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llvm-mirror/lib/Analysis/MemoryBuiltins.cpp
Petar Jovanovic 9f56ef2b97 Calculate __builtin_object_size when pointer depends on a condition 
This patch fixes calculating of builtin_object_size if it depends on a
condition. Before this patch compiler did not know how to calculate the
object size when it finds a condition that cannot be eliminated.
This patch enables calculating of builtin_object_size even in case when
condition cannot be eliminated by choosing minimum or maximum value as a
result from condition. Choosing minimum or maximum value from condition
is based on the second argument of __builtin_object_size function.

Patch by Strahinja Petrovic.

Differential Revision: http://reviews.llvm.org/D18438

llvm-svn: 266193
2016-04-13 12:25:25 +00:00

858 lines
32 KiB
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//===------ MemoryBuiltins.cpp - Identify calls to memory builtins --------===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This family of functions identifies calls to builtin functions that allocate
// or free memory.
//
//===----------------------------------------------------------------------===//
#include "llvm/Analysis/MemoryBuiltins.h"
#include "llvm/ADT/STLExtras.h"
#include "llvm/ADT/Statistic.h"
#include "llvm/Analysis/TargetLibraryInfo.h"
#include "llvm/Analysis/ValueTracking.h"
#include "llvm/IR/DataLayout.h"
#include "llvm/IR/GlobalVariable.h"
#include "llvm/IR/Instructions.h"
#include "llvm/IR/Intrinsics.h"
#include "llvm/IR/Metadata.h"
#include "llvm/IR/Module.h"
#include "llvm/Support/Debug.h"
#include "llvm/Support/MathExtras.h"
#include "llvm/Support/raw_ostream.h"
#include "llvm/Transforms/Utils/Local.h"
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,
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::Func, 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::Znwm, {OpNewLike, 1, 0, -1}}, // new(unsigned long)
{LibFunc::ZnwmRKSt9nothrow_t, {MallocLike, 2, 0, -1}}, // new(unsigned long, nothrow)
{LibFunc::Znaj, {OpNewLike, 1, 0, -1}}, // new[](unsigned int)
{LibFunc::ZnajRKSt9nothrow_t, {MallocLike, 2, 0, -1}}, // new[](unsigned int, nothrow)
{LibFunc::Znam, {OpNewLike, 1, 0, -1}}, // new[](unsigned long)
{LibFunc::ZnamRKSt9nothrow_t, {MallocLike, 2, 0, -1}}, // new[](unsigned long, nothrow)
{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 Function *getCalledFunction(const Value *V, bool LookThroughBitCast) {
if (LookThroughBitCast)
V = V->stripPointerCasts();
CallSite CS(const_cast<Value*>(V));
if (!CS.getInstruction())
return nullptr;
if (CS.isNoBuiltin())
return nullptr;
Function *Callee = CS.getCalledFunction();
if (!Callee || !Callee->isDeclaration())
return nullptr;
return Callee;
}
/// 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> getAllocationData(const Value *V, AllocType AllocTy,
const TargetLibraryInfo *TLI,
bool LookThroughBitCast = false) {
// Skip intrinsics
if (isa<IntrinsicInst>(V))
return None;
const Function *Callee = getCalledFunction(V, LookThroughBitCast);
if (!Callee)
return None;
// If it has allocsize, we can skip checking if it's a known function.
//
// MallocLike is chosen here because allocsize makes no guarantees about the
// nullness of the result of the function, nor does it deal with strings, nor
// does it require that the memory returned is zeroed out.
LLVM_CONSTEXPR auto AllocSizeAllocTy = MallocLike;
if ((AllocTy & AllocSizeAllocTy) == AllocSizeAllocTy &&
Callee->hasFnAttribute(Attribute::AllocSize)) {
Attribute Attr = Callee->getFnAttribute(Attribute::AllocSize);
std::pair<unsigned, Optional<unsigned>> Args = Attr.getAllocSizeArgs();
AllocFnsTy Result;
Result.AllocTy = AllocSizeAllocTy;
Result.NumParams = Callee->getNumOperands();
Result.FstParam = Args.first;
Result.SndParam = Args.second.getValueOr(-1);
return Result;
}
// Make sure that the function is available.
StringRef FnName = Callee->getName();
LibFunc::Func TLIFn;
if (!TLI || !TLI->getLibFunc(FnName, TLIFn) || !TLI->has(TLIFn))
return None;
const auto *Iter =
std::find_if(std::begin(AllocationFnData), std::end(AllocationFnData),
[TLIFn](const std::pair<LibFunc::Func, 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 bool hasNoAliasAttr(const Value *V, bool LookThroughBitCast) {
ImmutableCallSite CS(LookThroughBitCast ? V->stripPointerCasts() : V);
return CS && CS.paramHasAttr(AttributeSet::ReturnIndex, Attribute::NoAlias);
}
/// \brief 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();
}
/// \brief 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);
}
/// \brief 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();
}
/// \brief 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();
}
/// \brief 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();
}
/// 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,
const TargetLibraryInfo *TLI) {
return isMallocLikeFn(I, TLI) ? 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;
}
/// isFreeCall - Returns non-null if the value is a call to the builtin free()
const CallInst *llvm::isFreeCall(const Value *I, const TargetLibraryInfo *TLI) {
const CallInst *CI = dyn_cast<CallInst>(I);
if (!CI || isa<IntrinsicInst>(CI))
return nullptr;
Function *Callee = CI->getCalledFunction();
if (Callee == nullptr)
return nullptr;
StringRef FnName = Callee->getName();
LibFunc::Func TLIFn;
if (!TLI || !TLI->getLibFunc(FnName, TLIFn) || !TLI->has(TLIFn))
return nullptr;
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::ZdaPvj || // delete[](void*, uint)
TLIFn == LibFunc::ZdaPvm || // delete[](void*, ulong)
TLIFn == LibFunc::ZdaPvRKSt9nothrow_t || // delete[](void*, nothrow)
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
return nullptr;
// Check free prototype.
// FIXME: workaround for PR5130, this will be obsolete when a nobuiltin
// attribute will exist.
FunctionType *FTy = Callee->getFunctionType();
if (!FTy->getReturnType()->isVoidTy())
return nullptr;
if (FTy->getNumParams() != ExpectedNumParams)
return nullptr;
if (FTy->getParamType(0) != Type::getInt8PtrTy(Callee->getContext()))
return nullptr;
return CI;
}
//===----------------------------------------------------------------------===//
// 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;
}
/// \brief 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 aligment of allocas,
/// byval arguments, and global variables.
bool llvm::getObjectSize(const Value *Ptr, uint64_t &Size, const DataLayout &DL,
const TargetLibraryInfo *TLI, bool RoundToAlign,
llvm::ObjSizeMode Mode) {
ObjectSizeOffsetVisitor Visitor(DL, TLI, Ptr->getContext(),
RoundToAlign, Mode);
SizeOffsetType Data = Visitor.compute(const_cast<Value*>(Ptr));
if (!Visitor.bothKnown(Data))
return false;
Size = getSizeWithOverflow(Data).getZExtValue();
return true;
}
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 Align) {
if (RoundToAlign && Align)
return APInt(IntTyBits, alignTo(Size.getZExtValue(), Align));
return Size;
}
ObjectSizeOffsetVisitor::ObjectSizeOffsetVisitor(const DataLayout &DL,
const TargetLibraryInfo *TLI,
LLVMContext &Context,
bool RoundToAlign,
ObjSizeMode Mode)
: DL(DL), TLI(TLI), RoundToAlign(RoundToAlign), Mode(Mode) {
// 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));
}
DEBUG(dbgs() << "ObjectSizeOffsetVisitor::compute() unhandled value: " << *V
<< '\n');
return unknown();
}
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)) {
Size *= C->getValue().zextOrSelf(IntTyBits);
return 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 =
getAllocationData(CS.getInstruction(), AnyAlloc, 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();
// 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.
auto 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;
};
APInt Size = Arg->getValue();
if (!CheckedZextOrTrunc(Size))
return unknown();
// size 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&) {
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.getType()->getElementType()));
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 (Mode == ObjSizeMode::Min) {
if (TrueResult.slt(FalseResult))
return TrueSide;
return FalseSide;
}
if (Mode == ObjSizeMode::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) {
DEBUG(dbgs() << "ObjectSizeOffsetVisitor unknown instruction:" << I << '\n');
return unknown();
}
ObjectSizeOffsetEvaluator::ObjectSizeOffsetEvaluator(
const DataLayout &DL, const TargetLibraryInfo *TLI, LLVMContext &Context,
bool RoundToAlign)
: DL(DL), TLI(TLI), Context(Context), Builder(Context, TargetFolder(DL)),
RoundToAlign(RoundToAlign) {
// 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 (PtrSetTy::iterator I=SeenVals.begin(), E=SeenVals.end(); I != E; ++I) {
CacheMapTy::iterator CacheIt = CacheMap.find(*I);
// non-computable results can be safely cached
if (CacheIt != CacheMap.end() && anyKnown(CacheIt->second))
CacheMap.erase(CacheIt);
}
}
SeenVals.clear();
return Result;
}
SizeOffsetEvalType ObjectSizeOffsetEvaluator::compute_(Value *V) {
ObjectSizeOffsetVisitor Visitor(DL, TLI, Context, RoundToAlign);
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 what ObjectSizeVisitor can
Result = unknown();
} else {
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 =
getAllocationData(CS.getInstruction(), AnyAlloc, 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();
SizePHI->replaceAllUsesWith(UndefValue::get(IntTy));
SizePHI->eraseFromParent();
return unknown();
}
SizePHI->addIncoming(EdgeData.first, PHI.getIncomingBlock(i));
OffsetPHI->addIncoming(EdgeData.second, PHI.getIncomingBlock(i));
}
Value *Size = SizePHI, *Offset = OffsetPHI, *Tmp;
if ((Tmp = SizePHI->hasConstantValue())) {
Size = Tmp;
SizePHI->replaceAllUsesWith(Size);
SizePHI->eraseFromParent();
}
if ((Tmp = OffsetPHI->hasConstantValue())) {
Offset = Tmp;
OffsetPHI->replaceAllUsesWith(Offset);
OffsetPHI->eraseFromParent();
}
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) {
DEBUG(dbgs() << "ObjectSizeOffsetEvaluator unknown instruction:" << I <<'\n');
return unknown();
}
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