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Change the other half of aliasGEP (which handles GEP differencing) to use DecomposeGEPExpression. This dramatically simplifies and shrinks the code by eliminating the horrible CheckGEPInstructions method, fixes a miscompilation (@test3) and makes the code more aggressive. In particular, we now handle the @test4 case, which is reduced from the SmallPtrSet constructor. Missing this caused us to emit a variable length memset instead of a fixed size one.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@89922 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Chris Lattner
parent
4b7d0d9727
commit
d84eb911a9
@ -39,26 +39,6 @@ using namespace llvm;
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// Useful predicates
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//===----------------------------------------------------------------------===//
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static const Value *GetGEPOperands(const GEPOperator *V,
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SmallVector<Value*, 16> &GEPOps) {
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assert(GEPOps.empty() && "Expect empty list to populate!");
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GEPOps.insert(GEPOps.end(), V->op_begin()+1, V->op_end());
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// Accumulate all of the chained indexes into the operand array.
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Value *BasePtr = V->getOperand(0);
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while (1) {
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V = dyn_cast<GEPOperator>(BasePtr);
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if (V == 0) return BasePtr;
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// Don't handle folding arbitrary pointer offsets yet.
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if (!isa<Constant>(GEPOps[0]) || !cast<Constant>(GEPOps[0])->isNullValue())
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return BasePtr;
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GEPOps.erase(GEPOps.begin()); // Drop the zero index
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GEPOps.insert(GEPOps.begin(), V->op_begin()+1, V->op_end());
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}
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}
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/// isKnownNonNull - Return true if we know that the specified value is never
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/// null.
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static bool isKnownNonNull(const Value *V) {
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@ -235,15 +215,6 @@ namespace {
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AliasResult aliasCheck(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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AliasResult
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CheckGEPInstructions(const Type* BasePtr1Ty,
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Value **GEP1Ops, unsigned NumGEP1Ops, unsigned G1Size,
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const Type *BasePtr2Ty,
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Value **GEP2Ops, unsigned NumGEP2Ops, unsigned G2Size);
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};
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} // End of anonymous namespace
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@ -418,7 +389,7 @@ BasicAliasAnalysis::getModRefInfo(CallSite CS1, CallSite CS2) {
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/// FIXME: Move this out to ValueTracking.cpp
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///
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static const Value *DecomposeGEPExpression(const Value *V, int64_t &BaseOffs,
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SmallVectorImpl<std::pair<const Value*, uint64_t> > &VarIndices,
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SmallVectorImpl<std::pair<const Value*, int64_t> > &VarIndices,
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const TargetData *TD) {
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// FIXME: Should limit depth like getUnderlyingObject?
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BaseOffs = 0;
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@ -488,6 +459,7 @@ static const Value *DecomposeGEPExpression(const Value *V, int64_t &BaseOffs,
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// If we already had an occurrance of this index variable, merge this
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// scale into it. For example, we want to handle:
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// A[x][x] -> x*16 + x*4 -> x*20
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// This also ensures that 'x' only appears in the index list once.
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for (unsigned i = 0, e = VarIndices.size(); i != e; ++i) {
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if (VarIndices[i].first == Index) {
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Scale += VarIndices[i].second;
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@ -512,6 +484,39 @@ static const Value *DecomposeGEPExpression(const Value *V, int64_t &BaseOffs,
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}
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}
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/// GetIndiceDifference - Dest and Src are the variable indices from two
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/// decomposed GetElementPtr instructions GEP1 and GEP2 which have common base
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/// pointers. Subtract the GEP2 indices from GEP1 to find the symbolic
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/// difference between the two pointers.
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static void GetIndiceDifference(
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SmallVectorImpl<std::pair<const Value*, int64_t> > &Dest,
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const SmallVectorImpl<std::pair<const Value*, int64_t> > &Src) {
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if (Src.empty()) return;
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for (unsigned i = 0, e = Src.size(); i != e; ++i) {
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const Value *V = Src[i].first;
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int64_t Scale = Src[i].second;
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// Find V in Dest. This is N^2, but pointer indices almost never have more
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// than a few variable indexes.
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for (unsigned j = 0, e = Dest.size(); j != e; ++j) {
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if (Dest[j].first != V) continue;
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// If we found it, subtract off Scale V's from the entry in Dest. If it
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// goes to zero, remove the entry.
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if (Dest[j].second != Scale)
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Dest[j].second -= Scale;
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else
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Dest.erase(Dest.begin()+j);
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Scale = 0;
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break;
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}
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// If we didn't consume this entry, add it to the end of the Dest list.
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if (Scale)
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Dest.push_back(std::make_pair(V, -Scale));
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}
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}
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/// aliasGEP - Provide a bunch of ad-hoc rules to disambiguate a GEP instruction
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/// against another pointer. We know that V1 is a GEP, but we don't know
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@ -523,101 +528,83 @@ BasicAliasAnalysis::aliasGEP(const GEPOperator *GEP1, unsigned V1Size,
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const Value *V2, unsigned V2Size,
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const Value *UnderlyingV1,
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const Value *UnderlyingV2) {
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int64_t GEP1BaseOffset;
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SmallVector<std::pair<const Value*, int64_t>, 4> GEP1VariableIndices;
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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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// constant expression getelementptrs here.
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//
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if (const GEPOperator *GEP2 = dyn_cast<GEPOperator>(V2)) {
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// If V1 and V2 are identical GEPs, just recurse down on both of them.
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// This allows us to analyze things like:
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// P = gep A, 0, i, 1
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// Q = gep B, 0, i, 1
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// by just analyzing A and B. This is even safe for variable indices.
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if (GEP1->getType() == GEP2->getType() &&
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GEP1->getNumOperands() == GEP2->getNumOperands() &&
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GEP1->getOperand(0)->getType() == GEP2->getOperand(0)->getType() &&
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// All operands are the same, ignoring the base.
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std::equal(GEP1->op_begin()+1, GEP1->op_end(), GEP2->op_begin()+1))
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return aliasCheck(GEP1->getOperand(0), V1Size,
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GEP2->getOperand(0), V2Size);
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// Drill down into the first non-gep value, to test for must-aliasing of
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// the base pointers.
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while (isa<GEPOperator>(GEP1->getOperand(0)) &&
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GEP1->getOperand(1) ==
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Constant::getNullValue(GEP1->getOperand(1)->getType()))
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GEP1 = cast<GEPOperator>(GEP1->getOperand(0));
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const Value *BasePtr1 = GEP1->getOperand(0);
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while (isa<GEPOperator>(GEP2->getOperand(0)) &&
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GEP2->getOperand(1) ==
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Constant::getNullValue(GEP2->getOperand(1)->getType()))
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GEP2 = cast<GEPOperator>(GEP2->getOperand(0));
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const Value *BasePtr2 = GEP2->getOperand(0);
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// Do the base pointers alias?
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AliasResult BaseAlias = aliasCheck(BasePtr1, ~0U, BasePtr2, ~0U);
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if (BaseAlias == NoAlias) return NoAlias;
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if (BaseAlias == MustAlias) {
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// If the base pointers alias each other exactly, check to see if we can
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// figure out anything about the resultant pointers, to try to prove
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// non-aliasing.
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AliasResult BaseAlias = aliasCheck(UnderlyingV1, ~0U, UnderlyingV2, ~0U);
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// If we get a No or May, then return it immediately, no amount of analysis
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// will improve this situation.
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if (BaseAlias != MustAlias) return BaseAlias;
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// Otherwise, we have a MustAlias. Since the base pointers alias each other
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// exactly, see if the computed offset from the common pointer tells us
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// about the relation of the resulting pointer.
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const Value *GEP1BasePtr =
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DecomposeGEPExpression(GEP1, GEP1BaseOffset, GEP1VariableIndices, TD);
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int64_t GEP2BaseOffset;
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SmallVector<std::pair<const Value*, int64_t>, 4> GEP2VariableIndices;
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const Value *GEP2BasePtr =
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DecomposeGEPExpression(GEP2, GEP2BaseOffset, GEP2VariableIndices, TD);
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// If DecomposeGEPExpression isn't able to look all the way through the
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// addressing operation, we must not have TD and this is too complex for us
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// to handle without it.
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if (GEP1BasePtr != UnderlyingV1 || GEP2BasePtr != UnderlyingV2) {
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assert(TD == 0 &&
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"DecomposeGEPExpression and getUnderlyingObject disagree!");
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return MayAlias;
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}
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// Subtract the GEP2 pointer from the GEP1 pointer to find out their
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// symbolic difference.
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GEP1BaseOffset -= GEP2BaseOffset;
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GetIndiceDifference(GEP1VariableIndices, GEP2VariableIndices);
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} else {
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// Check to see if these two pointers are related by the getelementptr
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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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// FIXME: The check below only looks at the size of one of the pointers, not
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// both, this may cause us to miss things.
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if (V1Size == ~0U || V2Size == ~0U)
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return MayAlias;
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// Collect all of the chained GEP operands together into one simple place
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SmallVector<Value*, 16> GEP1Ops, GEP2Ops;
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BasePtr1 = GetGEPOperands(GEP1, GEP1Ops);
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BasePtr2 = GetGEPOperands(GEP2, GEP2Ops);
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AliasResult R = aliasCheck(UnderlyingV1, ~0U, V2, V2Size);
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if (R != MustAlias)
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// If V2 may alias GEP base pointer, conservatively returns MayAlias.
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// If V2 is known not to alias GEP base pointer, then the two values
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// cannot alias per GEP semantics: "A pointer value formed from a
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// getelementptr instruction is associated with the addresses associated
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// with the first operand of the getelementptr".
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return R;
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// If GetGEPOperands were able to fold to the same must-aliased pointer,
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// do the comparison.
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if (BasePtr1 == BasePtr2) {
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AliasResult GAlias =
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CheckGEPInstructions(BasePtr1->getType(),
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&GEP1Ops[0], GEP1Ops.size(), V1Size,
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BasePtr2->getType(),
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&GEP2Ops[0], GEP2Ops.size(), V2Size);
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if (GAlias != MayAlias)
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return GAlias;
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}
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const Value *GEP1BasePtr =
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DecomposeGEPExpression(GEP1, GEP1BaseOffset, GEP1VariableIndices, TD);
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// If DecomposeGEPExpression isn't able to look all the way through the
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// addressing operation, we must not have TD and this is too complex for us
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// to handle without it.
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if (GEP1BasePtr != UnderlyingV1) {
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assert(TD == 0 &&
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"DecomposeGEPExpression and getUnderlyingObject disagree!");
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return MayAlias;
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}
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}
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// Check to see if these two pointers are related by a getelementptr
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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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// In the two GEP Case, if there is no difference in the offsets of the
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// computed pointers, the resultant pointers are a must alias. This
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// hapens when we have two lexically identical GEP's (for example).
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//
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// FIXME: The check below only looks at the size of one of the pointers, not
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// both, this may cause us to miss things.
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if (V1Size == ~0U || V2Size == ~0U)
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return MayAlias;
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AliasResult R = aliasCheck(UnderlyingV1, ~0U, V2, V2Size);
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if (R != MustAlias)
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// If V2 may alias GEP base pointer, conservatively returns MayAlias.
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// If V2 is known not to alias GEP base pointer, then the two values
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// cannot alias per GEP semantics: "A pointer value formed from a
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// getelementptr instruction is associated with the addresses associated
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// with the first operand of the getelementptr".
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return R;
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int64_t GEP1BaseOffset;
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SmallVector<std::pair<const Value*, uint64_t>, 4> VariableIndices;
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const Value *GEP1BasePtr =
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DecomposeGEPExpression(GEP1, GEP1BaseOffset, VariableIndices, TD);
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// If DecomposeGEPExpression isn't able to look all the way through the
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// addressing operation, we must not have TD and this is too complex for us
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// to handle without it.
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if (GEP1BasePtr != UnderlyingV1) {
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assert(TD == 0 &&
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"DecomposeGEPExpression and getUnderlyingObject disagree!");
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return MayAlias;
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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 (GEP1BaseOffset == 0 && VariableIndices.empty())
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// In the other case, if we have getelementptr <ptr>, 0, 0, 0, 0, ... and V2
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// must aliases the GEP, the end result is a must alias also.
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if (GEP1BaseOffset == 0 && GEP1VariableIndices.empty())
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return MustAlias;
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// If we have a known constant offset, see if this offset is larger than the
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@ -631,9 +618,10 @@ BasicAliasAnalysis::aliasGEP(const GEPOperator *GEP1, unsigned V1Size,
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// multiple of any of our variable indices. This allows us to transform
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// things like &A[i][1] because i has a stride of (e.g.) 8 bytes but the 1
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// provides an offset of 4 bytes (assuming a <= 4 byte access).
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for (unsigned i = 0, e = VariableIndices.size(); i != e && GEP1BaseOffset;++i)
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if (int64_t RemovedOffset = GEP1BaseOffset/VariableIndices[i].second)
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GEP1BaseOffset -= RemovedOffset*VariableIndices[i].second;
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for (unsigned i = 0, e = GEP1VariableIndices.size();
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i != e && GEP1BaseOffset;++i)
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if (int64_t RemovedOffset = GEP1BaseOffset/GEP1VariableIndices[i].second)
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GEP1BaseOffset -= RemovedOffset*GEP1VariableIndices[i].second;
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// If our known offset is bigger than the access size, we know we don't have
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// an alias.
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@ -850,351 +838,5 @@ BasicAliasAnalysis::aliasCheck(const Value *V1, unsigned V1Size,
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return MayAlias;
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}
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// This function is used to determine if the indices of two GEP instructions are
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// equal. V1 and V2 are the indices.
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static bool IndexOperandsEqual(Value *V1, Value *V2) {
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if (V1->getType() == V2->getType())
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return V1 == V2;
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if (Constant *C1 = dyn_cast<Constant>(V1))
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if (Constant *C2 = dyn_cast<Constant>(V2)) {
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// Sign extend the constants to long types, if necessary
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if (C1->getType() != Type::getInt64Ty(C1->getContext()))
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C1 = ConstantExpr::getSExt(C1, Type::getInt64Ty(C1->getContext()));
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if (C2->getType() != Type::getInt64Ty(C1->getContext()))
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C2 = ConstantExpr::getSExt(C2, Type::getInt64Ty(C1->getContext()));
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return C1 == C2;
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}
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return false;
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}
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/// CheckGEPInstructions - Check two GEP instructions with known must-aliasing
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/// base pointers. This checks to see if the index expressions preclude the
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/// pointers from aliasing.
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AliasAnalysis::AliasResult
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BasicAliasAnalysis::CheckGEPInstructions(
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const Type* BasePtr1Ty, Value **GEP1Ops, unsigned NumGEP1Ops, unsigned G1S,
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const Type *BasePtr2Ty, Value **GEP2Ops, unsigned NumGEP2Ops, unsigned G2S) {
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// We currently can't handle the case when the base pointers have different
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// primitive types. Since this is uncommon anyway, we are happy being
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// extremely conservative.
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if (BasePtr1Ty != BasePtr2Ty)
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return MayAlias;
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const PointerType *GEPPointerTy = cast<PointerType>(BasePtr1Ty);
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// Find the (possibly empty) initial sequence of equal values... which are not
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// necessarily constants.
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unsigned NumGEP1Operands = NumGEP1Ops, NumGEP2Operands = NumGEP2Ops;
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unsigned MinOperands = std::min(NumGEP1Operands, NumGEP2Operands);
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unsigned MaxOperands = std::max(NumGEP1Operands, NumGEP2Operands);
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unsigned UnequalOper = 0;
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while (UnequalOper != MinOperands &&
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IndexOperandsEqual(GEP1Ops[UnequalOper], GEP2Ops[UnequalOper])) {
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// Advance through the type as we go...
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++UnequalOper;
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if (const CompositeType *CT = dyn_cast<CompositeType>(BasePtr1Ty))
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BasePtr1Ty = CT->getTypeAtIndex(GEP1Ops[UnequalOper-1]);
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else {
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// If all operands equal each other, then the derived pointers must
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// alias each other...
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BasePtr1Ty = 0;
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assert(UnequalOper == NumGEP1Operands && UnequalOper == NumGEP2Operands &&
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"Ran out of type nesting, but not out of operands?");
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return MustAlias;
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}
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}
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// If we have seen all constant operands, and run out of indexes on one of the
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// getelementptrs, check to see if the tail of the leftover one is all zeros.
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// If so, return mustalias.
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if (UnequalOper == MinOperands) {
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if (NumGEP1Ops < NumGEP2Ops) {
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std::swap(GEP1Ops, GEP2Ops);
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std::swap(NumGEP1Ops, NumGEP2Ops);
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}
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bool AllAreZeros = true;
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for (unsigned i = UnequalOper; i != MaxOperands; ++i)
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if (!isa<Constant>(GEP1Ops[i]) ||
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!cast<Constant>(GEP1Ops[i])->isNullValue()) {
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AllAreZeros = false;
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break;
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}
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if (AllAreZeros) return MustAlias;
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}
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// So now we know that the indexes derived from the base pointers,
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// which are known to alias, are different. We can still determine a
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// no-alias result if there are differing constant pairs in the index
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// chain. For example:
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// A[i][0] != A[j][1] iff (&A[0][1]-&A[0][0] >= std::max(G1S, G2S))
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//
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// We have to be careful here about array accesses. In particular, consider:
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// A[1][0] vs A[0][i]
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// In this case, we don't *know* that the array will be accessed in bounds:
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// the index could even be negative. Because of this, we have to
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// conservatively *give up* and return may alias. We disregard differing
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// array subscripts that are followed by a variable index without going
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// through a struct.
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//
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unsigned SizeMax = std::max(G1S, G2S);
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if (SizeMax == ~0U) return MayAlias; // Avoid frivolous work.
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// Scan for the first operand that is constant and unequal in the
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// two getelementptrs...
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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)
|
||||
|
||||
@ -1,7 +1,9 @@
|
||||
; RUN: opt < %s -aa-eval -print-all-alias-modref-info -disable-output |& grep {MustAlias:.*%R,.*%r}
|
||||
; RUN: opt < %s -gvn -instcombine -S |& FileCheck %s
|
||||
; Make sure that basicaa thinks R and r are must aliases.
|
||||
|
||||
define i32 @test(i8 * %P) {
|
||||
target datalayout = "e-p:32:32:32-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:32:64-f32:32:32-f64:32:64-v64:64:64-v128:128:128-a0:0:64-f80:128:128"
|
||||
|
||||
define i32 @test1(i8 * %P) {
|
||||
entry:
|
||||
%Q = bitcast i8* %P to {i32, i32}*
|
||||
%R = getelementptr {i32, i32}* %Q, i32 0, i32 1
|
||||
@ -13,4 +15,59 @@ entry:
|
||||
|
||||
%t = sub i32 %S, %s
|
||||
ret i32 %t
|
||||
; CHECK: @test1
|
||||
; CHECK: ret i32 0
|
||||
}
|
||||
|
||||
define i32 @test2(i8 * %P) {
|
||||
entry:
|
||||
%Q = bitcast i8* %P to {i32, i32, i32}*
|
||||
%R = getelementptr {i32, i32, i32}* %Q, i32 0, i32 1
|
||||
%S = load i32* %R
|
||||
|
||||
%r = getelementptr {i32, i32, i32}* %Q, i32 0, i32 2
|
||||
store i32 42, i32* %r
|
||||
|
||||
%s = load i32* %R
|
||||
|
||||
%t = sub i32 %S, %s
|
||||
ret i32 %t
|
||||
; CHECK: @test2
|
||||
; CHECK: ret i32 0
|
||||
}
|
||||
|
||||
|
||||
; This was a miscompilation.
|
||||
define i32 @test3({float, {i32, i32, i32}}* %P) {
|
||||
entry:
|
||||
%P2 = getelementptr {float, {i32, i32, i32}}* %P, i32 0, i32 1
|
||||
%R = getelementptr {i32, i32, i32}* %P2, i32 0, i32 1
|
||||
%S = load i32* %R
|
||||
|
||||
%r = getelementptr {i32, i32, i32}* %P2, i32 0, i32 2
|
||||
store i32 42, i32* %r
|
||||
|
||||
%s = load i32* %R
|
||||
|
||||
%t = sub i32 %S, %s
|
||||
ret i32 %t
|
||||
; CHECK: @test3
|
||||
; CHECK: ret i32 0
|
||||
}
|
||||
|
||||
|
||||
;; This is reduced from the SmallPtrSet constructor.
|
||||
%SmallPtrSetImpl = type { i8**, i32, i32, i32, [1 x i8*] }
|
||||
%SmallPtrSet64 = type { %SmallPtrSetImpl, [64 x i8*] }
|
||||
|
||||
define i32 @test4(%SmallPtrSet64* %P) {
|
||||
entry:
|
||||
%tmp2 = getelementptr inbounds %SmallPtrSet64* %P, i64 0, i32 0, i32 1
|
||||
store i32 64, i32* %tmp2, align 8
|
||||
%tmp3 = getelementptr inbounds %SmallPtrSet64* %P, i64 0, i32 0, i32 4, i64 64
|
||||
store i8* null, i8** %tmp3, align 8
|
||||
%tmp4 = load i32* %tmp2, align 8
|
||||
ret i32 %tmp4
|
||||
; CHECK: @test4
|
||||
; CHECK: ret i32 64
|
||||
}
|
||||
|
||||
Loading…
Reference in New Issue
Block a user