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llvm-for-llvmta/lib/Transforms/IPO/PartialInlining.cpp

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2022-04-25 10:02:23 +02:00
//===- PartialInlining.cpp - Inline parts of functions --------------------===//
//
// 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
//
//===----------------------------------------------------------------------===//
//
// This pass performs partial inlining, typically by inlining an if statement
// that surrounds the body of the function.
//
//===----------------------------------------------------------------------===//
#include "llvm/Transforms/IPO/PartialInlining.h"
#include "llvm/ADT/DenseMap.h"
#include "llvm/ADT/DenseSet.h"
#include "llvm/ADT/None.h"
#include "llvm/ADT/Optional.h"
#include "llvm/ADT/STLExtras.h"
#include "llvm/ADT/SmallVector.h"
#include "llvm/ADT/Statistic.h"
#include "llvm/Analysis/BlockFrequencyInfo.h"
#include "llvm/Analysis/BranchProbabilityInfo.h"
#include "llvm/Analysis/InlineCost.h"
#include "llvm/Analysis/LoopInfo.h"
#include "llvm/Analysis/OptimizationRemarkEmitter.h"
#include "llvm/Analysis/ProfileSummaryInfo.h"
#include "llvm/Analysis/TargetLibraryInfo.h"
#include "llvm/Analysis/TargetTransformInfo.h"
#include "llvm/IR/Attributes.h"
#include "llvm/IR/BasicBlock.h"
#include "llvm/IR/CFG.h"
#include "llvm/IR/DebugLoc.h"
#include "llvm/IR/DiagnosticInfo.h"
#include "llvm/IR/Dominators.h"
#include "llvm/IR/Function.h"
#include "llvm/IR/InstrTypes.h"
#include "llvm/IR/Instruction.h"
#include "llvm/IR/Instructions.h"
#include "llvm/IR/IntrinsicInst.h"
#include "llvm/IR/Intrinsics.h"
#include "llvm/IR/Module.h"
#include "llvm/IR/User.h"
#include "llvm/InitializePasses.h"
#include "llvm/Pass.h"
#include "llvm/Support/BlockFrequency.h"
#include "llvm/Support/BranchProbability.h"
#include "llvm/Support/Casting.h"
#include "llvm/Support/CommandLine.h"
#include "llvm/Support/ErrorHandling.h"
#include "llvm/Transforms/IPO.h"
#include "llvm/Transforms/Utils/Cloning.h"
#include "llvm/Transforms/Utils/CodeExtractor.h"
#include "llvm/Transforms/Utils/ValueMapper.h"
#include <algorithm>
#include <cassert>
#include <cstdint>
#include <functional>
#include <iterator>
#include <memory>
#include <tuple>
#include <vector>
using namespace llvm;
#define DEBUG_TYPE "partial-inlining"
STATISTIC(NumPartialInlined,
"Number of callsites functions partially inlined into.");
STATISTIC(NumColdOutlinePartialInlined, "Number of times functions with "
"cold outlined regions were partially "
"inlined into its caller(s).");
STATISTIC(NumColdRegionsFound,
"Number of cold single entry/exit regions found.");
STATISTIC(NumColdRegionsOutlined,
"Number of cold single entry/exit regions outlined.");
// Command line option to disable partial-inlining. The default is false:
static cl::opt<bool>
DisablePartialInlining("disable-partial-inlining", cl::init(false),
cl::Hidden, cl::desc("Disable partial inlining"));
// Command line option to disable multi-region partial-inlining. The default is
// false:
static cl::opt<bool> DisableMultiRegionPartialInline(
"disable-mr-partial-inlining", cl::init(false), cl::Hidden,
cl::desc("Disable multi-region partial inlining"));
// Command line option to force outlining in regions with live exit variables.
// The default is false:
static cl::opt<bool>
ForceLiveExit("pi-force-live-exit-outline", cl::init(false), cl::Hidden,
cl::desc("Force outline regions with live exits"));
// Command line option to enable marking outline functions with Cold Calling
// Convention. The default is false:
static cl::opt<bool>
MarkOutlinedColdCC("pi-mark-coldcc", cl::init(false), cl::Hidden,
cl::desc("Mark outline function calls with ColdCC"));
// This is an option used by testing:
static cl::opt<bool> SkipCostAnalysis("skip-partial-inlining-cost-analysis",
cl::init(false), cl::ZeroOrMore,
cl::ReallyHidden,
cl::desc("Skip Cost Analysis"));
// Used to determine if a cold region is worth outlining based on
// its inlining cost compared to the original function. Default is set at 10%.
// ie. if the cold region reduces the inlining cost of the original function by
// at least 10%.
static cl::opt<float> MinRegionSizeRatio(
"min-region-size-ratio", cl::init(0.1), cl::Hidden,
cl::desc("Minimum ratio comparing relative sizes of each "
"outline candidate and original function"));
// Used to tune the minimum number of execution counts needed in the predecessor
// block to the cold edge. ie. confidence interval.
static cl::opt<unsigned>
MinBlockCounterExecution("min-block-execution", cl::init(100), cl::Hidden,
cl::desc("Minimum block executions to consider "
"its BranchProbabilityInfo valid"));
// Used to determine when an edge is considered cold. Default is set to 10%. ie.
// if the branch probability is 10% or less, then it is deemed as 'cold'.
static cl::opt<float> ColdBranchRatio(
"cold-branch-ratio", cl::init(0.1), cl::Hidden,
cl::desc("Minimum BranchProbability to consider a region cold."));
static cl::opt<unsigned> MaxNumInlineBlocks(
"max-num-inline-blocks", cl::init(5), cl::Hidden,
cl::desc("Max number of blocks to be partially inlined"));
// Command line option to set the maximum number of partial inlining allowed
// for the module. The default value of -1 means no limit.
static cl::opt<int> MaxNumPartialInlining(
"max-partial-inlining", cl::init(-1), cl::Hidden, cl::ZeroOrMore,
cl::desc("Max number of partial inlining. The default is unlimited"));
// Used only when PGO or user annotated branch data is absent. It is
// the least value that is used to weigh the outline region. If BFI
// produces larger value, the BFI value will be used.
static cl::opt<int>
OutlineRegionFreqPercent("outline-region-freq-percent", cl::init(75),
cl::Hidden, cl::ZeroOrMore,
cl::desc("Relative frequency of outline region to "
"the entry block"));
static cl::opt<unsigned> ExtraOutliningPenalty(
"partial-inlining-extra-penalty", cl::init(0), cl::Hidden,
cl::desc("A debug option to add additional penalty to the computed one."));
namespace {
struct FunctionOutliningInfo {
FunctionOutliningInfo() = default;
// Returns the number of blocks to be inlined including all blocks
// in Entries and one return block.
unsigned getNumInlinedBlocks() const { return Entries.size() + 1; }
// A set of blocks including the function entry that guard
// the region to be outlined.
SmallVector<BasicBlock *, 4> Entries;
// The return block that is not included in the outlined region.
BasicBlock *ReturnBlock = nullptr;
// The dominating block of the region to be outlined.
BasicBlock *NonReturnBlock = nullptr;
// The set of blocks in Entries that that are predecessors to ReturnBlock
SmallVector<BasicBlock *, 4> ReturnBlockPreds;
};
struct FunctionOutliningMultiRegionInfo {
FunctionOutliningMultiRegionInfo()
: ORI() {}
// Container for outline regions
struct OutlineRegionInfo {
OutlineRegionInfo(ArrayRef<BasicBlock *> Region,
BasicBlock *EntryBlock, BasicBlock *ExitBlock,
BasicBlock *ReturnBlock)
: Region(Region.begin(), Region.end()), EntryBlock(EntryBlock),
ExitBlock(ExitBlock), ReturnBlock(ReturnBlock) {}
SmallVector<BasicBlock *, 8> Region;
BasicBlock *EntryBlock;
BasicBlock *ExitBlock;
BasicBlock *ReturnBlock;
};
SmallVector<OutlineRegionInfo, 4> ORI;
};
struct PartialInlinerImpl {
PartialInlinerImpl(
function_ref<AssumptionCache &(Function &)> GetAC,
function_ref<AssumptionCache *(Function &)> LookupAC,
function_ref<TargetTransformInfo &(Function &)> GTTI,
function_ref<const TargetLibraryInfo &(Function &)> GTLI,
ProfileSummaryInfo &ProfSI,
function_ref<BlockFrequencyInfo &(Function &)> GBFI = nullptr)
: GetAssumptionCache(GetAC), LookupAssumptionCache(LookupAC),
GetTTI(GTTI), GetBFI(GBFI), GetTLI(GTLI), PSI(ProfSI) {}
bool run(Module &M);
// Main part of the transformation that calls helper functions to find
// outlining candidates, clone & outline the function, and attempt to
// partially inline the resulting function. Returns true if
// inlining was successful, false otherwise. Also returns the outline
// function (only if we partially inlined early returns) as there is a
// possibility to further "peel" early return statements that were left in the
// outline function due to code size.
std::pair<bool, Function *> unswitchFunction(Function &F);
// This class speculatively clones the function to be partial inlined.
// At the end of partial inlining, the remaining callsites to the cloned
// function that are not partially inlined will be fixed up to reference
// the original function, and the cloned function will be erased.
struct FunctionCloner {
// Two constructors, one for single region outlining, the other for
// multi-region outlining.
FunctionCloner(Function *F, FunctionOutliningInfo *OI,
OptimizationRemarkEmitter &ORE,
function_ref<AssumptionCache *(Function &)> LookupAC,
function_ref<TargetTransformInfo &(Function &)> GetTTI);
FunctionCloner(Function *F, FunctionOutliningMultiRegionInfo *OMRI,
OptimizationRemarkEmitter &ORE,
function_ref<AssumptionCache *(Function &)> LookupAC,
function_ref<TargetTransformInfo &(Function &)> GetTTI);
~FunctionCloner();
// Prepare for function outlining: making sure there is only
// one incoming edge from the extracted/outlined region to
// the return block.
void normalizeReturnBlock() const;
// Do function outlining for cold regions.
bool doMultiRegionFunctionOutlining();
// Do function outlining for region after early return block(s).
// NOTE: For vararg functions that do the vararg handling in the outlined
// function, we temporarily generate IR that does not properly
// forward varargs to the outlined function. Calling InlineFunction
// will update calls to the outlined functions to properly forward
// the varargs.
Function *doSingleRegionFunctionOutlining();
Function *OrigFunc = nullptr;
Function *ClonedFunc = nullptr;
typedef std::pair<Function *, BasicBlock *> FuncBodyCallerPair;
// Keep track of Outlined Functions and the basic block they're called from.
SmallVector<FuncBodyCallerPair, 4> OutlinedFunctions;
// ClonedFunc is inlined in one of its callers after function
// outlining.
bool IsFunctionInlined = false;
// The cost of the region to be outlined.
int OutlinedRegionCost = 0;
// ClonedOI is specific to outlining non-early return blocks.
std::unique_ptr<FunctionOutliningInfo> ClonedOI = nullptr;
// ClonedOMRI is specific to outlining cold regions.
std::unique_ptr<FunctionOutliningMultiRegionInfo> ClonedOMRI = nullptr;
std::unique_ptr<BlockFrequencyInfo> ClonedFuncBFI = nullptr;
OptimizationRemarkEmitter &ORE;
function_ref<AssumptionCache *(Function &)> LookupAC;
function_ref<TargetTransformInfo &(Function &)> GetTTI;
};
private:
int NumPartialInlining = 0;
function_ref<AssumptionCache &(Function &)> GetAssumptionCache;
function_ref<AssumptionCache *(Function &)> LookupAssumptionCache;
function_ref<TargetTransformInfo &(Function &)> GetTTI;
function_ref<BlockFrequencyInfo &(Function &)> GetBFI;
function_ref<const TargetLibraryInfo &(Function &)> GetTLI;
ProfileSummaryInfo &PSI;
// Return the frequency of the OutlininingBB relative to F's entry point.
// The result is no larger than 1 and is represented using BP.
// (Note that the outlined region's 'head' block can only have incoming
// edges from the guarding entry blocks).
BranchProbability
getOutliningCallBBRelativeFreq(FunctionCloner &Cloner) const;
// Return true if the callee of CB should be partially inlined with
// profit.
bool shouldPartialInline(CallBase &CB, FunctionCloner &Cloner,
BlockFrequency WeightedOutliningRcost,
OptimizationRemarkEmitter &ORE) const;
// Try to inline DuplicateFunction (cloned from F with call to
// the OutlinedFunction into its callers. Return true
// if there is any successful inlining.
bool tryPartialInline(FunctionCloner &Cloner);
// Compute the mapping from use site of DuplicationFunction to the enclosing
// BB's profile count.
void
computeCallsiteToProfCountMap(Function *DuplicateFunction,
DenseMap<User *, uint64_t> &SiteCountMap) const;
bool isLimitReached() const {
return (MaxNumPartialInlining != -1 &&
NumPartialInlining >= MaxNumPartialInlining);
}
static CallBase *getSupportedCallBase(User *U) {
if (isa<CallInst>(U) || isa<InvokeInst>(U))
return cast<CallBase>(U);
llvm_unreachable("All uses must be calls");
return nullptr;
}
static CallBase *getOneCallSiteTo(Function &F) {
User *User = *F.user_begin();
return getSupportedCallBase(User);
}
std::tuple<DebugLoc, BasicBlock *> getOneDebugLoc(Function &F) const {
CallBase *CB = getOneCallSiteTo(F);
DebugLoc DLoc = CB->getDebugLoc();
BasicBlock *Block = CB->getParent();
return std::make_tuple(DLoc, Block);
}
// Returns the costs associated with function outlining:
// - The first value is the non-weighted runtime cost for making the call
// to the outlined function, including the addtional setup cost in the
// outlined function itself;
// - The second value is the estimated size of the new call sequence in
// basic block Cloner.OutliningCallBB;
std::tuple<int, int> computeOutliningCosts(FunctionCloner &Cloner) const;
// Compute the 'InlineCost' of block BB. InlineCost is a proxy used to
// approximate both the size and runtime cost (Note that in the current
// inline cost analysis, there is no clear distinction there either).
static int computeBBInlineCost(BasicBlock *BB, TargetTransformInfo *TTI);
std::unique_ptr<FunctionOutliningInfo>
computeOutliningInfo(Function &F) const;
std::unique_ptr<FunctionOutliningMultiRegionInfo>
computeOutliningColdRegionsInfo(Function &F,
OptimizationRemarkEmitter &ORE) const;
};
struct PartialInlinerLegacyPass : public ModulePass {
static char ID; // Pass identification, replacement for typeid
PartialInlinerLegacyPass() : ModulePass(ID) {
initializePartialInlinerLegacyPassPass(*PassRegistry::getPassRegistry());
}
void getAnalysisUsage(AnalysisUsage &AU) const override {
AU.addRequired<AssumptionCacheTracker>();
AU.addRequired<ProfileSummaryInfoWrapperPass>();
AU.addRequired<TargetTransformInfoWrapperPass>();
AU.addRequired<TargetLibraryInfoWrapperPass>();
}
bool runOnModule(Module &M) override {
if (skipModule(M))
return false;
AssumptionCacheTracker *ACT = &getAnalysis<AssumptionCacheTracker>();
TargetTransformInfoWrapperPass *TTIWP =
&getAnalysis<TargetTransformInfoWrapperPass>();
ProfileSummaryInfo &PSI =
getAnalysis<ProfileSummaryInfoWrapperPass>().getPSI();
auto GetAssumptionCache = [&ACT](Function &F) -> AssumptionCache & {
return ACT->getAssumptionCache(F);
};
auto LookupAssumptionCache = [ACT](Function &F) -> AssumptionCache * {
return ACT->lookupAssumptionCache(F);
};
auto GetTTI = [&TTIWP](Function &F) -> TargetTransformInfo & {
return TTIWP->getTTI(F);
};
auto GetTLI = [this](Function &F) -> TargetLibraryInfo & {
return this->getAnalysis<TargetLibraryInfoWrapperPass>().getTLI(F);
};
return PartialInlinerImpl(GetAssumptionCache, LookupAssumptionCache, GetTTI,
GetTLI, PSI)
.run(M);
}
};
} // end anonymous namespace
std::unique_ptr<FunctionOutliningMultiRegionInfo>
PartialInlinerImpl::computeOutliningColdRegionsInfo(
Function &F, OptimizationRemarkEmitter &ORE) const {
BasicBlock *EntryBlock = &F.front();
DominatorTree DT(F);
LoopInfo LI(DT);
BranchProbabilityInfo BPI(F, LI);
std::unique_ptr<BlockFrequencyInfo> ScopedBFI;
BlockFrequencyInfo *BFI;
if (!GetBFI) {
ScopedBFI.reset(new BlockFrequencyInfo(F, BPI, LI));
BFI = ScopedBFI.get();
} else
BFI = &(GetBFI(F));
// Return if we don't have profiling information.
if (!PSI.hasInstrumentationProfile())
return std::unique_ptr<FunctionOutliningMultiRegionInfo>();
std::unique_ptr<FunctionOutliningMultiRegionInfo> OutliningInfo =
std::make_unique<FunctionOutliningMultiRegionInfo>();
auto IsSingleExit =
[&ORE](SmallVectorImpl<BasicBlock *> &BlockList) -> BasicBlock * {
BasicBlock *ExitBlock = nullptr;
for (auto *Block : BlockList) {
for (auto SI = succ_begin(Block); SI != succ_end(Block); ++SI) {
if (!is_contained(BlockList, *SI)) {
if (ExitBlock) {
ORE.emit([&]() {
return OptimizationRemarkMissed(DEBUG_TYPE, "MultiExitRegion",
&SI->front())
<< "Region dominated by "
<< ore::NV("Block", BlockList.front()->getName())
<< " has more than one region exit edge.";
});
return nullptr;
}
ExitBlock = Block;
}
}
}
return ExitBlock;
};
auto BBProfileCount = [BFI](BasicBlock *BB) {
return BFI->getBlockProfileCount(BB)
? BFI->getBlockProfileCount(BB).getValue()
: 0;
};
// Use the same computeBBInlineCost function to compute the cost savings of
// the outlining the candidate region.
TargetTransformInfo *FTTI = &GetTTI(F);
int OverallFunctionCost = 0;
for (auto &BB : F)
OverallFunctionCost += computeBBInlineCost(&BB, FTTI);
LLVM_DEBUG(dbgs() << "OverallFunctionCost = " << OverallFunctionCost
<< "\n";);
int MinOutlineRegionCost =
static_cast<int>(OverallFunctionCost * MinRegionSizeRatio);
BranchProbability MinBranchProbability(
static_cast<int>(ColdBranchRatio * MinBlockCounterExecution),
MinBlockCounterExecution);
bool ColdCandidateFound = false;
BasicBlock *CurrEntry = EntryBlock;
std::vector<BasicBlock *> DFS;
DenseMap<BasicBlock *, bool> VisitedMap;
DFS.push_back(CurrEntry);
VisitedMap[CurrEntry] = true;
// Use Depth First Search on the basic blocks to find CFG edges that are
// considered cold.
// Cold regions considered must also have its inline cost compared to the
// overall inline cost of the original function. The region is outlined only
// if it reduced the inline cost of the function by 'MinOutlineRegionCost' or
// more.
while (!DFS.empty()) {
auto *ThisBB = DFS.back();
DFS.pop_back();
// Only consider regions with predecessor blocks that are considered
// not-cold (default: part of the top 99.99% of all block counters)
// AND greater than our minimum block execution count (default: 100).
if (PSI.isColdBlock(ThisBB, BFI) ||
BBProfileCount(ThisBB) < MinBlockCounterExecution)
continue;
for (auto SI = succ_begin(ThisBB); SI != succ_end(ThisBB); ++SI) {
if (VisitedMap[*SI])
continue;
VisitedMap[*SI] = true;
DFS.push_back(*SI);
// If branch isn't cold, we skip to the next one.
BranchProbability SuccProb = BPI.getEdgeProbability(ThisBB, *SI);
if (SuccProb > MinBranchProbability)
continue;
LLVM_DEBUG(dbgs() << "Found cold edge: " << ThisBB->getName() << "->"
<< SI->getName()
<< "\nBranch Probability = " << SuccProb << "\n";);
SmallVector<BasicBlock *, 8> DominateVector;
DT.getDescendants(*SI, DominateVector);
assert(!DominateVector.empty() &&
"SI should be reachable and have at least itself as descendant");
// We can only outline single entry regions (for now).
if (!DominateVector.front()->hasNPredecessors(1)) {
LLVM_DEBUG(dbgs() << "ABORT: Block " << SI->getName()
<< " doesn't have a single predecessor in the "
"dominator tree\n";);
continue;
}
BasicBlock *ExitBlock = nullptr;
// We can only outline single exit regions (for now).
if (!(ExitBlock = IsSingleExit(DominateVector))) {
LLVM_DEBUG(dbgs() << "ABORT: Block " << SI->getName()
<< " doesn't have a unique successor\n";);
continue;
}
int OutlineRegionCost = 0;
for (auto *BB : DominateVector)
OutlineRegionCost += computeBBInlineCost(BB, &GetTTI(*BB->getParent()));
LLVM_DEBUG(dbgs() << "OutlineRegionCost = " << OutlineRegionCost
<< "\n";);
if (!SkipCostAnalysis && OutlineRegionCost < MinOutlineRegionCost) {
ORE.emit([&]() {
return OptimizationRemarkAnalysis(DEBUG_TYPE, "TooCostly",
&SI->front())
<< ore::NV("Callee", &F)
<< " inline cost-savings smaller than "
<< ore::NV("Cost", MinOutlineRegionCost);
});
LLVM_DEBUG(dbgs() << "ABORT: Outline region cost is smaller than "
<< MinOutlineRegionCost << "\n";);
continue;
}
// For now, ignore blocks that belong to a SISE region that is a
// candidate for outlining. In the future, we may want to look
// at inner regions because the outer region may have live-exit
// variables.
for (auto *BB : DominateVector)
VisitedMap[BB] = true;
// ReturnBlock here means the block after the outline call
BasicBlock *ReturnBlock = ExitBlock->getSingleSuccessor();
FunctionOutliningMultiRegionInfo::OutlineRegionInfo RegInfo(
DominateVector, DominateVector.front(), ExitBlock, ReturnBlock);
OutliningInfo->ORI.push_back(RegInfo);
LLVM_DEBUG(dbgs() << "Found Cold Candidate starting at block: "
<< DominateVector.front()->getName() << "\n";);
ColdCandidateFound = true;
NumColdRegionsFound++;
}
}
if (ColdCandidateFound)
return OutliningInfo;
return std::unique_ptr<FunctionOutliningMultiRegionInfo>();
}
std::unique_ptr<FunctionOutliningInfo>
PartialInlinerImpl::computeOutliningInfo(Function &F) const {
BasicBlock *EntryBlock = &F.front();
BranchInst *BR = dyn_cast<BranchInst>(EntryBlock->getTerminator());
if (!BR || BR->isUnconditional())
return std::unique_ptr<FunctionOutliningInfo>();
// Returns true if Succ is BB's successor
auto IsSuccessor = [](BasicBlock *Succ, BasicBlock *BB) {
return is_contained(successors(BB), Succ);
};
auto IsReturnBlock = [](BasicBlock *BB) {
Instruction *TI = BB->getTerminator();
return isa<ReturnInst>(TI);
};
auto GetReturnBlock = [&](BasicBlock *Succ1, BasicBlock *Succ2) {
if (IsReturnBlock(Succ1))
return std::make_tuple(Succ1, Succ2);
if (IsReturnBlock(Succ2))
return std::make_tuple(Succ2, Succ1);
return std::make_tuple<BasicBlock *, BasicBlock *>(nullptr, nullptr);
};
// Detect a triangular shape:
auto GetCommonSucc = [&](BasicBlock *Succ1, BasicBlock *Succ2) {
if (IsSuccessor(Succ1, Succ2))
return std::make_tuple(Succ1, Succ2);
if (IsSuccessor(Succ2, Succ1))
return std::make_tuple(Succ2, Succ1);
return std::make_tuple<BasicBlock *, BasicBlock *>(nullptr, nullptr);
};
std::unique_ptr<FunctionOutliningInfo> OutliningInfo =
std::make_unique<FunctionOutliningInfo>();
BasicBlock *CurrEntry = EntryBlock;
bool CandidateFound = false;
do {
// The number of blocks to be inlined has already reached
// the limit. When MaxNumInlineBlocks is set to 0 or 1, this
// disables partial inlining for the function.
if (OutliningInfo->getNumInlinedBlocks() >= MaxNumInlineBlocks)
break;
if (succ_size(CurrEntry) != 2)
break;
BasicBlock *Succ1 = *succ_begin(CurrEntry);
BasicBlock *Succ2 = *(succ_begin(CurrEntry) + 1);
BasicBlock *ReturnBlock, *NonReturnBlock;
std::tie(ReturnBlock, NonReturnBlock) = GetReturnBlock(Succ1, Succ2);
if (ReturnBlock) {
OutliningInfo->Entries.push_back(CurrEntry);
OutliningInfo->ReturnBlock = ReturnBlock;
OutliningInfo->NonReturnBlock = NonReturnBlock;
CandidateFound = true;
break;
}
BasicBlock *CommSucc, *OtherSucc;
std::tie(CommSucc, OtherSucc) = GetCommonSucc(Succ1, Succ2);
if (!CommSucc)
break;
OutliningInfo->Entries.push_back(CurrEntry);
CurrEntry = OtherSucc;
} while (true);
if (!CandidateFound)
return std::unique_ptr<FunctionOutliningInfo>();
// Do sanity check of the entries: threre should not
// be any successors (not in the entry set) other than
// {ReturnBlock, NonReturnBlock}
assert(OutliningInfo->Entries[0] == &F.front() &&
"Function Entry must be the first in Entries vector");
DenseSet<BasicBlock *> Entries;
for (BasicBlock *E : OutliningInfo->Entries)
Entries.insert(E);
// Returns true of BB has Predecessor which is not
// in Entries set.
auto HasNonEntryPred = [Entries](BasicBlock *BB) {
for (auto *Pred : predecessors(BB)) {
if (!Entries.count(Pred))
return true;
}
return false;
};
auto CheckAndNormalizeCandidate =
[Entries, HasNonEntryPred](FunctionOutliningInfo *OutliningInfo) {
for (BasicBlock *E : OutliningInfo->Entries) {
for (auto *Succ : successors(E)) {
if (Entries.count(Succ))
continue;
if (Succ == OutliningInfo->ReturnBlock)
OutliningInfo->ReturnBlockPreds.push_back(E);
else if (Succ != OutliningInfo->NonReturnBlock)
return false;
}
// There should not be any outside incoming edges either:
if (HasNonEntryPred(E))
return false;
}
return true;
};
if (!CheckAndNormalizeCandidate(OutliningInfo.get()))
return std::unique_ptr<FunctionOutliningInfo>();
// Now further growing the candidate's inlining region by
// peeling off dominating blocks from the outlining region:
while (OutliningInfo->getNumInlinedBlocks() < MaxNumInlineBlocks) {
BasicBlock *Cand = OutliningInfo->NonReturnBlock;
if (succ_size(Cand) != 2)
break;
if (HasNonEntryPred(Cand))
break;
BasicBlock *Succ1 = *succ_begin(Cand);
BasicBlock *Succ2 = *(succ_begin(Cand) + 1);
BasicBlock *ReturnBlock, *NonReturnBlock;
std::tie(ReturnBlock, NonReturnBlock) = GetReturnBlock(Succ1, Succ2);
if (!ReturnBlock || ReturnBlock != OutliningInfo->ReturnBlock)
break;
if (NonReturnBlock->getSinglePredecessor() != Cand)
break;
// Now grow and update OutlininigInfo:
OutliningInfo->Entries.push_back(Cand);
OutliningInfo->NonReturnBlock = NonReturnBlock;
OutliningInfo->ReturnBlockPreds.push_back(Cand);
Entries.insert(Cand);
}
return OutliningInfo;
}
// Check if there is PGO data or user annotated branch data:
static bool hasProfileData(const Function &F, const FunctionOutliningInfo &OI) {
if (F.hasProfileData())
return true;
// Now check if any of the entry block has MD_prof data:
for (auto *E : OI.Entries) {
BranchInst *BR = dyn_cast<BranchInst>(E->getTerminator());
if (!BR || BR->isUnconditional())
continue;
uint64_t T, F;
if (BR->extractProfMetadata(T, F))
return true;
}
return false;
}
BranchProbability PartialInlinerImpl::getOutliningCallBBRelativeFreq(
FunctionCloner &Cloner) const {
BasicBlock *OutliningCallBB = Cloner.OutlinedFunctions.back().second;
auto EntryFreq =
Cloner.ClonedFuncBFI->getBlockFreq(&Cloner.ClonedFunc->getEntryBlock());
auto OutliningCallFreq =
Cloner.ClonedFuncBFI->getBlockFreq(OutliningCallBB);
// FIXME Hackery needed because ClonedFuncBFI is based on the function BEFORE
// we outlined any regions, so we may encounter situations where the
// OutliningCallFreq is *slightly* bigger than the EntryFreq.
if (OutliningCallFreq.getFrequency() > EntryFreq.getFrequency())
OutliningCallFreq = EntryFreq;
auto OutlineRegionRelFreq = BranchProbability::getBranchProbability(
OutliningCallFreq.getFrequency(), EntryFreq.getFrequency());
if (hasProfileData(*Cloner.OrigFunc, *Cloner.ClonedOI.get()))
return OutlineRegionRelFreq;
// When profile data is not available, we need to be conservative in
// estimating the overall savings. Static branch prediction can usually
// guess the branch direction right (taken/non-taken), but the guessed
// branch probability is usually not biased enough. In case when the
// outlined region is predicted to be likely, its probability needs
// to be made higher (more biased) to not under-estimate the cost of
// function outlining. On the other hand, if the outlined region
// is predicted to be less likely, the predicted probablity is usually
// higher than the actual. For instance, the actual probability of the
// less likely target is only 5%, but the guessed probablity can be
// 40%. In the latter case, there is no need for further adjustement.
// FIXME: add an option for this.
if (OutlineRegionRelFreq < BranchProbability(45, 100))
return OutlineRegionRelFreq;
OutlineRegionRelFreq = std::max(
OutlineRegionRelFreq, BranchProbability(OutlineRegionFreqPercent, 100));
return OutlineRegionRelFreq;
}
bool PartialInlinerImpl::shouldPartialInline(
CallBase &CB, FunctionCloner &Cloner, BlockFrequency WeightedOutliningRcost,
OptimizationRemarkEmitter &ORE) const {
using namespace ore;
Function *Callee = CB.getCalledFunction();
assert(Callee == Cloner.ClonedFunc);
if (SkipCostAnalysis)
return isInlineViable(*Callee).isSuccess();
Function *Caller = CB.getCaller();
auto &CalleeTTI = GetTTI(*Callee);
bool RemarksEnabled =
Callee->getContext().getDiagHandlerPtr()->isMissedOptRemarkEnabled(
DEBUG_TYPE);
InlineCost IC =
getInlineCost(CB, getInlineParams(), CalleeTTI, GetAssumptionCache,
GetTLI, GetBFI, &PSI, RemarksEnabled ? &ORE : nullptr);
if (IC.isAlways()) {
ORE.emit([&]() {
return OptimizationRemarkAnalysis(DEBUG_TYPE, "AlwaysInline", &CB)
<< NV("Callee", Cloner.OrigFunc)
<< " should always be fully inlined, not partially";
});
return false;
}
if (IC.isNever()) {
ORE.emit([&]() {
return OptimizationRemarkMissed(DEBUG_TYPE, "NeverInline", &CB)
<< NV("Callee", Cloner.OrigFunc) << " not partially inlined into "
<< NV("Caller", Caller)
<< " because it should never be inlined (cost=never)";
});
return false;
}
if (!IC) {
ORE.emit([&]() {
return OptimizationRemarkAnalysis(DEBUG_TYPE, "TooCostly", &CB)
<< NV("Callee", Cloner.OrigFunc) << " not partially inlined into "
<< NV("Caller", Caller) << " because too costly to inline (cost="
<< NV("Cost", IC.getCost()) << ", threshold="
<< NV("Threshold", IC.getCostDelta() + IC.getCost()) << ")";
});
return false;
}
const DataLayout &DL = Caller->getParent()->getDataLayout();
// The savings of eliminating the call:
int NonWeightedSavings = getCallsiteCost(CB, DL);
BlockFrequency NormWeightedSavings(NonWeightedSavings);
// Weighted saving is smaller than weighted cost, return false
if (NormWeightedSavings < WeightedOutliningRcost) {
ORE.emit([&]() {
return OptimizationRemarkAnalysis(DEBUG_TYPE, "OutliningCallcostTooHigh",
&CB)
<< NV("Callee", Cloner.OrigFunc) << " not partially inlined into "
<< NV("Caller", Caller) << " runtime overhead (overhead="
<< NV("Overhead", (unsigned)WeightedOutliningRcost.getFrequency())
<< ", savings="
<< NV("Savings", (unsigned)NormWeightedSavings.getFrequency())
<< ")"
<< " of making the outlined call is too high";
});
return false;
}
ORE.emit([&]() {
return OptimizationRemarkAnalysis(DEBUG_TYPE, "CanBePartiallyInlined", &CB)
<< NV("Callee", Cloner.OrigFunc) << " can be partially inlined into "
<< NV("Caller", Caller) << " with cost=" << NV("Cost", IC.getCost())
<< " (threshold="
<< NV("Threshold", IC.getCostDelta() + IC.getCost()) << ")";
});
return true;
}
// TODO: Ideally we should share Inliner's InlineCost Analysis code.
// For now use a simplified version. The returned 'InlineCost' will be used
// to esimate the size cost as well as runtime cost of the BB.
int PartialInlinerImpl::computeBBInlineCost(BasicBlock *BB,
TargetTransformInfo *TTI) {
int InlineCost = 0;
const DataLayout &DL = BB->getParent()->getParent()->getDataLayout();
for (Instruction &I : BB->instructionsWithoutDebug()) {
// Skip free instructions.
switch (I.getOpcode()) {
case Instruction::BitCast:
case Instruction::PtrToInt:
case Instruction::IntToPtr:
case Instruction::Alloca:
case Instruction::PHI:
continue;
case Instruction::GetElementPtr:
if (cast<GetElementPtrInst>(&I)->hasAllZeroIndices())
continue;
break;
default:
break;
}
if (I.isLifetimeStartOrEnd())
continue;
if (auto *II = dyn_cast<IntrinsicInst>(&I)) {
Intrinsic::ID IID = II->getIntrinsicID();
SmallVector<Type *, 4> Tys;
FastMathFlags FMF;
for (Value *Val : II->args())
Tys.push_back(Val->getType());
if (auto *FPMO = dyn_cast<FPMathOperator>(II))
FMF = FPMO->getFastMathFlags();
IntrinsicCostAttributes ICA(IID, II->getType(), Tys, FMF);
InlineCost += TTI->getIntrinsicInstrCost(ICA, TTI::TCK_SizeAndLatency);
continue;
}
if (CallInst *CI = dyn_cast<CallInst>(&I)) {
InlineCost += getCallsiteCost(*CI, DL);
continue;
}
if (InvokeInst *II = dyn_cast<InvokeInst>(&I)) {
InlineCost += getCallsiteCost(*II, DL);
continue;
}
if (SwitchInst *SI = dyn_cast<SwitchInst>(&I)) {
InlineCost += (SI->getNumCases() + 1) * InlineConstants::InstrCost;
continue;
}
InlineCost += InlineConstants::InstrCost;
}
return InlineCost;
}
std::tuple<int, int>
PartialInlinerImpl::computeOutliningCosts(FunctionCloner &Cloner) const {
int OutliningFuncCallCost = 0, OutlinedFunctionCost = 0;
for (auto FuncBBPair : Cloner.OutlinedFunctions) {
Function *OutlinedFunc = FuncBBPair.first;
BasicBlock* OutliningCallBB = FuncBBPair.second;
// Now compute the cost of the call sequence to the outlined function
// 'OutlinedFunction' in BB 'OutliningCallBB':
auto *OutlinedFuncTTI = &GetTTI(*OutlinedFunc);
OutliningFuncCallCost +=
computeBBInlineCost(OutliningCallBB, OutlinedFuncTTI);
// Now compute the cost of the extracted/outlined function itself:
for (BasicBlock &BB : *OutlinedFunc)
OutlinedFunctionCost += computeBBInlineCost(&BB, OutlinedFuncTTI);
}
assert(OutlinedFunctionCost >= Cloner.OutlinedRegionCost &&
"Outlined function cost should be no less than the outlined region");
// The code extractor introduces a new root and exit stub blocks with
// additional unconditional branches. Those branches will be eliminated
// later with bb layout. The cost should be adjusted accordingly:
OutlinedFunctionCost -=
2 * InlineConstants::InstrCost * Cloner.OutlinedFunctions.size();
int OutliningRuntimeOverhead =
OutliningFuncCallCost +
(OutlinedFunctionCost - Cloner.OutlinedRegionCost) +
ExtraOutliningPenalty;
return std::make_tuple(OutliningFuncCallCost, OutliningRuntimeOverhead);
}
// Create the callsite to profile count map which is
// used to update the original function's entry count,
// after the function is partially inlined into the callsite.
void PartialInlinerImpl::computeCallsiteToProfCountMap(
Function *DuplicateFunction,
DenseMap<User *, uint64_t> &CallSiteToProfCountMap) const {
std::vector<User *> Users(DuplicateFunction->user_begin(),
DuplicateFunction->user_end());
Function *CurrentCaller = nullptr;
std::unique_ptr<BlockFrequencyInfo> TempBFI;
BlockFrequencyInfo *CurrentCallerBFI = nullptr;
auto ComputeCurrBFI = [&,this](Function *Caller) {
// For the old pass manager:
if (!GetBFI) {
DominatorTree DT(*Caller);
LoopInfo LI(DT);
BranchProbabilityInfo BPI(*Caller, LI);
TempBFI.reset(new BlockFrequencyInfo(*Caller, BPI, LI));
CurrentCallerBFI = TempBFI.get();
} else {
// New pass manager:
CurrentCallerBFI = &(GetBFI(*Caller));
}
};
for (User *User : Users) {
CallBase *CB = getSupportedCallBase(User);
Function *Caller = CB->getCaller();
if (CurrentCaller != Caller) {
CurrentCaller = Caller;
ComputeCurrBFI(Caller);
} else {
assert(CurrentCallerBFI && "CallerBFI is not set");
}
BasicBlock *CallBB = CB->getParent();
auto Count = CurrentCallerBFI->getBlockProfileCount(CallBB);
if (Count)
CallSiteToProfCountMap[User] = *Count;
else
CallSiteToProfCountMap[User] = 0;
}
}
PartialInlinerImpl::FunctionCloner::FunctionCloner(
Function *F, FunctionOutliningInfo *OI, OptimizationRemarkEmitter &ORE,
function_ref<AssumptionCache *(Function &)> LookupAC,
function_ref<TargetTransformInfo &(Function &)> GetTTI)
: OrigFunc(F), ORE(ORE), LookupAC(LookupAC), GetTTI(GetTTI) {
ClonedOI = std::make_unique<FunctionOutliningInfo>();
// Clone the function, so that we can hack away on it.
ValueToValueMapTy VMap;
ClonedFunc = CloneFunction(F, VMap);
ClonedOI->ReturnBlock = cast<BasicBlock>(VMap[OI->ReturnBlock]);
ClonedOI->NonReturnBlock = cast<BasicBlock>(VMap[OI->NonReturnBlock]);
for (BasicBlock *BB : OI->Entries)
ClonedOI->Entries.push_back(cast<BasicBlock>(VMap[BB]));
for (BasicBlock *E : OI->ReturnBlockPreds) {
BasicBlock *NewE = cast<BasicBlock>(VMap[E]);
ClonedOI->ReturnBlockPreds.push_back(NewE);
}
// Go ahead and update all uses to the duplicate, so that we can just
// use the inliner functionality when we're done hacking.
F->replaceAllUsesWith(ClonedFunc);
}
PartialInlinerImpl::FunctionCloner::FunctionCloner(
Function *F, FunctionOutliningMultiRegionInfo *OI,
OptimizationRemarkEmitter &ORE,
function_ref<AssumptionCache *(Function &)> LookupAC,
function_ref<TargetTransformInfo &(Function &)> GetTTI)
: OrigFunc(F), ORE(ORE), LookupAC(LookupAC), GetTTI(GetTTI) {
ClonedOMRI = std::make_unique<FunctionOutliningMultiRegionInfo>();
// Clone the function, so that we can hack away on it.
ValueToValueMapTy VMap;
ClonedFunc = CloneFunction(F, VMap);
// Go through all Outline Candidate Regions and update all BasicBlock
// information.
for (FunctionOutliningMultiRegionInfo::OutlineRegionInfo RegionInfo :
OI->ORI) {
SmallVector<BasicBlock *, 8> Region;
for (BasicBlock *BB : RegionInfo.Region)
Region.push_back(cast<BasicBlock>(VMap[BB]));
BasicBlock *NewEntryBlock = cast<BasicBlock>(VMap[RegionInfo.EntryBlock]);
BasicBlock *NewExitBlock = cast<BasicBlock>(VMap[RegionInfo.ExitBlock]);
BasicBlock *NewReturnBlock = nullptr;
if (RegionInfo.ReturnBlock)
NewReturnBlock = cast<BasicBlock>(VMap[RegionInfo.ReturnBlock]);
FunctionOutliningMultiRegionInfo::OutlineRegionInfo MappedRegionInfo(
Region, NewEntryBlock, NewExitBlock, NewReturnBlock);
ClonedOMRI->ORI.push_back(MappedRegionInfo);
}
// Go ahead and update all uses to the duplicate, so that we can just
// use the inliner functionality when we're done hacking.
F->replaceAllUsesWith(ClonedFunc);
}
void PartialInlinerImpl::FunctionCloner::normalizeReturnBlock() const {
auto GetFirstPHI = [](BasicBlock *BB) {
BasicBlock::iterator I = BB->begin();
PHINode *FirstPhi = nullptr;
while (I != BB->end()) {
PHINode *Phi = dyn_cast<PHINode>(I);
if (!Phi)
break;
if (!FirstPhi) {
FirstPhi = Phi;
break;
}
}
return FirstPhi;
};
// Shouldn't need to normalize PHIs if we're not outlining non-early return
// blocks.
if (!ClonedOI)
return;
// Special hackery is needed with PHI nodes that have inputs from more than
// one extracted block. For simplicity, just split the PHIs into a two-level
// sequence of PHIs, some of which will go in the extracted region, and some
// of which will go outside.
BasicBlock *PreReturn = ClonedOI->ReturnBlock;
// only split block when necessary:
PHINode *FirstPhi = GetFirstPHI(PreReturn);
unsigned NumPredsFromEntries = ClonedOI->ReturnBlockPreds.size();
if (!FirstPhi || FirstPhi->getNumIncomingValues() <= NumPredsFromEntries + 1)
return;
auto IsTrivialPhi = [](PHINode *PN) -> Value * {
Value *CommonValue = PN->getIncomingValue(0);
if (all_of(PN->incoming_values(),
[&](Value *V) { return V == CommonValue; }))
return CommonValue;
return nullptr;
};
ClonedOI->ReturnBlock = ClonedOI->ReturnBlock->splitBasicBlock(
ClonedOI->ReturnBlock->getFirstNonPHI()->getIterator());
BasicBlock::iterator I = PreReturn->begin();
Instruction *Ins = &ClonedOI->ReturnBlock->front();
SmallVector<Instruction *, 4> DeadPhis;
while (I != PreReturn->end()) {
PHINode *OldPhi = dyn_cast<PHINode>(I);
if (!OldPhi)
break;
PHINode *RetPhi =
PHINode::Create(OldPhi->getType(), NumPredsFromEntries + 1, "", Ins);
OldPhi->replaceAllUsesWith(RetPhi);
Ins = ClonedOI->ReturnBlock->getFirstNonPHI();
RetPhi->addIncoming(&*I, PreReturn);
for (BasicBlock *E : ClonedOI->ReturnBlockPreds) {
RetPhi->addIncoming(OldPhi->getIncomingValueForBlock(E), E);
OldPhi->removeIncomingValue(E);
}
// After incoming values splitting, the old phi may become trivial.
// Keeping the trivial phi can introduce definition inside the outline
// region which is live-out, causing necessary overhead (load, store
// arg passing etc).
if (auto *OldPhiVal = IsTrivialPhi(OldPhi)) {
OldPhi->replaceAllUsesWith(OldPhiVal);
DeadPhis.push_back(OldPhi);
}
++I;
}
for (auto *DP : DeadPhis)
DP->eraseFromParent();
for (auto *E : ClonedOI->ReturnBlockPreds)
E->getTerminator()->replaceUsesOfWith(PreReturn, ClonedOI->ReturnBlock);
}
bool PartialInlinerImpl::FunctionCloner::doMultiRegionFunctionOutlining() {
auto ComputeRegionCost = [&](SmallVectorImpl<BasicBlock *> &Region) {
int Cost = 0;
for (BasicBlock* BB : Region)
Cost += computeBBInlineCost(BB, &GetTTI(*BB->getParent()));
return Cost;
};
assert(ClonedOMRI && "Expecting OutlineInfo for multi region outline");
if (ClonedOMRI->ORI.empty())
return false;
// The CodeExtractor needs a dominator tree.
DominatorTree DT;
DT.recalculate(*ClonedFunc);
// Manually calculate a BlockFrequencyInfo and BranchProbabilityInfo.
LoopInfo LI(DT);
BranchProbabilityInfo BPI(*ClonedFunc, LI);
ClonedFuncBFI.reset(new BlockFrequencyInfo(*ClonedFunc, BPI, LI));
// Cache and recycle the CodeExtractor analysis to avoid O(n^2) compile-time.
CodeExtractorAnalysisCache CEAC(*ClonedFunc);
SetVector<Value *> Inputs, Outputs, Sinks;
for (FunctionOutliningMultiRegionInfo::OutlineRegionInfo RegionInfo :
ClonedOMRI->ORI) {
int CurrentOutlinedRegionCost = ComputeRegionCost(RegionInfo.Region);
CodeExtractor CE(RegionInfo.Region, &DT, /*AggregateArgs*/ false,
ClonedFuncBFI.get(), &BPI,
LookupAC(*RegionInfo.EntryBlock->getParent()),
/* AllowVarargs */ false);
CE.findInputsOutputs(Inputs, Outputs, Sinks);
LLVM_DEBUG({
dbgs() << "inputs: " << Inputs.size() << "\n";
dbgs() << "outputs: " << Outputs.size() << "\n";
for (Value *value : Inputs)
dbgs() << "value used in func: " << *value << "\n";
for (Value *output : Outputs)
dbgs() << "instr used in func: " << *output << "\n";
});
// Do not extract regions that have live exit variables.
if (Outputs.size() > 0 && !ForceLiveExit)
continue;
if (Function *OutlinedFunc = CE.extractCodeRegion(CEAC)) {
CallBase *OCS = PartialInlinerImpl::getOneCallSiteTo(*OutlinedFunc);
BasicBlock *OutliningCallBB = OCS->getParent();
assert(OutliningCallBB->getParent() == ClonedFunc);
OutlinedFunctions.push_back(std::make_pair(OutlinedFunc,OutliningCallBB));
NumColdRegionsOutlined++;
OutlinedRegionCost += CurrentOutlinedRegionCost;
if (MarkOutlinedColdCC) {
OutlinedFunc->setCallingConv(CallingConv::Cold);
OCS->setCallingConv(CallingConv::Cold);
}
} else
ORE.emit([&]() {
return OptimizationRemarkMissed(DEBUG_TYPE, "ExtractFailed",
&RegionInfo.Region.front()->front())
<< "Failed to extract region at block "
<< ore::NV("Block", RegionInfo.Region.front());
});
}
return !OutlinedFunctions.empty();
}
Function *
PartialInlinerImpl::FunctionCloner::doSingleRegionFunctionOutlining() {
// Returns true if the block is to be partial inlined into the caller
// (i.e. not to be extracted to the out of line function)
auto ToBeInlined = [&, this](BasicBlock *BB) {
return BB == ClonedOI->ReturnBlock ||
llvm::is_contained(ClonedOI->Entries, BB);
};
assert(ClonedOI && "Expecting OutlineInfo for single region outline");
// The CodeExtractor needs a dominator tree.
DominatorTree DT;
DT.recalculate(*ClonedFunc);
// Manually calculate a BlockFrequencyInfo and BranchProbabilityInfo.
LoopInfo LI(DT);
BranchProbabilityInfo BPI(*ClonedFunc, LI);
ClonedFuncBFI.reset(new BlockFrequencyInfo(*ClonedFunc, BPI, LI));
// Gather up the blocks that we're going to extract.
std::vector<BasicBlock *> ToExtract;
auto *ClonedFuncTTI = &GetTTI(*ClonedFunc);
ToExtract.push_back(ClonedOI->NonReturnBlock);
OutlinedRegionCost += PartialInlinerImpl::computeBBInlineCost(
ClonedOI->NonReturnBlock, ClonedFuncTTI);
for (BasicBlock &BB : *ClonedFunc)
if (!ToBeInlined(&BB) && &BB != ClonedOI->NonReturnBlock) {
ToExtract.push_back(&BB);
// FIXME: the code extractor may hoist/sink more code
// into the outlined function which may make the outlining
// overhead (the difference of the outlined function cost
// and OutliningRegionCost) look larger.
OutlinedRegionCost += computeBBInlineCost(&BB, ClonedFuncTTI);
}
// Extract the body of the if.
CodeExtractorAnalysisCache CEAC(*ClonedFunc);
Function *OutlinedFunc =
CodeExtractor(ToExtract, &DT, /*AggregateArgs*/ false,
ClonedFuncBFI.get(), &BPI, LookupAC(*ClonedFunc),
/* AllowVarargs */ true)
.extractCodeRegion(CEAC);
if (OutlinedFunc) {
BasicBlock *OutliningCallBB =
PartialInlinerImpl::getOneCallSiteTo(*OutlinedFunc)->getParent();
assert(OutliningCallBB->getParent() == ClonedFunc);
OutlinedFunctions.push_back(std::make_pair(OutlinedFunc, OutliningCallBB));
} else
ORE.emit([&]() {
return OptimizationRemarkMissed(DEBUG_TYPE, "ExtractFailed",
&ToExtract.front()->front())
<< "Failed to extract region at block "
<< ore::NV("Block", ToExtract.front());
});
return OutlinedFunc;
}
PartialInlinerImpl::FunctionCloner::~FunctionCloner() {
// Ditch the duplicate, since we're done with it, and rewrite all remaining
// users (function pointers, etc.) back to the original function.
ClonedFunc->replaceAllUsesWith(OrigFunc);
ClonedFunc->eraseFromParent();
if (!IsFunctionInlined) {
// Remove each function that was speculatively created if there is no
// reference.
for (auto FuncBBPair : OutlinedFunctions) {
Function *Func = FuncBBPair.first;
Func->eraseFromParent();
}
}
}
std::pair<bool, Function *> PartialInlinerImpl::unswitchFunction(Function &F) {
if (F.hasAddressTaken())
return {false, nullptr};
// Let inliner handle it
if (F.hasFnAttribute(Attribute::AlwaysInline))
return {false, nullptr};
if (F.hasFnAttribute(Attribute::NoInline))
return {false, nullptr};
if (PSI.isFunctionEntryCold(&F))
return {false, nullptr};
if (F.users().empty())
return {false, nullptr};
OptimizationRemarkEmitter ORE(&F);
// Only try to outline cold regions if we have a profile summary, which
// implies we have profiling information.
if (PSI.hasProfileSummary() && F.hasProfileData() &&
!DisableMultiRegionPartialInline) {
std::unique_ptr<FunctionOutliningMultiRegionInfo> OMRI =
computeOutliningColdRegionsInfo(F, ORE);
if (OMRI) {
FunctionCloner Cloner(&F, OMRI.get(), ORE, LookupAssumptionCache, GetTTI);
LLVM_DEBUG({
dbgs() << "HotCountThreshold = " << PSI.getHotCountThreshold() << "\n";
dbgs() << "ColdCountThreshold = " << PSI.getColdCountThreshold()
<< "\n";
});
bool DidOutline = Cloner.doMultiRegionFunctionOutlining();
if (DidOutline) {
LLVM_DEBUG({
dbgs() << ">>>>>> Outlined (Cloned) Function >>>>>>\n";
Cloner.ClonedFunc->print(dbgs());
dbgs() << "<<<<<< Outlined (Cloned) Function <<<<<<\n";
});
if (tryPartialInline(Cloner))
return {true, nullptr};
}
}
}
// Fall-thru to regular partial inlining if we:
// i) can't find any cold regions to outline, or
// ii) can't inline the outlined function anywhere.
std::unique_ptr<FunctionOutliningInfo> OI = computeOutliningInfo(F);
if (!OI)
return {false, nullptr};
FunctionCloner Cloner(&F, OI.get(), ORE, LookupAssumptionCache, GetTTI);
Cloner.normalizeReturnBlock();
Function *OutlinedFunction = Cloner.doSingleRegionFunctionOutlining();
if (!OutlinedFunction)
return {false, nullptr};
if (tryPartialInline(Cloner))
return {true, OutlinedFunction};
return {false, nullptr};
}
bool PartialInlinerImpl::tryPartialInline(FunctionCloner &Cloner) {
if (Cloner.OutlinedFunctions.empty())
return false;
int SizeCost = 0;
BlockFrequency WeightedRcost;
int NonWeightedRcost;
std::tie(SizeCost, NonWeightedRcost) = computeOutliningCosts(Cloner);
// Only calculate RelativeToEntryFreq when we are doing single region
// outlining.
BranchProbability RelativeToEntryFreq;
if (Cloner.ClonedOI)
RelativeToEntryFreq = getOutliningCallBBRelativeFreq(Cloner);
else
// RelativeToEntryFreq doesn't make sense when we have more than one
// outlined call because each call will have a different relative frequency
// to the entry block. We can consider using the average, but the
// usefulness of that information is questionable. For now, assume we never
// execute the calls to outlined functions.
RelativeToEntryFreq = BranchProbability(0, 1);
WeightedRcost = BlockFrequency(NonWeightedRcost) * RelativeToEntryFreq;
// The call sequence(s) to the outlined function(s) are larger than the sum of
// the original outlined region size(s), it does not increase the chances of
// inlining the function with outlining (The inliner uses the size increase to
// model the cost of inlining a callee).
if (!SkipCostAnalysis && Cloner.OutlinedRegionCost < SizeCost) {
OptimizationRemarkEmitter OrigFuncORE(Cloner.OrigFunc);
DebugLoc DLoc;
BasicBlock *Block;
std::tie(DLoc, Block) = getOneDebugLoc(*Cloner.ClonedFunc);
OrigFuncORE.emit([&]() {
return OptimizationRemarkAnalysis(DEBUG_TYPE, "OutlineRegionTooSmall",
DLoc, Block)
<< ore::NV("Function", Cloner.OrigFunc)
<< " not partially inlined into callers (Original Size = "
<< ore::NV("OutlinedRegionOriginalSize", Cloner.OutlinedRegionCost)
<< ", Size of call sequence to outlined function = "
<< ore::NV("NewSize", SizeCost) << ")";
});
return false;
}
assert(Cloner.OrigFunc->users().empty() &&
"F's users should all be replaced!");
std::vector<User *> Users(Cloner.ClonedFunc->user_begin(),
Cloner.ClonedFunc->user_end());
DenseMap<User *, uint64_t> CallSiteToProfCountMap;
auto CalleeEntryCount = Cloner.OrigFunc->getEntryCount();
if (CalleeEntryCount)
computeCallsiteToProfCountMap(Cloner.ClonedFunc, CallSiteToProfCountMap);
uint64_t CalleeEntryCountV =
(CalleeEntryCount ? CalleeEntryCount.getCount() : 0);
bool AnyInline = false;
for (User *User : Users) {
CallBase *CB = getSupportedCallBase(User);
if (isLimitReached())
continue;
OptimizationRemarkEmitter CallerORE(CB->getCaller());
if (!shouldPartialInline(*CB, Cloner, WeightedRcost, CallerORE))
continue;
// Construct remark before doing the inlining, as after successful inlining
// the callsite is removed.
OptimizationRemark OR(DEBUG_TYPE, "PartiallyInlined", CB);
OR << ore::NV("Callee", Cloner.OrigFunc) << " partially inlined into "
<< ore::NV("Caller", CB->getCaller());
InlineFunctionInfo IFI(nullptr, GetAssumptionCache, &PSI);
// We can only forward varargs when we outlined a single region, else we
// bail on vararg functions.
if (!InlineFunction(*CB, IFI, nullptr, true,
(Cloner.ClonedOI ? Cloner.OutlinedFunctions.back().first
: nullptr))
.isSuccess())
continue;
CallerORE.emit(OR);
// Now update the entry count:
if (CalleeEntryCountV && CallSiteToProfCountMap.count(User)) {
uint64_t CallSiteCount = CallSiteToProfCountMap[User];
CalleeEntryCountV -= std::min(CalleeEntryCountV, CallSiteCount);
}
AnyInline = true;
NumPartialInlining++;
// Update the stats
if (Cloner.ClonedOI)
NumPartialInlined++;
else
NumColdOutlinePartialInlined++;
}
if (AnyInline) {
Cloner.IsFunctionInlined = true;
if (CalleeEntryCount)
Cloner.OrigFunc->setEntryCount(
CalleeEntryCount.setCount(CalleeEntryCountV));
OptimizationRemarkEmitter OrigFuncORE(Cloner.OrigFunc);
OrigFuncORE.emit([&]() {
return OptimizationRemark(DEBUG_TYPE, "PartiallyInlined", Cloner.OrigFunc)
<< "Partially inlined into at least one caller";
});
}
return AnyInline;
}
bool PartialInlinerImpl::run(Module &M) {
if (DisablePartialInlining)
return false;
std::vector<Function *> Worklist;
Worklist.reserve(M.size());
for (Function &F : M)
if (!F.use_empty() && !F.isDeclaration())
Worklist.push_back(&F);
bool Changed = false;
while (!Worklist.empty()) {
Function *CurrFunc = Worklist.back();
Worklist.pop_back();
if (CurrFunc->use_empty())
continue;
bool Recursive = false;
for (User *U : CurrFunc->users())
if (Instruction *I = dyn_cast<Instruction>(U))
if (I->getParent()->getParent() == CurrFunc) {
Recursive = true;
break;
}
if (Recursive)
continue;
std::pair<bool, Function *> Result = unswitchFunction(*CurrFunc);
if (Result.second)
Worklist.push_back(Result.second);
Changed |= Result.first;
}
return Changed;
}
char PartialInlinerLegacyPass::ID = 0;
INITIALIZE_PASS_BEGIN(PartialInlinerLegacyPass, "partial-inliner",
"Partial Inliner", false, false)
INITIALIZE_PASS_DEPENDENCY(AssumptionCacheTracker)
INITIALIZE_PASS_DEPENDENCY(ProfileSummaryInfoWrapperPass)
INITIALIZE_PASS_DEPENDENCY(TargetTransformInfoWrapperPass)
INITIALIZE_PASS_DEPENDENCY(TargetLibraryInfoWrapperPass)
INITIALIZE_PASS_END(PartialInlinerLegacyPass, "partial-inliner",
"Partial Inliner", false, false)
ModulePass *llvm::createPartialInliningPass() {
return new PartialInlinerLegacyPass();
}
PreservedAnalyses PartialInlinerPass::run(Module &M,
ModuleAnalysisManager &AM) {
auto &FAM = AM.getResult<FunctionAnalysisManagerModuleProxy>(M).getManager();
auto GetAssumptionCache = [&FAM](Function &F) -> AssumptionCache & {
return FAM.getResult<AssumptionAnalysis>(F);
};
auto LookupAssumptionCache = [&FAM](Function &F) -> AssumptionCache * {
return FAM.getCachedResult<AssumptionAnalysis>(F);
};
auto GetBFI = [&FAM](Function &F) -> BlockFrequencyInfo & {
return FAM.getResult<BlockFrequencyAnalysis>(F);
};
auto GetTTI = [&FAM](Function &F) -> TargetTransformInfo & {
return FAM.getResult<TargetIRAnalysis>(F);
};
auto GetTLI = [&FAM](Function &F) -> TargetLibraryInfo & {
return FAM.getResult<TargetLibraryAnalysis>(F);
};
ProfileSummaryInfo &PSI = AM.getResult<ProfileSummaryAnalysis>(M);
if (PartialInlinerImpl(GetAssumptionCache, LookupAssumptionCache, GetTTI,
GetTLI, PSI, GetBFI)
.run(M))
return PreservedAnalyses::none();
return PreservedAnalyses::all();
}