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Start implementing pre-ra if-converter: using speculation and selects to eliminate branches.

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llvm-svn: 158234
This commit is contained in:
Evan Cheng 2012-06-08 21:53:50 +00:00
parent 151209d9dc
commit 287aa9fb18
1 changed files with 15 additions and 6 deletions
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17
lib/CodeGen/IfConversion.cpp
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@ -18,6 +18,7 @@
#include "llvm/CodeGen/MachineModuleInfo.h"
#include "llvm/CodeGen/MachineBranchProbabilityInfo.h"
#include "llvm/CodeGen/MachineFunctionPass.h"
#include "llvm/CodeGen/MachineRegisterInfo.h"
#include "llvm/MC/MCInstrItineraries.h"
#include "llvm/Target/TargetInstrInfo.h"
#include "llvm/Target/TargetLowering.h"
@ -155,7 +156,9 @@ namespace {
const TargetRegisterInfo *TRI;
const InstrItineraryData *InstrItins;
const MachineBranchProbabilityInfo *MBPI;
MachineRegisterInfo *MRI;
bool PreRegAlloc;
bool MadeChange;
int FnNum;
public:
@ -263,14 +266,20 @@ bool IfConverter::runOnMachineFunction(MachineFunction &MF) {
TII = MF.getTarget().getInstrInfo();
TRI = MF.getTarget().getRegisterInfo();
MBPI = &getAnalysis<MachineBranchProbabilityInfo>();
MRI = &MF.getRegInfo();
InstrItins = MF.getTarget().getInstrItineraryData();
if (!TII) return false;
PreRegAlloc = MRI->isSSA();
bool BFChange = false;
if (!PreRegAlloc) {
// Tail merge tend to expose more if-conversion opportunities.
BranchFolder BF(true, false);
bool BFChange = BF.OptimizeFunction(MF, TII,
BFChange = BF.OptimizeFunction(MF, TII,
MF.getTarget().getRegisterInfo(),
getAnalysisIfAvailable<MachineModuleInfo>());
}
DEBUG(dbgs() << "\nIfcvt: function (" << ++FnNum << ") \'"
<< MF.getFunction()->getName() << "\'");
@ -621,7 +630,7 @@ void IfConverter::ScanInstructions(BBInfo &BBI) {
if (BBI.IsDone)
return;
bool AlreadyPredicated = BBI.Predicate.size() > 0;
bool AlreadyPredicated = !BBI.Predicate.empty();
// First analyze the end of BB branches.
BBI.TrueBB = BBI.FalseBB = NULL;
BBI.BrCond.clear();
@ -786,8 +795,8 @@ IfConverter::BBInfo &IfConverter::AnalyzeBlock(MachineBasicBlock *BB,
unsigned Dups = 0;
unsigned Dups2 = 0;
bool TNeedSub = TrueBBI.Predicate.size() > 0;
bool FNeedSub = FalseBBI.Predicate.size() > 0;
bool TNeedSub = !TrueBBI.Predicate.empty();
bool FNeedSub = !FalseBBI.Predicate.empty();
bool Enqueued = false;
BranchProbability Prediction = MBPI->getEdgeProbability(BB, TrueBBI.BB);