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Use BranchProbability instead of floating points in IfConverter.

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git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@134858 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Jakub Staszak 2011-07-10 02:58:07 +00:00
parent 687dc24e1d
commit f81b7f6069
4 changed files with 59 additions and 51 deletions
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7
include/llvm/Target/TargetInstrInfo.h
View File

@ -32,6 +32,7 @@ class SelectionDAG;
class ScheduleDAG;
class TargetRegisterClass;
class TargetRegisterInfo;
class BranchProbability;
template<class T> class SmallVectorImpl;
@ -321,7 +322,7 @@ public:
virtual
bool isProfitableToIfCvt(MachineBasicBlock &MBB, unsigned NumCyles,
unsigned ExtraPredCycles,
float Probability, float Confidence) const {
const BranchProbability &Probability) const {
return false;
}
@ -336,7 +337,7 @@ public:
unsigned NumTCycles, unsigned ExtraTCycles,
MachineBasicBlock &FMBB,
unsigned NumFCycles, unsigned ExtraFCycles,
float Probability, float Confidence) const {
const BranchProbability &Probability) const {
return false;
}
@ -348,7 +349,7 @@ public:
/// will be properly predicted.
virtual bool
isProfitableToDupForIfCvt(MachineBasicBlock &MBB, unsigned NumCyles,
float Probability, float Confidence) const {
const BranchProbability &Probability) const {
return false;
}

59
lib/CodeGen/IfConversion.cpp
View File

@ -23,6 +23,7 @@
#include "llvm/Target/TargetLowering.h"
#include "llvm/Target/TargetMachine.h"
#include "llvm/Target/TargetRegisterInfo.h"
#include "llvm/Support/BranchProbability.h"
#include "llvm/Support/CommandLine.h"
#include "llvm/Support/Debug.h"
#include "llvm/Support/ErrorHandling.h"
@ -173,10 +174,10 @@ namespace {
private:
bool ReverseBranchCondition(BBInfo &BBI);
bool ValidSimple(BBInfo &TrueBBI, unsigned &Dups,
float Prediction, float Confidence) const;
const BranchProbability &Prediction) const;
bool ValidTriangle(BBInfo &TrueBBI, BBInfo &FalseBBI,
bool FalseBranch, unsigned &Dups,
float Prediction, float Confidence) const;
const BranchProbability &Prediction) const;
bool ValidDiamond(BBInfo &TrueBBI, BBInfo &FalseBBI,
unsigned &Dups1, unsigned &Dups2) const;
void ScanInstructions(BBInfo &BBI);
@ -203,19 +204,19 @@ namespace {
bool MeetIfcvtSizeLimit(MachineBasicBlock &BB,
unsigned Cycle, unsigned Extra,
float Prediction, float Confidence) const {
const BranchProbability &Prediction) const {
return Cycle > 0 && TII->isProfitableToIfCvt(BB, Cycle, Extra,
Prediction, Confidence);
Prediction);
}
bool MeetIfcvtSizeLimit(MachineBasicBlock &TBB,
unsigned TCycle, unsigned TExtra,
MachineBasicBlock &FBB,
unsigned FCycle, unsigned FExtra,
float Prediction, float Confidence) const {
const BranchProbability &Prediction) const {
return TCycle > 0 && FCycle > 0 &&
TII->isProfitableToIfCvt(TBB, TCycle, TExtra, FBB, FCycle, FExtra,
Prediction, Confidence);
Prediction);
}
// blockAlwaysFallThrough - Block ends without a terminator.
@ -450,7 +451,7 @@ static inline MachineBasicBlock *getNextBlock(MachineBasicBlock *BB) {
/// number of instructions that the ifcvt would need to duplicate if performed
/// in Dups.
bool IfConverter::ValidSimple(BBInfo &TrueBBI, unsigned &Dups,
float Prediction, float Confidence) const {
const BranchProbability &Prediction) const {
Dups = 0;
if (TrueBBI.IsBeingAnalyzed || TrueBBI.IsDone)
return false;
@ -461,7 +462,7 @@ bool IfConverter::ValidSimple(BBInfo &TrueBBI, unsigned &Dups,
if (TrueBBI.BB->pred_size() > 1) {
if (TrueBBI.CannotBeCopied ||
!TII->isProfitableToDupForIfCvt(*TrueBBI.BB, TrueBBI.NonPredSize,
Prediction, Confidence))
Prediction))
return false;
Dups = TrueBBI.NonPredSize;
}
@ -477,7 +478,7 @@ bool IfConverter::ValidSimple(BBInfo &TrueBBI, unsigned &Dups,
/// if performed in 'Dups'.
bool IfConverter::ValidTriangle(BBInfo &TrueBBI, BBInfo &FalseBBI,
bool FalseBranch, unsigned &Dups,
float Prediction, float Confidence) const {
const BranchProbability &Prediction) const {
Dups = 0;
if (TrueBBI.IsBeingAnalyzed || TrueBBI.IsDone)
return false;
@ -499,8 +500,7 @@ bool IfConverter::ValidTriangle(BBInfo &TrueBBI, BBInfo &FalseBBI,
++Size;
}
}
if (!TII->isProfitableToDupForIfCvt(*TrueBBI.BB, Size,
Prediction, Confidence))
if (!TII->isProfitableToDupForIfCvt(*TrueBBI.BB, Size, Prediction))
return false;
Dups = Size;
}
@ -796,21 +796,20 @@ IfConverter::BBInfo &IfConverter::AnalyzeBlock(MachineBasicBlock *BB,
// - backedge -> 90% taken
// - early exit -> 20% taken
// - branch predictor confidence -> 90%
float Prediction = 0.5f;
float Confidence = 0.9f;
BranchProbability Prediction(5, 10);
MachineLoop *Loop = MLI->getLoopFor(BB);
if (Loop) {
if (TrueBBI.BB == Loop->getHeader())
Prediction = 0.9f;
Prediction = BranchProbability(9, 10);
else if (FalseBBI.BB == Loop->getHeader())
Prediction = 0.1f;
Prediction = BranchProbability(1, 10);
MachineLoop *TrueLoop = MLI->getLoopFor(TrueBBI.BB);
MachineLoop *FalseLoop = MLI->getLoopFor(FalseBBI.BB);
if (!TrueLoop || TrueLoop->getParentLoop() == Loop)
Prediction = 0.2f;
Prediction = BranchProbability(2, 10);
else if (!FalseLoop || FalseLoop->getParentLoop() == Loop)
Prediction = 0.8f;
Prediction = BranchProbability(8, 10);
}
if (CanRevCond && ValidDiamond(TrueBBI, FalseBBI, Dups, Dups2) &&
@ -818,7 +817,7 @@ IfConverter::BBInfo &IfConverter::AnalyzeBlock(MachineBasicBlock *BB,
TrueBBI.ExtraCost), TrueBBI.ExtraCost2,
*FalseBBI.BB, (FalseBBI.NonPredSize - (Dups + Dups2) +
FalseBBI.ExtraCost),FalseBBI.ExtraCost2,
Prediction, Confidence) &&
Prediction) &&
FeasibilityAnalysis(TrueBBI, BBI.BrCond) &&
FeasibilityAnalysis(FalseBBI, RevCond)) {
// Diamond:
@ -834,9 +833,9 @@ IfConverter::BBInfo &IfConverter::AnalyzeBlock(MachineBasicBlock *BB,
Enqueued = true;
}
if (ValidTriangle(TrueBBI, FalseBBI, false, Dups, Prediction, Confidence) &&
if (ValidTriangle(TrueBBI, FalseBBI, false, Dups, Prediction) &&
MeetIfcvtSizeLimit(*TrueBBI.BB, TrueBBI.NonPredSize + TrueBBI.ExtraCost,
TrueBBI.ExtraCost2, Prediction, Confidence) &&
TrueBBI.ExtraCost2, Prediction) &&
FeasibilityAnalysis(TrueBBI, BBI.BrCond, true)) {
// Triangle:
// EBB
@ -849,17 +848,17 @@ IfConverter::BBInfo &IfConverter::AnalyzeBlock(MachineBasicBlock *BB,
Enqueued = true;
}
if (ValidTriangle(TrueBBI, FalseBBI, true, Dups, Prediction, Confidence) &&
if (ValidTriangle(TrueBBI, FalseBBI, true, Dups, Prediction) &&
MeetIfcvtSizeLimit(*TrueBBI.BB, TrueBBI.NonPredSize + TrueBBI.ExtraCost,
TrueBBI.ExtraCost2, Prediction, Confidence) &&
TrueBBI.ExtraCost2, Prediction) &&
FeasibilityAnalysis(TrueBBI, BBI.BrCond, true, true)) {
Tokens.push_back(new IfcvtToken(BBI, ICTriangleRev, TNeedSub, Dups));
Enqueued = true;
}
if (ValidSimple(TrueBBI, Dups, Prediction, Confidence) &&
if (ValidSimple(TrueBBI, Dups, Prediction) &&
MeetIfcvtSizeLimit(*TrueBBI.BB, TrueBBI.NonPredSize + TrueBBI.ExtraCost,
TrueBBI.ExtraCost2, Prediction, Confidence) &&
TrueBBI.ExtraCost2, Prediction) &&
FeasibilityAnalysis(TrueBBI, BBI.BrCond)) {
// Simple (split, no rejoin):
// EBB
@ -875,29 +874,29 @@ IfConverter::BBInfo &IfConverter::AnalyzeBlock(MachineBasicBlock *BB,
if (CanRevCond) {
// Try the other path...
if (ValidTriangle(FalseBBI, TrueBBI, false, Dups,
1.0-Prediction, Confidence) &&
Prediction.getCompl()) &&
MeetIfcvtSizeLimit(*FalseBBI.BB,
FalseBBI.NonPredSize + FalseBBI.ExtraCost,
FalseBBI.ExtraCost2, 1.0-Prediction, Confidence) &&
FalseBBI.ExtraCost2, Prediction.getCompl()) &&
FeasibilityAnalysis(FalseBBI, RevCond, true)) {
Tokens.push_back(new IfcvtToken(BBI, ICTriangleFalse, FNeedSub, Dups));
Enqueued = true;
}
if (ValidTriangle(FalseBBI, TrueBBI, true, Dups,
1.0-Prediction, Confidence) &&
Prediction.getCompl()) &&
MeetIfcvtSizeLimit(*FalseBBI.BB,
FalseBBI.NonPredSize + FalseBBI.ExtraCost,
FalseBBI.ExtraCost2, 1.0-Prediction, Confidence) &&
FalseBBI.ExtraCost2, Prediction.getCompl()) &&
FeasibilityAnalysis(FalseBBI, RevCond, true, true)) {
Tokens.push_back(new IfcvtToken(BBI, ICTriangleFRev, FNeedSub, Dups));
Enqueued = true;
}
if (ValidSimple(FalseBBI, Dups, 1.0-Prediction, Confidence) &&
if (ValidSimple(FalseBBI, Dups, Prediction.getCompl()) &&
MeetIfcvtSizeLimit(*FalseBBI.BB,
FalseBBI.NonPredSize + FalseBBI.ExtraCost,
FalseBBI.ExtraCost2, 1.0-Prediction, Confidence) &&
FalseBBI.ExtraCost2, Prediction.getCompl()) &&
FeasibilityAnalysis(FalseBBI, RevCond)) {
Tokens.push_back(new IfcvtToken(BBI, ICSimpleFalse, FNeedSub, Dups));
Enqueued = true;

36
lib/Target/ARM/ARMBaseInstrInfo.cpp
View File

@ -30,6 +30,7 @@
#include "llvm/CodeGen/MachineRegisterInfo.h"
#include "llvm/CodeGen/PseudoSourceValue.h"
#include "llvm/MC/MCAsmInfo.h"
#include "llvm/Support/BranchProbability.h"
#include "llvm/Support/CommandLine.h"
#include "llvm/Support/Debug.h"
#include "llvm/Support/ErrorHandling.h"
@ -1273,20 +1274,20 @@ bool ARMBaseInstrInfo::isSchedulingBoundary(const MachineInstr *MI,
return false;
}
bool ARMBaseInstrInfo::isProfitableToIfCvt(MachineBasicBlock &MBB,
unsigned NumCycles,
unsigned ExtraPredCycles,
float Probability,
float Confidence) const {
bool ARMBaseInstrInfo::
isProfitableToIfCvt(MachineBasicBlock &MBB,
unsigned NumCycles, unsigned ExtraPredCycles,
const BranchProbability &Probability) const {
if (!NumCycles)
return false;
// Attempt to estimate the relative costs of predication versus branching.
float UnpredCost = Probability * NumCycles;
UnpredCost += 1.0; // The branch itself
UnpredCost += (1.0 - Confidence) * Subtarget.getMispredictionPenalty();
unsigned UnpredCost = Probability.getNumerator() * NumCycles;
UnpredCost /= Probability.getDenominator();
UnpredCost += 1; // The branch itself
UnpredCost += Subtarget.getMispredictionPenalty() / 10;
return (float)(NumCycles + ExtraPredCycles) < UnpredCost;
return (NumCycles + ExtraPredCycles) <= UnpredCost;
}
bool ARMBaseInstrInfo::
@ -1294,16 +1295,23 @@ isProfitableToIfCvt(MachineBasicBlock &TMBB,
unsigned TCycles, unsigned TExtra,
MachineBasicBlock &FMBB,
unsigned FCycles, unsigned FExtra,
float Probability, float Confidence) const {
const BranchProbability &Probability) const {
if (!TCycles || !FCycles)
return false;
// Attempt to estimate the relative costs of predication versus branching.
float UnpredCost = Probability * TCycles + (1.0 - Probability) * FCycles;
UnpredCost += 1.0; // The branch itself
UnpredCost += (1.0 - Confidence) * Subtarget.getMispredictionPenalty();
unsigned TUnpredCost = Probability.getNumerator() * TCycles;
TUnpredCost /= Probability.getDenominator();
uint32_t Comp = Probability.getDenominator() - Probability.getNumerator();
unsigned FUnpredCost = Comp * FCycles;
FUnpredCost /= Probability.getDenominator();
return (float)(TCycles + FCycles + TExtra + FExtra) < UnpredCost;
unsigned UnpredCost = TUnpredCost + FUnpredCost;
UnpredCost += 1; // The branch itself
UnpredCost += Subtarget.getMispredictionPenalty() / 10;
return (TCycles + FCycles + TExtra + FExtra) <= UnpredCost;
}
/// getInstrPredicate - If instruction is predicated, returns its predicate

8
lib/Target/ARM/ARMBaseInstrInfo.h
View File

@ -311,18 +311,18 @@ public:
virtual bool isProfitableToIfCvt(MachineBasicBlock &MBB,
unsigned NumCycles, unsigned ExtraPredCycles,
float Prob, float Confidence) const;
const BranchProbability &Probability) const;
virtual bool isProfitableToIfCvt(MachineBasicBlock &TMBB,
unsigned NumT, unsigned ExtraT,
MachineBasicBlock &FMBB,
unsigned NumF, unsigned ExtraF,
float Probability, float Confidence) const;
const BranchProbability &Probability) const;
virtual bool isProfitableToDupForIfCvt(MachineBasicBlock &MBB,
unsigned NumCycles,
float Probability,
float Confidence) const {
const BranchProbability
&Probability) const {
return NumCycles == 1;
}