = 0;
+ // WeightScale and SumWeight are for calculating successor probabilities of
+ // FromBBI.BB.
+ uint32_t WeightScale = 0;
+ uint32_t SumWeight = 0;
if (AddEdges && ToBBI.BB->isSuccessor(FromBBI.BB)) {
- // Set the edge probability from ToBBI.BB to FromBBI.BB to zero to avoid the
- // edge probability being merged to other edges when this edge is removed
- // later.
- ToBBI.BB->setSuccProbability(
- std::find(ToBBI.BB->succ_begin(), ToBBI.BB->succ_end(), FromBBI.BB),
- BranchProbability::getZero());
+ To2FromWeight = MBPI->getEdgeWeight(ToBBI.BB, FromBBI.BB);
+ // Set the edge weight from ToBBI.BB to FromBBI.BB to zero to avoid the edge
+ // weight being merged to other edges when this edge is removed later.
+ ToBBI.BB->setSuccWeight(
+ std::find(ToBBI.BB->succ_begin(), ToBBI.BB->succ_end(), FromBBI.BB), 0);
+ SumWeight = MBPI->getSumForBlock(FromBBI.BB, WeightScale);
}
for (unsigned i = 0, e = FromSuccs.size(); i != e; ++i) {
@@ -1695,38 +1711,39 @@ void IfConverter::MergeBlocks(BBInfo &ToBBI, BBInfo &FromBBI, bool AddEdges) {
if (Succ == FallThrough)
continue;
- auto NewProb = BranchProbability::getZero();
+ uint32_t NewWeight = 0;
if (AddEdges) {
- // Calculate the edge probability for the edge from ToBBI.BB to Succ,
- // which is a portion of the edge probability from FromBBI.BB to Succ. The
- // portion ratio is the edge probability from ToBBI.BB to FromBBI.BB (if
- // FromBBI is a successor of ToBBI.BB. See comment below for excepion).
- NewProb = MBPI->getEdgeProbability(FromBBI.BB, Succ);
+ // Calculate the edge weight for the edge from ToBBI.BB to Succ, which is
+ // a portion of the edge weight from FromBBI.BB to Succ. The portion ratio
+ // is the edge probability from ToBBI.BB to FromBBI.BB (if FromBBI is a
+ // successor of ToBBI.BB. See comment below for excepion).
+ NewWeight = MBPI->getEdgeWeight(FromBBI.BB, Succ);
- // To2FromProb is 0 when FromBBI.BB is not a successor of ToBBI.BB. This
+ // To2FromWeight is 0 when FromBBI.BB is not a successor of ToBBI.BB. This
// only happens when if-converting a diamond CFG and FromBBI.BB is the
// tail BB. In this case FromBBI.BB post-dominates ToBBI.BB and hence we
- // could just use the probabilities on FromBBI.BB's out-edges when adding
- // new successors.
- if (!To2FromProb.isZero())
- NewProb *= To2FromProb;
+ // could just use the weights on FromBBI.BB's out-edges when adding new
+ // successors.
+ if (To2FromWeight > 0) {
+ BranchProbability Prob(NewWeight / WeightScale, SumWeight);
+ NewWeight = Prob.scale(To2FromWeight);
+ }
}
FromBBI.BB->removeSuccessor(Succ);
if (AddEdges) {
- // If the edge from ToBBI.BB to Succ already exists, update the
- // probability of this edge by adding NewWeight to it. An example is shown
- // below, in which A is ToBBI.BB and B is FromBBI.BB. In this case we
- // don't have to set C as A's successor as it already is. We only need to
- // update the edge probability on A->C. Note that B will not be
- // immediately removed from A's successors. It is possible that B->D is
- // not removed either if D is a fallthrough of B. Later the edge A->D
- // (generated here) and B->D will be combined into one edge. To maintain
- // correct edge probability of this combined edge, we need to set the edge
- // probability of A->B to zero, which is already done above. The edge
- // probability on A->D is calculated by scaling the original probability
- // on A->B by the probability of B->D.
+ // If the edge from ToBBI.BB to Succ already exists, update the weight of
+ // this edge by adding NewWeight to it. An example is shown below, in
+ // which A is ToBBI.BB and B is FromBBI.BB. In this case we don't have to
+ // set C as A's successor as it already is. We only need to update the
+ // edge weight on A->C. Note that B will not be immediately removed from
+ // A's successors. It is possible that B->D is not removed either if D is
+ // a fallthrough of B. Later the edge A->D (generated here) and B->D will
+ // be combined into one edge. To maintain correct edge weight of this
+ // combined edge, we need to set the edge weight of A->B to zero, which is
+ // already done above. The edge weight on A->D is calculated by scaling
+ // the original weight on A->B by the probability of B->D.
//
// Before ifcvt: After ifcvt (assume B->D is kept):
//
@@ -1738,11 +1755,11 @@ void IfConverter::MergeBlocks(BBInfo &ToBBI, BBInfo &FromBBI, bool AddEdges) {
// C D C D
//
if (ToBBI.BB->isSuccessor(Succ))
- ToBBI.BB->setSuccProbability(
+ ToBBI.BB->setSuccWeight(
std::find(ToBBI.BB->succ_begin(), ToBBI.BB->succ_end(), Succ),
- MBPI->getEdgeProbability(ToBBI.BB, Succ) + NewProb);
+ MBPI->getEdgeWeight(ToBBI.BB, Succ) + NewWeight);
else
- ToBBI.BB->addSuccessor(Succ, NewProb);
+ ToBBI.BB->addSuccessor(Succ, NewWeight);
}
}
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