//===-- IfConversion.cpp - Machine code if conversion pass. ---------------===// // // 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 implements the machine instruction level if-conversion pass. // //===----------------------------------------------------------------------===// #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/Debug.h" #include "llvm/ADT/DepthFirstIterator.h" #include "llvm/ADT/Statistic.h" using namespace llvm; STATISTIC(NumSimple, "Number of simple if-conversions performed"); STATISTIC(NumSimpleRev, "Number of simple (reversed) if-conversions performed"); STATISTIC(NumTriangle, "Number of triangle if-conversions performed"); STATISTIC(NumDiamonds, "Number of diamond if-conversions performed"); STATISTIC(NumIfConvBBs, "Number of if-converted blocks"); namespace { class IfConverter : public MachineFunctionPass { enum BBICKind { ICNotAnalyzed, // BB has not been analyzed. ICReAnalyze, // BB must be re-analyzed. ICNotClassfied, // BB data valid, but not classified. ICSimple, // BB is entry of an one split, no rejoin sub-CFG. ICSimpleFalse, // Same as ICSimple, but on the false path. ICTriangle, // BB is entry of a triangle sub-CFG. ICDiamond, // BB is entry of a diamond sub-CFG. ICChild, // BB is part of the sub-CFG that'll be predicated. ICDead // BB has been converted and merged, it's now dead. }; /// 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), its size, whether it's predicable, and whether any /// instruction can clobber the 'would-be' predicate. /// /// Kind - Type of block. See BBICKind. /// NonPredSize - Number of non-predicated instructions. /// IsAnalyzable - True if AnalyzeBranch() returns false. /// ModifyPredicate - FIXME: Not used right now. True if BB would modify /// the predicate (e.g. has cmp, call, etc.) /// 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; unsigned NonPredSize; bool IsAnalyzable; bool ModifyPredicate; MachineBasicBlock *BB; MachineBasicBlock *TrueBB; MachineBasicBlock *FalseBB; MachineBasicBlock *TailBB; std::vector BrCond; std::vector Predicate; BBInfo() : Kind(ICNotAnalyzed), NonPredSize(0), IsAnalyzable(false), ModifyPredicate(false), BB(0), TrueBB(0), FalseBB(0), TailBB(0) {} }; /// Roots - Basic blocks that do not have successors. These are the starting /// points of Graph traversal. std::vector Roots; /// BBAnalysis - Results of if-conversion feasibility analysis indexed by /// basic block number. std::vector BBAnalysis; const TargetLowering *TLI; const TargetInstrInfo *TII; bool MadeChange; public: static char ID; IfConverter() : MachineFunctionPass((intptr_t)&ID) {} virtual bool runOnMachineFunction(MachineFunction &MF); virtual const char *getPassName() const { return "If converter"; } private: bool ReverseBranchCondition(BBInfo &BBI); void StructuralAnalysis(MachineBasicBlock *BB); bool FeasibilityAnalysis(BBInfo &BBI, std::vector &Cond, bool IgnoreTerm = false); bool AttemptRestructuring(BBInfo &BBI); bool AnalyzeBlocks(MachineFunction &MF, std::vector &Candidates); void ReTryPreds(MachineBasicBlock *BB); bool IfConvertSimple(BBInfo &BBI); bool IfConvertTriangle(BBInfo &BBI); bool IfConvertDiamond(BBInfo &BBI); void PredicateBlock(BBInfo &BBI, std::vector &Cond, bool IgnoreTerm = false); void MergeBlocks(BBInfo &TrueBBI, BBInfo &FalseBBI); // IfcvtCandidateCmp - Used to sort if-conversion candidates. static bool IfcvtCandidateCmp(BBInfo* C1, BBInfo* C2){ // Favor diamond over triangle, etc. return (unsigned)C1->Kind < (unsigned)C2->Kind; } }; char IfConverter::ID = 0; } FunctionPass *llvm::createIfConverterPass() { return new IfConverter(); } bool IfConverter::runOnMachineFunction(MachineFunction &MF) { TLI = MF.getTarget().getTargetLowering(); TII = MF.getTarget().getInstrInfo(); if (!TII) return false; DOUT << "\nIfcvt: function \'" << MF.getFunction()->getName() << "\'\n"; MF.RenumberBlocks(); 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_size() == 0) Roots.push_back(I); std::vector Candidates; MadeChange = false; while (true) { // Do an intial analysis for each basic block and finding all the potential // candidates to perform if-convesion. bool Change = AnalyzeBlocks(MF, Candidates); while (!Candidates.empty()) { BBInfo &BBI = *Candidates.back(); Candidates.pop_back(); bool RetVal = false; switch (BBI.Kind) { default: assert(false && "Unexpected!"); break; case ICReAnalyze: // One or more of 'children' have been modified, abort! case ICDead: // Block has been already been if-converted, abort! break; case ICSimple: case ICSimpleFalse: DOUT << "Ifcvt (Simple" << (BBI.Kind == ICSimpleFalse ? " false" : "") << "): BB#" << BBI.BB->getNumber() << " "; RetVal = IfConvertSimple(BBI); DOUT << (RetVal ? "succeeded!" : "failed!") << "\n"; if (RetVal) if (BBI.Kind == ICSimple) NumSimple++; else NumSimpleRev++; break; case ICTriangle: DOUT << "Ifcvt (Triangle): BB#" << BBI.BB->getNumber() << " "; RetVal = IfConvertTriangle(BBI); DOUT << (RetVal ? "succeeded!" : "failed!") << "\n"; if (RetVal) NumTriangle++; break; case ICDiamond: DOUT << "Ifcvt (Diamond): BB#" << BBI.BB->getNumber() << " "; RetVal = IfConvertDiamond(BBI); DOUT << (RetVal ? "succeeded!" : "failed!") << "\n"; if (RetVal) NumDiamonds++; break; } Change |= RetVal; } if (!Change) break; MadeChange |= Change; } Roots.clear(); BBAnalysis.clear(); return MadeChange; } static MachineBasicBlock *findFalseBlock(MachineBasicBlock *BB, MachineBasicBlock *TrueBB) { for (MachineBasicBlock::succ_iterator SI = BB->succ_begin(), E = BB->succ_end(); SI != E; ++SI) { MachineBasicBlock *SuccBB = *SI; if (SuccBB != TrueBB) return SuccBB; } return NULL; } 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; } /// StructuralAnalysis - Analyze the structure of the sub-CFG starting from /// the specified block. Record its successors and whether it looks like an /// if-conversion candidate. void IfConverter::StructuralAnalysis(MachineBasicBlock *BB) { BBInfo &BBI = BBAnalysis[BB->getNumber()]; if (BBI.Kind == ICReAnalyze) { BBI.BrCond.clear(); BBI.TrueBB = BBI.FalseBB = NULL; } else { if (BBI.Kind != ICNotAnalyzed) return; // Already analyzed. BBI.BB = BB; BBI.NonPredSize = std::distance(BB->begin(), BB->end()); } // Look for 'root' of a simple (non-nested) triangle or diamond. BBI.Kind = ICNotClassfied; BBI.IsAnalyzable = !TII->AnalyzeBranch(*BB, BBI.TrueBB, BBI.FalseBB, BBI.BrCond); if (!BBI.IsAnalyzable || BBI.BrCond.size() == 0) return; // Do not ifcvt if either path is a back edge to the entry block. if (BBI.TrueBB == BB || BBI.FalseBB == BB) return; StructuralAnalysis(BBI.TrueBB); BBInfo &TrueBBI = BBAnalysis[BBI.TrueBB->getNumber()]; // 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!"); StructuralAnalysis(BBI.FalseBB); BBInfo &FalseBBI = BBAnalysis[BBI.FalseBB->getNumber()]; // Look for more opportunities to if-convert a triangle. Try to restructure // the CFG to form a triangle with the 'false' path. std::vector RevCond(BBI.BrCond); bool CanRevCond = !TII->ReverseBranchCondition(RevCond); if (FalseBBI.FalseBB) { if (TrueBBI.TrueBB && TrueBBI.TrueBB == BBI.FalseBB) return; std::vector Cond(BBI.BrCond); if (CanRevCond && FalseBBI.TrueBB && FalseBBI.BB->pred_size() == 1 && FeasibilityAnalysis(FalseBBI, RevCond, true)) { std::vector FalseCond(FalseBBI.BrCond); if (FalseBBI.TrueBB == BBI.TrueBB && TII->SubsumesPredicate(FalseCond, BBI.BrCond)) { // Reverse 'true' and 'false' paths. ReverseBranchCondition(BBI); BBI.Kind = ICTriangle; FalseBBI.Kind = ICChild; } else if (FalseBBI.FalseBB == BBI.TrueBB && !TII->ReverseBranchCondition(FalseCond) && TII->SubsumesPredicate(FalseCond, BBI.BrCond)) { // Reverse 'false' block's 'true' and 'false' paths and then // reverse 'true' and 'false' paths. ReverseBranchCondition(FalseBBI); ReverseBranchCondition(BBI); BBI.Kind = ICTriangle; FalseBBI.Kind = ICChild; } } } else if (TrueBBI.TrueBB == FalseBBI.TrueBB && CanRevCond && TrueBBI.BB->pred_size() == 1 && FalseBBI.BB->pred_size() == 1 && // Check the 'true' and 'false' blocks if either isn't ended with // a branch. If the block does not fallthrough to another block // then we need to add a branch to its successor. !(TrueBBI.ModifyPredicate && !TrueBBI.TrueBB && TrueBBI.BB->succ_size()) && !(FalseBBI.ModifyPredicate && !FalseBBI.TrueBB && FalseBBI.BB->succ_size()) && FeasibilityAnalysis(TrueBBI, BBI.BrCond) && FeasibilityAnalysis(FalseBBI, RevCond)) { // Diamond: // EBB // / \_ // | | // TBB FBB // \ / // TailBB // Note TailBB can be empty. BBI.Kind = ICDiamond; TrueBBI.Kind = FalseBBI.Kind = ICChild; BBI.TailBB = TrueBBI.TrueBB; } else { // FIXME: Consider duplicating if BB is small. bool TryTriangle = TrueBBI.TrueBB && TrueBBI.TrueBB == BBI.FalseBB && BBI.TrueBB->pred_size() == 1; bool TrySimple = TrueBBI.BrCond.size() == 0 && BBI.TrueBB->pred_size() == 1; if ((TryTriangle || TrySimple) && FeasibilityAnalysis(TrueBBI, BBI.BrCond)) { if (TryTriangle) { // Triangle: // EBB // | \_ // | | // | TBB // | / // FBB BBI.Kind = ICTriangle; TrueBBI.Kind = ICChild; } else { // Simple (split, no rejoin): // EBB // | \_ // | | // | TBB---> exit // | // FBB BBI.Kind = ICSimple; TrueBBI.Kind = ICChild; } } else if (FalseBBI.BrCond.size() == 0 && BBI.FalseBB->pred_size() == 1) { // Try 'simple' on the other path... std::vector RevCond(BBI.BrCond); if (TII->ReverseBranchCondition(RevCond)) assert(false && "Unable to reverse branch condition!"); if (FeasibilityAnalysis(FalseBBI, RevCond)) { BBI.Kind = ICSimpleFalse; FalseBBI.Kind = ICChild; } } } return; } /// FeasibilityAnalysis - Determine if the block is predicable. In most /// cases, that means all the instructions in the block has M_PREDICABLE flag. /// 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. If IgnoreTerm is true then /// all the terminator instructions are skipped. bool IfConverter::FeasibilityAnalysis(BBInfo &BBI, std::vector &Cond, bool IgnoreTerm) { // If the block is dead, or it is going to be the entry block of a sub-CFG // that will be if-converted, then it cannot be predicated. if (BBI.Kind != ICNotAnalyzed && BBI.Kind != ICNotClassfied && BBI.Kind != ICChild) return false; // Check predication threshold. if (BBI.NonPredSize == 0 || BBI.NonPredSize > TLI->getIfCvtBlockSizeLimit()) return false; // If it is already predicated, check if its predicate subsumes the new // predicate. if (BBI.Predicate.size() && !TII->SubsumesPredicate(BBI.Predicate, Cond)) return false; for (MachineBasicBlock::iterator I = BBI.BB->begin(), E = BBI.BB->end(); I != E; ++I) { if (IgnoreTerm && TII->isTerminatorInstr(I->getOpcode())) continue; // TODO: check if instruction clobbers predicate. if (!I->isPredicable()) return false; } return true; } /// AttemptRestructuring - Restructure the sub-CFG rooted in the given block to /// expose more if-conversion opportunities. e.g. /// /// cmp /// b le BB1 /// / \____ /// / | /// cmp | /// b eq BB1 | /// / \____ | /// / \ | /// BB1 /// ==> /// /// cmp /// b eq BB1 /// / \____ /// / | /// cmp | /// b le BB1 | /// / \____ | /// / \ | /// BB1 bool IfConverter::AttemptRestructuring(BBInfo &BBI) { return false; } /// 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 &Candidates) { bool Change = false; std::set Visited; for (unsigned i = 0, e = Roots.size(); i != e; ++i) { for (idf_ext_iterator I=idf_ext_begin(Roots[i],Visited), E = idf_ext_end(Roots[i], Visited); I != E; ++I) { MachineBasicBlock *BB = *I; StructuralAnalysis(BB); BBInfo &BBI = BBAnalysis[BB->getNumber()]; switch (BBI.Kind) { case ICSimple: case ICSimpleFalse: case ICTriangle: case ICDiamond: Candidates.push_back(&BBI); break; default: Change |= AttemptRestructuring(BBI); break; } } } // Sort to favor more complex ifcvt scheme. std::stable_sort(Candidates.begin(), Candidates.end(), IfcvtCandidateCmp); return Change; } /// isNextBlock - Returns true either if ToBB the next block after BB or /// that all the intervening blocks are empty. static bool isNextBlock(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; } /// ReTryPreds - Invalidate predecessor BB info so it would be re-analyzed /// to determine if it can be if-converted. void IfConverter::ReTryPreds(MachineBasicBlock *BB) { for (MachineBasicBlock::pred_iterator PI = BB->pred_begin(), E = BB->pred_end(); PI != E; ++PI) { BBInfo &PBBI = BBAnalysis[(*PI)->getNumber()]; PBBI.Kind = ICReAnalyze; } } /// InsertUncondBranch - Inserts an unconditional branch from BB to ToBB. /// static void InsertUncondBranch(MachineBasicBlock *BB, MachineBasicBlock *ToBB, const TargetInstrInfo *TII) { std::vector NoCond; TII->InsertBranch(*BB, ToBB, NULL, NoCond); } /// IfConvertSimple - If convert a simple (split, no rejoin) sub-CFG. /// bool IfConverter::IfConvertSimple(BBInfo &BBI) { bool ReverseCond = BBI.Kind == ICSimpleFalse; BBI.Kind = ICNotClassfied; BBInfo &TrueBBI = BBAnalysis[BBI.TrueBB->getNumber()]; BBInfo &FalseBBI = BBAnalysis[BBI.FalseBB->getNumber()]; BBInfo *CvtBBI = &TrueBBI; BBInfo *NextBBI = &FalseBBI; std::vector Cond(BBI.BrCond); if (ReverseCond) { std::swap(CvtBBI, NextBBI); TII->ReverseBranchCondition(Cond); } PredicateBlock(*CvtBBI, Cond); // If the 'true' block ends without a branch, add a conditional branch // to its successor unless that happens to be the 'false' block. if (CvtBBI->IsAnalyzable && CvtBBI->TrueBB == NULL) { assert(CvtBBI->BB->succ_size() == 1 && "Unexpected!"); MachineBasicBlock *SuccBB = *CvtBBI->BB->succ_begin(); if (SuccBB != NextBBI->BB) TII->InsertBranch(*CvtBBI->BB, SuccBB, NULL, Cond); } // Merge converted block into entry block. Also add an unconditional branch // to the 'false' branch. BBI.NonPredSize -= TII->RemoveBranch(*BBI.BB); MergeBlocks(BBI, *CvtBBI); if (!isNextBlock(BBI.BB, NextBBI->BB)) InsertUncondBranch(BBI.BB, NextBBI->BB, TII); std::copy(Cond.begin(), Cond.end(), std::back_inserter(BBI.Predicate)); // Update block info. BB can be iteratively if-converted. BBI.Kind = ICReAnalyze; ReTryPreds(BBI.BB); CvtBBI->Kind = ICDead; // FIXME: Must maintain LiveIns. return true; } /// IfConvertTriangle - If convert a triangle sub-CFG. /// bool IfConverter::IfConvertTriangle(BBInfo &BBI) { BBI.Kind = ICNotClassfied; BBInfo &TrueBBI = BBAnalysis[BBI.TrueBB->getNumber()]; // Predicate the 'true' block after removing its branch. TrueBBI.NonPredSize -= TII->RemoveBranch(*BBI.TrueBB); PredicateBlock(TrueBBI, BBI.BrCond); // If 'true' block has a 'false' successor, add an exit branch to it. bool HasEarlyExit = TrueBBI.FalseBB != NULL; if (HasEarlyExit) { std::vector RevCond(TrueBBI.BrCond); if (TII->ReverseBranchCondition(RevCond)) assert(false && "Unable to reverse branch condition!"); TII->InsertBranch(*BBI.TrueBB, TrueBBI.FalseBB, NULL, RevCond); } // Join the 'true' and 'false' blocks if the 'false' block has no other // predecessors. Otherwise, add a unconditional branch from 'true' to 'false'. BBInfo &FalseBBI = BBAnalysis[BBI.FalseBB->getNumber()]; bool FalseBBDead = false; if (!HasEarlyExit && FalseBBI.BB->pred_size() == 2) { MergeBlocks(TrueBBI, FalseBBI); FalseBBDead = true; } else if (!isNextBlock(TrueBBI.BB, FalseBBI.BB)) InsertUncondBranch(TrueBBI.BB, FalseBBI.BB, TII); // Now merge the entry of the triangle with the true block. BBI.NonPredSize -= TII->RemoveBranch(*BBI.BB); MergeBlocks(BBI, TrueBBI); std::copy(BBI.BrCond.begin(), BBI.BrCond.end(), std::back_inserter(BBI.Predicate)); // Update block info. BB can be iteratively if-converted. BBI.Kind = ICReAnalyze; ReTryPreds(BBI.BB); TrueBBI.Kind = ICDead; if (FalseBBDead) FalseBBI.Kind = ICDead; // FIXME: Must maintain LiveIns. return true; } /// IfConvertDiamond - If convert a diamond sub-CFG. /// bool IfConverter::IfConvertDiamond(BBInfo &BBI) { BBI.Kind = ICNotClassfied; BBInfo &TrueBBI = BBAnalysis[BBI.TrueBB->getNumber()]; BBInfo &FalseBBI = BBAnalysis[BBI.FalseBB->getNumber()]; SmallVector 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! } ++TT; } while (FT != BBI.FalseBB->end()) { if (!FT->isPredicable()) { return false; // Can't if-convert. Abort! } ++FT; } } // Remove the duplicated instructions from the 'true' block. for (unsigned i = 0, e = Dups.size(); i != e; ++i) { Dups[i]->eraseFromParent(); --TrueBBI.NonPredSize; } // 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; std::vector RevCond(BBI.BrCond); TII->ReverseBranchCondition(RevCond); std::vector *Cond1 = &BBI.BrCond; std::vector *Cond2 = &RevCond; if (TrueBBI.ModifyPredicate) { std::swap(BBI1, BBI2); std::swap(Cond1, Cond2); } // Check the 'true' and 'false' blocks if either isn't ended with a branch. // Either the block fallthrough to another block or it ends with a // return. If it's the former, add a branch to its successor. bool NeedBr1 = !BBI1->TrueBB && BBI1->BB->succ_size(); bool NeedBr2 = !BBI2->TrueBB && BBI1->BB->succ_size(); // Predicate the 'true' block after removing its branch. BBI1->NonPredSize -= TII->RemoveBranch(*BBI1->BB); PredicateBlock(*BBI1, *Cond1); // Add an early exit branch if needed. if (NeedBr1) TII->InsertBranch(*BBI1->BB, *BBI1->BB->succ_begin(), NULL, *Cond1); // Predicate the 'false' block. PredicateBlock(*BBI2, *Cond2, true); // Add an unconditional branch from 'false' to to 'false' successor if it // will not be the fallthrough block. if (NeedBr2 && !isNextBlock(BBI2->BB, *BBI2->BB->succ_begin())) InsertUncondBranch(BBI2->BB, *BBI2->BB->succ_begin(), TII); // Keep them as two separate blocks if there is an early exit. if (!NeedBr1) MergeBlocks(*BBI1, *BBI2); else if (!isNextBlock(BBI1->BB, BBI2->BB)) InsertUncondBranch(BBI1->BB, BBI2->BB, TII); // Remove the conditional branch from entry to the blocks. BBI.NonPredSize -= TII->RemoveBranch(*BBI.BB); // Merge the combined block into the entry of the diamond. MergeBlocks(BBI, *BBI1); // If the if-converted block fallthrough or unconditionally branch into the // tail block, and the tail block does not have other predecessors, then // fold the tail block in as well. BBInfo *CvtBBI = NeedBr1 ? BBI2 : &BBI; if (BBI.TailBB && BBI.TailBB->pred_size() == 1 && CvtBBI->BB->succ_size() == 1) { CvtBBI->NonPredSize -= TII->RemoveBranch(*CvtBBI->BB); BBInfo TailBBI = BBAnalysis[BBI.TailBB->getNumber()]; MergeBlocks(*CvtBBI, TailBBI); TailBBI.Kind = ICDead; } // Update block info. TrueBBI.Kind = ICDead; FalseBBI.Kind = ICDead; // 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(BBInfo &BBI, std::vector &Cond, bool IgnoreTerm) { for (MachineBasicBlock::iterator I = BBI.BB->begin(), E = BBI.BB->end(); I != E; ++I) { if (IgnoreTerm && TII->isTerminatorInstr(I->getOpcode())) continue; if (TII->isPredicated(I)) continue; if (!TII->PredicateInstruction(I, Cond)) { cerr << "Unable to predicate " << *I << "!\n"; abort(); } } BBI.NonPredSize = 0; NumIfConvBBs++; } /// TransferPreds - Transfer all the predecessors of FromBB to ToBB. /// static void TransferPreds(MachineBasicBlock *ToBB, MachineBasicBlock *FromBB) { for (MachineBasicBlock::pred_iterator I = FromBB->pred_begin(), E = FromBB->pred_end(); I != E; ++I) { MachineBasicBlock *Pred = *I; Pred->removeSuccessor(FromBB); if (!Pred->isSuccessor(ToBB)) Pred->addSuccessor(ToBB); } } /// TransferSuccs - Transfer all the successors of FromBB to ToBB. /// static void TransferSuccs(MachineBasicBlock *ToBB, MachineBasicBlock *FromBB) { for (MachineBasicBlock::succ_iterator I = FromBB->succ_begin(), E = FromBB->succ_end(); I != E; ++I) { MachineBasicBlock *Succ = *I; FromBB->removeSuccessor(Succ); if (!ToBB->isSuccessor(Succ)) ToBB->addSuccessor(Succ); } } /// 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()); // If FromBBI is previously a successor, remove it from ToBBI's successor // list and update its TrueBB / FalseBB field if needed. if (ToBBI.BB->isSuccessor(FromBBI.BB)) ToBBI.BB->removeSuccessor(FromBBI.BB); // Redirect all branches to FromBB to ToBB. std::vector Preds(FromBBI.BB->pred_begin(), FromBBI.BB->pred_end()); for (unsigned i = 0, e = Preds.size(); i != e; ++i) Preds[i]->ReplaceUsesOfBlockWith(FromBBI.BB, ToBBI.BB); // Transfer preds / succs and update size. TransferPreds(ToBBI.BB, FromBBI.BB); TransferSuccs(ToBBI.BB, FromBBI.BB); ToBBI.NonPredSize += FromBBI.NonPredSize; FromBBI.NonPredSize = 0; }