1255 lines
44 KiB
C++
1255 lines
44 KiB
C++
//===-- IfConversion.cpp - Machine code if conversion pass. ---------------===//
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//
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// The LLVM Compiler Infrastructure
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//
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// This file is distributed under the University of Illinois Open Source
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// License. See LICENSE.TXT for details.
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//
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//===----------------------------------------------------------------------===//
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//
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// This file implements the machine instruction level if-conversion pass.
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//
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//===----------------------------------------------------------------------===//
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#define DEBUG_TYPE "ifcvt"
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#include "BranchFolding.h"
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#include "llvm/Function.h"
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#include "llvm/CodeGen/Passes.h"
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#include "llvm/CodeGen/MachineModuleInfo.h"
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#include "llvm/CodeGen/MachineFunctionPass.h"
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#include "llvm/Target/TargetInstrInfo.h"
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#include "llvm/Target/TargetLowering.h"
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#include "llvm/Target/TargetMachine.h"
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#include "llvm/Support/CommandLine.h"
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#include "llvm/Support/Debug.h"
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#include "llvm/Support/ErrorHandling.h"
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#include "llvm/Support/raw_ostream.h"
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#include "llvm/ADT/DepthFirstIterator.h"
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#include "llvm/ADT/Statistic.h"
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#include "llvm/ADT/STLExtras.h"
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using namespace llvm;
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// Hidden options for help debugging.
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static cl::opt<int> IfCvtFnStart("ifcvt-fn-start", cl::init(-1), cl::Hidden);
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static cl::opt<int> IfCvtFnStop("ifcvt-fn-stop", cl::init(-1), cl::Hidden);
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static cl::opt<int> IfCvtLimit("ifcvt-limit", cl::init(-1), cl::Hidden);
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static cl::opt<bool> DisableSimple("disable-ifcvt-simple",
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cl::init(false), cl::Hidden);
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static cl::opt<bool> DisableSimpleF("disable-ifcvt-simple-false",
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cl::init(false), cl::Hidden);
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static cl::opt<bool> DisableTriangle("disable-ifcvt-triangle",
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cl::init(false), cl::Hidden);
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static cl::opt<bool> DisableTriangleR("disable-ifcvt-triangle-rev",
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cl::init(false), cl::Hidden);
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static cl::opt<bool> DisableTriangleF("disable-ifcvt-triangle-false",
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cl::init(false), cl::Hidden);
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static cl::opt<bool> DisableTriangleFR("disable-ifcvt-triangle-false-rev",
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cl::init(false), cl::Hidden);
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static cl::opt<bool> DisableDiamond("disable-ifcvt-diamond",
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cl::init(false), cl::Hidden);
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STATISTIC(NumSimple, "Number of simple if-conversions performed");
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STATISTIC(NumSimpleFalse, "Number of simple (F) if-conversions performed");
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STATISTIC(NumTriangle, "Number of triangle if-conversions performed");
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STATISTIC(NumTriangleRev, "Number of triangle (R) if-conversions performed");
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STATISTIC(NumTriangleFalse,"Number of triangle (F) if-conversions performed");
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STATISTIC(NumTriangleFRev, "Number of triangle (F/R) if-conversions performed");
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STATISTIC(NumDiamonds, "Number of diamond if-conversions performed");
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STATISTIC(NumIfConvBBs, "Number of if-converted blocks");
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STATISTIC(NumDupBBs, "Number of duplicated blocks");
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namespace {
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class IfConverter : public MachineFunctionPass {
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enum IfcvtKind {
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ICNotClassfied, // BB data valid, but not classified.
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ICSimpleFalse, // Same as ICSimple, but on the false path.
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ICSimple, // BB is entry of an one split, no rejoin sub-CFG.
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ICTriangleFRev, // Same as ICTriangleFalse, but false path rev condition.
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ICTriangleRev, // Same as ICTriangle, but true path rev condition.
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ICTriangleFalse, // Same as ICTriangle, but on the false path.
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ICTriangle, // BB is entry of a triangle sub-CFG.
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ICDiamond // BB is entry of a diamond sub-CFG.
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};
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/// BBInfo - One per MachineBasicBlock, this is used to cache the result
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/// if-conversion feasibility analysis. This includes results from
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/// TargetInstrInfo::AnalyzeBranch() (i.e. TBB, FBB, and Cond), and its
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/// classification, and common tail block of its successors (if it's a
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/// diamond shape), its size, whether it's predicable, and whether any
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/// instruction can clobber the 'would-be' predicate.
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///
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/// IsDone - True if BB is not to be considered for ifcvt.
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/// IsBeingAnalyzed - True if BB is currently being analyzed.
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/// IsAnalyzed - True if BB has been analyzed (info is still valid).
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/// IsEnqueued - True if BB has been enqueued to be ifcvt'ed.
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/// IsBrAnalyzable - True if AnalyzeBranch() returns false.
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/// HasFallThrough - True if BB may fallthrough to the following BB.
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/// IsUnpredicable - True if BB is known to be unpredicable.
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/// ClobbersPred - True if BB could modify predicates (e.g. has
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/// cmp, call, etc.)
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/// NonPredSize - Number of non-predicated instructions.
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/// BB - Corresponding MachineBasicBlock.
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/// TrueBB / FalseBB- See AnalyzeBranch().
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/// BrCond - Conditions for end of block conditional branches.
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/// Predicate - Predicate used in the BB.
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struct BBInfo {
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bool IsDone : 1;
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bool IsBeingAnalyzed : 1;
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bool IsAnalyzed : 1;
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bool IsEnqueued : 1;
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bool IsBrAnalyzable : 1;
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bool HasFallThrough : 1;
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bool IsUnpredicable : 1;
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bool CannotBeCopied : 1;
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bool ClobbersPred : 1;
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unsigned NonPredSize;
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MachineBasicBlock *BB;
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MachineBasicBlock *TrueBB;
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MachineBasicBlock *FalseBB;
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SmallVector<MachineOperand, 4> BrCond;
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SmallVector<MachineOperand, 4> Predicate;
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BBInfo() : IsDone(false), IsBeingAnalyzed(false),
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IsAnalyzed(false), IsEnqueued(false), IsBrAnalyzable(false),
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HasFallThrough(false), IsUnpredicable(false),
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CannotBeCopied(false), ClobbersPred(false), NonPredSize(0),
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BB(0), TrueBB(0), FalseBB(0) {}
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};
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/// IfcvtToken - Record information about pending if-conversions to attemp:
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/// BBI - Corresponding BBInfo.
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/// Kind - Type of block. See IfcvtKind.
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/// NeedSubsumption - True if the to-be-predicated BB has already been
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/// predicated.
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/// NumDups - Number of instructions that would be duplicated due
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/// to this if-conversion. (For diamonds, the number of
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/// identical instructions at the beginnings of both
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/// paths).
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/// NumDups2 - For diamonds, the number of identical instructions
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/// at the ends of both paths.
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struct IfcvtToken {
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BBInfo &BBI;
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IfcvtKind Kind;
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bool NeedSubsumption;
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unsigned NumDups;
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unsigned NumDups2;
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IfcvtToken(BBInfo &b, IfcvtKind k, bool s, unsigned d, unsigned d2 = 0)
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: BBI(b), Kind(k), NeedSubsumption(s), NumDups(d), NumDups2(d2) {}
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};
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/// Roots - Basic blocks that do not have successors. These are the starting
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/// points of Graph traversal.
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std::vector<MachineBasicBlock*> Roots;
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/// BBAnalysis - Results of if-conversion feasibility analysis indexed by
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/// basic block number.
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std::vector<BBInfo> BBAnalysis;
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const TargetLowering *TLI;
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const TargetInstrInfo *TII;
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bool MadeChange;
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int FnNum;
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public:
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static char ID;
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IfConverter() : MachineFunctionPass(&ID), FnNum(-1) {}
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virtual bool runOnMachineFunction(MachineFunction &MF);
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virtual const char *getPassName() const { return "If Converter"; }
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private:
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bool ReverseBranchCondition(BBInfo &BBI);
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bool ValidSimple(BBInfo &TrueBBI, unsigned &Dups) const;
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bool ValidTriangle(BBInfo &TrueBBI, BBInfo &FalseBBI,
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bool FalseBranch, unsigned &Dups) const;
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bool ValidDiamond(BBInfo &TrueBBI, BBInfo &FalseBBI,
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unsigned &Dups1, unsigned &Dups2) const;
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void ScanInstructions(BBInfo &BBI);
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BBInfo &AnalyzeBlock(MachineBasicBlock *BB,
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std::vector<IfcvtToken*> &Tokens);
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bool FeasibilityAnalysis(BBInfo &BBI, SmallVectorImpl<MachineOperand> &Cond,
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bool isTriangle = false, bool RevBranch = false);
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bool AnalyzeBlocks(MachineFunction &MF,
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std::vector<IfcvtToken*> &Tokens);
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void InvalidatePreds(MachineBasicBlock *BB);
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void RemoveExtraEdges(BBInfo &BBI);
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bool IfConvertSimple(BBInfo &BBI, IfcvtKind Kind);
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bool IfConvertTriangle(BBInfo &BBI, IfcvtKind Kind);
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bool IfConvertDiamond(BBInfo &BBI, IfcvtKind Kind,
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unsigned NumDups1, unsigned NumDups2);
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void PredicateBlock(BBInfo &BBI,
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MachineBasicBlock::iterator E,
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SmallVectorImpl<MachineOperand> &Cond);
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void CopyAndPredicateBlock(BBInfo &ToBBI, BBInfo &FromBBI,
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SmallVectorImpl<MachineOperand> &Cond,
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bool IgnoreBr = false);
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void MergeBlocks(BBInfo &ToBBI, BBInfo &FromBBI);
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bool MeetIfcvtSizeLimit(unsigned Size) const {
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return Size > 0 && Size <= TLI->getIfCvtBlockSizeLimit();
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}
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// blockAlwaysFallThrough - Block ends without a terminator.
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bool blockAlwaysFallThrough(BBInfo &BBI) const {
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return BBI.IsBrAnalyzable && BBI.TrueBB == NULL;
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}
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// IfcvtTokenCmp - Used to sort if-conversion candidates.
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static bool IfcvtTokenCmp(IfcvtToken *C1, IfcvtToken *C2) {
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int Incr1 = (C1->Kind == ICDiamond)
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? -(int)(C1->NumDups + C1->NumDups2) : (int)C1->NumDups;
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int Incr2 = (C2->Kind == ICDiamond)
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? -(int)(C2->NumDups + C2->NumDups2) : (int)C2->NumDups;
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if (Incr1 > Incr2)
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return true;
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else if (Incr1 == Incr2) {
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// Favors subsumption.
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if (C1->NeedSubsumption == false && C2->NeedSubsumption == true)
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return true;
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else if (C1->NeedSubsumption == C2->NeedSubsumption) {
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// Favors diamond over triangle, etc.
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if ((unsigned)C1->Kind < (unsigned)C2->Kind)
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return true;
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else if (C1->Kind == C2->Kind)
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return C1->BBI.BB->getNumber() < C2->BBI.BB->getNumber();
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}
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}
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return false;
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}
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};
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char IfConverter::ID = 0;
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}
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static RegisterPass<IfConverter>
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X("if-converter", "If Converter");
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FunctionPass *llvm::createIfConverterPass() { return new IfConverter(); }
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bool IfConverter::runOnMachineFunction(MachineFunction &MF) {
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TLI = MF.getTarget().getTargetLowering();
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TII = MF.getTarget().getInstrInfo();
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if (!TII) return false;
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DEBUG(errs() << "\nIfcvt: function (" << ++FnNum << ") \'"
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<< MF.getFunction()->getName() << "\'");
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if (FnNum < IfCvtFnStart || (IfCvtFnStop != -1 && FnNum > IfCvtFnStop)) {
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DEBUG(errs() << " skipped\n");
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return false;
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}
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DEBUG(errs() << "\n");
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MF.RenumberBlocks();
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BBAnalysis.resize(MF.getNumBlockIDs());
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// Look for root nodes, i.e. blocks without successors.
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for (MachineFunction::iterator I = MF.begin(), E = MF.end(); I != E; ++I)
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if (I->succ_empty())
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Roots.push_back(I);
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std::vector<IfcvtToken*> Tokens;
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MadeChange = false;
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unsigned NumIfCvts = NumSimple + NumSimpleFalse + NumTriangle +
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NumTriangleRev + NumTriangleFalse + NumTriangleFRev + NumDiamonds;
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while (IfCvtLimit == -1 || (int)NumIfCvts < IfCvtLimit) {
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// Do an initial analysis for each basic block and find all the potential
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// candidates to perform if-conversion.
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bool Change = AnalyzeBlocks(MF, Tokens);
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while (!Tokens.empty()) {
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IfcvtToken *Token = Tokens.back();
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Tokens.pop_back();
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BBInfo &BBI = Token->BBI;
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IfcvtKind Kind = Token->Kind;
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unsigned NumDups = Token->NumDups;
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unsigned NumDups2 = Token->NumDups2;
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delete Token;
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// If the block has been evicted out of the queue or it has already been
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// marked dead (due to it being predicated), then skip it.
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if (BBI.IsDone)
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BBI.IsEnqueued = false;
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if (!BBI.IsEnqueued)
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continue;
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BBI.IsEnqueued = false;
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bool RetVal = false;
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switch (Kind) {
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default: assert(false && "Unexpected!");
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break;
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case ICSimple:
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case ICSimpleFalse: {
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bool isFalse = Kind == ICSimpleFalse;
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if ((isFalse && DisableSimpleF) || (!isFalse && DisableSimple)) break;
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DEBUG(errs() << "Ifcvt (Simple" << (Kind == ICSimpleFalse ? " false" :"")
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<< "): BB#" << BBI.BB->getNumber() << " ("
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<< ((Kind == ICSimpleFalse)
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? BBI.FalseBB->getNumber()
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: BBI.TrueBB->getNumber()) << ") ");
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RetVal = IfConvertSimple(BBI, Kind);
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DEBUG(errs() << (RetVal ? "succeeded!" : "failed!") << "\n");
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if (RetVal) {
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if (isFalse) NumSimpleFalse++;
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else NumSimple++;
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}
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break;
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}
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case ICTriangle:
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case ICTriangleRev:
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case ICTriangleFalse:
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case ICTriangleFRev: {
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bool isFalse = Kind == ICTriangleFalse;
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bool isRev = (Kind == ICTriangleRev || Kind == ICTriangleFRev);
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if (DisableTriangle && !isFalse && !isRev) break;
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if (DisableTriangleR && !isFalse && isRev) break;
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if (DisableTriangleF && isFalse && !isRev) break;
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if (DisableTriangleFR && isFalse && isRev) break;
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DEBUG(errs() << "Ifcvt (Triangle");
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if (isFalse)
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DEBUG(errs() << " false");
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if (isRev)
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DEBUG(errs() << " rev");
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DEBUG(errs() << "): BB#" << BBI.BB->getNumber() << " (T:"
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<< BBI.TrueBB->getNumber() << ",F:"
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<< BBI.FalseBB->getNumber() << ") ");
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RetVal = IfConvertTriangle(BBI, Kind);
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DEBUG(errs() << (RetVal ? "succeeded!" : "failed!") << "\n");
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if (RetVal) {
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if (isFalse) {
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if (isRev) NumTriangleFRev++;
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else NumTriangleFalse++;
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} else {
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if (isRev) NumTriangleRev++;
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else NumTriangle++;
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}
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}
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break;
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}
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case ICDiamond: {
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if (DisableDiamond) break;
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DEBUG(errs() << "Ifcvt (Diamond): BB#" << BBI.BB->getNumber() << " (T:"
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<< BBI.TrueBB->getNumber() << ",F:"
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<< BBI.FalseBB->getNumber() << ") ");
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RetVal = IfConvertDiamond(BBI, Kind, NumDups, NumDups2);
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DEBUG(errs() << (RetVal ? "succeeded!" : "failed!") << "\n");
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if (RetVal) NumDiamonds++;
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break;
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}
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}
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Change |= RetVal;
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NumIfCvts = NumSimple + NumSimpleFalse + NumTriangle + NumTriangleRev +
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NumTriangleFalse + NumTriangleFRev + NumDiamonds;
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if (IfCvtLimit != -1 && (int)NumIfCvts >= IfCvtLimit)
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break;
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}
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if (!Change)
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break;
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MadeChange |= Change;
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}
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// Delete tokens in case of early exit.
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while (!Tokens.empty()) {
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IfcvtToken *Token = Tokens.back();
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Tokens.pop_back();
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delete Token;
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}
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Tokens.clear();
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Roots.clear();
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BBAnalysis.clear();
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if (MadeChange) {
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BranchFolder BF(false);
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BF.OptimizeFunction(MF, TII,
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MF.getTarget().getRegisterInfo(),
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getAnalysisIfAvailable<MachineModuleInfo>());
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}
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return MadeChange;
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}
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/// findFalseBlock - BB has a fallthrough. Find its 'false' successor given
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/// its 'true' successor.
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static MachineBasicBlock *findFalseBlock(MachineBasicBlock *BB,
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MachineBasicBlock *TrueBB) {
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for (MachineBasicBlock::succ_iterator SI = BB->succ_begin(),
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E = BB->succ_end(); SI != E; ++SI) {
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MachineBasicBlock *SuccBB = *SI;
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if (SuccBB != TrueBB)
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return SuccBB;
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}
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return NULL;
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}
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/// ReverseBranchCondition - Reverse the condition of the end of the block
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/// branch. Swap block's 'true' and 'false' successors.
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bool IfConverter::ReverseBranchCondition(BBInfo &BBI) {
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if (!TII->ReverseBranchCondition(BBI.BrCond)) {
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TII->RemoveBranch(*BBI.BB);
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TII->InsertBranch(*BBI.BB, BBI.FalseBB, BBI.TrueBB, BBI.BrCond);
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std::swap(BBI.TrueBB, BBI.FalseBB);
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return true;
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}
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return false;
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}
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/// getNextBlock - Returns the next block in the function blocks ordering. If
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/// it is the end, returns NULL.
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static inline MachineBasicBlock *getNextBlock(MachineBasicBlock *BB) {
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MachineFunction::iterator I = BB;
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MachineFunction::iterator E = BB->getParent()->end();
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if (++I == E)
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return NULL;
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return I;
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}
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/// ValidSimple - Returns true if the 'true' block (along with its
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/// predecessor) forms a valid simple shape for ifcvt. It also returns the
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/// number of instructions that the ifcvt would need to duplicate if performed
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/// in Dups.
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bool IfConverter::ValidSimple(BBInfo &TrueBBI, unsigned &Dups) const {
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Dups = 0;
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if (TrueBBI.IsBeingAnalyzed || TrueBBI.IsDone)
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return false;
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if (TrueBBI.IsBrAnalyzable)
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return false;
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if (TrueBBI.BB->pred_size() > 1) {
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if (TrueBBI.CannotBeCopied ||
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TrueBBI.NonPredSize > TLI->getIfCvtDupBlockSizeLimit())
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return false;
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Dups = TrueBBI.NonPredSize;
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}
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return true;
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}
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/// ValidTriangle - Returns true if the 'true' and 'false' blocks (along
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/// with their common predecessor) forms a valid triangle shape for ifcvt.
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/// If 'FalseBranch' is true, it checks if 'true' block's false branch
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/// branches to the false branch rather than the other way around. It also
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/// returns the number of instructions that the ifcvt would need to duplicate
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/// if performed in 'Dups'.
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bool IfConverter::ValidTriangle(BBInfo &TrueBBI, BBInfo &FalseBBI,
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bool FalseBranch, unsigned &Dups) const {
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Dups = 0;
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if (TrueBBI.IsBeingAnalyzed || TrueBBI.IsDone)
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return false;
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if (TrueBBI.BB->pred_size() > 1) {
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if (TrueBBI.CannotBeCopied)
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return false;
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unsigned Size = TrueBBI.NonPredSize;
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if (TrueBBI.IsBrAnalyzable) {
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if (TrueBBI.TrueBB && TrueBBI.BrCond.empty())
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// Ends with an unconditional branch. It will be removed.
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--Size;
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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;
|
|
|
|
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.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;
|
|
|
|
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);
|
|
if (!BBI.FalseBB) {
|
|
// Malformed bcc? True and false blocks are the same?
|
|
BBI.IsUnpredicable = true;
|
|
return;
|
|
}
|
|
}
|
|
|
|
// Then scan all the instructions.
|
|
BBI.NonPredSize = 0;
|
|
BBI.ClobbersPred = 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) {
|
|
// 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 (!TII->isPredicable(I)) {
|
|
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;
|
|
}
|
|
|
|
// Do not ifcvt if true and false fallthrough blocks are the same.
|
|
if (!BBI.FalseBB) {
|
|
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
|
|
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---> exit
|
|
// |
|
|
// FBB
|
|
Tokens.push_back(new IfcvtToken(BBI, ICSimple, TNeedSub, Dups));
|
|
Enqueued = true;
|
|
}
|
|
|
|
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;
|
|
}
|
|
|
|
/// 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;
|
|
}
|
|
|
|
/// 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 InsertUncondBranch(MachineBasicBlock *BB, MachineBasicBlock *ToBB,
|
|
const TargetInstrInfo *TII) {
|
|
SmallVector<MachineOperand, 0> NoCond;
|
|
TII->InsertBranch(*BB, ToBB, NULL, NoCond);
|
|
}
|
|
|
|
/// 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::IfConvertSimple(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 == ICSimpleFalse)
|
|
std::swap(CvtBBI, NextBBI);
|
|
|
|
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;
|
|
}
|
|
|
|
if (Kind == ICSimpleFalse)
|
|
if (TII->ReverseBranchCondition(Cond))
|
|
assert(false && "Unable to reverse branch condition!");
|
|
|
|
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);
|
|
|
|
// Merge converted block into entry block.
|
|
BBI.NonPredSize -= TII->RemoveBranch(*BBI.BB);
|
|
MergeBlocks(BBI, *CvtBBI);
|
|
}
|
|
|
|
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;
|
|
}
|
|
|
|
/// IfConvertTriangle - If convert a triangle sub-CFG.
|
|
///
|
|
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);
|
|
|
|
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;
|
|
}
|
|
|
|
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.
|
|
CvtBBI->NonPredSize -= TII->RemoveBranch(*CvtBBI->BB);
|
|
PredicateBlock(*CvtBBI, CvtBBI->BB->end(), Cond);
|
|
|
|
// 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 {
|
|
InsertUncondBranch(BBI.BB, NextBBI->BB, TII);
|
|
BBI.HasFallThrough = false;
|
|
}
|
|
// Mixed predicated and unpredicated code. This cannot be iteratively
|
|
// predicated.
|
|
IterIfcvt = false;
|
|
}
|
|
|
|
RemoveExtraEdges(BBI);
|
|
|
|
// 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.
|
|
return true;
|
|
}
|
|
|
|
/// 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;
|
|
}
|
|
|
|
// 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 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)) {
|
|
#ifndef NDEBUG
|
|
errs() << "Unable to predicate " << *I << "!\n";
|
|
#endif
|
|
llvm_unreachable(0);
|
|
}
|
|
}
|
|
|
|
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)) {
|
|
#ifndef NDEBUG
|
|
errs() << "Unable to predicate " << *I << "!\n";
|
|
#endif
|
|
llvm_unreachable(0);
|
|
}
|
|
}
|
|
|
|
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());
|
|
|
|
// 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->isSuccessor(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;
|
|
}
|