#include "llvm/Target/TargetLowering.h"
#include "llvm/Target/TargetMachine.h"
#include "llvm/Target/TargetSubtargetInfo.h"
+#include "llvm/Transforms/Utils/BasicBlockUtils.h"
using namespace llvm;
return new AtomicExpand(TM);
}
-
-namespace {
-
-bool StoreAddressDependOnValue(StoreInst* SI, Value* DepVal);
-Value* GetUntaintedAddress(Value* CurrentAddress);
-
-// The depth we trace down a variable to look for its dependence set.
-const unsigned kDependenceDepth = 4;
-
-// Recursively looks for variables that 'Val' depends on at the given depth
-// 'Depth', and adds them in 'DepSet'. If 'InsertOnlyLeafNodes' is true, only
-// inserts the leaf node values; otherwise, all visited nodes are included in
-// 'DepSet'. Note that constants will be ignored.
-template <typename SetType>
-void recursivelyFindDependence(SetType* DepSet, Value* Val,
- bool InsertOnlyLeafNodes = false,
- unsigned Depth = kDependenceDepth) {
- if (Val == nullptr) {
- return;
- }
- if (!InsertOnlyLeafNodes && !isa<Constant>(Val)) {
- DepSet->insert(Val);
- }
- if (Depth == 0) {
- // Cannot go deeper. Insert the leaf nodes.
- if (InsertOnlyLeafNodes && !isa<Constant>(Val)) {
- DepSet->insert(Val);
- }
- return;
- }
-
- // Go one step further to explore the dependence of the operands.
- Instruction* I = nullptr;
- if ((I = dyn_cast<Instruction>(Val))) {
- if (isa<LoadInst>(I)) {
- // A load is considerd the leaf load of the dependence tree. Done.
- DepSet->insert(Val);
- return;
- } else if (I->isBinaryOp()) {
- BinaryOperator* I = dyn_cast<BinaryOperator>(Val);
- Value *Op0 = I->getOperand(0), *Op1 = I->getOperand(1);
- recursivelyFindDependence(DepSet, Op0, Depth - 1);
- recursivelyFindDependence(DepSet, Op1, Depth - 1);
- } else if (I->isCast()) {
- Value* Op0 = I->getOperand(0);
- recursivelyFindDependence(DepSet, Op0, Depth - 1);
- } else if (I->getOpcode() == Instruction::Select) {
- Value* Op0 = I->getOperand(0);
- Value* Op1 = I->getOperand(1);
- Value* Op2 = I->getOperand(2);
- recursivelyFindDependence(DepSet, Op0, Depth - 1);
- recursivelyFindDependence(DepSet, Op1, Depth - 1);
- recursivelyFindDependence(DepSet, Op2, Depth - 1);
- } else if (I->getOpcode() == Instruction::GetElementPtr) {
- for (unsigned i = 0; i < I->getNumOperands(); i++) {
- recursivelyFindDependence(DepSet, I->getOperand(i), Depth - 1);
- }
- } else if (I->getOpcode() == Instruction::Store) {
- auto* SI = dyn_cast<StoreInst>(Val);
- recursivelyFindDependence(DepSet, SI->getPointerOperand(), Depth - 1);
- recursivelyFindDependence(DepSet, SI->getValueOperand(), Depth - 1);
- } else {
- Value* Op0 = nullptr;
- Value* Op1 = nullptr;
- switch (I->getOpcode()) {
- case Instruction::ICmp:
- case Instruction::FCmp: {
- Op0 = I->getOperand(0);
- Op1 = I->getOperand(1);
- recursivelyFindDependence(DepSet, Op0, Depth - 1);
- recursivelyFindDependence(DepSet, Op1, Depth - 1);
- break;
- }
- default: {
- // Be conservative. Add it and be done with it.
- DepSet->insert(Val);
- return;
- }
- }
- }
- } else if (isa<Constant>(Val)) {
- // Not interested in constant values. Done.
- return;
- } else {
- // Be conservative. Add it and be done with it.
- DepSet->insert(Val);
- return;
- }
-}
-
-// Helper function to create a Cast instruction.
-Value* createCast(IRBuilder<true, NoFolder>& Builder, Value* DepVal,
- Type* TargetIntegerType) {
- Instruction::CastOps CastOp = Instruction::BitCast;
- switch (DepVal->getType()->getTypeID()) {
- case Type::IntegerTyID: {
- CastOp = Instruction::SExt;
- break;
- }
- case Type::FloatTyID:
- case Type::DoubleTyID: {
- CastOp = Instruction::FPToSI;
- break;
- }
- case Type::PointerTyID: {
- CastOp = Instruction::PtrToInt;
- break;
- }
- default: { break; }
- }
-
- return Builder.CreateCast(CastOp, DepVal, TargetIntegerType);
-}
-
-// Given a value, if it's a tainted address, this function returns the
-// instruction that ORs the "dependence value" with the "original address".
-// Otherwise, returns nullptr. This instruction is the first OR instruction
-// where one of its operand is an AND instruction with an operand being 0.
-//
-// E.g., it returns '%4 = or i32 %3, %2' given 'CurrentAddress' is '%5'.
-// %0 = load i32, i32* @y, align 4, !tbaa !1
-// %cmp = icmp ne i32 %0, 42 // <== this is like the condition
-// %1 = sext i1 %cmp to i32
-// %2 = ptrtoint i32* @x to i32
-// %3 = and i32 %1, 0
-// %4 = or i32 %3, %2
-// %5 = inttoptr i32 %4 to i32*
-// store i32 1, i32* %5, align 4
-Instruction* getOrAddress(Value* CurrentAddress) {
- // Is it a cast from integer to pointer type.
- Instruction* OrAddress = nullptr;
- Instruction* AndDep = nullptr;
- Instruction* CastToInt = nullptr;
- Value* ActualAddress = nullptr;
- Constant* ZeroConst = nullptr;
-
- const Instruction* CastToPtr = dyn_cast<Instruction>(CurrentAddress);
- if (CastToPtr && CastToPtr->getOpcode() == Instruction::IntToPtr) {
- // Is it an OR instruction: %1 = or %and, %actualAddress.
- if ((OrAddress = dyn_cast<Instruction>(CastToPtr->getOperand(0))) &&
- OrAddress->getOpcode() == Instruction::Or) {
- // The first operand should be and AND instruction.
- AndDep = dyn_cast<Instruction>(OrAddress->getOperand(0));
- if (AndDep && AndDep->getOpcode() == Instruction::And) {
- // Also make sure its first operand of the "AND" is 0, or the "AND" is
- // marked explicitly by "NoInstCombine".
- if ((ZeroConst = dyn_cast<Constant>(AndDep->getOperand(1))) &&
- ZeroConst->isNullValue()) {
- return OrAddress;
- }
- }
- }
- }
- // Looks like it's not been tainted.
- return nullptr;
-}
-
-// Given a value, if it's a tainted address, this function returns the
-// instruction that taints the "dependence value". Otherwise, returns nullptr.
-// This instruction is the last AND instruction where one of its operand is 0.
-// E.g., it returns '%3' given 'CurrentAddress' is '%5'.
-// %0 = load i32, i32* @y, align 4, !tbaa !1
-// %cmp = icmp ne i32 %0, 42 // <== this is like the condition
-// %1 = sext i1 %cmp to i32
-// %2 = ptrtoint i32* @x to i32
-// %3 = and i32 %1, 0
-// %4 = or i32 %3, %2
-// %5 = inttoptr i32 %4 to i32*
-// store i32 1, i32* %5, align 4
-Instruction* getAndDependence(Value* CurrentAddress) {
- // If 'CurrentAddress' is tainted, get the OR instruction.
- auto* OrAddress = getOrAddress(CurrentAddress);
- if (OrAddress == nullptr) {
- return nullptr;
- }
-
- // No need to check the operands.
- auto* AndDepInst = dyn_cast<Instruction>(OrAddress->getOperand(0));
- assert(AndDepInst);
- return AndDepInst;
-}
-
-// Given a value, if it's a tainted address, this function returns
-// the "dependence value", which is the first operand in the AND instruction.
-// E.g., it returns '%1' given 'CurrentAddress' is '%5'.
-// %0 = load i32, i32* @y, align 4, !tbaa !1
-// %cmp = icmp ne i32 %0, 42 // <== this is like the condition
-// %1 = sext i1 %cmp to i32
-// %2 = ptrtoint i32* @x to i32
-// %3 = and i32 %1, 0
-// %4 = or i32 %3, %2
-// %5 = inttoptr i32 %4 to i32*
-// store i32 1, i32* %5, align 4
-Value* getDependence(Value* CurrentAddress) {
- auto* AndInst = getAndDependence(CurrentAddress);
- if (AndInst == nullptr) {
- return nullptr;
- }
- return AndInst->getOperand(0);
-}
-
-// Given an address that has been tainted, returns the only condition it depends
-// on, if any; otherwise, returns nullptr.
-Value* getConditionDependence(Value* Address) {
- auto* Dep = getDependence(Address);
- if (Dep == nullptr) {
- // 'Address' has not been dependence-tainted.
- return nullptr;
- }
-
- Value* Operand = Dep;
- while (true) {
- auto* Inst = dyn_cast<Instruction>(Operand);
- if (Inst == nullptr) {
- // Non-instruction type does not have condition dependence.
- return nullptr;
- }
- if (Inst->getOpcode() == Instruction::ICmp) {
- return Inst;
- } else {
- if (Inst->getNumOperands() != 1) {
- return nullptr;
- } else {
- Operand = Inst->getOperand(0);
- }
- }
- }
-}
-
-// Conservatively decides whether the dependence set of 'Val1' includes the
-// dependence set of 'Val2'. If 'ExpandSecondValue' is false, we do not expand
-// 'Val2' and use that single value as its dependence set.
-// If it returns true, it means the dependence set of 'Val1' includes that of
-// 'Val2'; otherwise, it only means we cannot conclusively decide it.
-bool dependenceSetInclusion(Value* Val1, Value* Val2,
- int Val1ExpandLevel = 2 * kDependenceDepth,
- int Val2ExpandLevel = kDependenceDepth) {
- typedef SmallSet<Value*, 8> IncludingSet;
- typedef SmallSet<Value*, 4> IncludedSet;
-
- IncludingSet DepSet1;
- IncludedSet DepSet2;
- // Look for more depths for the including set.
- recursivelyFindDependence(&DepSet1, Val1, false /*Insert all visited nodes*/,
- Val1ExpandLevel);
- recursivelyFindDependence(&DepSet2, Val2, true /*Only insert leaf nodes*/,
- Val2ExpandLevel);
-
- auto set_inclusion = [](IncludingSet FullSet, IncludedSet Subset) {
- for (auto* Dep : Subset) {
- if (0 == FullSet.count(Dep)) {
- return false;
- }
- }
- return true;
- };
- bool inclusion = set_inclusion(DepSet1, DepSet2);
- DEBUG(dbgs() << "[dependenceSetInclusion]: " << inclusion << "\n");
- DEBUG(dbgs() << "Including set for: " << *Val1 << "\n");
- DEBUG(for (const auto* Dep : DepSet1) { dbgs() << "\t\t" << *Dep << "\n"; });
- DEBUG(dbgs() << "Included set for: " << *Val2 << "\n");
- DEBUG(for (const auto* Dep : DepSet2) { dbgs() << "\t\t" << *Dep << "\n"; });
-
- return inclusion;
-}
-
-// Recursively iterates through the operands spawned from 'DepVal'. If there
-// exists a single value that 'DepVal' only depends on, we call that value the
-// root dependence of 'DepVal' and return it. Otherwise, return 'DepVal'.
-Value* getRootDependence(Value* DepVal) {
- SmallSet<Value*, 8> DepSet;
- for (unsigned depth = kDependenceDepth; depth > 0; --depth) {
- recursivelyFindDependence(&DepSet, DepVal, true /*Only insert leaf nodes*/,
- depth);
- if (DepSet.size() == 1) {
- return *DepSet.begin();
- }
- DepSet.clear();
- }
- return DepVal;
-}
-
-// This function actually taints 'DepVal' to the address to 'SI'. If the
-// address
-// of 'SI' already depends on whatever 'DepVal' depends on, this function
-// doesn't do anything and returns false. Otherwise, returns true.
-//
-// This effect forces the store and any stores that comes later to depend on
-// 'DepVal'. For example, we have a condition "cond", and a store instruction
-// "s: STORE addr, val". If we want "s" (and any later store) to depend on
-// "cond", we do the following:
-// %conv = sext i1 %cond to i32
-// %addrVal = ptrtoint i32* %addr to i32
-// %andCond = and i32 conv, 0;
-// %orAddr = or i32 %andCond, %addrVal;
-// %NewAddr = inttoptr i32 %orAddr to i32*;
-//
-// This is a more concrete example:
-// ------
-// %0 = load i32, i32* @y, align 4, !tbaa !1
-// %cmp = icmp ne i32 %0, 42 // <== this is like the condition
-// %1 = sext i1 %cmp to i32
-// %2 = ptrtoint i32* @x to i32
-// %3 = and i32 %1, 0
-// %4 = or i32 %3, %2
-// %5 = inttoptr i32 %4 to i32*
-// store i32 1, i32* %5, align 4
-bool taintStoreAddress(StoreInst* SI, Value* DepVal,
- const char* calling_func = __builtin_FUNCTION()) {
- DEBUG(dbgs() << "Called from " << calling_func << '\n');
- IRBuilder<true, NoFolder> Builder(SI);
- BasicBlock* BB = SI->getParent();
- Value* Address = SI->getPointerOperand();
- Type* TargetIntegerType =
- IntegerType::get(Address->getContext(),
- BB->getModule()->getDataLayout().getPointerSizeInBits());
-
- // Does SI's address already depends on whatever 'DepVal' depends on?
- if (StoreAddressDependOnValue(SI, DepVal)) {
- return false;
- }
-
- // Figure out if there's a root variable 'DepVal' depends on. For example, we
- // can extract "getelementptr inbounds %struct, %struct* %0, i64 0, i32 123"
- // to be "%struct* %0" since all other operands are constant.
- DepVal = getRootDependence(DepVal);
-
- // Is this already a dependence-tainted store?
- Value* OldDep = getDependence(Address);
- if (OldDep) {
- // The address of 'SI' has already been tainted. Just need to absorb the
- // DepVal to the existing dependence in the address of SI.
- Instruction* AndDep = getAndDependence(Address);
- IRBuilder<true, NoFolder> Builder(AndDep);
- Value* NewDep = nullptr;
- if (DepVal->getType() == AndDep->getType()) {
- NewDep = Builder.CreateAnd(OldDep, DepVal);
- } else {
- NewDep = Builder.CreateAnd(
- OldDep, createCast(Builder, DepVal, TargetIntegerType));
- }
-
- auto* NewDepInst = dyn_cast<Instruction>(NewDep);
-
- // Use the new AND instruction as the dependence
- AndDep->setOperand(0, NewDep);
- return true;
- }
-
- // SI's address has not been tainted. Now taint it with 'DepVal'.
- Value* CastDepToInt = createCast(Builder, DepVal, TargetIntegerType);
- Value* PtrToIntCast = Builder.CreatePtrToInt(Address, TargetIntegerType);
- Value* AndDepVal =
- Builder.CreateAnd(CastDepToInt, ConstantInt::get(TargetIntegerType, 0));
- auto AndInst = dyn_cast<Instruction>(AndDepVal);
- // XXX-comment: The original IR InstCombiner would change our and instruction
- // to a select and then the back end optimize the condition out. We attach a
- // flag to instructions and set it here to inform the InstCombiner to not to
- // touch this and instruction at all.
- Value* OrAddr = Builder.CreateOr(AndDepVal, PtrToIntCast);
- Value* NewAddr = Builder.CreateIntToPtr(OrAddr, Address->getType());
-
- DEBUG(dbgs() << "[taintStoreAddress]\n"
- << "Original store: " << *SI << '\n');
- SI->setOperand(1, NewAddr);
-
- // Debug output.
- DEBUG(dbgs() << "\tTargetIntegerType: " << *TargetIntegerType << '\n'
- << "\tCast dependence value to integer: " << *CastDepToInt
- << '\n'
- << "\tCast address to integer: " << *PtrToIntCast << '\n'
- << "\tAnd dependence value: " << *AndDepVal << '\n'
- << "\tOr address: " << *OrAddr << '\n'
- << "\tCast or instruction to address: " << *NewAddr << "\n\n");
-
- return true;
-}
-
-// Looks for the previous store in the if block --- 'BrBB', which makes the
-// speculative store 'StoreToHoist' safe.
-Value* getSpeculativeStoreInPrevBB(StoreInst* StoreToHoist, BasicBlock* BrBB) {
- assert(StoreToHoist && "StoreToHoist must be a real store");
-
- Value* StorePtr = StoreToHoist->getPointerOperand();
-
- // Look for a store to the same pointer in BrBB.
- for (BasicBlock::reverse_iterator RI = BrBB->rbegin(), RE = BrBB->rend();
- RI != RE; ++RI) {
- Instruction* CurI = &*RI;
-
- StoreInst* SI = dyn_cast<StoreInst>(CurI);
- // Found the previous store make sure it stores to the same location.
- // XXX-update: If the previous store's original untainted address are the
- // same as 'StorePtr', we are also good to hoist the store.
- if (SI && (SI->getPointerOperand() == StorePtr ||
- GetUntaintedAddress(SI->getPointerOperand()) == StorePtr)) {
- // Found the previous store, return its value operand.
- return SI;
- }
- }
-
- assert(false &&
- "We should not reach here since this store is safe to speculate");
-}
-
-// XXX-comment: Returns true if it changes the code, false otherwise (the branch
-// condition already depends on 'DepVal'.
-bool taintConditionalBranch(BranchInst* BI, Value* DepVal) {
- assert(BI->isConditional());
- auto* Cond = BI->getOperand(0);
- if (dependenceSetInclusion(Cond, DepVal)) {
- // The dependence/ordering is self-evident.
- return false;
- }
-
- IRBuilder<true, NoFolder> Builder(BI);
- auto* AndDep =
- Builder.CreateAnd(DepVal, ConstantInt::get(DepVal->getType(), 0));
- auto* TruncAndDep =
- Builder.CreateTrunc(AndDep, IntegerType::get(DepVal->getContext(), 1));
- auto* OrCond = Builder.CreateOr(TruncAndDep, Cond);
- BI->setOperand(0, OrCond);
-
- // Debug output.
- DEBUG(dbgs() << "\tTainted branch condition:\n" << *BI->getParent());
-
- return true;
-}
-
-// XXX-update: For a relaxed load 'LI', find the first immediate atomic store or
-// the first conditional branch. Returns nullptr if there's no such immediately
-// following store/branch instructions, which we can only enforce the load with
-// 'acquire'.
-Instruction* findFirstStoreCondBranchInst(LoadInst* LI) {
- // In some situations, relaxed loads can be left as is:
- // 1. The relaxed load is used to calculate the address of the immediate
- // following store;
- // 2. The relaxed load is used as a condition in the immediate following
- // condition, and there are no stores in between. This is actually quite
- // common. E.g.,
- // int r1 = x.load(relaxed);
- // if (r1 != 0) {
- // y.store(1, relaxed);
- // }
- // However, in this function, we don't deal with them directly. Instead, we
- // just find the immediate following store/condition branch and return it.
-
- auto* BB = LI->getParent();
- auto BE = BB->end();
- auto BBI = BasicBlock::iterator(LI);
- BBI++;
- while (true) {
- for (; BBI != BE; BBI++) {
- auto* Inst = dyn_cast<Instruction>(&*BBI);
- if (Inst == nullptr) {
- continue;
- }
- if (Inst->getOpcode() == Instruction::Store) {
- return Inst;
- } else if (Inst->getOpcode() == Instruction::Br) {
- auto* BrInst = dyn_cast<BranchInst>(Inst);
- if (BrInst->isConditional()) {
- return Inst;
- } else {
- // Reinitialize iterators with the destination of the unconditional
- // branch.
- BB = BrInst->getSuccessor(0);
- BBI = BB->begin();
- BE = BB->end();
- break;
- }
- }
- }
- if (BBI == BE) {
- return nullptr;
- }
- }
-}
-
-// XXX-comment: Returns whether the code has been changed.
-bool taintMonotonicLoads(const SmallVector<LoadInst*, 1>& MonotonicLoadInsts) {
- bool Changed = false;
- for (auto* LI : MonotonicLoadInsts) {
- auto* FirstInst = findFirstStoreCondBranchInst(LI);
- if (FirstInst == nullptr) {
- // We don't seem to be able to taint a following store/conditional branch
- // instruction. Simply make it acquire.
- DEBUG(dbgs() << "[RelaxedLoad]: Transformed to acquire load\n"
- << *LI << "\n");
- LI->setOrdering(Acquire);
- Changed = true;
- continue;
- }
- // Taint 'FirstInst', which could be a store or a condition branch
- // instruction.
- if (FirstInst->getOpcode() == Instruction::Store) {
- Changed |= taintStoreAddress(dyn_cast<StoreInst>(FirstInst), LI);
- } else if (FirstInst->getOpcode() == Instruction::Br) {
- Changed |= taintConditionalBranch(dyn_cast<BranchInst>(FirstInst), LI);
- } else {
- assert(false && "findFirstStoreCondBranchInst() should return a "
- "store/condition branch instruction");
- }
- }
- return Changed;
-}
-
-/**** Implementations of public methods for dependence tainting ****/
-Value* GetUntaintedAddress(Value* CurrentAddress) {
- auto* OrAddress = getOrAddress(CurrentAddress);
- if (OrAddress == nullptr) {
- // Is it tainted by a select instruction?
- auto* Inst = dyn_cast<Instruction>(CurrentAddress);
- if (nullptr != Inst && Inst->getOpcode() == Instruction::Select) {
- // A selection instruction.
- if (Inst->getOperand(1) == Inst->getOperand(2)) {
- return Inst->getOperand(1);
- }
- }
-
- return CurrentAddress;
- }
- Value* ActualAddress = nullptr;
-
- auto* CastToInt = dyn_cast<Instruction>(OrAddress->getOperand(1));
- if (CastToInt && CastToInt->getOpcode() == Instruction::PtrToInt) {
- return CastToInt->getOperand(0);
- } else {
- // This should be a IntToPtr constant expression.
- ConstantExpr* PtrToIntExpr =
- dyn_cast<ConstantExpr>(OrAddress->getOperand(1));
- if (PtrToIntExpr && PtrToIntExpr->getOpcode() == Instruction::PtrToInt) {
- return PtrToIntExpr->getOperand(0);
- }
- }
-
- // Looks like it's not been dependence-tainted. Returns itself.
- return CurrentAddress;
-}
-
-MemoryLocation GetUntaintedMemoryLocation(StoreInst* SI) {
- AAMDNodes AATags;
- SI->getAAMetadata(AATags);
- const auto& DL = SI->getModule()->getDataLayout();
- const auto* OriginalAddr = GetUntaintedAddress(SI->getPointerOperand());
- DEBUG(if (OriginalAddr != SI->getPointerOperand()) {
- dbgs() << "[GetUntaintedMemoryLocation]\n"
- << "Storing address: " << *SI->getPointerOperand()
- << "\nUntainted address: " << *OriginalAddr << "\n";
- });
- return MemoryLocation(OriginalAddr,
- DL.getTypeStoreSize(SI->getValueOperand()->getType()),
- AATags);
-}
-
-bool TaintDependenceToStore(StoreInst* SI, Value* DepVal) {
- if (dependenceSetInclusion(SI, DepVal)) {
- return false;
- }
-
- bool tainted = taintStoreAddress(SI, DepVal);
- assert(tainted);
- return tainted;
-}
-
-bool TaintDependenceToStoreAddress(StoreInst* SI, Value* DepVal) {
- if (dependenceSetInclusion(SI->getPointerOperand(), DepVal)) {
- return false;
- }
-
- bool tainted = taintStoreAddress(SI, DepVal);
- assert(tainted);
- return tainted;
-}
-
-bool CompressTaintedStore(BasicBlock* BB) {
- // This function looks for windows of adajcent stores in 'BB' that satisfy the
- // following condition (and then do optimization):
- // *Addr(d1) = v1, d1 is a condition and is the only dependence the store's
- // address depends on && Dep(v1) includes Dep(d1);
- // *Addr(d2) = v2, d2 is a condition and is the only dependnece the store's
- // address depends on && Dep(v2) includes Dep(d2) &&
- // Dep(d2) includes Dep(d1);
- // ...
- // *Addr(dN) = vN, dN is a condition and is the only dependence the store's
- // address depends on && Dep(dN) includes Dep(d"N-1").
- //
- // As a result, Dep(dN) includes [Dep(d1) V ... V Dep(d"N-1")], so we can
- // safely transform the above to the following. In between these stores, we
- // can omit untainted stores to the same address 'Addr' since they internally
- // have dependence on the previous stores on the same address.
- // =>
- // *Addr = v1
- // *Addr = v2
- // *Addr(d3) = v3
- for (auto BI = BB->begin(), BE = BB->end(); BI != BE; BI++) {
- // Look for the first store in such a window of adajacent stores.
- auto* FirstSI = dyn_cast<StoreInst>(&*BI);
- if (!FirstSI) {
- continue;
- }
-
- // The first store in the window must be tainted.
- auto* UntaintedAddress = GetUntaintedAddress(FirstSI->getPointerOperand());
- if (UntaintedAddress == FirstSI->getPointerOperand()) {
- continue;
- }
-
- // The first store's address must directly depend on and only depend on a
- // condition.
- auto* FirstSIDepCond = getConditionDependence(FirstSI->getPointerOperand());
- if (nullptr == FirstSIDepCond) {
- continue;
- }
-
- // Dep(first store's storing value) includes Dep(tainted dependence).
- if (!dependenceSetInclusion(FirstSI->getValueOperand(), FirstSIDepCond)) {
- continue;
- }
-
- // Look for subsequent stores to the same address that satisfy the condition
- // of "compressing the dependence".
- SmallVector<StoreInst*, 8> AdajacentStores;
- AdajacentStores.push_back(FirstSI);
- auto BII = BasicBlock::iterator(FirstSI);
- for (BII++; BII != BE; BII++) {
- auto* CurrSI = dyn_cast<StoreInst>(&*BII);
- if (!CurrSI) {
- if (BII->mayHaveSideEffects()) {
- // Be conservative. Instructions with side effects are similar to
- // stores.
- break;
- }
- continue;
- }
-
- auto* OrigAddress = GetUntaintedAddress(CurrSI->getPointerOperand());
- auto* CurrSIDepCond = getConditionDependence(CurrSI->getPointerOperand());
- // All other stores must satisfy either:
- // A. 'CurrSI' is an untainted store to the same address, or
- // B. the combination of the following 5 subconditions:
- // 1. Tainted;
- // 2. Untainted address is the same as the group's address;
- // 3. The address is tainted with a sole value which is a condition;
- // 4. The storing value depends on the condition in 3.
- // 5. The condition in 3 depends on the previous stores dependence
- // condition.
-
- // Condition A. Should ignore this store directly.
- if (OrigAddress == CurrSI->getPointerOperand() &&
- OrigAddress == UntaintedAddress) {
- continue;
- }
- // Check condition B.
- Value* Cond = nullptr;
- if (OrigAddress == CurrSI->getPointerOperand() ||
- OrigAddress != UntaintedAddress || CurrSIDepCond == nullptr ||
- !dependenceSetInclusion(CurrSI->getValueOperand(), CurrSIDepCond)) {
- // Check condition 1, 2, 3 & 4.
- break;
- }
-
- // Check condition 5.
- StoreInst* PrevSI = AdajacentStores[AdajacentStores.size() - 1];
- auto* PrevSIDepCond = getConditionDependence(PrevSI->getPointerOperand());
- assert(PrevSIDepCond &&
- "Store in the group must already depend on a condtion");
- if (!dependenceSetInclusion(CurrSIDepCond, PrevSIDepCond)) {
- break;
- }
-
- AdajacentStores.push_back(CurrSI);
- }
-
- if (AdajacentStores.size() == 1) {
- // The outer loop should keep looking from the next store.
- continue;
- }
-
- // Now we have such a group of tainted stores to the same address.
- DEBUG(dbgs() << "[CompressTaintedStore]\n");
- DEBUG(dbgs() << "Original BB\n");
- DEBUG(dbgs() << *BB << '\n');
- auto* LastSI = AdajacentStores[AdajacentStores.size() - 1];
- for (int i = 0; i < AdajacentStores.size() - 1; ++i) {
- auto* SI = AdajacentStores[i];
-
- // Use the original address for stores before the last one.
- SI->setOperand(1, UntaintedAddress);
-
- DEBUG(dbgs() << "Store address has been reversed: " << *SI << '\n';);
- }
- // XXX-comment: Try to make the last store use fewer registers.
- // If LastSI's storing value is a select based on the condition with which
- // its address is tainted, transform the tainted address to a select
- // instruction, as follows:
- // r1 = Select Cond ? A : B
- // r2 = Cond & 0
- // r3 = Addr | r2
- // *r3 = r1
- // ==>
- // r1 = Select Cond ? A : B
- // r2 = Select Cond ? Addr : Addr
- // *r2 = r1
- // The idea is that both Select instructions depend on the same condition,
- // so hopefully the backend can generate two cmov instructions for them (and
- // this saves the number of registers needed).
- auto* LastSIDep = getConditionDependence(LastSI->getPointerOperand());
- auto* LastSIValue = dyn_cast<Instruction>(LastSI->getValueOperand());
- if (LastSIValue && LastSIValue->getOpcode() == Instruction::Select &&
- LastSIValue->getOperand(0) == LastSIDep) {
- // XXX-comment: Maybe it's better for us to just leave it as an and/or
- // dependence pattern.
- // /*
- IRBuilder<true, NoFolder> Builder(LastSI);
- auto* Address =
- Builder.CreateSelect(LastSIDep, UntaintedAddress, UntaintedAddress);
- LastSI->setOperand(1, Address);
- DEBUG(dbgs() << "The last store becomes :" << *LastSI << "\n\n";);
- // */
- }
- }
-
- return true;
-}
-
-bool PassDependenceToStore(Value* OldAddress, StoreInst* NewStore) {
- Value* OldDep = getDependence(OldAddress);
- // Return false when there's no dependence to pass from the OldAddress.
- if (!OldDep) {
- return false;
- }
-
- // No need to pass the dependence to NewStore's address if it already depends
- // on whatever 'OldAddress' depends on.
- if (StoreAddressDependOnValue(NewStore, OldDep)) {
- return false;
- }
- return taintStoreAddress(NewStore, OldAddress);
-}
-
-SmallSet<Value*, 8> FindDependence(Value* Val) {
- SmallSet<Value*, 8> DepSet;
- recursivelyFindDependence(&DepSet, Val, true /*Only insert leaf nodes*/);
- return DepSet;
-}
-
-bool StoreAddressDependOnValue(StoreInst* SI, Value* DepVal) {
- return dependenceSetInclusion(SI->getPointerOperand(), DepVal);
-}
-
-bool StoreDependOnValue(StoreInst* SI, Value* Dep) {
- return dependenceSetInclusion(SI, Dep);
-}
-
-} // namespace
-
-
bool AtomicExpand::runOnFunction(Function &F) {
if (!TM || !TM->getSubtargetImpl(F)->enableAtomicExpand())
return false;
if (TLI->getInsertFencesForAtomic()) {
if (LI && isAtLeastAcquire(LI->getOrdering())) {
FenceOrdering = LI->getOrdering();
- LI->setOrdering(Monotonic);
+// AddFakeConditionalBranch(
IsStore = false;
IsLoad = true;
} else if (SI && isAtLeastRelease(SI->getOrdering())) {
}
}
- MadeChange |= taintMonotonicLoads(MonotonicLoadInsts);
-
return MadeChange;
}
projects / oota-llvm.git / blobdiff