forked from OSchip/llvm-project
Refactor some code. No functionality changes.
llvm-svn: 84000
This commit is contained in:
Evan Cheng
parent
54463e837a
commit
f1f3dd3c3c
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@ -215,6 +215,11 @@ namespace {
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bool pointsToConstantMemory(const Value *P);
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private:
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// aliasGEP - Provide a bunch of ad-hoc rules to disambiguate a GEP instruction
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// against another.
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AliasResult aliasGEP(const Value *V1, unsigned V1Size,
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const Value *V2, unsigned V2Size);
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// CheckGEPInstructions - Check two GEP instructions with known
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// must-aliasing base pointers. This checks to see if the index expressions
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// preclude the pointers from aliasing...
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@ -329,61 +334,12 @@ BasicAliasAnalysis::getModRefInfo(CallSite CS1, CallSite CS2) {
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return NoAA::getModRefInfo(CS1, CS2);
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}
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// alias - Provide a bunch of ad-hoc rules to disambiguate in common cases, such
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// as array references.
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// aliasGEP - Provide a bunch of ad-hoc rules to disambiguate a GEP instruction
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// against another.
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//
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AliasAnalysis::AliasResult
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BasicAliasAnalysis::alias(const Value *V1, unsigned V1Size,
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const Value *V2, unsigned V2Size) {
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// Strip off any casts if they exist.
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V1 = V1->stripPointerCasts();
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V2 = V2->stripPointerCasts();
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// Are we checking for alias of the same value?
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if (V1 == V2) return MustAlias;
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if (!isa<PointerType>(V1->getType()) || !isa<PointerType>(V2->getType()))
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return NoAlias; // Scalars cannot alias each other
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// Figure out what objects these things are pointing to if we can.
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const Value *O1 = V1->getUnderlyingObject();
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const Value *O2 = V2->getUnderlyingObject();
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if (O1 != O2) {
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// If V1/V2 point to two different objects we know that we have no alias.
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if (isIdentifiedObject(O1) && isIdentifiedObject(O2))
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return NoAlias;
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// Arguments can't alias with local allocations or noalias calls.
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if ((isa<Argument>(O1) && (isa<AllocationInst>(O2) || isNoAliasCall(O2))) ||
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(isa<Argument>(O2) && (isa<AllocationInst>(O1) || isNoAliasCall(O1))))
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return NoAlias;
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// Most objects can't alias null.
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if ((isa<ConstantPointerNull>(V2) && isKnownNonNull(O1)) ||
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(isa<ConstantPointerNull>(V1) && isKnownNonNull(O2)))
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return NoAlias;
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}
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// If the size of one access is larger than the entire object on the other
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// side, then we know such behavior is undefined and can assume no alias.
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LLVMContext &Context = V1->getContext();
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if (TD)
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if ((V1Size != ~0U && isObjectSmallerThan(O2, V1Size, Context, *TD)) ||
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(V2Size != ~0U && isObjectSmallerThan(O1, V2Size, Context, *TD)))
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return NoAlias;
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// If one pointer is the result of a call/invoke and the other is a
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// non-escaping local object, then we know the object couldn't escape to a
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// point where the call could return it.
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if ((isa<CallInst>(O1) || isa<InvokeInst>(O1)) &&
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isNonEscapingLocalObject(O2) && O1 != O2)
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return NoAlias;
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if ((isa<CallInst>(O2) || isa<InvokeInst>(O2)) &&
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isNonEscapingLocalObject(O1) && O1 != O2)
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return NoAlias;
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BasicAliasAnalysis::aliasGEP(const Value *V1, unsigned V1Size,
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const Value *V2, unsigned V2Size) {
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// If we have two gep instructions with must-alias'ing base pointers, figure
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// out if the indexes to the GEP tell us anything about the derived pointer.
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// Note that we also handle chains of getelementptr instructions as well as
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@ -451,63 +407,121 @@ BasicAliasAnalysis::alias(const Value *V1, unsigned V1Size,
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// instruction. If one pointer is a GEP with a non-zero index of the other
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// pointer, we know they cannot alias.
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//
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if (isGEP(V2)) {
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if (V1Size == ~0U || V2Size == ~0U)
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return MayAlias;
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SmallVector<Value*, 16> GEPOperands;
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const Value *BasePtr = GetGEPOperands(V1, GEPOperands);
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AliasResult R = alias(BasePtr, V1Size, V2, V2Size);
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if (R == MustAlias) {
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// If there is at least one non-zero constant index, we know they cannot
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// alias.
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bool ConstantFound = false;
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bool AllZerosFound = true;
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for (unsigned i = 0, e = GEPOperands.size(); i != e; ++i)
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if (const Constant *C = dyn_cast<Constant>(GEPOperands[i])) {
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if (!C->isNullValue()) {
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ConstantFound = true;
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AllZerosFound = false;
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break;
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}
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} else {
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AllZerosFound = false;
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}
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// If we have getelementptr <ptr>, 0, 0, 0, 0, ... and V2 must aliases
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// the ptr, the end result is a must alias also.
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if (AllZerosFound)
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return MustAlias;
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if (ConstantFound) {
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if (V2Size <= 1 && V1Size <= 1) // Just pointer check?
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return NoAlias;
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// Otherwise we have to check to see that the distance is more than
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// the size of the argument... build an index vector that is equal to
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// the arguments provided, except substitute 0's for any variable
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// indexes we find...
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if (TD &&
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cast<PointerType>(BasePtr->getType())->getElementType()->isSized()) {
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for (unsigned i = 0; i != GEPOperands.size(); ++i)
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if (!isa<ConstantInt>(GEPOperands[i]))
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GEPOperands[i] = Constant::getNullValue(GEPOperands[i]->getType());
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int64_t Offset =
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TD->getIndexedOffset(BasePtr->getType(),
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&GEPOperands[0],
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GEPOperands.size());
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if (Offset >= (int64_t)V2Size || Offset <= -(int64_t)V1Size)
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return NoAlias;
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}
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}
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}
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return MayAlias;
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}
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// alias - Provide a bunch of ad-hoc rules to disambiguate in common cases, such
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// as array references.
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//
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AliasAnalysis::AliasResult
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BasicAliasAnalysis::alias(const Value *V1, unsigned V1Size,
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const Value *V2, unsigned V2Size) {
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// Strip off any casts if they exist.
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V1 = V1->stripPointerCasts();
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V2 = V2->stripPointerCasts();
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// Are we checking for alias of the same value?
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if (V1 == V2) return MustAlias;
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if (!isa<PointerType>(V1->getType()) || !isa<PointerType>(V2->getType()))
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return NoAlias; // Scalars cannot alias each other
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// Figure out what objects these things are pointing to if we can.
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const Value *O1 = V1->getUnderlyingObject();
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const Value *O2 = V2->getUnderlyingObject();
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if (O1 != O2) {
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// If V1/V2 point to two different objects we know that we have no alias.
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if (isIdentifiedObject(O1) && isIdentifiedObject(O2))
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return NoAlias;
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// Arguments can't alias with local allocations or noalias calls.
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if ((isa<Argument>(O1) && (isa<AllocationInst>(O2) || isNoAliasCall(O2))) ||
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(isa<Argument>(O2) && (isa<AllocationInst>(O1) || isNoAliasCall(O1))))
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return NoAlias;
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// Most objects can't alias null.
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if ((isa<ConstantPointerNull>(V2) && isKnownNonNull(O1)) ||
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(isa<ConstantPointerNull>(V1) && isKnownNonNull(O2)))
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return NoAlias;
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}
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// If the size of one access is larger than the entire object on the other
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// side, then we know such behavior is undefined and can assume no alias.
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LLVMContext &Context = V1->getContext();
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if (TD)
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if ((V1Size != ~0U && isObjectSmallerThan(O2, V1Size, Context, *TD)) ||
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(V2Size != ~0U && isObjectSmallerThan(O1, V2Size, Context, *TD)))
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return NoAlias;
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// If one pointer is the result of a call/invoke and the other is a
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// non-escaping local object, then we know the object couldn't escape to a
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// point where the call could return it.
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if ((isa<CallInst>(O1) || isa<InvokeInst>(O1)) &&
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isNonEscapingLocalObject(O2) && O1 != O2)
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return NoAlias;
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if ((isa<CallInst>(O2) || isa<InvokeInst>(O2)) &&
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isNonEscapingLocalObject(O1) && O1 != O2)
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return NoAlias;
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if (!isGEP(V1) && isGEP(V2)) {
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std::swap(V1, V2);
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std::swap(V1Size, V2Size);
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}
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if (V1Size != ~0U && V2Size != ~0U)
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if (isGEP(V1)) {
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SmallVector<Value*, 16> GEPOperands;
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const Value *BasePtr = GetGEPOperands(V1, GEPOperands);
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AliasResult R = alias(BasePtr, V1Size, V2, V2Size);
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if (R == MustAlias) {
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// If there is at least one non-zero constant index, we know they cannot
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// alias.
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bool ConstantFound = false;
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bool AllZerosFound = true;
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for (unsigned i = 0, e = GEPOperands.size(); i != e; ++i)
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if (const Constant *C = dyn_cast<Constant>(GEPOperands[i])) {
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if (!C->isNullValue()) {
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ConstantFound = true;
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AllZerosFound = false;
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break;
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}
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} else {
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AllZerosFound = false;
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}
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// If we have getelementptr <ptr>, 0, 0, 0, 0, ... and V2 must aliases
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// the ptr, the end result is a must alias also.
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if (AllZerosFound)
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return MustAlias;
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if (ConstantFound) {
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if (V2Size <= 1 && V1Size <= 1) // Just pointer check?
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return NoAlias;
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// Otherwise we have to check to see that the distance is more than
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// the size of the argument... build an index vector that is equal to
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// the arguments provided, except substitute 0's for any variable
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// indexes we find...
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if (TD && cast<PointerType>(
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BasePtr->getType())->getElementType()->isSized()) {
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for (unsigned i = 0; i != GEPOperands.size(); ++i)
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if (!isa<ConstantInt>(GEPOperands[i]))
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GEPOperands[i] =
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Constant::getNullValue(GEPOperands[i]->getType());
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int64_t Offset =
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TD->getIndexedOffset(BasePtr->getType(),
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&GEPOperands[0],
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GEPOperands.size());
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if (Offset >= (int64_t)V2Size || Offset <= -(int64_t)V1Size)
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return NoAlias;
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}
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}
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}
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}
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if (isGEP(V1))
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return aliasGEP(V1, V1Size, V2, V2Size);
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return MayAlias;
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}
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