static bool fold(std::vector<Function *> &FnVec, unsigned i, unsigned j) {
if (FnVec[i]->mayBeOverridden() && !FnVec[j]->mayBeOverridden())
std::swap(FnVec[i], FnVec[j]);
Function *F = FnVec[i];
Function *G = FnVec[j];
if (!F->mayBeOverridden()) {
if (G->hasLocalLinkage()) {
F->setAlignment(std::max(F->getAlignment(), G->getAlignment()));
G->replaceAllUsesWith(F);
G->eraseFromParent();
++NumFunctionsMerged;
return true;
}
if (G->hasExternalLinkage() || G->hasWeakLinkage()) {
GlobalAlias *GA = new GlobalAlias(G->getType(), G->getLinkage(), "",
F, G->getParent());
F->setAlignment(std::max(F->getAlignment(), G->getAlignment()));
GA->takeName(G);
GA->setVisibility(G->getVisibility());
G->replaceAllUsesWith(GA);
G->eraseFromParent();
++NumFunctionsMerged;
return true;
}
}
if (F->hasWeakLinkage() && G->hasWeakLinkage()) {
GlobalAlias *GA_F = new GlobalAlias(F->getType(), F->getLinkage(), "",
0, F->getParent());
GA_F->takeName(F);
GA_F->setVisibility(F->getVisibility());
F->setAlignment(std::max(F->getAlignment(), G->getAlignment()));
F->replaceAllUsesWith(GA_F);
F->setName("folded." + GA_F->getName());
F->setLinkage(GlobalValue::ExternalLinkage);
GA_F->setAliasee(F);
GlobalAlias *GA_G = new GlobalAlias(G->getType(), G->getLinkage(), "",
F, G->getParent());
GA_G->takeName(G);
GA_G->setVisibility(G->getVisibility());
G->replaceAllUsesWith(GA_G);
G->eraseFromParent();
++NumFunctionsMerged;
return true;
}
DOUT << "Failed on " << F->getName() << " and " << G->getName() << "\n";
++NumMergeFails;
return false;
}
static void AliasGToF(Function *F, Function *G) {
if (!G->hasExternalLinkage() && !G->hasLocalLinkage() && !G->hasWeakLinkage())
return ThunkGToF(F, G);
GlobalAlias *GA = new GlobalAlias(
G->getType(), G->getLinkage(), "",
ConstantExpr::getBitCast(F, G->getType()), G->getParent());
F->setAlignment(std::max(F->getAlignment(), G->getAlignment()));
GA->takeName(G);
GA->setVisibility(G->getVisibility());
G->replaceAllUsesWith(GA);
G->eraseFromParent();
}
// Replace G with an alias to F and delete G.
void MergeFunctions::writeAlias(Function *F, Function *G) {
Constant *BitcastF = ConstantExpr::getBitCast(F, G->getType());
GlobalAlias *GA = new GlobalAlias(G->getType(), G->getLinkage(), "",
BitcastF, G->getParent());
F->setAlignment(std::max(F->getAlignment(), G->getAlignment()));
GA->takeName(G);
GA->setVisibility(G->getVisibility());
removeUsers(G);
G->replaceAllUsesWith(GA);
G->eraseFromParent();
DEBUG(dbgs() << "writeAlias: " << GA->getName() << '\n');
++NumAliasesWritten;
}
/// Given a disjoint set of bitsets and globals, layout the globals, build the
/// bit sets and lower the llvm.bitset.test calls.
void LowerBitSets::buildBitSetsFromGlobalVariables(
ArrayRef<Metadata *> BitSets, ArrayRef<GlobalVariable *> Globals) {
// Build a new global with the combined contents of the referenced globals.
// This global is a struct whose even-indexed elements contain the original
// contents of the referenced globals and whose odd-indexed elements contain
// any padding required to align the next element to the next power of 2.
std::vector<Constant *> GlobalInits;
const DataLayout &DL = M->getDataLayout();
for (GlobalVariable *G : Globals) {
GlobalInits.push_back(G->getInitializer());
uint64_t InitSize = DL.getTypeAllocSize(G->getValueType());
// Compute the amount of padding required.
uint64_t Padding = NextPowerOf2(InitSize - 1) - InitSize;
// Cap at 128 was found experimentally to have a good data/instruction
// overhead tradeoff.
if (Padding > 128)
Padding = RoundUpToAlignment(InitSize, 128) - InitSize;
GlobalInits.push_back(
ConstantAggregateZero::get(ArrayType::get(Int8Ty, Padding)));
}
if (!GlobalInits.empty())
GlobalInits.pop_back();
Constant *NewInit = ConstantStruct::getAnon(M->getContext(), GlobalInits);
auto *CombinedGlobal =
new GlobalVariable(*M, NewInit->getType(), /*isConstant=*/true,
GlobalValue::PrivateLinkage, NewInit);
StructType *NewTy = cast<StructType>(NewInit->getType());
const StructLayout *CombinedGlobalLayout = DL.getStructLayout(NewTy);
// Compute the offsets of the original globals within the new global.
DenseMap<GlobalObject *, uint64_t> GlobalLayout;
for (unsigned I = 0; I != Globals.size(); ++I)
// Multiply by 2 to account for padding elements.
GlobalLayout[Globals[I]] = CombinedGlobalLayout->getElementOffset(I * 2);
lowerBitSetCalls(BitSets, CombinedGlobal, GlobalLayout);
// Build aliases pointing to offsets into the combined global for each
// global from which we built the combined global, and replace references
// to the original globals with references to the aliases.
for (unsigned I = 0; I != Globals.size(); ++I) {
// Multiply by 2 to account for padding elements.
Constant *CombinedGlobalIdxs[] = {ConstantInt::get(Int32Ty, 0),
ConstantInt::get(Int32Ty, I * 2)};
Constant *CombinedGlobalElemPtr = ConstantExpr::getGetElementPtr(
NewInit->getType(), CombinedGlobal, CombinedGlobalIdxs);
if (LinkerSubsectionsViaSymbols) {
Globals[I]->replaceAllUsesWith(CombinedGlobalElemPtr);
} else {
assert(Globals[I]->getType()->getAddressSpace() == 0);
GlobalAlias *GAlias = GlobalAlias::create(NewTy->getElementType(I * 2), 0,
Globals[I]->getLinkage(), "",
CombinedGlobalElemPtr, M);
GAlias->setVisibility(Globals[I]->getVisibility());
GAlias->takeName(Globals[I]);
Globals[I]->replaceAllUsesWith(GAlias);
}
Globals[I]->eraseFromParent();
}
}
// emit_alias_to_llvm - Given decl and target emit alias to target.
void emit_alias_to_llvm(tree decl, tree target, tree target_decl) {
if (errorcount || sorrycount) return;
timevar_push(TV_LLVM_GLOBALS);
// Get or create LLVM global for our alias.
GlobalValue *V = cast<GlobalValue>(DECL_LLVM(decl));
GlobalValue *Aliasee = NULL;
if (target_decl)
Aliasee = cast<GlobalValue>(DECL_LLVM(target_decl));
else {
// This is something insane. Probably only LTHUNKs can be here
// Try to grab decl from IDENTIFIER_NODE
// Query SymTab for aliasee
const char* AliaseeName = IDENTIFIER_POINTER(target);
Aliasee =
dyn_cast_or_null<GlobalValue>(TheModule->
getValueSymbolTable().lookup(AliaseeName));
// Last resort. Query for name set via __asm__
if (!Aliasee) {
std::string starred = std::string("\001") + AliaseeName;
Aliasee =
dyn_cast_or_null<GlobalValue>(TheModule->
getValueSymbolTable().lookup(starred));
}
if (!Aliasee) {
error ("%J%qD aliased to undefined symbol %qE",
decl, decl, target);
timevar_pop(TV_LLVM_GLOBALS);
return;
}
}
GlobalValue::LinkageTypes Linkage;
// Check for external weak linkage
if (DECL_EXTERNAL(decl) && DECL_WEAK(decl))
Linkage = GlobalValue::WeakLinkage;
else if (!TREE_PUBLIC(decl))
Linkage = GlobalValue::InternalLinkage;
else
Linkage = GlobalValue::ExternalLinkage;
GlobalAlias* GA = new GlobalAlias(Aliasee->getType(), Linkage, "",
Aliasee, TheModule);
// Handle visibility style
if (TREE_PUBLIC(decl)) {
if (DECL_VISIBILITY(decl) == VISIBILITY_HIDDEN)
GA->setVisibility(GlobalValue::HiddenVisibility);
else if (DECL_VISIBILITY(decl) == VISIBILITY_PROTECTED)
GA->setVisibility(GlobalValue::ProtectedVisibility);
}
if (V->getType() == GA->getType())
V->replaceAllUsesWith(GA);
else if (!V->use_empty()) {
error ("%J Alias %qD used with invalid type!", decl, decl);
timevar_pop(TV_LLVM_GLOBALS);
return;
}
changeLLVMValue(V, GA);
GA->takeName(V);
if (GlobalVariable *GV = dyn_cast<GlobalVariable>(V))
GV->eraseFromParent();
else if (GlobalAlias *GA = dyn_cast<GlobalAlias>(V))
GA->eraseFromParent();
else if (Function *F = dyn_cast<Function>(V))
F->eraseFromParent();
else
assert(0 && "Unsuported global value");
TREE_ASM_WRITTEN(decl) = 1;
timevar_pop(TV_LLVM_GLOBALS);
return;
}
