#include "llvm/Transforms/IPO.h"
#include "llvm/ADT/EquivalenceClasses.h"
#include "llvm/ADT/Statistic.h"
+#include "llvm/ADT/Triple.h"
#include "llvm/IR/Constant.h"
#include "llvm/IR/Constants.h"
#include "llvm/IR/GlobalVariable.h"
#include "llvm/IR/Module.h"
#include "llvm/IR/Operator.h"
#include "llvm/Pass.h"
+#include "llvm/Support/Debug.h"
+#include "llvm/Support/raw_ostream.h"
#include "llvm/Transforms/Utils/BasicBlockUtils.h"
using namespace llvm;
#define DEBUG_TYPE "lowerbitsets"
-STATISTIC(NumBitSetsCreated, "Number of bitsets created");
+STATISTIC(ByteArraySizeBits, "Byte array size in bits");
+STATISTIC(ByteArraySizeBytes, "Byte array size in bytes");
+STATISTIC(NumByteArraysCreated, "Number of byte arrays created");
STATISTIC(NumBitSetCallsLowered, "Number of bitset calls lowered");
STATISTIC(NumBitSetDisjointSets, "Number of disjoint sets of bitsets");
+static cl::opt<bool> AvoidReuse(
+ "lowerbitsets-avoid-reuse",
+ cl::desc("Try to avoid reuse of byte array addresses using aliases"),
+ cl::Hidden, cl::init(true));
+
bool BitSetInfo::containsGlobalOffset(uint64_t Offset) const {
if (Offset < ByteOffset)
return false;
if (BitOffset >= BitSize)
return false;
- return (Bits[BitOffset / 8] >> (BitOffset % 8)) & 1;
+ return Bits.count(BitOffset);
}
bool BitSetInfo::containsValue(
- const DataLayout *DL,
+ const DataLayout &DL,
const DenseMap<GlobalVariable *, uint64_t> &GlobalLayout, Value *V,
uint64_t COffset) const {
if (auto GV = dyn_cast<GlobalVariable>(V)) {
}
if (auto GEP = dyn_cast<GEPOperator>(V)) {
- APInt APOffset(DL->getPointerSizeInBits(0), 0);
- bool Result = GEP->accumulateConstantOffset(*DL, APOffset);
+ APInt APOffset(DL.getPointerSizeInBits(0), 0);
+ bool Result = GEP->accumulateConstantOffset(DL, APOffset);
if (!Result)
return false;
COffset += APOffset.getZExtValue();
return false;
}
+void BitSetInfo::print(raw_ostream &OS) const {
+ OS << "offset " << ByteOffset << " size " << BitSize << " align "
+ << (1 << AlignLog2);
+
+ if (isAllOnes()) {
+ OS << " all-ones\n";
+ return;
+ }
+
+ OS << " { ";
+ for (uint64_t B : Bits)
+ OS << B << ' ';
+ OS << "}\n";
+ return;
+}
+
BitSetInfo BitSetBuilder::build() {
if (Min > Max)
Min = 0;
BSI.ByteOffset = Min;
BSI.AlignLog2 = 0;
- // FIXME: Can probably do something smarter if all offsets are 0.
if (Mask != 0)
BSI.AlignLog2 = countTrailingZeros(Mask, ZB_Undefined);
// Build the compressed bitset while normalizing the offsets against the
// computed alignment.
BSI.BitSize = ((Max - Min) >> BSI.AlignLog2) + 1;
- uint64_t ByteSize = (BSI.BitSize + 7) / 8;
- BSI.Bits.resize(ByteSize);
for (uint64_t Offset : Offsets) {
Offset >>= BSI.AlignLog2;
- BSI.Bits[Offset / 8] |= 1 << (Offset % 8);
+ BSI.Bits.insert(Offset);
}
return BSI;
}
+void GlobalLayoutBuilder::addFragment(const std::set<uint64_t> &F) {
+ // Create a new fragment to hold the layout for F.
+ Fragments.emplace_back();
+ std::vector<uint64_t> &Fragment = Fragments.back();
+ uint64_t FragmentIndex = Fragments.size() - 1;
+
+ for (auto ObjIndex : F) {
+ uint64_t OldFragmentIndex = FragmentMap[ObjIndex];
+ if (OldFragmentIndex == 0) {
+ // We haven't seen this object index before, so just add it to the current
+ // fragment.
+ Fragment.push_back(ObjIndex);
+ } else {
+ // This index belongs to an existing fragment. Copy the elements of the
+ // old fragment into this one and clear the old fragment. We don't update
+ // the fragment map just yet, this ensures that any further references to
+ // indices from the old fragment in this fragment do not insert any more
+ // indices.
+ std::vector<uint64_t> &OldFragment = Fragments[OldFragmentIndex];
+ Fragment.insert(Fragment.end(), OldFragment.begin(), OldFragment.end());
+ OldFragment.clear();
+ }
+ }
+
+ // Update the fragment map to point our object indices to this fragment.
+ for (uint64_t ObjIndex : Fragment)
+ FragmentMap[ObjIndex] = FragmentIndex;
+}
+
+void ByteArrayBuilder::allocate(const std::set<uint64_t> &Bits,
+ uint64_t BitSize, uint64_t &AllocByteOffset,
+ uint8_t &AllocMask) {
+ // Find the smallest current allocation.
+ unsigned Bit = 0;
+ for (unsigned I = 1; I != BitsPerByte; ++I)
+ if (BitAllocs[I] < BitAllocs[Bit])
+ Bit = I;
+
+ AllocByteOffset = BitAllocs[Bit];
+
+ // Add our size to it.
+ unsigned ReqSize = AllocByteOffset + BitSize;
+ BitAllocs[Bit] = ReqSize;
+ if (Bytes.size() < ReqSize)
+ Bytes.resize(ReqSize);
+
+ // Set our bits.
+ AllocMask = 1 << Bit;
+ for (uint64_t B : Bits)
+ Bytes[AllocByteOffset + B] |= AllocMask;
+}
+
namespace {
+struct ByteArrayInfo {
+ std::set<uint64_t> Bits;
+ uint64_t BitSize;
+ GlobalVariable *ByteArray;
+ Constant *Mask;
+};
+
struct LowerBitSets : public ModulePass {
static char ID;
LowerBitSets() : ModulePass(ID) {
initializeLowerBitSetsPass(*PassRegistry::getPassRegistry());
}
- const DataLayout *DL;
+ Module *M;
+
+ bool LinkerSubsectionsViaSymbols;
IntegerType *Int1Ty;
+ IntegerType *Int8Ty;
IntegerType *Int32Ty;
Type *Int32PtrTy;
IntegerType *Int64Ty;
// Mapping from bitset mdstrings to the call sites that test them.
DenseMap<MDString *, std::vector<CallInst *>> BitSetTestCallSites;
+ std::vector<ByteArrayInfo> ByteArrayInfos;
+
BitSetInfo
buildBitSet(MDString *BitSet,
const DenseMap<GlobalVariable *, uint64_t> &GlobalLayout);
- Value *createBitSetTest(IRBuilder<> &B, const BitSetInfo &BSI,
- GlobalVariable *BitSetGlobal, Value *BitOffset);
- void
- lowerBitSetCall(CallInst *CI, const BitSetInfo &BSI,
- GlobalVariable *BitSetGlobal, GlobalVariable *CombinedGlobal,
+ ByteArrayInfo *createByteArray(BitSetInfo &BSI);
+ void allocateByteArrays();
+ Value *createBitSetTest(IRBuilder<> &B, BitSetInfo &BSI, ByteArrayInfo *&BAI,
+ Value *BitOffset);
+ Value *
+ lowerBitSetCall(CallInst *CI, BitSetInfo &BSI, ByteArrayInfo *&BAI,
+ GlobalVariable *CombinedGlobal,
const DenseMap<GlobalVariable *, uint64_t> &GlobalLayout);
- void buildBitSetsFromGlobals(Module &M,
- const std::vector<MDString *> &BitSets,
+ void buildBitSetsFromGlobals(const std::vector<MDString *> &BitSets,
const std::vector<GlobalVariable *> &Globals);
- bool buildBitSets(Module &M);
- bool eraseBitSetMetadata(Module &M);
+ bool buildBitSets();
+ bool eraseBitSetMetadata();
bool doInitialization(Module &M) override;
bool runOnModule(Module &M) override;
ModulePass *llvm::createLowerBitSetsPass() { return new LowerBitSets; }
-bool LowerBitSets::doInitialization(Module &M) {
- DL = M.getDataLayout();
- if (!DL)
- report_fatal_error("Data layout required");
+bool LowerBitSets::doInitialization(Module &Mod) {
+ M = &Mod;
+ const DataLayout &DL = Mod.getDataLayout();
- Int1Ty = Type::getInt1Ty(M.getContext());
- Int32Ty = Type::getInt32Ty(M.getContext());
+ Triple TargetTriple(M->getTargetTriple());
+ LinkerSubsectionsViaSymbols = TargetTriple.isMacOSX();
+
+ Int1Ty = Type::getInt1Ty(M->getContext());
+ Int8Ty = Type::getInt8Ty(M->getContext());
+ Int32Ty = Type::getInt32Ty(M->getContext());
Int32PtrTy = PointerType::getUnqual(Int32Ty);
- Int64Ty = Type::getInt64Ty(M.getContext());
- IntPtrTy = DL->getIntPtrType(M.getContext(), 0);
+ Int64Ty = Type::getInt64Ty(M->getContext());
+ IntPtrTy = DL.getIntPtrType(M->getContext(), 0);
- BitSetNM = M.getNamedMetadata("llvm.bitsets");
+ BitSetNM = M->getNamedMetadata("llvm.bitsets");
BitSetTestCallSites.clear();
for (MDNode *Op : BitSetNM->operands()) {
if (Op->getOperand(0) != BitSet || !Op->getOperand(1))
continue;
- auto OpGlobal = cast<GlobalVariable>(
+ auto OpGlobal = dyn_cast<GlobalVariable>(
cast<ConstantAsMetadata>(Op->getOperand(1))->getValue());
+ if (!OpGlobal)
+ continue;
uint64_t Offset =
cast<ConstantInt>(cast<ConstantAsMetadata>(Op->getOperand(2))
->getValue())->getZExtValue();
return B.CreateICmpNE(MaskedBits, ConstantInt::get(BitsType, 0));
}
+ByteArrayInfo *LowerBitSets::createByteArray(BitSetInfo &BSI) {
+ // Create globals to stand in for byte arrays and masks. These never actually
+ // get initialized, we RAUW and erase them later in allocateByteArrays() once
+ // we know the offset and mask to use.
+ auto ByteArrayGlobal = new GlobalVariable(
+ *M, Int8Ty, /*isConstant=*/true, GlobalValue::PrivateLinkage, nullptr);
+ auto MaskGlobal = new GlobalVariable(
+ *M, Int8Ty, /*isConstant=*/true, GlobalValue::PrivateLinkage, nullptr);
+
+ ByteArrayInfos.emplace_back();
+ ByteArrayInfo *BAI = &ByteArrayInfos.back();
+
+ BAI->Bits = BSI.Bits;
+ BAI->BitSize = BSI.BitSize;
+ BAI->ByteArray = ByteArrayGlobal;
+ BAI->Mask = ConstantExpr::getPtrToInt(MaskGlobal, Int8Ty);
+ return BAI;
+}
+
+void LowerBitSets::allocateByteArrays() {
+ std::stable_sort(ByteArrayInfos.begin(), ByteArrayInfos.end(),
+ [](const ByteArrayInfo &BAI1, const ByteArrayInfo &BAI2) {
+ return BAI1.BitSize > BAI2.BitSize;
+ });
+
+ std::vector<uint64_t> ByteArrayOffsets(ByteArrayInfos.size());
+
+ ByteArrayBuilder BAB;
+ for (unsigned I = 0; I != ByteArrayInfos.size(); ++I) {
+ ByteArrayInfo *BAI = &ByteArrayInfos[I];
+
+ uint8_t Mask;
+ BAB.allocate(BAI->Bits, BAI->BitSize, ByteArrayOffsets[I], Mask);
+
+ BAI->Mask->replaceAllUsesWith(ConstantInt::get(Int8Ty, Mask));
+ cast<GlobalVariable>(BAI->Mask->getOperand(0))->eraseFromParent();
+ }
+
+ Constant *ByteArrayConst = ConstantDataArray::get(M->getContext(), BAB.Bytes);
+ auto ByteArray =
+ new GlobalVariable(*M, ByteArrayConst->getType(), /*isConstant=*/true,
+ GlobalValue::PrivateLinkage, ByteArrayConst);
+
+ for (unsigned I = 0; I != ByteArrayInfos.size(); ++I) {
+ ByteArrayInfo *BAI = &ByteArrayInfos[I];
+
+ Constant *Idxs[] = {ConstantInt::get(IntPtrTy, 0),
+ ConstantInt::get(IntPtrTy, ByteArrayOffsets[I])};
+ Constant *GEP = ConstantExpr::getInBoundsGetElementPtr(
+ ByteArrayConst->getType(), ByteArray, Idxs);
+
+ // Create an alias instead of RAUW'ing the gep directly. On x86 this ensures
+ // that the pc-relative displacement is folded into the lea instead of the
+ // test instruction getting another displacement.
+ if (LinkerSubsectionsViaSymbols) {
+ BAI->ByteArray->replaceAllUsesWith(GEP);
+ } else {
+ GlobalAlias *Alias =
+ GlobalAlias::create(PointerType::getUnqual(Int8Ty),
+ GlobalValue::PrivateLinkage, "bits", GEP, M);
+ BAI->ByteArray->replaceAllUsesWith(Alias);
+ }
+ BAI->ByteArray->eraseFromParent();
+ }
+
+ ByteArraySizeBits = BAB.BitAllocs[0] + BAB.BitAllocs[1] + BAB.BitAllocs[2] +
+ BAB.BitAllocs[3] + BAB.BitAllocs[4] + BAB.BitAllocs[5] +
+ BAB.BitAllocs[6] + BAB.BitAllocs[7];
+ ByteArraySizeBytes = BAB.Bytes.size();
+}
+
/// Build a test that bit BitOffset is set in BSI, where
/// BitSetGlobal is a global containing the bits in BSI.
-Value *LowerBitSets::createBitSetTest(IRBuilder<> &B, const BitSetInfo &BSI,
- GlobalVariable *BitSetGlobal,
- Value *BitOffset) {
- if (BSI.Bits.size() <= 8) {
+Value *LowerBitSets::createBitSetTest(IRBuilder<> &B, BitSetInfo &BSI,
+ ByteArrayInfo *&BAI, Value *BitOffset) {
+ if (BSI.BitSize <= 64) {
// If the bit set is sufficiently small, we can avoid a load by bit testing
// a constant.
IntegerType *BitsTy;
- if (BSI.Bits.size() <= 4)
+ if (BSI.BitSize <= 32)
BitsTy = Int32Ty;
else
BitsTy = Int64Ty;
uint64_t Bits = 0;
- for (auto I = BSI.Bits.rbegin(), E = BSI.Bits.rend(); I != E; ++I) {
- Bits <<= 8;
- Bits |= *I;
- }
+ for (auto Bit : BSI.Bits)
+ Bits |= uint64_t(1) << Bit;
Constant *BitsConst = ConstantInt::get(BitsTy, Bits);
return createMaskedBitTest(B, BitsConst, BitOffset);
} else {
- // TODO: We might want to use the memory variant of the bt instruction
- // with the previously computed bit offset at -Os. This instruction does
- // exactly what we want but has been benchmarked as being slower than open
- // coding the load+bt.
- Value *BitSetGlobalOffset =
- B.CreateLShr(BitOffset, ConstantInt::get(IntPtrTy, 5));
- Value *BitSetEntryAddr = B.CreateGEP(
- ConstantExpr::getBitCast(BitSetGlobal, Int32PtrTy), BitSetGlobalOffset);
- Value *BitSetEntry = B.CreateLoad(BitSetEntryAddr);
-
- return createMaskedBitTest(B, BitSetEntry, BitOffset);
+ if (!BAI) {
+ ++NumByteArraysCreated;
+ BAI = createByteArray(BSI);
+ }
+
+ Constant *ByteArray = BAI->ByteArray;
+ Type *Ty = BAI->ByteArray->getValueType();
+ if (!LinkerSubsectionsViaSymbols && AvoidReuse) {
+ // Each use of the byte array uses a different alias. This makes the
+ // backend less likely to reuse previously computed byte array addresses,
+ // improving the security of the CFI mechanism based on this pass.
+ ByteArray = GlobalAlias::create(BAI->ByteArray->getType(),
+ GlobalValue::PrivateLinkage, "bits_use",
+ ByteArray, M);
+ }
+
+ Value *ByteAddr = B.CreateGEP(Ty, ByteArray, BitOffset);
+ Value *Byte = B.CreateLoad(ByteAddr);
+
+ Value *ByteAndMask = B.CreateAnd(Byte, BAI->Mask);
+ return B.CreateICmpNE(ByteAndMask, ConstantInt::get(Int8Ty, 0));
}
}
-/// Lower a llvm.bitset.test call to its implementation.
-void LowerBitSets::lowerBitSetCall(
- CallInst *CI, const BitSetInfo &BSI, GlobalVariable *BitSetGlobal,
+/// Lower a llvm.bitset.test call to its implementation. Returns the value to
+/// replace the call with.
+Value *LowerBitSets::lowerBitSetCall(
+ CallInst *CI, BitSetInfo &BSI, ByteArrayInfo *&BAI,
GlobalVariable *CombinedGlobal,
const DenseMap<GlobalVariable *, uint64_t> &GlobalLayout) {
Value *Ptr = CI->getArgOperand(0);
+ const DataLayout &DL = M->getDataLayout();
- if (BSI.containsValue(DL, GlobalLayout, Ptr)) {
- CI->replaceAllUsesWith(
- ConstantInt::getTrue(BitSetGlobal->getParent()->getContext()));
- CI->eraseFromParent();
- return;
- }
+ if (BSI.containsValue(DL, GlobalLayout, Ptr))
+ return ConstantInt::getTrue(CombinedGlobal->getParent()->getContext());
Constant *GlobalAsInt = ConstantExpr::getPtrToInt(CombinedGlobal, IntPtrTy);
Constant *OffsetedGlobalAsInt = ConstantExpr::getAdd(
Value *PtrAsInt = B.CreatePtrToInt(Ptr, IntPtrTy);
- if (BSI.isSingleOffset()) {
- Value *Eq = B.CreateICmpEQ(PtrAsInt, OffsetedGlobalAsInt);
- CI->replaceAllUsesWith(Eq);
- CI->eraseFromParent();
- return;
- }
+ if (BSI.isSingleOffset())
+ return B.CreateICmpEQ(PtrAsInt, OffsetedGlobalAsInt);
Value *PtrOffset = B.CreateSub(PtrAsInt, OffsetedGlobalAsInt);
Value *OffsetSHR =
B.CreateLShr(PtrOffset, ConstantInt::get(IntPtrTy, BSI.AlignLog2));
Value *OffsetSHL = B.CreateShl(
- PtrOffset, ConstantInt::get(IntPtrTy, DL->getPointerSizeInBits(0) -
- BSI.AlignLog2));
+ PtrOffset,
+ ConstantInt::get(IntPtrTy, DL.getPointerSizeInBits(0) - BSI.AlignLog2));
BitOffset = B.CreateOr(OffsetSHR, OffsetSHL);
}
Constant *BitSizeConst = ConstantInt::get(IntPtrTy, BSI.BitSize);
Value *OffsetInRange = B.CreateICmpULT(BitOffset, BitSizeConst);
+ // If the bit set is all ones, testing against it is unnecessary.
+ if (BSI.isAllOnes())
+ return OffsetInRange;
+
TerminatorInst *Term = SplitBlockAndInsertIfThen(OffsetInRange, CI, false);
IRBuilder<> ThenB(Term);
// Now that we know that the offset is in range and aligned, load the
// appropriate bit from the bitset.
- Value *Bit = createBitSetTest(ThenB, BSI, BitSetGlobal, BitOffset);
+ Value *Bit = createBitSetTest(ThenB, BSI, BAI, BitOffset);
// The value we want is 0 if we came directly from the initial block
// (having failed the range or alignment checks), or the loaded bit if
PHINode *P = B.CreatePHI(Int1Ty, 2);
P->addIncoming(ConstantInt::get(Int1Ty, 0), InitialBB);
P->addIncoming(Bit, ThenB.GetInsertBlock());
-
- CI->replaceAllUsesWith(P);
- CI->eraseFromParent();
+ return P;
}
/// Given a disjoint set of bitsets and globals, layout the globals, build the
/// bit sets and lower the llvm.bitset.test calls.
void LowerBitSets::buildBitSetsFromGlobals(
- Module &M,
const std::vector<MDString *> &BitSets,
const std::vector<GlobalVariable *> &Globals) {
// Build a new global with the combined contents of the referenced globals.
std::vector<Constant *> GlobalInits;
- for (GlobalVariable *G : Globals)
+ const DataLayout &DL = M->getDataLayout();
+ for (GlobalVariable *G : Globals) {
GlobalInits.push_back(G->getInitializer());
- Constant *NewInit = ConstantStruct::getAnon(M.getContext(), GlobalInits);
+ uint64_t InitSize = DL.getTypeAllocSize(G->getInitializer()->getType());
+
+ // Compute the amount of padding required to align the next element to the
+ // next power of 2.
+ 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,
+ new GlobalVariable(*M, NewInit->getType(), /*isConstant=*/true,
GlobalValue::PrivateLinkage, NewInit);
const StructLayout *CombinedGlobalLayout =
- DL->getStructLayout(cast<StructType>(NewInit->getType()));
+ DL.getStructLayout(cast<StructType>(NewInit->getType()));
// Compute the offsets of the original globals within the new global.
DenseMap<GlobalVariable *, uint64_t> GlobalLayout;
for (unsigned I = 0; I != Globals.size(); ++I)
- GlobalLayout[Globals[I]] = CombinedGlobalLayout->getElementOffset(I);
+ // Multiply by 2 to account for padding elements.
+ GlobalLayout[Globals[I]] = CombinedGlobalLayout->getElementOffset(I * 2);
// For each bitset in this disjoint set...
for (MDString *BS : BitSets) {
// Build the bitset.
BitSetInfo BSI = buildBitSet(BS, GlobalLayout);
+ DEBUG({
+ dbgs() << BS->getString() << ": ";
+ BSI.print(dbgs());
+ });
- // Create a global in which to store it.
- ++NumBitSetsCreated;
- Constant *BitsConst = ConstantDataArray::get(M.getContext(), BSI.Bits);
- auto BitSetGlobal = new GlobalVariable(
- M, BitsConst->getType(), /*isConstant=*/true,
- GlobalValue::PrivateLinkage, BitsConst, BS->getString() + ".bits");
+ ByteArrayInfo *BAI = 0;
// Lower each call to llvm.bitset.test for this bitset.
for (CallInst *CI : BitSetTestCallSites[BS]) {
++NumBitSetCallsLowered;
- lowerBitSetCall(CI, BSI, BitSetGlobal, CombinedGlobal, GlobalLayout);
+ Value *Lowered = lowerBitSetCall(CI, BSI, BAI, CombinedGlobal, GlobalLayout);
+ CI->replaceAllUsesWith(Lowered);
+ CI->eraseFromParent();
}
}
// 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)};
- Constant *CombinedGlobalElemPtr =
- ConstantExpr::getGetElementPtr(CombinedGlobal, CombinedGlobalIdxs);
- GlobalAlias *GAlias = GlobalAlias::create(
- Globals[I]->getType()->getElementType(),
- Globals[I]->getType()->getAddressSpace(), Globals[I]->getLinkage(),
- "", CombinedGlobalElemPtr, &M);
- GAlias->takeName(Globals[I]);
- Globals[I]->replaceAllUsesWith(GAlias);
+ ConstantInt::get(Int32Ty, I * 2)};
+ Constant *CombinedGlobalElemPtr = ConstantExpr::getGetElementPtr(
+ NewInit->getType(), CombinedGlobal, CombinedGlobalIdxs);
+ if (LinkerSubsectionsViaSymbols) {
+ Globals[I]->replaceAllUsesWith(CombinedGlobalElemPtr);
+ } else {
+ GlobalAlias *GAlias =
+ GlobalAlias::create(Globals[I]->getType(), Globals[I]->getLinkage(),
+ "", CombinedGlobalElemPtr, M);
+ GAlias->takeName(Globals[I]);
+ Globals[I]->replaceAllUsesWith(GAlias);
+ }
Globals[I]->eraseFromParent();
}
}
/// Lower all bit sets in this module.
-bool LowerBitSets::buildBitSets(Module &M) {
+bool LowerBitSets::buildBitSets() {
Function *BitSetTestFunc =
- M.getFunction(Intrinsic::getName(Intrinsic::bitset_test));
+ M->getFunction(Intrinsic::getName(Intrinsic::bitset_test));
if (!BitSetTestFunc)
return false;
report_fatal_error("Bit set element must be a constant");
auto OpGlobal = dyn_cast<GlobalVariable>(OpConstMD->getValue());
if (!OpGlobal)
- report_fatal_error("Bit set element must refer to global");
+ continue;
auto OffsetConstMD = dyn_cast<ConstantAsMetadata>(Op->getOperand(2));
if (!OffsetConstMD)
// Build the list of bitsets and referenced globals in this disjoint set.
std::vector<MDString *> BitSets;
std::vector<GlobalVariable *> Globals;
+ llvm::DenseMap<MDString *, uint64_t> BitSetIndices;
+ llvm::DenseMap<GlobalVariable *, uint64_t> GlobalIndices;
for (GlobalClassesTy::member_iterator MI = GlobalClasses.member_begin(I);
MI != GlobalClasses.member_end(); ++MI) {
- if ((*MI).is<MDString *>())
+ if ((*MI).is<MDString *>()) {
+ BitSetIndices[MI->get<MDString *>()] = BitSets.size();
BitSets.push_back(MI->get<MDString *>());
- else
+ } else {
+ GlobalIndices[MI->get<GlobalVariable *>()] = Globals.size();
Globals.push_back(MI->get<GlobalVariable *>());
+ }
}
- // Order bitsets and globals by name for determinism. TODO: We may later
- // want to use a more sophisticated ordering that lays out globals so as to
- // minimize the sizes of the bitsets.
+ // For each bitset, build a set of indices that refer to globals referenced
+ // by the bitset.
+ std::vector<std::set<uint64_t>> BitSetMembers(BitSets.size());
+ if (BitSetNM) {
+ for (MDNode *Op : BitSetNM->operands()) {
+ // Op = { bitset name, global, offset }
+ if (!Op->getOperand(1))
+ continue;
+ auto I = BitSetIndices.find(cast<MDString>(Op->getOperand(0)));
+ if (I == BitSetIndices.end())
+ continue;
+
+ auto OpGlobal = dyn_cast<GlobalVariable>(
+ cast<ConstantAsMetadata>(Op->getOperand(1))->getValue());
+ if (!OpGlobal)
+ continue;
+ BitSetMembers[I->second].insert(GlobalIndices[OpGlobal]);
+ }
+ }
+
+ // Order the sets of indices by size. The GlobalLayoutBuilder works best
+ // when given small index sets first.
+ std::stable_sort(
+ BitSetMembers.begin(), BitSetMembers.end(),
+ [](const std::set<uint64_t> &O1, const std::set<uint64_t> &O2) {
+ return O1.size() < O2.size();
+ });
+
+ // Create a GlobalLayoutBuilder and provide it with index sets as layout
+ // fragments. The GlobalLayoutBuilder tries to lay out members of fragments
+ // as close together as possible.
+ GlobalLayoutBuilder GLB(Globals.size());
+ for (auto &&MemSet : BitSetMembers)
+ GLB.addFragment(MemSet);
+
+ // Build a vector of globals with the computed layout.
+ std::vector<GlobalVariable *> OrderedGlobals(Globals.size());
+ auto OGI = OrderedGlobals.begin();
+ for (auto &&F : GLB.Fragments)
+ for (auto &&Offset : F)
+ *OGI++ = Globals[Offset];
+
+ // Order bitsets by name for determinism.
std::sort(BitSets.begin(), BitSets.end(), [](MDString *S1, MDString *S2) {
return S1->getString() < S2->getString();
});
- std::sort(Globals.begin(), Globals.end(),
- [](GlobalVariable *GV1, GlobalVariable *GV2) {
- return GV1->getName() < GV2->getName();
- });
// Build the bitsets from this disjoint set.
- buildBitSetsFromGlobals(M, BitSets, Globals);
+ buildBitSetsFromGlobals(BitSets, OrderedGlobals);
}
+ allocateByteArrays();
+
return true;
}
-bool LowerBitSets::eraseBitSetMetadata(Module &M) {
+bool LowerBitSets::eraseBitSetMetadata() {
if (!BitSetNM)
return false;
- M.eraseNamedMetadata(BitSetNM);
+ M->eraseNamedMetadata(BitSetNM);
return true;
}
bool LowerBitSets::runOnModule(Module &M) {
- bool Changed = buildBitSets(M);
- Changed |= eraseBitSetMetadata(M);
+ bool Changed = buildBitSets();
+ Changed |= eraseBitSetMetadata();
return Changed;
}
projects / oota-llvm.git / blobdiff