diff options
author | Evan Cheng <evan.cheng@apple.com> | 2007-06-04 06:47:22 +0000 |
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committer | Evan Cheng <evan.cheng@apple.com> | 2007-06-04 06:47:22 +0000 |
commit | b6665f62c5cb19a04c4bb0eecbc498d406ec85b3 (patch) | |
tree | 83e623720fa3c1b1da6ec3b2fa29b27a30937f46 /lib/CodeGen/IfConversion.cpp | |
parent | 0370fad74b48388412c52d1325512f2c218487fa (diff) | |
download | external_llvm-b6665f62c5cb19a04c4bb0eecbc498d406ec85b3.zip external_llvm-b6665f62c5cb19a04c4bb0eecbc498d406ec85b3.tar.gz external_llvm-b6665f62c5cb19a04c4bb0eecbc498d406ec85b3.tar.bz2 |
Let IfConverter loose. Allow more aggressive subsumptions; reorder basic blocks to expose more ifcvt opportunities; code clean up and fixes.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@37409 91177308-0d34-0410-b5e6-96231b3b80d8
Diffstat (limited to 'lib/CodeGen/IfConversion.cpp')
-rw-r--r-- | lib/CodeGen/IfConversion.cpp | 460 |
1 files changed, 264 insertions, 196 deletions
diff --git a/lib/CodeGen/IfConversion.cpp b/lib/CodeGen/IfConversion.cpp index 9efceb0..57862eb 100644 --- a/lib/CodeGen/IfConversion.cpp +++ b/lib/CodeGen/IfConversion.cpp @@ -24,6 +24,10 @@ #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 { @@ -32,8 +36,8 @@ namespace { ICNotAnalyzed, // BB has not been analyzed. ICReAnalyze, // BB must be re-analyzed. ICNotClassfied, // BB data valid, but not classified. - ICEarlyExit, // BB is entry of an early-exit sub-CFG. - ICEarlyExitFalse,// Same as ICEarlyExit, but on the false path. + 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. @@ -49,8 +53,7 @@ namespace { /// /// Kind - Type of block. See BBICKind. /// NonPredSize - Number of non-predicated instructions. - /// isPredicable - Is it predicable. (FIXME: Remove.) - /// hasEarlyExit - Ends with a return, indirect jump or br to jumptable. + /// 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. @@ -60,8 +63,7 @@ namespace { struct BBInfo { BBICKind Kind; unsigned NonPredSize; - bool isPredicable; - bool hasEarlyExit; + bool IsAnalyzable; bool ModifyPredicate; MachineBasicBlock *BB; MachineBasicBlock *TrueBB; @@ -69,8 +71,8 @@ namespace { MachineBasicBlock *TailBB; std::vector<MachineOperand> BrCond; std::vector<MachineOperand> Predicate; - BBInfo() : Kind(ICNotAnalyzed), NonPredSize(0), isPredicable(false), - hasEarlyExit(false), ModifyPredicate(false), + BBInfo() : Kind(ICNotAnalyzed), NonPredSize(0), + IsAnalyzable(false), ModifyPredicate(false), BB(0), TrueBB(0), FalseBB(0), TailBB(0) {} }; @@ -93,14 +95,16 @@ namespace { virtual const char *getPassName() const { return "If converter"; } private: + bool ReverseBranchCondition(BBInfo &BBI); void StructuralAnalysis(MachineBasicBlock *BB); - void FeasibilityAnalysis(BBInfo &BBI, - std::vector<MachineOperand> &Cond); + bool FeasibilityAnalysis(BBInfo &BBI, + std::vector<MachineOperand> &Cond, + bool IgnoreTerm = false); bool AttemptRestructuring(BBInfo &BBI); bool AnalyzeBlocks(MachineFunction &MF, std::vector<BBInfo*> &Candidates); void ReTryPreds(MachineBasicBlock *BB); - bool IfConvertEarlyExit(BBInfo &BBI); + bool IfConvertSimple(BBInfo &BBI); bool IfConvertTriangle(BBInfo &BBI); bool IfConvertDiamond(BBInfo &BBI); void PredicateBlock(BBInfo &BBI, @@ -137,39 +141,49 @@ bool IfConverter::runOnMachineFunction(MachineFunction &MF) { std::vector<BBInfo*> Candidates; MadeChange = false; while (true) { - bool Change = false; - // Do an intial analysis for each basic block and finding all the potential // candidates to perform if-convesion. - Change |= AnalyzeBlocks(MF, Candidates); + 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 'childrean' have been modified, abort! break; - case ICEarlyExit: - case ICEarlyExitFalse: - DOUT << "Ifcvt (Early exit): BB#" << BBI.BB->getNumber() << "\n"; - Change |= IfConvertEarlyExit(BBI); - 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() << "\n"; - Change |= IfConvertTriangle(BBI); + 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() << "\n"; - Change |= IfConvertDiamond(BBI); + DOUT << "Ifcvt (Diamond): BB#" << BBI.BB->getNumber() << " "; + RetVal = IfConvertDiamond(BBI); + DOUT << (RetVal ? "succeeded!" : "failed!") << "\n"; + if (RetVal) NumDiamonds++; break; } + Change |= RetVal; } - MadeChange |= Change; if (!Change) break; + MadeChange |= Change; } Roots.clear(); @@ -189,13 +203,25 @@ static MachineBasicBlock *findFalseBlock(MachineBasicBlock *BB, 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) { + if (BBI.Kind == ICReAnalyze) + BBI.BrCond.clear(); + else { if (BBI.Kind != ICNotAnalyzed) return; // Already analyzed. BBI.BB = BB; @@ -204,57 +230,64 @@ void IfConverter::StructuralAnalysis(MachineBasicBlock *BB) { // Look for 'root' of a simple (non-nested) triangle or diamond. BBI.Kind = ICNotClassfied; - bool CanAnalyze = !TII->AnalyzeBranch(*BB, BBI.TrueBB, BBI.FalseBB, - BBI.BrCond); - // Does it end with a return, indirect jump, or jumptable branch? - BBI.hasEarlyExit = TII->BlockHasNoFallThrough(*BB) && !BBI.TrueBB; - if (!CanAnalyze || !BBI.TrueBB || BBI.BrCond.size() == 0) + BBI.IsAnalyzable = + !TII->AnalyzeBranch(*BB, BBI.TrueBB, BBI.FalseBB, BBI.BrCond); + if (!BBI.IsAnalyzable || BBI.BrCond.size() == 0) return; - // Not a candidate if 'true' block is going to be if-converted. StructuralAnalysis(BBI.TrueBB); BBInfo &TrueBBI = BBAnalysis[BBI.TrueBB->getNumber()]; - // TODO: Only handle very simple cases for now. - if (TrueBBI.FalseBB || TrueBBI.BrCond.size()) - return; - // 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!"); - // Not a candidate if 'false' block is going to be if-converted. StructuralAnalysis(BBI.FalseBB); BBInfo &FalseBBI = BBAnalysis[BBI.FalseBB->getNumber()]; - - // TODO: Only handle very simple cases for now. - if (FalseBBI.FalseBB || FalseBBI.BrCond.size()) - return; - - unsigned TrueNumPreds = BBI.TrueBB->pred_size(); - unsigned FalseNumPreds = BBI.FalseBB->pred_size(); - if ((TrueBBI.hasEarlyExit && TrueNumPreds <= 1) && - !(FalseBBI.hasEarlyExit && FalseNumPreds <=1)) { - BBI.Kind = ICEarlyExit; - TrueBBI.Kind = ICChild; - } else if (!(TrueBBI.hasEarlyExit && TrueNumPreds <= 1) && - (FalseBBI.hasEarlyExit && FalseNumPreds <=1)) { - BBI.Kind = ICEarlyExitFalse; - FalseBBI.Kind = ICChild; - } else if (TrueBBI.TrueBB && TrueBBI.TrueBB == BBI.FalseBB) { - // Triangle: - // EBB - // | \_ - // | | - // | TBB - // | / - // FBB - BBI.Kind = ICTriangle; - TrueBBI.Kind = FalseBBI.Kind = ICChild; - } else if (TrueBBI.TrueBB == FalseBBI.TrueBB && - TrueNumPreds <= 1 && FalseNumPreds <= 1) { + + // Look for more opportunities to if-convert a triangle. Try to restructure + // the CFG to form a triangle with the 'false' path. + std::vector<MachineOperand> RevCond(BBI.BrCond); + bool CanRevCond = !TII->ReverseBranchCondition(RevCond); + if (FalseBBI.FalseBB) { + if (TrueBBI.TrueBB && TrueBBI.TrueBB == BBI.FalseBB) + return; + std::vector<MachineOperand> Cond(BBI.BrCond); + if (CanRevCond && + FalseBBI.TrueBB && FalseBBI.BB->pred_size() == 1 && + FeasibilityAnalysis(FalseBBI, RevCond, true)) { + std::vector<MachineOperand> 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 && + TrueBBI.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 // / \_ @@ -266,6 +299,44 @@ void IfConverter::StructuralAnalysis(MachineBasicBlock *BB) { 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<MachineOperand> 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; } @@ -274,25 +345,37 @@ void IfConverter::StructuralAnalysis(MachineBasicBlock *BB) { /// 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. Note, this function assumes -/// all the terminator instructions can be converted or deleted so it ignore -/// them. -void IfConverter::FeasibilityAnalysis(BBInfo &BBI, - std::vector<MachineOperand> &Cond) { +/// 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<MachineOperand> &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; + 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; + return false; } - if (BBI.Predicate.size() && !TII->SubsumesPredicate(BBI.Predicate, Cond)) - return; - - BBI.isPredicable = true; + return true; } /// AttemptRestructuring - Restructure the sub-CFG rooted in the given block to @@ -336,8 +419,8 @@ bool IfConverter::AnalyzeBlocks(MachineFunction &MF, StructuralAnalysis(BB); BBInfo &BBI = BBAnalysis[BB->getNumber()]; switch (BBI.Kind) { - case ICEarlyExit: - case ICEarlyExitFalse: + case ICSimple: + case ICSimpleFalse: case ICTriangle: case ICDiamond: Candidates.push_back(&BBI); @@ -355,37 +438,14 @@ bool IfConverter::AnalyzeBlocks(MachineFunction &MF, return Change; } -/// 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); - } -} - -/// TransferSuccs - Transfer all the successors of FromBB 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); - } -} - -/// isNextBlock - Returns true if ToBB the next basic block after BB. -/// +/// 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 Fallthrough = BB; - return MachineFunction::iterator(ToBB) == ++Fallthrough; + MachineFunction::iterator I = BB; + while (++I != MachineFunction::iterator(ToBB)) + if (!I->empty()) + return false; + return true; } /// ReTryPreds - Invalidate predecessor BB info so it would be re-analyzed @@ -406,10 +466,10 @@ static void InsertUncondBranch(MachineBasicBlock *BB, MachineBasicBlock *ToBB, TII->InsertBranch(*BB, ToBB, NULL, NoCond); } -/// IfConvertEarlyExit - If convert a early exit sub-CFG. +/// IfConvertSimple - If convert a simple (split, no rejoin) sub-CFG. /// -bool IfConverter::IfConvertEarlyExit(BBInfo &BBI) { - bool ReverseCond = BBI.Kind == ICEarlyExitFalse; +bool IfConverter::IfConvertSimple(BBInfo &BBI) { + bool ReverseCond = BBI.Kind == ICSimpleFalse; BBI.Kind = ICNotClassfied; @@ -418,25 +478,29 @@ bool IfConverter::IfConvertEarlyExit(BBInfo &BBI) { BBInfo *CvtBBI = &TrueBBI; BBInfo *NextBBI = &FalseBBI; - std::vector<MachineOperand> NewCond(BBI.BrCond); + std::vector<MachineOperand> Cond(BBI.BrCond); if (ReverseCond) { std::swap(CvtBBI, NextBBI); - TII->ReverseBranchCondition(NewCond); + TII->ReverseBranchCondition(Cond); } - FeasibilityAnalysis(*CvtBBI, NewCond); - if (!CvtBBI->isPredicable) - return false; - PredicateBlock(*CvtBBI, NewCond); + 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 convert the end of the - // block conditional branch (to the non-converted block) into an - // unconditional one. + // 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(NewCond.begin(), NewCond.end(), std::back_inserter(BBI.Predicate)); + std::copy(Cond.begin(), Cond.end(), std::back_inserter(BBI.Predicate)); // Update block info. BB can be iteratively if-converted. BBI.Kind = ICNotAnalyzed; @@ -447,7 +511,6 @@ bool IfConverter::IfConvertEarlyExit(BBInfo &BBI) { CvtBBI->Kind = ICDead; // FIXME: Must maintain LiveIns. - NumIfConvBBs++; return true; } @@ -457,19 +520,12 @@ bool IfConverter::IfConvertTriangle(BBInfo &BBI) { BBI.Kind = ICNotClassfied; BBInfo &TrueBBI = BBAnalysis[BBI.TrueBB->getNumber()]; - FeasibilityAnalysis(TrueBBI, BBI.BrCond); - if (!TrueBBI.isPredicable) - return false; - - // FIXME: Consider duplicating if BB is small. - if (BBI.TrueBB->pred_size() > 1) - return false; // 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 a early exit branch to it. + // If 'true' block has a 'false' successor, add an exit branch to it. if (TrueBBI.FalseBB) { std::vector<MachineOperand> RevCond(TrueBBI.BrCond); if (TII->ReverseBranchCondition(RevCond)) @@ -482,7 +538,7 @@ bool IfConverter::IfConvertTriangle(BBInfo &BBI) { BBInfo &FalseBBI = BBAnalysis[BBI.FalseBB->getNumber()]; if (FalseBBI.BB->pred_size() == 2) MergeBlocks(TrueBBI, FalseBBI); - else + else if (!isNextBlock(TrueBBI.BB, FalseBBI.BB)) InsertUncondBranch(TrueBBI.BB, FalseBBI.BB, TII); // Now merge the entry of the triangle with the true block. @@ -500,7 +556,6 @@ bool IfConverter::IfConvertTriangle(BBInfo &BBI) { TrueBBI.Kind = ICDead; // FIXME: Must maintain LiveIns. - NumIfConvBBs++; return true; } @@ -509,87 +564,66 @@ bool IfConverter::IfConvertTriangle(BBInfo &BBI) { bool IfConverter::IfConvertDiamond(BBInfo &BBI) { BBI.Kind = ICNotClassfied; - bool TrueNeedBr; - bool FalseNeedBr; - BBInfo &TrueBBI = BBAnalysis[BBI.TrueBB->getNumber()]; + BBInfo &TrueBBI = BBAnalysis[BBI.TrueBB->getNumber()]; BBInfo &FalseBBI = BBAnalysis[BBI.FalseBB->getNumber()]; - FeasibilityAnalysis(TrueBBI, BBI.BrCond); - std::vector<MachineOperand> RevCond(BBI.BrCond); - TII->ReverseBranchCondition(RevCond); - FeasibilityAnalysis(FalseBBI, RevCond); SmallVector<MachineInstr*, 2> Dups; - bool Proceed = TrueBBI.isPredicable && FalseBBI.isPredicable; - if (Proceed) { - // 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. - TrueNeedBr = !TrueBBI.TrueBB && BBI.TrueBB->succ_size(); - FalseNeedBr = !FalseBBI.TrueBB && BBI.FalseBB->succ_size(); - if (TrueNeedBr && TrueBBI.ModifyPredicate) { - TrueBBI.isPredicable = false; - Proceed = false; - } - if (FalseNeedBr && FalseBBI.ModifyPredicate) { - FalseBBI.isPredicable = false; - Proceed = false; + 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; } - if (Proceed) { - 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()) { - Proceed = false; - break; // Can't if-convert. Abort! - } - ++TT; - ++FT; - } - - // One of the two pathes have more terminators, make sure they are - // all predicable. - while (Proceed && TT != BBI.TrueBB->end()) - if (!TT->isPredicable()) { - Proceed = false; - break; // Can't if-convert. Abort! - } - while (Proceed && FT != BBI.FalseBB->end()) - if (!FT->isPredicable()) { - Proceed = false; - break; // Can't if-convert. Abort! - } + // 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; } } - if (!Proceed) - return false; - // Remove the duplicated instructions from the 'true' block. for (unsigned i = 0, e = Dups.size(); i != e; ++i) { Dups[i]->eraseFromParent(); --TrueBBI.NonPredSize; } - // Predicate the 'true' block after removing its branch. - TrueBBI.NonPredSize -= TII->RemoveBranch(*BBI.TrueBB); - PredicateBlock(TrueBBI, BBI.BrCond); - - // Predicate the 'false' block. - PredicateBlock(FalseBBI, RevCond, true); + // 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 TrueNeedBr = !TrueBBI.TrueBB && BBI.TrueBB->succ_size(); + bool FalseNeedBr = !FalseBBI.TrueBB && BBI.FalseBB->succ_size(); // 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. + std::vector<MachineOperand> RevCond(BBI.BrCond); + TII->ReverseBranchCondition(RevCond); BBInfo *CvtBBI; if (!TrueBBI.ModifyPredicate) { - // Add a conditional branch from 'true' to 'true' successor if needed. + // Predicate the 'true' block after removing its branch. + TrueBBI.NonPredSize -= TII->RemoveBranch(*BBI.TrueBB); + PredicateBlock(TrueBBI, BBI.BrCond); + + // Predicate the 'false' block. + PredicateBlock(FalseBBI, RevCond, true); + if (TrueNeedBr) TII->InsertBranch(*BBI.TrueBB, *BBI.TrueBB->succ_begin(), NULL, BBI.BrCond); @@ -601,6 +635,13 @@ bool IfConverter::IfConvertDiamond(BBInfo &BBI) { MergeBlocks(TrueBBI, FalseBBI); CvtBBI = &TrueBBI; } else { + // Predicate the 'false' block after removing its branch. + FalseBBI.NonPredSize -= TII->RemoveBranch(*BBI.FalseBB); + PredicateBlock(FalseBBI, RevCond); + + // Predicate the 'false' block. + PredicateBlock(TrueBBI, BBI.BrCond, true); + // Add a conditional branch from 'false' to 'false' successor if needed. if (FalseNeedBr) TII->InsertBranch(*BBI.FalseBB, *BBI.FalseBB->succ_begin(), NULL, @@ -625,7 +666,7 @@ bool IfConverter::IfConvertDiamond(BBInfo &BBI) { MergeBlocks(BBI, *CvtBBI); CvtBBI = &BBI; OkToIfcvt = false; - } else + } else if (!isNextBlock(BBI.BB, CvtBBI->BB)) InsertUncondBranch(BBI.BB, CvtBBI->BB, TII); // If the if-converted block fallthrough or unconditionally branch into the @@ -651,7 +692,6 @@ bool IfConverter::IfConvertDiamond(BBInfo &BBI) { FalseBBI.Kind = ICDead; // FIXME: Must maintain LiveIns. - NumIfConvBBs += 2; return true; } @@ -662,18 +702,41 @@ void IfConverter::PredicateBlock(BBInfo &BBI, bool IgnoreTerm) { for (MachineBasicBlock::iterator I = BBI.BB->begin(), E = BBI.BB->end(); I != E; ++I) { - MachineInstr *MI = I; - if (IgnoreTerm && TII->isTerminatorInstr(MI->getOpcode())) + if (IgnoreTerm && TII->isTerminatorInstr(I->getOpcode())) continue; - if (TII->isPredicated(MI)) + if (TII->isPredicated(I)) continue; - if (!TII->PredicateInstruction(MI, Cond)) { + 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) { + FromBB->removeSuccessor(*I); + if (!ToBB->isSuccessor(*I)) + ToBB->addSuccessor(*I); + } } /// MergeBlocks - Move all instructions from FromBB to the end of ToBB. @@ -687,6 +750,11 @@ void IfConverter::MergeBlocks(BBInfo &ToBBI, BBInfo &FromBBI) { if (ToBBI.BB->isSuccessor(FromBBI.BB)) ToBBI.BB->removeSuccessor(FromBBI.BB); + // Redirect all branches to FromBB to ToBB. + for (MachineBasicBlock::pred_iterator I = FromBBI.BB->pred_begin(), + E = FromBBI.BB->pred_end(); I != E; ++I) + (*I)->ReplaceUsesOfBlockWith(FromBBI.BB, ToBBI.BB); + // Transfer preds / succs and update size. TransferPreds(ToBBI.BB, FromBBI.BB); TransferSuccs(ToBBI.BB, FromBBI.BB); |