//===----------------------------------------------------------------------===//
#include "llvm/Analysis/AliasAnalysis.h"
-#include "llvm/Analysis/CaptureTracking.h"
-#include "llvm/Analysis/MemoryBuiltins.h"
#include "llvm/Analysis/Passes.h"
#include "llvm/Constants.h"
#include "llvm/DerivedTypes.h"
#include "llvm/Function.h"
-#include "llvm/GlobalAlias.h"
#include "llvm/GlobalVariable.h"
#include "llvm/Instructions.h"
#include "llvm/IntrinsicInst.h"
#include "llvm/Operator.h"
#include "llvm/Pass.h"
+#include "llvm/Analysis/CaptureTracking.h"
+#include "llvm/Analysis/MemoryBuiltins.h"
+#include "llvm/Analysis/ValueTracking.h"
#include "llvm/Target/TargetData.h"
-#include "llvm/ADT/SmallSet.h"
+#include "llvm/ADT/SmallPtrSet.h"
#include "llvm/ADT/SmallVector.h"
-#include "llvm/ADT/STLExtras.h"
#include "llvm/Support/ErrorHandling.h"
-#include "llvm/Support/GetElementPtrTypeIterator.h"
#include <algorithm>
using namespace llvm;
// Useful predicates
//===----------------------------------------------------------------------===//
-static const Value *GetGEPOperands(const GEPOperator *V,
- SmallVector<Value*, 16> &GEPOps) {
- assert(GEPOps.empty() && "Expect empty list to populate!");
- GEPOps.insert(GEPOps.end(), V->op_begin()+1, V->op_end());
-
- // Accumulate all of the chained indexes into the operand array.
- Value *BasePtr = V->getOperand(0);
- while (1) {
- V = dyn_cast<GEPOperator>(BasePtr);
- if (V == 0) return BasePtr;
-
- // Don't handle folding arbitrary pointer offsets yet.
- if (!isa<Constant>(GEPOps[0]) || !cast<Constant>(GEPOps[0])->isNullValue())
- return BasePtr;
-
- GEPOps.erase(GEPOps.begin()); // Drop the zero index
- GEPOps.insert(GEPOps.begin(), V->op_begin()+1, V->op_end());
- }
-}
-
/// isKnownNonNull - Return true if we know that the specified value is never
/// null.
static bool isKnownNonNull(const Value *V) {
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;
+ }
};
} // End of anonymous namespace
/// global) or not.
bool pointsToConstantMemory(const Value *P);
+ /// 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:
// VisitedPHIs - Track PHI nodes visited by a aliasCheck() call.
SmallPtrSet<const Value*, 16> VisitedPHIs;
AliasResult aliasCheck(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.
- AliasResult
- CheckGEPInstructions(const Type* BasePtr1Ty,
- Value **GEP1Ops, unsigned NumGEP1Ops, unsigned G1Size,
- const Type *BasePtr2Ty,
- Value **GEP2Ops, unsigned NumGEP2Ops, unsigned G2Size);
};
} // End of anonymous namespace
for (CallSite::arg_iterator CI = CS.arg_begin(), CE = CS.arg_end();
CI != CE; ++CI, ++ArgNo) {
// Only look at the no-capture pointer arguments.
- if (!isa<PointerType>((*CI)->getType()) ||
+ if (!(*CI)->getType()->isPointerTy() ||
!CS.paramHasAttr(ArgNo+1, Attribute::NoCapture))
continue;
return NoAA::getModRefInfo(CS1, CS2);
}
-/// DecomposeGEPExpression - If V is a symbolic pointer expression, decompose it
-/// into a base pointer with a constant offset and a number of scaled symbolic
-/// offsets.
-///
-/// When TargetData is around, this function is capable of analyzing everything
-/// that Value::getUnderlyingObject() can look through. When not, it just looks
-/// through pointer casts.
-///
-/// FIXME: Move this out to ValueTracking.cpp
-///
-static const Value *DecomposeGEPExpression(const Value *V, int64_t &BaseOffs,
- SmallVectorImpl<std::pair<const Value*, uint64_t> > &VarIndices,
- const TargetData *TD) {
- // FIXME: Should limit depth like getUnderlyingObject?
- BaseOffs = 0;
- while (1) {
- // See if this is a bitcast or GEP.
- const Operator *Op = dyn_cast<Operator>(V);
- if (Op == 0) {
- // The only non-operator case we can handle are GlobalAliases.
- if (const GlobalAlias *GA = dyn_cast<GlobalAlias>(V)) {
- if (!GA->mayBeOverridden()) {
- V = GA->getAliasee();
- continue;
- }
- }
- return V;
- }
-
- if (Op->getOpcode() == Instruction::BitCast) {
- V = Op->getOperand(0);
- continue;
- }
+/// GetIndiceDifference - Dest and Src are the variable indices from two
+/// decomposed GetElementPtr instructions GEP1 and GEP2 which have common base
+/// pointers. Subtract the GEP2 indices from GEP1 to find the symbolic
+/// difference between the two pointers.
+static void GetIndiceDifference(
+ SmallVectorImpl<std::pair<const Value*, int64_t> > &Dest,
+ const SmallVectorImpl<std::pair<const Value*, int64_t> > &Src) {
+ if (Src.empty()) return;
+
+ for (unsigned i = 0, e = Src.size(); i != e; ++i) {
+ const Value *V = Src[i].first;
+ int64_t Scale = Src[i].second;
- const GEPOperator *GEPOp = dyn_cast<GEPOperator>(Op);
- if (GEPOp == 0)
- return V;
-
- // Don't attempt to analyze GEPs over unsized objects.
- if (!cast<PointerType>(GEPOp->getOperand(0)->getType())
- ->getElementType()->isSized())
- return V;
-
- // If we are lacking TargetData information, we can't compute the offets of
- // elements computed by GEPs. However, we can handle bitcast equivalent
- // GEPs.
- if (!TD) {
- if (!GEPOp->hasAllZeroIndices())
- return V;
- V = GEPOp->getOperand(0);
- continue;
- }
-
- // Walk the indices of the GEP, accumulating them into BaseOff/VarIndices.
- gep_type_iterator GTI = gep_type_begin(GEPOp);
- for (User::const_op_iterator I = next(GEPOp->op_begin()),
- E = GEPOp->op_end(); I != E; ++I) {
- Value *Index = *I;
- // Compute the (potentially symbolic) offset in bytes for this index.
- if (const StructType *STy = dyn_cast<StructType>(*GTI++)) {
- // For a struct, add the member offset.
- unsigned FieldNo = cast<ConstantInt>(Index)->getZExtValue();
- if (FieldNo == 0) continue;
-
- BaseOffs += TD->getStructLayout(STy)->getElementOffset(FieldNo);
- continue;
- }
-
- // For an array/pointer, add the element offset, explicitly scaled.
- if (ConstantInt *CIdx = dyn_cast<ConstantInt>(Index)) {
- if (CIdx->isZero()) continue;
- BaseOffs += TD->getTypeAllocSize(*GTI)*CIdx->getSExtValue();
- continue;
- }
-
- // TODO: Could handle linear expressions here like A[X+1], also A[X*4|1].
- uint64_t Scale = TD->getTypeAllocSize(*GTI);
-
- // If we already had an occurrance of this index variable, merge this
- // scale into it. For example, we want to handle:
- // A[x][x] -> x*16 + x*4 -> x*20
- for (unsigned i = 0, e = VarIndices.size(); i != e; ++i) {
- if (VarIndices[i].first == Index) {
- Scale += VarIndices[i].second;
- VarIndices.erase(VarIndices.begin()+i);
- break;
- }
- }
+ // Find V in Dest. This is N^2, but pointer indices almost never have more
+ // than a few variable indexes.
+ for (unsigned j = 0, e = Dest.size(); j != e; ++j) {
+ if (Dest[j].first != V) continue;
- // Make sure that we have a scale that makes sense for this target's
- // pointer size.
- if (unsigned ShiftBits = 64-TD->getPointerSizeInBits()) {
- Scale <<= ShiftBits;
- Scale >>= ShiftBits;
- }
-
- if (Scale)
- VarIndices.push_back(std::make_pair(Index, Scale));
+ // If we found it, subtract off Scale V's from the entry in Dest. If it
+ // goes to zero, remove the entry.
+ if (Dest[j].second != Scale)
+ Dest[j].second -= Scale;
+ else
+ Dest.erase(Dest.begin()+j);
+ Scale = 0;
+ break;
}
- // Analyze the base pointer next.
- V = GEPOp->getOperand(0);
+ // If we didn't consume this entry, add it to the end of the Dest list.
+ if (Scale)
+ Dest.push_back(std::make_pair(V, -Scale));
}
}
-
/// aliasGEP - Provide a bunch of ad-hoc rules to disambiguate a GEP instruction
/// against another pointer. We know that V1 is a GEP, but we don't know
/// anything about V2. UnderlyingV1 is GEP1->getUnderlyingObject(),
const Value *V2, unsigned V2Size,
const Value *UnderlyingV1,
const Value *UnderlyingV2) {
+ int64_t GEP1BaseOffset;
+ SmallVector<std::pair<const Value*, int64_t>, 4> GEP1VariableIndices;
+
// 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
- // constant expression getelementptrs here.
- //
if (const GEPOperator *GEP2 = dyn_cast<GEPOperator>(V2)) {
- // If V1 and V2 are identical GEPs, just recurse down on both of them.
- // This allows us to analyze things like:
- // P = gep A, 0, i, 1
- // Q = gep B, 0, i, 1
- // by just analyzing A and B. This is even safe for variable indices.
- if (GEP1->getType() == GEP2->getType() &&
- GEP1->getNumOperands() == GEP2->getNumOperands() &&
- GEP1->getOperand(0)->getType() == GEP2->getOperand(0)->getType() &&
- // All operands are the same, ignoring the base.
- std::equal(GEP1->op_begin()+1, GEP1->op_end(), GEP2->op_begin()+1))
- return aliasCheck(GEP1->getOperand(0), V1Size,
- GEP2->getOperand(0), V2Size);
-
- // Drill down into the first non-gep value, to test for must-aliasing of
- // the base pointers.
- while (isa<GEPOperator>(GEP1->getOperand(0)) &&
- GEP1->getOperand(1) ==
- Constant::getNullValue(GEP1->getOperand(1)->getType()))
- GEP1 = cast<GEPOperator>(GEP1->getOperand(0));
- const Value *BasePtr1 = GEP1->getOperand(0);
-
- while (isa<GEPOperator>(GEP2->getOperand(0)) &&
- GEP2->getOperand(1) ==
- Constant::getNullValue(GEP2->getOperand(1)->getType()))
- GEP2 = cast<GEPOperator>(GEP2->getOperand(0));
- const Value *BasePtr2 = GEP2->getOperand(0);
-
// Do the base pointers alias?
- AliasResult BaseAlias = aliasCheck(BasePtr1, ~0U, BasePtr2, ~0U);
- if (BaseAlias == NoAlias) return NoAlias;
- if (BaseAlias == MustAlias) {
- // If the base pointers alias each other exactly, check to see if we can
- // figure out anything about the resultant pointers, to try to prove
- // non-aliasing.
-
- // Collect all of the chained GEP operands together into one simple place
- SmallVector<Value*, 16> GEP1Ops, GEP2Ops;
- BasePtr1 = GetGEPOperands(GEP1, GEP1Ops);
- BasePtr2 = GetGEPOperands(GEP2, GEP2Ops);
-
- // If GetGEPOperands were able to fold to the same must-aliased pointer,
- // do the comparison.
- if (BasePtr1 == BasePtr2) {
- AliasResult GAlias =
- CheckGEPInstructions(BasePtr1->getType(),
- &GEP1Ops[0], GEP1Ops.size(), V1Size,
- BasePtr2->getType(),
- &GEP2Ops[0], GEP2Ops.size(), V2Size);
- if (GAlias != MayAlias)
- return GAlias;
- }
+ AliasResult BaseAlias = aliasCheck(UnderlyingV1, ~0U, UnderlyingV2, ~0U);
+
+ // If we get a No or May, then return it immediately, no amount of analysis
+ // will improve this situation.
+ if (BaseAlias != MustAlias) return BaseAlias;
+
+ // Otherwise, we have a MustAlias. Since the base pointers alias each other
+ // exactly, see if the computed offset from the common pointer tells us
+ // about the relation of the resulting pointer.
+ const Value *GEP1BasePtr =
+ DecomposeGEPExpression(GEP1, GEP1BaseOffset, GEP1VariableIndices, TD);
+
+ int64_t GEP2BaseOffset;
+ SmallVector<std::pair<const Value*, int64_t>, 4> GEP2VariableIndices;
+ const Value *GEP2BasePtr =
+ DecomposeGEPExpression(GEP2, GEP2BaseOffset, GEP2VariableIndices, TD);
+
+ // If DecomposeGEPExpression isn't able to look all the way through the
+ // addressing operation, we must not have TD and this is too complex for us
+ // to handle without it.
+ if (GEP1BasePtr != UnderlyingV1 || GEP2BasePtr != UnderlyingV2) {
+ assert(TD == 0 &&
+ "DecomposeGEPExpression and getUnderlyingObject disagree!");
+ return MayAlias;
}
- }
-
- // Check to see if these two pointers are related by a getelementptr
- // instruction. If one pointer is a GEP with a non-zero index of the other
- // pointer, we know they cannot alias.
- //
- // FIXME: The check below only looks at the size of one of the pointers, not
- // both, this may cause us to miss things.
- if (V1Size == ~0U || V2Size == ~0U)
- return MayAlias;
+
+ // Subtract the GEP2 pointer from the GEP1 pointer to find out their
+ // symbolic difference.
+ GEP1BaseOffset -= GEP2BaseOffset;
+ GetIndiceDifference(GEP1VariableIndices, GEP2VariableIndices);
+
+ } else {
+ // Check to see if these two pointers are related by the getelementptr
+ // instruction. If one pointer is a GEP with a non-zero index of the other
+ // pointer, we know they cannot alias.
- AliasResult R = aliasCheck(UnderlyingV1, ~0U, V2, V2Size);
- if (R != MustAlias)
- // If V2 may alias GEP base pointer, conservatively returns MayAlias.
- // If V2 is known not to alias GEP base pointer, then the two values
- // cannot alias per GEP semantics: "A pointer value formed from a
- // getelementptr instruction is associated with the addresses associated
- // with the first operand of the getelementptr".
- return R;
+ // If both accesses are unknown size, we can't do anything useful here.
+ if (V1Size == ~0U && V2Size == ~0U)
+ return MayAlias;
- int64_t GEP1BaseOffset;
- SmallVector<std::pair<const Value*, uint64_t>, 4> VariableIndices;
- const Value *GEP1BasePtr =
- DecomposeGEPExpression(GEP1, GEP1BaseOffset, VariableIndices, TD);
-
- // If DecomposeGEPExpression isn't able to look all the way through the
- // addressing operation, we must not have TD and this is too complex for us
- // to handle without it.
- if (GEP1BasePtr != UnderlyingV1) {
- assert(TD == 0 &&
- "DecomposeGEPExpression and getUnderlyingObject disagree!");
- return MayAlias;
+ AliasResult R = aliasCheck(UnderlyingV1, ~0U, V2, V2Size);
+ if (R != MustAlias)
+ // If V2 may alias GEP base pointer, conservatively returns MayAlias.
+ // If V2 is known not to alias GEP base pointer, then the two values
+ // cannot alias per GEP semantics: "A pointer value formed from a
+ // getelementptr instruction is associated with the addresses associated
+ // with the first operand of the getelementptr".
+ return R;
+
+ const Value *GEP1BasePtr =
+ DecomposeGEPExpression(GEP1, GEP1BaseOffset, GEP1VariableIndices, TD);
+
+ // If DecomposeGEPExpression isn't able to look all the way through the
+ // addressing operation, we must not have TD and this is too complex for us
+ // to handle without it.
+ if (GEP1BasePtr != UnderlyingV1) {
+ assert(TD == 0 &&
+ "DecomposeGEPExpression and getUnderlyingObject disagree!");
+ return MayAlias;
+ }
}
- // If we have getelementptr <ptr>, 0, 0, 0, 0, ... and V2 must aliases
- // the ptr, the end result is a must alias also.
- if (GEP1BaseOffset == 0 && VariableIndices.empty())
+ // In the two GEP Case, if there is no difference in the offsets of the
+ // computed pointers, the resultant pointers are a must alias. This
+ // hapens when we have two lexically identical GEP's (for example).
+ //
+ // In the other case, if we have getelementptr <ptr>, 0, 0, 0, 0, ... and V2
+ // must aliases the GEP, the end result is a must alias also.
+ if (GEP1BaseOffset == 0 && GEP1VariableIndices.empty())
return MustAlias;
// If we have a known constant offset, see if this offset is larger than the
// multiple of any of our variable indices. This allows us to transform
// things like &A[i][1] because i has a stride of (e.g.) 8 bytes but the 1
// provides an offset of 4 bytes (assuming a <= 4 byte access).
- for (unsigned i = 0, e = VariableIndices.size(); i != e && GEP1BaseOffset;++i)
- if (int64_t RemovedOffset = GEP1BaseOffset/VariableIndices[i].second)
- GEP1BaseOffset -= RemovedOffset*VariableIndices[i].second;
+ for (unsigned i = 0, e = GEP1VariableIndices.size();
+ i != e && GEP1BaseOffset;++i)
+ if (int64_t RemovedOffset = GEP1BaseOffset/GEP1VariableIndices[i].second)
+ GEP1BaseOffset -= RemovedOffset*GEP1VariableIndices[i].second;
// If our known offset is bigger than the access size, we know we don't have
// an alias.
AliasAnalysis::AliasResult
BasicAliasAnalysis::aliasCheck(const Value *V1, unsigned V1Size,
const Value *V2, unsigned V2Size) {
+ // If either of the memory references is empty, it doesn't matter what the
+ // pointer values are.
+ if (V1Size == 0 || V2Size == 0)
+ return NoAlias;
+
// 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()))
+ if (!V1->getType()->isPointerTy() || !V2->getType()->isPointerTy())
return NoAlias; // Scalars cannot alias each other
// Figure out what objects these things are pointing to if we can.
return MayAlias;
}
-// This function is used to determine if the indices of two GEP instructions are
-// equal. V1 and V2 are the indices.
-static bool IndexOperandsEqual(Value *V1, Value *V2) {
- if (V1->getType() == V2->getType())
- return V1 == V2;
- if (Constant *C1 = dyn_cast<Constant>(V1))
- if (Constant *C2 = dyn_cast<Constant>(V2)) {
- // Sign extend the constants to long types, if necessary
- if (C1->getType() != Type::getInt64Ty(C1->getContext()))
- C1 = ConstantExpr::getSExt(C1, Type::getInt64Ty(C1->getContext()));
- if (C2->getType() != Type::getInt64Ty(C1->getContext()))
- C2 = ConstantExpr::getSExt(C2, Type::getInt64Ty(C1->getContext()));
- return C1 == C2;
- }
- return false;
-}
-
-/// CheckGEPInstructions - Check two GEP instructions with known must-aliasing
-/// base pointers. This checks to see if the index expressions preclude the
-/// pointers from aliasing.
-AliasAnalysis::AliasResult
-BasicAliasAnalysis::CheckGEPInstructions(
- const Type* BasePtr1Ty, Value **GEP1Ops, unsigned NumGEP1Ops, unsigned G1S,
- const Type *BasePtr2Ty, Value **GEP2Ops, unsigned NumGEP2Ops, unsigned G2S) {
- // We currently can't handle the case when the base pointers have different
- // primitive types. Since this is uncommon anyway, we are happy being
- // extremely conservative.
- if (BasePtr1Ty != BasePtr2Ty)
- return MayAlias;
-
- const PointerType *GEPPointerTy = cast<PointerType>(BasePtr1Ty);
-
- // Find the (possibly empty) initial sequence of equal values... which are not
- // necessarily constants.
- unsigned NumGEP1Operands = NumGEP1Ops, NumGEP2Operands = NumGEP2Ops;
- unsigned MinOperands = std::min(NumGEP1Operands, NumGEP2Operands);
- unsigned MaxOperands = std::max(NumGEP1Operands, NumGEP2Operands);
- unsigned UnequalOper = 0;
- while (UnequalOper != MinOperands &&
- IndexOperandsEqual(GEP1Ops[UnequalOper], GEP2Ops[UnequalOper])) {
- // Advance through the type as we go...
- ++UnequalOper;
- if (const CompositeType *CT = dyn_cast<CompositeType>(BasePtr1Ty))
- BasePtr1Ty = CT->getTypeAtIndex(GEP1Ops[UnequalOper-1]);
- else {
- // If all operands equal each other, then the derived pointers must
- // alias each other...
- BasePtr1Ty = 0;
- assert(UnequalOper == NumGEP1Operands && UnequalOper == NumGEP2Operands &&
- "Ran out of type nesting, but not out of operands?");
- return MustAlias;
- }
- }
-
- // If we have seen all constant operands, and run out of indexes on one of the
- // getelementptrs, check to see if the tail of the leftover one is all zeros.
- // If so, return mustalias.
- if (UnequalOper == MinOperands) {
- if (NumGEP1Ops < NumGEP2Ops) {
- std::swap(GEP1Ops, GEP2Ops);
- std::swap(NumGEP1Ops, NumGEP2Ops);
- }
-
- bool AllAreZeros = true;
- for (unsigned i = UnequalOper; i != MaxOperands; ++i)
- if (!isa<Constant>(GEP1Ops[i]) ||
- !cast<Constant>(GEP1Ops[i])->isNullValue()) {
- AllAreZeros = false;
- break;
- }
- if (AllAreZeros) return MustAlias;
- }
-
-
- // So now we know that the indexes derived from the base pointers,
- // which are known to alias, are different. We can still determine a
- // no-alias result if there are differing constant pairs in the index
- // chain. For example:
- // A[i][0] != A[j][1] iff (&A[0][1]-&A[0][0] >= std::max(G1S, G2S))
- //
- // We have to be careful here about array accesses. In particular, consider:
- // A[1][0] vs A[0][i]
- // In this case, we don't *know* that the array will be accessed in bounds:
- // the index could even be negative. Because of this, we have to
- // conservatively *give up* and return may alias. We disregard differing
- // array subscripts that are followed by a variable index without going
- // through a struct.
- //
- unsigned SizeMax = std::max(G1S, G2S);
- if (SizeMax == ~0U) return MayAlias; // Avoid frivolous work.
-
- // Scan for the first operand that is constant and unequal in the
- // two getelementptrs...
- unsigned FirstConstantOper = UnequalOper;
- for (; FirstConstantOper != MinOperands; ++FirstConstantOper) {
- const Value *G1Oper = GEP1Ops[FirstConstantOper];
- const Value *G2Oper = GEP2Ops[FirstConstantOper];
-
- if (G1Oper != G2Oper) // Found non-equal constant indexes...
- if (Constant *G1OC = dyn_cast<ConstantInt>(const_cast<Value*>(G1Oper)))
- if (Constant *G2OC = dyn_cast<ConstantInt>(const_cast<Value*>(G2Oper))){
- if (G1OC->getType() != G2OC->getType()) {
- // Sign extend both operands to long.
- const Type *Int64Ty = Type::getInt64Ty(G1OC->getContext());
- if (G1OC->getType() != Int64Ty)
- G1OC = ConstantExpr::getSExt(G1OC, Int64Ty);
- if (G2OC->getType() != Int64Ty)
- G2OC = ConstantExpr::getSExt(G2OC, Int64Ty);
- GEP1Ops[FirstConstantOper] = G1OC;
- GEP2Ops[FirstConstantOper] = G2OC;
- }
-
- if (G1OC != G2OC) {
- // Handle the "be careful" case above: if this is an array/vector
- // subscript, scan for a subsequent variable array index.
- if (const SequentialType *STy =
- dyn_cast<SequentialType>(BasePtr1Ty)) {
- const Type *NextTy = STy;
- bool isBadCase = false;
-
- for (unsigned Idx = FirstConstantOper;
- Idx != MinOperands && isa<SequentialType>(NextTy); ++Idx) {
- const Value *V1 = GEP1Ops[Idx], *V2 = GEP2Ops[Idx];
- if (!isa<Constant>(V1) || !isa<Constant>(V2)) {
- isBadCase = true;
- break;
- }
- // If the array is indexed beyond the bounds of the static type
- // at this level, it will also fall into the "be careful" case.
- // It would theoretically be possible to analyze these cases,
- // but for now just be conservatively correct.
- if (const ArrayType *ATy = dyn_cast<ArrayType>(STy))
- if (cast<ConstantInt>(G1OC)->getZExtValue() >=
- ATy->getNumElements() ||
- cast<ConstantInt>(G2OC)->getZExtValue() >=
- ATy->getNumElements()) {
- isBadCase = true;
- break;
- }
- if (const VectorType *VTy = dyn_cast<VectorType>(STy))
- if (cast<ConstantInt>(G1OC)->getZExtValue() >=
- VTy->getNumElements() ||
- cast<ConstantInt>(G2OC)->getZExtValue() >=
- VTy->getNumElements()) {
- isBadCase = true;
- break;
- }
- STy = cast<SequentialType>(NextTy);
- NextTy = cast<SequentialType>(NextTy)->getElementType();
- }
-
- if (isBadCase) G1OC = 0;
- }
-
- // Make sure they are comparable (ie, not constant expressions), and
- // make sure the GEP with the smaller leading constant is GEP1.
- if (G1OC) {
- Constant *Compare = ConstantExpr::getICmp(ICmpInst::ICMP_SGT,
- G1OC, G2OC);
- if (ConstantInt *CV = dyn_cast<ConstantInt>(Compare)) {
- if (CV->getZExtValue()) { // If they are comparable and G2 > G1
- std::swap(GEP1Ops, GEP2Ops); // Make GEP1 < GEP2
- std::swap(NumGEP1Ops, NumGEP2Ops);
- }
- break;
- }
- }
- }
- }
- BasePtr1Ty = cast<CompositeType>(BasePtr1Ty)->getTypeAtIndex(G1Oper);
- }
-
- // No shared constant operands, and we ran out of common operands. At this
- // point, the GEP instructions have run through all of their operands, and we
- // haven't found evidence that there are any deltas between the GEP's.
- // However, one GEP may have more operands than the other. If this is the
- // case, there may still be hope. Check this now.
- if (FirstConstantOper == MinOperands) {
- // Without TargetData, we won't know what the offsets are.
- if (!TD)
- return MayAlias;
-
- // Make GEP1Ops be the longer one if there is a longer one.
- if (NumGEP1Ops < NumGEP2Ops) {
- std::swap(GEP1Ops, GEP2Ops);
- std::swap(NumGEP1Ops, NumGEP2Ops);
- }
-
- // Is there anything to check?
- if (NumGEP1Ops > MinOperands) {
- for (unsigned i = FirstConstantOper; i != MaxOperands; ++i)
- if (isa<ConstantInt>(GEP1Ops[i]) &&
- !cast<ConstantInt>(GEP1Ops[i])->isZero()) {
- // Yup, there's a constant in the tail. Set all variables to
- // constants in the GEP instruction to make it suitable for
- // TargetData::getIndexedOffset.
- for (i = 0; i != MaxOperands; ++i)
- if (!isa<ConstantInt>(GEP1Ops[i]))
- GEP1Ops[i] = Constant::getNullValue(GEP1Ops[i]->getType());
- // Okay, now get the offset. This is the relative offset for the full
- // instruction.
- int64_t Offset1 = TD->getIndexedOffset(GEPPointerTy, GEP1Ops,
- NumGEP1Ops);
-
- // Now check without any constants at the end.
- int64_t Offset2 = TD->getIndexedOffset(GEPPointerTy, GEP1Ops,
- MinOperands);
-
- // Make sure we compare the absolute difference.
- if (Offset1 > Offset2)
- std::swap(Offset1, Offset2);
-
- // If the tail provided a bit enough offset, return noalias!
- if ((uint64_t)(Offset2-Offset1) >= SizeMax)
- return NoAlias;
- // Otherwise break - we don't look for another constant in the tail.
- break;
- }
- }
-
- // Couldn't find anything useful.
- return MayAlias;
- }
-
- // If there are non-equal constants arguments, then we can figure
- // out a minimum known delta between the two index expressions... at
- // this point we know that the first constant index of GEP1 is less
- // than the first constant index of GEP2.
-
- // Advance BasePtr[12]Ty over this first differing constant operand.
- BasePtr2Ty = cast<CompositeType>(BasePtr1Ty)->
- getTypeAtIndex(GEP2Ops[FirstConstantOper]);
- BasePtr1Ty = cast<CompositeType>(BasePtr1Ty)->
- getTypeAtIndex(GEP1Ops[FirstConstantOper]);
-
- // We are going to be using TargetData::getIndexedOffset to determine the
- // offset that each of the GEP's is reaching. To do this, we have to convert
- // all variable references to constant references. To do this, we convert the
- // initial sequence of array subscripts into constant zeros to start with.
- const Type *ZeroIdxTy = GEPPointerTy;
- for (unsigned i = 0; i != FirstConstantOper; ++i) {
- if (!isa<StructType>(ZeroIdxTy))
- GEP1Ops[i] = GEP2Ops[i] =
- Constant::getNullValue(Type::getInt32Ty(ZeroIdxTy->getContext()));
-
- if (const CompositeType *CT = dyn_cast<CompositeType>(ZeroIdxTy))
- ZeroIdxTy = CT->getTypeAtIndex(GEP1Ops[i]);
- }
-
- // We know that GEP1Ops[FirstConstantOper] & GEP2Ops[FirstConstantOper] are ok
-
- // Loop over the rest of the operands...
- for (unsigned i = FirstConstantOper+1; i != MaxOperands; ++i) {
- const Value *Op1 = i < NumGEP1Ops ? GEP1Ops[i] : 0;
- const Value *Op2 = i < NumGEP2Ops ? GEP2Ops[i] : 0;
- // If they are equal, use a zero index...
- if (Op1 == Op2 && BasePtr1Ty == BasePtr2Ty) {
- if (!isa<ConstantInt>(Op1))
- GEP1Ops[i] = GEP2Ops[i] = Constant::getNullValue(Op1->getType());
- // Otherwise, just keep the constants we have.
- } else {
- if (Op1) {
- if (const ConstantInt *Op1C = dyn_cast<ConstantInt>(Op1)) {
- // If this is an array index, make sure the array element is in range.
- if (const ArrayType *AT = dyn_cast<ArrayType>(BasePtr1Ty)) {
- if (Op1C->getZExtValue() >= AT->getNumElements())
- return MayAlias; // Be conservative with out-of-range accesses
- } else if (const VectorType *VT = dyn_cast<VectorType>(BasePtr1Ty)) {
- if (Op1C->getZExtValue() >= VT->getNumElements())
- return MayAlias; // Be conservative with out-of-range accesses
- }
-
- } else {
- // GEP1 is known to produce a value less than GEP2. To be
- // conservatively correct, we must assume the largest possible
- // constant is used in this position. This cannot be the initial
- // index to the GEP instructions (because we know we have at least one
- // element before this one with the different constant arguments), so
- // we know that the current index must be into either a struct or
- // array. Because we know it's not constant, this cannot be a
- // structure index. Because of this, we can calculate the maximum
- // value possible.
- //
- if (const ArrayType *AT = dyn_cast<ArrayType>(BasePtr1Ty))
- GEP1Ops[i] =
- ConstantInt::get(Type::getInt64Ty(AT->getContext()),
- AT->getNumElements()-1);
- else if (const VectorType *VT = dyn_cast<VectorType>(BasePtr1Ty))
- GEP1Ops[i] =
- ConstantInt::get(Type::getInt64Ty(VT->getContext()),
- VT->getNumElements()-1);
- }
- }
-
- if (Op2) {
- if (const ConstantInt *Op2C = dyn_cast<ConstantInt>(Op2)) {
- // If this is an array index, make sure the array element is in range.
- if (const ArrayType *AT = dyn_cast<ArrayType>(BasePtr2Ty)) {
- if (Op2C->getZExtValue() >= AT->getNumElements())
- return MayAlias; // Be conservative with out-of-range accesses
- } else if (const VectorType *VT = dyn_cast<VectorType>(BasePtr2Ty)) {
- if (Op2C->getZExtValue() >= VT->getNumElements())
- return MayAlias; // Be conservative with out-of-range accesses
- }
- } else { // Conservatively assume the minimum value for this index
- GEP2Ops[i] = Constant::getNullValue(Op2->getType());
- }
- }
- }
-
- if (BasePtr1Ty && Op1) {
- if (const CompositeType *CT = dyn_cast<CompositeType>(BasePtr1Ty))
- BasePtr1Ty = CT->getTypeAtIndex(GEP1Ops[i]);
- else
- BasePtr1Ty = 0;
- }
-
- if (BasePtr2Ty && Op2) {
- if (const CompositeType *CT = dyn_cast<CompositeType>(BasePtr2Ty))
- BasePtr2Ty = CT->getTypeAtIndex(GEP2Ops[i]);
- else
- BasePtr2Ty = 0;
- }
- }
-
- if (TD && GEPPointerTy->getElementType()->isSized()) {
- int64_t Offset1 =
- TD->getIndexedOffset(GEPPointerTy, GEP1Ops, NumGEP1Ops);
- int64_t Offset2 =
- TD->getIndexedOffset(GEPPointerTy, GEP2Ops, NumGEP2Ops);
- assert(Offset1 != Offset2 &&
- "There is at least one different constant here!");
-
- // Make sure we compare the absolute difference.
- if (Offset1 > Offset2)
- std::swap(Offset1, Offset2);
-
- if ((uint64_t)(Offset2-Offset1) >= SizeMax) {
- //cerr << "Determined that these two GEP's don't alias ["
- // << SizeMax << " bytes]: \n" << *GEP1 << *GEP2;
- return NoAlias;
- }
- }
- return MayAlias;
-}
-
// Make sure that anything that uses AliasAnalysis pulls in this file.
DEFINING_FILE_FOR(BasicAliasAnalysis)
projects / oota-llvm.git / blobdiff