//===- GlobalsModRef.cpp - Simple Mod/Ref Analysis for Globals ------------===//
-//
+//
// 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.
+//
//===----------------------------------------------------------------------===//
//
// This simple pass provides alias and mod/ref information for global values
-// that do not have their address taken. For this simple (but very common)
-// case, we can provide pretty accurate and useful information.
+// 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.
//
//===----------------------------------------------------------------------===//
-#define DEBUG_TYPE "globalsmodref"
+#define DEBUG_TYPE "globalsmodref-aa"
#include "llvm/Analysis/Passes.h"
#include "llvm/Module.h"
#include "llvm/Pass.h"
#include "llvm/Instructions.h"
#include "llvm/Constants.h"
+#include "llvm/DerivedTypes.h"
#include "llvm/Analysis/AliasAnalysis.h"
#include "llvm/Analysis/CallGraph.h"
-#include "Support/Debug.h"
-#include "Support/Statistic.h"
-#include "Support/SCCIterator.h"
+#include "llvm/Support/Compiler.h"
+#include "llvm/Support/CommandLine.h"
+#include "llvm/Support/InstIterator.h"
+#include "llvm/ADT/Statistic.h"
+#include "llvm/ADT/SCCIterator.h"
#include <set>
using namespace llvm;
+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");
+
namespace {
- Statistic<>
- NumNonAddrTakenGlobalVars("globalsmodref-aa",
- "Number of global vars without address taken");
- Statistic<>
- NumNonAddrTakenFunctions("globalsmodref-aa",
- "Number of functions without address taken");
-
- class GlobalsModRef : public Pass, public AliasAnalysis {
- /// ModRefFns - One instance of this record is kept for each global without
- /// its address taken.
- struct ModRefFns {
- /// RefFns/ModFns - Sets of functions that and write globals.
- std::set<Function*> RefFns, ModFns;
- };
-
- /// NonAddressTakenGlobals - A map of globals that do not have their
- /// addresses taken to their record.
- std::map<GlobalValue*, ModRefFns> NonAddressTakenGlobals;
+ /// 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 VISIBILITY_HIDDEN 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;
+
+ unsigned getInfoForGlobal(GlobalValue *GV) const {
+ std::map<GlobalValue*, unsigned>::const_iterator I = GlobalInfo.find(GV);
+ if (I != GlobalInfo.end())
+ return I->second;
+ return 0;
+ }
+
+ /// 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) {}
+ };
+ /// GlobalsModRef - The actual analysis pass.
+ class VISIBILITY_HIDDEN 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<std::pair<Function*, GlobalValue*>, unsigned> FunctionInfo;
+ std::map<Function*, FunctionRecord> FunctionInfo;
public:
- bool run(Module &M) {
+ static char ID;
+ GlobalsModRef() : ModulePass((intptr_t)&ID) {}
+
+ bool runOnModule(Module &M) {
InitializeAliasAnalysis(this); // set up super class
AnalyzeGlobals(M); // find non-addr taken globals
AnalyzeCallGraph(getAnalysis<CallGraph>(), M); // Propagate on CG
//------------------------------------------------
// Implement the AliasAnalysis API
- //
+ //
AliasResult alias(const Value *V1, unsigned V1Size,
const Value *V2, unsigned V2Size);
ModRefResult getModRefInfo(CallSite CS, Value *P, unsigned Size);
+ 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,
+ std::vector<PointerAccessInfo> *Info) {
+ 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);
+ }
+
virtual void deleteValue(Value *V);
virtual void copyValue(Value *From, Value *To);
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).
+ FunctionRecord *getFunctionInfo(Function *F) {
+ std::map<Function*, FunctionRecord>::iterator I = FunctionInfo.find(F);
+ if (I != FunctionInfo.end())
+ return &I->second;
+ return 0;
+ }
+
void AnalyzeGlobals(Module &M);
void AnalyzeCallGraph(CallGraph &CG, Module &M);
- bool AnalyzeUsesOfGlobal(Value *V, std::vector<Function*> &Readers,
- std::vector<Function*> &Writers);
+ 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);
};
-
- RegisterOpt<GlobalsModRef> X("globalsmodref-aa",
- "Simple mod/ref analysis for globals");
- RegisterAnalysisGroup<AliasAnalysis, GlobalsModRef> Y;
+
+ 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(); }
+/// 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;
+}
-/// AnalyzeGlobalUses - Scan through the users of all of the internal
+/// 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.
std::vector<Function*> Readers, Writers;
for (Module::iterator I = M.begin(), E = M.end(); I != E; ++I)
if (I->hasInternalLinkage()) {
- if (!AnalyzeUsesOfGlobal(I, Readers, Writers)) {
- // Remember that we are tracking this global, and the mod/ref fns
- ModRefFns &E = NonAddressTakenGlobals[I];
- E.RefFns.insert(Readers.begin(), Readers.end());
- E.ModFns.insert(Writers.begin(), Writers.end());
+ if (!AnalyzeUsesOfPointer(I, Readers, Writers)) {
+ // Remember that we are tracking this global.
+ NonAddressTakenGlobals.insert(I);
++NumNonAddrTakenFunctions;
}
Readers.clear(); Writers.clear();
}
- for (Module::giterator I = M.gbegin(), E = M.gend(); I != E; ++I)
- // FIXME: it is kinda dumb to track aliasing properties for constant
- // globals, it will never be particularly useful anyways, 'cause they can
- // never be modified (and the optimizer knows this already)!
+ for (Module::global_iterator I = M.global_begin(), E = M.global_end();
+ I != E; ++I)
if (I->hasInternalLinkage()) {
- if (!AnalyzeUsesOfGlobal(I, Readers, Writers)) {
+ if (!AnalyzeUsesOfPointer(I, Readers, Writers)) {
// Remember that we are tracking this global, and the mod/ref fns
- ModRefFns &E = NonAddressTakenGlobals[I];
- E.RefFns.insert(Readers.begin(), Readers.end());
- E.ModFns.insert(Writers.begin(), Writers.end());
+ NonAddressTakenGlobals.insert(I);
+ for (unsigned i = 0, e = Readers.size(); i != e; ++i)
+ FunctionInfo[Readers[i]].GlobalInfo[I] |= Ref;
+
+ if (!I->isConstant()) // No need to keep track of writers to constants
+ 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()) &&
+ AnalyzeIndirectGlobalMemory(I))
+ ++NumIndirectGlobalVars;
}
Readers.clear(); Writers.clear();
}
}
-/// AnalyzeUsesOfGlobal - Look at all of the users of the specified global value
-/// derived 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.
-bool GlobalsModRef::AnalyzeUsesOfGlobal(Value *V,
- std::vector<Function*> &Readers,
- std::vector<Function*> &Writers) {
- //if (!isa<PointerType>(V->getType())) return true;
+/// 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,
+ std::vector<Function*> &Readers,
+ std::vector<Function*> &Writers,
+ GlobalValue *OkayStoreDest) {
+ if (!isa<PointerType>(V->getType())) return true;
for (Value::use_iterator UI = V->use_begin(), E = V->use_end(); UI != E; ++UI)
if (LoadInst *LI = dyn_cast<LoadInst>(*UI)) {
Readers.push_back(LI->getParent()->getParent());
} else if (StoreInst *SI = dyn_cast<StoreInst>(*UI)) {
- if (V == SI->getOperand(0)) return true; // Storing the pointer
- Writers.push_back(SI->getParent()->getParent());
+ if (V == SI->getOperand(1)) {
+ Writers.push_back(SI->getParent()->getParent());
+ } else if (SI->getOperand(1) != OkayStoreDest) {
+ return true; // Storing the pointer
+ }
} else if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(*UI)) {
- if (AnalyzeUsesOfGlobal(GEP, Readers, Writers)) return true;
- } 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 = 1, e = CI->getNumOperands(); i != e; ++i)
- if (CI->getOperand(i) == V) return true;
+ if (AnalyzeUsesOfPointer(GEP, Readers, Writers)) return true;
} 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 ||
- CE->getOpcode() == Instruction::Cast) {
- if (AnalyzeUsesOfGlobal(CE, Readers, Writers))
+ if (CE->getOpcode() == Instruction::GetElementPtr ||
+ CE->getOpcode() == Instruction::BitCast) {
+ if (AnalyzeUsesOfPointer(CE, Readers, Writers))
return true;
} else {
return true;
- }
- } else if (ConstantPointerRef *CPR = dyn_cast<ConstantPointerRef>(*UI)) {
- if (AnalyzeUsesOfGlobal(CPR, 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;
}
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 (Value::use_iterator I = GV->use_begin(), E = GV->use_end(); I != E; ++I){
+ if (LoadInst *LI = dyn_cast<LoadInst>(*I)) {
+ // 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.
+ std::vector<Function*> ReadersWriters;
+ if (AnalyzeUsesOfPointer(LI, ReadersWriters, ReadersWriters))
+ return false; // Loaded pointer escapes.
+ // TODO: Could try some IP mod/ref of the loaded pointer.
+ } 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));
+
+ if (isa<MallocInst>(Ptr)) {
+ // Okay, easy case.
+ } else if (CallInst *CI = dyn_cast<CallInst>(Ptr)) {
+ Function *F = CI->getCalledFunction();
+ if (!F || !F->isDeclaration()) return false; // Too hard to analyze.
+ if (F->getName() != "calloc") return false; // Not calloc.
+ } 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;
+ if (AnalyzeUsesOfPointer(Ptr, ReadersWriters, ReadersWriters, 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;
+ AllocRelatedValues.pop_back();
+ }
+ IndirectGlobals.insert(GV);
+ 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.
+/// graph to all callers and compute the mod/ref info for all memory for each
+/// function.
void GlobalsModRef::AnalyzeCallGraph(CallGraph &CG, Module &M) {
- if (NonAddressTakenGlobals.empty()) return; // Don't bother, nothing to do.
-
- // Invert the NonAddressTakenGlobals map into the FunctionInfo map.
- for (std::map<GlobalValue*, ModRefFns>::iterator I =
- NonAddressTakenGlobals.begin(), E = NonAddressTakenGlobals.end();
- I != E; ++I) {
- GlobalValue *GV = I->first;
- ModRefFns &MRInfo = I->second;
- for (std::set<Function*>::iterator I = MRInfo.RefFns.begin(),
- E = MRInfo.RefFns.begin(); I != E; ++I)
- FunctionInfo[std::make_pair(*I, GV)] |= Ref;
- MRInfo.RefFns.clear();
- for (std::set<Function*>::iterator I = MRInfo.ModFns.begin(),
- E = MRInfo.ModFns.begin(); I != E; ++I)
- FunctionInfo[std::make_pair(*I, GV)] |= Mod;
- MRInfo.ModFns.clear();
- }
-
// 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) {
- std::map<GlobalValue*, unsigned> ModRefProperties;
- const std::vector<CallGraphNode *> &SCC = *I;
+ 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.
+ }
+}
+
+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;
- // Collect the mod/ref properties due to called functions.
- for (unsigned i = 0, e = SCC.size(); i != e; ++i)
- for (CallGraphNode::iterator CI = SCC[i]->begin(), E = SCC[i]->end();
- CI != E; ++CI) {
- if (Function *Callee = (*CI)->getFunction()) {
- // Otherwise, combine the callee properties into our accumulated set.
- std::map<std::pair<Function*, GlobalValue*>, unsigned>::iterator
- CI = FunctionInfo.lower_bound(std::make_pair(Callee,
- (GlobalValue*)0));
- for (;CI != FunctionInfo.end() && CI->first.first == Callee; ++CI)
- ModRefProperties[CI->first.second] |= CI->second;
} else {
- // For now assume that external functions could mod/ref anything,
- // since they could call into an escaping function that mod/refs an
- // internal. FIXME: We need better tracking!
- for (std::map<GlobalValue*, ModRefFns>::iterator GI =
- NonAddressTakenGlobals.begin(),
- E = NonAddressTakenGlobals.end(); GI != E; ++GI)
- ModRefProperties[GI->first] = ModRef;
- goto Out;
+ // 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;
+ }
}
+ } else {
+ CallsExternal = true;
+ break;
}
- Out:
- // Set all functions in the CFG to have these properties. FIXME: it would
- // be better to use union find to only store these properties once,
- // PARTICULARLY if it's the universal set.
+
+ // 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)
- if (Function *F = SCC[i]->getFunction()) {
- for (std::map<GlobalValue*, unsigned>::iterator I =
- ModRefProperties.begin(), E = ModRefProperties.end();
- I != E; ++I)
- FunctionInfo[std::make_pair(F, I->first)] = I->second;
- }
+ FunctionInfo.erase(SCC[i]->getFunction());
+ return;
}
-}
+ // 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) {
+ 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))
+ FunctionEffect |= Ref;
+ else if (isa<StoreInst>(*II))
+ FunctionEffect |= Mod;
+ else if (isa<MallocInst>(*II) || isa<FreeInst>(*II))
+ FunctionEffect |= ModRef;
+ }
+ if ((FunctionEffect & Mod) == 0)
+ ++NumReadMemFunctions;
+ if (FunctionEffect == 0)
+ ++NumNoMemFunctions;
+ FR.FunctionEffect = FunctionEffect;
-/// 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 const GlobalValue *getUnderlyingObject(const Value *V) {
- //if (!isa<PointerType>(V->getType())) return 0;
-
- // If we are at some type of object... return it.
- if (const GlobalValue *GV = dyn_cast<GlobalValue>(V)) return GV;
-
- // Traverse through different addressing mechanisms...
- if (const Instruction *I = dyn_cast<Instruction>(V)) {
- if (isa<CastInst>(I) || isa<GetElementPtrInst>(I))
- return getUnderlyingObject(I->getOperand(0));
- } else if (const ConstantExpr *CE = dyn_cast<ConstantExpr>(V)) {
- if (CE->getOpcode() == Instruction::Cast ||
- CE->getOpcode() == Instruction::GetElementPtr)
- return getUnderlyingObject(CE->getOperand(0));
- } else if (const ConstantPointerRef *CPR = dyn_cast<ConstantPointerRef>(V)) {
- return CPR->getValue();
- }
- return 0;
+ // 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.
AliasAnalysis::AliasResult
GlobalsModRef::alias(const Value *V1, unsigned V1Size,
const Value *V2, unsigned V2Size) {
- GlobalValue *GV1 = const_cast<GlobalValue*>(getUnderlyingObject(V1));
- GlobalValue *GV2 = const_cast<GlobalValue*>(getUnderlyingObject(V2));
-
- // 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 = 0;
- if (GV2 && !NonAddressTakenGlobals.count(GV2)) GV2 = 0;
-
+ // Get the base object these pointers point to.
+ Value *UV1 = getUnderlyingObject(const_cast<Value*>(V1));
+ Value *UV2 = getUnderlyingObject(const_cast<Value*>(V2));
+
+ // 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);
+ 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 = 0;
+ if (GV2 && !NonAddressTakenGlobals.count(GV2)) GV2 = 0;
+
+ // If the 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.
+ GV1 = GV2 = 0;
+ if (LoadInst *LI = dyn_cast<LoadInst>(UV1))
+ if (GlobalVariable *GV = dyn_cast<GlobalVariable>(LI->getOperand(0)))
+ if (IndirectGlobals.count(GV))
+ GV1 = GV;
+ if (LoadInst *LI = dyn_cast<LoadInst>(UV2))
+ 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);
}
unsigned Known = ModRef;
// If we are asking for mod/ref info of a direct call with a pointer to a
- // global, return information if we have it.
- if (GlobalValue *GV = const_cast<GlobalValue*>(getUnderlyingObject(P)))
+ // global we are tracking, return information if we have it.
+ if (GlobalValue *GV = dyn_cast<GlobalValue>(getUnderlyingObject(P)))
if (GV->hasInternalLinkage())
- if (Function *F = CS.getCalledFunction()) {
- std::map<std::pair<Function*, GlobalValue*>, unsigned>::iterator
- it = FunctionInfo.find(std::make_pair(F, GV));
- if (it != FunctionInfo.end())
- Known = it->second;
- }
+ if (Function *F = CS.getCalledFunction())
+ if (NonAddressTakenGlobals.count(GV))
+ if (FunctionRecord *FR = getFunctionInfo(F))
+ Known = FR->getInfoForGlobal(GV);
if (Known == NoModRef)
return NoModRef; // No need to query other mod/ref analyses
//
void GlobalsModRef::deleteValue(Value *V) {
if (GlobalValue *GV = dyn_cast<GlobalValue>(V)) {
- std::map<GlobalValue*, ModRefFns>::iterator I =
- NonAddressTakenGlobals.find(GV);
- if (I != NonAddressTakenGlobals.end())
- NonAddressTakenGlobals.erase(I);
+ if (NonAddressTakenGlobals.erase(GV)) {
+ // This global might be an indirect global. If so, remove it and remove
+ // any AllocRelatedValues for it.
+ if (IndirectGlobals.erase(GV)) {
+ // Remove any entries in AllocsForIndirectGlobals for this global.
+ for (std::map<Value*, GlobalValue*>::iterator
+ I = AllocsForIndirectGlobals.begin(),
+ E = AllocsForIndirectGlobals.end(); I != E; ) {
+ if (I->second == GV) {
+ AllocsForIndirectGlobals.erase(I++);
+ } else {
+ ++I;
+ }
+ }
+ }
+ }
}
+
+ // Otherwise, if this is an allocation related to an indirect global, remove
+ // it.
+ AllocsForIndirectGlobals.erase(V);
+
+ AliasAnalysis::deleteValue(V);
}
void GlobalsModRef::copyValue(Value *From, Value *To) {
- if (GlobalValue *FromGV = dyn_cast<GlobalValue>(From))
- if (GlobalValue *ToGV = dyn_cast<GlobalValue>(To)) {
- std::map<GlobalValue*, ModRefFns>::iterator I =
- NonAddressTakenGlobals.find(FromGV);
- if (I != NonAddressTakenGlobals.end())
- NonAddressTakenGlobals[ToGV] = I->second;
- }
+ AliasAnalysis::copyValue(From, To);
}
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