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LLVM
4.0.0
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#include "BranchFolding.h"#include "llvm/ADT/STLExtras.h"#include "llvm/ADT/SmallSet.h"#include "llvm/ADT/Statistic.h"#include "llvm/CodeGen/Analysis.h"#include "llvm/CodeGen/MachineBlockFrequencyInfo.h"#include "llvm/CodeGen/MachineBranchProbabilityInfo.h"#include "llvm/CodeGen/MachineFunctionPass.h"#include "llvm/CodeGen/MachineJumpTableInfo.h"#include "llvm/CodeGen/MachineMemOperand.h"#include "llvm/CodeGen/MachineLoopInfo.h"#include "llvm/CodeGen/MachineModuleInfo.h"#include "llvm/CodeGen/MachineRegisterInfo.h"#include "llvm/CodeGen/Passes.h"#include "llvm/CodeGen/TargetPassConfig.h"#include "llvm/IR/Function.h"#include "llvm/Support/CommandLine.h"#include "llvm/Support/Debug.h"#include "llvm/Support/ErrorHandling.h"#include "llvm/Support/raw_ostream.h"#include "llvm/Target/TargetInstrInfo.h"#include "llvm/Target/TargetRegisterInfo.h"#include "llvm/Target/TargetSubtargetInfo.h"#include <algorithm>Go to the source code of this file.
Macros | |
| #define | DEBUG_TYPE "branchfolding" |
Functions | |
| STATISTIC (NumDeadBlocks,"Number of dead blocks removed") | |
| STATISTIC (NumBranchOpts,"Number of branches optimized") | |
| STATISTIC (NumTailMerge,"Number of block tails merged") | |
| STATISTIC (NumHoist,"Number of times common instructions are hoisted") | |
| INITIALIZE_PASS (BranchFolderPass,"branch-folder","Control Flow Optimizer", false, false) bool BranchFolderPass | |
| static unsigned | HashMachineInstr (const MachineInstr &MI) |
| HashMachineInstr - Compute a hash value for MI and its operands. More... | |
| static unsigned | HashEndOfMBB (const MachineBasicBlock &MBB) |
| HashEndOfMBB - Hash the last instruction in the MBB. More... | |
| static unsigned | ComputeCommonTailLength (MachineBasicBlock *MBB1, MachineBasicBlock *MBB2, MachineBasicBlock::iterator &I1, MachineBasicBlock::iterator &I2) |
| ComputeCommonTailLength - Given two machine basic blocks, compute the number of instructions they actually have in common together at their end. More... | |
| static unsigned | EstimateRuntime (MachineBasicBlock::iterator I, MachineBasicBlock::iterator E) |
| EstimateRuntime - Make a rough estimate for how long it will take to run the specified code. More... | |
| static void | FixTail (MachineBasicBlock *CurMBB, MachineBasicBlock *SuccBB, const TargetInstrInfo *TII) |
| static unsigned | CountTerminators (MachineBasicBlock *MBB, MachineBasicBlock::iterator &I) |
| CountTerminators - Count the number of terminators in the given block and set I to the position of the first non-terminator, if there is one, or MBB->end() otherwise. More... | |
| static bool | ProfitableToMerge (MachineBasicBlock *MBB1, MachineBasicBlock *MBB2, unsigned MinCommonTailLength, unsigned &CommonTailLen, MachineBasicBlock::iterator &I1, MachineBasicBlock::iterator &I2, MachineBasicBlock *SuccBB, MachineBasicBlock *PredBB, DenseMap< const MachineBasicBlock *, int > &FuncletMembership, bool AfterPlacement) |
| ProfitableToMerge - Check if two machine basic blocks have a common tail and decide if it would be profitable to merge those tails. More... | |
| static void | mergeOperations (MachineBasicBlock::iterator MBBIStartPos, MachineBasicBlock &MBBCommon) |
| static bool | IsEmptyBlock (MachineBasicBlock *MBB) |
| static bool | IsBranchOnlyBlock (MachineBasicBlock *MBB) |
| static bool | IsBetterFallthrough (MachineBasicBlock *MBB1, MachineBasicBlock *MBB2) |
| IsBetterFallthrough - Return true if it would be clearly better to fall-through to MBB1 than to fall through into MBB2. More... | |
| static DebugLoc | getBranchDebugLoc (MachineBasicBlock &MBB) |
| getBranchDebugLoc - Find and return, if any, the DebugLoc of the branch instructions on the block. More... | |
| static MachineBasicBlock * | findFalseBlock (MachineBasicBlock *BB, MachineBasicBlock *TrueBB) |
| findFalseBlock - BB has a fallthrough. More... | |
| template<class Container > | |
| static void | addRegAndItsAliases (unsigned Reg, const TargetRegisterInfo *TRI, Container &Set) |
| static MachineBasicBlock::iterator | findHoistingInsertPosAndDeps (MachineBasicBlock *MBB, const TargetInstrInfo *TII, const TargetRegisterInfo *TRI, SmallSet< unsigned, 4 > &Uses, SmallSet< unsigned, 4 > &Defs) |
| findHoistingInsertPosAndDeps - Find the location to move common instructions in successors to. More... | |
Variables | |
| static cl::opt< cl::boolOrDefault > | FlagEnableTailMerge ("enable-tail-merge", cl::init(cl::BOU_UNSET), cl::Hidden) |
| static cl::opt< unsigned > | TailMergeThreshold ("tail-merge-threshold", cl::desc("Max number of predecessors to consider tail merging"), cl::init(150), cl::Hidden) |
| static cl::opt< unsigned > | TailMergeSize ("tail-merge-size", cl::desc("Min number of instructions to consider tail merging"), cl::init(3), cl::Hidden) |
| #define DEBUG_TYPE "branchfolding" |
Definition at line 46 of file BranchFolding.cpp.
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Definition at line 1625 of file BranchFolding.cpp.
References llvm::TargetRegisterInfo::isPhysicalRegister(), and llvm::MCRegAliasIterator::isValid().
Referenced by findHoistingInsertPosAndDeps().
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ComputeCommonTailLength - Given two machine basic blocks, compute the number of instructions they actually have in common together at their end.
Return iterators for the first shared instruction in each block.
Definition at line 279 of file BranchFolding.cpp.
References llvm::MachineBasicBlock::begin(), and llvm::MachineBasicBlock::end().
Referenced by ProfitableToMerge().
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CountTerminators - Count the number of terminators in the given block and set I to the position of the first non-terminator, if there is one, or MBB->end() otherwise.
Definition at line 503 of file BranchFolding.cpp.
References llvm::MachineBasicBlock::begin(), llvm::MachineBasicBlock::end(), and I.
Referenced by ProfitableToMerge().
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EstimateRuntime - Make a rough estimate for how long it will take to run the specified code.
Definition at line 413 of file BranchFolding.cpp.
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findFalseBlock - BB has a fallthrough.
Find its 'false' successor given its 'true' successor.
Definition at line 1616 of file BranchFolding.cpp.
References llvm::MachineBasicBlock::successors().
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findHoistingInsertPosAndDeps - Find the location to move common instructions in successors to.
The location is usually just before the terminator, however if the terminator is a conditional branch and its previous instruction is the flag setting instruction, the previous instruction is the preferred location. This function also gathers uses and defs of the instructions from the insertion point to the end of the block. The data is used by HoistCommonCodeInSuccs to ensure safety.
Definition at line 1643 of file BranchFolding.cpp.
References addRegAndItsAliases(), llvm::MachineBasicBlock::begin(), llvm::SmallSet< T, N, C >::count(), llvm::SmallSet< T, N, C >::empty(), llvm::MachineBasicBlock::end(), llvm::SmallSet< T, N, C >::erase(), llvm::MachineBasicBlock::getFirstTerminator(), llvm::TargetRegisterInfo::isPhysicalRegister(), llvm::TargetInstrInfo::isPredicated(), llvm::TargetInstrInfo::isUnpredicatedTerminator(), llvm::MCRegisterInfo::DiffListIterator::isValid(), and llvm::skipDebugInstructionsBackward().
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Definition at line 433 of file BranchFolding.cpp.
References llvm::TargetInstrInfo::analyzeBranch(), llvm::SmallVectorBase::empty(), llvm::MachineFunction::end(), llvm::MachineBasicBlock::getParent(), I, llvm::TargetInstrInfo::insertBranch(), llvm::TargetInstrInfo::removeBranch(), and llvm::TargetInstrInfo::reverseBranchCondition().
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getBranchDebugLoc - Find and return, if any, the DebugLoc of the branch instructions on the block.
Definition at line 1189 of file BranchFolding.cpp.
References llvm::MachineBasicBlock::end(), llvm::MachineBasicBlock::getLastNonDebugInstr(), and I.
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HashEndOfMBB - Hash the last instruction in the MBB.
Definition at line 268 of file BranchFolding.cpp.
References llvm::MachineBasicBlock::end(), llvm::MachineBasicBlock::getLastNonDebugInstr(), HashMachineInstr(), and I.
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HashMachineInstr - Compute a hash value for MI and its operands.
Definition at line 228 of file BranchFolding.cpp.
References llvm::MachineOperand::getImm(), llvm::MachineOperand::getIndex(), llvm::MachineOperand::getMBB(), llvm::MachineBasicBlock::getNumber(), llvm::MachineInstr::getNumOperands(), llvm::MachineOperand::getOffset(), llvm::MachineInstr::getOpcode(), llvm::MachineInstr::getOperand(), llvm::MachineOperand::getReg(), llvm::MachineOperand::getType(), fuzzer::Hash(), i, llvm::MachineOperand::MO_ConstantPoolIndex, llvm::MachineOperand::MO_ExternalSymbol, llvm::MachineOperand::MO_FrameIndex, llvm::MachineOperand::MO_GlobalAddress, llvm::MachineOperand::MO_Immediate, llvm::MachineOperand::MO_JumpTableIndex, llvm::MachineOperand::MO_MachineBasicBlock, and llvm::MachineOperand::MO_Register.
Referenced by HashEndOfMBB().
Definition at line 90 of file BranchFolding.cpp.
References llvm::TargetPassConfig::getEnableTailMerge(), and llvm::BranchFolder::OptimizeFunction().
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IsBetterFallthrough - Return true if it would be clearly better to fall-through to MBB1 than to fall through into MBB2.
This has to return a strict ordering, returning true for both (MBB1,MBB2) and (MBB2,MBB1) will result in infinite loops.
Definition at line 1168 of file BranchFolding.cpp.
References llvm::MachineBasicBlock::end(), llvm::MachineBasicBlock::getLastNonDebugInstr(), and llvm::MachineBasicBlock::isSuccessor().
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Definition at line 1158 of file BranchFolding.cpp.
References assert(), llvm::MachineBasicBlock::end(), llvm::MachineBasicBlock::getFirstNonDebugInstr(), and I.
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Definition at line 1152 of file BranchFolding.cpp.
References llvm::MachineBasicBlock::end(), and llvm::MachineBasicBlock::getFirstNonDebugInstr().
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Definition at line 727 of file BranchFolding.cpp.
References assert(), E, llvm::MachineBasicBlock::end(), I, llvm::MachineOperand::isReg(), llvm::MachineOperand::isUndef(), llvm::MachineBasicBlock::rbegin(), llvm::MachineBasicBlock::rend(), and llvm::MachineOperand::setIsUndef().
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ProfitableToMerge - Check if two machine basic blocks have a common tail and decide if it would be profitable to merge those tails.
Return the length of the common tail and iterators to the first common instruction in each block. MBB1, MBB2 The blocks to check MinCommonTailLength Minimum size of tail block to be merged. CommonTailLen Out parameter to record the size of the shared tail between MBB1 and MBB2 I1, I2 Iterator references that will be changed to point to the first instruction in the common tail shared by MBB1,MBB2 SuccBB A common successor of MBB1, MBB2 which are in a canonical form relative to SuccBB PredBB The layout predecessor of SuccBB, if any. FuncletMembership map from block to funclet #. AfterPlacement True if we are merging blocks after layout. Stricter thresholds apply to prevent undoing tail-duplication.
Definition at line 536 of file BranchFolding.cpp.
References assert(), llvm::MachineBasicBlock::back(), llvm::MachineBasicBlock::begin(), ComputeCommonTailLength(), CountTerminators(), llvm::dbgs(), DEBUG, llvm::DenseMapBase< DenseMap< KeyT, ValueT, KeyInfoT, BucketT >, KeyT, ValueT, KeyInfoT, BucketT >::empty(), llvm::DenseMapBase< DenseMap< KeyT, ValueT, KeyInfoT, BucketT >, KeyT, ValueT, KeyInfoT, BucketT >::end(), llvm::DenseMapBase< DenseMap< KeyT, ValueT, KeyInfoT, BucketT >, KeyT, ValueT, KeyInfoT, BucketT >::find(), llvm::MachineFunction::getFunction(), llvm::MachineBasicBlock::getNumber(), llvm::MachineBasicBlock::getParent(), I, llvm::MachineInstr::isBarrier(), llvm::MachineBasicBlock::isLayoutSuccessor(), llvm::Function::optForSize(), and llvm::MachineBasicBlock::succ_size().
| STATISTIC | ( | NumDeadBlocks | , |
| "Number of dead blocks removed" | |||
| ) |
| STATISTIC | ( | NumBranchOpts | , |
| "Number of branches optimized" | |||
| ) |
| STATISTIC | ( | NumTailMerge | , |
| "Number of block tails merged" | |||
| ) |
| STATISTIC | ( | NumHoist | , |
| "Number of times common instructions are hoisted" | |||
| ) |
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Referenced by llvm::BranchFolder::BranchFolder().
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Referenced by llvm::BranchFolder::BranchFolder().
1.8.6