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Diffstat (limited to 'llvm/lib/Analysis/MemoryBuiltins.cpp')
| -rw-r--r-- | llvm/lib/Analysis/MemoryBuiltins.cpp | 1051 |
1 files changed, 1051 insertions, 0 deletions
diff --git a/llvm/lib/Analysis/MemoryBuiltins.cpp b/llvm/lib/Analysis/MemoryBuiltins.cpp new file mode 100644 index 000000000000..172c86eb4646 --- /dev/null +++ b/llvm/lib/Analysis/MemoryBuiltins.cpp @@ -0,0 +1,1051 @@ +//===- MemoryBuiltins.cpp - Identify calls to memory builtins -------------===// +// +// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions. +// See https://llvm.org/LICENSE.txt for license information. +// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception +// +//===----------------------------------------------------------------------===// +// +// This family of functions identifies calls to builtin functions that allocate +// or free memory. +// +//===----------------------------------------------------------------------===// + +#include "llvm/Analysis/MemoryBuiltins.h" +#include "llvm/ADT/APInt.h" +#include "llvm/ADT/None.h" +#include "llvm/ADT/Optional.h" +#include "llvm/ADT/STLExtras.h" +#include "llvm/ADT/Statistic.h" +#include "llvm/ADT/StringRef.h" +#include "llvm/Analysis/TargetFolder.h" +#include "llvm/Analysis/TargetLibraryInfo.h" +#include "llvm/Analysis/Utils/Local.h" +#include "llvm/Analysis/ValueTracking.h" +#include "llvm/IR/Argument.h" +#include "llvm/IR/Attributes.h" +#include "llvm/IR/Constants.h" +#include "llvm/IR/DataLayout.h" +#include "llvm/IR/DerivedTypes.h" +#include "llvm/IR/Function.h" +#include "llvm/IR/GlobalAlias.h" +#include "llvm/IR/GlobalVariable.h" +#include "llvm/IR/Instruction.h" +#include "llvm/IR/Instructions.h" +#include "llvm/IR/IntrinsicInst.h" +#include "llvm/IR/Operator.h" +#include "llvm/IR/Type.h" +#include "llvm/IR/Value.h" +#include "llvm/Support/Casting.h" +#include "llvm/Support/Debug.h" +#include "llvm/Support/MathExtras.h" +#include "llvm/Support/raw_ostream.h" +#include <cassert> +#include <cstdint> +#include <iterator> +#include <utility> + +using namespace llvm; + +#define DEBUG_TYPE "memory-builtins" + +enum AllocType : uint8_t { + OpNewLike = 1<<0, // allocates; never returns null + MallocLike = 1<<1 | OpNewLike, // allocates; may return null + CallocLike = 1<<2, // allocates + bzero + ReallocLike = 1<<3, // reallocates + StrDupLike = 1<<4, + MallocOrCallocLike = MallocLike | CallocLike, + AllocLike = MallocLike | CallocLike | StrDupLike, + AnyAlloc = AllocLike | ReallocLike +}; + +struct AllocFnsTy { + AllocType AllocTy; + unsigned NumParams; + // First and Second size parameters (or -1 if unused) + int FstParam, SndParam; +}; + +// FIXME: certain users need more information. E.g., SimplifyLibCalls needs to +// know which functions are nounwind, noalias, nocapture parameters, etc. +static const std::pair<LibFunc, AllocFnsTy> AllocationFnData[] = { + {LibFunc_malloc, {MallocLike, 1, 0, -1}}, + {LibFunc_valloc, {MallocLike, 1, 0, -1}}, + {LibFunc_Znwj, {OpNewLike, 1, 0, -1}}, // new(unsigned int) + {LibFunc_ZnwjRKSt9nothrow_t, {MallocLike, 2, 0, -1}}, // new(unsigned int, nothrow) + {LibFunc_ZnwjSt11align_val_t, {OpNewLike, 2, 0, -1}}, // new(unsigned int, align_val_t) + {LibFunc_ZnwjSt11align_val_tRKSt9nothrow_t, // new(unsigned int, align_val_t, nothrow) + {MallocLike, 3, 0, -1}}, + {LibFunc_Znwm, {OpNewLike, 1, 0, -1}}, // new(unsigned long) + {LibFunc_ZnwmRKSt9nothrow_t, {MallocLike, 2, 0, -1}}, // new(unsigned long, nothrow) + {LibFunc_ZnwmSt11align_val_t, {OpNewLike, 2, 0, -1}}, // new(unsigned long, align_val_t) + {LibFunc_ZnwmSt11align_val_tRKSt9nothrow_t, // new(unsigned long, align_val_t, nothrow) + {MallocLike, 3, 0, -1}}, + {LibFunc_Znaj, {OpNewLike, 1, 0, -1}}, // new[](unsigned int) + {LibFunc_ZnajRKSt9nothrow_t, {MallocLike, 2, 0, -1}}, // new[](unsigned int, nothrow) + {LibFunc_ZnajSt11align_val_t, {OpNewLike, 2, 0, -1}}, // new[](unsigned int, align_val_t) + {LibFunc_ZnajSt11align_val_tRKSt9nothrow_t, // new[](unsigned int, align_val_t, nothrow) + {MallocLike, 3, 0, -1}}, + {LibFunc_Znam, {OpNewLike, 1, 0, -1}}, // new[](unsigned long) + {LibFunc_ZnamRKSt9nothrow_t, {MallocLike, 2, 0, -1}}, // new[](unsigned long, nothrow) + {LibFunc_ZnamSt11align_val_t, {OpNewLike, 2, 0, -1}}, // new[](unsigned long, align_val_t) + {LibFunc_ZnamSt11align_val_tRKSt9nothrow_t, // new[](unsigned long, align_val_t, nothrow) + {MallocLike, 3, 0, -1}}, + {LibFunc_msvc_new_int, {OpNewLike, 1, 0, -1}}, // new(unsigned int) + {LibFunc_msvc_new_int_nothrow, {MallocLike, 2, 0, -1}}, // new(unsigned int, nothrow) + {LibFunc_msvc_new_longlong, {OpNewLike, 1, 0, -1}}, // new(unsigned long long) + {LibFunc_msvc_new_longlong_nothrow, {MallocLike, 2, 0, -1}}, // new(unsigned long long, nothrow) + {LibFunc_msvc_new_array_int, {OpNewLike, 1, 0, -1}}, // new[](unsigned int) + {LibFunc_msvc_new_array_int_nothrow, {MallocLike, 2, 0, -1}}, // new[](unsigned int, nothrow) + {LibFunc_msvc_new_array_longlong, {OpNewLike, 1, 0, -1}}, // new[](unsigned long long) + {LibFunc_msvc_new_array_longlong_nothrow, {MallocLike, 2, 0, -1}}, // new[](unsigned long long, nothrow) + {LibFunc_calloc, {CallocLike, 2, 0, 1}}, + {LibFunc_realloc, {ReallocLike, 2, 1, -1}}, + {LibFunc_reallocf, {ReallocLike, 2, 1, -1}}, + {LibFunc_strdup, {StrDupLike, 1, -1, -1}}, + {LibFunc_strndup, {StrDupLike, 2, 1, -1}} + // TODO: Handle "int posix_memalign(void **, size_t, size_t)" +}; + +static const Function *getCalledFunction(const Value *V, bool LookThroughBitCast, + bool &IsNoBuiltin) { + // Don't care about intrinsics in this case. + if (isa<IntrinsicInst>(V)) + return nullptr; + + if (LookThroughBitCast) + V = V->stripPointerCasts(); + + ImmutableCallSite CS(V); + if (!CS.getInstruction()) + return nullptr; + + IsNoBuiltin = CS.isNoBuiltin(); + + if (const Function *Callee = CS.getCalledFunction()) + return Callee; + return nullptr; +} + +/// Returns the allocation data for the given value if it's either a call to a +/// known allocation function, or a call to a function with the allocsize +/// attribute. +static Optional<AllocFnsTy> +getAllocationDataForFunction(const Function *Callee, AllocType AllocTy, + const TargetLibraryInfo *TLI) { + // Make sure that the function is available. + StringRef FnName = Callee->getName(); + LibFunc TLIFn; + if (!TLI || !TLI->getLibFunc(FnName, TLIFn) || !TLI->has(TLIFn)) + return None; + + const auto *Iter = find_if( + AllocationFnData, [TLIFn](const std::pair<LibFunc, AllocFnsTy> &P) { + return P.first == TLIFn; + }); + + if (Iter == std::end(AllocationFnData)) + return None; + + const AllocFnsTy *FnData = &Iter->second; + if ((FnData->AllocTy & AllocTy) != FnData->AllocTy) + return None; + + // Check function prototype. + int FstParam = FnData->FstParam; + int SndParam = FnData->SndParam; + FunctionType *FTy = Callee->getFunctionType(); + + if (FTy->getReturnType() == Type::getInt8PtrTy(FTy->getContext()) && + FTy->getNumParams() == FnData->NumParams && + (FstParam < 0 || + (FTy->getParamType(FstParam)->isIntegerTy(32) || + FTy->getParamType(FstParam)->isIntegerTy(64))) && + (SndParam < 0 || + FTy->getParamType(SndParam)->isIntegerTy(32) || + FTy->getParamType(SndParam)->isIntegerTy(64))) + return *FnData; + return None; +} + +static Optional<AllocFnsTy> getAllocationData(const Value *V, AllocType AllocTy, + const TargetLibraryInfo *TLI, + bool LookThroughBitCast = false) { + bool IsNoBuiltinCall; + if (const Function *Callee = + getCalledFunction(V, LookThroughBitCast, IsNoBuiltinCall)) + if (!IsNoBuiltinCall) + return getAllocationDataForFunction(Callee, AllocTy, TLI); + return None; +} + +static Optional<AllocFnsTy> +getAllocationData(const Value *V, AllocType AllocTy, + function_ref<const TargetLibraryInfo &(Function &)> GetTLI, + bool LookThroughBitCast = false) { + bool IsNoBuiltinCall; + if (const Function *Callee = + getCalledFunction(V, LookThroughBitCast, IsNoBuiltinCall)) + if (!IsNoBuiltinCall) + return getAllocationDataForFunction( + Callee, AllocTy, &GetTLI(const_cast<Function &>(*Callee))); + return None; +} + +static Optional<AllocFnsTy> getAllocationSize(const Value *V, + const TargetLibraryInfo *TLI) { + bool IsNoBuiltinCall; + const Function *Callee = + getCalledFunction(V, /*LookThroughBitCast=*/false, IsNoBuiltinCall); + if (!Callee) + return None; + + // Prefer to use existing information over allocsize. This will give us an + // accurate AllocTy. + if (!IsNoBuiltinCall) + if (Optional<AllocFnsTy> Data = + getAllocationDataForFunction(Callee, AnyAlloc, TLI)) + return Data; + + Attribute Attr = Callee->getFnAttribute(Attribute::AllocSize); + if (Attr == Attribute()) + return None; + + std::pair<unsigned, Optional<unsigned>> Args = Attr.getAllocSizeArgs(); + + AllocFnsTy Result; + // Because allocsize only tells us how many bytes are allocated, we're not + // really allowed to assume anything, so we use MallocLike. + Result.AllocTy = MallocLike; + Result.NumParams = Callee->getNumOperands(); + Result.FstParam = Args.first; + Result.SndParam = Args.second.getValueOr(-1); + return Result; +} + +static bool hasNoAliasAttr(const Value *V, bool LookThroughBitCast) { + ImmutableCallSite CS(LookThroughBitCast ? V->stripPointerCasts() : V); + return CS && CS.hasRetAttr(Attribute::NoAlias); +} + +/// Tests if a value is a call or invoke to a library function that +/// allocates or reallocates memory (either malloc, calloc, realloc, or strdup +/// like). +bool llvm::isAllocationFn(const Value *V, const TargetLibraryInfo *TLI, + bool LookThroughBitCast) { + return getAllocationData(V, AnyAlloc, TLI, LookThroughBitCast).hasValue(); +} +bool llvm::isAllocationFn( + const Value *V, function_ref<const TargetLibraryInfo &(Function &)> GetTLI, + bool LookThroughBitCast) { + return getAllocationData(V, AnyAlloc, GetTLI, LookThroughBitCast).hasValue(); +} + +/// Tests if a value is a call or invoke to a function that returns a +/// NoAlias pointer (including malloc/calloc/realloc/strdup-like functions). +bool llvm::isNoAliasFn(const Value *V, const TargetLibraryInfo *TLI, + bool LookThroughBitCast) { + // it's safe to consider realloc as noalias since accessing the original + // pointer is undefined behavior + return isAllocationFn(V, TLI, LookThroughBitCast) || + hasNoAliasAttr(V, LookThroughBitCast); +} + +/// Tests if a value is a call or invoke to a library function that +/// allocates uninitialized memory (such as malloc). +bool llvm::isMallocLikeFn(const Value *V, const TargetLibraryInfo *TLI, + bool LookThroughBitCast) { + return getAllocationData(V, MallocLike, TLI, LookThroughBitCast).hasValue(); +} +bool llvm::isMallocLikeFn( + const Value *V, function_ref<const TargetLibraryInfo &(Function &)> GetTLI, + bool LookThroughBitCast) { + return getAllocationData(V, MallocLike, GetTLI, LookThroughBitCast) + .hasValue(); +} + +/// Tests if a value is a call or invoke to a library function that +/// allocates zero-filled memory (such as calloc). +bool llvm::isCallocLikeFn(const Value *V, const TargetLibraryInfo *TLI, + bool LookThroughBitCast) { + return getAllocationData(V, CallocLike, TLI, LookThroughBitCast).hasValue(); +} + +/// Tests if a value is a call or invoke to a library function that +/// allocates memory similar to malloc or calloc. +bool llvm::isMallocOrCallocLikeFn(const Value *V, const TargetLibraryInfo *TLI, + bool LookThroughBitCast) { + return getAllocationData(V, MallocOrCallocLike, TLI, + LookThroughBitCast).hasValue(); +} + +/// Tests if a value is a call or invoke to a library function that +/// allocates memory (either malloc, calloc, or strdup like). +bool llvm::isAllocLikeFn(const Value *V, const TargetLibraryInfo *TLI, + bool LookThroughBitCast) { + return getAllocationData(V, AllocLike, TLI, LookThroughBitCast).hasValue(); +} + +/// Tests if a value is a call or invoke to a library function that +/// reallocates memory (e.g., realloc). +bool llvm::isReallocLikeFn(const Value *V, const TargetLibraryInfo *TLI, + bool LookThroughBitCast) { + return getAllocationData(V, ReallocLike, TLI, LookThroughBitCast).hasValue(); +} + +/// Tests if a functions is a call or invoke to a library function that +/// reallocates memory (e.g., realloc). +bool llvm::isReallocLikeFn(const Function *F, const TargetLibraryInfo *TLI) { + return getAllocationDataForFunction(F, ReallocLike, TLI).hasValue(); +} + +/// Tests if a value is a call or invoke to a library function that +/// allocates memory and throws if an allocation failed (e.g., new). +bool llvm::isOpNewLikeFn(const Value *V, const TargetLibraryInfo *TLI, + bool LookThroughBitCast) { + return getAllocationData(V, OpNewLike, TLI, LookThroughBitCast).hasValue(); +} + +/// Tests if a value is a call or invoke to a library function that +/// allocates memory (strdup, strndup). +bool llvm::isStrdupLikeFn(const Value *V, const TargetLibraryInfo *TLI, + bool LookThroughBitCast) { + return getAllocationData(V, StrDupLike, TLI, LookThroughBitCast).hasValue(); +} + +/// extractMallocCall - Returns the corresponding CallInst if the instruction +/// is a malloc call. Since CallInst::CreateMalloc() only creates calls, we +/// ignore InvokeInst here. +const CallInst *llvm::extractMallocCall( + const Value *I, + function_ref<const TargetLibraryInfo &(Function &)> GetTLI) { + return isMallocLikeFn(I, GetTLI) ? dyn_cast<CallInst>(I) : nullptr; +} + +static Value *computeArraySize(const CallInst *CI, const DataLayout &DL, + const TargetLibraryInfo *TLI, + bool LookThroughSExt = false) { + if (!CI) + return nullptr; + + // The size of the malloc's result type must be known to determine array size. + Type *T = getMallocAllocatedType(CI, TLI); + if (!T || !T->isSized()) + return nullptr; + + unsigned ElementSize = DL.getTypeAllocSize(T); + if (StructType *ST = dyn_cast<StructType>(T)) + ElementSize = DL.getStructLayout(ST)->getSizeInBytes(); + + // If malloc call's arg can be determined to be a multiple of ElementSize, + // return the multiple. Otherwise, return NULL. + Value *MallocArg = CI->getArgOperand(0); + Value *Multiple = nullptr; + if (ComputeMultiple(MallocArg, ElementSize, Multiple, LookThroughSExt)) + return Multiple; + + return nullptr; +} + +/// getMallocType - Returns the PointerType resulting from the malloc call. +/// The PointerType depends on the number of bitcast uses of the malloc call: +/// 0: PointerType is the calls' return type. +/// 1: PointerType is the bitcast's result type. +/// >1: Unique PointerType cannot be determined, return NULL. +PointerType *llvm::getMallocType(const CallInst *CI, + const TargetLibraryInfo *TLI) { + assert(isMallocLikeFn(CI, TLI) && "getMallocType and not malloc call"); + + PointerType *MallocType = nullptr; + unsigned NumOfBitCastUses = 0; + + // Determine if CallInst has a bitcast use. + for (Value::const_user_iterator UI = CI->user_begin(), E = CI->user_end(); + UI != E;) + if (const BitCastInst *BCI = dyn_cast<BitCastInst>(*UI++)) { + MallocType = cast<PointerType>(BCI->getDestTy()); + NumOfBitCastUses++; + } + + // Malloc call has 1 bitcast use, so type is the bitcast's destination type. + if (NumOfBitCastUses == 1) + return MallocType; + + // Malloc call was not bitcast, so type is the malloc function's return type. + if (NumOfBitCastUses == 0) + return cast<PointerType>(CI->getType()); + + // Type could not be determined. + return nullptr; +} + +/// getMallocAllocatedType - Returns the Type allocated by malloc call. +/// The Type depends on the number of bitcast uses of the malloc call: +/// 0: PointerType is the malloc calls' return type. +/// 1: PointerType is the bitcast's result type. +/// >1: Unique PointerType cannot be determined, return NULL. +Type *llvm::getMallocAllocatedType(const CallInst *CI, + const TargetLibraryInfo *TLI) { + PointerType *PT = getMallocType(CI, TLI); + return PT ? PT->getElementType() : nullptr; +} + +/// getMallocArraySize - Returns the array size of a malloc call. If the +/// argument passed to malloc is a multiple of the size of the malloced type, +/// then return that multiple. For non-array mallocs, the multiple is +/// constant 1. Otherwise, return NULL for mallocs whose array size cannot be +/// determined. +Value *llvm::getMallocArraySize(CallInst *CI, const DataLayout &DL, + const TargetLibraryInfo *TLI, + bool LookThroughSExt) { + assert(isMallocLikeFn(CI, TLI) && "getMallocArraySize and not malloc call"); + return computeArraySize(CI, DL, TLI, LookThroughSExt); +} + +/// extractCallocCall - Returns the corresponding CallInst if the instruction +/// is a calloc call. +const CallInst *llvm::extractCallocCall(const Value *I, + const TargetLibraryInfo *TLI) { + return isCallocLikeFn(I, TLI) ? cast<CallInst>(I) : nullptr; +} + +/// isLibFreeFunction - Returns true if the function is a builtin free() +bool llvm::isLibFreeFunction(const Function *F, const LibFunc TLIFn) { + unsigned ExpectedNumParams; + if (TLIFn == LibFunc_free || + TLIFn == LibFunc_ZdlPv || // operator delete(void*) + TLIFn == LibFunc_ZdaPv || // operator delete[](void*) + TLIFn == LibFunc_msvc_delete_ptr32 || // operator delete(void*) + TLIFn == LibFunc_msvc_delete_ptr64 || // operator delete(void*) + TLIFn == LibFunc_msvc_delete_array_ptr32 || // operator delete[](void*) + TLIFn == LibFunc_msvc_delete_array_ptr64) // operator delete[](void*) + ExpectedNumParams = 1; + else if (TLIFn == LibFunc_ZdlPvj || // delete(void*, uint) + TLIFn == LibFunc_ZdlPvm || // delete(void*, ulong) + TLIFn == LibFunc_ZdlPvRKSt9nothrow_t || // delete(void*, nothrow) + TLIFn == LibFunc_ZdlPvSt11align_val_t || // delete(void*, align_val_t) + TLIFn == LibFunc_ZdaPvj || // delete[](void*, uint) + TLIFn == LibFunc_ZdaPvm || // delete[](void*, ulong) + TLIFn == LibFunc_ZdaPvRKSt9nothrow_t || // delete[](void*, nothrow) + TLIFn == LibFunc_ZdaPvSt11align_val_t || // delete[](void*, align_val_t) + TLIFn == LibFunc_msvc_delete_ptr32_int || // delete(void*, uint) + TLIFn == LibFunc_msvc_delete_ptr64_longlong || // delete(void*, ulonglong) + TLIFn == LibFunc_msvc_delete_ptr32_nothrow || // delete(void*, nothrow) + TLIFn == LibFunc_msvc_delete_ptr64_nothrow || // delete(void*, nothrow) + TLIFn == LibFunc_msvc_delete_array_ptr32_int || // delete[](void*, uint) + TLIFn == LibFunc_msvc_delete_array_ptr64_longlong || // delete[](void*, ulonglong) + TLIFn == LibFunc_msvc_delete_array_ptr32_nothrow || // delete[](void*, nothrow) + TLIFn == LibFunc_msvc_delete_array_ptr64_nothrow) // delete[](void*, nothrow) + ExpectedNumParams = 2; + else if (TLIFn == LibFunc_ZdaPvSt11align_val_tRKSt9nothrow_t || // delete(void*, align_val_t, nothrow) + TLIFn == LibFunc_ZdlPvSt11align_val_tRKSt9nothrow_t) // delete[](void*, align_val_t, nothrow) + ExpectedNumParams = 3; + else + return false; + + // Check free prototype. + // FIXME: workaround for PR5130, this will be obsolete when a nobuiltin + // attribute will exist. + FunctionType *FTy = F->getFunctionType(); + if (!FTy->getReturnType()->isVoidTy()) + return false; + if (FTy->getNumParams() != ExpectedNumParams) + return false; + if (FTy->getParamType(0) != Type::getInt8PtrTy(F->getContext())) + return false; + + return true; +} + +/// isFreeCall - Returns non-null if the value is a call to the builtin free() +const CallInst *llvm::isFreeCall(const Value *I, const TargetLibraryInfo *TLI) { + bool IsNoBuiltinCall; + const Function *Callee = + getCalledFunction(I, /*LookThroughBitCast=*/false, IsNoBuiltinCall); + if (Callee == nullptr || IsNoBuiltinCall) + return nullptr; + + StringRef FnName = Callee->getName(); + LibFunc TLIFn; + if (!TLI || !TLI->getLibFunc(FnName, TLIFn) || !TLI->has(TLIFn)) + return nullptr; + + return isLibFreeFunction(Callee, TLIFn) ? dyn_cast<CallInst>(I) : nullptr; +} + + +//===----------------------------------------------------------------------===// +// Utility functions to compute size of objects. +// +static APInt getSizeWithOverflow(const SizeOffsetType &Data) { + if (Data.second.isNegative() || Data.first.ult(Data.second)) + return APInt(Data.first.getBitWidth(), 0); + return Data.first - Data.second; +} + +/// Compute the size of the object pointed by Ptr. Returns true and the +/// object size in Size if successful, and false otherwise. +/// If RoundToAlign is true, then Size is rounded up to the alignment of +/// allocas, byval arguments, and global variables. +bool llvm::getObjectSize(const Value *Ptr, uint64_t &Size, const DataLayout &DL, + const TargetLibraryInfo *TLI, ObjectSizeOpts Opts) { + ObjectSizeOffsetVisitor Visitor(DL, TLI, Ptr->getContext(), Opts); + SizeOffsetType Data = Visitor.compute(const_cast<Value*>(Ptr)); + if (!Visitor.bothKnown(Data)) + return false; + + Size = getSizeWithOverflow(Data).getZExtValue(); + return true; +} + +Value *llvm::lowerObjectSizeCall(IntrinsicInst *ObjectSize, + const DataLayout &DL, + const TargetLibraryInfo *TLI, + bool MustSucceed) { + assert(ObjectSize->getIntrinsicID() == Intrinsic::objectsize && + "ObjectSize must be a call to llvm.objectsize!"); + + bool MaxVal = cast<ConstantInt>(ObjectSize->getArgOperand(1))->isZero(); + ObjectSizeOpts EvalOptions; + // Unless we have to fold this to something, try to be as accurate as + // possible. + if (MustSucceed) + EvalOptions.EvalMode = + MaxVal ? ObjectSizeOpts::Mode::Max : ObjectSizeOpts::Mode::Min; + else + EvalOptions.EvalMode = ObjectSizeOpts::Mode::Exact; + + EvalOptions.NullIsUnknownSize = + cast<ConstantInt>(ObjectSize->getArgOperand(2))->isOne(); + + auto *ResultType = cast<IntegerType>(ObjectSize->getType()); + bool StaticOnly = cast<ConstantInt>(ObjectSize->getArgOperand(3))->isZero(); + if (StaticOnly) { + // FIXME: Does it make sense to just return a failure value if the size won't + // fit in the output and `!MustSucceed`? + uint64_t Size; + if (getObjectSize(ObjectSize->getArgOperand(0), Size, DL, TLI, EvalOptions) && + isUIntN(ResultType->getBitWidth(), Size)) + return ConstantInt::get(ResultType, Size); + } else { + LLVMContext &Ctx = ObjectSize->getFunction()->getContext(); + ObjectSizeOffsetEvaluator Eval(DL, TLI, Ctx, EvalOptions); + SizeOffsetEvalType SizeOffsetPair = + Eval.compute(ObjectSize->getArgOperand(0)); + + if (SizeOffsetPair != ObjectSizeOffsetEvaluator::unknown()) { + IRBuilder<TargetFolder> Builder(Ctx, TargetFolder(DL)); + Builder.SetInsertPoint(ObjectSize); + + // If we've outside the end of the object, then we can always access + // exactly 0 bytes. + Value *ResultSize = + Builder.CreateSub(SizeOffsetPair.first, SizeOffsetPair.second); + Value *UseZero = + Builder.CreateICmpULT(SizeOffsetPair.first, SizeOffsetPair.second); + return Builder.CreateSelect(UseZero, ConstantInt::get(ResultType, 0), + ResultSize); + } + } + + if (!MustSucceed) + return nullptr; + + return ConstantInt::get(ResultType, MaxVal ? -1ULL : 0); +} + +STATISTIC(ObjectVisitorArgument, + "Number of arguments with unsolved size and offset"); +STATISTIC(ObjectVisitorLoad, + "Number of load instructions with unsolved size and offset"); + +APInt ObjectSizeOffsetVisitor::align(APInt Size, uint64_t Alignment) { + if (Options.RoundToAlign && Alignment) + return APInt(IntTyBits, alignTo(Size.getZExtValue(), Align(Alignment))); + return Size; +} + +ObjectSizeOffsetVisitor::ObjectSizeOffsetVisitor(const DataLayout &DL, + const TargetLibraryInfo *TLI, + LLVMContext &Context, + ObjectSizeOpts Options) + : DL(DL), TLI(TLI), Options(Options) { + // Pointer size must be rechecked for each object visited since it could have + // a different address space. +} + +SizeOffsetType ObjectSizeOffsetVisitor::compute(Value *V) { + IntTyBits = DL.getPointerTypeSizeInBits(V->getType()); + Zero = APInt::getNullValue(IntTyBits); + + V = V->stripPointerCasts(); + if (Instruction *I = dyn_cast<Instruction>(V)) { + // If we have already seen this instruction, bail out. Cycles can happen in + // unreachable code after constant propagation. + if (!SeenInsts.insert(I).second) + return unknown(); + + if (GEPOperator *GEP = dyn_cast<GEPOperator>(V)) + return visitGEPOperator(*GEP); + return visit(*I); + } + if (Argument *A = dyn_cast<Argument>(V)) + return visitArgument(*A); + if (ConstantPointerNull *P = dyn_cast<ConstantPointerNull>(V)) + return visitConstantPointerNull(*P); + if (GlobalAlias *GA = dyn_cast<GlobalAlias>(V)) + return visitGlobalAlias(*GA); + if (GlobalVariable *GV = dyn_cast<GlobalVariable>(V)) + return visitGlobalVariable(*GV); + if (UndefValue *UV = dyn_cast<UndefValue>(V)) + return visitUndefValue(*UV); + if (ConstantExpr *CE = dyn_cast<ConstantExpr>(V)) { + if (CE->getOpcode() == Instruction::IntToPtr) + return unknown(); // clueless + if (CE->getOpcode() == Instruction::GetElementPtr) + return visitGEPOperator(cast<GEPOperator>(*CE)); + } + + LLVM_DEBUG(dbgs() << "ObjectSizeOffsetVisitor::compute() unhandled value: " + << *V << '\n'); + return unknown(); +} + +/// When we're compiling N-bit code, and the user uses parameters that are +/// greater than N bits (e.g. uint64_t on a 32-bit build), we can run into +/// trouble with APInt size issues. This function handles resizing + overflow +/// checks for us. Check and zext or trunc \p I depending on IntTyBits and +/// I's value. +bool ObjectSizeOffsetVisitor::CheckedZextOrTrunc(APInt &I) { + // More bits than we can handle. Checking the bit width isn't necessary, but + // it's faster than checking active bits, and should give `false` in the + // vast majority of cases. + if (I.getBitWidth() > IntTyBits && I.getActiveBits() > IntTyBits) + return false; + if (I.getBitWidth() != IntTyBits) + I = I.zextOrTrunc(IntTyBits); + return true; +} + +SizeOffsetType ObjectSizeOffsetVisitor::visitAllocaInst(AllocaInst &I) { + if (!I.getAllocatedType()->isSized()) + return unknown(); + + APInt Size(IntTyBits, DL.getTypeAllocSize(I.getAllocatedType())); + if (!I.isArrayAllocation()) + return std::make_pair(align(Size, I.getAlignment()), Zero); + + Value *ArraySize = I.getArraySize(); + if (const ConstantInt *C = dyn_cast<ConstantInt>(ArraySize)) { + APInt NumElems = C->getValue(); + if (!CheckedZextOrTrunc(NumElems)) + return unknown(); + + bool Overflow; + Size = Size.umul_ov(NumElems, Overflow); + return Overflow ? unknown() : std::make_pair(align(Size, I.getAlignment()), + Zero); + } + return unknown(); +} + +SizeOffsetType ObjectSizeOffsetVisitor::visitArgument(Argument &A) { + // No interprocedural analysis is done at the moment. + if (!A.hasByValOrInAllocaAttr()) { + ++ObjectVisitorArgument; + return unknown(); + } + PointerType *PT = cast<PointerType>(A.getType()); + APInt Size(IntTyBits, DL.getTypeAllocSize(PT->getElementType())); + return std::make_pair(align(Size, A.getParamAlignment()), Zero); +} + +SizeOffsetType ObjectSizeOffsetVisitor::visitCallSite(CallSite CS) { + Optional<AllocFnsTy> FnData = getAllocationSize(CS.getInstruction(), TLI); + if (!FnData) + return unknown(); + + // Handle strdup-like functions separately. + if (FnData->AllocTy == StrDupLike) { + APInt Size(IntTyBits, GetStringLength(CS.getArgument(0))); + if (!Size) + return unknown(); + + // Strndup limits strlen. + if (FnData->FstParam > 0) { + ConstantInt *Arg = + dyn_cast<ConstantInt>(CS.getArgument(FnData->FstParam)); + if (!Arg) + return unknown(); + + APInt MaxSize = Arg->getValue().zextOrSelf(IntTyBits); + if (Size.ugt(MaxSize)) + Size = MaxSize + 1; + } + return std::make_pair(Size, Zero); + } + + ConstantInt *Arg = dyn_cast<ConstantInt>(CS.getArgument(FnData->FstParam)); + if (!Arg) + return unknown(); + + APInt Size = Arg->getValue(); + if (!CheckedZextOrTrunc(Size)) + return unknown(); + + // Size is determined by just 1 parameter. + if (FnData->SndParam < 0) + return std::make_pair(Size, Zero); + + Arg = dyn_cast<ConstantInt>(CS.getArgument(FnData->SndParam)); + if (!Arg) + return unknown(); + + APInt NumElems = Arg->getValue(); + if (!CheckedZextOrTrunc(NumElems)) + return unknown(); + + bool Overflow; + Size = Size.umul_ov(NumElems, Overflow); + return Overflow ? unknown() : std::make_pair(Size, Zero); + + // TODO: handle more standard functions (+ wchar cousins): + // - strdup / strndup + // - strcpy / strncpy + // - strcat / strncat + // - memcpy / memmove + // - strcat / strncat + // - memset +} + +SizeOffsetType +ObjectSizeOffsetVisitor::visitConstantPointerNull(ConstantPointerNull& CPN) { + // If null is unknown, there's nothing we can do. Additionally, non-zero + // address spaces can make use of null, so we don't presume to know anything + // about that. + // + // TODO: How should this work with address space casts? We currently just drop + // them on the floor, but it's unclear what we should do when a NULL from + // addrspace(1) gets casted to addrspace(0) (or vice-versa). + if (Options.NullIsUnknownSize || CPN.getType()->getAddressSpace()) + return unknown(); + return std::make_pair(Zero, Zero); +} + +SizeOffsetType +ObjectSizeOffsetVisitor::visitExtractElementInst(ExtractElementInst&) { + return unknown(); +} + +SizeOffsetType +ObjectSizeOffsetVisitor::visitExtractValueInst(ExtractValueInst&) { + // Easy cases were already folded by previous passes. + return unknown(); +} + +SizeOffsetType ObjectSizeOffsetVisitor::visitGEPOperator(GEPOperator &GEP) { + SizeOffsetType PtrData = compute(GEP.getPointerOperand()); + APInt Offset(IntTyBits, 0); + if (!bothKnown(PtrData) || !GEP.accumulateConstantOffset(DL, Offset)) + return unknown(); + + return std::make_pair(PtrData.first, PtrData.second + Offset); +} + +SizeOffsetType ObjectSizeOffsetVisitor::visitGlobalAlias(GlobalAlias &GA) { + if (GA.isInterposable()) + return unknown(); + return compute(GA.getAliasee()); +} + +SizeOffsetType ObjectSizeOffsetVisitor::visitGlobalVariable(GlobalVariable &GV){ + if (!GV.hasDefinitiveInitializer()) + return unknown(); + + APInt Size(IntTyBits, DL.getTypeAllocSize(GV.getValueType())); + return std::make_pair(align(Size, GV.getAlignment()), Zero); +} + +SizeOffsetType ObjectSizeOffsetVisitor::visitIntToPtrInst(IntToPtrInst&) { + // clueless + return unknown(); +} + +SizeOffsetType ObjectSizeOffsetVisitor::visitLoadInst(LoadInst&) { + ++ObjectVisitorLoad; + return unknown(); +} + +SizeOffsetType ObjectSizeOffsetVisitor::visitPHINode(PHINode&) { + // too complex to analyze statically. + return unknown(); +} + +SizeOffsetType ObjectSizeOffsetVisitor::visitSelectInst(SelectInst &I) { + SizeOffsetType TrueSide = compute(I.getTrueValue()); + SizeOffsetType FalseSide = compute(I.getFalseValue()); + if (bothKnown(TrueSide) && bothKnown(FalseSide)) { + if (TrueSide == FalseSide) { + return TrueSide; + } + + APInt TrueResult = getSizeWithOverflow(TrueSide); + APInt FalseResult = getSizeWithOverflow(FalseSide); + + if (TrueResult == FalseResult) { + return TrueSide; + } + if (Options.EvalMode == ObjectSizeOpts::Mode::Min) { + if (TrueResult.slt(FalseResult)) + return TrueSide; + return FalseSide; + } + if (Options.EvalMode == ObjectSizeOpts::Mode::Max) { + if (TrueResult.sgt(FalseResult)) + return TrueSide; + return FalseSide; + } + } + return unknown(); +} + +SizeOffsetType ObjectSizeOffsetVisitor::visitUndefValue(UndefValue&) { + return std::make_pair(Zero, Zero); +} + +SizeOffsetType ObjectSizeOffsetVisitor::visitInstruction(Instruction &I) { + LLVM_DEBUG(dbgs() << "ObjectSizeOffsetVisitor unknown instruction:" << I + << '\n'); + return unknown(); +} + +ObjectSizeOffsetEvaluator::ObjectSizeOffsetEvaluator( + const DataLayout &DL, const TargetLibraryInfo *TLI, LLVMContext &Context, + ObjectSizeOpts EvalOpts) + : DL(DL), TLI(TLI), Context(Context), + Builder(Context, TargetFolder(DL), + IRBuilderCallbackInserter( + [&](Instruction *I) { InsertedInstructions.insert(I); })), + EvalOpts(EvalOpts) { + // IntTy and Zero must be set for each compute() since the address space may + // be different for later objects. +} + +SizeOffsetEvalType ObjectSizeOffsetEvaluator::compute(Value *V) { + // XXX - Are vectors of pointers possible here? + IntTy = cast<IntegerType>(DL.getIntPtrType(V->getType())); + Zero = ConstantInt::get(IntTy, 0); + + SizeOffsetEvalType Result = compute_(V); + + if (!bothKnown(Result)) { + // Erase everything that was computed in this iteration from the cache, so + // that no dangling references are left behind. We could be a bit smarter if + // we kept a dependency graph. It's probably not worth the complexity. + for (const Value *SeenVal : SeenVals) { + CacheMapTy::iterator CacheIt = CacheMap.find(SeenVal); + // non-computable results can be safely cached + if (CacheIt != CacheMap.end() && anyKnown(CacheIt->second)) + CacheMap.erase(CacheIt); + } + + // Erase any instructions we inserted as part of the traversal. + for (Instruction *I : InsertedInstructions) { + I->replaceAllUsesWith(UndefValue::get(I->getType())); + I->eraseFromParent(); + } + } + + SeenVals.clear(); + InsertedInstructions.clear(); + return Result; +} + +SizeOffsetEvalType ObjectSizeOffsetEvaluator::compute_(Value *V) { + ObjectSizeOffsetVisitor Visitor(DL, TLI, Context, EvalOpts); + SizeOffsetType Const = Visitor.compute(V); + if (Visitor.bothKnown(Const)) + return std::make_pair(ConstantInt::get(Context, Const.first), + ConstantInt::get(Context, Const.second)); + + V = V->stripPointerCasts(); + + // Check cache. + CacheMapTy::iterator CacheIt = CacheMap.find(V); + if (CacheIt != CacheMap.end()) + return CacheIt->second; + + // Always generate code immediately before the instruction being + // processed, so that the generated code dominates the same BBs. + BuilderTy::InsertPointGuard Guard(Builder); + if (Instruction *I = dyn_cast<Instruction>(V)) + Builder.SetInsertPoint(I); + + // Now compute the size and offset. + SizeOffsetEvalType Result; + + // Record the pointers that were handled in this run, so that they can be + // cleaned later if something fails. We also use this set to break cycles that + // can occur in dead code. + if (!SeenVals.insert(V).second) { + Result = unknown(); + } else if (GEPOperator *GEP = dyn_cast<GEPOperator>(V)) { + Result = visitGEPOperator(*GEP); + } else if (Instruction *I = dyn_cast<Instruction>(V)) { + Result = visit(*I); + } else if (isa<Argument>(V) || + (isa<ConstantExpr>(V) && + cast<ConstantExpr>(V)->getOpcode() == Instruction::IntToPtr) || + isa<GlobalAlias>(V) || + isa<GlobalVariable>(V)) { + // Ignore values where we cannot do more than ObjectSizeVisitor. + Result = unknown(); + } else { + LLVM_DEBUG( + dbgs() << "ObjectSizeOffsetEvaluator::compute() unhandled value: " << *V + << '\n'); + Result = unknown(); + } + + // Don't reuse CacheIt since it may be invalid at this point. + CacheMap[V] = Result; + return Result; +} + +SizeOffsetEvalType ObjectSizeOffsetEvaluator::visitAllocaInst(AllocaInst &I) { + if (!I.getAllocatedType()->isSized()) + return unknown(); + + // must be a VLA + assert(I.isArrayAllocation()); + Value *ArraySize = I.getArraySize(); + Value *Size = ConstantInt::get(ArraySize->getType(), + DL.getTypeAllocSize(I.getAllocatedType())); + Size = Builder.CreateMul(Size, ArraySize); + return std::make_pair(Size, Zero); +} + +SizeOffsetEvalType ObjectSizeOffsetEvaluator::visitCallSite(CallSite CS) { + Optional<AllocFnsTy> FnData = getAllocationSize(CS.getInstruction(), TLI); + if (!FnData) + return unknown(); + + // Handle strdup-like functions separately. + if (FnData->AllocTy == StrDupLike) { + // TODO + return unknown(); + } + + Value *FirstArg = CS.getArgument(FnData->FstParam); + FirstArg = Builder.CreateZExt(FirstArg, IntTy); + if (FnData->SndParam < 0) + return std::make_pair(FirstArg, Zero); + + Value *SecondArg = CS.getArgument(FnData->SndParam); + SecondArg = Builder.CreateZExt(SecondArg, IntTy); + Value *Size = Builder.CreateMul(FirstArg, SecondArg); + return std::make_pair(Size, Zero); + + // TODO: handle more standard functions (+ wchar cousins): + // - strdup / strndup + // - strcpy / strncpy + // - strcat / strncat + // - memcpy / memmove + // - strcat / strncat + // - memset +} + +SizeOffsetEvalType +ObjectSizeOffsetEvaluator::visitExtractElementInst(ExtractElementInst&) { + return unknown(); +} + +SizeOffsetEvalType +ObjectSizeOffsetEvaluator::visitExtractValueInst(ExtractValueInst&) { + return unknown(); +} + +SizeOffsetEvalType +ObjectSizeOffsetEvaluator::visitGEPOperator(GEPOperator &GEP) { + SizeOffsetEvalType PtrData = compute_(GEP.getPointerOperand()); + if (!bothKnown(PtrData)) + return unknown(); + + Value *Offset = EmitGEPOffset(&Builder, DL, &GEP, /*NoAssumptions=*/true); + Offset = Builder.CreateAdd(PtrData.second, Offset); + return std::make_pair(PtrData.first, Offset); +} + +SizeOffsetEvalType ObjectSizeOffsetEvaluator::visitIntToPtrInst(IntToPtrInst&) { + // clueless + return unknown(); +} + +SizeOffsetEvalType ObjectSizeOffsetEvaluator::visitLoadInst(LoadInst&) { + return unknown(); +} + +SizeOffsetEvalType ObjectSizeOffsetEvaluator::visitPHINode(PHINode &PHI) { + // Create 2 PHIs: one for size and another for offset. + PHINode *SizePHI = Builder.CreatePHI(IntTy, PHI.getNumIncomingValues()); + PHINode *OffsetPHI = Builder.CreatePHI(IntTy, PHI.getNumIncomingValues()); + + // Insert right away in the cache to handle recursive PHIs. + CacheMap[&PHI] = std::make_pair(SizePHI, OffsetPHI); + + // Compute offset/size for each PHI incoming pointer. + for (unsigned i = 0, e = PHI.getNumIncomingValues(); i != e; ++i) { + Builder.SetInsertPoint(&*PHI.getIncomingBlock(i)->getFirstInsertionPt()); + SizeOffsetEvalType EdgeData = compute_(PHI.getIncomingValue(i)); + + if (!bothKnown(EdgeData)) { + OffsetPHI->replaceAllUsesWith(UndefValue::get(IntTy)); + OffsetPHI->eraseFromParent(); + InsertedInstructions.erase(OffsetPHI); + SizePHI->replaceAllUsesWith(UndefValue::get(IntTy)); + SizePHI->eraseFromParent(); + InsertedInstructions.erase(SizePHI); + return unknown(); + } + SizePHI->addIncoming(EdgeData.first, PHI.getIncomingBlock(i)); + OffsetPHI->addIncoming(EdgeData.second, PHI.getIncomingBlock(i)); + } + + Value *Size = SizePHI, *Offset = OffsetPHI; + if (Value *Tmp = SizePHI->hasConstantValue()) { + Size = Tmp; + SizePHI->replaceAllUsesWith(Size); + SizePHI->eraseFromParent(); + InsertedInstructions.erase(SizePHI); + } + if (Value *Tmp = OffsetPHI->hasConstantValue()) { + Offset = Tmp; + OffsetPHI->replaceAllUsesWith(Offset); + OffsetPHI->eraseFromParent(); + InsertedInstructions.erase(OffsetPHI); + } + return std::make_pair(Size, Offset); +} + +SizeOffsetEvalType ObjectSizeOffsetEvaluator::visitSelectInst(SelectInst &I) { + SizeOffsetEvalType TrueSide = compute_(I.getTrueValue()); + SizeOffsetEvalType FalseSide = compute_(I.getFalseValue()); + + if (!bothKnown(TrueSide) || !bothKnown(FalseSide)) + return unknown(); + if (TrueSide == FalseSide) + return TrueSide; + + Value *Size = Builder.CreateSelect(I.getCondition(), TrueSide.first, + FalseSide.first); + Value *Offset = Builder.CreateSelect(I.getCondition(), TrueSide.second, + FalseSide.second); + return std::make_pair(Size, Offset); +} + +SizeOffsetEvalType ObjectSizeOffsetEvaluator::visitInstruction(Instruction &I) { + LLVM_DEBUG(dbgs() << "ObjectSizeOffsetEvaluator unknown instruction:" << I + << '\n'); + return unknown(); +} |