bool EliminateAvailableExternally::runOnModule(Module &M) {
bool Changed = false;
// Drop initializers of available externally global variables.
for (GlobalVariable &GV : M.globals()) {
if (!GV.hasAvailableExternallyLinkage())
continue;
if (GV.hasInitializer()) {
Constant *Init = GV.getInitializer();
GV.setInitializer(nullptr);
if (isSafeToDestroyConstant(Init))
Init->destroyConstant();
}
GV.removeDeadConstantUsers();
GV.setLinkage(GlobalValue::ExternalLinkage);
NumVariables++;
Changed = true;
}
// Drop the bodies of available externally functions.
for (Function &F : M) {
if (!F.hasAvailableExternallyLinkage())
continue;
if (!F.isDeclaration())
// This will set the linkage to external
F.deleteBody();
F.removeDeadConstantUsers();
NumFunctions++;
Changed = true;
}
return Changed;
}
bool EliminateAvailableExternally::runOnModule(Module &M) {
bool Changed = false;
// Convert any aliases that alias with an available externally
// value (which will be turned into declarations later on in this routine)
// into declarations themselves. All aliases must be definitions, and
// must alias with a definition. So this involves creating a declaration
// equivalent to the alias's base object.
for (Module::alias_iterator I = M.alias_begin(), E = M.alias_end(); I != E;) {
// Increment the iterator first since we may delete the current alias.
GlobalAlias &GA = *(I++);
GlobalValue *GVal = GA.getBaseObject();
if (!GVal->hasAvailableExternallyLinkage())
continue;
convertAliasToDeclaration(GA, M);
Changed = true;
}
// Drop initializers of available externally global variables.
for (GlobalVariable &GV : M.globals()) {
if (!GV.hasAvailableExternallyLinkage())
continue;
if (GV.hasInitializer()) {
Constant *Init = GV.getInitializer();
GV.setInitializer(nullptr);
if (isSafeToDestroyConstant(Init))
Init->destroyConstant();
}
GV.removeDeadConstantUsers();
GV.setLinkage(GlobalValue::ExternalLinkage);
NumVariables++;
Changed = true;
}
// Drop the bodies of available externally functions.
for (Function &F : M) {
if (!F.hasAvailableExternallyLinkage())
continue;
if (!F.isDeclaration())
// This will set the linkage to external
F.deleteBody();
F.removeDeadConstantUsers();
NumFunctions++;
Changed = true;
}
return Changed;
}
static int runCompilePasses(Module *ModuleRef,
unsigned ModuleIndex,
ThreadedFunctionQueue *FuncQueue,
const Triple &TheTriple,
TargetMachine &Target,
StringRef ProgramName,
raw_pwrite_stream &OS){
PNaClABIErrorReporter ABIErrorReporter;
if (SplitModuleCount > 1 || ExternalizeAll) {
// Add function and global names, and give them external linkage.
// This relies on LLVM's consistent auto-generation of names, we could
// maybe do our own in case something changes there.
for (Function &F : *ModuleRef) {
if (!F.hasName())
F.setName("Function");
if (F.hasInternalLinkage())
F.setLinkage(GlobalValue::ExternalLinkage);
}
for (Module::global_iterator GI = ModuleRef->global_begin(),
GE = ModuleRef->global_end();
GI != GE; ++GI) {
if (!GI->hasName())
GI->setName("Global");
if (GI->hasInternalLinkage())
GI->setLinkage(GlobalValue::ExternalLinkage);
}
if (ModuleIndex > 0) {
// Remove the initializers for all global variables, turning them into
// declarations.
for (Module::global_iterator GI = ModuleRef->global_begin(),
GE = ModuleRef->global_end();
GI != GE; ++GI) {
assert(GI->hasInitializer() && "Global variable missing initializer");
Constant *Init = GI->getInitializer();
GI->setInitializer(nullptr);
if (Init->getNumUses() == 0)
Init->destroyConstant();
}
}
}
// Make all non-weak symbols hidden for better code. We cannot do
// this for weak symbols. The linker complains when some weak
// symbols are not resolved.
for (Function &F : *ModuleRef) {
if (!F.isWeakForLinker() && !F.hasLocalLinkage())
F.setVisibility(GlobalValue::HiddenVisibility);
}
for (Module::global_iterator GI = ModuleRef->global_begin(),
GE = ModuleRef->global_end();
GI != GE; ++GI) {
if (!GI->isWeakForLinker() && !GI->hasLocalLinkage())
GI->setVisibility(GlobalValue::HiddenVisibility);
}
// Build up all of the passes that we want to do to the module.
std::unique_ptr<legacy::PassManagerBase> PM;
if (LazyBitcode)
PM.reset(new legacy::FunctionPassManager(ModuleRef));
else
PM.reset(new legacy::PassManager());
// Add the target data from the target machine, if it exists, or the module.
if (const DataLayout *DL = Target.getDataLayout())
ModuleRef->setDataLayout(*DL);
// For conformance with llc, we let the user disable LLVM IR verification with
// -disable-verify. Unlike llc, when LLVM IR verification is enabled we only
// run it once, before PNaCl ABI verification.
if (!NoVerify)
PM->add(createVerifierPass());
// Add the ABI verifier pass before the analysis and code emission passes.
if (PNaClABIVerify)
PM->add(createPNaClABIVerifyFunctionsPass(&ABIErrorReporter));
// Add the intrinsic resolution pass. It assumes ABI-conformant code.
PM->add(createResolvePNaClIntrinsicsPass());
// Add an appropriate TargetLibraryInfo pass for the module's triple.
TargetLibraryInfoImpl TLII(TheTriple);
// The -disable-simplify-libcalls flag actually disables all builtin optzns.
if (DisableSimplifyLibCalls)
TLII.disableAllFunctions();
PM->add(new TargetLibraryInfoWrapperPass(TLII));
// Allow subsequent passes and the backend to better optimize instructions
// that were simplified for PNaCl's ABI. This pass uses the TargetLibraryInfo
// above.
PM->add(createBackendCanonicalizePass());
// Ask the target to add backend passes as necessary. We explicitly ask it
// not to add the verifier pass because we added it earlier.
if (Target.addPassesToEmitFile(*PM, OS, FileType,
/* DisableVerify */ true)) {
errs() << ProgramName
<< ": target does not support generation of this file type!\n";
return 1;
}
if (LazyBitcode) {
auto FPM = static_cast<legacy::FunctionPassManager *>(PM.get());
FPM->doInitialization();
unsigned FuncIndex = 0;
switch (SplitModuleSched) {
case SplitModuleStatic:
for (Function &F : *ModuleRef) {
if (FuncQueue->GrabFunctionStatic(FuncIndex, ModuleIndex)) {
FPM->run(F);
CheckABIVerifyErrors(ABIErrorReporter, "Function " + F.getName());
F.Dematerialize();
}
++FuncIndex;
}
break;
case SplitModuleDynamic:
unsigned ChunkSize = 0;
unsigned NumFunctions = FuncQueue->Size();
Module::iterator I = ModuleRef->begin();
while (FuncIndex < NumFunctions) {
ChunkSize = FuncQueue->RecommendedChunkSize();
unsigned NextIndex;
bool grabbed = FuncQueue->GrabFunctionDynamic(FuncIndex, ChunkSize,
NextIndex);
if (grabbed) {
while (FuncIndex < NextIndex) {
if (!I->isMaterializable() && I->isDeclaration()) {
++I;
continue;
}
FPM->run(*I);
CheckABIVerifyErrors(ABIErrorReporter, "Function " + I->getName());
I->Dematerialize();
++FuncIndex;
++I;
}
} else {
while (FuncIndex < NextIndex) {
if (!I->isMaterializable() && I->isDeclaration()) {
++I;
continue;
}
++FuncIndex;
++I;
}
}
}
break;
}
FPM->doFinalization();
} else
static_cast<legacy::PassManager *>(PM.get())->run(*ModuleRef);
return 0;
}
PreservedAnalyses GlobalDCEPass::run(Module &M, ModuleAnalysisManager &) {
bool Changed = false;
// Remove empty functions from the global ctors list.
Changed |= optimizeGlobalCtorsList(M, isEmptyFunction);
// Collect the set of members for each comdat.
for (Function &F : M)
if (Comdat *C = F.getComdat())
ComdatMembers.insert(std::make_pair(C, &F));
for (GlobalVariable &GV : M.globals())
if (Comdat *C = GV.getComdat())
ComdatMembers.insert(std::make_pair(C, &GV));
for (GlobalAlias &GA : M.aliases())
if (Comdat *C = GA.getComdat())
ComdatMembers.insert(std::make_pair(C, &GA));
// Loop over the module, adding globals which are obviously necessary.
for (GlobalObject &GO : M.global_objects()) {
Changed |= RemoveUnusedGlobalValue(GO);
// Functions with external linkage are needed if they have a body.
// Externally visible & appending globals are needed, if they have an
// initializer.
if (!GO.isDeclaration() && !GO.hasAvailableExternallyLinkage())
if (!GO.isDiscardableIfUnused())
GlobalIsNeeded(&GO);
}
for (GlobalAlias &GA : M.aliases()) {
Changed |= RemoveUnusedGlobalValue(GA);
// Externally visible aliases are needed.
if (!GA.isDiscardableIfUnused())
GlobalIsNeeded(&GA);
}
for (GlobalIFunc &GIF : M.ifuncs()) {
Changed |= RemoveUnusedGlobalValue(GIF);
// Externally visible ifuncs are needed.
if (!GIF.isDiscardableIfUnused())
GlobalIsNeeded(&GIF);
}
// Now that all globals which are needed are in the AliveGlobals set, we loop
// through the program, deleting those which are not alive.
//
// The first pass is to drop initializers of global variables which are dead.
std::vector<GlobalVariable *> DeadGlobalVars; // Keep track of dead globals
for (GlobalVariable &GV : M.globals())
if (!AliveGlobals.count(&GV)) {
DeadGlobalVars.push_back(&GV); // Keep track of dead globals
if (GV.hasInitializer()) {
Constant *Init = GV.getInitializer();
GV.setInitializer(nullptr);
if (isSafeToDestroyConstant(Init))
Init->destroyConstant();
}
}
// The second pass drops the bodies of functions which are dead...
std::vector<Function *> DeadFunctions;
for (Function &F : M)
if (!AliveGlobals.count(&F)) {
DeadFunctions.push_back(&F); // Keep track of dead globals
if (!F.isDeclaration())
F.deleteBody();
}
// The third pass drops targets of aliases which are dead...
std::vector<GlobalAlias*> DeadAliases;
for (GlobalAlias &GA : M.aliases())
if (!AliveGlobals.count(&GA)) {
DeadAliases.push_back(&GA);
GA.setAliasee(nullptr);
}
// The third pass drops targets of ifuncs which are dead...
std::vector<GlobalIFunc*> DeadIFuncs;
for (GlobalIFunc &GIF : M.ifuncs())
if (!AliveGlobals.count(&GIF)) {
DeadIFuncs.push_back(&GIF);
GIF.setResolver(nullptr);
}
// Now that all interferences have been dropped, delete the actual objects
// themselves.
auto EraseUnusedGlobalValue = [&](GlobalValue *GV) {
RemoveUnusedGlobalValue(*GV);
GV->eraseFromParent();
Changed = true;
};
NumFunctions += DeadFunctions.size();
for (Function *F : DeadFunctions)
EraseUnusedGlobalValue(F);
NumVariables += DeadGlobalVars.size();
for (GlobalVariable *GV : DeadGlobalVars)
EraseUnusedGlobalValue(GV);
NumAliases += DeadAliases.size();
for (GlobalAlias *GA : DeadAliases)
EraseUnusedGlobalValue(GA);
NumIFuncs += DeadIFuncs.size();
for (GlobalIFunc *GIF : DeadIFuncs)
EraseUnusedGlobalValue(GIF);
// Make sure that all memory is released
AliveGlobals.clear();
SeenConstants.clear();
ComdatMembers.clear();
if (Changed)
return PreservedAnalyses::none();
return PreservedAnalyses::all();
}
bool GlobalDCE::runOnModule(Module &M) {
bool Changed = false;
// Remove empty functions from the global ctors list.
Changed |= optimizeGlobalCtorsList(M, isEmptyFunction);
// Loop over the module, adding globals which are obviously necessary.
for (Module::iterator I = M.begin(), E = M.end(); I != E; ++I) {
Changed |= RemoveUnusedGlobalValue(*I);
// Functions with external linkage are needed if they have a body
if (!I->isDeclaration() && !I->hasAvailableExternallyLinkage()) {
if (!I->isDiscardableIfUnused())
GlobalIsNeeded(I);
}
}
for (Module::global_iterator I = M.global_begin(), E = M.global_end();
I != E; ++I) {
Changed |= RemoveUnusedGlobalValue(*I);
// Externally visible & appending globals are needed, if they have an
// initializer.
if (!I->isDeclaration() && !I->hasAvailableExternallyLinkage()) {
if (!I->isDiscardableIfUnused())
GlobalIsNeeded(I);
}
}
for (Module::alias_iterator I = M.alias_begin(), E = M.alias_end();
I != E; ++I) {
Changed |= RemoveUnusedGlobalValue(*I);
// Externally visible aliases are needed.
if (!I->isDiscardableIfUnused()) {
GlobalIsNeeded(I);
}
}
// Now that all globals which are needed are in the AliveGlobals set, we loop
// through the program, deleting those which are not alive.
//
// The first pass is to drop initializers of global variables which are dead.
std::vector<GlobalVariable*> DeadGlobalVars; // Keep track of dead globals
for (Module::global_iterator I = M.global_begin(), E = M.global_end();
I != E; ++I)
if (!AliveGlobals.count(I)) {
DeadGlobalVars.push_back(I); // Keep track of dead globals
if (I->hasInitializer()) {
Constant *Init = I->getInitializer();
I->setInitializer(nullptr);
if (isSafeToDestroyConstant(Init))
Init->destroyConstant();
}
}
// The second pass drops the bodies of functions which are dead...
std::vector<Function*> DeadFunctions;
for (Module::iterator I = M.begin(), E = M.end(); I != E; ++I)
if (!AliveGlobals.count(I)) {
DeadFunctions.push_back(I); // Keep track of dead globals
if (!I->isDeclaration())
I->deleteBody();
}
// The third pass drops targets of aliases which are dead...
std::vector<GlobalAlias*> DeadAliases;
for (Module::alias_iterator I = M.alias_begin(), E = M.alias_end(); I != E;
++I)
if (!AliveGlobals.count(I)) {
DeadAliases.push_back(I);
I->setAliasee(nullptr);
}
if (!DeadFunctions.empty()) {
// Now that all interferences have been dropped, delete the actual objects
// themselves.
for (unsigned i = 0, e = DeadFunctions.size(); i != e; ++i) {
RemoveUnusedGlobalValue(*DeadFunctions[i]);
M.getFunctionList().erase(DeadFunctions[i]);
}
NumFunctions += DeadFunctions.size();
Changed = true;
}
if (!DeadGlobalVars.empty()) {
for (unsigned i = 0, e = DeadGlobalVars.size(); i != e; ++i) {
RemoveUnusedGlobalValue(*DeadGlobalVars[i]);
M.getGlobalList().erase(DeadGlobalVars[i]);
}
NumVariables += DeadGlobalVars.size();
Changed = true;
}
// Now delete any dead aliases.
if (!DeadAliases.empty()) {
for (unsigned i = 0, e = DeadAliases.size(); i != e; ++i) {
RemoveUnusedGlobalValue(*DeadAliases[i]);
M.getAliasList().erase(DeadAliases[i]);
}
NumAliases += DeadAliases.size();
Changed = true;
}
// Make sure that all memory is released
AliveGlobals.clear();
SeenConstants.clear();
return Changed;
}
PreservedAnalyses GlobalDCEPass::run(Module &M, ModuleAnalysisManager &MAM) {
bool Changed = false;
// The algorithm first computes the set L of global variables that are
// trivially live. Then it walks the initialization of these variables to
// compute the globals used to initialize them, which effectively builds a
// directed graph where nodes are global variables, and an edge from A to B
// means B is used to initialize A. Finally, it propagates the liveness
// information through the graph starting from the nodes in L. Nodes note
// marked as alive are discarded.
// Remove empty functions from the global ctors list.
Changed |= optimizeGlobalCtorsList(M, isEmptyFunction);
// Collect the set of members for each comdat.
for (Function &F : M)
if (Comdat *C = F.getComdat())
ComdatMembers.insert(std::make_pair(C, &F));
for (GlobalVariable &GV : M.globals())
if (Comdat *C = GV.getComdat())
ComdatMembers.insert(std::make_pair(C, &GV));
for (GlobalAlias &GA : M.aliases())
if (Comdat *C = GA.getComdat())
ComdatMembers.insert(std::make_pair(C, &GA));
// Loop over the module, adding globals which are obviously necessary.
for (GlobalObject &GO : M.global_objects()) {
Changed |= RemoveUnusedGlobalValue(GO);
// Functions with external linkage are needed if they have a body.
// Externally visible & appending globals are needed, if they have an
// initializer.
if (!GO.isDeclaration() && !GO.hasAvailableExternallyLinkage())
if (!GO.isDiscardableIfUnused())
MarkLive(GO);
UpdateGVDependencies(GO);
}
// Compute direct dependencies of aliases.
for (GlobalAlias &GA : M.aliases()) {
Changed |= RemoveUnusedGlobalValue(GA);
// Externally visible aliases are needed.
if (!GA.isDiscardableIfUnused())
MarkLive(GA);
UpdateGVDependencies(GA);
}
// Compute direct dependencies of ifuncs.
for (GlobalIFunc &GIF : M.ifuncs()) {
Changed |= RemoveUnusedGlobalValue(GIF);
// Externally visible ifuncs are needed.
if (!GIF.isDiscardableIfUnused())
MarkLive(GIF);
UpdateGVDependencies(GIF);
}
// Propagate liveness from collected Global Values through the computed
// dependencies.
SmallVector<GlobalValue *, 8> NewLiveGVs{AliveGlobals.begin(),
AliveGlobals.end()};
while (!NewLiveGVs.empty()) {
GlobalValue *LGV = NewLiveGVs.pop_back_val();
for (auto &&GVD : make_range(GVDependencies.equal_range(LGV)))
MarkLive(*GVD.second, &NewLiveGVs);
}
// Now that all globals which are needed are in the AliveGlobals set, we loop
// through the program, deleting those which are not alive.
//
// The first pass is to drop initializers of global variables which are dead.
std::vector<GlobalVariable *> DeadGlobalVars; // Keep track of dead globals
for (GlobalVariable &GV : M.globals())
if (!AliveGlobals.count(&GV)) {
DeadGlobalVars.push_back(&GV); // Keep track of dead globals
if (GV.hasInitializer()) {
Constant *Init = GV.getInitializer();
GV.setInitializer(nullptr);
if (isSafeToDestroyConstant(Init))
Init->destroyConstant();
}
}
// The second pass drops the bodies of functions which are dead...
std::vector<Function *> DeadFunctions;
for (Function &F : M)
if (!AliveGlobals.count(&F)) {
DeadFunctions.push_back(&F); // Keep track of dead globals
if (!F.isDeclaration())
F.deleteBody();
}
// The third pass drops targets of aliases which are dead...
std::vector<GlobalAlias*> DeadAliases;
for (GlobalAlias &GA : M.aliases())
if (!AliveGlobals.count(&GA)) {
DeadAliases.push_back(&GA);
GA.setAliasee(nullptr);
}
// The fourth pass drops targets of ifuncs which are dead...
std::vector<GlobalIFunc*> DeadIFuncs;
for (GlobalIFunc &GIF : M.ifuncs())
if (!AliveGlobals.count(&GIF)) {
DeadIFuncs.push_back(&GIF);
GIF.setResolver(nullptr);
}
// Now that all interferences have been dropped, delete the actual objects
// themselves.
auto EraseUnusedGlobalValue = [&](GlobalValue *GV) {
RemoveUnusedGlobalValue(*GV);
GV->eraseFromParent();
Changed = true;
};
NumFunctions += DeadFunctions.size();
for (Function *F : DeadFunctions)
EraseUnusedGlobalValue(F);
NumVariables += DeadGlobalVars.size();
for (GlobalVariable *GV : DeadGlobalVars)
EraseUnusedGlobalValue(GV);
NumAliases += DeadAliases.size();
for (GlobalAlias *GA : DeadAliases)
EraseUnusedGlobalValue(GA);
NumIFuncs += DeadIFuncs.size();
for (GlobalIFunc *GIF : DeadIFuncs)
EraseUnusedGlobalValue(GIF);
// Make sure that all memory is released
AliveGlobals.clear();
ConstantDependenciesCache.clear();
GVDependencies.clear();
ComdatMembers.clear();
if (Changed)
return PreservedAnalyses::none();
return PreservedAnalyses::all();
}
/// Once all constants are read, this method bulk resolves any forward
/// references. The idea behind this is that we sometimes get constants (such
/// as large arrays) which reference *many* forward ref constants. Replacing
/// each of these causes a lot of thrashing when building/reuniquing the
/// constant. Instead of doing this, we look at all the uses and rewrite all
/// the place holders at once for any constant that uses a placeholder.
void BitcodeReaderValueList::resolveConstantForwardRefs() {
// Sort the values by-pointer so that they are efficient to look up with a
// binary search.
llvm::sort(ResolveConstants);
SmallVector<Constant *, 64> NewOps;
while (!ResolveConstants.empty()) {
Value *RealVal = operator[](ResolveConstants.back().second);
Constant *Placeholder = ResolveConstants.back().first;
ResolveConstants.pop_back();
// Loop over all users of the placeholder, updating them to reference the
// new value. If they reference more than one placeholder, update them all
// at once.
while (!Placeholder->use_empty()) {
auto UI = Placeholder->user_begin();
User *U = *UI;
// If the using object isn't uniqued, just update the operands. This
// handles instructions and initializers for global variables.
if (!isa<Constant>(U) || isa<GlobalValue>(U)) {
UI.getUse().set(RealVal);
continue;
}
// Otherwise, we have a constant that uses the placeholder. Replace that
// constant with a new constant that has *all* placeholder uses updated.
Constant *UserC = cast<Constant>(U);
for (User::op_iterator I = UserC->op_begin(), E = UserC->op_end(); I != E;
++I) {
Value *NewOp;
if (!isa<ConstantPlaceHolder>(*I)) {
// Not a placeholder reference.
NewOp = *I;
} else if (*I == Placeholder) {
// Common case is that it just references this one placeholder.
NewOp = RealVal;
} else {
// Otherwise, look up the placeholder in ResolveConstants.
ResolveConstantsTy::iterator It = llvm::lower_bound(
ResolveConstants,
std::pair<Constant *, unsigned>(cast<Constant>(*I), 0));
assert(It != ResolveConstants.end() && It->first == *I);
NewOp = operator[](It->second);
}
NewOps.push_back(cast<Constant>(NewOp));
}
// Make the new constant.
Constant *NewC;
if (ConstantArray *UserCA = dyn_cast<ConstantArray>(UserC)) {
NewC = ConstantArray::get(UserCA->getType(), NewOps);
} else if (ConstantStruct *UserCS = dyn_cast<ConstantStruct>(UserC)) {
NewC = ConstantStruct::get(UserCS->getType(), NewOps);
} else if (isa<ConstantVector>(UserC)) {
NewC = ConstantVector::get(NewOps);
} else {
assert(isa<ConstantExpr>(UserC) && "Must be a ConstantExpr.");
NewC = cast<ConstantExpr>(UserC)->getWithOperands(NewOps);
}
UserC->replaceAllUsesWith(NewC);
UserC->destroyConstant();
NewOps.clear();
}
// Update all ValueHandles, they should be the only users at this point.
Placeholder->replaceAllUsesWith(RealVal);
Placeholder->deleteValue();
}
}
