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llvm-mirror/lib/Analysis/AliasSetTracker.cpp
Hal Finkel 9be4aefa57 AA metadata refactoring (introduce AAMDNodes) 
In order to enable the preservation of noalias function parameter information
after inlining, and the representation of block-level __restrict__ pointer
information (etc.), additional kinds of aliasing metadata will be introduced.
This metadata needs to be carried around in AliasAnalysis::Location objects
(and MMOs at the SDAG level), and so we need to generalize the current scheme
(which is hard-coded to just one TBAA MDNode*).

This commit introduces only the necessary refactoring to allow for the
introduction of other aliasing metadata types, but does not actually introduce
any (that will come in a follow-up commit). What it does introduce is a new
AAMDNodes structure to hold all of the aliasing metadata nodes associated with
a particular memory-accessing instruction, and uses that structure instead of
the raw MDNode* in AliasAnalysis::Location, etc.

No functionality change intended.

llvm-svn: 213859
2014-07-24 12:16:19 +00:00

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//===- AliasSetTracker.cpp - Alias Sets Tracker implementation-------------===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This file implements the AliasSetTracker and AliasSet classes.
//
//===----------------------------------------------------------------------===//
#include "llvm/Analysis/AliasSetTracker.h"
#include "llvm/Analysis/AliasAnalysis.h"
#include "llvm/IR/DataLayout.h"
#include "llvm/IR/InstIterator.h"
#include "llvm/IR/Instructions.h"
#include "llvm/IR/IntrinsicInst.h"
#include "llvm/IR/LLVMContext.h"
#include "llvm/IR/Type.h"
#include "llvm/Pass.h"
#include "llvm/Support/Debug.h"
#include "llvm/Support/ErrorHandling.h"
#include "llvm/Support/raw_ostream.h"
using namespace llvm;
/// mergeSetIn - Merge the specified alias set into this alias set.
///
void AliasSet::mergeSetIn(AliasSet &AS, AliasSetTracker &AST) {
assert(!AS.Forward && "Alias set is already forwarding!");
assert(!Forward && "This set is a forwarding set!!");
// Update the alias and access types of this set...
AccessTy |= AS.AccessTy;
AliasTy |= AS.AliasTy;
Volatile |= AS.Volatile;
if (AliasTy == MustAlias) {
// Check that these two merged sets really are must aliases. Since both
// used to be must-alias sets, we can just check any pointer from each set
// for aliasing.
AliasAnalysis &AA = AST.getAliasAnalysis();
PointerRec *L = getSomePointer();
PointerRec *R = AS.getSomePointer();
// If the pointers are not a must-alias pair, this set becomes a may alias.
if (AA.alias(AliasAnalysis::Location(L->getValue(),
L->getSize(),
L->getAAInfo()),
AliasAnalysis::Location(R->getValue(),
R->getSize(),
R->getAAInfo()))
!= AliasAnalysis::MustAlias)
AliasTy = MayAlias;
}
if (UnknownInsts.empty()) { // Merge call sites...
if (!AS.UnknownInsts.empty())
std::swap(UnknownInsts, AS.UnknownInsts);
} else if (!AS.UnknownInsts.empty()) {
UnknownInsts.insert(UnknownInsts.end(), AS.UnknownInsts.begin(), AS.UnknownInsts.end());
AS.UnknownInsts.clear();
}
AS.Forward = this; // Forward across AS now...
addRef(); // AS is now pointing to us...
// Merge the list of constituent pointers...
if (AS.PtrList) {
*PtrListEnd = AS.PtrList;
AS.PtrList->setPrevInList(PtrListEnd);
PtrListEnd = AS.PtrListEnd;
AS.PtrList = nullptr;
AS.PtrListEnd = &AS.PtrList;
assert(*AS.PtrListEnd == nullptr && "End of list is not null?");
}
}
void AliasSetTracker::removeAliasSet(AliasSet *AS) {
if (AliasSet *Fwd = AS->Forward) {
Fwd->dropRef(*this);
AS->Forward = nullptr;
}
AliasSets.erase(AS);
}
void AliasSet::removeFromTracker(AliasSetTracker &AST) {
assert(RefCount == 0 && "Cannot remove non-dead alias set from tracker!");
AST.removeAliasSet(this);
}
void AliasSet::addPointer(AliasSetTracker &AST, PointerRec &Entry,
uint64_t Size, const AAMDNodes &AAInfo,
bool KnownMustAlias) {
assert(!Entry.hasAliasSet() && "Entry already in set!");
// Check to see if we have to downgrade to _may_ alias.
if (isMustAlias() && !KnownMustAlias)
if (PointerRec *P = getSomePointer()) {
AliasAnalysis &AA = AST.getAliasAnalysis();
AliasAnalysis::AliasResult Result =
AA.alias(AliasAnalysis::Location(P->getValue(), P->getSize(),
P->getAAInfo()),
AliasAnalysis::Location(Entry.getValue(), Size, AAInfo));
if (Result != AliasAnalysis::MustAlias)
AliasTy = MayAlias;
else // First entry of must alias must have maximum size!
P->updateSizeAndAAInfo(Size, AAInfo);
assert(Result != AliasAnalysis::NoAlias && "Cannot be part of must set!");
}
Entry.setAliasSet(this);
Entry.updateSizeAndAAInfo(Size, AAInfo);
// Add it to the end of the list...
assert(*PtrListEnd == nullptr && "End of list is not null?");
*PtrListEnd = &Entry;
PtrListEnd = Entry.setPrevInList(PtrListEnd);
assert(*PtrListEnd == nullptr && "End of list is not null?");
addRef(); // Entry points to alias set.
}
void AliasSet::addUnknownInst(Instruction *I, AliasAnalysis &AA) {
UnknownInsts.push_back(I);
if (!I->mayWriteToMemory()) {
AliasTy = MayAlias;
AccessTy |= Refs;
return;
}
// FIXME: This should use mod/ref information to make this not suck so bad
AliasTy = MayAlias;
AccessTy = ModRef;
}
/// aliasesPointer - Return true if the specified pointer "may" (or must)
/// alias one of the members in the set.
///
bool AliasSet::aliasesPointer(const Value *Ptr, uint64_t Size,
const AAMDNodes &AAInfo,
AliasAnalysis &AA) const {
if (AliasTy == MustAlias) {
assert(UnknownInsts.empty() && "Illegal must alias set!");
// If this is a set of MustAliases, only check to see if the pointer aliases
// SOME value in the set.
PointerRec *SomePtr = getSomePointer();
assert(SomePtr && "Empty must-alias set??");
return AA.alias(AliasAnalysis::Location(SomePtr->getValue(),
SomePtr->getSize(),
SomePtr->getAAInfo()),
AliasAnalysis::Location(Ptr, Size, AAInfo));
}
// If this is a may-alias set, we have to check all of the pointers in the set
// to be sure it doesn't alias the set...
for (iterator I = begin(), E = end(); I != E; ++I)
if (AA.alias(AliasAnalysis::Location(Ptr, Size, AAInfo),
AliasAnalysis::Location(I.getPointer(), I.getSize(),
I.getAAInfo())))
return true;
// Check the unknown instructions...
if (!UnknownInsts.empty()) {
for (unsigned i = 0, e = UnknownInsts.size(); i != e; ++i)
if (AA.getModRefInfo(UnknownInsts[i],
AliasAnalysis::Location(Ptr, Size, AAInfo)) !=
AliasAnalysis::NoModRef)
return true;
}
return false;
}
bool AliasSet::aliasesUnknownInst(Instruction *Inst, AliasAnalysis &AA) const {
if (!Inst->mayReadOrWriteMemory())
return false;
for (unsigned i = 0, e = UnknownInsts.size(); i != e; ++i) {
CallSite C1 = getUnknownInst(i), C2 = Inst;
if (!C1 || !C2 ||
AA.getModRefInfo(C1, C2) != AliasAnalysis::NoModRef ||
AA.getModRefInfo(C2, C1) != AliasAnalysis::NoModRef)
return true;
}
for (iterator I = begin(), E = end(); I != E; ++I)
if (AA.getModRefInfo(Inst, AliasAnalysis::Location(I.getPointer(),
I.getSize(),
I.getAAInfo())) !=
AliasAnalysis::NoModRef)
return true;
return false;
}
void AliasSetTracker::clear() {
// Delete all the PointerRec entries.
for (PointerMapType::iterator I = PointerMap.begin(), E = PointerMap.end();
I != E; ++I)
I->second->eraseFromList();
PointerMap.clear();
// The alias sets should all be clear now.
AliasSets.clear();
}
/// findAliasSetForPointer - Given a pointer, find the one alias set to put the
/// instruction referring to the pointer into. If there are multiple alias sets
/// that may alias the pointer, merge them together and return the unified set.
///
AliasSet *AliasSetTracker::findAliasSetForPointer(const Value *Ptr,
uint64_t Size,
const AAMDNodes &AAInfo) {
AliasSet *FoundSet = nullptr;
for (iterator I = begin(), E = end(); I != E; ++I) {
if (I->Forward || !I->aliasesPointer(Ptr, Size, AAInfo, AA)) continue;
if (!FoundSet) { // If this is the first alias set ptr can go into.
FoundSet = I; // Remember it.
} else { // Otherwise, we must merge the sets.
FoundSet->mergeSetIn(*I, *this); // Merge in contents.
}
}
return FoundSet;
}
/// containsPointer - Return true if the specified location is represented by
/// this alias set, false otherwise. This does not modify the AST object or
/// alias sets.
bool AliasSetTracker::containsPointer(Value *Ptr, uint64_t Size,
const AAMDNodes &AAInfo) const {
for (const_iterator I = begin(), E = end(); I != E; ++I)
if (!I->Forward && I->aliasesPointer(Ptr, Size, AAInfo, AA))
return true;
return false;
}
AliasSet *AliasSetTracker::findAliasSetForUnknownInst(Instruction *Inst) {
AliasSet *FoundSet = nullptr;
for (iterator I = begin(), E = end(); I != E; ++I) {
if (I->Forward || !I->aliasesUnknownInst(Inst, AA))
continue;
if (!FoundSet) // If this is the first alias set ptr can go into.
FoundSet = I; // Remember it.
else if (!I->Forward) // Otherwise, we must merge the sets.
FoundSet->mergeSetIn(*I, *this); // Merge in contents.
}
return FoundSet;
}
/// getAliasSetForPointer - Return the alias set that the specified pointer
/// lives in.
AliasSet &AliasSetTracker::getAliasSetForPointer(Value *Pointer, uint64_t Size,
const AAMDNodes &AAInfo,
bool *New) {
AliasSet::PointerRec &Entry = getEntryFor(Pointer);
// Check to see if the pointer is already known.
if (Entry.hasAliasSet()) {
Entry.updateSizeAndAAInfo(Size, AAInfo);
// Return the set!
return *Entry.getAliasSet(*this)->getForwardedTarget(*this);
}
if (AliasSet *AS = findAliasSetForPointer(Pointer, Size, AAInfo)) {
// Add it to the alias set it aliases.
AS->addPointer(*this, Entry, Size, AAInfo);
return *AS;
}
if (New) *New = true;
// Otherwise create a new alias set to hold the loaded pointer.
AliasSets.push_back(new AliasSet());
AliasSets.back().addPointer(*this, Entry, Size, AAInfo);
return AliasSets.back();
}
bool AliasSetTracker::add(Value *Ptr, uint64_t Size, const AAMDNodes &AAInfo) {
bool NewPtr;
addPointer(Ptr, Size, AAInfo, AliasSet::NoModRef, NewPtr);
return NewPtr;
}
bool AliasSetTracker::add(LoadInst *LI) {
if (LI->getOrdering() > Monotonic) return addUnknown(LI);
AAMDNodes AAInfo;
LI->getAAMetadata(AAInfo);
AliasSet::AccessType ATy = AliasSet::Refs;
bool NewPtr;
AliasSet &AS = addPointer(LI->getOperand(0),
AA.getTypeStoreSize(LI->getType()),
AAInfo, ATy, NewPtr);
if (LI->isVolatile()) AS.setVolatile();
return NewPtr;
}
bool AliasSetTracker::add(StoreInst *SI) {
if (SI->getOrdering() > Monotonic) return addUnknown(SI);
AAMDNodes AAInfo;
SI->getAAMetadata(AAInfo);
AliasSet::AccessType ATy = AliasSet::Mods;
bool NewPtr;
Value *Val = SI->getOperand(0);
AliasSet &AS = addPointer(SI->getOperand(1),
AA.getTypeStoreSize(Val->getType()),
AAInfo, ATy, NewPtr);
if (SI->isVolatile()) AS.setVolatile();
return NewPtr;
}
bool AliasSetTracker::add(VAArgInst *VAAI) {
AAMDNodes AAInfo;
VAAI->getAAMetadata(AAInfo);
bool NewPtr;
addPointer(VAAI->getOperand(0), AliasAnalysis::UnknownSize,
AAInfo, AliasSet::ModRef, NewPtr);
return NewPtr;
}
bool AliasSetTracker::addUnknown(Instruction *Inst) {
if (isa<DbgInfoIntrinsic>(Inst))
return true; // Ignore DbgInfo Intrinsics.
if (!Inst->mayReadOrWriteMemory())
return true; // doesn't alias anything
AliasSet *AS = findAliasSetForUnknownInst(Inst);
if (AS) {
AS->addUnknownInst(Inst, AA);
return false;
}
AliasSets.push_back(new AliasSet());
AS = &AliasSets.back();
AS->addUnknownInst(Inst, AA);
return true;
}
bool AliasSetTracker::add(Instruction *I) {
// Dispatch to one of the other add methods.
if (LoadInst *LI = dyn_cast<LoadInst>(I))
return add(LI);
if (StoreInst *SI = dyn_cast<StoreInst>(I))
return add(SI);
if (VAArgInst *VAAI = dyn_cast<VAArgInst>(I))
return add(VAAI);
return addUnknown(I);
}
void AliasSetTracker::add(BasicBlock &BB) {
for (BasicBlock::iterator I = BB.begin(), E = BB.end(); I != E; ++I)
add(I);
}
void AliasSetTracker::add(const AliasSetTracker &AST) {
assert(&AA == &AST.AA &&
"Merging AliasSetTracker objects with different Alias Analyses!");
// Loop over all of the alias sets in AST, adding the pointers contained
// therein into the current alias sets. This can cause alias sets to be
// merged together in the current AST.
for (const_iterator I = AST.begin(), E = AST.end(); I != E; ++I) {
if (I->Forward) continue; // Ignore forwarding alias sets
AliasSet &AS = const_cast<AliasSet&>(*I);
// If there are any call sites in the alias set, add them to this AST.
for (unsigned i = 0, e = AS.UnknownInsts.size(); i != e; ++i)
add(AS.UnknownInsts[i]);
// Loop over all of the pointers in this alias set.
bool X;
for (AliasSet::iterator ASI = AS.begin(), E = AS.end(); ASI != E; ++ASI) {
AliasSet &NewAS = addPointer(ASI.getPointer(), ASI.getSize(),
ASI.getAAInfo(),
(AliasSet::AccessType)AS.AccessTy, X);
if (AS.isVolatile()) NewAS.setVolatile();
}
}
}
/// remove - Remove the specified (potentially non-empty) alias set from the
/// tracker.
void AliasSetTracker::remove(AliasSet &AS) {
// Drop all call sites.
AS.UnknownInsts.clear();
// Clear the alias set.
unsigned NumRefs = 0;
while (!AS.empty()) {
AliasSet::PointerRec *P = AS.PtrList;
Value *ValToRemove = P->getValue();
// Unlink and delete entry from the list of values.
P->eraseFromList();
// Remember how many references need to be dropped.
++NumRefs;
// Finally, remove the entry.
PointerMap.erase(ValToRemove);
}
// Stop using the alias set, removing it.
AS.RefCount -= NumRefs;
if (AS.RefCount == 0)
AS.removeFromTracker(*this);
}
bool
AliasSetTracker::remove(Value *Ptr, uint64_t Size, const AAMDNodes &AAInfo) {
AliasSet *AS = findAliasSetForPointer(Ptr, Size, AAInfo);
if (!AS) return false;
remove(*AS);
return true;
}
bool AliasSetTracker::remove(LoadInst *LI) {
uint64_t Size = AA.getTypeStoreSize(LI->getType());
AAMDNodes AAInfo;
LI->getAAMetadata(AAInfo);
AliasSet *AS = findAliasSetForPointer(LI->getOperand(0), Size, AAInfo);
if (!AS) return false;
remove(*AS);
return true;
}
bool AliasSetTracker::remove(StoreInst *SI) {
uint64_t Size = AA.getTypeStoreSize(SI->getOperand(0)->getType());
AAMDNodes AAInfo;
SI->getAAMetadata(AAInfo);
AliasSet *AS = findAliasSetForPointer(SI->getOperand(1), Size, AAInfo);
if (!AS) return false;
remove(*AS);
return true;
}
bool AliasSetTracker::remove(VAArgInst *VAAI) {
AAMDNodes AAInfo;
VAAI->getAAMetadata(AAInfo);
AliasSet *AS = findAliasSetForPointer(VAAI->getOperand(0),
AliasAnalysis::UnknownSize, AAInfo);
if (!AS) return false;
remove(*AS);
return true;
}
bool AliasSetTracker::removeUnknown(Instruction *I) {
if (!I->mayReadOrWriteMemory())
return false; // doesn't alias anything
AliasSet *AS = findAliasSetForUnknownInst(I);
if (!AS) return false;
remove(*AS);
return true;
}
bool AliasSetTracker::remove(Instruction *I) {
// Dispatch to one of the other remove methods...
if (LoadInst *LI = dyn_cast<LoadInst>(I))
return remove(LI);
if (StoreInst *SI = dyn_cast<StoreInst>(I))
return remove(SI);
if (VAArgInst *VAAI = dyn_cast<VAArgInst>(I))
return remove(VAAI);
return removeUnknown(I);
}
// deleteValue method - This method is used to remove a pointer value from the
// AliasSetTracker entirely. It should be used when an instruction is deleted
// from the program to update the AST. If you don't use this, you would have
// dangling pointers to deleted instructions.
//
void AliasSetTracker::deleteValue(Value *PtrVal) {
// Notify the alias analysis implementation that this value is gone.
AA.deleteValue(PtrVal);
// If this is a call instruction, remove the callsite from the appropriate
// AliasSet (if present).
if (Instruction *Inst = dyn_cast<Instruction>(PtrVal)) {
if (Inst->mayReadOrWriteMemory()) {
// Scan all the alias sets to see if this call site is contained.
for (iterator I = begin(), E = end(); I != E; ++I) {
if (I->Forward) continue;
I->removeUnknownInst(Inst);
}
}
}
// First, look up the PointerRec for this pointer.
PointerMapType::iterator I = PointerMap.find_as(PtrVal);
if (I == PointerMap.end()) return; // Noop
// If we found one, remove the pointer from the alias set it is in.
AliasSet::PointerRec *PtrValEnt = I->second;
AliasSet *AS = PtrValEnt->getAliasSet(*this);
// Unlink and delete from the list of values.
PtrValEnt->eraseFromList();
// Stop using the alias set.
AS->dropRef(*this);
PointerMap.erase(I);
}
// copyValue - This method should be used whenever a preexisting value in the
// program is copied or cloned, introducing a new value. Note that it is ok for
// clients that use this method to introduce the same value multiple times: if
// the tracker already knows about a value, it will ignore the request.
//
void AliasSetTracker::copyValue(Value *From, Value *To) {
// Notify the alias analysis implementation that this value is copied.
AA.copyValue(From, To);
// First, look up the PointerRec for this pointer.
PointerMapType::iterator I = PointerMap.find_as(From);
if (I == PointerMap.end())
return; // Noop
assert(I->second->hasAliasSet() && "Dead entry?");
AliasSet::PointerRec &Entry = getEntryFor(To);
if (Entry.hasAliasSet()) return; // Already in the tracker!
// Add it to the alias set it aliases...
I = PointerMap.find_as(From);
AliasSet *AS = I->second->getAliasSet(*this);
AS->addPointer(*this, Entry, I->second->getSize(),
I->second->getAAInfo(),
true);
}
//===----------------------------------------------------------------------===//
// AliasSet/AliasSetTracker Printing Support
//===----------------------------------------------------------------------===//
void AliasSet::print(raw_ostream &OS) const {
OS << " AliasSet[" << (const void*)this << ", " << RefCount << "] ";
OS << (AliasTy == MustAlias ? "must" : "may") << " alias, ";
switch (AccessTy) {
case NoModRef: OS << "No access "; break;
case Refs : OS << "Ref "; break;
case Mods : OS << "Mod "; break;
case ModRef : OS << "Mod/Ref "; break;
default: llvm_unreachable("Bad value for AccessTy!");
}
if (isVolatile()) OS << "[volatile] ";
if (Forward)
OS << " forwarding to " << (void*)Forward;
if (!empty()) {
OS << "Pointers: ";
for (iterator I = begin(), E = end(); I != E; ++I) {
if (I != begin()) OS << ", ";
I.getPointer()->printAsOperand(OS << "(");
OS << ", " << I.getSize() << ")";
}
}
if (!UnknownInsts.empty()) {
OS << "\n " << UnknownInsts.size() << " Unknown instructions: ";
for (unsigned i = 0, e = UnknownInsts.size(); i != e; ++i) {
if (i) OS << ", ";
UnknownInsts[i]->printAsOperand(OS);
}
}
OS << "\n";
}
void AliasSetTracker::print(raw_ostream &OS) const {
OS << "Alias Set Tracker: " << AliasSets.size() << " alias sets for "
<< PointerMap.size() << " pointer values.\n";
for (const_iterator I = begin(), E = end(); I != E; ++I)
I->print(OS);
OS << "\n";
}
#if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
void AliasSet::dump() const { print(dbgs()); }
void AliasSetTracker::dump() const { print(dbgs()); }
#endif
//===----------------------------------------------------------------------===//
// ASTCallbackVH Class Implementation
//===----------------------------------------------------------------------===//
void AliasSetTracker::ASTCallbackVH::deleted() {
assert(AST && "ASTCallbackVH called with a null AliasSetTracker!");
AST->deleteValue(getValPtr());
// this now dangles!
}
void AliasSetTracker::ASTCallbackVH::allUsesReplacedWith(Value *V) {
AST->copyValue(getValPtr(), V);
}
AliasSetTracker::ASTCallbackVH::ASTCallbackVH(Value *V, AliasSetTracker *ast)
: CallbackVH(V), AST(ast) {}
AliasSetTracker::ASTCallbackVH &
AliasSetTracker::ASTCallbackVH::operator=(Value *V) {
return *this = ASTCallbackVH(V, AST);
}
//===----------------------------------------------------------------------===//
// AliasSetPrinter Pass
//===----------------------------------------------------------------------===//
namespace {
class AliasSetPrinter : public FunctionPass {
AliasSetTracker *Tracker;
public:
static char ID; // Pass identification, replacement for typeid
AliasSetPrinter() : FunctionPass(ID) {
initializeAliasSetPrinterPass(*PassRegistry::getPassRegistry());
}
void getAnalysisUsage(AnalysisUsage &AU) const override {
AU.setPreservesAll();
AU.addRequired<AliasAnalysis>();
}
bool runOnFunction(Function &F) override {
Tracker = new AliasSetTracker(getAnalysis<AliasAnalysis>());
for (inst_iterator I = inst_begin(F), E = inst_end(F); I != E; ++I)
Tracker->add(&*I);
Tracker->print(errs());
delete Tracker;
return false;
}
};
}
char AliasSetPrinter::ID = 0;
INITIALIZE_PASS_BEGIN(AliasSetPrinter, "print-alias-sets",
"Alias Set Printer", false, true)
INITIALIZE_AG_DEPENDENCY(AliasAnalysis)
INITIALIZE_PASS_END(AliasSetPrinter, "print-alias-sets",
"Alias Set Printer", false, true)
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