#include "llvm/Function.h"
#include "llvm/CodeGen/Passes.h"
#include "llvm/CodeGen/MachineModuleInfo.h"
-#include "llvm/CodeGen/MachineBranchProbabilityInfo.h"
#include "llvm/CodeGen/MachineFunctionPass.h"
+#include "llvm/CodeGen/MachineLoopInfo.h"
#include "llvm/MC/MCInstrItineraries.h"
#include "llvm/Target/TargetInstrInfo.h"
#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"
const TargetInstrInfo *TII;
const TargetRegisterInfo *TRI;
const InstrItineraryData *InstrItins;
- const MachineBranchProbabilityInfo *MBPI;
-
+ const MachineLoopInfo *MLI;
bool MadeChange;
int FnNum;
public:
IfConverter() : MachineFunctionPass(ID), FnNum(-1) {
initializeIfConverterPass(*PassRegistry::getPassRegistry());
}
-
+
virtual void getAnalysisUsage(AnalysisUsage &AU) const {
- AU.addRequired<MachineBranchProbabilityInfo>();
+ AU.addRequired<MachineLoopInfo>();
MachineFunctionPass::getAnalysisUsage(AU);
}
}
INITIALIZE_PASS_BEGIN(IfConverter, "if-converter", "If Converter", false, false)
-INITIALIZE_PASS_DEPENDENCY(MachineBranchProbabilityInfo)
+INITIALIZE_PASS_DEPENDENCY(MachineLoopInfo)
INITIALIZE_PASS_END(IfConverter, "if-converter", "If Converter", false, false)
FunctionPass *llvm::createIfConverterPass() { return new IfConverter(); }
TLI = MF.getTarget().getTargetLowering();
TII = MF.getTarget().getInstrInfo();
TRI = MF.getTarget().getRegisterInfo();
- MBPI = &getAnalysis<MachineBranchProbabilityInfo>();
+ MLI = &getAnalysis<MachineLoopInfo>();
InstrItins = MF.getTarget().getInstrItineraryData();
if (!TII) return false;
bool TNeedSub = TrueBBI.Predicate.size() > 0;
bool FNeedSub = FalseBBI.Predicate.size() > 0;
bool Enqueued = false;
-
- BranchProbability Prediction = MBPI->getEdgeProbability(BB, TrueBBI.BB);
-
+
+ // Try to predict the branch, using loop info to guide us.
+ // General heuristics are:
+ // - backedge -> 90% taken
+ // - early exit -> 20% taken
+ // - branch predictor confidence -> 90%
+ BranchProbability Prediction(5, 10);
+ MachineLoop *Loop = MLI->getLoopFor(BB);
+ if (Loop) {
+ if (TrueBBI.BB == Loop->getHeader())
+ Prediction = BranchProbability(9, 10);
+ else if (FalseBBI.BB == Loop->getHeader())
+ Prediction = BranchProbability(1, 10);
+
+ MachineLoop *TrueLoop = MLI->getLoopFor(TrueBBI.BB);
+ MachineLoop *FalseLoop = MLI->getLoopFor(FalseBBI.BB);
+ if (!TrueLoop || TrueLoop->getParentLoop() == Loop)
+ Prediction = BranchProbability(2, 10);
+ else if (!FalseLoop || FalseLoop->getParentLoop() == Loop)
+ Prediction = BranchProbability(8, 10);
+ }
+
if (CanRevCond && ValidDiamond(TrueBBI, FalseBBI, Dups, Dups2) &&
MeetIfcvtSizeLimit(*TrueBBI.BB, (TrueBBI.NonPredSize - (Dups + Dups2) +
TrueBBI.ExtraCost), TrueBBI.ExtraCost2,