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fuchsia / third_party / swift / 4b43cbe26b074889efa1c80c3253aa89c1cbf1e7 / . / lib / SILOptimizer / IPO / GlobalOpt.cpp
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//===--- GlobalOpt.cpp - Optimize global initializers ---------------------===//
//
// This source file is part of the Swift.org open source project
//
// Copyright (c) 2014 - 2017 Apple Inc. and the Swift project authors
// Licensed under Apache License v2.0 with Runtime Library Exception
//
// See https://swift.org/LICENSE.txt for license information
// See https://swift.org/CONTRIBUTORS.txt for the list of Swift project authors
//
//===----------------------------------------------------------------------===//
#define DEBUG_TYPE "globalopt"
#include "swift/Demangling/Demangle.h"
#include "swift/SIL/CFG.h"
#include "swift/SIL/DebugUtils.h"
#include "swift/SIL/SILInstruction.h"
#include "swift/SILOptimizer/Analysis/ColdBlockInfo.h"
#include "swift/SILOptimizer/Analysis/DominanceAnalysis.h"
#include "swift/SILOptimizer/PassManager/Passes.h"
#include "swift/SILOptimizer/PassManager/Transforms.h"
#include "swift/SILOptimizer/Utils/Local.h"
#include "swift/Demangling/Demangler.h"
#include "swift/Demangling/ManglingMacros.h"
#include "llvm/ADT/MapVector.h"
#include "llvm/ADT/SCCIterator.h"
#include "llvm/Support/CommandLine.h"
#include "llvm/Support/Debug.h"
#include "swift/AST/ASTMangler.h"
using namespace swift;
namespace {
/// Optimize the placement of global initializers.
///
/// TODO:
///
/// - Analyze the module to move initializers to the module's public
/// entry points.
///
/// - Convert trivial initializers to static initialization. This requires
/// serializing globals.
///
/// - For global "lets", generate addressors that return by value. If we also
/// converted to a static initializer, then remove the load from the addressor.
///
/// - When the addressor is local to the module, be sure it is inlined to allow
/// constant propagation in case of statically initialized "lets".
class SILGlobalOpt {
SILModule *Module;
DominanceAnalysis* DA;
bool HasChanged = false;
// Map each global initializer to a list of call sites.
typedef SmallVector<ApplyInst *, 4> GlobalInitCalls;
typedef SmallVector<LoadInst *, 4> GlobalLoads;
llvm::MapVector<SILFunction*, GlobalInitCalls> GlobalInitCallMap;
// The following mappings are used if this is a compilation
// in scripting mode and global variables are accessed without
// addressors.
// Map each global let variable to a set of loads from it.
llvm::MapVector<SILGlobalVariable*, GlobalLoads> GlobalLoadMap;
// Map each global let variable to the store instruction which initializes it.
llvm::MapVector<SILGlobalVariable*, StoreInst *> GlobalVarStore;
// Variables in this set should not be processed by this pass
// anymore.
llvm::SmallPtrSet<SILGlobalVariable*, 16> GlobalVarSkipProcessing;
// Mark any block that this pass has determined to be inside a loop.
llvm::DenseSet<SILBasicBlock*> LoopBlocks;
// Mark any functions for which loops have been analyzed.
llvm::DenseSet<SILFunction*> LoopCheckedFunctions;
// Keep track of cold blocks.
ColdBlockInfo ColdBlocks;
NominalTypeDecl *ArrayDecl;
int GlobIdx = 0;
// Whether we see a "once" call to callees that we currently don't handle.
bool UnhandledOnceCallee = false;
// Record number of times a globalinit_func is called by "once".
llvm::DenseMap<SILFunction*, unsigned> InitializerCount;
public:
SILGlobalOpt(SILModule *M, DominanceAnalysis *DA)
: Module(M), DA(DA), ColdBlocks(DA),
ArrayDecl(M->getASTContext().getArrayDecl()) {}
bool run();
protected:
void collectGlobalInitCall(ApplyInst *AI);
void collectGlobalLoad(LoadInst *SI, SILGlobalVariable *SILG);
void collectGlobalStore(StoreInst *SI, SILGlobalVariable *SILG);
void collectGlobalAccess(GlobalAddrInst *GAI);
bool isCOWType(SILType type) {
return type.getNominalOrBoundGenericNominal() == ArrayDecl;
}
bool isValidUseOfObject(SILInstruction *Val, bool isCOWObject,
ApplyInst **FindStringCall = nullptr);
bool getObjectInitVals(SILValue Val,
llvm::DenseMap<VarDecl *, StoreInst *> &MemberStores,
llvm::SmallVectorImpl<StoreInst *> &TailStores,
ApplyInst **FindStringCall);
bool handleTailAddr(int TailIdx, SILInstruction *I,
llvm::SmallVectorImpl<StoreInst *> &TailStores);
void optimizeObjectAllocation(AllocRefInst *ARI);
void replaceFindStringCall(ApplyInst *FindStringCall);
SILGlobalVariable *getVariableOfGlobalInit(SILFunction *AddrF);
bool isInLoop(SILBasicBlock *CurBB);
void placeInitializers(SILFunction *InitF, ArrayRef<ApplyInst*> Calls);
// Update UnhandledOnceCallee and InitializerCount by going through all "once"
// calls.
void collectOnceCall(BuiltinInst *AI);
// Set the static initializer and remove "once" from addressor if a global can
// be statically initialized.
void optimizeInitializer(SILFunction *AddrF, GlobalInitCalls &Calls);
void optimizeGlobalAccess(SILGlobalVariable *SILG, StoreInst *SI);
// Replace loads from a global variable by the known value.
void replaceLoadsByKnownValue(BuiltinInst *CallToOnce,
SILFunction *AddrF,
SILFunction *InitF,
SILGlobalVariable *SILG,
SILInstruction *InitVal,
GlobalInitCalls &Calls);
};
/// Helper class to copy only a set of SIL instructions providing in the
/// constructor.
class InstructionsCloner : public SILClonerWithScopes<InstructionsCloner> {
friend class SILVisitor<InstructionsCloner>;
friend class SILCloner<InstructionsCloner>;
ArrayRef<SILInstruction *> Insns;
protected:
SILBasicBlock *FromBB, *DestBB;
public:
// A map of old to new available values.
SmallVector<std::pair<ValueBase *, SILValue>, 16> AvailVals;
InstructionsCloner(SILFunction &F,
ArrayRef<SILInstruction *> Insns,
SILBasicBlock *Dest = nullptr)
: SILClonerWithScopes(F), Insns(Insns), FromBB(nullptr), DestBB(Dest) {}
void process(SILInstruction *I) { visit(I); }
SILBasicBlock *remapBasicBlock(SILBasicBlock *BB) { return BB; }
SILValue remapValue(SILValue Value) {
return SILCloner<InstructionsCloner>::remapValue(Value);
}
void postProcess(SILInstruction *Orig, SILInstruction *Cloned) {
DestBB->push_back(Cloned);
SILClonerWithScopes<InstructionsCloner>::postProcess(Orig, Cloned);
AvailVals.push_back(std::make_pair(Orig, Cloned));
}
// Clone all instructions from Insns into DestBB
void clone() {
for (auto I : Insns)
process(I);
}
};
} // end anonymous namespace
/// If this is a call to a global initializer, map it.
void SILGlobalOpt::collectGlobalInitCall(ApplyInst *AI) {
SILFunction *F = AI->getReferencedFunction();
if (!F || !F->isGlobalInit())
return;
GlobalInitCallMap[F].push_back(AI);
}
/// If this is a read from a global let variable, map it.
void SILGlobalOpt::collectGlobalLoad(LoadInst *LI, SILGlobalVariable *SILG) {
assert(SILG);
//assert(SILG->isLet());
// This is read from a let variable.
// Figure out if the value of this variable is statically known.
GlobalLoadMap[SILG].push_back(LI);
}
/// Remove an unused global token used by once calls.
static void removeToken(SILValue Op) {
if (auto *ATPI = dyn_cast<AddressToPointerInst>(Op)) {
Op = ATPI->getOperand();
if (ATPI->use_empty())
ATPI->eraseFromParent();
}
if (auto *GAI = dyn_cast<GlobalAddrInst>(Op)) {
auto *Global = GAI->getReferencedGlobal();
// If "global_addr token" is used more than one time, bail.
if (!(GAI->use_empty() || GAI->hasOneUse()))
return;
// If it is not a *_token global variable, bail.
if (!Global || Global->getName().find("_token") == StringRef::npos)
return;
GAI->getModule().eraseGlobalVariable(Global);
GAI->replaceAllUsesWithUndef();
GAI->eraseFromParent();
}
}
static std::string mangleGetter(VarDecl *varDecl) {
Mangle::ASTMangler Mangler;
return Mangler.mangleGlobalGetterEntity(varDecl);
}
/// Generate getter from the initialization code whose
/// result is stored by a given store instruction.
static SILFunction *genGetterFromInit(StoreInst *Store,
SILGlobalVariable *SILG) {
auto *varDecl = SILG->getDecl();
auto getterName = mangleGetter(varDecl);
// Check if a getter was generated already.
if (auto *F = Store->getModule().lookUpFunction(getterName))
return F;
// Find the code that performs the initialization first.
// Recursively walk the SIL value being assigned to the SILG.
auto V = Store->getSrc();
SmallVector<SILInstruction *, 8> ReverseInsns;
SmallVector<SILInstruction *, 8> Insns;
ReverseInsns.push_back(Store);
ReverseInsns.push_back(dyn_cast<SILInstruction>(Store->getDest()));
if (!analyzeStaticInitializer(V, ReverseInsns))
return nullptr;
// Produce a correct order of instructions.
while (!ReverseInsns.empty()) {
Insns.push_back(ReverseInsns.pop_back_val());
}
// Generate a getter from the global init function without side-effects.
auto refType = varDecl->getInterfaceType()->getCanonicalType();
// Function takes no arguments and returns refType
SILResultInfo Results[] = { SILResultInfo(refType, ResultConvention::Owned) };
SILFunctionType::ExtInfo EInfo;
EInfo = EInfo.withRepresentation(SILFunctionType::Representation::Thin);
auto LoweredType = SILFunctionType::get(nullptr, EInfo,
ParameterConvention::Direct_Owned, { }, Results, None,
Store->getModule().getASTContext());
auto *GetterF = Store->getModule().getOrCreateFunction(
Store->getLoc(),
getterName, SILLinkage::Private, LoweredType,
IsBare_t::IsBare, IsTransparent_t::IsNotTransparent,
IsSerialized_t::IsSerialized);
GetterF->setDebugScope(Store->getFunction()->getDebugScope());
if (Store->getFunction()->hasUnqualifiedOwnership())
GetterF->setUnqualifiedOwnership();
auto *EntryBB = GetterF->createBasicBlock();
// Copy instructions into GetterF
InstructionsCloner Cloner(*GetterF, Insns, EntryBB);
Cloner.clone();
GetterF->setInlined();
// Find the store instruction and turn it into return.
// Remove the alloc_global instruction.
auto BB = EntryBB;
SILValue Val;
for (auto II = BB->begin(), E = BB->end(); II != E;) {
auto &I = *II++;
if (isa<AllocGlobalInst>(&I)) {
I.eraseFromParent();
continue;
}
if (auto *SI = dyn_cast<StoreInst>(&I)) {
Val = SI->getSrc();
SILBuilderWithScope B(SI);
B.createReturn(SI->getLoc(), Val);
eraseUsesOfInstruction(SI);
recursivelyDeleteTriviallyDeadInstructions(SI, true);
return GetterF;
}
}
Store->getModule().getFunctionList().addNodeToList(GetterF);
return GetterF;
}
/// If this is a read from a global let variable, map it.
void SILGlobalOpt::collectGlobalStore(StoreInst *SI, SILGlobalVariable *SILG) {
if (GlobalVarStore.count(SILG)) {
// There is more then one assignment to a given global variable.
// Therefore we don't know its value.
GlobalVarSkipProcessing.insert(SILG);
}
// Figure out if the value of this variable is statically known.
GlobalVarStore[SILG] = SI;
}
/// Return the callee of a once call.
static SILFunction *getCalleeOfOnceCall(BuiltinInst *BI) {
assert(BI->getNumOperands() == 2 && "once call should have 2 operands.");
auto Callee = BI->getOperand(1);
assert(Callee->getType().castTo<SILFunctionType>()->getRepresentation()
== SILFunctionTypeRepresentation::Thin &&
"Expected thin function representation!");
if (auto *FR = dyn_cast<FunctionRefInst>(Callee))
return FR->getReferencedFunction();
return nullptr;
}
/// Update UnhandledOnceCallee and InitializerCount by going through all "once"
/// calls.
void SILGlobalOpt::collectOnceCall(BuiltinInst *BI) {
if (UnhandledOnceCallee)
return;
const BuiltinInfo &Builtin = Module->getBuiltinInfo(BI->getName());
if (Builtin.ID != BuiltinValueKind::Once)
return;
SILFunction *Callee = getCalleeOfOnceCall(BI);
if (!Callee) {
DEBUG(llvm::dbgs() << "GlobalOpt: unhandled once callee\n");
UnhandledOnceCallee = true;
return;
}
if (!Callee->getName().startswith("globalinit_"))
return;
// We currently disable optimizing the initializer if a globalinit_func
// is called by "once" from multiple locations.
if (!BI->getFunction()->isGlobalInit())
// If a globalinit_func is called by "once" from a function that is not
// an addressor, we set count to 2 to disable optimizing the initializer.
InitializerCount[Callee] = 2;
else
InitializerCount[Callee]++;
}
/// return true if this block is inside a loop.
bool SILGlobalOpt::isInLoop(SILBasicBlock *CurBB) {
SILFunction *F = CurBB->getParent();
// Catch the common case in which we've already hoisted the initializer.
if (CurBB == &F->front())
return false;
if (LoopCheckedFunctions.insert(F).second) {
for (auto I = scc_begin(F); !I.isAtEnd(); ++I) {
if (I.hasLoop())
for (SILBasicBlock *BB : *I)
LoopBlocks.insert(BB);
}
}
return LoopBlocks.count(CurBB);
}
/// Returns true if the block \p BB is terminated with a cond_br based on an
/// availability check.
static bool isAvailabilityCheck(SILBasicBlock *BB) {
auto *CBR = dyn_cast<CondBranchInst>(BB->getTerminator());
if (!CBR)
return false;
auto *AI = dyn_cast<ApplyInst>(CBR->getCondition());
if (!AI)
return false;
SILFunction *F = AI->getReferencedFunction();
if (!F || !F->hasSemanticsAttrs())
return false;
return F->hasSemanticsAttrThatStartsWith("availability");
}
/// Returns true if there are any availability checks along the dominator tree
/// from \p From to \p To.
static bool isAvailabilityCheckOnDomPath(SILBasicBlock *From, SILBasicBlock *To,
DominanceInfo *DT) {
if (From == To)
return false;
auto *Node = DT->getNode(To)->getIDom();
for (;;) {
SILBasicBlock *BB = Node->getBlock();
if (isAvailabilityCheck(BB))
return true;
if (BB == From)
return false;
Node = Node->getIDom();
assert(Node && "Should have hit To-block");
}
}
/// Optimize placement of initializer calls given a list of calls to the
/// same initializer. All original initialization points must be dominated by
/// the final initialization calls.
///
/// The current heuristic hoists all initialization points within a function to
/// a single dominating call in the outer loop preheader.
void SILGlobalOpt::placeInitializers(SILFunction *InitF,
ArrayRef<ApplyInst*> Calls) {
DEBUG(llvm::dbgs() << "GlobalOpt: calls to "
<< Demangle::demangleSymbolAsString(InitF->getName())
<< " : " << Calls.size() << "\n");
// Map each initializer-containing function to its final initializer call.
llvm::DenseMap<SILFunction*, ApplyInst*> ParentFuncs;
for (auto *AI : Calls) {
assert(AI->getNumArguments() == 0 && "ill-formed global init call");
assert(cast<FunctionRefInst>(AI->getCallee())->getReferencedFunction()
== InitF && "wrong init call");
SILFunction *ParentF = AI->getFunction();
DominanceInfo *DT = DA->get(ParentF);
auto PFI = ParentFuncs.find(ParentF);
ApplyInst *HoistAI = nullptr;
if (PFI != ParentFuncs.end()) {
// Found a replacement for this init call.
// Ensure the replacement dominates the original call site.
ApplyInst *CommonAI = PFI->second;
assert(cast<FunctionRefInst>(CommonAI->getCallee())
->getReferencedFunction() == InitF &&
"ill-formed global init call");
SILBasicBlock *DomBB =
DT->findNearestCommonDominator(AI->getParent(), CommonAI->getParent());
// We must not move initializers around availability-checks.
if (!isAvailabilityCheckOnDomPath(DomBB, CommonAI->getParent(), DT)) {
if (DomBB != CommonAI->getParent()) {
CommonAI->moveBefore(&*DomBB->begin());
placeFuncRef(CommonAI, DT);
// Try to hoist the existing AI again if we move it to another block,
// e.g. from a loop exit into the loop.
HoistAI = CommonAI;
}
AI->replaceAllUsesWith(CommonAI);
AI->eraseFromParent();
HasChanged = true;
}
} else {
ParentFuncs[ParentF] = AI;
// It's the first time we found a call to InitF in this function, so we
// try to hoist it out of any loop.
HoistAI = AI;
}
if (HoistAI) {
// Move this call to the outermost loop preheader.
SILBasicBlock *BB = HoistAI->getParent();
typedef llvm::DomTreeNodeBase<SILBasicBlock> DomTreeNode;
DomTreeNode *Node = DT->getNode(BB);
while (Node) {
SILBasicBlock *DomParentBB = Node->getBlock();
if (isAvailabilityCheck(DomParentBB)) {
DEBUG(llvm::dbgs() << " don't hoist above availability check at bb"
<< DomParentBB->getDebugID() << "\n");
break;
}
BB = DomParentBB;
if (!isInLoop(BB))
break;
Node = Node->getIDom();
}
if (BB == HoistAI->getParent()) {
// BB is either unreachable or not in a loop.
DEBUG(llvm::dbgs() << " skipping (not in a loop): " << *HoistAI
<< " in " << HoistAI->getFunction()->getName() << "\n");
}
else {
DEBUG(llvm::dbgs() << " hoisting: " << *HoistAI
<< " in " << HoistAI->getFunction()->getName() << "\n");
HoistAI->moveBefore(&*BB->begin());
placeFuncRef(HoistAI, DT);
HasChanged = true;
}
}
}
}
/// Create a getter function from the initializer function.
static SILFunction *genGetterFromInit(SILFunction *InitF, VarDecl *varDecl) {
// Generate a getter from the global init function without side-effects.
auto getterName = mangleGetter(varDecl);
// Check if a getter was generated already.
if (auto *F = InitF->getModule().lookUpFunction(getterName))
return F;
auto refType = varDecl->getInterfaceType()->getCanonicalType();
// Function takes no arguments and returns refType
SILResultInfo Results[] = { SILResultInfo(refType, ResultConvention::Owned) };
SILFunctionType::ExtInfo EInfo;
EInfo = EInfo.withRepresentation(SILFunctionType::Representation::Thin);
auto LoweredType = SILFunctionType::get(nullptr, EInfo,
ParameterConvention::Direct_Owned, { }, Results, None,
InitF->getASTContext());
auto *GetterF = InitF->getModule().getOrCreateFunction(
InitF->getLocation(),
getterName, SILLinkage::Private, LoweredType,
IsBare_t::IsBare, IsTransparent_t::IsNotTransparent,
IsSerialized_t::IsSerialized);
if (InitF->hasUnqualifiedOwnership())
GetterF->setUnqualifiedOwnership();
auto *EntryBB = GetterF->createBasicBlock();
// Copy InitF into GetterF
BasicBlockCloner Cloner(&*InitF->begin(), EntryBB, /*WithinFunction=*/false);
Cloner.clone();
GetterF->setInlined();
// Find the store instruction
auto BB = EntryBB;
SILValue Val;
SILInstruction *Store;
for (auto II = BB->begin(), E = BB->end(); II != E;) {
auto &I = *II++;
if (isa<AllocGlobalInst>(&I)) {
I.eraseFromParent();
continue;
}
if (auto *SI = dyn_cast<StoreInst>(&I)) {
Val = SI->getSrc();
Store = SI;
continue;
}
if (auto *RI = dyn_cast<ReturnInst>(&I)) {
SILBuilderWithScope B(RI);
B.createReturn(RI->getLoc(), Val);
eraseUsesOfInstruction(RI);
recursivelyDeleteTriviallyDeadInstructions(RI, true);
recursivelyDeleteTriviallyDeadInstructions(Store, true);
return GetterF;
}
}
InitF->getModule().getFunctionList().addNodeToList(GetterF);
return GetterF;
}
/// Find the globalinit_func by analyzing the body of the addressor.
static SILFunction *findInitializer(SILModule *Module, SILFunction *AddrF,
BuiltinInst *&CallToOnce) {
// We only handle a single SILBasicBlock for now.
if (AddrF->size() != 1)
return nullptr;
CallToOnce = nullptr;
SILBasicBlock *BB = &AddrF->front();
for (auto &I : *BB) {
// Find the builtin "once" call.
if (auto *BI = dyn_cast<BuiltinInst>(&I)) {
const BuiltinInfo &Builtin = Module->getBuiltinInfo(BI->getName());
if (Builtin.ID != BuiltinValueKind::Once)
continue;
// Bail if we have multiple "once" calls in the addressor.
if (CallToOnce)
return nullptr;
CallToOnce = BI;
}
}
if (!CallToOnce)
return nullptr;
return getCalleeOfOnceCall(CallToOnce);
}
/// Checks if a given global variable is assigned only once.
static bool isAssignedOnlyOnceInInitializer(SILGlobalVariable *SILG) {
if (SILG->isLet())
return true;
// TODO: If we can prove that a given global variable
// is assigned only once, during initialization, then
// we can treat it as if it is a let.
// If this global is internal or private, it should be
return false;
}
/// Replace load sequence which may contain
/// a chain of struct_element_addr followed by a load.
/// The sequence is traversed starting from the load
/// instruction.
static SILInstruction *convertLoadSequence(SILInstruction *I,
SILInstruction *Value,
SILBuilder &B) {
if (isa<GlobalAddrInst>(I))
return Value;
if (auto *LI = dyn_cast<LoadInst>(I)) {
Value =
convertLoadSequence(cast<SILInstruction>(LI->getOperand()), Value, B);
LI->replaceAllUsesWith(Value);
return Value;
}
// It is a series of struct_element_addr followed by load.
if (auto *SEAI = dyn_cast<StructElementAddrInst>(I)) {
Value =
convertLoadSequence(cast<SILInstruction>(SEAI->getOperand()), Value, B);
auto *SEI = B.createStructExtract(SEAI->getLoc(), Value, SEAI->getField());
return SEI;
}
if (auto *TEAI = dyn_cast<TupleElementAddrInst>(I)) {
Value =
convertLoadSequence(cast<SILInstruction>(TEAI->getOperand()), Value, B);
auto *TEI = B.createTupleExtract(TEAI->getLoc(), Value, TEAI->getFieldNo());
return TEI;
}
llvm_unreachable("Unknown instruction sequence for reading from a global");
return nullptr;
}
static SILGlobalVariable *getVariableOfStaticInitializer(SILFunction *InitFunc,
SILInstruction *&InitVal) {
InitVal = nullptr;
SILGlobalVariable *GVar = nullptr;
// We only handle a single SILBasicBlock for now.
if (InitFunc->size() != 1)
return nullptr;
SILBasicBlock *BB = &InitFunc->front();
GlobalAddrInst *SGA = nullptr;
bool HasStore = false;
for (auto &I : *BB) {
// Make sure we have a single GlobalAddrInst and a single StoreInst.
// And the StoreInst writes to the GlobalAddrInst.
if (isa<AllocGlobalInst>(&I) || isa<ReturnInst>(&I)
|| isa<DebugValueInst>(&I)) {
continue;
} else if (auto *sga = dyn_cast<GlobalAddrInst>(&I)) {
if (SGA)
return nullptr;
SGA = sga;
GVar = SGA->getReferencedGlobal();
} else if (auto *SI = dyn_cast<StoreInst>(&I)) {
if (HasStore || SI->getDest() != SGA)
return nullptr;
HasStore = true;
InitVal = dyn_cast<SILInstruction>(SI->getSrc());
// We only handle StructInst and TupleInst being stored to a
// global variable for now.
if (!isa<StructInst>(InitVal) && !isa<TupleInst>(InitVal))
return nullptr;
} else if (!SILGlobalVariable::isValidStaticInitializerInst(&I,
I.getModule())) {
return nullptr;
}
}
if (!InitVal)
return nullptr;
return GVar;
}
namespace {
/// Utility class for cloning init values into the static initializer of a
/// SILGlobalVariable.
class StaticInitCloner : public SILCloner<StaticInitCloner> {
friend class SILVisitor<StaticInitCloner>;
friend class SILCloner<StaticInitCloner>;
/// The number of not yet cloned operands for each instruction.
llvm::DenseMap<SILInstruction *, int> NumOpsToClone;
/// List of instructions for which all operands are already cloned (or which
/// don't have any operands).
llvm::SmallVector<SILInstruction *, 8> ReadyToClone;
public:
StaticInitCloner(SILGlobalVariable *GVar)
: SILCloner<StaticInitCloner>(GVar) { }
/// Add \p InitVal and all its operands (transitively) for cloning.
///
/// Note: all init values must are added, before calling clone().
void add(SILInstruction *InitVal);
/// Clone \p InitVal and all its operands into the initializer of the
/// SILGlobalVariable.
///
/// \return Returns the cloned instruction in the SILGlobalVariable.
SILInstruction *clone(SILInstruction *InitVal);
/// Convenience function to clone a single \p InitVal.
static void appendToInitializer(SILGlobalVariable *GVar,
SILInstruction *InitVal) {
StaticInitCloner Cloner(GVar);
Cloner.add(InitVal);
Cloner.clone(InitVal);
}
protected:
SILLocation remapLocation(SILLocation Loc) {
return ArtificialUnreachableLocation();
}
};
void StaticInitCloner::add(SILInstruction *InitVal) {
// Don't schedule an instruction twice for cloning.
if (NumOpsToClone.count(InitVal) != 0)
return;
ArrayRef<Operand> Ops = InitVal->getAllOperands();
NumOpsToClone[InitVal] = Ops.size();
if (Ops.empty()) {
// It's an instruction without operands, e.g. a literal. It's ready to be
// cloned first.
ReadyToClone.push_back(InitVal);
} else {
// Recursively add all operands.
for (const Operand &Op : Ops) {
add(cast<SILInstruction>(Op.get()));
}
}
}
SILInstruction *StaticInitCloner::clone(SILInstruction *InitVal) {
assert(NumOpsToClone.count(InitVal) != 0 && "InitVal was not added");
// Find the right order to clone: all operands of an instruction must be
// cloned before the instruction itself.
while (!ReadyToClone.empty()) {
SILInstruction *I = ReadyToClone.pop_back_val();
// Clone the instruction into the SILGlobalVariable
visit(I);
// Check if users of I can now be cloned.
for (Operand *Use : I->getUses()) {
SILInstruction *User = Use->getUser();
if (NumOpsToClone.count(User) != 0 && --NumOpsToClone[User] == 0)
ReadyToClone.push_back(User);
}
}
assert(InstructionMap.count(InitVal) != 0 &&
"Could not schedule all instructions for cloning");
return InstructionMap[InitVal];
}
} // end anonymous namespace
/// Replace loads from a global variable by the known value.
void SILGlobalOpt::
replaceLoadsByKnownValue(BuiltinInst *CallToOnce, SILFunction *AddrF,
SILFunction *InitF, SILGlobalVariable *SILG,
SILInstruction *InitVal,
GlobalInitCalls &Calls) {
assert(isAssignedOnlyOnceInInitializer(SILG) &&
"The value of the initializer should be known at compile-time");
assert(SILG->getDecl() &&
"Decl corresponding to the global variable should be known");
removeToken(CallToOnce->getOperand(0));
eraseUsesOfInstruction(CallToOnce);
recursivelyDeleteTriviallyDeadInstructions(CallToOnce, true);
// Make this addressor transparent.
AddrF->setTransparent(IsTransparent_t::IsTransparent);
for (int i = 0, e = Calls.size(); i < e; ++i) {
auto *Call = Calls[i];
SILBuilderWithScope B(Call);
SmallVector<SILValue, 1> Args;
auto *NewAI = B.createApply(Call->getLoc(), Call->getCallee(), Args, false);
Call->replaceAllUsesWith(NewAI);
eraseUsesOfInstruction(Call);
recursivelyDeleteTriviallyDeadInstructions(Call, true);
Calls[i] = NewAI;
}
// Generate a getter from InitF which returns the value of the global.
auto *GetterF = genGetterFromInit(InitF, SILG->getDecl());
// Replace all calls of an addressor by calls of a getter .
for (int i = 0, e = Calls.size(); i < e; ++i) {
auto *Call = Calls[i];
// Now find all uses of Call. They all should be loads, so that
// we can replace it.
bool isValid = true;
for (auto Use : Call->getUses()) {
if (!isa<PointerToAddressInst>(Use->getUser())) {
isValid = false;
break;
}
}
if (!isValid)
continue;
SILBuilderWithScope B(Call);
SmallVector<SILValue, 1> Args;
auto *GetterRef = B.createFunctionRef(Call->getLoc(), GetterF);
auto *NewAI = B.createApply(Call->getLoc(), GetterRef, Args, false);
for (auto Use : Call->getUses()) {
auto *PTAI = dyn_cast<PointerToAddressInst>(Use->getUser());
assert(PTAI && "All uses should be pointer_to_address");
for (auto PTAIUse : PTAI->getUses()) {
replaceLoadSequence(PTAIUse->getUser(), NewAI, B);
}
}
eraseUsesOfInstruction(Call);
recursivelyDeleteTriviallyDeadInstructions(Call, true);
}
Calls.clear();
StaticInitCloner::appendToInitializer(SILG, InitVal);
}
/// We analyze the body of globalinit_func to see if it can be statically
/// initialized. If yes, we set the initial value of the SILGlobalVariable and
/// remove the "once" call to globalinit_func from the addressor.
void SILGlobalOpt::optimizeInitializer(SILFunction *AddrF,
GlobalInitCalls &Calls) {
if (UnhandledOnceCallee)
return;
// Find the initializer and the SILGlobalVariable.
BuiltinInst *CallToOnce;
// If the addressor contains a single "once" call, it calls globalinit_func,
// and the globalinit_func is called by "once" from a single location,
// continue; otherwise bail.
auto *InitF = findInitializer(Module, AddrF, CallToOnce);
if (!InitF || !InitF->getName().startswith("globalinit_") ||
InitializerCount[InitF] > 1)
return;
// If the globalinit_func is trivial, continue; otherwise bail.
SILInstruction *InitVal;
SILGlobalVariable *SILG = getVariableOfStaticInitializer(InitF, InitVal);
if (!SILG)
return;
DEBUG(llvm::dbgs() << "GlobalOpt: use static initializer for " <<
SILG->getName() << '\n');
// Remove "once" call from the addressor.
if (!isAssignedOnlyOnceInInitializer(SILG) || !SILG->getDecl()) {
removeToken(CallToOnce->getOperand(0));
CallToOnce->eraseFromParent();
StaticInitCloner::appendToInitializer(SILG, InitVal);
HasChanged = true;
return;
}
replaceLoadsByKnownValue(CallToOnce, AddrF, InitF, SILG, InitVal, Calls);
HasChanged = true;
}
SILGlobalVariable *SILGlobalOpt::getVariableOfGlobalInit(SILFunction *AddrF) {
if (AddrF->isGlobalInit()) {
// If the addressor contains a single "once" call, it calls globalinit_func,
// and the globalinit_func is called by "once" from a single location,
// continue; otherwise bail.
BuiltinInst *CallToOnce;
auto *InitF = findInitializer(Module, AddrF, CallToOnce);
if (!InitF || !InitF->getName().startswith("globalinit_")
|| InitializerCount[InitF] > 1)
return nullptr;
// If the globalinit_func is trivial, continue; otherwise bail.
SILInstruction *dummyInitVal;
auto *SILG = getVariableOfStaticInitializer(InitF, dummyInitVal);
if (!SILG || !SILG->isDefinition())
return nullptr;
return SILG;
}
return nullptr;
}
static bool canBeChangedExternally(SILGlobalVariable *SILG) {
// Don't assume anything about globals which are imported from other modules.
if (isAvailableExternally(SILG->getLinkage()))
return true;
// Use access specifiers from the declarations,
// if possible.
if (auto *Decl = SILG->getDecl()) {
switch (Decl->getEffectiveAccess()) {
case AccessLevel::Private:
case AccessLevel::FilePrivate:
return false;
case AccessLevel::Internal:
return !SILG->getModule().isWholeModule();
case AccessLevel::Public:
case AccessLevel::Open:
return true;
}
}
if (SILG->getLinkage() == SILLinkage::Private)
return false;
if (SILG->getLinkage() == SILLinkage::Hidden
&& SILG->getModule().isWholeModule()) {
return false;
}
return true;
}
/// Check if instruction I is a load from instruction V or
/// or a struct_element_addr from instruction V.
/// returns instruction I if this condition holds, or nullptr otherwise.
static LoadInst *getValidLoad(SILInstruction *I, SILInstruction *V) {
if (auto *LI = dyn_cast<LoadInst>(I)) {
if (LI->getOperand() == V)
return LI;
}
if (auto *SEAI = dyn_cast<StructElementAddrInst>(I)) {
if (SEAI->getOperand() == V && SEAI->hasOneUse())
return getValidLoad(SEAI->use_begin()->getUser(), SEAI);
}
if (auto *TEAI = dyn_cast<TupleElementAddrInst>(I)) {
if (TEAI->getOperand() == V && TEAI->hasOneUse())
return getValidLoad(TEAI->use_begin()->getUser(), TEAI);
}
return nullptr;
}
/// If this is a read from a global let variable, map it.
void SILGlobalOpt::collectGlobalAccess(GlobalAddrInst *GAI) {
auto *SILG = GAI->getReferencedGlobal();
if (!SILG)
return;
if (!SILG->isLet()) {
// We cannot determine the value for global variables which could be
// changed externally at run-time.
if (canBeChangedExternally(SILG))
return;
}
if (GlobalVarSkipProcessing.count(SILG))
return;
if (!isSimpleType(SILG->getLoweredType(), *Module)) {
GlobalVarSkipProcessing.insert(SILG);
return;
}
// Ignore any accesses inside addressors for SILG
auto *F = GAI->getFunction();
auto GlobalVar = getVariableOfGlobalInit(F);
if (GlobalVar == SILG)
return;
if (!SILG->getDecl())
return;
SILValue V = GAI;
for (auto Use : getNonDebugUses(V)) {
if (auto *SI = dyn_cast<StoreInst>(Use->getUser())) {
if (SI->getDest() == GAI)
collectGlobalStore(SI, SILG);
continue;
}
if (auto *Load = getValidLoad(Use->getUser(), GAI)) {
collectGlobalLoad(Load, SILG);
continue;
}
// This global is not initialized by a simple
// constant value at this moment.
GlobalVarSkipProcessing.insert(SILG);
break;
}
}
/// Get all stored properties of a class, including it's super classes.
static void getFields(ClassDecl *Cl, SmallVectorImpl<VarDecl *> &Fields) {
if (ClassDecl *SuperCl = Cl->getSuperclassDecl()) {
getFields(SuperCl, Fields);
}
for (VarDecl *Field : Cl->getStoredProperties()) {
Fields.push_back(Field);
}
}
/// Check if \p V is a valid instruction for a static initializer, including
/// all it's operands.
static bool isValidInitVal(SILValue V) {
if (SILInstruction *I = dyn_cast<SILInstruction>(V)) {
if (!SILGlobalVariable::isValidStaticInitializerInst(I, I->getModule()))
return false;
for (Operand &Op : I->getAllOperands()) {
if (!isValidInitVal(Op.get()))
return false;
}
return true;
}
return false;
}
/// Check if \p V is an empty tuple or empty struct.
static bool isEmptyInitVal(SILValue V) {
if (!isa<StructInst>(V) && !isa<TupleInst>(V))
return false;
// If any of the operands is not empty, the whole struct/tuple is not empty.
for (Operand &Op : cast<SILInstruction>(V)->getAllOperands()) {
if (!isEmptyInitVal(Op.get()))
return false;
}
return true;
}
/// Check if a use of an object may prevent outlining the object.
///
/// If \p isCOWObject is true, then the object reference is wrapped into a
/// COW container. Currently this is just Array<T>.
/// If a use is a call to the findStringSwitchCase semantic call, the apply
/// is returned in \p FindStringCall.
bool SILGlobalOpt::isValidUseOfObject(SILInstruction *I, bool isCOWObject,
ApplyInst **FindStringCall) {
switch (I->getKind()) {
case ValueKind::DebugValueAddrInst:
case ValueKind::DebugValueInst:
case ValueKind::LoadInst:
case ValueKind::DeallocRefInst:
case ValueKind::StrongRetainInst:
case ValueKind::StrongReleaseInst:
return true;
case ValueKind::ReturnInst:
case ValueKind::TryApplyInst:
case ValueKind::PartialApplyInst:
case ValueKind::StoreInst:
/// We don't have a representation for COW objects in SIL, so we do some
/// ad-hoc testing: We can ignore uses of a COW object if any use after
/// this will do a uniqueness checking before the object is modified.
return isCOWObject;
case ValueKind::ApplyInst:
if (!isCOWObject)
return false;
// There should only be a single call to findStringSwitchCase. But even
// if there are multiple calls, it's not problem - we'll just optimize the
// last one we find.
if (cast<ApplyInst>(I)->hasSemantics("findStringSwitchCase"))
*FindStringCall = cast<ApplyInst>(I);
return true;
case ValueKind::StructInst:
if (isCOWType(I->getType())) {
// The object is wrapped into a COW container.
isCOWObject = true;
}
break;
case ValueKind::UncheckedRefCastInst:
case ValueKind::StructElementAddrInst:
case ValueKind::AddressToPointerInst:
assert(!isCOWObject && "instruction cannot have a COW object as operand");
break;
case ValueKind::TupleInst:
case ValueKind::TupleExtractInst:
case ValueKind::EnumInst:
break;
case ValueKind::StructExtractInst:
// To be on the safe side we don't consider the object as COW if it is
// extracted again from the COW container: the uniqueness check may be
// optimized away in this case.
isCOWObject = false;
break;
case ValueKind::BuiltinInst: {
// Handle the case for comparing addresses. This occurs when the Array
// comparison function is inlined.
auto *BI = cast<BuiltinInst>(I);
BuiltinValueKind K = BI->getBuiltinInfo().ID;
if (K == BuiltinValueKind::ICMP_EQ || K == BuiltinValueKind::ICMP_NE)
return true;
return false;
}
default:
return false;
}
for (Operand *Use : getNonDebugUses(I)) {
if (!isValidUseOfObject(Use->getUser(), isCOWObject, FindStringCall))
return false;
}
return true;
}
/// Handle the address of a tail element.
bool SILGlobalOpt::handleTailAddr(int TailIdx, SILInstruction *TailAddr,
llvm::SmallVectorImpl<StoreInst *> &TailStores) {
if (TailIdx >= 0 && TailIdx < (int)TailStores.size()) {
if (auto *SI = dyn_cast<StoreInst>(TailAddr)) {
if (!isValidInitVal(SI->getSrc()) || TailStores[TailIdx])
return false;
// We don't optimize arrays with an empty element type. This would
// generate a wrong initializer with zero-sized elements. But the stride
// of zero sized types is (artificially) set to 1 in IRGen.
if (isEmptyInitVal(SI->getSrc()))
return false;
TailStores[TailIdx] = SI;
return true;
}
}
return isValidUseOfObject(TailAddr, /*isCOWObject*/false);
}
/// Get the init values for an object's stored properties and its tail elements.
bool SILGlobalOpt::getObjectInitVals(SILValue Val,
llvm::DenseMap<VarDecl *, StoreInst *> &MemberStores,
llvm::SmallVectorImpl<StoreInst *> &TailStores,
ApplyInst **FindStringCall) {
for (Operand *Use : Val->getUses()) {
SILInstruction *User = Use->getUser();
if (auto *UC = dyn_cast<UpcastInst>(User)) {
// Upcast is transparent.
if (!getObjectInitVals(UC, MemberStores, TailStores, FindStringCall))
return false;
} else if (auto *REA = dyn_cast<RefElementAddrInst>(User)) {
// The address of a stored property.
for (Operand *ElemAddrUse : REA->getUses()) {
SILInstruction *ElemAddrUser = ElemAddrUse->getUser();
if (auto *SI = dyn_cast<StoreInst>(ElemAddrUser)) {
if (!isValidInitVal(SI->getSrc()) || MemberStores[REA->getField()])
return false;
MemberStores[REA->getField()] = SI;
} else if (!isValidUseOfObject(ElemAddrUser, /*isCOWObject*/false)) {
return false;
}
}
} else if (auto *RTA = dyn_cast<RefTailAddrInst>(User)) {
// The address of a tail element.
for (Operand *TailUse : RTA->getUses()) {
SILInstruction *TailUser = TailUse->getUser();
if (auto *IA = dyn_cast<IndexAddrInst>(TailUser)) {
// An index_addr yields the address of any tail element. Only if the
// second operand (the index) is an integer literal we can figure out
// which tail element is refereneced.
int TailIdx = -1;
if (auto *Index = dyn_cast<IntegerLiteralInst>(IA->getIndex()))
TailIdx = Index->getValue().getZExtValue();
for (Operand *IAUse : IA->getUses()) {
if (!handleTailAddr(TailIdx, IAUse->getUser(), TailStores))
return false;
}
// Without an index_addr it's the first tail element.
} else if (!handleTailAddr(/*TailIdx*/0, TailUser, TailStores)) {
return false;
}
}
} else if (!isValidUseOfObject(User, /*isCOWObject*/false, FindStringCall)) {
return false;
}
}
return true;
}
class GlobalVariableMangler : public Mangle::ASTMangler {
public:
std::string mangleOutlinedVariable(SILFunction *F, int &uniqueIdx) {
std::string GlobName;
do {
beginManglingWithoutPrefix();
appendOperator(F->getName());
appendOperator("Tv", Index(uniqueIdx++));
GlobName = finalize();
} while (F->getModule().lookUpGlobalVariable(GlobName));
return GlobName;
}
};
/// Try to convert an object allocation into a statically initialized object.
///
/// In general this works for any class, but in practice it will only kick in
/// for array buffer objects. The use cases are array literals in a function.
/// For example:
/// func getarray() -> [Int] {
/// return [1, 2, 3]
/// }
void SILGlobalOpt::optimizeObjectAllocation(AllocRefInst *ARI) {
if (ARI->isObjC())
return;
// Check how many tail allocated elements are on the object.
ArrayRef<Operand> TailCounts = ARI->getTailAllocatedCounts();
SILType TailType;
unsigned NumTailElems = 0;
if (TailCounts.size() > 0) {
// We only support a single tail allocated array.
if (TailCounts.size() > 1)
return;
// The number of tail allocated elements must be constant.
if (auto *ILI = dyn_cast<IntegerLiteralInst>(TailCounts[0].get())) {
if (ILI->getValue().getActiveBits() > 20)
return;
NumTailElems = ILI->getValue().getZExtValue();
TailType = ARI->getTailAllocatedTypes()[0];
} else {
return;
}
}
SILType Ty = ARI->getType();
ClassDecl *Cl = Ty.getClassOrBoundGenericClass();
if (!Cl)
return;
llvm::SmallVector<VarDecl *, 16> Fields;
getFields(Cl, Fields);
// Get the initialization stores of the object's properties and tail
// allocated elements. Also check if there are any "bad" uses of the object.
llvm::DenseMap<VarDecl *, StoreInst *> MemberStores;
llvm::SmallVector<StoreInst *, 16> TailStores;
TailStores.resize(NumTailElems);
ApplyInst *FindStringCall = nullptr;
if (!getObjectInitVals(ARI, MemberStores, TailStores, &FindStringCall))
return;
// Is there a store for all the class properties?
if (MemberStores.size() != Fields.size())
return;
// Is there a store for all tail allocated elements?
for (SILValue V : TailStores) {
if (!V)
return;
}
DEBUG(llvm::dbgs() << "Outline global variable in " <<
ARI->getFunction()->getName() << '\n');
// Create a name for the outlined global variable.
GlobalVariableMangler Mangler;
std::string GlobName =
Mangler.mangleOutlinedVariable(ARI->getFunction(), GlobIdx);
SILGlobalVariable *Glob =
SILGlobalVariable::create(*Module, SILLinkage::Private, IsNotSerialized,
GlobName, ARI->getType());
// Schedule all init values for cloning into the initializer of Glob.
StaticInitCloner Cloner(Glob);
for (VarDecl *Field : Fields) {
StoreInst *MemberStore = MemberStores[Field];
Cloner.add(cast<SILInstruction>(MemberStore->getSrc()));
}
for (StoreInst *TailStore : TailStores) {
Cloner.add(cast<SILInstruction>(TailStore->getSrc()));
}
// Create the class property initializers
llvm::SmallVector<SILValue, 16> ObjectArgs;
for (VarDecl *Field : Fields) {
StoreInst *MemberStore = MemberStores[Field];
assert(MemberStore);
ObjectArgs.push_back(Cloner.clone(
cast<SILInstruction>(MemberStore->getSrc())));
MemberStore->eraseFromParent();
}
// Create the initializers for the tail elements.
unsigned NumBaseElements = ObjectArgs.size();
for (StoreInst *TailStore : TailStores) {
ObjectArgs.push_back(Cloner.clone(
cast<SILInstruction>(TailStore->getSrc())));
TailStore->eraseFromParent();
}
// Create the initializer for the object itself.
SILBuilder StaticInitBuilder(Glob);
StaticInitBuilder.createObject(ArtificialUnreachableLocation(),
ARI->getType(), ObjectArgs, NumBaseElements);
// Replace the alloc_ref by global_value + strong_retain instructions.
SILBuilder B(ARI);
GlobalValueInst *GVI = B.createGlobalValue(ARI->getLoc(), Glob);
B.createStrongRetain(ARI->getLoc(), GVI, B.getDefaultAtomicity());
while (!ARI->use_empty()) {
Operand *Use = *ARI->use_begin();
SILInstruction *User = Use->getUser();
switch (User->getKind()) {
case ValueKind::DeallocRefInst:
User->eraseFromParent();
break;
default:
Use->set(GVI);
}
}
if (FindStringCall && NumTailElems > 16) {
assert(&*std::next(ARI->getIterator()) != FindStringCall &&
"FindStringCall must not be the next instruction after ARI because "
"deleting it would invalidate the instruction iterator");
replaceFindStringCall(FindStringCall);
}
ARI->eraseFromParent();
HasChanged = true;
}
/// Replaces a call to _findStringSwitchCase with a call to
/// _findStringSwitchCaseWithCache which builds a cache (e.g. a Dictionary) and
/// stores it into a global variable. Then subsequent calls to this function can
/// do a fast lookup using the cache.
void SILGlobalOpt::replaceFindStringCall(ApplyInst *FindStringCall) {
// Find the replacement function in the swift stdlib.
SmallVector<ValueDecl *, 1> results;
Module->getASTContext().lookupInSwiftModule("_findStringSwitchCaseWithCache",
results);
if (results.size() != 1)
return;
auto *FD = dyn_cast<FuncDecl>(results.front());
if (!FD)
return;
std::string Mangled = SILDeclRef(FD, SILDeclRef::Kind::Func).mangle();
SILFunction *replacementFunc = Module->findFunction(Mangled,
SILLinkage::PublicExternal);
if (!replacementFunc)
return;
SILFunctionType *FTy = replacementFunc->getLoweredFunctionType();
if (FTy->getNumParameters() != 3)
return;
SILType cacheType = FTy->getParameters()[2].getSILStorageType().getObjectType();
NominalTypeDecl *cacheDecl = cacheType.getNominalOrBoundGenericNominal();
if (!cacheDecl)
return;
SILType wordTy = cacheType.getFieldType(
cacheDecl->getStoredProperties().front(), *Module);
GlobalVariableMangler Mangler;
std::string GlobName =
Mangler.mangleOutlinedVariable(FindStringCall->getFunction(), GlobIdx);
// Create an "opaque" global variable which is passed as inout to
// _findStringSwitchCaseWithCache and into which the function stores the
// "cache".
SILGlobalVariable *CacheVar =
SILGlobalVariable::create(*Module, SILLinkage::Private, IsNotSerialized,
GlobName, cacheType);
SILLocation Loc = FindStringCall->getLoc();
SILBuilder StaticInitBuilder(CacheVar);
auto *Zero = StaticInitBuilder.createIntegerLiteral(Loc, wordTy, 0);
StaticInitBuilder.createStruct(ArtificialUnreachableLocation(), cacheType,
{Zero, Zero});
SILBuilder B(FindStringCall);
GlobalAddrInst *CacheAddr = B.createGlobalAddr(FindStringCall->getLoc(),
CacheVar);
FunctionRefInst *FRI = B.createFunctionRef(FindStringCall->getLoc(),
replacementFunc);
ApplyInst *NewCall = B.createApply(FindStringCall->getLoc(), FRI,
FindStringCall->getSubstitutions(),
{ FindStringCall->getArgument(0),
FindStringCall->getArgument(1),
CacheAddr },
FindStringCall->isNonThrowing());
FindStringCall->replaceAllUsesWith(NewCall);
FindStringCall->eraseFromParent();
}
/// Optimize access to the global variable, which is known
/// to have a constant value. Replace all loads from the
/// global address by invocations of a getter that returns
/// the value of this variable.
void SILGlobalOpt::optimizeGlobalAccess(SILGlobalVariable *SILG,
StoreInst *SI) {
DEBUG(llvm::dbgs() << "GlobalOpt: use static initializer for " <<
SILG->getName() << '\n');
if (GlobalVarSkipProcessing.count(SILG))
return;
if (//!isAssignedOnlyOnceInInitializer(SILG) ||
!SILG->getDecl()) {
return;
}
if (!GlobalLoadMap.count(SILG))
return;
// Generate a getter only if there are any loads from this variable.
SILFunction *GetterF = genGetterFromInit(SI, SILG);
if (!GetterF)
return;
// Iterate over all loads and replace them by values.
// TODO: In principle, we could invoke the getter only once
// inside each function that loads from the global. This
// invocation should happen at the common dominator of all
// loads inside this function.
for (auto *Load: GlobalLoadMap[SILG]) {
SILBuilderWithScope B(Load);
auto *GetterRef = B.createFunctionRef(Load->getLoc(), GetterF);
auto *Value = B.createApply(Load->getLoc(), GetterRef, {}, false);
convertLoadSequence(Load, Value, B);
HasChanged = true;
}
}
bool SILGlobalOpt::run() {
for (auto &F : *Module) {
// Don't optimize functions that are marked with the opt.never attribute.
if (!F.shouldOptimize())
continue;
// Cache cold blocks per function.
ColdBlockInfo ColdBlocks(DA);
GlobIdx = 0;
for (auto &BB : F) {
bool IsCold = ColdBlocks.isCold(&BB);
auto Iter = BB.begin();
while (Iter != BB.end()) {
SILInstruction *I = &*Iter;
Iter++;
if (auto *BI = dyn_cast<BuiltinInst>(I)) {
collectOnceCall(BI);
} else if (auto *AI = dyn_cast<ApplyInst>(I)) {
if (!IsCold)
collectGlobalInitCall(AI);
} else if (auto *GAI = dyn_cast<GlobalAddrInst>(I)) {
collectGlobalAccess(GAI);
} else if (auto *ARI = dyn_cast<AllocRefInst>(I)) {
if (!F.isSerialized()) {
// Currently we cannot serialize a function which refers to a
// statically initialized global. So we don't do the optimization
// for serializable functions.
// TODO: We may do the optimization _after_ serialization in the
// pass pipeline.
optimizeObjectAllocation(ARI);
}
}
}
}
}
for (auto &InitCalls : GlobalInitCallMap) {
// Optimize the addressors if possible.
optimizeInitializer(InitCalls.first, InitCalls.second);
placeInitializers(InitCalls.first, InitCalls.second);
}
for (auto &Init : GlobalVarStore) {
// Optimize the access to globals if possible.
optimizeGlobalAccess(Init.first, Init.second);
}
return HasChanged;
}
namespace {
class SILGlobalOptPass : public SILModuleTransform
{
void run() override {
DominanceAnalysis *DA = PM->getAnalysis<DominanceAnalysis>();
if (SILGlobalOpt(getModule(), DA).run()) {
invalidateAll();
}
}
};
} // end anonymous namespace
SILTransform *swift::createGlobalOpt() {
return new SILGlobalOptPass();
}