//
// The LLVM Compiler Infrastructure
//
-// This file was developed by the Evan Cheng and is distributed under
-// the University of Illinois Open Source License. See LICENSE.TXT for details.
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
//
//===----------------------------------------------------------------------===//
-#define DEBUG_TYPE "ifconversion"
+#define DEBUG_TYPE "ifcvt"
+#include "llvm/Function.h"
#include "llvm/CodeGen/Passes.h"
#include "llvm/CodeGen/MachineModuleInfo.h"
#include "llvm/CodeGen/MachineFunctionPass.h"
#include "llvm/Target/TargetInstrInfo.h"
#include "llvm/Target/TargetLowering.h"
#include "llvm/Target/TargetMachine.h"
+#include "llvm/Support/CommandLine.h"
#include "llvm/Support/Debug.h"
+#include "llvm/ADT/DepthFirstIterator.h"
#include "llvm/ADT/Statistic.h"
+#include "llvm/ADT/STLExtras.h"
using namespace llvm;
-STATISTIC(NumIfConvBBs, "Number of if-converted blocks");
+// Hidden options for help debugging.
+static cl::opt<int> IfCvtFnStart("ifcvt-fn-start", cl::init(-1), cl::Hidden);
+static cl::opt<int> IfCvtFnStop("ifcvt-fn-stop", cl::init(-1), cl::Hidden);
+static cl::opt<int> IfCvtLimit("ifcvt-limit", cl::init(-1), cl::Hidden);
+static cl::opt<bool> DisableSimple("disable-ifcvt-simple",
+ cl::init(false), cl::Hidden);
+static cl::opt<bool> DisableSimpleF("disable-ifcvt-simple-false",
+ cl::init(false), cl::Hidden);
+static cl::opt<bool> DisableTriangle("disable-ifcvt-triangle",
+ cl::init(false), cl::Hidden);
+static cl::opt<bool> DisableTriangleR("disable-ifcvt-triangle-rev",
+ cl::init(false), cl::Hidden);
+static cl::opt<bool> DisableTriangleF("disable-ifcvt-triangle-false",
+ cl::init(false), cl::Hidden);
+static cl::opt<bool> DisableTriangleFR("disable-ifcvt-triangle-false-rev",
+ cl::init(false), cl::Hidden);
+static cl::opt<bool> DisableDiamond("disable-ifcvt-diamond",
+ cl::init(false), cl::Hidden);
+
+STATISTIC(NumSimple, "Number of simple if-conversions performed");
+STATISTIC(NumSimpleFalse, "Number of simple (F) if-conversions performed");
+STATISTIC(NumTriangle, "Number of triangle if-conversions performed");
+STATISTIC(NumTriangleRev, "Number of triangle (R) if-conversions performed");
+STATISTIC(NumTriangleFalse,"Number of triangle (F) if-conversions performed");
+STATISTIC(NumTriangleFRev, "Number of triangle (F/R) if-conversions performed");
+STATISTIC(NumDiamonds, "Number of diamond if-conversions performed");
+STATISTIC(NumIfConvBBs, "Number of if-converted blocks");
+STATISTIC(NumDupBBs, "Number of duplicated blocks");
namespace {
- class IfConverter : public MachineFunctionPass {
- enum BBICKind {
- ICInvalid, // BB data invalid.
+ class VISIBILITY_HIDDEN IfConverter : public MachineFunctionPass {
+ enum IfcvtKind {
ICNotClassfied, // BB data valid, but not classified.
- ICTriangle, // BB is part of a triangle sub-CFG.
- ICDiamond, // BB is part of a diamond sub-CFG.
- ICTriangleEntry, // BB is entry of a triangle sub-CFG.
- ICDiamondEntry // BB is entry of a diamond sub-CFG.
+ ICSimpleFalse, // Same as ICSimple, but on the false path.
+ ICSimple, // BB is entry of an one split, no rejoin sub-CFG.
+ ICTriangleFRev, // Same as ICTriangleFalse, but false path rev condition.
+ ICTriangleRev, // Same as ICTriangle, but true path rev condition.
+ ICTriangleFalse, // Same as ICTriangle, but on the false path.
+ ICTriangle, // BB is entry of a triangle sub-CFG.
+ ICDiamond // BB is entry of a diamond sub-CFG.
};
/// BBInfo - One per MachineBasicBlock, this is used to cache the result
/// if-conversion feasibility analysis. This includes results from
/// TargetInstrInfo::AnalyzeBranch() (i.e. TBB, FBB, and Cond), and its
/// classification, and common tail block of its successors (if it's a
- /// diamond shape).
+ /// diamond shape), its size, whether it's predicable, and whether any
+ /// instruction can clobber the 'would-be' predicate.
+ ///
+ /// IsDone - True if BB is not to be considered for ifcvt.
+ /// IsBeingAnalyzed - True if BB is currently being analyzed.
+ /// IsAnalyzed - True if BB has been analyzed (info is still valid).
+ /// IsEnqueued - True if BB has been enqueued to be ifcvt'ed.
+ /// IsBrAnalyzable - True if AnalyzeBranch() returns false.
+ /// HasFallThrough - True if BB may fallthrough to the following BB.
+ /// IsUnpredicable - True if BB is known to be unpredicable.
+ /// ClobbersPred - True if BB could modify predicates (e.g. has
+ /// cmp, call, etc.)
+ /// NonPredSize - Number of non-predicated instructions.
+ /// BB - Corresponding MachineBasicBlock.
+ /// TrueBB / FalseBB- See AnalyzeBranch().
+ /// BrCond - Conditions for end of block conditional branches.
+ /// Predicate - Predicate used in the BB.
struct BBInfo {
- BBICKind Kind;
+ bool IsDone : 1;
+ bool IsBeingAnalyzed : 1;
+ bool IsAnalyzed : 1;
+ bool IsEnqueued : 1;
+ bool IsBrAnalyzable : 1;
+ bool HasFallThrough : 1;
+ bool IsUnpredicable : 1;
+ bool CannotBeCopied : 1;
+ bool ClobbersPred : 1;
+ unsigned NonPredSize;
MachineBasicBlock *BB;
MachineBasicBlock *TrueBB;
MachineBasicBlock *FalseBB;
- MachineBasicBlock *TailBB;
- std::vector<MachineOperand> Cond;
- unsigned Size;
- BBInfo() : Kind(ICInvalid), BB(0), TrueBB(0), FalseBB(0), TailBB(0), Size(0) {}
+ SmallVector<MachineOperand, 4> BrCond;
+ SmallVector<MachineOperand, 4> Predicate;
+ BBInfo() : IsDone(false), IsBeingAnalyzed(false),
+ IsAnalyzed(false), IsEnqueued(false), IsBrAnalyzable(false),
+ HasFallThrough(false), IsUnpredicable(false),
+ CannotBeCopied(false), ClobbersPred(false), NonPredSize(0),
+ BB(0), TrueBB(0), FalseBB(0) {}
+ };
+
+ /// IfcvtToken - Record information about pending if-conversions to attemp:
+ /// BBI - Corresponding BBInfo.
+ /// Kind - Type of block. See IfcvtKind.
+ /// NeedSubsumption - True if the to-be-predicated BB has already been
+ /// predicated.
+ /// NumDups - Number of instructions that would be duplicated due
+ /// to this if-conversion. (For diamonds, the number of
+ /// identical instructions at the beginnings of both
+ /// paths).
+ /// NumDups2 - For diamonds, the number of identical instructions
+ /// at the ends of both paths.
+ struct IfcvtToken {
+ BBInfo &BBI;
+ IfcvtKind Kind;
+ bool NeedSubsumption;
+ unsigned NumDups;
+ unsigned NumDups2;
+ IfcvtToken(BBInfo &b, IfcvtKind k, bool s, unsigned d, unsigned d2 = 0)
+ : BBI(b), Kind(k), NeedSubsumption(s), NumDups(d), NumDups2(d2) {}
};
+ /// Roots - Basic blocks that do not have successors. These are the starting
+ /// points of Graph traversal.
+ std::vector<MachineBasicBlock*> Roots;
+
/// BBAnalysis - Results of if-conversion feasibility analysis indexed by
/// basic block number.
std::vector<BBInfo> BBAnalysis;
bool MadeChange;
public:
static char ID;
- IfConverter() : MachineFunctionPass((intptr_t)&ID) {}
+ IfConverter() : MachineFunctionPass(&ID) {}
virtual bool runOnMachineFunction(MachineFunction &MF);
- virtual const char *getPassName() const { return "If converter"; }
+ virtual const char *getPassName() const { return "If Converter"; }
private:
- void AnalyzeBlock(MachineBasicBlock *BB);
- void InitialFunctionAnalysis(MachineFunction &MF,
- std::vector<int> &Candidates);
- bool IfConvertDiamond(BBInfo &BBI);
- bool IfConvertTriangle(BBInfo &BBI);
- bool isBlockPredicable(MachineBasicBlock *BB) const;
- void PredicateBlock(MachineBasicBlock *BB,
- std::vector<MachineOperand> &Cond,
- bool IgnoreTerm = false);
- void MergeBlocks(BBInfo &TrueBBI, BBInfo &FalseBBI);
+ bool ReverseBranchCondition(BBInfo &BBI);
+ bool ValidSimple(BBInfo &TrueBBI, unsigned &Dups) const;
+ bool ValidTriangle(BBInfo &TrueBBI, BBInfo &FalseBBI,
+ bool FalseBranch, unsigned &Dups) const;
+ bool ValidDiamond(BBInfo &TrueBBI, BBInfo &FalseBBI,
+ unsigned &Dups1, unsigned &Dups2) const;
+ void ScanInstructions(BBInfo &BBI);
+ BBInfo &AnalyzeBlock(MachineBasicBlock *BB,
+ std::vector<IfcvtToken*> &Tokens);
+ bool FeasibilityAnalysis(BBInfo &BBI, SmallVectorImpl<MachineOperand> &Cond,
+ bool isTriangle = false, bool RevBranch = false);
+ bool AnalyzeBlocks(MachineFunction &MF,
+ std::vector<IfcvtToken*> &Tokens);
+ void InvalidatePreds(MachineBasicBlock *BB);
+ void RemoveExtraEdges(BBInfo &BBI);
+ bool IfConvertSimple(BBInfo &BBI, IfcvtKind Kind);
+ bool IfConvertTriangle(BBInfo &BBI, IfcvtKind Kind);
+ bool IfConvertDiamond(BBInfo &BBI, IfcvtKind Kind,
+ unsigned NumDups1, unsigned NumDups2);
+ void PredicateBlock(BBInfo &BBI,
+ MachineBasicBlock::iterator E,
+ SmallVectorImpl<MachineOperand> &Cond);
+ void CopyAndPredicateBlock(BBInfo &ToBBI, BBInfo &FromBBI,
+ SmallVectorImpl<MachineOperand> &Cond,
+ bool IgnoreBr = false);
+ void MergeBlocks(BBInfo &ToBBI, BBInfo &FromBBI);
+
+ bool MeetIfcvtSizeLimit(unsigned Size) const {
+ return Size > 0 && Size <= TLI->getIfCvtBlockSizeLimit();
+ }
+
+ // blockAlwaysFallThrough - Block ends without a terminator.
+ bool blockAlwaysFallThrough(BBInfo &BBI) const {
+ return BBI.IsBrAnalyzable && BBI.TrueBB == NULL;
+ }
+
+ // IfcvtTokenCmp - Used to sort if-conversion candidates.
+ static bool IfcvtTokenCmp(IfcvtToken *C1, IfcvtToken *C2) {
+ int Incr1 = (C1->Kind == ICDiamond)
+ ? -(int)(C1->NumDups + C1->NumDups2) : (int)C1->NumDups;
+ int Incr2 = (C2->Kind == ICDiamond)
+ ? -(int)(C2->NumDups + C2->NumDups2) : (int)C2->NumDups;
+ if (Incr1 > Incr2)
+ return true;
+ else if (Incr1 == Incr2) {
+ // Favors subsumption.
+ if (C1->NeedSubsumption == false && C2->NeedSubsumption == true)
+ return true;
+ else if (C1->NeedSubsumption == C2->NeedSubsumption) {
+ // Favors diamond over triangle, etc.
+ if ((unsigned)C1->Kind < (unsigned)C2->Kind)
+ return true;
+ else if (C1->Kind == C2->Kind)
+ return C1->BBI.BB->getNumber() < C2->BBI.BB->getNumber();
+ }
+ }
+ return false;
+ }
};
+
char IfConverter::ID = 0;
}
+static RegisterPass<IfConverter>
+X("if-converter", "If Converter");
+
FunctionPass *llvm::createIfConverterPass() { return new IfConverter(); }
bool IfConverter::runOnMachineFunction(MachineFunction &MF) {
TII = MF.getTarget().getInstrInfo();
if (!TII) return false;
- MadeChange = false;
+ static int FnNum = -1;
+ DOUT << "\nIfcvt: function (" << ++FnNum << ") \'"
+ << MF.getFunction()->getName() << "\'";
+
+ if (FnNum < IfCvtFnStart || (IfCvtFnStop != -1 && FnNum > IfCvtFnStop)) {
+ DOUT << " skipped\n";
+ return false;
+ }
+ DOUT << "\n";
MF.RenumberBlocks();
- unsigned NumBBs = MF.getNumBlockIDs();
- BBAnalysis.resize(NumBBs);
-
- std::vector<int> Candidates;
- // Do an intial analysis for each basic block and finding all the potential
- // candidates to perform if-convesion.
- InitialFunctionAnalysis(MF, Candidates);
-
- for (unsigned i = 0, e = Candidates.size(); i != e; ++i) {
- BBInfo &BBI = BBAnalysis[Candidates[i]];
- switch (BBI.Kind) {
- default: assert(false && "Unexpected!");
- break;
- case ICTriangleEntry:
- MadeChange |= IfConvertTriangle(BBI);
- break;
- case ICDiamondEntry:
- MadeChange |= IfConvertDiamond(BBI);
- break;
+ BBAnalysis.resize(MF.getNumBlockIDs());
+
+ // Look for root nodes, i.e. blocks without successors.
+ for (MachineFunction::iterator I = MF.begin(), E = MF.end(); I != E; ++I)
+ if (I->succ_empty())
+ Roots.push_back(I);
+
+ std::vector<IfcvtToken*> Tokens;
+ MadeChange = false;
+ unsigned NumIfCvts = NumSimple + NumSimpleFalse + NumTriangle +
+ NumTriangleRev + NumTriangleFalse + NumTriangleFRev + NumDiamonds;
+ while (IfCvtLimit == -1 || (int)NumIfCvts < IfCvtLimit) {
+ // Do an initial analysis for each basic block and find all the potential
+ // candidates to perform if-conversion.
+ bool Change = AnalyzeBlocks(MF, Tokens);
+ while (!Tokens.empty()) {
+ IfcvtToken *Token = Tokens.back();
+ Tokens.pop_back();
+ BBInfo &BBI = Token->BBI;
+ IfcvtKind Kind = Token->Kind;
+ unsigned NumDups = Token->NumDups;
+ unsigned NumDups2 = Token->NumDups2;
+
+ delete Token;
+
+ // If the block has been evicted out of the queue or it has already been
+ // marked dead (due to it being predicated), then skip it.
+ if (BBI.IsDone)
+ BBI.IsEnqueued = false;
+ if (!BBI.IsEnqueued)
+ continue;
+
+ BBI.IsEnqueued = false;
+
+ bool RetVal = false;
+ switch (Kind) {
+ default: assert(false && "Unexpected!");
+ break;
+ case ICSimple:
+ case ICSimpleFalse: {
+ bool isFalse = Kind == ICSimpleFalse;
+ if ((isFalse && DisableSimpleF) || (!isFalse && DisableSimple)) break;
+ DOUT << "Ifcvt (Simple" << (Kind == ICSimpleFalse ? " false" :"")
+ << "): BB#" << BBI.BB->getNumber() << " ("
+ << ((Kind == ICSimpleFalse)
+ ? BBI.FalseBB->getNumber()
+ : BBI.TrueBB->getNumber()) << ") ";
+ RetVal = IfConvertSimple(BBI, Kind);
+ DOUT << (RetVal ? "succeeded!" : "failed!") << "\n";
+ if (RetVal) {
+ if (isFalse) NumSimpleFalse++;
+ else NumSimple++;
+ }
+ break;
+ }
+ case ICTriangle:
+ case ICTriangleRev:
+ case ICTriangleFalse:
+ case ICTriangleFRev: {
+ bool isFalse = Kind == ICTriangleFalse;
+ bool isRev = (Kind == ICTriangleRev || Kind == ICTriangleFRev);
+ if (DisableTriangle && !isFalse && !isRev) break;
+ if (DisableTriangleR && !isFalse && isRev) break;
+ if (DisableTriangleF && isFalse && !isRev) break;
+ if (DisableTriangleFR && isFalse && isRev) break;
+ DOUT << "Ifcvt (Triangle";
+ if (isFalse)
+ DOUT << " false";
+ if (isRev)
+ DOUT << " rev";
+ DOUT << "): BB#" << BBI.BB->getNumber() << " (T:"
+ << BBI.TrueBB->getNumber() << ",F:"
+ << BBI.FalseBB->getNumber() << ") ";
+ RetVal = IfConvertTriangle(BBI, Kind);
+ DOUT << (RetVal ? "succeeded!" : "failed!") << "\n";
+ if (RetVal) {
+ if (isFalse) {
+ if (isRev) NumTriangleFRev++;
+ else NumTriangleFalse++;
+ } else {
+ if (isRev) NumTriangleRev++;
+ else NumTriangle++;
+ }
+ }
+ break;
+ }
+ case ICDiamond: {
+ if (DisableDiamond) break;
+ DOUT << "Ifcvt (Diamond): BB#" << BBI.BB->getNumber() << " (T:"
+ << BBI.TrueBB->getNumber() << ",F:"
+ << BBI.FalseBB->getNumber() << ") ";
+ RetVal = IfConvertDiamond(BBI, Kind, NumDups, NumDups2);
+ DOUT << (RetVal ? "succeeded!" : "failed!") << "\n";
+ if (RetVal) NumDiamonds++;
+ break;
+ }
+ }
+
+ Change |= RetVal;
+
+ NumIfCvts = NumSimple + NumSimpleFalse + NumTriangle + NumTriangleRev +
+ NumTriangleFalse + NumTriangleFRev + NumDiamonds;
+ if (IfCvtLimit != -1 && (int)NumIfCvts >= IfCvtLimit)
+ break;
}
+
+ if (!Change)
+ break;
+ MadeChange |= Change;
+ }
+
+ // Delete tokens in case of early exit.
+ while (!Tokens.empty()) {
+ IfcvtToken *Token = Tokens.back();
+ Tokens.pop_back();
+ delete Token;
}
+
+ Tokens.clear();
+ Roots.clear();
+ BBAnalysis.clear();
+
return MadeChange;
}
+/// findFalseBlock - BB has a fallthrough. Find its 'false' successor given
+/// its 'true' successor.
static MachineBasicBlock *findFalseBlock(MachineBasicBlock *BB,
MachineBasicBlock *TrueBB) {
for (MachineBasicBlock::succ_iterator SI = BB->succ_begin(),
return NULL;
}
-void IfConverter::AnalyzeBlock(MachineBasicBlock *BB) {
- BBInfo &BBI = BBAnalysis[BB->getNumber()];
+/// ReverseBranchCondition - Reverse the condition of the end of the block
+/// branch. Swap block's 'true' and 'false' successors.
+bool IfConverter::ReverseBranchCondition(BBInfo &BBI) {
+ if (!TII->ReverseBranchCondition(BBI.BrCond)) {
+ TII->RemoveBranch(*BBI.BB);
+ TII->InsertBranch(*BBI.BB, BBI.FalseBB, BBI.TrueBB, BBI.BrCond);
+ std::swap(BBI.TrueBB, BBI.FalseBB);
+ return true;
+ }
+ return false;
+}
- if (BBI.Kind != ICInvalid)
- return; // Always analyzed.
- BBI.BB = BB;
- BBI.Size = std::distance(BB->begin(), BB->end());
+/// getNextBlock - Returns the next block in the function blocks ordering. If
+/// it is the end, returns NULL.
+static inline MachineBasicBlock *getNextBlock(MachineBasicBlock *BB) {
+ MachineFunction::iterator I = BB;
+ MachineFunction::iterator E = BB->getParent()->end();
+ if (++I == E)
+ return NULL;
+ return I;
+}
- // Look for 'root' of a simple (non-nested) triangle or diamond.
- BBI.Kind = ICNotClassfied;
- if (TII->AnalyzeBranch(*BB, BBI.TrueBB, BBI.FalseBB, BBI.Cond)
- || !BBI.TrueBB || BBI.Cond.size() == 0)
- return;
+/// ValidSimple - Returns true if the 'true' block (along with its
+/// predecessor) forms a valid simple shape for ifcvt. It also returns the
+/// number of instructions that the ifcvt would need to duplicate if performed
+/// in Dups.
+bool IfConverter::ValidSimple(BBInfo &TrueBBI, unsigned &Dups) const {
+ Dups = 0;
+ if (TrueBBI.IsBeingAnalyzed || TrueBBI.IsDone)
+ return false;
- // Not a candidate if 'true' block has another predecessor.
- // FIXME: Use or'd predicate or predicated cmp.
- if (BBI.TrueBB->pred_size() > 1)
- return;
+ if (TrueBBI.IsBrAnalyzable)
+ return false;
- // Not a candidate if 'true' block is going to be if-converted.
- AnalyzeBlock(BBI.TrueBB);
- BBInfo &TrueBBI = BBAnalysis[BBI.TrueBB->getNumber()];
- if (TrueBBI.Kind != ICNotClassfied)
- return;
+ if (TrueBBI.BB->pred_size() > 1) {
+ if (TrueBBI.CannotBeCopied ||
+ TrueBBI.NonPredSize > TLI->getIfCvtDupBlockSizeLimit())
+ return false;
+ Dups = TrueBBI.NonPredSize;
+ }
- // No false branch. This BB must end with a conditional branch and a
- // fallthrough.
- if (!BBI.FalseBB)
- BBI.FalseBB = findFalseBlock(BB, BBI.TrueBB);
- assert(BBI.FalseBB && "Expected to find the fallthrough block!");
+ return true;
+}
- // Not a candidate if 'false' block has another predecessor.
- // FIXME: Invert condition and swap 'true' / 'false' blocks?
- if (BBI.FalseBB->pred_size() > 1)
- return;
+/// ValidTriangle - Returns true if the 'true' and 'false' blocks (along
+/// with their common predecessor) forms a valid triangle shape for ifcvt.
+/// If 'FalseBranch' is true, it checks if 'true' block's false branch
+/// branches to the false branch rather than the other way around. It also
+/// returns the number of instructions that the ifcvt would need to duplicate
+/// if performed in 'Dups'.
+bool IfConverter::ValidTriangle(BBInfo &TrueBBI, BBInfo &FalseBBI,
+ bool FalseBranch, unsigned &Dups) const {
+ Dups = 0;
+ if (TrueBBI.IsBeingAnalyzed || TrueBBI.IsDone)
+ return false;
- // Not a candidate if 'false' block is going to be if-converted.
- AnalyzeBlock(BBI.FalseBB);
- BBInfo &FalseBBI = BBAnalysis[BBI.FalseBB->getNumber()];
- if (FalseBBI.Kind != ICNotClassfied)
- return;
+ if (TrueBBI.BB->pred_size() > 1) {
+ if (TrueBBI.CannotBeCopied)
+ return false;
+
+ unsigned Size = TrueBBI.NonPredSize;
+ if (TrueBBI.IsBrAnalyzable) {
+ if (TrueBBI.TrueBB && TrueBBI.BrCond.empty())
+ // Ends with an unconditional branch. It will be removed.
+ --Size;
+ else {
+ MachineBasicBlock *FExit = FalseBranch
+ ? TrueBBI.TrueBB : TrueBBI.FalseBB;
+ if (FExit)
+ // Require a conditional branch
+ ++Size;
+ }
+ }
+ if (Size > TLI->getIfCvtDupBlockSizeLimit())
+ return false;
+ Dups = Size;
+ }
+
+ MachineBasicBlock *TExit = FalseBranch ? TrueBBI.FalseBB : TrueBBI.TrueBB;
+ if (!TExit && blockAlwaysFallThrough(TrueBBI)) {
+ MachineFunction::iterator I = TrueBBI.BB;
+ if (++I == TrueBBI.BB->getParent()->end())
+ return false;
+ TExit = I;
+ }
+ return TExit && TExit == FalseBBI.BB;
+}
+
+static
+MachineBasicBlock::iterator firstNonBranchInst(MachineBasicBlock *BB,
+ const TargetInstrInfo *TII) {
+ MachineBasicBlock::iterator I = BB->end();
+ while (I != BB->begin()) {
+ --I;
+ if (!I->getDesc().isBranch())
+ break;
+ }
+ return I;
+}
+
+/// ValidDiamond - Returns true if the 'true' and 'false' blocks (along
+/// with their common predecessor) forms a valid diamond shape for ifcvt.
+bool IfConverter::ValidDiamond(BBInfo &TrueBBI, BBInfo &FalseBBI,
+ unsigned &Dups1, unsigned &Dups2) const {
+ Dups1 = Dups2 = 0;
+ if (TrueBBI.IsBeingAnalyzed || TrueBBI.IsDone ||
+ FalseBBI.IsBeingAnalyzed || FalseBBI.IsDone)
+ return false;
+
+ MachineBasicBlock *TT = TrueBBI.TrueBB;
+ MachineBasicBlock *FT = FalseBBI.TrueBB;
- // TODO: Only handle very simple cases for now.
+ if (!TT && blockAlwaysFallThrough(TrueBBI))
+ TT = getNextBlock(TrueBBI.BB);
+ if (!FT && blockAlwaysFallThrough(FalseBBI))
+ FT = getNextBlock(FalseBBI.BB);
+ if (TT != FT)
+ return false;
+ if (TT == NULL && (TrueBBI.IsBrAnalyzable || FalseBBI.IsBrAnalyzable))
+ return false;
+ if (TrueBBI.BB->pred_size() > 1 || FalseBBI.BB->pred_size() > 1)
+ return false;
+
+ // FIXME: Allow true block to have an early exit?
if (TrueBBI.FalseBB || FalseBBI.FalseBB ||
- TrueBBI.Cond.size() || FalseBBI.Cond.size())
+ (TrueBBI.ClobbersPred && FalseBBI.ClobbersPred))
+ return false;
+
+ MachineBasicBlock::iterator TI = TrueBBI.BB->begin();
+ MachineBasicBlock::iterator FI = FalseBBI.BB->begin();
+ while (TI != TrueBBI.BB->end() && FI != FalseBBI.BB->end()) {
+ if (!TI->isIdenticalTo(FI))
+ break;
+ ++Dups1;
+ ++TI;
+ ++FI;
+ }
+
+ TI = firstNonBranchInst(TrueBBI.BB, TII);
+ FI = firstNonBranchInst(FalseBBI.BB, TII);
+ while (TI != TrueBBI.BB->begin() && FI != FalseBBI.BB->begin()) {
+ if (!TI->isIdenticalTo(FI))
+ break;
+ ++Dups2;
+ --TI;
+ --FI;
+ }
+
+ return true;
+}
+
+/// ScanInstructions - Scan all the instructions in the block to determine if
+/// the block is predicable. In most cases, that means all the instructions
+/// in the block are isPredicable(). Also checks if the block contains any
+/// instruction which can clobber a predicate (e.g. condition code register).
+/// If so, the block is not predicable unless it's the last instruction.
+void IfConverter::ScanInstructions(BBInfo &BBI) {
+ if (BBI.IsDone)
return;
- if (TrueBBI.TrueBB && TrueBBI.TrueBB == BBI.FalseBB) {
+ bool AlreadyPredicated = BBI.Predicate.size() > 0;
+ // First analyze the end of BB branches.
+ BBI.TrueBB = BBI.FalseBB = NULL;
+ BBI.BrCond.clear();
+ BBI.IsBrAnalyzable =
+ !TII->AnalyzeBranch(*BBI.BB, BBI.TrueBB, BBI.FalseBB, BBI.BrCond);
+ BBI.HasFallThrough = BBI.IsBrAnalyzable && BBI.FalseBB == NULL;
+
+ if (BBI.BrCond.size()) {
+ // No false branch. This BB must end with a conditional branch and a
+ // fallthrough.
+ if (!BBI.FalseBB)
+ BBI.FalseBB = findFalseBlock(BBI.BB, BBI.TrueBB);
+ assert(BBI.FalseBB && "Expected to find the fallthrough block!");
+ }
+
+ // Then scan all the instructions.
+ BBI.NonPredSize = 0;
+ BBI.ClobbersPred = false;
+ bool SeenCondBr = false;
+ for (MachineBasicBlock::iterator I = BBI.BB->begin(), E = BBI.BB->end();
+ I != E; ++I) {
+ const TargetInstrDesc &TID = I->getDesc();
+ if (TID.isNotDuplicable())
+ BBI.CannotBeCopied = true;
+
+ bool isPredicated = TII->isPredicated(I);
+ bool isCondBr = BBI.IsBrAnalyzable && TID.isConditionalBranch();
+
+ if (!isCondBr) {
+ if (!isPredicated)
+ BBI.NonPredSize++;
+ else if (!AlreadyPredicated) {
+ // FIXME: This instruction is already predicated before the
+ // if-conversion pass. It's probably something like a conditional move.
+ // Mark this block unpredicable for now.
+ BBI.IsUnpredicable = true;
+ return;
+ }
+ }
+
+ if (BBI.ClobbersPred && !isPredicated) {
+ // Predicate modification instruction should end the block (except for
+ // already predicated instructions and end of block branches).
+ if (isCondBr) {
+ SeenCondBr = true;
+
+ // A conditional branch is not predicable, but it may be eliminated.
+ continue;
+ }
+
+ // Predicate may have been modified, the subsequent (currently)
+ // unpredicated instructions cannot be correctly predicated.
+ BBI.IsUnpredicable = true;
+ return;
+ }
+
+ // FIXME: Make use of PredDefs? e.g. ADDC, SUBC sets predicates but are
+ // still potentially predicable.
+ std::vector<MachineOperand> PredDefs;
+ if (TII->DefinesPredicate(I, PredDefs))
+ BBI.ClobbersPred = true;
+
+ if (!TID.isPredicable()) {
+ BBI.IsUnpredicable = true;
+ return;
+ }
+ }
+}
+
+/// FeasibilityAnalysis - Determine if the block is a suitable candidate to be
+/// predicated by the specified predicate.
+bool IfConverter::FeasibilityAnalysis(BBInfo &BBI,
+ SmallVectorImpl<MachineOperand> &Pred,
+ bool isTriangle, bool RevBranch) {
+ // If the block is dead or unpredicable, then it cannot be predicated.
+ if (BBI.IsDone || BBI.IsUnpredicable)
+ return false;
+
+ // If it is already predicated, check if its predicate subsumes the new
+ // predicate.
+ if (BBI.Predicate.size() && !TII->SubsumesPredicate(BBI.Predicate, Pred))
+ return false;
+
+ if (BBI.BrCond.size()) {
+ if (!isTriangle)
+ return false;
+
+ // Test predicate subsumption.
+ SmallVector<MachineOperand, 4> RevPred(Pred.begin(), Pred.end());
+ SmallVector<MachineOperand, 4> Cond(BBI.BrCond.begin(), BBI.BrCond.end());
+ if (RevBranch) {
+ if (TII->ReverseBranchCondition(Cond))
+ return false;
+ }
+ if (TII->ReverseBranchCondition(RevPred) ||
+ !TII->SubsumesPredicate(Cond, RevPred))
+ return false;
+ }
+
+ return true;
+}
+
+/// AnalyzeBlock - Analyze the structure of the sub-CFG starting from
+/// the specified block. Record its successors and whether it looks like an
+/// if-conversion candidate.
+IfConverter::BBInfo &IfConverter::AnalyzeBlock(MachineBasicBlock *BB,
+ std::vector<IfcvtToken*> &Tokens) {
+ BBInfo &BBI = BBAnalysis[BB->getNumber()];
+
+ if (BBI.IsAnalyzed || BBI.IsBeingAnalyzed)
+ return BBI;
+
+ BBI.BB = BB;
+ BBI.IsBeingAnalyzed = true;
+
+ ScanInstructions(BBI);
+
+ // Unanalyzable or ends with fallthrough or unconditional branch.
+ if (!BBI.IsBrAnalyzable || BBI.BrCond.empty()) {
+ BBI.IsBeingAnalyzed = false;
+ BBI.IsAnalyzed = true;
+ return BBI;
+ }
+
+ // Do not ifcvt if either path is a back edge to the entry block.
+ if (BBI.TrueBB == BB || BBI.FalseBB == BB) {
+ BBI.IsBeingAnalyzed = false;
+ BBI.IsAnalyzed = true;
+ return BBI;
+ }
+
+ BBInfo &TrueBBI = AnalyzeBlock(BBI.TrueBB, Tokens);
+ BBInfo &FalseBBI = AnalyzeBlock(BBI.FalseBB, Tokens);
+
+ if (TrueBBI.IsDone && FalseBBI.IsDone) {
+ BBI.IsBeingAnalyzed = false;
+ BBI.IsAnalyzed = true;
+ return BBI;
+ }
+
+ SmallVector<MachineOperand, 4> RevCond(BBI.BrCond.begin(), BBI.BrCond.end());
+ bool CanRevCond = !TII->ReverseBranchCondition(RevCond);
+
+ unsigned Dups = 0;
+ unsigned Dups2 = 0;
+ bool TNeedSub = TrueBBI.Predicate.size() > 0;
+ bool FNeedSub = FalseBBI.Predicate.size() > 0;
+ bool Enqueued = false;
+ if (CanRevCond && ValidDiamond(TrueBBI, FalseBBI, Dups, Dups2) &&
+ MeetIfcvtSizeLimit(TrueBBI.NonPredSize - (Dups + Dups2)) &&
+ MeetIfcvtSizeLimit(FalseBBI.NonPredSize - (Dups + Dups2)) &&
+ FeasibilityAnalysis(TrueBBI, BBI.BrCond) &&
+ FeasibilityAnalysis(FalseBBI, RevCond)) {
+ // Diamond:
+ // EBB
+ // / \_
+ // | |
+ // TBB FBB
+ // \ /
+ // TailBB
+ // Note TailBB can be empty.
+ Tokens.push_back(new IfcvtToken(BBI, ICDiamond, TNeedSub|FNeedSub, Dups,
+ Dups2));
+ Enqueued = true;
+ }
+
+ if (ValidTriangle(TrueBBI, FalseBBI, false, Dups) &&
+ MeetIfcvtSizeLimit(TrueBBI.NonPredSize) &&
+ FeasibilityAnalysis(TrueBBI, BBI.BrCond, true)) {
// Triangle:
// EBB
// | \_
// | TBB
// | /
// FBB
- BBI.Kind = ICTriangleEntry;
- TrueBBI.Kind = FalseBBI.Kind = ICTriangle;
- } else if (TrueBBI.TrueBB == FalseBBI.TrueBB) {
- // Diamond:
+ Tokens.push_back(new IfcvtToken(BBI, ICTriangle, TNeedSub, Dups));
+ Enqueued = true;
+ }
+
+ if (ValidTriangle(TrueBBI, FalseBBI, true, Dups) &&
+ MeetIfcvtSizeLimit(TrueBBI.NonPredSize) &&
+ FeasibilityAnalysis(TrueBBI, BBI.BrCond, true, true)) {
+ Tokens.push_back(new IfcvtToken(BBI, ICTriangleRev, TNeedSub, Dups));
+ Enqueued = true;
+ }
+
+ if (ValidSimple(TrueBBI, Dups) &&
+ MeetIfcvtSizeLimit(TrueBBI.NonPredSize) &&
+ FeasibilityAnalysis(TrueBBI, BBI.BrCond)) {
+ // Simple (split, no rejoin):
// EBB
- // / \_
- // | |
- // TBB FBB
- // \ /
- // TailBB
- // Note MBB can be empty in case both TBB and FBB are return blocks.
- BBI.Kind = ICDiamondEntry;
- TrueBBI.Kind = FalseBBI.Kind = ICDiamond;
- BBI.TailBB = TrueBBI.TrueBB;
+ // | \_
+ // | |
+ // | TBB---> exit
+ // |
+ // FBB
+ Tokens.push_back(new IfcvtToken(BBI, ICSimple, TNeedSub, Dups));
+ Enqueued = true;
}
- return;
-}
-/// InitialFunctionAnalysis - Analyze all blocks and find entries for all
-/// if-conversion candidates.
-void IfConverter::InitialFunctionAnalysis(MachineFunction &MF,
- std::vector<int> &Candidates) {
- for (MachineFunction::iterator I = MF.begin(), E = MF.end(); I != E; ++I) {
- MachineBasicBlock *BB = I;
- AnalyzeBlock(BB);
- BBInfo &BBI = BBAnalysis[BB->getNumber()];
- if (BBI.Kind == ICTriangleEntry || BBI.Kind == ICDiamondEntry)
- Candidates.push_back(BB->getNumber());
+ if (CanRevCond) {
+ // Try the other path...
+ if (ValidTriangle(FalseBBI, TrueBBI, false, Dups) &&
+ MeetIfcvtSizeLimit(FalseBBI.NonPredSize) &&
+ FeasibilityAnalysis(FalseBBI, RevCond, true)) {
+ Tokens.push_back(new IfcvtToken(BBI, ICTriangleFalse, FNeedSub, Dups));
+ Enqueued = true;
+ }
+
+ if (ValidTriangle(FalseBBI, TrueBBI, true, Dups) &&
+ MeetIfcvtSizeLimit(FalseBBI.NonPredSize) &&
+ FeasibilityAnalysis(FalseBBI, RevCond, true, true)) {
+ Tokens.push_back(new IfcvtToken(BBI, ICTriangleFRev, FNeedSub, Dups));
+ Enqueued = true;
+ }
+
+ if (ValidSimple(FalseBBI, Dups) &&
+ MeetIfcvtSizeLimit(FalseBBI.NonPredSize) &&
+ FeasibilityAnalysis(FalseBBI, RevCond)) {
+ Tokens.push_back(new IfcvtToken(BBI, ICSimpleFalse, FNeedSub, Dups));
+ Enqueued = true;
+ }
}
+
+ BBI.IsEnqueued = Enqueued;
+ BBI.IsBeingAnalyzed = false;
+ BBI.IsAnalyzed = true;
+ return BBI;
}
-/// TransferPreds - Transfer all the predecessors of FromBB to ToBB.
-///
-static void TransferPreds(MachineBasicBlock *ToBB, MachineBasicBlock *FromBB) {
- std::vector<MachineBasicBlock*> Preds(FromBB->pred_begin(),
- FromBB->pred_end());
- for (unsigned i = 0, e = Preds.size(); i != e; ++i) {
- MachineBasicBlock *Pred = Preds[i];
- Pred->removeSuccessor(FromBB);
- if (!Pred->isSuccessor(ToBB))
- Pred->addSuccessor(ToBB);
+/// AnalyzeBlocks - Analyze all blocks and find entries for all if-conversion
+/// candidates. It returns true if any CFG restructuring is done to expose more
+/// if-conversion opportunities.
+bool IfConverter::AnalyzeBlocks(MachineFunction &MF,
+ std::vector<IfcvtToken*> &Tokens) {
+ bool Change = false;
+ std::set<MachineBasicBlock*> Visited;
+ for (unsigned i = 0, e = Roots.size(); i != e; ++i) {
+ for (idf_ext_iterator<MachineBasicBlock*> I=idf_ext_begin(Roots[i],Visited),
+ E = idf_ext_end(Roots[i], Visited); I != E; ++I) {
+ MachineBasicBlock *BB = *I;
+ AnalyzeBlock(BB, Tokens);
}
+ }
+
+ // Sort to favor more complex ifcvt scheme.
+ std::stable_sort(Tokens.begin(), Tokens.end(), IfcvtTokenCmp);
+
+ return Change;
}
-/// TransferSuccs - Transfer all the successors of FromBB to ToBB.
+/// canFallThroughTo - Returns true either if ToBB is the next block after BB or
+/// that all the intervening blocks are empty (given BB can fall through to its
+/// next block).
+static bool canFallThroughTo(MachineBasicBlock *BB, MachineBasicBlock *ToBB) {
+ MachineFunction::iterator I = BB;
+ MachineFunction::iterator TI = ToBB;
+ MachineFunction::iterator E = BB->getParent()->end();
+ while (++I != TI)
+ if (I == E || !I->empty())
+ return false;
+ return true;
+}
+
+/// InvalidatePreds - Invalidate predecessor BB info so it would be re-analyzed
+/// to determine if it can be if-converted. If predecessor is already enqueued,
+/// dequeue it!
+void IfConverter::InvalidatePreds(MachineBasicBlock *BB) {
+ for (MachineBasicBlock::pred_iterator PI = BB->pred_begin(),
+ E = BB->pred_end(); PI != E; ++PI) {
+ BBInfo &PBBI = BBAnalysis[(*PI)->getNumber()];
+ if (PBBI.IsDone || PBBI.BB == BB)
+ continue;
+ PBBI.IsAnalyzed = false;
+ PBBI.IsEnqueued = false;
+ }
+}
+
+/// InsertUncondBranch - Inserts an unconditional branch from BB to ToBB.
///
-static void TransferSuccs(MachineBasicBlock *ToBB, MachineBasicBlock *FromBB) {
- std::vector<MachineBasicBlock*> Succs(FromBB->succ_begin(),
- FromBB->succ_end());
- for (unsigned i = 0, e = Succs.size(); i != e; ++i) {
- MachineBasicBlock *Succ = Succs[i];
- FromBB->removeSuccessor(Succ);
- if (!ToBB->isSuccessor(Succ))
- ToBB->addSuccessor(Succ);
- }
+static void InsertUncondBranch(MachineBasicBlock *BB, MachineBasicBlock *ToBB,
+ const TargetInstrInfo *TII) {
+ SmallVector<MachineOperand, 0> NoCond;
+ TII->InsertBranch(*BB, ToBB, NULL, NoCond);
}
-/// IfConvertTriangle - If convert a triangle sub-CFG.
+/// RemoveExtraEdges - Remove true / false edges if either / both are no longer
+/// successors.
+void IfConverter::RemoveExtraEdges(BBInfo &BBI) {
+ MachineBasicBlock *TBB = NULL, *FBB = NULL;
+ SmallVector<MachineOperand, 4> Cond;
+ if (!TII->AnalyzeBranch(*BBI.BB, TBB, FBB, Cond))
+ BBI.BB->CorrectExtraCFGEdges(TBB, FBB, !Cond.empty());
+}
+
+/// IfConvertSimple - If convert a simple (split, no rejoin) sub-CFG.
///
-bool IfConverter::IfConvertTriangle(BBInfo &BBI) {
- if (isBlockPredicable(BBI.TrueBB)) {
- BBInfo &TrueBBI = BBAnalysis[BBI.TrueBB->getNumber()];
- BBInfo &FalseBBI = BBAnalysis[BBI.FalseBB->getNumber()];
+bool IfConverter::IfConvertSimple(BBInfo &BBI, IfcvtKind Kind) {
+ BBInfo &TrueBBI = BBAnalysis[BBI.TrueBB->getNumber()];
+ BBInfo &FalseBBI = BBAnalysis[BBI.FalseBB->getNumber()];
+ BBInfo *CvtBBI = &TrueBBI;
+ BBInfo *NextBBI = &FalseBBI;
- // Predicate the 'true' block after removing its branch.
- TrueBBI.Size -= TII->RemoveBranch(*BBI.TrueBB);
- PredicateBlock(BBI.TrueBB, BBI.Cond);
+ SmallVector<MachineOperand, 4> Cond(BBI.BrCond.begin(), BBI.BrCond.end());
+ if (Kind == ICSimpleFalse)
+ std::swap(CvtBBI, NextBBI);
- // Join the 'true' and 'false' blocks by copying the instructions
- // from the 'false' block to the 'true' block.
- BBI.TrueBB->removeSuccessor(BBI.FalseBB);
- MergeBlocks(TrueBBI, FalseBBI);
+ if (CvtBBI->IsDone ||
+ (CvtBBI->CannotBeCopied && CvtBBI->BB->pred_size() > 1)) {
+ // Something has changed. It's no longer safe to predicate this block.
+ BBI.IsAnalyzed = false;
+ CvtBBI->IsAnalyzed = false;
+ return false;
+ }
- // Now merge the entry of the triangle with the true block.
- BBI.Size -= TII->RemoveBranch(*BBI.BB);
- MergeBlocks(BBI, TrueBBI);
+ if (Kind == ICSimpleFalse)
+ if (TII->ReverseBranchCondition(Cond))
+ assert(false && "Unable to reverse branch condition!");
- // Update block info.
- TrueBBI.Kind = ICInvalid;
- FalseBBI.Kind = ICInvalid;
+ if (CvtBBI->BB->pred_size() > 1) {
+ BBI.NonPredSize -= TII->RemoveBranch(*BBI.BB);
+ // Copy instructions in the true block, predicate them, and add them to
+ // the entry block.
+ CopyAndPredicateBlock(BBI, *CvtBBI, Cond);
+ } else {
+ PredicateBlock(*CvtBBI, CvtBBI->BB->end(), Cond);
- // FIXME: Must maintain LiveIns.
- NumIfConvBBs++;
- return true;
+ // Merge converted block into entry block.
+ BBI.NonPredSize -= TII->RemoveBranch(*BBI.BB);
+ MergeBlocks(BBI, *CvtBBI);
}
- return false;
+
+ bool IterIfcvt = true;
+ if (!canFallThroughTo(BBI.BB, NextBBI->BB)) {
+ InsertUncondBranch(BBI.BB, NextBBI->BB, TII);
+ BBI.HasFallThrough = false;
+ // Now ifcvt'd block will look like this:
+ // BB:
+ // ...
+ // t, f = cmp
+ // if t op
+ // b BBf
+ //
+ // We cannot further ifcvt this block because the unconditional branch
+ // will have to be predicated on the new condition, that will not be
+ // available if cmp executes.
+ IterIfcvt = false;
+ }
+
+ RemoveExtraEdges(BBI);
+
+ // Update block info. BB can be iteratively if-converted.
+ if (!IterIfcvt)
+ BBI.IsDone = true;
+ InvalidatePreds(BBI.BB);
+ CvtBBI->IsDone = true;
+
+ // FIXME: Must maintain LiveIns.
+ return true;
}
-/// IfConvertDiamond - If convert a diamond sub-CFG.
+/// IfConvertTriangle - If convert a triangle sub-CFG.
///
-bool IfConverter::IfConvertDiamond(BBInfo &BBI) {
- if (isBlockPredicable(BBI.TrueBB) && isBlockPredicable(BBI.FalseBB)) {
- std::vector<MachineInstr*> Dups;
- if (!BBI.TailBB) {
- // No common merge block. Check if the terminators (e.g. return) are
- // the same or predicable.
- MachineBasicBlock::iterator TT = BBI.TrueBB->getFirstTerminator();
- MachineBasicBlock::iterator FT = BBI.FalseBB->getFirstTerminator();
- while (TT != BBI.TrueBB->end() && FT != BBI.FalseBB->end()) {
- if (TT->isIdenticalTo(FT))
- Dups.push_back(TT); // Will erase these later.
- else if (!TT->isPredicable() && !FT->isPredicable())
- return false; // Can't if-convert. Abort!
- ++TT;
- ++FT;
- }
- // One of the two pathes have more terminators, make sure they are all
- // predicable.
- while (TT != BBI.TrueBB->end())
- if (!TT->isPredicable())
- return false; // Can't if-convert. Abort!
- while (FT != BBI.FalseBB->end())
- if (!FT->isPredicable())
- return false; // Can't if-convert. Abort!
- }
+bool IfConverter::IfConvertTriangle(BBInfo &BBI, IfcvtKind Kind) {
+ BBInfo &TrueBBI = BBAnalysis[BBI.TrueBB->getNumber()];
+ BBInfo &FalseBBI = BBAnalysis[BBI.FalseBB->getNumber()];
+ BBInfo *CvtBBI = &TrueBBI;
+ BBInfo *NextBBI = &FalseBBI;
+
+ SmallVector<MachineOperand, 4> Cond(BBI.BrCond.begin(), BBI.BrCond.end());
+ if (Kind == ICTriangleFalse || Kind == ICTriangleFRev)
+ std::swap(CvtBBI, NextBBI);
- BBInfo &TrueBBI = BBAnalysis[BBI.TrueBB->getNumber()];
- BBInfo &FalseBBI = BBAnalysis[BBI.FalseBB->getNumber()];
+ if (CvtBBI->IsDone ||
+ (CvtBBI->CannotBeCopied && CvtBBI->BB->pred_size() > 1)) {
+ // Something has changed. It's no longer safe to predicate this block.
+ BBI.IsAnalyzed = false;
+ CvtBBI->IsAnalyzed = false;
+ return false;
+ }
- // Remove the duplicated instructions from the 'true' block.
- for (unsigned i = 0, e = Dups.size(); i != e; ++i) {
- Dups[i]->eraseFromParent();
- --TrueBBI.Size;
+ if (Kind == ICTriangleFalse || Kind == ICTriangleFRev)
+ if (TII->ReverseBranchCondition(Cond))
+ assert(false && "Unable to reverse branch condition!");
+
+ if (Kind == ICTriangleRev || Kind == ICTriangleFRev) {
+ if (ReverseBranchCondition(*CvtBBI)) {
+ // BB has been changed, modify its predecessors (except for this
+ // one) so they don't get ifcvt'ed based on bad intel.
+ for (MachineBasicBlock::pred_iterator PI = CvtBBI->BB->pred_begin(),
+ E = CvtBBI->BB->pred_end(); PI != E; ++PI) {
+ MachineBasicBlock *PBB = *PI;
+ if (PBB == BBI.BB)
+ continue;
+ BBInfo &PBBI = BBAnalysis[PBB->getNumber()];
+ if (PBBI.IsEnqueued) {
+ PBBI.IsAnalyzed = false;
+ PBBI.IsEnqueued = false;
+ }
+ }
}
-
+ }
+
+ bool HasEarlyExit = CvtBBI->FalseBB != NULL;
+ bool DupBB = CvtBBI->BB->pred_size() > 1;
+ if (DupBB) {
+ BBI.NonPredSize -= TII->RemoveBranch(*BBI.BB);
+ // Copy instructions in the true block, predicate them, and add them to
+ // the entry block.
+ CopyAndPredicateBlock(BBI, *CvtBBI, Cond, true);
+ } else {
// Predicate the 'true' block after removing its branch.
- TrueBBI.Size -= TII->RemoveBranch(*BBI.TrueBB);
- PredicateBlock(BBI.TrueBB, BBI.Cond);
-
- // Predicate the 'false' block.
- std::vector<MachineOperand> NewCond(BBI.Cond);
- TII->ReverseBranchCondition(NewCond);
- PredicateBlock(BBI.FalseBB, NewCond, true);
-
- // Merge the 'true' and 'false' blocks by copying the instructions
- // from the 'false' block to the 'true' block.
- MergeBlocks(TrueBBI, FalseBBI);
-
- // Remove the conditional branch from entry to the blocks.
- BBI.Size -= TII->RemoveBranch(*BBI.BB);
-
- // Merge the combined block into the entry of the diamond if the entry
- // block is the only predecessor. Otherwise, insert an unconditional
- // branch.
- BBInfo *CvtBBI = &TrueBBI;
- if (BBI.TrueBB->pred_size() == 1) {
- BBI.BB->removeSuccessor(BBI.TrueBB);
- MergeBlocks(BBI, TrueBBI);
- CvtBBI = &BBI;
+ CvtBBI->NonPredSize -= TII->RemoveBranch(*CvtBBI->BB);
+ PredicateBlock(*CvtBBI, CvtBBI->BB->end(), Cond);
+ }
+
+ if (!DupBB) {
+ // Now merge the entry of the triangle with the true block.
+ BBI.NonPredSize -= TII->RemoveBranch(*BBI.BB);
+ MergeBlocks(BBI, *CvtBBI);
+ }
+
+ // If 'true' block has a 'false' successor, add an exit branch to it.
+ if (HasEarlyExit) {
+ SmallVector<MachineOperand, 4> RevCond(CvtBBI->BrCond.begin(),
+ CvtBBI->BrCond.end());
+ if (TII->ReverseBranchCondition(RevCond))
+ assert(false && "Unable to reverse branch condition!");
+ TII->InsertBranch(*BBI.BB, CvtBBI->FalseBB, NULL, RevCond);
+ BBI.BB->addSuccessor(CvtBBI->FalseBB);
+ }
+
+ // Merge in the 'false' block if the 'false' block has no other
+ // predecessors. Otherwise, add an unconditional branch to 'false'.
+ bool FalseBBDead = false;
+ bool IterIfcvt = true;
+ bool isFallThrough = canFallThroughTo(BBI.BB, NextBBI->BB);
+ if (!isFallThrough) {
+ // Only merge them if the true block does not fallthrough to the false
+ // block. By not merging them, we make it possible to iteratively
+ // ifcvt the blocks.
+ if (!HasEarlyExit &&
+ NextBBI->BB->pred_size() == 1 && !NextBBI->HasFallThrough) {
+ MergeBlocks(BBI, *NextBBI);
+ FalseBBDead = true;
} else {
- std::vector<MachineOperand> NoCond;
- TII->InsertBranch(*BBI.BB, BBI.TrueBB, NULL, NoCond);
+ InsertUncondBranch(BBI.BB, NextBBI->BB, TII);
+ BBI.HasFallThrough = false;
}
+ // Mixed predicated and unpredicated code. This cannot be iteratively
+ // predicated.
+ IterIfcvt = false;
+ }
- // If the if-converted block fallthrough into the tail block, then
- // fold the tail block in as well.
- if (BBI.TailBB && CvtBBI->BB->succ_size() == 1) {
- CvtBBI->Size -= TII->RemoveBranch(*CvtBBI->BB);
- CvtBBI->BB->removeSuccessor(BBI.TailBB);
- BBInfo TailBBI = BBAnalysis[BBI.TailBB->getNumber()];
- MergeBlocks(*CvtBBI, TailBBI);
- TailBBI.Kind = ICInvalid;
- }
+ RemoveExtraEdges(BBI);
- // Update block info.
- TrueBBI.Kind = ICInvalid;
- FalseBBI.Kind = ICInvalid;
+ // Update block info. BB can be iteratively if-converted.
+ if (!IterIfcvt)
+ BBI.IsDone = true;
+ InvalidatePreds(BBI.BB);
+ CvtBBI->IsDone = true;
+ if (FalseBBDead)
+ NextBBI->IsDone = true;
- // FIXME: Must maintain LiveIns.
- NumIfConvBBs += 2;
- return true;
- }
- return false;
+ // FIXME: Must maintain LiveIns.
+ return true;
}
-/// isBlockPredicable - Returns true if the block is predicable. In most
-/// cases, that means all the instructions in the block has M_PREDICABLE flag.
-/// It assume all the terminator instructions can be converted or deleted.
-bool IfConverter::isBlockPredicable(MachineBasicBlock *BB) const {
- const BBInfo &BBI = BBAnalysis[BB->getNumber()];
- if (BBI.Size == 0 || BBI.Size > TLI->getIfCvtBlockSizeLimit())
+/// IfConvertDiamond - If convert a diamond sub-CFG.
+///
+bool IfConverter::IfConvertDiamond(BBInfo &BBI, IfcvtKind Kind,
+ unsigned NumDups1, unsigned NumDups2) {
+ BBInfo &TrueBBI = BBAnalysis[BBI.TrueBB->getNumber()];
+ BBInfo &FalseBBI = BBAnalysis[BBI.FalseBB->getNumber()];
+ MachineBasicBlock *TailBB = TrueBBI.TrueBB;
+ // True block must fall through or end with an unanalyzable terminator.
+ if (!TailBB) {
+ if (blockAlwaysFallThrough(TrueBBI))
+ TailBB = FalseBBI.TrueBB;
+ assert((TailBB || !TrueBBI.IsBrAnalyzable) && "Unexpected!");
+ }
+
+ if (TrueBBI.IsDone || FalseBBI.IsDone ||
+ TrueBBI.BB->pred_size() > 1 ||
+ FalseBBI.BB->pred_size() > 1) {
+ // Something has changed. It's no longer safe to predicate these blocks.
+ BBI.IsAnalyzed = false;
+ TrueBBI.IsAnalyzed = false;
+ FalseBBI.IsAnalyzed = false;
return false;
+ }
- for (MachineBasicBlock::iterator I = BB->begin(), E = BB->end();
- I != E; ++I) {
- if (TII->isTerminatorInstr(I->getOpcode()))
- continue;
- if (!I->isPredicable())
- return false;
+ // Merge the 'true' and 'false' blocks by copying the instructions
+ // from the 'false' block to the 'true' block. That is, unless the true
+ // block would clobber the predicate, in that case, do the opposite.
+ BBInfo *BBI1 = &TrueBBI;
+ BBInfo *BBI2 = &FalseBBI;
+ SmallVector<MachineOperand, 4> RevCond(BBI.BrCond.begin(), BBI.BrCond.end());
+ if (TII->ReverseBranchCondition(RevCond))
+ assert(false && "Unable to reverse branch condition!");
+ SmallVector<MachineOperand, 4> *Cond1 = &BBI.BrCond;
+ SmallVector<MachineOperand, 4> *Cond2 = &RevCond;
+
+ // Figure out the more profitable ordering.
+ bool DoSwap = false;
+ if (TrueBBI.ClobbersPred && !FalseBBI.ClobbersPred)
+ DoSwap = true;
+ else if (TrueBBI.ClobbersPred == FalseBBI.ClobbersPred) {
+ if (TrueBBI.NonPredSize > FalseBBI.NonPredSize)
+ DoSwap = true;
}
+ if (DoSwap) {
+ std::swap(BBI1, BBI2);
+ std::swap(Cond1, Cond2);
+ }
+
+ // Remove the conditional branch from entry to the blocks.
+ BBI.NonPredSize -= TII->RemoveBranch(*BBI.BB);
+
+ // Remove the duplicated instructions at the beginnings of both paths.
+ MachineBasicBlock::iterator DI1 = BBI1->BB->begin();
+ MachineBasicBlock::iterator DI2 = BBI2->BB->begin();
+ BBI1->NonPredSize -= NumDups1;
+ BBI2->NonPredSize -= NumDups1;
+ while (NumDups1 != 0) {
+ ++DI1;
+ ++DI2;
+ --NumDups1;
+ }
+ BBI.BB->splice(BBI.BB->end(), BBI1->BB, BBI1->BB->begin(), DI1);
+ BBI2->BB->erase(BBI2->BB->begin(), DI2);
+
+ // Predicate the 'true' block after removing its branch.
+ BBI1->NonPredSize -= TII->RemoveBranch(*BBI1->BB);
+ DI1 = BBI1->BB->end();
+ for (unsigned i = 0; i != NumDups2; ++i)
+ --DI1;
+ BBI1->BB->erase(DI1, BBI1->BB->end());
+ PredicateBlock(*BBI1, BBI1->BB->end(), *Cond1);
+
+ // Predicate the 'false' block.
+ BBI2->NonPredSize -= TII->RemoveBranch(*BBI2->BB);
+ DI2 = BBI2->BB->end();
+ while (NumDups2 != 0) {
+ --DI2;
+ --NumDups2;
+ }
+ PredicateBlock(*BBI2, DI2, *Cond2);
+
+ // Merge the true block into the entry of the diamond.
+ MergeBlocks(BBI, *BBI1);
+ MergeBlocks(BBI, *BBI2);
+
+ // If the if-converted block falls through or unconditionally branches into
+ // the tail block, and the tail block does not have other predecessors, then
+ // fold the tail block in as well. Otherwise, unless it falls through to the
+ // tail, add a unconditional branch to it.
+ if (TailBB) {
+ BBInfo TailBBI = BBAnalysis[TailBB->getNumber()];
+ if (TailBB->pred_size() == 1 && !TailBBI.HasFallThrough) {
+ BBI.NonPredSize -= TII->RemoveBranch(*BBI.BB);
+ MergeBlocks(BBI, TailBBI);
+ TailBBI.IsDone = true;
+ } else {
+ InsertUncondBranch(BBI.BB, TailBB, TII);
+ BBI.HasFallThrough = false;
+ }
+ }
+
+ RemoveExtraEdges(BBI);
+
+ // Update block info.
+ BBI.IsDone = TrueBBI.IsDone = FalseBBI.IsDone = true;
+ InvalidatePreds(BBI.BB);
+
+ // FIXME: Must maintain LiveIns.
return true;
}
-/// PredicateBlock - Predicate every instruction in the block with the specified
-/// condition. If IgnoreTerm is true, skip over all terminator instructions.
-void IfConverter::PredicateBlock(MachineBasicBlock *BB,
- std::vector<MachineOperand> &Cond,
- bool IgnoreTerm) {
- for (MachineBasicBlock::iterator I = BB->begin(), E = BB->end();
- I != E; ++I) {
- if (IgnoreTerm && TII->isTerminatorInstr(I->getOpcode()))
+/// PredicateBlock - Predicate instructions from the start of the block to the
+/// specified end with the specified condition.
+void IfConverter::PredicateBlock(BBInfo &BBI,
+ MachineBasicBlock::iterator E,
+ SmallVectorImpl<MachineOperand> &Cond) {
+ for (MachineBasicBlock::iterator I = BBI.BB->begin(); I != E; ++I) {
+ if (TII->isPredicated(I))
continue;
- if (!TII->PredicateInstruction(&*I, Cond)) {
- cerr << "Unable to predication " << *I << "!\n";
+ if (!TII->PredicateInstruction(I, Cond)) {
+ cerr << "Unable to predicate " << *I << "!\n";
abort();
}
}
+
+ std::copy(Cond.begin(), Cond.end(), std::back_inserter(BBI.Predicate));
+
+ BBI.IsAnalyzed = false;
+ BBI.NonPredSize = 0;
+
+ NumIfConvBBs++;
+}
+
+/// CopyAndPredicateBlock - Copy and predicate instructions from source BB to
+/// the destination block. Skip end of block branches if IgnoreBr is true.
+void IfConverter::CopyAndPredicateBlock(BBInfo &ToBBI, BBInfo &FromBBI,
+ SmallVectorImpl<MachineOperand> &Cond,
+ bool IgnoreBr) {
+ MachineFunction &MF = *ToBBI.BB->getParent();
+
+ for (MachineBasicBlock::iterator I = FromBBI.BB->begin(),
+ E = FromBBI.BB->end(); I != E; ++I) {
+ const TargetInstrDesc &TID = I->getDesc();
+ bool isPredicated = TII->isPredicated(I);
+ // Do not copy the end of the block branches.
+ if (IgnoreBr && !isPredicated && TID.isBranch())
+ break;
+
+ MachineInstr *MI = MF.CloneMachineInstr(I);
+ ToBBI.BB->insert(ToBBI.BB->end(), MI);
+ ToBBI.NonPredSize++;
+
+ if (!isPredicated)
+ if (!TII->PredicateInstruction(MI, Cond)) {
+ cerr << "Unable to predicate " << *MI << "!\n";
+ abort();
+ }
+ }
+
+ std::vector<MachineBasicBlock *> Succs(FromBBI.BB->succ_begin(),
+ FromBBI.BB->succ_end());
+ MachineBasicBlock *NBB = getNextBlock(FromBBI.BB);
+ MachineBasicBlock *FallThrough = FromBBI.HasFallThrough ? NBB : NULL;
+
+ for (unsigned i = 0, e = Succs.size(); i != e; ++i) {
+ MachineBasicBlock *Succ = Succs[i];
+ // Fallthrough edge can't be transferred.
+ if (Succ == FallThrough)
+ continue;
+ ToBBI.BB->addSuccessor(Succ);
+ }
+
+ std::copy(FromBBI.Predicate.begin(), FromBBI.Predicate.end(),
+ std::back_inserter(ToBBI.Predicate));
+ std::copy(Cond.begin(), Cond.end(), std::back_inserter(ToBBI.Predicate));
+
+ ToBBI.ClobbersPred |= FromBBI.ClobbersPred;
+ ToBBI.IsAnalyzed = false;
+
+ NumDupBBs++;
}
/// MergeBlocks - Move all instructions from FromBB to the end of ToBB.
void IfConverter::MergeBlocks(BBInfo &ToBBI, BBInfo &FromBBI) {
ToBBI.BB->splice(ToBBI.BB->end(),
FromBBI.BB, FromBBI.BB->begin(), FromBBI.BB->end());
- TransferPreds(ToBBI.BB, FromBBI.BB);
- TransferSuccs(ToBBI.BB, FromBBI.BB);
- ToBBI.Size += FromBBI.Size;
- FromBBI.Size = 0;
+
+ // Redirect all branches to FromBB to ToBB.
+ std::vector<MachineBasicBlock *> Preds(FromBBI.BB->pred_begin(),
+ FromBBI.BB->pred_end());
+ for (unsigned i = 0, e = Preds.size(); i != e; ++i) {
+ MachineBasicBlock *Pred = Preds[i];
+ if (Pred == ToBBI.BB)
+ continue;
+ Pred->ReplaceUsesOfBlockWith(FromBBI.BB, ToBBI.BB);
+ }
+
+ std::vector<MachineBasicBlock *> Succs(FromBBI.BB->succ_begin(),
+ FromBBI.BB->succ_end());
+ MachineBasicBlock *NBB = getNextBlock(FromBBI.BB);
+ MachineBasicBlock *FallThrough = FromBBI.HasFallThrough ? NBB : NULL;
+
+ for (unsigned i = 0, e = Succs.size(); i != e; ++i) {
+ MachineBasicBlock *Succ = Succs[i];
+ // Fallthrough edge can't be transferred.
+ if (Succ == FallThrough)
+ continue;
+ FromBBI.BB->removeSuccessor(Succ);
+ ToBBI.BB->addSuccessor(Succ);
+ }
+
+ // Now FromBBI always falls through to the next block!
+ if (NBB)
+ FromBBI.BB->addSuccessor(NBB);
+
+ std::copy(FromBBI.Predicate.begin(), FromBBI.Predicate.end(),
+ std::back_inserter(ToBBI.Predicate));
+ FromBBI.Predicate.clear();
+
+ ToBBI.NonPredSize += FromBBI.NonPredSize;
+ FromBBI.NonPredSize = 0;
+
+ ToBBI.ClobbersPred |= FromBBI.ClobbersPred;
+ ToBBI.HasFallThrough = FromBBI.HasFallThrough;
+ ToBBI.IsAnalyzed = false;
+ FromBBI.IsAnalyzed = false;
}
projects / oota-llvm.git / blobdiff