[llvm-commits] [llvm] r84000 - /llvm/trunk/lib/Analysis/BasicAliasAnalysis.cpp
Evan Cheng
evan.cheng at apple.com
Tue Oct 13 11:42:05 PDT 2009
Author: evancheng
Date: Tue Oct 13 13:42:04 2009
New Revision: 84000
URL: http://llvm.org/viewvc/llvm-project?rev=84000&view=rev
Log:
Refactor some code. No functionality changes.
Modified:
llvm/trunk/lib/Analysis/BasicAliasAnalysis.cpp
Modified: llvm/trunk/lib/Analysis/BasicAliasAnalysis.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Analysis/BasicAliasAnalysis.cpp?rev=84000&r1=83999&r2=84000&view=diff
==============================================================================
--- llvm/trunk/lib/Analysis/BasicAliasAnalysis.cpp (original)
+++ llvm/trunk/lib/Analysis/BasicAliasAnalysis.cpp Tue Oct 13 13:42:04 2009
@@ -215,6 +215,11 @@
bool pointsToConstantMemory(const Value *P);
private:
+ // aliasGEP - Provide a bunch of ad-hoc rules to disambiguate a GEP instruction
+ // against another.
+ AliasResult aliasGEP(const Value *V1, unsigned V1Size,
+ const Value *V2, unsigned V2Size);
+
// CheckGEPInstructions - Check two GEP instructions with known
// must-aliasing base pointers. This checks to see if the index expressions
// preclude the pointers from aliasing...
@@ -329,61 +334,12 @@
return NoAA::getModRefInfo(CS1, CS2);
}
-
-// alias - Provide a bunch of ad-hoc rules to disambiguate in common cases, such
-// as array references.
+// aliasGEP - Provide a bunch of ad-hoc rules to disambiguate a GEP instruction
+// against another.
//
AliasAnalysis::AliasResult
-BasicAliasAnalysis::alias(const Value *V1, unsigned V1Size,
- const Value *V2, unsigned V2Size) {
- // Strip off any casts if they exist.
- V1 = V1->stripPointerCasts();
- V2 = V2->stripPointerCasts();
-
- // Are we checking for alias of the same value?
- if (V1 == V2) return MustAlias;
-
- if (!isa<PointerType>(V1->getType()) || !isa<PointerType>(V2->getType()))
- return NoAlias; // Scalars cannot alias each other
-
- // Figure out what objects these things are pointing to if we can.
- const Value *O1 = V1->getUnderlyingObject();
- const Value *O2 = V2->getUnderlyingObject();
-
- if (O1 != O2) {
- // If V1/V2 point to two different objects we know that we have no alias.
- if (isIdentifiedObject(O1) && isIdentifiedObject(O2))
- return NoAlias;
-
- // Arguments can't alias with local allocations or noalias calls.
- if ((isa<Argument>(O1) && (isa<AllocationInst>(O2) || isNoAliasCall(O2))) ||
- (isa<Argument>(O2) && (isa<AllocationInst>(O1) || isNoAliasCall(O1))))
- return NoAlias;
-
- // Most objects can't alias null.
- if ((isa<ConstantPointerNull>(V2) && isKnownNonNull(O1)) ||
- (isa<ConstantPointerNull>(V1) && isKnownNonNull(O2)))
- return NoAlias;
- }
-
- // If the size of one access is larger than the entire object on the other
- // side, then we know such behavior is undefined and can assume no alias.
- LLVMContext &Context = V1->getContext();
- if (TD)
- if ((V1Size != ~0U && isObjectSmallerThan(O2, V1Size, Context, *TD)) ||
- (V2Size != ~0U && isObjectSmallerThan(O1, V2Size, Context, *TD)))
- return NoAlias;
-
- // If one pointer is the result of a call/invoke and the other is a
- // non-escaping local object, then we know the object couldn't escape to a
- // point where the call could return it.
- if ((isa<CallInst>(O1) || isa<InvokeInst>(O1)) &&
- isNonEscapingLocalObject(O2) && O1 != O2)
- return NoAlias;
- if ((isa<CallInst>(O2) || isa<InvokeInst>(O2)) &&
- isNonEscapingLocalObject(O1) && O1 != O2)
- return NoAlias;
-
+BasicAliasAnalysis::aliasGEP(const Value *V1, unsigned V1Size,
+ const Value *V2, unsigned V2Size) {
// If we have two gep instructions with must-alias'ing base pointers, figure
// out if the indexes to the GEP tell us anything about the derived pointer.
// Note that we also handle chains of getelementptr instructions as well as
@@ -451,63 +407,121 @@
// instruction. If one pointer is a GEP with a non-zero index of the other
// pointer, we know they cannot alias.
//
- if (isGEP(V2)) {
- std::swap(V1, V2);
- std::swap(V1Size, V2Size);
- }
+ if (V1Size == ~0U || V2Size == ~0U)
+ return MayAlias;
- if (V1Size != ~0U && V2Size != ~0U)
- if (isGEP(V1)) {
- SmallVector<Value*, 16> GEPOperands;
- const Value *BasePtr = GetGEPOperands(V1, GEPOperands);
-
- AliasResult R = alias(BasePtr, V1Size, V2, V2Size);
- if (R == MustAlias) {
- // If there is at least one non-zero constant index, we know they cannot
- // alias.
- bool ConstantFound = false;
- bool AllZerosFound = true;
- for (unsigned i = 0, e = GEPOperands.size(); i != e; ++i)
- if (const Constant *C = dyn_cast<Constant>(GEPOperands[i])) {
- if (!C->isNullValue()) {
- ConstantFound = true;
- AllZerosFound = false;
- break;
- }
- } else {
- AllZerosFound = false;
- }
+ SmallVector<Value*, 16> GEPOperands;
+ const Value *BasePtr = GetGEPOperands(V1, GEPOperands);
- // If we have getelementptr <ptr>, 0, 0, 0, 0, ... and V2 must aliases
- // the ptr, the end result is a must alias also.
- if (AllZerosFound)
- return MustAlias;
+ AliasResult R = alias(BasePtr, V1Size, V2, V2Size);
+ if (R == MustAlias) {
+ // If there is at least one non-zero constant index, we know they cannot
+ // alias.
+ bool ConstantFound = false;
+ bool AllZerosFound = true;
+ for (unsigned i = 0, e = GEPOperands.size(); i != e; ++i)
+ if (const Constant *C = dyn_cast<Constant>(GEPOperands[i])) {
+ if (!C->isNullValue()) {
+ ConstantFound = true;
+ AllZerosFound = false;
+ break;
+ }
+ } else {
+ AllZerosFound = false;
+ }
- if (ConstantFound) {
- if (V2Size <= 1 && V1Size <= 1) // Just pointer check?
- return NoAlias;
+ // If we have getelementptr <ptr>, 0, 0, 0, 0, ... and V2 must aliases
+ // the ptr, the end result is a must alias also.
+ if (AllZerosFound)
+ return MustAlias;
- // Otherwise we have to check to see that the distance is more than
- // the size of the argument... build an index vector that is equal to
- // the arguments provided, except substitute 0's for any variable
- // indexes we find...
- if (TD && cast<PointerType>(
- BasePtr->getType())->getElementType()->isSized()) {
- for (unsigned i = 0; i != GEPOperands.size(); ++i)
- if (!isa<ConstantInt>(GEPOperands[i]))
- GEPOperands[i] =
- Constant::getNullValue(GEPOperands[i]->getType());
- int64_t Offset =
- TD->getIndexedOffset(BasePtr->getType(),
- &GEPOperands[0],
- GEPOperands.size());
+ if (ConstantFound) {
+ if (V2Size <= 1 && V1Size <= 1) // Just pointer check?
+ return NoAlias;
+
+ // Otherwise we have to check to see that the distance is more than
+ // the size of the argument... build an index vector that is equal to
+ // the arguments provided, except substitute 0's for any variable
+ // indexes we find...
+ if (TD &&
+ cast<PointerType>(BasePtr->getType())->getElementType()->isSized()) {
+ for (unsigned i = 0; i != GEPOperands.size(); ++i)
+ if (!isa<ConstantInt>(GEPOperands[i]))
+ GEPOperands[i] = Constant::getNullValue(GEPOperands[i]->getType());
+ int64_t Offset =
+ TD->getIndexedOffset(BasePtr->getType(),
+ &GEPOperands[0],
+ GEPOperands.size());
- if (Offset >= (int64_t)V2Size || Offset <= -(int64_t)V1Size)
- return NoAlias;
- }
- }
+ if (Offset >= (int64_t)V2Size || Offset <= -(int64_t)V1Size)
+ return NoAlias;
}
}
+ }
+
+ return MayAlias;
+}
+
+// alias - Provide a bunch of ad-hoc rules to disambiguate in common cases, such
+// as array references.
+//
+AliasAnalysis::AliasResult
+BasicAliasAnalysis::alias(const Value *V1, unsigned V1Size,
+ const Value *V2, unsigned V2Size) {
+ // Strip off any casts if they exist.
+ V1 = V1->stripPointerCasts();
+ V2 = V2->stripPointerCasts();
+
+ // Are we checking for alias of the same value?
+ if (V1 == V2) return MustAlias;
+
+ if (!isa<PointerType>(V1->getType()) || !isa<PointerType>(V2->getType()))
+ return NoAlias; // Scalars cannot alias each other
+
+ // Figure out what objects these things are pointing to if we can.
+ const Value *O1 = V1->getUnderlyingObject();
+ const Value *O2 = V2->getUnderlyingObject();
+
+ if (O1 != O2) {
+ // If V1/V2 point to two different objects we know that we have no alias.
+ if (isIdentifiedObject(O1) && isIdentifiedObject(O2))
+ return NoAlias;
+
+ // Arguments can't alias with local allocations or noalias calls.
+ if ((isa<Argument>(O1) && (isa<AllocationInst>(O2) || isNoAliasCall(O2))) ||
+ (isa<Argument>(O2) && (isa<AllocationInst>(O1) || isNoAliasCall(O1))))
+ return NoAlias;
+
+ // Most objects can't alias null.
+ if ((isa<ConstantPointerNull>(V2) && isKnownNonNull(O1)) ||
+ (isa<ConstantPointerNull>(V1) && isKnownNonNull(O2)))
+ return NoAlias;
+ }
+
+ // If the size of one access is larger than the entire object on the other
+ // side, then we know such behavior is undefined and can assume no alias.
+ LLVMContext &Context = V1->getContext();
+ if (TD)
+ if ((V1Size != ~0U && isObjectSmallerThan(O2, V1Size, Context, *TD)) ||
+ (V2Size != ~0U && isObjectSmallerThan(O1, V2Size, Context, *TD)))
+ return NoAlias;
+
+ // If one pointer is the result of a call/invoke and the other is a
+ // non-escaping local object, then we know the object couldn't escape to a
+ // point where the call could return it.
+ if ((isa<CallInst>(O1) || isa<InvokeInst>(O1)) &&
+ isNonEscapingLocalObject(O2) && O1 != O2)
+ return NoAlias;
+ if ((isa<CallInst>(O2) || isa<InvokeInst>(O2)) &&
+ isNonEscapingLocalObject(O1) && O1 != O2)
+ return NoAlias;
+
+ if (!isGEP(V1) && isGEP(V2)) {
+ std::swap(V1, V2);
+ std::swap(V1Size, V2Size);
+ }
+ if (isGEP(V1))
+ return aliasGEP(V1, V1Size, V2, V2Size);
return MayAlias;
}
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