236 lines
9.6 KiB
C++
236 lines
9.6 KiB
C++
//===- Transform/Utils/CodeExtractor.h - Code extraction util ---*- C++ -*-===//
|
|
//
|
|
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
|
|
// See https://llvm.org/LICENSE.txt for license information.
|
|
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
|
|
//
|
|
//===----------------------------------------------------------------------===//
|
|
//
|
|
// A utility to support extracting code from one function into its own
|
|
// stand-alone function.
|
|
//
|
|
//===----------------------------------------------------------------------===//
|
|
|
|
#ifndef LLVM_TRANSFORMS_UTILS_CODEEXTRACTOR_H
|
|
#define LLVM_TRANSFORMS_UTILS_CODEEXTRACTOR_H
|
|
|
|
#include "llvm/ADT/ArrayRef.h"
|
|
#include "llvm/ADT/DenseMap.h"
|
|
#include "llvm/ADT/SetVector.h"
|
|
#include "llvm/ADT/SmallPtrSet.h"
|
|
#include <limits>
|
|
|
|
namespace llvm {
|
|
|
|
class AllocaInst;
|
|
class BasicBlock;
|
|
class BlockFrequency;
|
|
class BlockFrequencyInfo;
|
|
class BranchProbabilityInfo;
|
|
class AssumptionCache;
|
|
class CallInst;
|
|
class DominatorTree;
|
|
class Function;
|
|
class Instruction;
|
|
class Loop;
|
|
class Module;
|
|
class Type;
|
|
class Value;
|
|
|
|
/// A cache for the CodeExtractor analysis. The operation \ref
|
|
/// CodeExtractor::extractCodeRegion is guaranteed not to invalidate this
|
|
/// object. This object should conservatively be considered invalid if any
|
|
/// other mutating operations on the IR occur.
|
|
///
|
|
/// Constructing this object is O(n) in the size of the function.
|
|
class CodeExtractorAnalysisCache {
|
|
/// The allocas in the function.
|
|
SmallVector<AllocaInst *, 16> Allocas;
|
|
|
|
/// Base memory addresses of load/store instructions, grouped by block.
|
|
DenseMap<BasicBlock *, DenseSet<Value *>> BaseMemAddrs;
|
|
|
|
/// Blocks which contain instructions which may have unknown side-effects
|
|
/// on memory.
|
|
DenseSet<BasicBlock *> SideEffectingBlocks;
|
|
|
|
void findSideEffectInfoForBlock(BasicBlock &BB);
|
|
|
|
public:
|
|
CodeExtractorAnalysisCache(Function &F);
|
|
|
|
/// Get the allocas in the function at the time the analysis was created.
|
|
/// Note that some of these allocas may no longer be present in the function,
|
|
/// due to \ref CodeExtractor::extractCodeRegion.
|
|
ArrayRef<AllocaInst *> getAllocas() const { return Allocas; }
|
|
|
|
/// Check whether \p BB contains an instruction thought to load from, store
|
|
/// to, or otherwise clobber the alloca \p Addr.
|
|
bool doesBlockContainClobberOfAddr(BasicBlock &BB, AllocaInst *Addr) const;
|
|
};
|
|
|
|
/// Utility class for extracting code into a new function.
|
|
///
|
|
/// This utility provides a simple interface for extracting some sequence of
|
|
/// code into its own function, replacing it with a call to that function. It
|
|
/// also provides various methods to query about the nature and result of
|
|
/// such a transformation.
|
|
///
|
|
/// The rough algorithm used is:
|
|
/// 1) Find both the inputs and outputs for the extracted region.
|
|
/// 2) Pass the inputs as arguments, remapping them within the extracted
|
|
/// function to arguments.
|
|
/// 3) Add allocas for any scalar outputs, adding all of the outputs' allocas
|
|
/// as arguments, and inserting stores to the arguments for any scalars.
|
|
class CodeExtractor {
|
|
using ValueSet = SetVector<Value *>;
|
|
|
|
// Various bits of state computed on construction.
|
|
DominatorTree *const DT;
|
|
const bool AggregateArgs;
|
|
BlockFrequencyInfo *BFI;
|
|
BranchProbabilityInfo *BPI;
|
|
AssumptionCache *AC;
|
|
|
|
// If true, varargs functions can be extracted.
|
|
bool AllowVarArgs;
|
|
|
|
// Bits of intermediate state computed at various phases of extraction.
|
|
SetVector<BasicBlock *> Blocks;
|
|
unsigned NumExitBlocks = std::numeric_limits<unsigned>::max();
|
|
Type *RetTy;
|
|
|
|
// Suffix to use when creating extracted function (appended to the original
|
|
// function name + "."). If empty, the default is to use the entry block
|
|
// label, if non-empty, otherwise "extracted".
|
|
std::string Suffix;
|
|
|
|
public:
|
|
/// Create a code extractor for a sequence of blocks.
|
|
///
|
|
/// Given a sequence of basic blocks where the first block in the sequence
|
|
/// dominates the rest, prepare a code extractor object for pulling this
|
|
/// sequence out into its new function. When a DominatorTree is also given,
|
|
/// extra checking and transformations are enabled. If AllowVarArgs is true,
|
|
/// vararg functions can be extracted. This is safe, if all vararg handling
|
|
/// code is extracted, including vastart. If AllowAlloca is true, then
|
|
/// extraction of blocks containing alloca instructions would be possible,
|
|
/// however code extractor won't validate whether extraction is legal.
|
|
CodeExtractor(ArrayRef<BasicBlock *> BBs, DominatorTree *DT = nullptr,
|
|
bool AggregateArgs = false, BlockFrequencyInfo *BFI = nullptr,
|
|
BranchProbabilityInfo *BPI = nullptr,
|
|
AssumptionCache *AC = nullptr,
|
|
bool AllowVarArgs = false, bool AllowAlloca = false,
|
|
std::string Suffix = "");
|
|
|
|
/// Create a code extractor for a loop body.
|
|
///
|
|
/// Behaves just like the generic code sequence constructor, but uses the
|
|
/// block sequence of the loop.
|
|
CodeExtractor(DominatorTree &DT, Loop &L, bool AggregateArgs = false,
|
|
BlockFrequencyInfo *BFI = nullptr,
|
|
BranchProbabilityInfo *BPI = nullptr,
|
|
AssumptionCache *AC = nullptr,
|
|
std::string Suffix = "");
|
|
|
|
/// Perform the extraction, returning the new function.
|
|
///
|
|
/// Returns zero when called on a CodeExtractor instance where isEligible
|
|
/// returns false.
|
|
Function *extractCodeRegion(const CodeExtractorAnalysisCache &CEAC);
|
|
|
|
/// Verify that assumption cache isn't stale after a region is extracted.
|
|
/// Returns true when verifier finds errors. AssumptionCache is passed as
|
|
/// parameter to make this function stateless.
|
|
static bool verifyAssumptionCache(const Function &OldFunc,
|
|
const Function &NewFunc,
|
|
AssumptionCache *AC);
|
|
|
|
/// Test whether this code extractor is eligible.
|
|
///
|
|
/// Based on the blocks used when constructing the code extractor,
|
|
/// determine whether it is eligible for extraction.
|
|
///
|
|
/// Checks that varargs handling (with vastart and vaend) is only done in
|
|
/// the outlined blocks.
|
|
bool isEligible() const;
|
|
|
|
/// Compute the set of input values and output values for the code.
|
|
///
|
|
/// These can be used either when performing the extraction or to evaluate
|
|
/// the expected size of a call to the extracted function. Note that this
|
|
/// work cannot be cached between the two as once we decide to extract
|
|
/// a code sequence, that sequence is modified, including changing these
|
|
/// sets, before extraction occurs. These modifications won't have any
|
|
/// significant impact on the cost however.
|
|
void findInputsOutputs(ValueSet &Inputs, ValueSet &Outputs,
|
|
const ValueSet &Allocas) const;
|
|
|
|
/// Check if life time marker nodes can be hoisted/sunk into the outline
|
|
/// region.
|
|
///
|
|
/// Returns true if it is safe to do the code motion.
|
|
bool
|
|
isLegalToShrinkwrapLifetimeMarkers(const CodeExtractorAnalysisCache &CEAC,
|
|
Instruction *AllocaAddr) const;
|
|
|
|
/// Find the set of allocas whose life ranges are contained within the
|
|
/// outlined region.
|
|
///
|
|
/// Allocas which have life_time markers contained in the outlined region
|
|
/// should be pushed to the outlined function. The address bitcasts that
|
|
/// are used by the lifetime markers are also candidates for shrink-
|
|
/// wrapping. The instructions that need to be sunk are collected in
|
|
/// 'Allocas'.
|
|
void findAllocas(const CodeExtractorAnalysisCache &CEAC,
|
|
ValueSet &SinkCands, ValueSet &HoistCands,
|
|
BasicBlock *&ExitBlock) const;
|
|
|
|
/// Find or create a block within the outline region for placing hoisted
|
|
/// code.
|
|
///
|
|
/// CommonExitBlock is block outside the outline region. It is the common
|
|
/// successor of blocks inside the region. If there exists a single block
|
|
/// inside the region that is the predecessor of CommonExitBlock, that block
|
|
/// will be returned. Otherwise CommonExitBlock will be split and the
|
|
/// original block will be added to the outline region.
|
|
BasicBlock *findOrCreateBlockForHoisting(BasicBlock *CommonExitBlock);
|
|
|
|
private:
|
|
struct LifetimeMarkerInfo {
|
|
bool SinkLifeStart = false;
|
|
bool HoistLifeEnd = false;
|
|
Instruction *LifeStart = nullptr;
|
|
Instruction *LifeEnd = nullptr;
|
|
};
|
|
|
|
LifetimeMarkerInfo
|
|
getLifetimeMarkers(const CodeExtractorAnalysisCache &CEAC,
|
|
Instruction *Addr, BasicBlock *ExitBlock) const;
|
|
|
|
void severSplitPHINodesOfEntry(BasicBlock *&Header);
|
|
void severSplitPHINodesOfExits(const SmallPtrSetImpl<BasicBlock *> &Exits);
|
|
void splitReturnBlocks();
|
|
|
|
Function *constructFunction(const ValueSet &inputs,
|
|
const ValueSet &outputs,
|
|
BasicBlock *header,
|
|
BasicBlock *newRootNode, BasicBlock *newHeader,
|
|
Function *oldFunction, Module *M);
|
|
|
|
void moveCodeToFunction(Function *newFunction);
|
|
|
|
void calculateNewCallTerminatorWeights(
|
|
BasicBlock *CodeReplacer,
|
|
DenseMap<BasicBlock *, BlockFrequency> &ExitWeights,
|
|
BranchProbabilityInfo *BPI);
|
|
|
|
CallInst *emitCallAndSwitchStatement(Function *newFunction,
|
|
BasicBlock *newHeader,
|
|
ValueSet &inputs, ValueSet &outputs);
|
|
};
|
|
|
|
} // end namespace llvm
|
|
|
|
#endif // LLVM_TRANSFORMS_UTILS_CODEEXTRACTOR_H
|