Introduce MachineBranchProbabilityInfo class, which has similar API to
BranchProbabilityInfo (expect setEdgeWeight which is not available here).
Branch Weights are kept in MachineBasicBlocks. To turn off this analysis
set -use-mbpi=false.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@133184 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/CodeGen/CMakeLists.txt b/lib/CodeGen/CMakeLists.txt
index c726d92..aef4ff2 100644
--- a/lib/CodeGen/CMakeLists.txt
+++ b/lib/CodeGen/CMakeLists.txt
@@ -33,6 +33,7 @@
LocalStackSlotAllocation.cpp
LowerSubregs.cpp
MachineBasicBlock.cpp
+ MachineBranchProbabilityInfo.cpp
MachineCSE.cpp
MachineDominators.cpp
MachineFunction.cpp
diff --git a/lib/CodeGen/MachineBasicBlock.cpp b/lib/CodeGen/MachineBasicBlock.cpp
index bc1998c..613f0c4 100644
--- a/lib/CodeGen/MachineBasicBlock.cpp
+++ b/lib/CodeGen/MachineBasicBlock.cpp
@@ -339,25 +339,64 @@
}
}
-void MachineBasicBlock::addSuccessor(MachineBasicBlock *succ) {
- Successors.push_back(succ);
- succ->addPredecessor(this);
-}
+void MachineBasicBlock::addSuccessor(MachineBasicBlock *succ, uint32_t weight) {
+
+ // If we see non-zero value for the first time it means we actually use Weight
+ // list, so we fill all Weights with 0's.
+ if (weight != 0 && Weights.empty())
+ Weights.resize(Successors.size());
+
+ if (weight != 0 || !Weights.empty())
+ Weights.push_back(weight);
+
+ Successors.push_back(succ);
+ succ->addPredecessor(this);
+ }
void MachineBasicBlock::removeSuccessor(MachineBasicBlock *succ) {
succ->removePredecessor(this);
succ_iterator I = std::find(Successors.begin(), Successors.end(), succ);
assert(I != Successors.end() && "Not a current successor!");
+
+ // If Weight list is empty it means we don't use it (disabled optimization).
+ if (!Weights.empty()) {
+ weight_iterator WI = getWeightIterator(I);
+ Weights.erase(WI);
+ }
+
Successors.erase(I);
}
MachineBasicBlock::succ_iterator
MachineBasicBlock::removeSuccessor(succ_iterator I) {
assert(I != Successors.end() && "Not a current successor!");
+
+ // If Weight list is empty it means we don't use it (disabled optimization).
+ if (!Weights.empty()) {
+ weight_iterator WI = getWeightIterator(I);
+ Weights.erase(WI);
+ }
+
(*I)->removePredecessor(this);
return Successors.erase(I);
}
+void MachineBasicBlock::replaceSuccessor(MachineBasicBlock *Old,
+ MachineBasicBlock *New) {
+ uint32_t weight = 0;
+ succ_iterator SI = std::find(Successors.begin(), Successors.end(), Old);
+
+ // If Weight list is empty it means we don't use it (disabled optimization).
+ if (!Weights.empty()) {
+ weight_iterator WI = getWeightIterator(SI);
+ weight = *WI;
+ }
+
+ // Update the successor information.
+ removeSuccessor(SI);
+ addSuccessor(New, weight);
+}
+
void MachineBasicBlock::addPredecessor(MachineBasicBlock *pred) {
Predecessors.push_back(pred);
}
@@ -374,7 +413,14 @@
while (!fromMBB->succ_empty()) {
MachineBasicBlock *Succ = *fromMBB->succ_begin();
- addSuccessor(Succ);
+ uint32_t weight = 0;
+
+
+ // If Weight list is empty it means we don't use it (disabled optimization).
+ if (!fromMBB->Weights.empty())
+ weight = *fromMBB->Weights.begin();
+
+ addSuccessor(Succ, weight);
fromMBB->removeSuccessor(Succ);
}
}
@@ -637,8 +683,7 @@
}
// Update the successor information.
- removeSuccessor(Old);
- addSuccessor(New);
+ replaceSuccessor(Old, New);
}
/// CorrectExtraCFGEdges - Various pieces of code can cause excess edges in the
@@ -720,6 +765,23 @@
return DL;
}
+/// getSuccWeight - Return weight of the edge from this block to MBB.
+///
+uint32_t MachineBasicBlock::getSuccWeight(MachineBasicBlock *succ) {
+ succ_iterator I = std::find(Successors.begin(), Successors.end(), succ);
+ return *getWeightIterator(I);
+}
+
+/// getWeightIterator - Return wight iterator corresonding to the I successor
+/// iterator
+MachineBasicBlock::weight_iterator MachineBasicBlock::
+getWeightIterator(MachineBasicBlock::succ_iterator I) {
+ assert(Weights.size() == Successors.size() && "Async weight list!");
+ size_t index = std::distance(Successors.begin(), I);
+ assert(index < Weights.size() && "Not a current successor!");
+ return Weights.begin() + index;
+}
+
void llvm::WriteAsOperand(raw_ostream &OS, const MachineBasicBlock *MBB,
bool t) {
OS << "BB#" << MBB->getNumber();
diff --git a/lib/CodeGen/MachineBranchProbabilityInfo.cpp b/lib/CodeGen/MachineBranchProbabilityInfo.cpp
new file mode 100644
index 0000000..c13fa6b
--- /dev/null
+++ b/lib/CodeGen/MachineBranchProbabilityInfo.cpp
@@ -0,0 +1,113 @@
+//===- MachineBranchProbabilityInfo.cpp - Machine Branch Probability Info -===//
+//
+// The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// This analysis uses probability info stored in Machine Basic Blocks.
+//
+//===----------------------------------------------------------------------===//
+
+#include "llvm/Instructions.h"
+#include "llvm/CodeGen/MachineBranchProbabilityInfo.h"
+#include "llvm/CodeGen/MachineBasicBlock.h"
+#include "llvm/Support/Debug.h"
+#include "llvm/Support/raw_ostream.h"
+
+using namespace llvm;
+
+INITIALIZE_PASS_BEGIN(MachineBranchProbabilityInfo, "machine-branch-prob",
+ "Machine Branch Probability Analysis", false, true)
+INITIALIZE_PASS_END(MachineBranchProbabilityInfo, "machine-branch-prob",
+ "Machine Branch Probability Analysis", false, true)
+
+char MachineBranchProbabilityInfo::ID = 0;
+
+uint32_t MachineBranchProbabilityInfo::
+getSumForBlock(MachineBasicBlock *MBB) const {
+ uint32_t Sum = 0;
+
+ for (MachineBasicBlock::const_succ_iterator I = MBB->succ_begin(),
+ E = MBB->succ_end(); I != E; ++I) {
+ MachineBasicBlock *Succ = *I;
+ uint32_t Weight = getEdgeWeight(MBB, Succ);
+ uint32_t PrevSum = Sum;
+
+ Sum += Weight;
+ assert(Sum > PrevSum); (void) PrevSum;
+ }
+
+ return Sum;
+}
+
+uint32_t
+MachineBranchProbabilityInfo::getEdgeWeight(MachineBasicBlock *Src,
+ MachineBasicBlock *Dst) const {
+ uint32_t Weight = Src->getSuccWeight(Dst);
+ if (!Weight)
+ return DEFAULT_WEIGHT;
+ return Weight;
+}
+
+bool MachineBranchProbabilityInfo::isEdgeHot(MachineBasicBlock *Src,
+ MachineBasicBlock *Dst) const {
+ // Hot probability is at least 4/5 = 80%
+ uint32_t Weight = getEdgeWeight(Src, Dst);
+ uint32_t Sum = getSumForBlock(Src);
+
+ // FIXME: Implement BranchProbability::compare then change this code to
+ // compare this BranchProbability against a static "hot" BranchProbability.
+ return (uint64_t)Weight * 5 > (uint64_t)Sum * 4;
+}
+
+MachineBasicBlock *
+MachineBranchProbabilityInfo::getHotSucc(MachineBasicBlock *MBB) const {
+ uint32_t Sum = 0;
+ uint32_t MaxWeight = 0;
+ MachineBasicBlock *MaxSucc = 0;
+
+ for (MachineBasicBlock::const_succ_iterator I = MBB->succ_begin(),
+ E = MBB->succ_end(); I != E; ++I) {
+ MachineBasicBlock *Succ = *I;
+ uint32_t Weight = getEdgeWeight(MBB, Succ);
+ uint32_t PrevSum = Sum;
+
+ Sum += Weight;
+ assert(Sum > PrevSum); (void) PrevSum;
+
+ if (Weight > MaxWeight) {
+ MaxWeight = Weight;
+ MaxSucc = Succ;
+ }
+ }
+
+ // FIXME: Use BranchProbability::compare.
+ if ((uint64_t)MaxWeight * 5 >= (uint64_t)Sum * 4)
+ return MaxSucc;
+
+ return 0;
+}
+
+BranchProbability
+MachineBranchProbabilityInfo::getEdgeProbability(MachineBasicBlock *Src,
+ MachineBasicBlock *Dst) const {
+ uint32_t N = getEdgeWeight(Src, Dst);
+ uint32_t D = getSumForBlock(Src);
+
+ return BranchProbability(N, D);
+}
+
+raw_ostream &MachineBranchProbabilityInfo::
+printEdgeProbability(raw_ostream &OS, MachineBasicBlock *Src,
+ MachineBasicBlock *Dst) const {
+
+ const BranchProbability Prob = getEdgeProbability(Src, Dst);
+ OS << "edge MBB#" << Src->getNumber() << " -> MBB#" << Dst->getNumber()
+ << " probability is " << Prob
+ << (isEdgeHot(Src, Dst) ? " [HOT edge]\n" : "\n");
+
+ return OS;
+}
diff --git a/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp b/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
index 4e19d2b..d79a5ae 100644
--- a/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
+++ b/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
@@ -1279,6 +1279,24 @@
return true;
}
+/// Return branch probability calculated by BranchProbabilityInfo for IR blocks.
+uint32_t SelectionDAGBuilder::getEdgeWeight(MachineBasicBlock *Src,
+ MachineBasicBlock *Dst) {
+ BranchProbabilityInfo *BPI = FuncInfo.BPI;
+ if (!BPI)
+ return 0;
+ BasicBlock *SrcBB = const_cast<BasicBlock*>(Src->getBasicBlock());
+ BasicBlock *DstBB = const_cast<BasicBlock*>(Dst->getBasicBlock());
+ return BPI->getEdgeWeight(SrcBB, DstBB);
+}
+
+void SelectionDAGBuilder::addSuccessorWithWeight(MachineBasicBlock *Src,
+ MachineBasicBlock *Dst) {
+ uint32_t weight = getEdgeWeight(Src, Dst);
+ Src->addSuccessor(Dst, weight);
+}
+
+
static bool InBlock(const Value *V, const BasicBlock *BB) {
if (const Instruction *I = dyn_cast<Instruction>(V))
return I->getParent() == BB;
@@ -1548,8 +1566,8 @@
}
// Update successor info
- SwitchBB->addSuccessor(CB.TrueBB);
- SwitchBB->addSuccessor(CB.FalseBB);
+ addSuccessorWithWeight(SwitchBB, CB.TrueBB);
+ addSuccessorWithWeight(SwitchBB, CB.FalseBB);
// Set NextBlock to be the MBB immediately after the current one, if any.
// This is used to avoid emitting unnecessary branches to the next block.
@@ -1693,8 +1711,8 @@
MachineBasicBlock* MBB = B.Cases[0].ThisBB;
- SwitchBB->addSuccessor(B.Default);
- SwitchBB->addSuccessor(MBB);
+ addSuccessorWithWeight(SwitchBB, B.Default);
+ addSuccessorWithWeight(SwitchBB, MBB);
SDValue BrRange = DAG.getNode(ISD::BRCOND, getCurDebugLoc(),
MVT::Other, CopyTo, RangeCmp,
@@ -1739,8 +1757,8 @@
ISD::SETNE);
}
- SwitchBB->addSuccessor(B.TargetBB);
- SwitchBB->addSuccessor(NextMBB);
+ addSuccessorWithWeight(SwitchBB, B.TargetBB);
+ addSuccessorWithWeight(SwitchBB, NextMBB);
SDValue BrAnd = DAG.getNode(ISD::BRCOND, getCurDebugLoc(),
MVT::Other, getControlRoot(),
@@ -1980,8 +1998,9 @@
// table.
MachineBasicBlock *JumpTableBB = CurMF->CreateMachineBasicBlock(LLVMBB);
CurMF->insert(BBI, JumpTableBB);
- CR.CaseBB->addSuccessor(Default);
- CR.CaseBB->addSuccessor(JumpTableBB);
+
+ addSuccessorWithWeight(CR.CaseBB, Default);
+ addSuccessorWithWeight(CR.CaseBB, JumpTableBB);
// Build a vector of destination BBs, corresponding to each target
// of the jump table. If the value of the jump table slot corresponds to
@@ -2008,7 +2027,7 @@
E = DestBBs.end(); I != E; ++I) {
if (!SuccsHandled[(*I)->getNumber()]) {
SuccsHandled[(*I)->getNumber()] = true;
- JumpTableBB->addSuccessor(*I);
+ addSuccessorWithWeight(JumpTableBB, *I);
}
}
@@ -2427,8 +2446,10 @@
succs.push_back(I.getSuccessor(i));
array_pod_sort(succs.begin(), succs.end());
succs.erase(std::unique(succs.begin(), succs.end()), succs.end());
- for (unsigned i = 0, e = succs.size(); i != e; ++i)
- IndirectBrMBB->addSuccessor(FuncInfo.MBBMap[succs[i]]);
+ for (unsigned i = 0, e = succs.size(); i != e; ++i) {
+ MachineBasicBlock *Succ = FuncInfo.MBBMap[succs[i]];
+ addSuccessorWithWeight(IndirectBrMBB, Succ);
+ }
DAG.setRoot(DAG.getNode(ISD::BRIND, getCurDebugLoc(),
MVT::Other, getControlRoot(),
diff --git a/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.h b/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.h
index 8376d41..a1ca891 100644
--- a/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.h
+++ b/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.h
@@ -434,6 +434,9 @@
const Value* SV,
MachineBasicBlock* Default,
MachineBasicBlock *SwitchBB);
+
+ uint32_t getEdgeWeight(MachineBasicBlock *Src, MachineBasicBlock *Dst);
+ void addSuccessorWithWeight(MachineBasicBlock *Src, MachineBasicBlock *Dst);
public:
void visitSwitchCase(CaseBlock &CB,
MachineBasicBlock *SwitchBB);
diff --git a/lib/CodeGen/SelectionDAG/SelectionDAGISel.cpp b/lib/CodeGen/SelectionDAG/SelectionDAGISel.cpp
index 771b008..dc8044b 100644
--- a/lib/CodeGen/SelectionDAG/SelectionDAGISel.cpp
+++ b/lib/CodeGen/SelectionDAG/SelectionDAGISel.cpp
@@ -17,6 +17,7 @@
#include "llvm/CodeGen/FunctionLoweringInfo.h"
#include "llvm/CodeGen/SelectionDAGISel.h"
#include "llvm/Analysis/AliasAnalysis.h"
+#include "llvm/Analysis/BranchProbabilityInfo.h"
#include "llvm/Analysis/DebugInfo.h"
#include "llvm/Constants.h"
#include "llvm/Function.h"
@@ -68,6 +69,11 @@
EnableFastISelAbort("fast-isel-abort", cl::Hidden,
cl::desc("Enable abort calls when \"fast\" instruction fails"));
+static cl::opt<bool>
+UseMBPI("use-mbpi",
+ cl::desc("use Machine Branch Probability Info"),
+ cl::init(true), cl::Hidden);
+
#ifndef NDEBUG
static cl::opt<bool>
ViewDAGCombine1("view-dag-combine1-dags", cl::Hidden,
@@ -186,6 +192,7 @@
DAGSize(0) {
initializeGCModuleInfoPass(*PassRegistry::getPassRegistry());
initializeAliasAnalysisAnalysisGroup(*PassRegistry::getPassRegistry());
+ initializeBranchProbabilityInfoPass(*PassRegistry::getPassRegistry());
}
SelectionDAGISel::~SelectionDAGISel() {
@@ -199,6 +206,8 @@
AU.addPreserved<AliasAnalysis>();
AU.addRequired<GCModuleInfo>();
AU.addPreserved<GCModuleInfo>();
+ if (UseMBPI && OptLevel != CodeGenOpt::None)
+ AU.addRequired<BranchProbabilityInfo>();
MachineFunctionPass::getAnalysisUsage(AU);
}
@@ -262,6 +271,12 @@
CurDAG->init(*MF);
FuncInfo->set(Fn, *MF);
+
+ if (UseMBPI && OptLevel != CodeGenOpt::None)
+ FuncInfo->BPI = &getAnalysis<BranchProbabilityInfo>();
+ else
+ FuncInfo->BPI = 0;
+
SDB->init(GFI, *AA);
SelectAllBasicBlocks(Fn);