#include "llvm/DerivedTypes.h"
#include "llvm/Analysis/AliasAnalysis.h"
#include "llvm/Analysis/CallGraph.h"
-#include "llvm/Support/Compiler.h"
+#include "llvm/Analysis/MemoryBuiltins.h"
#include "llvm/Support/CommandLine.h"
#include "llvm/Support/InstIterator.h"
#include "llvm/ADT/Statistic.h"
/// 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 VISIBILITY_HIDDEN FunctionRecord {
+ 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<GlobalValue*, unsigned> GlobalInfo;
+ /// MayReadAnyGlobal - May read global variables, but it is not known which.
+ bool MayReadAnyGlobal;
+
unsigned getInfoForGlobal(GlobalValue *GV) const {
+ unsigned Effect = MayReadAnyGlobal ? AliasAnalysis::Ref : 0;
std::map<GlobalValue*, unsigned>::const_iterator I = GlobalInfo.find(GV);
if (I != GlobalInfo.end())
- return I->second;
- return 0;
+ 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() : FunctionEffect(0) {}
+ FunctionRecord() : MayReadAnyGlobal (false), FunctionEffect(0) {}
};
/// GlobalsModRef - The actual analysis pass.
- class VISIBILITY_HIDDEN GlobalsModRef
- : public ModulePass, public AliasAnalysis {
+ class GlobalsModRef : public ModulePass, public AliasAnalysis {
/// NonAddressTakenGlobals - The globals that do not have their addresses
/// taken.
std::set<GlobalValue*> NonAddressTakenGlobals;
/// IndirectGlobals - The memory pointed to by this global is known to be
/// 'owned' by the global.
std::set<GlobalValue*> IndirectGlobals;
-
+
/// AllocsForIndirectGlobals - If an instruction allocates memory for an
/// indirect global, this map indicates which one.
std::map<Value*, GlobalValue*> AllocsForIndirectGlobals;
-
+
/// FunctionInfo - For each function, keep track of what globals are
/// modified or read.
std::map<Function*, FunctionRecord> FunctionInfo;
public:
static char ID;
- GlobalsModRef() : ModulePass((intptr_t)&ID) {}
+ GlobalsModRef() : ModulePass(&ID) {}
bool runOnModule(Module &M) {
InitializeAliasAnalysis(this); // set up super class
ModRefResult getModRefInfo(CallSite CS1, CallSite CS2) {
return AliasAnalysis::getModRefInfo(CS1,CS2);
}
- bool hasNoModRefInfoForCalls() const { return false; }
/// 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.
- virtual ModRefBehavior getModRefBehavior(Function *F, CallSite CS,
+ ModRefBehavior getModRefBehavior(Function *F,
std::vector<PointerAccessInfo> *Info) {
- if (FunctionRecord *FR = getFunctionInfo(F))
+ if (FunctionRecord *FR = getFunctionInfo(F)) {
if (FR->FunctionEffect == 0)
return DoesNotAccessMemory;
else if ((FR->FunctionEffect & Mod) == 0)
return OnlyReadsMemory;
- return AliasAnalysis::getModRefBehavior(F, CS, Info);
+ }
+ return AliasAnalysis::getModRefBehavior(F, Info);
+ }
+
+ /// 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.
+ ModRefBehavior getModRefBehavior(CallSite CS,
+ std::vector<PointerAccessInfo> *Info) {
+ Function* F = CS.getCalledFunction();
+ if (!F) return AliasAnalysis::getModRefBehavior(CS, Info);
+ if (FunctionRecord *FR = getFunctionInfo(F)) {
+ if (FR->FunctionEffect == 0)
+ return DoesNotAccessMemory;
+ else if ((FR->FunctionEffect & Mod) == 0)
+ return OnlyReadsMemory;
+ }
+ return AliasAnalysis::getModRefBehavior(CS, Info);
}
virtual void deleteValue(Value *V);
virtual void copyValue(Value *From, Value *To);
+ /// 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.
+ virtual void *getAdjustedAnalysisPointer(const PassInfo *PI) {
+ if (PI->isPassID(&AliasAnalysis::ID))
+ return (AliasAnalysis*)this;
+ return this;
+ }
+
private:
/// getFunctionInfo - Return the function info for the function, or null if
- /// the function calls an external function (in which case we don't have
- /// anything useful to say about it).
+ /// we don't have anything useful to say about it.
FunctionRecord *getFunctionInfo(Function *F) {
std::map<Function*, FunctionRecord>::iterator I = FunctionInfo.find(F);
if (I != FunctionInfo.end())
void AnalyzeGlobals(Module &M);
void AnalyzeCallGraph(CallGraph &CG, Module &M);
- void AnalyzeSCC(std::vector<CallGraphNode *> &SCC);
bool AnalyzeUsesOfPointer(Value *V, std::vector<Function*> &Readers,
std::vector<Function*> &Writers,
GlobalValue *OkayStoreDest = 0);
bool AnalyzeIndirectGlobalMemory(GlobalValue *GV);
};
-
- char GlobalsModRef::ID = 0;
- RegisterPass<GlobalsModRef> X("globalsmodref-aa",
- "Simple mod/ref analysis for globals");
- RegisterAnalysisGroup<AliasAnalysis> Y(X);
}
-Pass *llvm::createGlobalsModRefPass() { return new GlobalsModRef(); }
+char GlobalsModRef::ID = 0;
+static RegisterPass<GlobalsModRef>
+X("globalsmodref-aa", "Simple mod/ref analysis for globals", false, true);
+static RegisterAnalysisGroup<AliasAnalysis> Y(X);
-/// 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 global object, return it.
-static Value *getUnderlyingObject(Value *V) {
- if (!isa<PointerType>(V->getType())) return V;
-
- // If we are at some type of object... return it.
- if (GlobalValue *GV = dyn_cast<GlobalValue>(V)) return GV;
-
- // Traverse through different addressing mechanisms.
- if (Instruction *I = dyn_cast<Instruction>(V)) {
- if (isa<BitCastInst>(I) || isa<GetElementPtrInst>(I))
- return getUnderlyingObject(I->getOperand(0));
- } else if (ConstantExpr *CE = dyn_cast<ConstantExpr>(V)) {
- if (CE->getOpcode() == Instruction::BitCast ||
- CE->getOpcode() == Instruction::GetElementPtr)
- return getUnderlyingObject(CE->getOperand(0));
- }
-
- // Othewise, we don't know what this is, return it as the base pointer.
- return V;
-}
+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"
+/// 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) {
std::vector<Function*> Readers, Writers;
for (Module::iterator I = M.begin(), E = M.end(); I != E; ++I)
- if (I->hasInternalLinkage()) {
+ if (I->hasLocalLinkage()) {
if (!AnalyzeUsesOfPointer(I, Readers, Writers)) {
// Remember that we are tracking this global.
NonAddressTakenGlobals.insert(I);
for (Module::global_iterator I = M.global_begin(), E = M.global_end();
I != E; ++I)
- if (I->hasInternalLinkage()) {
+ if (I->hasLocalLinkage()) {
if (!AnalyzeUsesOfPointer(I, Readers, Writers)) {
// Remember that we are tracking this global, and the mod/ref fns
NonAddressTakenGlobals.insert(I);
+
for (unsigned i = 0, e = Readers.size(); i != e; ++i)
FunctionInfo[Readers[i]].GlobalInfo[I] |= Ref;
for (unsigned i = 0, e = Writers.size(); i != e; ++i)
FunctionInfo[Writers[i]].GlobalInfo[I] |= Mod;
++NumNonAddrTakenGlobalVars;
-
+
// If this global holds a pointer type, see if it is an indirect global.
- if (isa<PointerType>(I->getType()->getElementType()) &&
+ if (I->getType()->getElementType()->isPointerTy() &&
AnalyzeIndirectGlobalMemory(I))
++NumIndirectGlobalVars;
}
std::vector<Function*> &Readers,
std::vector<Function*> &Writers,
GlobalValue *OkayStoreDest) {
- if (!isa<PointerType>(V->getType())) return true;
+ if (!V->getType()->isPointerTy()) return true;
for (Value::use_iterator UI = V->use_begin(), E = V->use_end(); UI != E; ++UI)
if (LoadInst *LI = dyn_cast<LoadInst>(*UI)) {
}
} else if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(*UI)) {
if (AnalyzeUsesOfPointer(GEP, Readers, Writers)) return true;
+ } else if (BitCastInst *BCI = dyn_cast<BitCastInst>(*UI)) {
+ if (AnalyzeUsesOfPointer(BCI, Readers, Writers, OkayStoreDest))
+ return true;
+ } else if (isFreeCall(*UI)) {
+ Writers.push_back(cast<Instruction>(*UI)->getParent()->getParent());
} else if (CallInst *CI = dyn_cast<CallInst>(*UI)) {
// Make sure that this is just the function being called, not that it is
// passing into the function.
for (unsigned i = 3, e = II->getNumOperands(); i != e; ++i)
if (II->getOperand(i) == V) return true;
} else if (ConstantExpr *CE = dyn_cast<ConstantExpr>(*UI)) {
- if (CE->getOpcode() == Instruction::GetElementPtr ||
+ if (CE->getOpcode() == Instruction::GetElementPtr ||
CE->getOpcode() == Instruction::BitCast) {
if (AnalyzeUsesOfPointer(CE, Readers, Writers))
return true;
} else if (ICmpInst *ICI = dyn_cast<ICmpInst>(*UI)) {
if (!isa<ConstantPointerNull>(ICI->getOperand(1)))
return true; // Allow comparison against null.
- } else if (FreeInst *F = dyn_cast<FreeInst>(*UI)) {
- Writers.push_back(F->getParent()->getParent());
} else {
return true;
}
// 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 (Value::use_iterator I = GV->use_begin(), E = GV->use_end(); I != E; ++I){
} else if (StoreInst *SI = dyn_cast<StoreInst>(*I)) {
// 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));
+ Value *Ptr = SI->getOperand(0)->getUnderlyingObject();
- if (isa<MallocInst>(Ptr)) {
+ if (isMalloc(Ptr)) {
// Okay, easy case.
} else if (CallInst *CI = dyn_cast<CallInst>(Ptr)) {
Function *F = CI->getCalledFunction();
} else {
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.
std::vector<Function*> ReadersWriters;
return false;
}
}
-
+
// Okay, this is an indirect global. Remember all of the allocations for
// this global in AllocsForIndirectGlobals.
while (!AllocRelatedValues.empty()) {
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), E = scc_end(&CG); I!=E; ++I)
- if ((*I).size() != 1) {
- AnalyzeSCC(*I);
- } else if (Function *F = (*I)[0]->getFunction()) {
- if (!F->isDeclaration()) {
- // Nonexternal function.
- AnalyzeSCC(*I);
- } else {
- // Otherwise external function. Handle intrinsics and other special
- // cases here.
- if (getAnalysis<AliasAnalysis>().doesNotAccessMemory(F))
- // If it does not access memory, process the function, causing us to
- // realize it doesn't do anything (the body is empty).
- AnalyzeSCC(*I);
- else {
- // Otherwise, don't process it. This will cause us to conservatively
- // assume the worst.
- }
- }
- } else {
- // Do not process the external node, assume the worst.
+ for (scc_iterator<CallGraph*> I = scc_begin(&CG), E = scc_end(&CG); I != E;
+ ++I) {
+ 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 (unsigned i = 0, e = SCC.size(); i != e; ++i)
+ FunctionInfo.erase(SCC[i]->getFunction());
+ continue;
}
-}
-void GlobalsModRef::AnalyzeSCC(std::vector<CallGraphNode *> &SCC) {
- assert(!SCC.empty() && "SCC with no functions?");
- FunctionRecord &FR = FunctionInfo[SCC[0]->getFunction()];
-
- bool CallsExternal = 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 && !CallsExternal; ++i)
- for (CallGraphNode::iterator CI = SCC[i]->begin(), E = SCC[i]->end();
- CI != E; ++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 (std::map<GlobalValue*, unsigned>::iterator GI =
- CalleeFR->GlobalInfo.begin(), E = CalleeFR->GlobalInfo.end();
- GI != E; ++GI)
- FR.GlobalInfo[GI->first] |= GI->second;
+ 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 |= 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 {
- // Okay, if we can't say anything about it, maybe some other alias
- // analysis can.
- ModRefBehavior MRB =
- AliasAnalysis::getModRefBehavior(Callee);
- if (MRB != DoesNotAccessMemory) {
- // FIXME: could make this more aggressive for functions that just
- // read memory. We should just say they read all globals.
- CallsExternal = true;
- break;
- }
+ FunctionEffect |= 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();
}
- } else {
- CallsExternal = true;
- break;
+ continue;
}
- // If this SCC calls an external function, we can't say anything about it, so
- // remove all SCC functions from the FunctionInfo map.
- if (CallsExternal) {
- for (unsigned i = 0, e = SCC.size(); i != e; ++i)
- FunctionInfo.erase(SCC[i]->getFunction());
- return;
- }
+ 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 (std::map<GlobalValue*, unsigned>::iterator GI =
+ CalleeFR->GlobalInfo.begin(), E = CalleeFR->GlobalInfo.end();
+ GI != E; ++GI)
+ FR.GlobalInfo[GI->first] |= GI->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;
+ }
+ }
- // Otherwise, unless we already know that this function mod/refs memory, scan
- // the function bodies to see if there are any explicit loads or stores.
- if (FunctionEffect != ModRef) {
+ // If we can't say anything useful about this SCC, remove all SCC functions
+ // from the FunctionInfo map.
+ if (KnowNothing) {
+ for (unsigned i = 0, e = SCC.size(); i != e; ++i)
+ FunctionInfo.erase(SCC[i]->getFunction());
+ continue;
+ }
+
+ // Scan the function bodies for explicit loads or stores.
for (unsigned i = 0, e = SCC.size(); i != e && FunctionEffect != ModRef;++i)
for (inst_iterator II = inst_begin(SCC[i]->getFunction()),
E = inst_end(SCC[i]->getFunction());
II != E && FunctionEffect != ModRef; ++II)
- if (isa<LoadInst>(*II))
+ if (isa<LoadInst>(*II)) {
FunctionEffect |= Ref;
- else if (isa<StoreInst>(*II))
+ if (cast<LoadInst>(*II).isVolatile())
+ // Volatile loads may have side-effects, so mark them as writing
+ // memory (for example, a flag inside the processor).
+ FunctionEffect |= Mod;
+ } else if (isa<StoreInst>(*II)) {
FunctionEffect |= Mod;
- else if (isa<MallocInst>(*II) || isa<FreeInst>(*II))
+ if (cast<StoreInst>(*II).isVolatile())
+ // Treat volatile stores as reading memory somewhere.
+ FunctionEffect |= Ref;
+ } else if (isMalloc(&cast<Instruction>(*II)) ||
+ isFreeCall(&cast<Instruction>(*II))) {
FunctionEffect |= ModRef;
- }
+ }
- if ((FunctionEffect & Mod) == 0)
- ++NumReadMemFunctions;
- if (FunctionEffect == 0)
- ++NumNoMemFunctions;
- FR.FunctionEffect = FunctionEffect;
+ if ((FunctionEffect & 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;
+ // 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;
+ }
}
GlobalsModRef::alias(const Value *V1, unsigned V1Size,
const Value *V2, unsigned V2Size) {
// Get the base object these pointers point to.
- Value *UV1 = getUnderlyingObject(const_cast<Value*>(V1));
- Value *UV2 = getUnderlyingObject(const_cast<Value*>(V2));
-
+ Value *UV1 = const_cast<Value*>(V1->getUnderlyingObject());
+ Value *UV2 = const_cast<Value*>(V2->getUnderlyingObject());
+
// If either of the underlying values is a global, they may be non-addr-taken
// globals, which we can answer queries about.
GlobalValue *GV1 = dyn_cast<GlobalValue>(UV1);
if (GV1 && !NonAddressTakenGlobals.count(GV1)) GV1 = 0;
if (GV2 && !NonAddressTakenGlobals.count(GV2)) GV2 = 0;
- // If the the two pointers are derived from two different non-addr-taken
+ // If the two pointers are derived from two different non-addr-taken
// globals, or if one is and the other isn't, we know these can't alias.
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.
if (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 (AllocsForIndirectGlobals.count(UV1))
GV1 = AllocsForIndirectGlobals[UV1];
if (AllocsForIndirectGlobals.count(UV2))
GV2 = AllocsForIndirectGlobals[UV2];
-
+
// Now that we know whether the two pointers are related to indirect globals,
// use this to disambiguate the pointers. If either pointer is based on an
// indirect global and if they are not both based on the same indirect global,
// they cannot alias.
if ((GV1 || GV2) && GV1 != GV2)
return NoAlias;
-
+
return AliasAnalysis::alias(V1, V1Size, V2, V2Size);
}
// 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.
- if (GlobalValue *GV = dyn_cast<GlobalValue>(getUnderlyingObject(P)))
- if (GV->hasInternalLinkage())
+ if (GlobalValue *GV = dyn_cast<GlobalValue>(P->getUnderlyingObject()))
+ if (GV->hasLocalLinkage())
if (Function *F = CS.getCalledFunction())
if (NonAddressTakenGlobals.count(GV))
if (FunctionRecord *FR = getFunctionInfo(F))
}
}
}
-
+
// Otherwise, if this is an allocation related to an indirect global, remove
// it.
AllocsForIndirectGlobals.erase(V);
-
+
AliasAnalysis::deleteValue(V);
}
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