LLVM 20.0.0git
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The goal of hot/cold splitting is to improve the memory locality of code. More...
#include "llvm/Transforms/IPO/HotColdSplitting.h"
#include "llvm/ADT/PostOrderIterator.h"
#include "llvm/ADT/SmallVector.h"
#include "llvm/ADT/Statistic.h"
#include "llvm/Analysis/AssumptionCache.h"
#include "llvm/Analysis/BlockFrequencyInfo.h"
#include "llvm/Analysis/OptimizationRemarkEmitter.h"
#include "llvm/Analysis/PostDominators.h"
#include "llvm/Analysis/ProfileSummaryInfo.h"
#include "llvm/Analysis/TargetTransformInfo.h"
#include "llvm/IR/BasicBlock.h"
#include "llvm/IR/CFG.h"
#include "llvm/IR/DiagnosticInfo.h"
#include "llvm/IR/Dominators.h"
#include "llvm/IR/EHPersonalities.h"
#include "llvm/IR/Function.h"
#include "llvm/IR/Instruction.h"
#include "llvm/IR/Instructions.h"
#include "llvm/IR/Module.h"
#include "llvm/IR/PassManager.h"
#include "llvm/IR/ProfDataUtils.h"
#include "llvm/IR/User.h"
#include "llvm/IR/Value.h"
#include "llvm/Support/CommandLine.h"
#include "llvm/Support/Debug.h"
#include "llvm/Support/raw_ostream.h"
#include "llvm/Transforms/IPO.h"
#include "llvm/Transforms/Utils/CodeExtractor.h"
#include <algorithm>
#include <cassert>
#include <limits>
#include <string>
Go to the source code of this file.
Macros | |
#define | DEBUG_TYPE "hotcoldsplit" |
Typedefs | |
using | BlockTy = std::pair< BasicBlock *, unsigned > |
A pair of (basic block, score). | |
Functions | |
STATISTIC (NumColdRegionsFound, "Number of cold regions found.") | |
STATISTIC (NumColdRegionsOutlined, "Number of cold regions outlined.") | |
static InstructionCost | getOutliningBenefit (ArrayRef< BasicBlock * > Region, TargetTransformInfo &TTI) |
Get the benefit score of outlining Region . | |
static int | getOutliningPenalty (ArrayRef< BasicBlock * > Region, unsigned NumInputs, unsigned NumOutputs) |
Get the penalty score for outlining Region . | |
Variables | |
static cl::opt< bool > | EnableStaticAnalysis ("hot-cold-static-analysis", cl::init(true), cl::Hidden) |
static cl::opt< int > | SplittingThreshold ("hotcoldsplit-threshold", cl::init(2), cl::Hidden, cl::desc("Base penalty for splitting cold code (as a " "multiple of TCC_Basic)")) |
static cl::opt< bool > | EnableColdSection ("enable-cold-section", cl::init(false), cl::Hidden, cl::desc("Enable placement of extracted cold functions" " into a separate section after hot-cold splitting.")) |
static cl::opt< std::string > | ColdSectionName ("hotcoldsplit-cold-section-name", cl::init("__llvm_cold"), cl::Hidden, cl::desc("Name for the section containing cold functions " "extracted by hot-cold splitting.")) |
static cl::opt< int > | MaxParametersForSplit ("hotcoldsplit-max-params", cl::init(4), cl::Hidden, cl::desc("Maximum number of parameters for a split function")) |
static cl::opt< int > | ColdBranchProbDenom ("hotcoldsplit-cold-probability-denom", cl::init(100), cl::Hidden, cl::desc("Divisor of cold branch probability." "BranchProbability = 1/ColdBranchProbDenom")) |
The goal of hot/cold splitting is to improve the memory locality of code.
The splitting pass does this by identifying cold blocks and moving them into separate functions.
When the splitting pass finds a cold block (referred to as "the sink"), it grows a maximal cold region around that block. The maximal region contains all blocks (post-)dominated by the sink [*]. In theory, these blocks are as cold as the sink. Once a region is found, it's split out of the original function provided it's profitable to do so.
[*] In practice, there is some added complexity because some blocks are not safe to extract.
TODO: Use the PM to get domtrees, and preserve BFI/BPI. TODO: Reorder outlined functions.
Definition in file HotColdSplitting.cpp.
#define DEBUG_TYPE "hotcoldsplit" |
Definition at line 61 of file HotColdSplitting.cpp.
using BlockTy = std::pair<BasicBlock *, unsigned> |
A pair of (basic block, score).
Definition at line 457 of file HotColdSplitting.cpp.
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Get the benefit score of outlining Region
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Definition at line 285 of file HotColdSplitting.cpp.
References llvm::TargetTransformInfo::getInstructionCost(), llvm::BasicBlock::getTerminator(), I, llvm::BasicBlock::instructionsWithoutDebug(), and llvm::TargetTransformInfo::TCK_CodeSize.
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Get the penalty score for outlining Region
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Definition at line 300 of file HotColdSplitting.cpp.
References llvm::dbgs(), llvm::BasicBlock::getTerminator(), llvm::SmallPtrSetImpl< PtrType >::insert(), llvm::is_contained(), LLVM_DEBUG, MaxParametersForSplit, llvm::SmallPtrSetImplBase::size(), SplittingThreshold, llvm::succ_empty(), llvm::successors(), and llvm::TargetTransformInfo::TCC_Basic.
STATISTIC | ( | NumColdRegionsFound | , |
"Number of cold regions found." | |||
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STATISTIC | ( | NumColdRegionsOutlined | , |
"Number of cold regions outlined." | |||
) |
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Referenced by getOutliningPenalty().
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Referenced by getOutliningPenalty().