diff options
author | Dimitry Andric <dim@FreeBSD.org> | 2014-11-24 09:08:18 +0000 |
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committer | Dimitry Andric <dim@FreeBSD.org> | 2014-11-24 09:08:18 +0000 |
commit | 5ca98fd98791947eba83a1ed3f2c8191ef7afa6c (patch) | |
tree | f5944309621cee4fe0976be6f9ac619b7ebfc4c2 /lib/IR/Value.cpp | |
parent | 68bcb7db193e4bc81430063148253d30a791023e (diff) | |
download | src-5ca98fd98791947eba83a1ed3f2c8191ef7afa6c.tar.gz src-5ca98fd98791947eba83a1ed3f2c8191ef7afa6c.zip |
Notes
Diffstat (limited to 'lib/IR/Value.cpp')
-rw-r--r-- | lib/IR/Value.cpp | 164 |
1 files changed, 131 insertions, 33 deletions
diff --git a/lib/IR/Value.cpp b/lib/IR/Value.cpp index 62a3b31c18b2..1ab2183b6565 100644 --- a/lib/IR/Value.cpp +++ b/lib/IR/Value.cpp @@ -15,20 +15,22 @@ #include "LLVMContextImpl.h" #include "llvm/ADT/DenseMap.h" #include "llvm/ADT/SmallString.h" +#include "llvm/IR/CallSite.h" #include "llvm/IR/Constant.h" #include "llvm/IR/Constants.h" +#include "llvm/IR/DataLayout.h" #include "llvm/IR/DerivedTypes.h" +#include "llvm/IR/GetElementPtrTypeIterator.h" #include "llvm/IR/InstrTypes.h" #include "llvm/IR/Instructions.h" +#include "llvm/IR/LeakDetector.h" #include "llvm/IR/Module.h" #include "llvm/IR/Operator.h" +#include "llvm/IR/ValueHandle.h" #include "llvm/IR/ValueSymbolTable.h" #include "llvm/Support/Debug.h" #include "llvm/Support/ErrorHandling.h" -#include "llvm/Support/GetElementPtrTypeIterator.h" -#include "llvm/Support/LeakDetector.h" #include "llvm/Support/ManagedStatic.h" -#include "llvm/Support/ValueHandle.h" #include <algorithm> using namespace llvm; @@ -38,13 +40,12 @@ using namespace llvm; static inline Type *checkType(Type *Ty) { assert(Ty && "Value defined with a null type: Error!"); - return const_cast<Type*>(Ty); + return Ty; } Value::Value(Type *ty, unsigned scid) - : SubclassID(scid), HasValueHandle(0), - SubclassOptionalData(0), SubclassData(0), VTy((Type*)checkType(ty)), - UseList(0), Name(0) { + : VTy(checkType(ty)), UseList(nullptr), Name(nullptr), SubclassID(scid), + HasValueHandle(0), SubclassOptionalData(0), SubclassData(0) { // FIXME: Why isn't this in the subclass gunk?? // Note, we cannot call isa<CallInst> before the CallInst has been // constructed. @@ -119,7 +120,7 @@ bool Value::isUsedInBasicBlock(const BasicBlock *BB) const { // Scan both lists simultaneously until one is exhausted. This limits the // search to the shorter list. BasicBlock::const_iterator BI = BB->begin(), BE = BB->end(); - const_use_iterator UI = use_begin(), UE = use_end(); + const_user_iterator UI = user_begin(), UE = user_end(); for (; BI != BE && UI != UE; ++BI, ++UI) { // Scan basic block: Check if this Value is used by the instruction at BI. if (std::find(BI->op_begin(), BI->op_end(), this) != BI->op_end()) @@ -141,7 +142,7 @@ unsigned Value::getNumUses() const { } static bool getSymTab(Value *V, ValueSymbolTable *&ST) { - ST = 0; + ST = nullptr; if (Instruction *I = dyn_cast<Instruction>(V)) { if (BasicBlock *P = I->getParent()) if (Function *PP = P->getParent()) @@ -182,6 +183,8 @@ void Value::setName(const Twine &NewName) { SmallString<256> NameData; StringRef NameRef = NewName.toStringRef(NameData); + assert(NameRef.find_first_of(0) == StringRef::npos && + "Null bytes are not allowed in names"); // Name isn't changing? if (getName() == NameRef) @@ -201,7 +204,7 @@ void Value::setName(const Twine &NewName) { if (NameRef.empty()) { // Free the name for this value. Name->Destroy(); - Name = 0; + Name = nullptr; return; } @@ -212,7 +215,7 @@ void Value::setName(const Twine &NewName) { // then reallocated. // Create the new name. - Name = ValueName::Create(NameRef.begin(), NameRef.end()); + Name = ValueName::Create(NameRef); Name->setValue(this); return; } @@ -223,7 +226,7 @@ void Value::setName(const Twine &NewName) { // Remove old name. ST->removeValueName(Name); Name->Destroy(); - Name = 0; + Name = nullptr; if (NameRef.empty()) return; @@ -239,7 +242,7 @@ void Value::setName(const Twine &NewName) { void Value::takeName(Value *V) { assert(SubclassID != MDStringVal && "Cannot take the name of an MDString!"); - ValueSymbolTable *ST = 0; + ValueSymbolTable *ST = nullptr; // If this value has a name, drop it. if (hasName()) { // Get the symtab this is in. @@ -254,7 +257,7 @@ void Value::takeName(Value *V) { if (ST) ST->removeValueName(Name); Name->Destroy(); - Name = 0; + Name = nullptr; } // Now we know that this has no name. @@ -281,7 +284,7 @@ void Value::takeName(Value *V) { if (ST == VST) { // Take the name! Name = V->Name; - V->Name = 0; + V->Name = nullptr; Name->setValue(this); return; } @@ -292,17 +295,52 @@ void Value::takeName(Value *V) { if (VST) VST->removeValueName(V->Name); Name = V->Name; - V->Name = 0; + V->Name = nullptr; Name->setValue(this); if (ST) ST->reinsertValue(this); } +#ifndef NDEBUG +static bool contains(SmallPtrSet<ConstantExpr *, 4> &Cache, ConstantExpr *Expr, + Constant *C) { + if (!Cache.insert(Expr)) + return false; + + for (auto &O : Expr->operands()) { + if (O == C) + return true; + auto *CE = dyn_cast<ConstantExpr>(O); + if (!CE) + continue; + if (contains(Cache, CE, C)) + return true; + } + return false; +} + +static bool contains(Value *Expr, Value *V) { + if (Expr == V) + return true; + + auto *C = dyn_cast<Constant>(V); + if (!C) + return false; + + auto *CE = dyn_cast<ConstantExpr>(Expr); + if (!CE) + return false; + + SmallPtrSet<ConstantExpr *, 4> Cache; + return contains(Cache, CE, C); +} +#endif void Value::replaceAllUsesWith(Value *New) { assert(New && "Value::replaceAllUsesWith(<null>) is invalid!"); - assert(New != this && "this->replaceAllUsesWith(this) is NOT valid!"); + assert(!contains(New, this) && + "this->replaceAllUsesWith(expr(this)) is NOT valid!"); assert(New->getType() == getType() && "replaceAllUses of value with new value of different type!"); @@ -314,7 +352,7 @@ void Value::replaceAllUsesWith(Value *New) { Use &U = *UseList; // Must handle Constants specially, we cannot call replaceUsesOfWith on a // constant because they are uniqued. - if (Constant *C = dyn_cast<Constant>(U.getUser())) { + if (auto *C = dyn_cast<Constant>(U.getUser())) { if (!isa<GlobalValue>(C)) { C->replaceUsesOfWithOnConstant(this, New, &U); continue; @@ -417,7 +455,8 @@ Value *Value::stripAndAccumulateInBoundsConstantOffsets(const DataLayout &DL, return V; Offset = GEPOffset; V = GEP->getPointerOperand(); - } else if (Operator::getOpcode(V) == Instruction::BitCast) { + } else if (Operator::getOpcode(V) == Instruction::BitCast || + Operator::getOpcode(V) == Instruction::AddrSpaceCast) { V = cast<Operator>(V)->getOperand(0); } else if (GlobalAlias *GA = dyn_cast<GlobalAlias>(V)) { V = GA->getAliasee(); @@ -436,32 +475,67 @@ Value *Value::stripInBoundsOffsets() { /// isDereferenceablePointer - Test if this value is always a pointer to /// allocated and suitably aligned memory for a simple load or store. -static bool isDereferenceablePointer(const Value *V, +static bool isDereferenceablePointer(const Value *V, const DataLayout *DL, SmallPtrSet<const Value *, 32> &Visited) { // Note that it is not safe to speculate into a malloc'd region because // malloc may return null. - // It's also not always safe to follow a bitcast, for example: - // bitcast i8* (alloca i8) to i32* - // would result in a 4-byte load from a 1-byte alloca. Some cases could - // be handled using DataLayout to check sizes and alignments though. // These are obviously ok. if (isa<AllocaInst>(V)) return true; + // It's not always safe to follow a bitcast, for example: + // bitcast i8* (alloca i8) to i32* + // would result in a 4-byte load from a 1-byte alloca. However, + // if we're casting from a pointer from a type of larger size + // to a type of smaller size (or the same size), and the alignment + // is at least as large as for the resulting pointer type, then + // we can look through the bitcast. + if (DL) + if (const BitCastInst* BC = dyn_cast<BitCastInst>(V)) { + Type *STy = BC->getSrcTy()->getPointerElementType(), + *DTy = BC->getDestTy()->getPointerElementType(); + if (STy->isSized() && DTy->isSized() && + (DL->getTypeStoreSize(STy) >= + DL->getTypeStoreSize(DTy)) && + (DL->getABITypeAlignment(STy) >= + DL->getABITypeAlignment(DTy))) + return isDereferenceablePointer(BC->getOperand(0), DL, Visited); + } + // Global variables which can't collapse to null are ok. if (const GlobalVariable *GV = dyn_cast<GlobalVariable>(V)) return !GV->hasExternalWeakLinkage(); - // byval arguments are ok. - if (const Argument *A = dyn_cast<Argument>(V)) - return A->hasByValAttr(); + // byval arguments are okay. Arguments specifically marked as + // dereferenceable are okay too. + if (const Argument *A = dyn_cast<Argument>(V)) { + if (A->hasByValAttr()) + return true; + else if (uint64_t Bytes = A->getDereferenceableBytes()) { + Type *Ty = V->getType()->getPointerElementType(); + if (Ty->isSized() && DL && DL->getTypeStoreSize(Ty) <= Bytes) + return true; + } + + return false; + } + + // Return values from call sites specifically marked as dereferenceable are + // also okay. + if (ImmutableCallSite CS = V) { + if (uint64_t Bytes = CS.getDereferenceableBytes(0)) { + Type *Ty = V->getType()->getPointerElementType(); + if (Ty->isSized() && DL && DL->getTypeStoreSize(Ty) <= Bytes) + return true; + } + } // For GEPs, determine if the indexing lands within the allocated object. if (const GEPOperator *GEP = dyn_cast<GEPOperator>(V)) { // Conservatively require that the base pointer be fully dereferenceable. if (!Visited.insert(GEP->getOperand(0))) return false; - if (!isDereferenceablePointer(GEP->getOperand(0), Visited)) + if (!isDereferenceablePointer(GEP->getOperand(0), DL, Visited)) return false; // Check the indices. gep_type_iterator GTI = gep_type_begin(GEP); @@ -491,15 +565,39 @@ static bool isDereferenceablePointer(const Value *V, return true; } + if (const AddrSpaceCastInst *ASC = dyn_cast<AddrSpaceCastInst>(V)) + return isDereferenceablePointer(ASC->getOperand(0), DL, Visited); + // If we don't know, assume the worst. return false; } /// isDereferenceablePointer - Test if this value is always a pointer to /// allocated and suitably aligned memory for a simple load or store. -bool Value::isDereferenceablePointer() const { +bool Value::isDereferenceablePointer(const DataLayout *DL) const { + // When dereferenceability information is provided by a dereferenceable + // attribute, we know exactly how many bytes are dereferenceable. If we can + // determine the exact offset to the attributed variable, we can use that + // information here. + Type *Ty = getType()->getPointerElementType(); + if (Ty->isSized() && DL) { + APInt Offset(DL->getTypeStoreSizeInBits(getType()), 0); + const Value *BV = stripAndAccumulateInBoundsConstantOffsets(*DL, Offset); + + APInt DerefBytes(Offset.getBitWidth(), 0); + if (const Argument *A = dyn_cast<Argument>(BV)) + DerefBytes = A->getDereferenceableBytes(); + else if (ImmutableCallSite CS = BV) + DerefBytes = CS.getDereferenceableBytes(0); + + if (DerefBytes.getBoolValue() && Offset.isNonNegative()) { + if (DerefBytes.uge(Offset + DL->getTypeStoreSize(Ty))) + return true; + } + } + SmallPtrSet<const Value *, 32> Visited; - return ::isDereferenceablePointer(this, Visited); + return ::isDereferenceablePointer(this, DL, Visited); } /// DoPHITranslation - If this value is a PHI node with CurBB as its parent, @@ -555,7 +653,7 @@ void ValueHandleBase::AddToUseList() { // If this value already has a ValueHandle, then it must be in the // ValueHandles map already. ValueHandleBase *&Entry = pImpl->ValueHandles[VP.getPointer()]; - assert(Entry != 0 && "Value doesn't have any handles?"); + assert(Entry && "Value doesn't have any handles?"); AddToExistingUseList(&Entry); return; } @@ -569,7 +667,7 @@ void ValueHandleBase::AddToUseList() { const void *OldBucketPtr = Handles.getPointerIntoBucketsArray(); ValueHandleBase *&Entry = Handles[VP.getPointer()]; - assert(Entry == 0 && "Value really did already have handles?"); + assert(!Entry && "Value really did already have handles?"); AddToExistingUseList(&Entry); VP.getPointer()->HasValueHandle = true; @@ -650,7 +748,7 @@ void ValueHandleBase::ValueIsDeleted(Value *V) { break; case Weak: // Weak just goes to null, which will unlink it from the list. - Entry->operator=(0); + Entry->operator=(nullptr); break; case Callback: // Forward to the subclass's implementation. |