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llvm/lib/Analysis/IPA/GlobalsModRef.cpp
Chandler Carruth 52ab0bc417 [PM/AA] Extract the ModRef enums from the AliasAnalysis class in 
preparation for de-coupling the AA implementations.

In order to do this, they had to become fake-scoped using the
traditional LLVM pattern of a leading initialism. These can't be actual
scoped enumerations because they're bitfields and thus inherently we use
them as integers.

I've also renamed the behavior enums that are specific to reasoning
about the mod/ref behavior of functions when called. This makes it more
clear that they have a very narrow domain of applicability.

I think there is a significantly cleaner API for all of this, but
I don't want to try to do really substantive changes for now, I just
want to refactor the things away from analysis groups so I'm preserving
the exact original design and just cleaning up the names, style, and
lifting out of the class.

Differential Revision: http://reviews.llvm.org/D10564

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@242963 91177308-0d34-0410-b5e6-96231b3b80d8
2015-07-22 23:15:57 +00:00

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//===- GlobalsModRef.cpp - Simple Mod/Ref Analysis for Globals ------------===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This simple pass provides alias and mod/ref information for global values
// that do not have their address taken, and keeps track of whether functions
// read or write memory (are "pure"). For this simple (but very common) case,
// we can provide pretty accurate and useful information.
//
//===----------------------------------------------------------------------===//
#include "llvm/Analysis/Passes.h"
#include "llvm/ADT/SCCIterator.h"
#include "llvm/ADT/SmallPtrSet.h"
#include "llvm/ADT/Statistic.h"
#include "llvm/Analysis/AliasAnalysis.h"
#include "llvm/Analysis/CallGraph.h"
#include "llvm/Analysis/MemoryBuiltins.h"
#include "llvm/Analysis/ValueTracking.h"
#include "llvm/IR/Constants.h"
#include "llvm/IR/DerivedTypes.h"
#include "llvm/IR/InstIterator.h"
#include "llvm/IR/Instructions.h"
#include "llvm/IR/IntrinsicInst.h"
#include "llvm/IR/Module.h"
#include "llvm/Pass.h"
#include "llvm/Support/CommandLine.h"
#include <list>
using namespace llvm;
#define DEBUG_TYPE "globalsmodref-aa"
STATISTIC(NumNonAddrTakenGlobalVars,
"Number of global vars without address taken");
STATISTIC(NumNonAddrTakenFunctions,"Number of functions without address taken");
STATISTIC(NumNoMemFunctions, "Number of functions that do not access memory");
STATISTIC(NumReadMemFunctions, "Number of functions that only read memory");
STATISTIC(NumIndirectGlobalVars, "Number of indirect global objects");
// An option to enable unsafe alias results from the GlobalsModRef analysis.
// When enabled, GlobalsModRef will provide no-alias results which in extremely
// rare cases may not be conservatively correct. In particular, in the face of
// transforms which cause assymetry between how effective GetUnderlyingObject
// is for two pointers, it may produce incorrect results.
//
// These unsafe results have been returned by GMR for many years without
// causing significant issues in the wild and so we provide a mechanism to
// re-enable them for users of LLVM that have a particular performance
// sensitivity and no known issues. The option also makes it easy to evaluate
// the performance impact of these results.
static cl::opt<bool> EnableUnsafeGlobalsModRefAliasResults(
"enable-unsafe-globalsmodref-alias-results", cl::init(false), cl::Hidden);
namespace {
/// FunctionRecord - One instance of this structure is stored for every
/// function in the program. Later, the entries for these functions are
/// removed if the function is found to call an external function (in which
/// case we know nothing about it.
struct FunctionRecord {
/// GlobalInfo - Maintain mod/ref info for all of the globals without
/// addresses taken that are read or written (transitively) by this
/// function.
std::map<const GlobalValue *, unsigned> GlobalInfo;
/// MayReadAnyGlobal - May read global variables, but it is not known which.
bool MayReadAnyGlobal;
unsigned getInfoForGlobal(const GlobalValue *GV) const {
unsigned Effect = MayReadAnyGlobal ? MRI_Ref : 0;
std::map<const GlobalValue *, unsigned>::const_iterator I =
GlobalInfo.find(GV);
if (I != GlobalInfo.end())
Effect |= I->second;
return Effect;
}
/// FunctionEffect - Capture whether or not this function reads or writes to
/// ANY memory. If not, we can do a lot of aggressive analysis on it.
unsigned FunctionEffect;
FunctionRecord() : MayReadAnyGlobal(false), FunctionEffect(0) {}
};
/// GlobalsModRef - The actual analysis pass.
class GlobalsModRef : public ModulePass, public AliasAnalysis {
/// The globals that do not have their addresses taken.
SmallPtrSet<const GlobalValue *, 8> NonAddressTakenGlobals;
/// IndirectGlobals - The memory pointed to by this global is known to be
/// 'owned' by the global.
SmallPtrSet<const GlobalValue *, 8> IndirectGlobals;
/// AllocsForIndirectGlobals - If an instruction allocates memory for an
/// indirect global, this map indicates which one.
DenseMap<const Value *, const GlobalValue *> AllocsForIndirectGlobals;
/// FunctionInfo - For each function, keep track of what globals are
/// modified or read.
DenseMap<const Function *, FunctionRecord> FunctionInfo;
/// Handle to clear this analysis on deletion of values.
struct DeletionCallbackHandle final : CallbackVH {
GlobalsModRef &GMR;
std::list<DeletionCallbackHandle>::iterator I;
DeletionCallbackHandle(GlobalsModRef &GMR, Value *V)
: CallbackVH(V), GMR(GMR) {}
void deleted() override {
Value *V = getValPtr();
if (GlobalValue *GV = dyn_cast<GlobalValue>(V)) {
if (GMR.NonAddressTakenGlobals.erase(GV)) {
// This global might be an indirect global. If so, remove it and
// remove
// any AllocRelatedValues for it.
if (GMR.IndirectGlobals.erase(GV)) {
// Remove any entries in AllocsForIndirectGlobals for this global.
for (auto I = GMR.AllocsForIndirectGlobals.begin(),
E = GMR.AllocsForIndirectGlobals.end();
I != E; ++I)
if (I->second == GV)
GMR.AllocsForIndirectGlobals.erase(I);
}
}
}
// If this is an allocation related to an indirect global, remove it.
GMR.AllocsForIndirectGlobals.erase(V);
// And clear out the handle.
setValPtr(nullptr);
GMR.Handles.erase(I);
// This object is now destroyed!
}
};
/// List of callbacks for globals being tracked by this analysis. Note that
/// these objects are quite large, but we only anticipate having one per
/// global tracked by this analysis. There are numerous optimizations we
/// could perform to the memory utilization here if this becomes a problem.
std::list<DeletionCallbackHandle> Handles;
public:
static char ID;
GlobalsModRef() : ModulePass(ID) {
initializeGlobalsModRefPass(*PassRegistry::getPassRegistry());
}
bool runOnModule(Module &M) override {
InitializeAliasAnalysis(this, &M.getDataLayout());
// Find non-addr taken globals.
AnalyzeGlobals(M);
// Propagate on CG.
AnalyzeCallGraph(getAnalysis<CallGraphWrapperPass>().getCallGraph(), M);
return false;
}
void getAnalysisUsage(AnalysisUsage &AU) const override {
AliasAnalysis::getAnalysisUsage(AU);
AU.addRequired<CallGraphWrapperPass>();
AU.setPreservesAll(); // Does not transform code
}
/// getAdjustedAnalysisPointer - This method is used when a pass implements
/// an analysis interface through multiple inheritance. If needed, it
/// should override this to adjust the this pointer as needed for the
/// specified pass info.
void *getAdjustedAnalysisPointer(AnalysisID PI) override {
if (PI == &AliasAnalysis::ID)
return (AliasAnalysis *)this;
return this;
}
//------------------------------------------------
// Implement the AliasAnalysis API
//
AliasResult alias(const MemoryLocation &LocA,
const MemoryLocation &LocB) override;
ModRefInfo getModRefInfo(ImmutableCallSite CS,
const MemoryLocation &Loc) override;
ModRefInfo getModRefInfo(ImmutableCallSite CS1,
ImmutableCallSite CS2) override {
return AliasAnalysis::getModRefInfo(CS1, CS2);
}
/// getModRefBehavior - Return the behavior of the specified function if
/// called from the specified call site. The call site may be null in which
/// case the most generic behavior of this function should be returned.
FunctionModRefBehavior getModRefBehavior(const Function *F) override {
FunctionModRefBehavior Min = FMRB_UnknownModRefBehavior;
if (FunctionRecord *FR = getFunctionInfo(F)) {
if (FR->FunctionEffect == 0)
Min = FMRB_DoesNotAccessMemory;
else if ((FR->FunctionEffect & MRI_Mod) == 0)
Min = FMRB_OnlyReadsMemory;
}
return FunctionModRefBehavior(AliasAnalysis::getModRefBehavior(F) & Min);
}
/// getModRefBehavior - Return the behavior of the specified function if
/// called from the specified call site. The call site may be null in which
/// case the most generic behavior of this function should be returned.
FunctionModRefBehavior getModRefBehavior(ImmutableCallSite CS) override {
FunctionModRefBehavior Min = FMRB_UnknownModRefBehavior;
if (const Function *F = CS.getCalledFunction())
if (FunctionRecord *FR = getFunctionInfo(F)) {
if (FR->FunctionEffect == 0)
Min = FMRB_DoesNotAccessMemory;
else if ((FR->FunctionEffect & MRI_Mod) == 0)
Min = FMRB_OnlyReadsMemory;
}
return FunctionModRefBehavior(AliasAnalysis::getModRefBehavior(CS) & Min);
}
private:
/// getFunctionInfo - Return the function info for the function, or null if
/// we don't have anything useful to say about it.
FunctionRecord *getFunctionInfo(const Function *F) {
auto I = FunctionInfo.find(F);
if (I != FunctionInfo.end())
return &I->second;
return nullptr;
}
void AnalyzeGlobals(Module &M);
void AnalyzeCallGraph(CallGraph &CG, Module &M);
bool AnalyzeUsesOfPointer(Value *V,
SmallPtrSetImpl<Function *> *Readers = nullptr,
SmallPtrSetImpl<Function *> *Writers = nullptr,
GlobalValue *OkayStoreDest = nullptr);
bool AnalyzeIndirectGlobalMemory(GlobalValue *GV);
};
}
char GlobalsModRef::ID = 0;
INITIALIZE_AG_PASS_BEGIN(GlobalsModRef, AliasAnalysis, "globalsmodref-aa",
"Simple mod/ref analysis for globals", false, true,
false)
INITIALIZE_PASS_DEPENDENCY(CallGraphWrapperPass)
INITIALIZE_AG_PASS_END(GlobalsModRef, AliasAnalysis, "globalsmodref-aa",
"Simple mod/ref analysis for globals", false, true,
false)
Pass *llvm::createGlobalsModRefPass() { return new GlobalsModRef(); }
/// AnalyzeGlobals - Scan through the users of all of the internal
/// GlobalValue's in the program. If none of them have their "address taken"
/// (really, their address passed to something nontrivial), record this fact,
/// and record the functions that they are used directly in.
void GlobalsModRef::AnalyzeGlobals(Module &M) {
for (Function &F : M)
if (F.hasLocalLinkage())
if (!AnalyzeUsesOfPointer(&F)) {
// Remember that we are tracking this global.
NonAddressTakenGlobals.insert(&F);
Handles.emplace_front(*this, &F);
Handles.front().I = Handles.begin();
++NumNonAddrTakenFunctions;
}
SmallPtrSet<Function *, 64> Readers, Writers;
for (GlobalVariable &GV : M.globals())
if (GV.hasLocalLinkage()) {
if (!AnalyzeUsesOfPointer(&GV, &Readers,
GV.isConstant() ? nullptr : &Writers)) {
// Remember that we are tracking this global, and the mod/ref fns
NonAddressTakenGlobals.insert(&GV);
Handles.emplace_front(*this, &GV);
Handles.front().I = Handles.begin();
for (Function *Reader : Readers)
FunctionInfo[Reader].GlobalInfo[&GV] |= MRI_Ref;
if (!GV.isConstant()) // No need to keep track of writers to constants
for (Function *Writer : Writers)
FunctionInfo[Writer].GlobalInfo[&GV] |= MRI_Mod;
++NumNonAddrTakenGlobalVars;
// If this global holds a pointer type, see if it is an indirect global.
if (GV.getType()->getElementType()->isPointerTy() &&
AnalyzeIndirectGlobalMemory(&GV))
++NumIndirectGlobalVars;
}
Readers.clear();
Writers.clear();
}
}
/// AnalyzeUsesOfPointer - Look at all of the users of the specified pointer.
/// If this is used by anything complex (i.e., the address escapes), return
/// true. Also, while we are at it, keep track of those functions that read and
/// write to the value.
///
/// If OkayStoreDest is non-null, stores into this global are allowed.
bool GlobalsModRef::AnalyzeUsesOfPointer(Value *V,
SmallPtrSetImpl<Function *> *Readers,
SmallPtrSetImpl<Function *> *Writers,
GlobalValue *OkayStoreDest) {
if (!V->getType()->isPointerTy())
return true;
for (Use &U : V->uses()) {
User *I = U.getUser();
if (LoadInst *LI = dyn_cast<LoadInst>(I)) {
if (Readers)
Readers->insert(LI->getParent()->getParent());
} else if (StoreInst *SI = dyn_cast<StoreInst>(I)) {
if (V == SI->getOperand(1)) {
if (Writers)
Writers->insert(SI->getParent()->getParent());
} else if (SI->getOperand(1) != OkayStoreDest) {
return true; // Storing the pointer
}
} else if (Operator::getOpcode(I) == Instruction::GetElementPtr) {
if (AnalyzeUsesOfPointer(I, Readers, Writers))
return true;
} else if (Operator::getOpcode(I) == Instruction::BitCast) {
if (AnalyzeUsesOfPointer(I, Readers, Writers, OkayStoreDest))
return true;
} else if (auto CS = CallSite(I)) {
// Make sure that this is just the function being called, not that it is
// passing into the function.
if (!CS.isCallee(&U)) {
// Detect calls to free.
if (isFreeCall(I, TLI)) {
if (Writers)
Writers->insert(CS->getParent()->getParent());
} else {
return true; // Argument of an unknown call.
}
}
} else if (ICmpInst *ICI = dyn_cast<ICmpInst>(I)) {
if (!isa<ConstantPointerNull>(ICI->getOperand(1)))
return true; // Allow comparison against null.
} else {
return true;
}
}
return false;
}
/// AnalyzeIndirectGlobalMemory - We found an non-address-taken global variable
/// which holds a pointer type. See if the global always points to non-aliased
/// heap memory: that is, all initializers of the globals are allocations, and
/// those allocations have no use other than initialization of the global.
/// Further, all loads out of GV must directly use the memory, not store the
/// pointer somewhere. If this is true, we consider the memory pointed to by
/// GV to be owned by GV and can disambiguate other pointers from it.
bool GlobalsModRef::AnalyzeIndirectGlobalMemory(GlobalValue *GV) {
// Keep track of values related to the allocation of the memory, f.e. the
// value produced by the malloc call and any casts.
std::vector<Value *> AllocRelatedValues;
// Walk the user list of the global. If we find anything other than a direct
// load or store, bail out.
for (User *U : GV->users()) {
if (LoadInst *LI = dyn_cast<LoadInst>(U)) {
// The pointer loaded from the global can only be used in simple ways:
// we allow addressing of it and loading storing to it. We do *not* allow
// storing the loaded pointer somewhere else or passing to a function.
if (AnalyzeUsesOfPointer(LI))
return false; // Loaded pointer escapes.
// TODO: Could try some IP mod/ref of the loaded pointer.
} else if (StoreInst *SI = dyn_cast<StoreInst>(U)) {
// Storing the global itself.
if (SI->getOperand(0) == GV)
return false;
// If storing the null pointer, ignore it.
if (isa<ConstantPointerNull>(SI->getOperand(0)))
continue;
// Check the value being stored.
Value *Ptr = GetUnderlyingObject(SI->getOperand(0),
GV->getParent()->getDataLayout());
if (!isAllocLikeFn(Ptr, TLI))
return false; // Too hard to analyze.
// Analyze all uses of the allocation. If any of them are used in a
// non-simple way (e.g. stored to another global) bail out.
if (AnalyzeUsesOfPointer(Ptr, /*Readers*/ nullptr, /*Writers*/ nullptr,
GV))
return false; // Loaded pointer escapes.
// Remember that this allocation is related to the indirect global.
AllocRelatedValues.push_back(Ptr);
} else {
// Something complex, bail out.
return false;
}
}
// Okay, this is an indirect global. Remember all of the allocations for
// this global in AllocsForIndirectGlobals.
while (!AllocRelatedValues.empty()) {
AllocsForIndirectGlobals[AllocRelatedValues.back()] = GV;
Handles.emplace_front(*this, AllocRelatedValues.back());
Handles.front().I = Handles.begin();
AllocRelatedValues.pop_back();
}
IndirectGlobals.insert(GV);
Handles.emplace_front(*this, GV);
Handles.front().I = Handles.begin();
return true;
}
/// AnalyzeCallGraph - At this point, we know the functions where globals are
/// immediately stored to and read from. Propagate this information up the call
/// graph to all callers and compute the mod/ref info for all memory for each
/// function.
void GlobalsModRef::AnalyzeCallGraph(CallGraph &CG, Module &M) {
// We do a bottom-up SCC traversal of the call graph. In other words, we
// visit all callees before callers (leaf-first).
for (scc_iterator<CallGraph *> I = scc_begin(&CG); !I.isAtEnd(); ++I) {
const std::vector<CallGraphNode *> &SCC = *I;
assert(!SCC.empty() && "SCC with no functions?");
if (!SCC[0]->getFunction()) {
// Calls externally - can't say anything useful. Remove any existing
// function records (may have been created when scanning globals).
for (auto *Node : SCC)
FunctionInfo.erase(Node->getFunction());
continue;
}
FunctionRecord &FR = FunctionInfo[SCC[0]->getFunction()];
bool KnowNothing = false;
unsigned FunctionEffect = 0;
// Collect the mod/ref properties due to called functions. We only compute
// one mod-ref set.
for (unsigned i = 0, e = SCC.size(); i != e && !KnowNothing; ++i) {
Function *F = SCC[i]->getFunction();
if (!F) {
KnowNothing = true;
break;
}
if (F->isDeclaration()) {
// Try to get mod/ref behaviour from function attributes.
if (F->doesNotAccessMemory()) {
// Can't do better than that!
} else if (F->onlyReadsMemory()) {
FunctionEffect |= MRI_Ref;
if (!F->isIntrinsic())
// This function might call back into the module and read a global -
// consider every global as possibly being read by this function.
FR.MayReadAnyGlobal = true;
} else {
FunctionEffect |= MRI_ModRef;
// Can't say anything useful unless it's an intrinsic - they don't
// read or write global variables of the kind considered here.
KnowNothing = !F->isIntrinsic();
}
continue;
}
for (CallGraphNode::iterator CI = SCC[i]->begin(), E = SCC[i]->end();
CI != E && !KnowNothing; ++CI)
if (Function *Callee = CI->second->getFunction()) {
if (FunctionRecord *CalleeFR = getFunctionInfo(Callee)) {
// Propagate function effect up.
FunctionEffect |= CalleeFR->FunctionEffect;
// Incorporate callee's effects on globals into our info.
for (const auto &G : CalleeFR->GlobalInfo)
FR.GlobalInfo[G.first] |= G.second;
FR.MayReadAnyGlobal |= CalleeFR->MayReadAnyGlobal;
} else {
// Can't say anything about it. However, if it is inside our SCC,
// then nothing needs to be done.
CallGraphNode *CalleeNode = CG[Callee];
if (std::find(SCC.begin(), SCC.end(), CalleeNode) == SCC.end())
KnowNothing = true;
}
} else {
KnowNothing = true;
}
}
// If we can't say anything useful about this SCC, remove all SCC functions
// from the FunctionInfo map.
if (KnowNothing) {
for (auto *Node : SCC)
FunctionInfo.erase(Node->getFunction());
continue;
}
// Scan the function bodies for explicit loads or stores.
for (auto *Node : SCC) {
if (FunctionEffect == MRI_ModRef)
break; // The mod/ref lattice saturates here.
for (Instruction &I : inst_range(Node->getFunction())) {
if (FunctionEffect == MRI_ModRef)
break; // The mod/ref lattice saturates here.
// We handle calls specially because the graph-relevant aspects are
// handled above.
if (auto CS = CallSite(&I)) {
if (isAllocationFn(&I, TLI) || isFreeCall(&I, TLI)) {
// FIXME: It is completely unclear why this is necessary and not
// handled by the above graph code.
FunctionEffect |= MRI_ModRef;
} else if (Function *Callee = CS.getCalledFunction()) {
// The callgraph doesn't include intrinsic calls.
if (Callee->isIntrinsic()) {
FunctionModRefBehavior Behaviour =
AliasAnalysis::getModRefBehavior(Callee);
FunctionEffect |= (Behaviour & MRI_ModRef);
}
}
continue;
}
// All non-call instructions we use the primary predicates for whether
// thay read or write memory.
if (I.mayReadFromMemory())
FunctionEffect |= MRI_Ref;
if (I.mayWriteToMemory())
FunctionEffect |= MRI_Mod;
}
}
if ((FunctionEffect & MRI_Mod) == 0)
++NumReadMemFunctions;
if (FunctionEffect == 0)
++NumNoMemFunctions;
FR.FunctionEffect = FunctionEffect;
// Finally, now that we know the full effect on this SCC, clone the
// information to each function in the SCC.
for (unsigned i = 1, e = SCC.size(); i != e; ++i)
FunctionInfo[SCC[i]->getFunction()] = FR;
}
}
/// alias - If one of the pointers is to a global that we are tracking, and the
/// other is some random pointer, we know there cannot be an alias, because the
/// address of the global isn't taken.
AliasResult GlobalsModRef::alias(const MemoryLocation &LocA,
const MemoryLocation &LocB) {
// Get the base object these pointers point to.
const Value *UV1 = GetUnderlyingObject(LocA.Ptr, *DL);
const Value *UV2 = GetUnderlyingObject(LocB.Ptr, *DL);
// If either of the underlying values is a global, they may be non-addr-taken
// globals, which we can answer queries about.
const GlobalValue *GV1 = dyn_cast<GlobalValue>(UV1);
const GlobalValue *GV2 = dyn_cast<GlobalValue>(UV2);
if (GV1 || GV2) {
// If the global's address is taken, pretend we don't know it's a pointer to
// the global.
if (GV1 && !NonAddressTakenGlobals.count(GV1))
GV1 = nullptr;
if (GV2 && !NonAddressTakenGlobals.count(GV2))
GV2 = nullptr;
// If the two pointers are derived from two different non-addr-taken
// globals we know these can't alias.
if (GV1 && GV2 && GV1 != GV2)
return NoAlias;
// If one is and the other isn't, it isn't strictly safe but we can fake
// this result if necessary for performance. This does not appear to be
// a common problem in practice.
if (EnableUnsafeGlobalsModRefAliasResults)
if ((GV1 || GV2) && GV1 != GV2)
return NoAlias;
// Otherwise if they are both derived from the same addr-taken global, we
// can't know the two accesses don't overlap.
}
// These pointers may be based on the memory owned by an indirect global. If
// so, we may be able to handle this. First check to see if the base pointer
// is a direct load from an indirect global.
GV1 = GV2 = nullptr;
if (const LoadInst *LI = dyn_cast<LoadInst>(UV1))
if (GlobalVariable *GV = dyn_cast<GlobalVariable>(LI->getOperand(0)))
if (IndirectGlobals.count(GV))
GV1 = GV;
if (const LoadInst *LI = dyn_cast<LoadInst>(UV2))
if (const GlobalVariable *GV = dyn_cast<GlobalVariable>(LI->getOperand(0)))
if (IndirectGlobals.count(GV))
GV2 = GV;
// These pointers may also be from an allocation for the indirect global. If
// so, also handle them.
if (!GV1)
GV1 = AllocsForIndirectGlobals.lookup(UV1);
if (!GV2)
GV2 = AllocsForIndirectGlobals.lookup(UV2);
// Now that we know whether the two pointers are related to indirect globals,
// use this to disambiguate the pointers. If the pointers are based on
// different indirect globals they cannot alias.
if (GV1 && GV2 && GV1 != GV2)
return NoAlias;
// If one is based on an indirect global and the other isn't, it isn't
// strictly safe but we can fake this result if necessary for performance.
// This does not appear to be a common problem in practice.
if (EnableUnsafeGlobalsModRefAliasResults)
if ((GV1 || GV2) && GV1 != GV2)
return NoAlias;
return AliasAnalysis::alias(LocA, LocB);
}
ModRefInfo GlobalsModRef::getModRefInfo(ImmutableCallSite CS,
const MemoryLocation &Loc) {
unsigned Known = MRI_ModRef;
// If we are asking for mod/ref info of a direct call with a pointer to a
// global we are tracking, return information if we have it.
const DataLayout &DL = CS.getCaller()->getParent()->getDataLayout();
if (const GlobalValue *GV =
dyn_cast<GlobalValue>(GetUnderlyingObject(Loc.Ptr, DL)))
if (GV->hasLocalLinkage())
if (const Function *F = CS.getCalledFunction())
if (NonAddressTakenGlobals.count(GV))
if (const FunctionRecord *FR = getFunctionInfo(F))
Known = FR->getInfoForGlobal(GV);
if (Known == MRI_NoModRef)
return MRI_NoModRef; // No need to query other mod/ref analyses
return ModRefInfo(Known & AliasAnalysis::getModRefInfo(CS, Loc));
}
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