From 0f745da4fec9665dfdd36fa1d35257bd1390a075 Mon Sep 17 00:00:00 2001 From: Evan Cheng Date: Fri, 18 May 2007 00:20:58 +0000 Subject: [PATCH] Make use of target specific block size limits; bug fixes. llvm-svn: 37195 --- llvm/lib/CodeGen/IfConversion.cpp | 211 +++++++++++++++++++++--------- 1 file changed, 148 insertions(+), 63 deletions(-) diff --git a/llvm/lib/CodeGen/IfConversion.cpp b/llvm/lib/CodeGen/IfConversion.cpp index 37c729d341cd..9b69bf16f8c8 100644 --- a/llvm/lib/CodeGen/IfConversion.cpp +++ b/llvm/lib/CodeGen/IfConversion.cpp @@ -16,6 +16,7 @@ #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/Statistic.h" @@ -37,22 +38,24 @@ namespace { /// 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 merge block of its successors (if it's a + /// classification, and common tail block of its successors (if it's a /// diamond shape). struct BBInfo { BBICKind Kind; - MachineBasicBlock *EBB; - MachineBasicBlock *TBB; - MachineBasicBlock *FBB; - MachineBasicBlock *CMBB; + MachineBasicBlock *BB; + MachineBasicBlock *TrueBB; + MachineBasicBlock *FalseBB; + MachineBasicBlock *TailBB; std::vector Cond; - BBInfo() : Kind(ICInvalid), EBB(0), TBB(0), FBB(0), CMBB(0) {} + unsigned Size; + BBInfo() : Kind(ICInvalid), BB(0), TrueBB(0), FalseBB(0), TailBB(0), Size(0) {} }; /// BBAnalysis - Results of if-conversion feasibility analysis indexed by /// basic block number. std::vector BBAnalysis; + const TargetLowering *TLI; const TargetInstrInfo *TII; bool MadeChange; public: @@ -72,7 +75,7 @@ namespace { void PredicateBlock(MachineBasicBlock *BB, std::vector &Cond, bool IgnoreTerm = false); - void MergeBlocks(MachineBasicBlock *TBB, MachineBasicBlock *FBB); + void MergeBlocks(BBInfo &TrueBBI, BBInfo &FalseBBI); }; char IfConverter::ID = 0; } @@ -80,6 +83,7 @@ namespace { FunctionPass *llvm::createIfConverterPass() { return new IfConverter(); } bool IfConverter::runOnMachineFunction(MachineFunction &MF) { + TLI = MF.getTarget().getTargetLowering(); TII = MF.getTarget().getInstrInfo(); if (!TII) return false; @@ -95,7 +99,7 @@ bool IfConverter::runOnMachineFunction(MachineFunction &MF) { InitialFunctionAnalysis(MF, Candidates); for (unsigned i = 0, e = Candidates.size(); i != e; ++i) { - BBInfo &BBI = BBAnalysis[i]; + BBInfo &BBI = BBAnalysis[Candidates[i]]; switch (BBI.Kind) { default: assert(false && "Unexpected!"); break; @@ -111,11 +115,11 @@ bool IfConverter::runOnMachineFunction(MachineFunction &MF) { } static MachineBasicBlock *findFalseBlock(MachineBasicBlock *BB, - MachineBasicBlock *TBB) { + MachineBasicBlock *TrueBB) { for (MachineBasicBlock::succ_iterator SI = BB->succ_begin(), E = BB->succ_end(); SI != E; ++SI) { MachineBasicBlock *SuccBB = *SI; - if (SuccBB != TBB) + if (SuccBB != TrueBB) return SuccBB; } return NULL; @@ -126,36 +130,49 @@ void IfConverter::AnalyzeBlock(MachineBasicBlock *BB) { if (BBI.Kind != ICInvalid) return; // Always analyzed. - BBI.EBB = BB; + BBI.BB = BB; + BBI.Size = std::distance(BB->begin(), BB->end()); // Look for 'root' of a simple (non-nested) triangle or diamond. BBI.Kind = ICNotClassfied; - if (TII->AnalyzeBranch(*BB, BBI.TBB, BBI.FBB, BBI.Cond) - || !BBI.TBB || BBI.Cond.size() == 0) + if (TII->AnalyzeBranch(*BB, BBI.TrueBB, BBI.FalseBB, BBI.Cond) + || !BBI.TrueBB || BBI.Cond.size() == 0) return; - // Can't do it if 'true' block is already marked as to be if-converted. - AnalyzeBlock(BBI.TBB); - BBInfo &TBBI = BBAnalysis[BBI.TBB->getNumber()]; - if (TBBI.Kind != ICNotClassfied) + + // Not a candidate if 'true' block has another predecessor. + // FIXME: Use or'd predicate or predicated cmp. + if (BBI.TrueBB->pred_size() > 1) + return; + + // Not a candidate if 'true' block is going to be if-converted. + AnalyzeBlock(BBI.TrueBB); + BBInfo &TrueBBI = BBAnalysis[BBI.TrueBB->getNumber()]; + if (TrueBBI.Kind != ICNotClassfied) return; // No false branch. This BB must end with a conditional branch and a // fallthrough. - if (!BBI.FBB) - BBI.FBB = findFalseBlock(BB, BBI.TBB); - assert(BBI.FBB && "Expected to find the fallthrough block!"); + if (!BBI.FalseBB) + BBI.FalseBB = findFalseBlock(BB, BBI.TrueBB); + assert(BBI.FalseBB && "Expected to find the fallthrough block!"); - // Can't do it if 'false' block is already marked as to be if-converted. - AnalyzeBlock(BBI.FBB); - BBInfo &FBBI = BBAnalysis[BBI.FBB->getNumber()]; - if (FBBI.Kind != ICNotClassfied) + // Not a candidate if 'false' block has another predecessor. + // FIXME: Invert condition and swap 'true' / 'false' blocks? + if (BBI.FalseBB->pred_size() > 1) + return; + + // Not a candidate if 'false' block is going to be if-converted. + AnalyzeBlock(BBI.FalseBB); + BBInfo &FalseBBI = BBAnalysis[BBI.FalseBB->getNumber()]; + if (FalseBBI.Kind != ICNotClassfied) return; // TODO: Only handle very simple cases for now. - if (TBBI.FBB || FBBI.FBB || TBBI.Cond.size() > 1 || FBBI.Cond.size() > 1) + if (TrueBBI.FalseBB || FalseBBI.FalseBB || + TrueBBI.Cond.size() || FalseBBI.Cond.size()) return; - if (TBBI.TBB && TBBI.TBB == BBI.FBB) { + if (TrueBBI.TrueBB && TrueBBI.TrueBB == BBI.FalseBB) { // Triangle: // EBB // | \_ @@ -164,19 +181,19 @@ void IfConverter::AnalyzeBlock(MachineBasicBlock *BB) { // | / // FBB BBI.Kind = ICTriangleEntry; - TBBI.Kind = FBBI.Kind = ICTriangle; - } else if (TBBI.TBB == FBBI.TBB) { + TrueBBI.Kind = FalseBBI.Kind = ICTriangle; + } else if (TrueBBI.TrueBB == FalseBBI.TrueBB) { // Diamond: // EBB // / \_ // | | // TBB FBB // \ / - // MBB + // TailBB // Note MBB can be empty in case both TBB and FBB are return blocks. BBI.Kind = ICDiamondEntry; - TBBI.Kind = FBBI.Kind = ICDiamond; - BBI.CMBB = TBBI.TBB; + TrueBBI.Kind = FalseBBI.Kind = ICDiamond; + BBI.TailBB = TrueBBI.TrueBB; } return; } @@ -194,24 +211,55 @@ void IfConverter::InitialFunctionAnalysis(MachineFunction &MF, } } +/// TransferPreds - Transfer all the predecessors of FromBB to ToBB. +/// +static void TransferPreds(MachineBasicBlock *ToBB, MachineBasicBlock *FromBB) { + std::vector 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 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); + } +} + /// IfConvertTriangle - If convert a triangle sub-CFG. /// bool IfConverter::IfConvertTriangle(BBInfo &BBI) { - if (isBlockPredicable(BBI.TBB)) { + if (isBlockPredicable(BBI.TrueBB)) { + BBInfo &TrueBBI = BBAnalysis[BBI.TrueBB->getNumber()]; + BBInfo &FalseBBI = BBAnalysis[BBI.FalseBB->getNumber()]; + // Predicate the 'true' block after removing its branch. - TII->RemoveBranch(*BBI.TBB); - PredicateBlock(BBI.TBB, BBI.Cond); + TrueBBI.Size -= TII->RemoveBranch(*BBI.TrueBB); + PredicateBlock(BBI.TrueBB, BBI.Cond); // Join the 'true' and 'false' blocks by copying the instructions // from the 'false' block to the 'true' block. - MergeBlocks(BBI.TBB, BBI.FBB); + BBI.TrueBB->removeSuccessor(BBI.FalseBB); + MergeBlocks(TrueBBI, FalseBBI); - // Adjust entry block, it should have but a single unconditional - // branch. - BBI.EBB->removeSuccessor(BBI.FBB); - TII->RemoveBranch(*BBI.EBB); - std::vector NoCond; - TII->InsertBranch(*BBI.EBB, BBI.TBB, NULL, NoCond); + // Now merge the entry of the triangle with the true block. + BBI.Size -= TII->RemoveBranch(*BBI.BB); + MergeBlocks(BBI, TrueBBI); + + // Update block info. + TrueBBI.Kind = ICInvalid; + FalseBBI.Kind = ICInvalid; // FIXME: Must maintain LiveIns. NumIfConvBBs++; @@ -223,14 +271,14 @@ bool IfConverter::IfConvertTriangle(BBInfo &BBI) { /// IfConvertDiamond - If convert a diamond sub-CFG. /// bool IfConverter::IfConvertDiamond(BBInfo &BBI) { - if (isBlockPredicable(BBI.TBB) && isBlockPredicable(BBI.FBB)) { + if (isBlockPredicable(BBI.TrueBB) && isBlockPredicable(BBI.FalseBB)) { std::vector Dups; - if (!BBI.CMBB) { + if (!BBI.TailBB) { // No common merge block. Check if the terminators (e.g. return) are // the same or predicable. - MachineBasicBlock::iterator TT = BBI.TBB->getFirstTerminator(); - MachineBasicBlock::iterator FT = BBI.FBB->getFirstTerminator(); - while (TT != BBI.TBB->end() && FT != BBI.FBB->end()) { + 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()) @@ -240,37 +288,65 @@ bool IfConverter::IfConvertDiamond(BBInfo &BBI) { } // One of the two pathes have more terminators, make sure they are all // predicable. - while (TT != BBI.TBB->end()) + while (TT != BBI.TrueBB->end()) if (!TT->isPredicable()) return false; // Can't if-convert. Abort! - while (FT != BBI.FBB->end()) + while (FT != BBI.FalseBB->end()) if (!FT->isPredicable()) return false; // Can't if-convert. Abort! } + BBInfo &TrueBBI = BBAnalysis[BBI.TrueBB->getNumber()]; + BBInfo &FalseBBI = BBAnalysis[BBI.FalseBB->getNumber()]; + // Remove the duplicated instructions from the 'true' block. - for (unsigned i = 0, e = Dups.size(); i != e; ++i) + for (unsigned i = 0, e = Dups.size(); i != e; ++i) { Dups[i]->eraseFromParent(); + --TrueBBI.Size; + } // Predicate the 'true' block after removing its branch. - TII->RemoveBranch(*BBI.TBB); - PredicateBlock(BBI.TBB, BBI.Cond); + TrueBBI.Size -= TII->RemoveBranch(*BBI.TrueBB); + PredicateBlock(BBI.TrueBB, BBI.Cond); // Predicate the 'false' block. std::vector NewCond(BBI.Cond); TII->ReverseBranchCondition(NewCond); - PredicateBlock(BBI.FBB, NewCond, true); + PredicateBlock(BBI.FalseBB, NewCond, true); - // Join the 'true' and 'false' blocks by copying the instructions + // Merge the 'true' and 'false' blocks by copying the instructions // from the 'false' block to the 'true' block. - MergeBlocks(BBI.TBB, BBI.FBB); + MergeBlocks(TrueBBI, FalseBBI); - // Adjust entry block, it should have but a single unconditional - // branch . - BBI.EBB->removeSuccessor(BBI.FBB); - TII->RemoveBranch(*BBI.EBB); - std::vector NoCond; - TII->InsertBranch(*BBI.EBB, BBI.TBB, NULL, NoCond); + // Remove the conditional branch from entry to the blocks. + BBI.Size -= TII->RemoveBranch(*BBI.BB); + + // Merge the combined block into the entry of the diamond if the entry + // block is the only predecessor. Otherwise, insert an unconditional + // branch. + BBInfo *CvtBBI = &TrueBBI; + if (BBI.TrueBB->pred_size() == 1) { + BBI.BB->removeSuccessor(BBI.TrueBB); + MergeBlocks(BBI, TrueBBI); + CvtBBI = &BBI; + } else { + std::vector NoCond; + TII->InsertBranch(*BBI.BB, BBI.TrueBB, NULL, NoCond); + } + + // If the if-converted block fallthrough into the tail block, then + // fold the tail block in as well. + if (BBI.TailBB && CvtBBI->BB->succ_size() == 1) { + CvtBBI->Size -= TII->RemoveBranch(*CvtBBI->BB); + CvtBBI->BB->removeSuccessor(BBI.TailBB); + BBInfo TailBBI = BBAnalysis[BBI.TailBB->getNumber()]; + MergeBlocks(*CvtBBI, TailBBI); + TailBBI.Kind = ICInvalid; + } + + // Update block info. + TrueBBI.Kind = ICInvalid; + FalseBBI.Kind = ICInvalid; // FIXME: Must maintain LiveIns. NumIfConvBBs += 2; @@ -283,6 +359,10 @@ bool IfConverter::IfConvertDiamond(BBInfo &BBI) { /// cases, that means all the instructions in the block has M_PREDICABLE flag. /// It assume all the terminator instructions can be converted or deleted. bool IfConverter::isBlockPredicable(MachineBasicBlock *BB) const { + const BBInfo &BBI = BBAnalysis[BB->getNumber()]; + if (BBI.Size == 0 || BBI.Size > TLI->getIfCvtBlockSizeLimit()) + return false; + for (MachineBasicBlock::iterator I = BB->begin(), E = BB->end(); I != E; ++I) { if (TII->isTerminatorInstr(I->getOpcode())) @@ -309,8 +389,13 @@ void IfConverter::PredicateBlock(MachineBasicBlock *BB, } } -/// MergeBlocks - Move all instructions from FBB to the end of TBB. +/// MergeBlocks - Move all instructions from FromBB to the end of ToBB. /// -void IfConverter::MergeBlocks(MachineBasicBlock *TBB, MachineBasicBlock *FBB) { - TBB->splice(TBB->end(), FBB, FBB->begin(), FBB->end()); +void IfConverter::MergeBlocks(BBInfo &ToBBI, BBInfo &FromBBI) { + ToBBI.BB->splice(ToBBI.BB->end(), + FromBBI.BB, FromBBI.BB->begin(), FromBBI.BB->end()); + TransferPreds(ToBBI.BB, FromBBI.BB); + TransferSuccs(ToBBI.BB, FromBBI.BB); + ToBBI.Size += FromBBI.Size; + FromBBI.Size = 0; }