Introduce bitset metadata format and bitset lowering pass.
This patch introduces a new mechanism that allows IR modules to co-operatively
build pointer sets corresponding to addresses within a given set of
globals. One particular use case for this is to allow a C++ program to
efficiently verify (at each call site) that a vtable pointer is in the set
of valid vtable pointers for the class or its derived classes. One way of
doing this is for a toolchain component to build, for each class, a bit set
that maps to the memory region allocated for the vtables, such that each 1
bit in the bit set maps to a valid vtable for that class, and lay out the
vtables next to each other, to minimize the total size of the bit sets.
The patch introduces a metadata format for representing pointer sets, an
'@llvm.bitset.test' intrinsic and an LTO lowering pass that lays out the globals
and builds the bitsets, and documents the new feature.
Differential Revision: http://reviews.llvm.org/D7288
llvm-svn: 230054
diff --git a/llvm/lib/Transforms/IPO/CMakeLists.txt b/llvm/lib/Transforms/IPO/CMakeLists.txt
index 923c3af..3df17b9 100644
--- a/llvm/lib/Transforms/IPO/CMakeLists.txt
+++ b/llvm/lib/Transforms/IPO/CMakeLists.txt
@@ -14,6 +14,7 @@
Inliner.cpp
Internalize.cpp
LoopExtractor.cpp
+ LowerBitSets.cpp
MergeFunctions.cpp
PartialInlining.cpp
PassManagerBuilder.cpp
diff --git a/llvm/lib/Transforms/IPO/IPO.cpp b/llvm/lib/Transforms/IPO/IPO.cpp
index 1605efa..fcacec3 100644
--- a/llvm/lib/Transforms/IPO/IPO.cpp
+++ b/llvm/lib/Transforms/IPO/IPO.cpp
@@ -36,6 +36,7 @@
initializeLoopExtractorPass(Registry);
initializeBlockExtractorPassPass(Registry);
initializeSingleLoopExtractorPass(Registry);
+ initializeLowerBitSetsPass(Registry);
initializeMergeFunctionsPass(Registry);
initializePartialInlinerPass(Registry);
initializePruneEHPass(Registry);
diff --git a/llvm/lib/Transforms/IPO/LowerBitSets.cpp b/llvm/lib/Transforms/IPO/LowerBitSets.cpp
new file mode 100644
index 0000000..3be7dd5
--- /dev/null
+++ b/llvm/lib/Transforms/IPO/LowerBitSets.cpp
@@ -0,0 +1,526 @@
+//===-- LowerBitSets.cpp - Bitset lowering pass ---------------------------===//
+//
+// The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// This pass lowers bitset metadata and calls to the llvm.bitset.test intrinsic.
+// See http://llvm.org/docs/LangRef.html#bitsets for more information.
+//
+//===----------------------------------------------------------------------===//
+
+#include "llvm/Transforms/IPO/LowerBitSets.h"
+#include "llvm/Transforms/IPO.h"
+#include "llvm/ADT/EquivalenceClasses.h"
+#include "llvm/ADT/Statistic.h"
+#include "llvm/IR/Constant.h"
+#include "llvm/IR/Constants.h"
+#include "llvm/IR/GlobalVariable.h"
+#include "llvm/IR/IRBuilder.h"
+#include "llvm/IR/Instructions.h"
+#include "llvm/IR/Intrinsics.h"
+#include "llvm/IR/Module.h"
+#include "llvm/IR/Operator.h"
+#include "llvm/Pass.h"
+#include "llvm/Transforms/Utils/BasicBlockUtils.h"
+
+using namespace llvm;
+
+#define DEBUG_TYPE "lowerbitsets"
+
+STATISTIC(NumBitSetsCreated, "Number of bitsets created");
+STATISTIC(NumBitSetCallsLowered, "Number of bitset calls lowered");
+STATISTIC(NumBitSetDisjointSets, "Number of disjoint sets of bitsets");
+
+bool BitSetInfo::containsGlobalOffset(uint64_t Offset) const {
+ if (Offset < ByteOffset)
+ return false;
+
+ if ((Offset - ByteOffset) % (uint64_t(1) << AlignLog2) != 0)
+ return false;
+
+ uint64_t BitOffset = (Offset - ByteOffset) >> AlignLog2;
+ if (BitOffset >= BitSize)
+ return false;
+
+ return (Bits[BitOffset / 8] >> (BitOffset % 8)) & 1;
+}
+
+bool BitSetInfo::containsValue(
+ const DataLayout *DL,
+ const DenseMap<GlobalVariable *, uint64_t> &GlobalLayout, Value *V,
+ uint64_t COffset) const {
+ if (auto GV = dyn_cast<GlobalVariable>(V)) {
+ auto I = GlobalLayout.find(GV);
+ if (I == GlobalLayout.end())
+ return false;
+ return containsGlobalOffset(I->second + COffset);
+ }
+
+ if (auto GEP = dyn_cast<GEPOperator>(V)) {
+ APInt APOffset(DL->getPointerSizeInBits(0), 0);
+ bool Result = GEP->accumulateConstantOffset(*DL, APOffset);
+ if (!Result)
+ return false;
+ COffset += APOffset.getZExtValue();
+ return containsValue(DL, GlobalLayout, GEP->getPointerOperand(),
+ COffset);
+ }
+
+ if (auto Op = dyn_cast<Operator>(V)) {
+ if (Op->getOpcode() == Instruction::BitCast)
+ return containsValue(DL, GlobalLayout, Op->getOperand(0), COffset);
+
+ if (Op->getOpcode() == Instruction::Select)
+ return containsValue(DL, GlobalLayout, Op->getOperand(1), COffset) &&
+ containsValue(DL, GlobalLayout, Op->getOperand(2), COffset);
+ }
+
+ return false;
+}
+
+BitSetInfo BitSetBuilder::build() {
+ if (Min > Max)
+ Min = 0;
+
+ // Normalize each offset against the minimum observed offset, and compute
+ // the bitwise OR of each of the offsets. The number of trailing zeros
+ // in the mask gives us the log2 of the alignment of all offsets, which
+ // allows us to compress the bitset by only storing one bit per aligned
+ // address.
+ uint64_t Mask = 0;
+ for (uint64_t &Offset : Offsets) {
+ Offset -= Min;
+ Mask |= Offset;
+ }
+
+ BitSetInfo BSI;
+ 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);
+ }
+
+ return BSI;
+}
+
+namespace {
+
+struct LowerBitSets : public ModulePass {
+ static char ID;
+ LowerBitSets() : ModulePass(ID) {
+ initializeLowerBitSetsPass(*PassRegistry::getPassRegistry());
+ }
+
+ const DataLayout *DL;
+ IntegerType *Int1Ty;
+ IntegerType *Int32Ty;
+ Type *Int32PtrTy;
+ IntegerType *Int64Ty;
+ Type *IntPtrTy;
+
+ // The llvm.bitsets named metadata.
+ NamedMDNode *BitSetNM;
+
+ // Mapping from bitset mdstrings to the call sites that test them.
+ DenseMap<MDString *, std::vector<CallInst *>> BitSetTestCallSites;
+
+ 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,
+ const DenseMap<GlobalVariable *, uint64_t> &GlobalLayout);
+ void buildBitSetsFromGlobals(Module &M,
+ const std::vector<MDString *> &BitSets,
+ const std::vector<GlobalVariable *> &Globals);
+ bool buildBitSets(Module &M);
+ bool eraseBitSetMetadata(Module &M);
+
+ bool doInitialization(Module &M) override;
+ bool runOnModule(Module &M) override;
+};
+
+} // namespace
+
+INITIALIZE_PASS_BEGIN(LowerBitSets, "lowerbitsets",
+ "Lower bitset metadata", false, false)
+INITIALIZE_PASS_END(LowerBitSets, "lowerbitsets",
+ "Lower bitset metadata", false, false)
+char LowerBitSets::ID = 0;
+
+ModulePass *llvm::createLowerBitSetsPass() { return new LowerBitSets; }
+
+bool LowerBitSets::doInitialization(Module &M) {
+ DL = M.getDataLayout();
+ if (!DL)
+ report_fatal_error("Data layout required");
+
+ Int1Ty = Type::getInt1Ty(M.getContext());
+ Int32Ty = Type::getInt32Ty(M.getContext());
+ Int32PtrTy = PointerType::getUnqual(Int32Ty);
+ Int64Ty = Type::getInt64Ty(M.getContext());
+ IntPtrTy = DL->getIntPtrType(M.getContext(), 0);
+
+ BitSetNM = M.getNamedMetadata("llvm.bitsets");
+
+ BitSetTestCallSites.clear();
+
+ return false;
+}
+
+/// Build a bit set for \param BitSet using the object layouts in
+/// \param GlobalLayout.
+BitSetInfo LowerBitSets::buildBitSet(
+ MDString *BitSet,
+ const DenseMap<GlobalVariable *, uint64_t> &GlobalLayout) {
+ BitSetBuilder BSB;
+
+ // Compute the byte offset of each element of this bitset.
+ if (BitSetNM) {
+ for (MDNode *Op : BitSetNM->operands()) {
+ if (Op->getOperand(0) != BitSet || !Op->getOperand(1))
+ continue;
+ auto OpGlobal = cast<GlobalVariable>(
+ cast<ConstantAsMetadata>(Op->getOperand(1))->getValue());
+ uint64_t Offset =
+ cast<ConstantInt>(cast<ConstantAsMetadata>(Op->getOperand(2))
+ ->getValue())->getZExtValue();
+
+ Offset += GlobalLayout.find(OpGlobal)->second;
+
+ BSB.addOffset(Offset);
+ }
+ }
+
+ return BSB.build();
+}
+
+/// Build a test that bit \param BitOffset mod sizeof(Bits)*8 is set in
+/// \param Bits. This pattern matches to the bt instruction on x86.
+static Value *createMaskedBitTest(IRBuilder<> &B, Value *Bits,
+ Value *BitOffset) {
+ auto BitsType = cast<IntegerType>(Bits->getType());
+ unsigned BitWidth = BitsType->getBitWidth();
+
+ BitOffset = B.CreateZExtOrTrunc(BitOffset, BitsType);
+ Value *BitIndex =
+ B.CreateAnd(BitOffset, ConstantInt::get(BitsType, BitWidth - 1));
+ Value *BitMask = B.CreateShl(ConstantInt::get(BitsType, 1), BitIndex);
+ Value *MaskedBits = B.CreateAnd(Bits, BitMask);
+ return B.CreateICmpNE(MaskedBits, ConstantInt::get(BitsType, 0));
+}
+
+/// Build a test that bit \param BitOffset is set in \param BSI, where
+/// \param BitSetGlobal is a global containing the bits in \param BSI.
+Value *LowerBitSets::createBitSetTest(IRBuilder<> &B, const BitSetInfo &BSI,
+ GlobalVariable *BitSetGlobal,
+ Value *BitOffset) {
+ if (BSI.Bits.size() <= 8) {
+ // If the bit set is sufficiently small, we can avoid a load by bit testing
+ // a constant.
+ IntegerType *BitsTy;
+ if (BSI.Bits.size() <= 4)
+ 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;
+ }
+ 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);
+ }
+}
+
+/// Lower a llvm.bitset.test call to its implementation.
+void LowerBitSets::lowerBitSetCall(
+ CallInst *CI, const BitSetInfo &BSI, GlobalVariable *BitSetGlobal,
+ GlobalVariable *CombinedGlobal,
+ const DenseMap<GlobalVariable *, uint64_t> &GlobalLayout) {
+ Value *Ptr = CI->getArgOperand(0);
+
+ if (BSI.containsValue(DL, GlobalLayout, Ptr)) {
+ CI->replaceAllUsesWith(
+ ConstantInt::getTrue(BitSetGlobal->getParent()->getContext()));
+ CI->eraseFromParent();
+ return;
+ }
+
+ Constant *GlobalAsInt = ConstantExpr::getPtrToInt(CombinedGlobal, IntPtrTy);
+ Constant *OffsetedGlobalAsInt = ConstantExpr::getAdd(
+ GlobalAsInt, ConstantInt::get(IntPtrTy, BSI.ByteOffset));
+
+ BasicBlock *InitialBB = CI->getParent();
+
+ IRBuilder<> B(CI);
+
+ Value *PtrAsInt = B.CreatePtrToInt(Ptr, IntPtrTy);
+
+ if (BSI.isSingleOffset()) {
+ Value *Eq = B.CreateICmpEQ(PtrAsInt, OffsetedGlobalAsInt);
+ CI->replaceAllUsesWith(Eq);
+ CI->eraseFromParent();
+ return;
+ }
+
+ Value *PtrOffset = B.CreateSub(PtrAsInt, OffsetedGlobalAsInt);
+
+ Value *BitOffset;
+ if (BSI.AlignLog2 == 0) {
+ BitOffset = PtrOffset;
+ } else {
+ // We need to check that the offset both falls within our range and is
+ // suitably aligned. We can check both properties at the same time by
+ // performing a right rotate by log2(alignment) followed by an integer
+ // comparison against the bitset size. The rotate will move the lower
+ // order bits that need to be zero into the higher order bits of the
+ // result, causing the comparison to fail if they are nonzero. The rotate
+ // also conveniently gives us a bit offset to use during the load from
+ // the bitset.
+ Value *OffsetSHR =
+ B.CreateLShr(PtrOffset, ConstantInt::get(IntPtrTy, BSI.AlignLog2));
+ Value *OffsetSHL = B.CreateShl(
+ 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);
+
+ 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);
+
+ // 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
+ // we came from the block in which we loaded it.
+ B.SetInsertPoint(CI);
+ PHINode *P = B.CreatePHI(Int1Ty, 2);
+ P->addIncoming(ConstantInt::get(Int1Ty, 0), InitialBB);
+ P->addIncoming(Bit, ThenB.GetInsertBlock());
+
+ CI->replaceAllUsesWith(P);
+ CI->eraseFromParent();
+}
+
+/// 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)
+ GlobalInits.push_back(G->getInitializer());
+ Constant *NewInit = ConstantStruct::getAnon(M.getContext(), GlobalInits);
+ auto CombinedGlobal =
+ new GlobalVariable(M, NewInit->getType(), /*isConstant=*/true,
+ GlobalValue::PrivateLinkage, NewInit);
+
+ const StructLayout *CombinedGlobalLayout =
+ 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);
+
+ // For each bitset in this disjoint set...
+ for (MDString *BS : BitSets) {
+ // Build the bitset.
+ BitSetInfo BSI = buildBitSet(BS, GlobalLayout);
+
+ // 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");
+
+ // Lower each call to llvm.bitset.test for this bitset.
+ for (CallInst *CI : BitSetTestCallSites[BS]) {
+ ++NumBitSetCallsLowered;
+ lowerBitSetCall(CI, BSI, BitSetGlobal, 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) {
+ 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);
+ Globals[I]->eraseFromParent();
+ }
+}
+
+/// Lower all bit sets in this module.
+bool LowerBitSets::buildBitSets(Module &M) {
+ Function *BitSetTestFunc =
+ M.getFunction(Intrinsic::getName(Intrinsic::bitset_test));
+ if (!BitSetTestFunc)
+ return false;
+
+ // Equivalence class set containing bitsets and the globals they reference.
+ // This is used to partition the set of bitsets in the module into disjoint
+ // sets.
+ typedef EquivalenceClasses<PointerUnion<GlobalVariable *, MDString *>>
+ GlobalClassesTy;
+ GlobalClassesTy GlobalClasses;
+
+ for (const Use &U : BitSetTestFunc->uses()) {
+ auto CI = cast<CallInst>(U.getUser());
+
+ auto BitSetMDVal = dyn_cast<MetadataAsValue>(CI->getArgOperand(1));
+ if (!BitSetMDVal || !isa<MDString>(BitSetMDVal->getMetadata()))
+ report_fatal_error(
+ "Second argument of llvm.bitset.test must be metadata string");
+ auto BitSet = cast<MDString>(BitSetMDVal->getMetadata());
+
+ // Add the call site to the list of call sites for this bit set. We also use
+ // BitSetTestCallSites to keep track of whether we have seen this bit set
+ // before. If we have, we don't need to re-add the referenced globals to the
+ // equivalence class.
+ std::pair<DenseMap<MDString *, std::vector<CallInst *>>::iterator,
+ bool> Ins =
+ BitSetTestCallSites.insert(
+ std::make_pair(BitSet, std::vector<CallInst *>()));
+ Ins.first->second.push_back(CI);
+ if (!Ins.second)
+ continue;
+
+ // Add the bitset to the equivalence class.
+ GlobalClassesTy::iterator GCI = GlobalClasses.insert(BitSet);
+ GlobalClassesTy::member_iterator CurSet = GlobalClasses.findLeader(GCI);
+
+ if (!BitSetNM)
+ continue;
+
+ // Verify the bitset metadata and add the referenced globals to the bitset's
+ // equivalence class.
+ for (MDNode *Op : BitSetNM->operands()) {
+ if (Op->getNumOperands() != 3)
+ report_fatal_error(
+ "All operands of llvm.bitsets metadata must have 3 elements");
+
+ if (Op->getOperand(0) != BitSet || !Op->getOperand(1))
+ continue;
+
+ auto OpConstMD = dyn_cast<ConstantAsMetadata>(Op->getOperand(1));
+ if (!OpConstMD)
+ 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");
+
+ auto OffsetConstMD = dyn_cast<ConstantAsMetadata>(Op->getOperand(2));
+ if (!OffsetConstMD)
+ report_fatal_error("Bit set element offset must be a constant");
+ auto OffsetInt = dyn_cast<ConstantInt>(OffsetConstMD->getValue());
+ if (!OffsetInt)
+ report_fatal_error(
+ "Bit set element offset must be an integer constant");
+
+ CurSet = GlobalClasses.unionSets(
+ CurSet, GlobalClasses.findLeader(GlobalClasses.insert(OpGlobal)));
+ }
+ }
+
+ if (GlobalClasses.empty())
+ return false;
+
+ // For each disjoint set we found...
+ for (GlobalClassesTy::iterator I = GlobalClasses.begin(),
+ E = GlobalClasses.end();
+ I != E; ++I) {
+ if (!I->isLeader()) continue;
+
+ ++NumBitSetDisjointSets;
+
+ // Build the list of bitsets and referenced globals in this disjoint set.
+ std::vector<MDString *> BitSets;
+ std::vector<GlobalVariable *> Globals;
+ for (GlobalClassesTy::member_iterator MI = GlobalClasses.member_begin(I);
+ MI != GlobalClasses.member_end(); ++MI) {
+ if ((*MI).is<MDString *>())
+ BitSets.push_back(MI->get<MDString *>());
+ else
+ 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.
+ 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);
+ }
+
+ return true;
+}
+
+bool LowerBitSets::eraseBitSetMetadata(Module &M) {
+ if (!BitSetNM)
+ return false;
+
+ M.eraseNamedMetadata(BitSetNM);
+ return true;
+}
+
+bool LowerBitSets::runOnModule(Module &M) {
+ bool Changed = buildBitSets(M);
+ Changed |= eraseBitSetMetadata(M);
+ return Changed;
+}
diff --git a/llvm/lib/Transforms/IPO/PassManagerBuilder.cpp b/llvm/lib/Transforms/IPO/PassManagerBuilder.cpp
index 9e34a4e..9a75050 100644
--- a/llvm/lib/Transforms/IPO/PassManagerBuilder.cpp
+++ b/llvm/lib/Transforms/IPO/PassManagerBuilder.cpp
@@ -474,6 +474,9 @@
PM.add(createJumpThreadingPass());
+ // Lower bitset metadata to bitsets.
+ PM.add(createLowerBitSetsPass());
+
// Delete basic blocks, which optimization passes may have killed.
PM.add(createCFGSimplificationPass());