X-Git-Url: http://plrg.eecs.uci.edu/git/?a=blobdiff_plain;f=lib%2FAnalysis%2FBasicAliasAnalysis.cpp;h=200779f0e7aef7e760221c33da42fdd7eafc6f69;hb=851bfff50f7251e4d00b5fffbb5e140544cc4a63;hp=6aeaec23faf90e3ee20985bdaeca9b3029dd64fb;hpb=514ab348fddcdffa8367685dc608b2f8d5de986d;p=oota-llvm.git diff --git a/lib/Analysis/BasicAliasAnalysis.cpp b/lib/Analysis/BasicAliasAnalysis.cpp index 6aeaec23faf..200779f0e7a 100644 --- a/lib/Analysis/BasicAliasAnalysis.cpp +++ b/lib/Analysis/BasicAliasAnalysis.cpp @@ -2,8 +2,8 @@ // // The LLVM Compiler Infrastructure // -// This file was developed by the LLVM research group and is distributed under -// the University of Illinois Open Source License. See LICENSE.TXT for details. +// This file is distributed under the University of Illinois Open Source +// License. See LICENSE.TXT for details. // //===----------------------------------------------------------------------===// // @@ -21,12 +21,10 @@ #include "llvm/ParameterAttributes.h" #include "llvm/GlobalVariable.h" #include "llvm/Instructions.h" -#include "llvm/Intrinsics.h" +#include "llvm/IntrinsicInst.h" #include "llvm/Pass.h" #include "llvm/Target/TargetData.h" #include "llvm/ADT/SmallVector.h" -#include "llvm/ADT/StringMap.h" -#include "llvm/ADT/BitVector.h" #include "llvm/ADT/STLExtras.h" #include "llvm/Support/Compiler.h" #include "llvm/Support/GetElementPtrTypeIterator.h" @@ -116,9 +114,6 @@ namespace { /// global) or not. bool pointsToConstantMemory(const Value *P); - virtual ModRefBehavior getModRefBehavior(Function *F, CallSite CS, - std::vector *Info); - private: // CheckGEPInstructions - Check two GEP instructions with known // must-aliasing base pointers. This checks to see if the index expressions @@ -143,9 +138,10 @@ ImmutablePass *llvm::createBasicAliasAnalysisPass() { return new BasicAliasAnalysis(); } -// getUnderlyingObject - This traverses the use chain to figure out what object -// the specified value points to. If the value points to, or is derived from, a -// unique object or an argument, return it. +/// getUnderlyingObject - This traverses the use chain to figure out what object +/// the specified value points to. If the value points to, or is derived from, +/// a unique object or an argument, return it. This returns: +/// Arguments, GlobalVariables, Functions, Allocas, Mallocs. static const Value *getUnderlyingObject(const Value *V) { if (!isa(V->getType())) return 0; @@ -223,8 +219,6 @@ static bool AddressMightEscape(const Value *V) { return true; break; // next use. case Instruction::BitCast: - if (!isa(I->getType())) - return true; if (AddressMightEscape(I)) return true; break; // next use @@ -232,6 +226,12 @@ static bool AddressMightEscape(const Value *V) { // If returned, the address will escape to calling functions, but no // callees could modify it. break; // next use + case Instruction::Call: + // If the call is to a few known safe intrinsics, we know that it does + // not escape + if (!isa(I)) + return true; + break; // next use default: return true; } @@ -246,41 +246,45 @@ static bool AddressMightEscape(const Value *V) { // AliasAnalysis::ModRefResult BasicAliasAnalysis::getModRefInfo(CallSite CS, Value *P, unsigned Size) { - if (!isa(P)) - if (const AllocationInst *AI = - dyn_cast_or_null(getUnderlyingObject(P))) { - // Okay, the pointer is to a stack allocated object. If we can prove that - // the pointer never "escapes", then we know the call cannot clobber it, - // because it simply can't get its address. - if (!AddressMightEscape(AI)) - return NoModRef; + if (!isa(P)) { + const Value *Object = getUnderlyingObject(P); + // Allocations and byval arguments are "new" objects. + if (Object && + (isa(Object) || isa(Object))) { + // Okay, the pointer is to a stack allocated (or effectively so, for + // for noalias parameters) object. If the address of this object doesn't + // escape from this function body to a callee, then we know that no + // callees can mod/ref it unless they are actually passed it. + if (isa(Object) || + cast(Object)->hasByValAttr() || + cast(Object)->hasNoAliasAttr()) + if (!AddressMightEscape(Object)) { + bool passedAsArg = false; + for (CallSite::arg_iterator CI = CS.arg_begin(), CE = CS.arg_end(); + CI != CE; ++CI) + if (isa((*CI)->getType()) && + ( getUnderlyingObject(*CI) == P || + alias(cast(CI), ~0ULL, P, ~0ULL) != NoAlias) ) + passedAsArg = true; + + if (!passedAsArg) + return NoModRef; + } // If this is a tail call and P points to a stack location, we know that // the tail call cannot access or modify the local stack. - if (CallInst *CI = dyn_cast(CS.getInstruction())) - if (CI->isTailCall() && isa(AI)) - return NoModRef; + if (isa(Object) || + (isa(Object) && cast(Object)->hasByValAttr())) + if (CallInst *CI = dyn_cast(CS.getInstruction())) + if (CI->isTailCall()) + return NoModRef; } + } // The AliasAnalysis base class has some smarts, lets use them. return AliasAnalysis::getModRefInfo(CS, P, Size); } -static bool isNoAliasArgument(const Argument *Arg) { - const Function *Func = Arg->getParent(); - const ParamAttrsList *Attr = Func->getFunctionType()->getParamAttrs(); - if (Attr) { - unsigned Idx = 1; - for (Function::const_arg_iterator I = Func->arg_begin(), - E = Func->arg_end(); I != E; ++I, ++Idx) { - if (&(*I) == Arg && - Attr->paramHasAttr(Idx, ParamAttr::NoAlias)) - return true; - } - } - return false; -} - // alias - Provide a bunch of ad-hoc rules to disambiguate in common cases, such // as array references. Note that this function is heavily tail recursive. // Hopefully we have a smart C++ compiler. :) @@ -322,9 +326,12 @@ BasicAliasAnalysis::alias(const Value *V1, unsigned V1Size, // If they are two different objects, and one is a noalias argument // then they do not alias. - if (O1 != O2 && isNoAliasArgument(O1Arg)) + if (O1 != O2 && O1Arg->hasNoAliasAttr()) return NoAlias; - + + // Byval arguments can't alias globals or other arguments. + if (O1 != O2 && O1Arg->hasByValAttr()) return NoAlias; + // Otherwise, nothing is known... } @@ -334,16 +341,18 @@ BasicAliasAnalysis::alias(const Value *V1, unsigned V1Size, // If they are two different objects, and one is a noalias argument // then they do not alias. - if (O1 != O2 && isNoAliasArgument(O2Arg)) + if (O1 != O2 && O2Arg->hasNoAliasAttr()) return NoAlias; + // Byval arguments can't alias globals or other arguments. + if (O1 != O2 && O2Arg->hasByValAttr()) return NoAlias; + // Otherwise, nothing is known... - } else if (O1 != O2) { - if (!isa(O1)) - // If they are two different objects, and neither is an argument, - // we know that we have no alias... - return NoAlias; + } else if (O1 != O2 && !isa(O1)) { + // If they are two different objects, and neither is an argument, + // we know that we have no alias. + return NoAlias; } // If they are the same object, they we can look at the indexes. If they @@ -352,9 +361,15 @@ BasicAliasAnalysis::alias(const Value *V1, unsigned V1Size, // can't tell anything. } - - if (!isa(O1) && isa(V2)) - return NoAlias; // Unique values don't alias null + // Unique values don't alias null, except non-byval arguments. + if (isa(V2)) { + if (const Argument *O1Arg = dyn_cast(O1)) { + if (O1Arg->hasByValAttr()) + return NoAlias; + } else { + return NoAlias; + } + } if (isa(O1) || (isa(O1) && @@ -396,17 +411,19 @@ BasicAliasAnalysis::alias(const Value *V1, unsigned V1Size, if (isGEP(V1) && isGEP(V2)) { // Drill down into the first non-gep value, to test for must-aliasing of // the base pointers. - const Value *BasePtr1 = V1, *BasePtr2 = V2; - do { - BasePtr1 = cast(BasePtr1)->getOperand(0); - } while (isGEP(BasePtr1) && - cast(BasePtr1)->getOperand(1) == - Constant::getNullValue(cast(BasePtr1)->getOperand(1)->getType())); - do { - BasePtr2 = cast(BasePtr2)->getOperand(0); - } while (isGEP(BasePtr2) && - cast(BasePtr2)->getOperand(1) == - Constant::getNullValue(cast(BasePtr2)->getOperand(1)->getType())); + const User *G = cast(V1); + while (isGEP(G->getOperand(0)) && + G->getOperand(1) == + Constant::getNullValue(G->getOperand(1)->getType())) + G = cast(G->getOperand(0)); + const Value *BasePtr1 = G->getOperand(0); + + G = cast(V2); + while (isGEP(G->getOperand(0)) && + G->getOperand(1) == + Constant::getNullValue(G->getOperand(1)->getType())) + G = cast(G->getOperand(0)); + const Value *BasePtr2 = G->getOperand(0); // Do the base pointers alias? AliasResult BaseAlias = alias(BasePtr1, ~0U, BasePtr2, ~0U); @@ -735,8 +752,8 @@ BasicAliasAnalysis::CheckGEPInstructions( if (const ArrayType *AT = dyn_cast(BasePtr1Ty)) { if (Op1C->getZExtValue() >= AT->getNumElements()) return MayAlias; // Be conservative with out-of-range accesses - } else if (const VectorType *PT = dyn_cast(BasePtr1Ty)) { - if (Op1C->getZExtValue() >= PT->getNumElements()) + } else if (const VectorType *VT = dyn_cast(BasePtr1Ty)) { + if (Op1C->getZExtValue() >= VT->getNumElements()) return MayAlias; // Be conservative with out-of-range accesses } @@ -753,20 +770,19 @@ BasicAliasAnalysis::CheckGEPInstructions( // if (const ArrayType *AT = dyn_cast(BasePtr1Ty)) GEP1Ops[i] = ConstantInt::get(Type::Int64Ty,AT->getNumElements()-1); - else if (const VectorType *PT = dyn_cast(BasePtr1Ty)) - GEP1Ops[i] = ConstantInt::get(Type::Int64Ty,PT->getNumElements()-1); - + else if (const VectorType *VT = dyn_cast(BasePtr1Ty)) + GEP1Ops[i] = ConstantInt::get(Type::Int64Ty,VT->getNumElements()-1); } } if (Op2) { if (const ConstantInt *Op2C = dyn_cast(Op2)) { // If this is an array index, make sure the array element is in range. - if (const ArrayType *AT = dyn_cast(BasePtr1Ty)) { + if (const ArrayType *AT = dyn_cast(BasePtr2Ty)) { if (Op2C->getZExtValue() >= AT->getNumElements()) return MayAlias; // Be conservative with out-of-range accesses - } else if (const VectorType *PT = dyn_cast(BasePtr1Ty)) { - if (Op2C->getZExtValue() >= PT->getNumElements()) + } else if (const VectorType *VT = dyn_cast(BasePtr2Ty)) { + if (Op2C->getZExtValue() >= VT->getNumElements()) return MayAlias; // Be conservative with out-of-range accesses } } else { // Conservatively assume the minimum value for this index @@ -795,8 +811,13 @@ BasicAliasAnalysis::CheckGEPInstructions( getTargetData().getIndexedOffset(GEPPointerTy, GEP1Ops, NumGEP1Ops); int64_t Offset2 = getTargetData().getIndexedOffset(GEPPointerTy, GEP2Ops, NumGEP2Ops); - assert(Offset1 Offset2) + std::swap(Offset1, Offset2); + if ((uint64_t)(Offset2-Offset1) >= SizeMax) { //cerr << "Determined that these two GEP's don't alias [" // << SizeMax << " bytes]: \n" << *GEP1 << *GEP2; @@ -806,147 +827,5 @@ BasicAliasAnalysis::CheckGEPInstructions( return MayAlias; } -namespace { - struct VISIBILITY_HIDDEN StringCompare { - bool operator()(const char *LHS, const char *RHS) { - return strcmp(LHS, RHS) < 0; - } - }; -} - -// Note that this list cannot contain libm functions (such as acos and sqrt) -// that set errno on a domain or other error. -static const char *DoesntAccessMemoryFns[] = { - "abs", "labs", "llabs", "imaxabs", "fabs", "fabsf", "fabsl", - "trunc", "truncf", "truncl", "ldexp", - - "atan", "atanf", "atanl", "atan2", "atan2f", "atan2l", - "cbrt", - "cos", "cosf", "cosl", - "exp", "expf", "expl", - "hypot", - "sin", "sinf", "sinl", - "tan", "tanf", "tanl", "tanh", "tanhf", "tanhl", - - "floor", "floorf", "floorl", "ceil", "ceilf", "ceill", - - // ctype.h - "isalnum", "isalpha", "iscntrl", "isdigit", "isgraph", "islower", "isprint" - "ispunct", "isspace", "isupper", "isxdigit", "tolower", "toupper", - - // wctype.h" - "iswalnum", "iswalpha", "iswcntrl", "iswdigit", "iswgraph", "iswlower", - "iswprint", "iswpunct", "iswspace", "iswupper", "iswxdigit", - - "iswctype", "towctrans", "towlower", "towupper", - - "btowc", "wctob", - - "isinf", "isnan", "finite", - - // C99 math functions - "copysign", "copysignf", "copysignd", - "nexttoward", "nexttowardf", "nexttowardd", - "nextafter", "nextafterf", "nextafterd", - - // ISO C99: - "__signbit", "__signbitf", "__signbitl", -}; - - -static const char *OnlyReadsMemoryFns[] = { - "atoi", "atol", "atof", "atoll", "atoq", "a64l", - "bcmp", "memcmp", "memchr", "memrchr", "wmemcmp", "wmemchr", - - // Strings - "strcmp", "strcasecmp", "strcoll", "strncmp", "strncasecmp", - "strchr", "strcspn", "strlen", "strpbrk", "strrchr", "strspn", "strstr", - "index", "rindex", - - // Wide char strings - "wcschr", "wcscmp", "wcscoll", "wcscspn", "wcslen", "wcsncmp", "wcspbrk", - "wcsrchr", "wcsspn", "wcsstr", - - // glibc - "alphasort", "alphasort64", "versionsort", "versionsort64", - - // C99 - "nan", "nanf", "nand", - - // File I/O - "feof", "ferror", "fileno", - "feof_unlocked", "ferror_unlocked", "fileno_unlocked" -}; - -static ManagedStatic > NoMemoryTable; -static ManagedStatic > OnlyReadsMemoryTable; - -static ManagedStatic NoMemoryIntrinsics; -static ManagedStatic OnlyReadsMemoryIntrinsics; - - -AliasAnalysis::ModRefBehavior -BasicAliasAnalysis::getModRefBehavior(Function *F, CallSite CS, - std::vector *Info) { - if (!F->isDeclaration()) return UnknownModRefBehavior; - - static bool Initialized = false; - if (!Initialized) { - NoMemoryTable->insert(NoMemoryTable->end(), - DoesntAccessMemoryFns, - array_endof(DoesntAccessMemoryFns)); - - OnlyReadsMemoryTable->insert(OnlyReadsMemoryTable->end(), - OnlyReadsMemoryFns, - array_endof(OnlyReadsMemoryFns)); - - // Sort the table the first time through. - std::sort(NoMemoryTable->begin(), NoMemoryTable->end(), StringCompare()); - std::sort(OnlyReadsMemoryTable->begin(), OnlyReadsMemoryTable->end(), - StringCompare()); - - NoMemoryIntrinsics->resize(Intrinsic::num_intrinsics); - OnlyReadsMemoryIntrinsics->resize(Intrinsic::num_intrinsics); -#define GET_MODREF_BEHAVIOR -#include "llvm/Intrinsics.gen" -#undef GET_MODREF_BEHAVIOR - - Initialized = true; - } - - // If this is an intrinsic, we can use lookup tables - if (unsigned id = F->getIntrinsicID()) { - if (NoMemoryIntrinsics->test(id)) - return DoesNotAccessMemory; - if (OnlyReadsMemoryIntrinsics->test(id)) - return OnlyReadsMemory; - - return UnknownModRefBehavior; - } - - ValueName *Name = F->getValueName(); - unsigned NameLen = Name->getKeyLength(); - const char *NamePtr = Name->getKeyData(); - - // If there is an embedded nul character in the function name, we can never - // match it. - if (strlen(NamePtr) != NameLen) - return UnknownModRefBehavior; - - std::vector::iterator Ptr = - std::lower_bound(NoMemoryTable->begin(), NoMemoryTable->end(), - NamePtr, StringCompare()); - if (Ptr != NoMemoryTable->end() && strcmp(*Ptr, NamePtr) == 0) - return DoesNotAccessMemory; - - Ptr = std::lower_bound(OnlyReadsMemoryTable->begin(), - OnlyReadsMemoryTable->end(), - NamePtr, StringCompare()); - if (Ptr != OnlyReadsMemoryTable->end() && strcmp(*Ptr, NamePtr) == 0) - return OnlyReadsMemory; - - return UnknownModRefBehavior; -} - // Make sure that anything that uses AliasAnalysis pulls in this file... DEFINING_FILE_FOR(BasicAliasAnalysis)