[llvm] r246502 - [BasicAA] Fix the handling of sext and zext in the analysis of GEPs.
Quentin Colombet via llvm-commits
llvm-commits at lists.llvm.org
Mon Aug 31 15:40:21 PDT 2015
Hi Hans,
Following Hal's recommendation in D11847, I think we want to pull that into 3.7.
Thanks,
-Quentin
> On Aug 31, 2015, at 3:32 PM, Quentin Colombet via llvm-commits <llvm-commits at lists.llvm.org> wrote:
>
> Author: qcolombet
> Date: Mon Aug 31 17:32:47 2015
> New Revision: 246502
>
> URL: http://llvm.org/viewvc/llvm-project?rev=246502&view=rev
> Log:
> [BasicAA] Fix the handling of sext and zext in the analysis of GEPs.
> Hopefully this will end the GEPs saga!
>
> This commit reverts r245394, i.e., it reapplies r221876 while incorporating the
> fixes from D11847.
> r221876 was not reapplied alone because it was not safe and D11847 was not
> applied alone because it needs r221876 to produce correct results.
>
> This should fix PR24596.
>
> Original commit message for r221876:
> Let's try this again...
>
> This reverts r219432, plus a bug fix.
>
> Description of the bug in r219432 (by Nick):
>
> The bug was using AllPositive to break out of the loop; if the loop break
> condition i != e is changed to i != e && AllPositive then the
> test_modulo_analysis_with_global test I've added will fail as the Modulo will
> be calculated incorrectly (as the last loop iteration is skipped, so Modulo
> isn't updated with its Scale).
>
> Nick also adds this comment:
>
> ComputeSignBit is safe to use in loops as it takes into account phi nodes, and
> the == EK_ZeroEx check is safe in loops as, no matter how the variable changes
> between iterations, zero-extensions will always guarantee a zero sign bit. The
> isValueEqualInPotentialCycles check is therefore definitely not needed as all
> the variable analysis holds no matter how the variables change between loop
> iterations.
>
> And this patch also adds another enhancement to GetLinearExpression - basically
> to convert ConstantInts to Offsets (see test_const_eval and
> test_const_eval_scaled for the situations this improves).
>
> Original commit message:
>
> This reverts r218944, which reverted r218714, plus a bug fix.
>
> Description of the bug in r218714 (by Nick):
>
> The original patch forgot to check if the Scale in VariableGEPIndex flipped the
> sign of the variable. The BasicAA pass iterates over the instructions in the
> order they appear in the function, and so BasicAliasAnalysis::aliasGEP is
> called with the variable it first comes across as parameter GEP1. Adding a
> %reorder label puts the definition of %a after %b so aliasGEP is called with %b
> as the first parameter and %a as the second. aliasGEP later calculates that %a
> == %b + 1 - %idxprom where %idxprom >= 0 (if %a was passed as the first
> parameter it would calculate %b == %a - 1 + %idxprom where %idxprom >= 0) -
> ignoring that %idxprom is scaled by -1 here lead the patch to incorrectly
> conclude that %a > %b.
>
> Revised patch by Nick White, thanks! Thanks to Lang to isolating the bug.
> Slightly modified by me to add an early exit from the loop and avoid
> unnecessary, but expensive, function calls.
>
> Original commit message:
>
> Two related things:
>
> 1. Fixes a bug when calculating the offset in GetLinearExpression. The code
> previously used zext to extend the offset, so negative offsets were converted
> to large positive ones.
>
> 2. Enhance aliasGEP to deduce that, if the difference between two GEP
> allocations is positive and all the variables that govern the offset are also
> positive (i.e. the offset is strictly after the higher base pointer), then
> locations that fit in the gap between the two base pointers are NoAlias.
>
> Patch by Nick White!
>
> Message from D11847:
> Un-revert of r241981 and fix for PR23626. The 'Or' case of GetLinearExpression
> delegates to 'Add' if possible, and if not it returns an Opaque value.
> Unfortunately the Scale and Offsets weren't being set (and so defaulted to 0) -
> and a scale of zero effectively removes the variable from the GEP instruction.
> This meant that BasicAA would return MustAliases when it should have been
> returning PartialAliases (and PR23626 was an example of the GVN pass using an
> incorrect MustAlias to merge loads from what should have been different
> pointers).
>
> Differential Revision: http://reviews.llvm.org/D11847
> Patch by Nick White <n.j.white at gmail.com>!
>
>
> Added:
> llvm/trunk/test/Analysis/BasicAA/bug.23540.ll
> llvm/trunk/test/Analysis/BasicAA/bug.23626.ll
> llvm/trunk/test/Analysis/BasicAA/q.bad.ll
> llvm/trunk/test/Analysis/BasicAA/zext.ll
> - copied, changed from r245393, llvm/trunk/test/Analysis/BasicAA/zext.ll
> Modified:
> llvm/trunk/include/llvm/Analysis/BasicAliasAnalysis.h
> llvm/trunk/lib/Analysis/BasicAliasAnalysis.cpp
> llvm/trunk/test/Analysis/BasicAA/phi-aa.ll
>
> Modified: llvm/trunk/include/llvm/Analysis/BasicAliasAnalysis.h
> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/include/llvm/Analysis/BasicAliasAnalysis.h?rev=246502&r1=246501&r2=246502&view=diff
> ==============================================================================
> --- llvm/trunk/include/llvm/Analysis/BasicAliasAnalysis.h (original)
> +++ llvm/trunk/include/llvm/Analysis/BasicAliasAnalysis.h Mon Aug 31 17:32:47 2015
> @@ -109,16 +109,25 @@ struct BasicAliasAnalysis : public Immut
> }
>
> private:
> - enum ExtensionKind { EK_NotExtended, EK_SignExt, EK_ZeroExt };
> -
> + // A linear transformation of a Value; this class represents ZExt(SExt(V,
> + // SExtBits), ZExtBits) * Scale + Offset.
> struct VariableGEPIndex {
> +
> + // An opaque Value - we can't decompose this further.
> const Value *V;
> - ExtensionKind Extension;
> +
> + // We need to track what extensions we've done as we consider the same Value
> + // with different extensions as different variables in a GEP's linear
> + // expression;
> + // e.g.: if V == -1, then sext(x) != zext(x).
> + unsigned ZExtBits;
> + unsigned SExtBits;
> +
> int64_t Scale;
>
> bool operator==(const VariableGEPIndex &Other) const {
> - return V == Other.V && Extension == Other.Extension &&
> - Scale == Other.Scale;
> + return V == Other.V && ZExtBits == Other.ZExtBits &&
> + SExtBits == Other.SExtBits && Scale == Other.Scale;
> }
>
> bool operator!=(const VariableGEPIndex &Other) const {
> @@ -150,16 +159,30 @@ private:
> /// Tracks instructions visited by pointsToConstantMemory.
> SmallPtrSet<const Value *, 16> Visited;
>
> - static Value *GetLinearExpression(Value *V, APInt &Scale, APInt &Offset,
> - ExtensionKind &Extension,
> - const DataLayout &DL, unsigned Depth,
> - AssumptionCache *AC, DominatorTree *DT);
> + static const Value *
> + GetLinearExpression(const Value *V, APInt &Scale, APInt &Offset,
> + unsigned &ZExtBits, unsigned &SExtBits,
> + const DataLayout &DL, unsigned Depth, AssumptionCache *AC,
> + DominatorTree *DT, bool &NSW, bool &NUW);
>
> static const Value *
> DecomposeGEPExpression(const Value *V, int64_t &BaseOffs,
> SmallVectorImpl<VariableGEPIndex> &VarIndices,
> bool &MaxLookupReached, const DataLayout &DL,
> AssumptionCache *AC, DominatorTree *DT);
> + /// \brief A Heuristic for aliasGEP that searches for a constant offset
> + /// between the variables.
> + ///
> + /// GetLinearExpression has some limitations, as generally zext(%x + 1)
> + /// != zext(%x) + zext(1) if the arithmetic overflows. GetLinearExpression
> + /// will therefore conservatively refuse to decompose these expressions.
> + /// However, we know that, for all %x, zext(%x) != zext(%x + 1), even if
> + /// the addition overflows.
> + bool
> + constantOffsetHeuristic(const SmallVectorImpl<VariableGEPIndex> &VarIndices,
> + uint64_t V1Size, uint64_t V2Size, int64_t BaseOffset,
> + const DataLayout *DL, AssumptionCache *AC,
> + DominatorTree *DT);
>
> bool isValueEqualInPotentialCycles(const Value *V1, const Value *V2);
>
>
> Modified: llvm/trunk/lib/Analysis/BasicAliasAnalysis.cpp
> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Analysis/BasicAliasAnalysis.cpp?rev=246502&r1=246501&r2=246502&view=diff
> ==============================================================================
> --- llvm/trunk/lib/Analysis/BasicAliasAnalysis.cpp (original)
> +++ llvm/trunk/lib/Analysis/BasicAliasAnalysis.cpp Mon Aug 31 17:32:47 2015
> @@ -177,10 +177,10 @@ static bool isObjectSize(const Value *V,
> ///
> /// Note that this looks through extends, so the high bits may not be
> /// represented in the result.
> -/*static*/ Value *BasicAliasAnalysis::GetLinearExpression(
> - Value *V, APInt &Scale, APInt &Offset, ExtensionKind &Extension,
> - const DataLayout &DL, unsigned Depth, AssumptionCache *AC,
> - DominatorTree *DT) {
> +/*static*/ const Value *BasicAliasAnalysis::GetLinearExpression(
> + const Value *V, APInt &Scale, APInt &Offset, unsigned &ZExtBits,
> + unsigned &SExtBits, const DataLayout &DL, unsigned Depth,
> + AssumptionCache *AC, DominatorTree *DT, bool &NSW, bool &NUW) {
> assert(V->getType()->isIntegerTy() && "Not an integer value");
>
> // Limit our recursion depth.
> @@ -190,55 +190,125 @@ static bool isObjectSize(const Value *V,
> return V;
> }
>
> - if (BinaryOperator *BOp = dyn_cast<BinaryOperator>(V)) {
> + if (const ConstantInt *Const = dyn_cast<ConstantInt>(V)) {
> + // if it's a constant, just convert it to an offset and remove the variable.
> + // If we've been called recursively the Offset bit width will be greater
> + // than the constant's (the Offset's always as wide as the outermost call),
> + // so we'll zext here and process any extension in the isa<SExtInst> &
> + // isa<ZExtInst> cases below.
> + Offset += Const->getValue().zextOrSelf(Offset.getBitWidth());
> + assert(Scale == 0 && "Constant values don't have a scale");
> + return V;
> + }
> +
> + if (const BinaryOperator *BOp = dyn_cast<BinaryOperator>(V)) {
> if (ConstantInt *RHSC = dyn_cast<ConstantInt>(BOp->getOperand(1))) {
> +
> + // If we've been called recursively then Offset and Scale will be wider
> + // that the BOp operands. We'll always zext it here as we'll process sign
> + // extensions below (see the isa<SExtInst> / isa<ZExtInst> cases).
> + APInt RHS = RHSC->getValue().zextOrSelf(Offset.getBitWidth());
> +
> switch (BOp->getOpcode()) {
> default:
> - break;
> + // We don't understand this instruction, so we can't decompose it any
> + // further.
> + Scale = 1;
> + Offset = 0;
> + return V;
> case Instruction::Or:
> // X|C == X+C if all the bits in C are unset in X. Otherwise we can't
> // analyze it.
> if (!MaskedValueIsZero(BOp->getOperand(0), RHSC->getValue(), DL, 0, AC,
> - BOp, DT))
> - break;
> + BOp, DT)) {
> + Scale = 1;
> + Offset = 0;
> + return V;
> + }
> // FALL THROUGH.
> case Instruction::Add:
> - V = GetLinearExpression(BOp->getOperand(0), Scale, Offset, Extension,
> - DL, Depth + 1, AC, DT);
> - Offset += RHSC->getValue();
> - return V;
> + V = GetLinearExpression(BOp->getOperand(0), Scale, Offset, ZExtBits,
> + SExtBits, DL, Depth + 1, AC, DT, NSW, NUW);
> + Offset += RHS;
> + break;
> + case Instruction::Sub:
> + V = GetLinearExpression(BOp->getOperand(0), Scale, Offset, ZExtBits,
> + SExtBits, DL, Depth + 1, AC, DT, NSW, NUW);
> + Offset -= RHS;
> + break;
> case Instruction::Mul:
> - V = GetLinearExpression(BOp->getOperand(0), Scale, Offset, Extension,
> - DL, Depth + 1, AC, DT);
> - Offset *= RHSC->getValue();
> - Scale *= RHSC->getValue();
> - return V;
> + V = GetLinearExpression(BOp->getOperand(0), Scale, Offset, ZExtBits,
> + SExtBits, DL, Depth + 1, AC, DT, NSW, NUW);
> + Offset *= RHS;
> + Scale *= RHS;
> + break;
> case Instruction::Shl:
> - V = GetLinearExpression(BOp->getOperand(0), Scale, Offset, Extension,
> - DL, Depth + 1, AC, DT);
> - Offset <<= RHSC->getValue().getLimitedValue();
> - Scale <<= RHSC->getValue().getLimitedValue();
> + V = GetLinearExpression(BOp->getOperand(0), Scale, Offset, ZExtBits,
> + SExtBits, DL, Depth + 1, AC, DT, NSW, NUW);
> + Offset <<= RHS.getLimitedValue();
> + Scale <<= RHS.getLimitedValue();
> + // the semantics of nsw and nuw for left shifts don't match those of
> + // multiplications, so we won't propagate them.
> + NSW = NUW = false;
> return V;
> }
> +
> + if (isa<OverflowingBinaryOperator>(BOp)) {
> + NUW &= BOp->hasNoUnsignedWrap();
> + NSW &= BOp->hasNoSignedWrap();
> + }
> + return V;
> }
> }
>
> // Since GEP indices are sign extended anyway, we don't care about the high
> // bits of a sign or zero extended value - just scales and offsets. The
> // extensions have to be consistent though.
> - if ((isa<SExtInst>(V) && Extension != EK_ZeroExt) ||
> - (isa<ZExtInst>(V) && Extension != EK_SignExt)) {
> + if (isa<SExtInst>(V) || isa<ZExtInst>(V)) {
> Value *CastOp = cast<CastInst>(V)->getOperand(0);
> - unsigned OldWidth = Scale.getBitWidth();
> + unsigned NewWidth = V->getType()->getPrimitiveSizeInBits();
> unsigned SmallWidth = CastOp->getType()->getPrimitiveSizeInBits();
> - Scale = Scale.trunc(SmallWidth);
> - Offset = Offset.trunc(SmallWidth);
> - Extension = isa<SExtInst>(V) ? EK_SignExt : EK_ZeroExt;
> -
> - Value *Result = GetLinearExpression(CastOp, Scale, Offset, Extension, DL,
> - Depth + 1, AC, DT);
> - Scale = Scale.zext(OldWidth);
> - Offset = Offset.zext(OldWidth);
> + unsigned OldZExtBits = ZExtBits, OldSExtBits = SExtBits;
> + const Value *Result =
> + GetLinearExpression(CastOp, Scale, Offset, ZExtBits, SExtBits, DL,
> + Depth + 1, AC, DT, NSW, NUW);
> +
> + // zext(zext(%x)) == zext(%x), and similiarly for sext; we'll handle this
> + // by just incrementing the number of bits we've extended by.
> + unsigned ExtendedBy = NewWidth - SmallWidth;
> +
> + if (isa<SExtInst>(V) && ZExtBits == 0) {
> + // sext(sext(%x, a), b) == sext(%x, a + b)
> +
> + if (NSW) {
> + // We haven't sign-wrapped, so it's valid to decompose sext(%x + c)
> + // into sext(%x) + sext(c). We'll sext the Offset ourselves:
> + unsigned OldWidth = Offset.getBitWidth();
> + Offset = Offset.trunc(SmallWidth).sext(NewWidth).zextOrSelf(OldWidth);
> + } else {
> + // We may have signed-wrapped, so don't decompose sext(%x + c) into
> + // sext(%x) + sext(c)
> + Scale = 1;
> + Offset = 0;
> + Result = CastOp;
> + ZExtBits = OldZExtBits;
> + SExtBits = OldSExtBits;
> + }
> + SExtBits += ExtendedBy;
> + } else {
> + // sext(zext(%x, a), b) = zext(zext(%x, a), b) = zext(%x, a + b)
> +
> + if (!NUW) {
> + // We may have unsigned-wrapped, so don't decompose zext(%x + c) into
> + // zext(%x) + zext(c)
> + Scale = 1;
> + Offset = 0;
> + Result = CastOp;
> + ZExtBits = OldZExtBits;
> + SExtBits = OldSExtBits;
> + }
> + ZExtBits += ExtendedBy;
> + }
>
> return Result;
> }
> @@ -318,7 +388,7 @@ static bool isObjectSize(const Value *V,
> gep_type_iterator GTI = gep_type_begin(GEPOp);
> for (User::const_op_iterator I = GEPOp->op_begin() + 1, E = GEPOp->op_end();
> I != E; ++I) {
> - Value *Index = *I;
> + const Value *Index = *I;
> // Compute the (potentially symbolic) offset in bytes for this index.
> if (StructType *STy = dyn_cast<StructType>(*GTI++)) {
> // For a struct, add the member offset.
> @@ -331,7 +401,7 @@ static bool isObjectSize(const Value *V,
> }
>
> // For an array/pointer, add the element offset, explicitly scaled.
> - if (ConstantInt *CIdx = dyn_cast<ConstantInt>(Index)) {
> + if (const ConstantInt *CIdx = dyn_cast<ConstantInt>(Index)) {
> if (CIdx->isZero())
> continue;
> BaseOffs += DL.getTypeAllocSize(*GTI) * CIdx->getSExtValue();
> @@ -339,18 +409,20 @@ static bool isObjectSize(const Value *V,
> }
>
> uint64_t Scale = DL.getTypeAllocSize(*GTI);
> - ExtensionKind Extension = EK_NotExtended;
> + unsigned ZExtBits = 0, SExtBits = 0;
>
> // If the integer type is smaller than the pointer size, it is implicitly
> // sign extended to pointer size.
> unsigned Width = Index->getType()->getIntegerBitWidth();
> - if (DL.getPointerSizeInBits(AS) > Width)
> - Extension = EK_SignExt;
> + unsigned PointerSize = DL.getPointerSizeInBits(AS);
> + if (PointerSize > Width)
> + SExtBits += PointerSize - Width;
>
> // Use GetLinearExpression to decompose the index into a C1*V+C2 form.
> APInt IndexScale(Width, 0), IndexOffset(Width, 0);
> - Index = GetLinearExpression(Index, IndexScale, IndexOffset, Extension, DL,
> - 0, AC, DT);
> + bool NSW = true, NUW = true;
> + Index = GetLinearExpression(Index, IndexScale, IndexOffset, ZExtBits,
> + SExtBits, DL, 0, AC, DT, NSW, NUW);
>
> // The GEP index scale ("Scale") scales C1*V+C2, yielding (C1*V+C2)*Scale.
> // This gives us an aggregate computation of (C1*Scale)*V + C2*Scale.
> @@ -362,7 +434,8 @@ static bool isObjectSize(const Value *V,
> // A[x][x] -> x*16 + x*4 -> x*20
> // This also ensures that 'x' only appears in the index list once.
> for (unsigned i = 0, e = VarIndices.size(); i != e; ++i) {
> - if (VarIndices[i].V == Index && VarIndices[i].Extension == Extension) {
> + if (VarIndices[i].V == Index && VarIndices[i].ZExtBits == ZExtBits &&
> + VarIndices[i].SExtBits == SExtBits) {
> Scale += VarIndices[i].Scale;
> VarIndices.erase(VarIndices.begin() + i);
> break;
> @@ -371,13 +444,13 @@ static bool isObjectSize(const Value *V,
>
> // Make sure that we have a scale that makes sense for this target's
> // pointer size.
> - if (unsigned ShiftBits = 64 - DL.getPointerSizeInBits(AS)) {
> + if (unsigned ShiftBits = 64 - PointerSize) {
> Scale <<= ShiftBits;
> Scale = (int64_t)Scale >> ShiftBits;
> }
>
> if (Scale) {
> - VariableGEPIndex Entry = {Index, Extension,
> + VariableGEPIndex Entry = {Index, ZExtBits, SExtBits,
> static_cast<int64_t>(Scale)};
> VarIndices.push_back(Entry);
> }
> @@ -948,12 +1021,42 @@ AliasResult BasicAliasAnalysis::aliasGEP
> }
> }
>
> - // Try to distinguish something like &A[i][1] against &A[42][0].
> - // Grab the least significant bit set in any of the scales.
> if (!GEP1VariableIndices.empty()) {
> uint64_t Modulo = 0;
> - for (unsigned i = 0, e = GEP1VariableIndices.size(); i != e; ++i)
> + bool AllPositive = true;
> + for (unsigned i = 0, e = GEP1VariableIndices.size(); i != e; ++i) {
> +
> + // Try to distinguish something like &A[i][1] against &A[42][0].
> + // Grab the least significant bit set in any of the scales. We
> + // don't need std::abs here (even if the scale's negative) as we'll
> + // be ^'ing Modulo with itself later.
> Modulo |= (uint64_t)GEP1VariableIndices[i].Scale;
> +
> + if (AllPositive) {
> + // If the Value could change between cycles, then any reasoning about
> + // the Value this cycle may not hold in the next cycle. We'll just
> + // give up if we can't determine conditions that hold for every cycle:
> + const Value *V = GEP1VariableIndices[i].V;
> +
> + bool SignKnownZero, SignKnownOne;
> + ComputeSignBit(const_cast<Value *>(V), SignKnownZero, SignKnownOne, *DL,
> + 0, AC1, nullptr, DT);
> +
> + // Zero-extension widens the variable, and so forces the sign
> + // bit to zero.
> + bool IsZExt = GEP1VariableIndices[i].ZExtBits > 0 || isa<ZExtInst>(V);
> + SignKnownZero |= IsZExt;
> + SignKnownOne &= !IsZExt;
> +
> + // If the variable begins with a zero then we know it's
> + // positive, regardless of whether the value is signed or
> + // unsigned.
> + int64_t Scale = GEP1VariableIndices[i].Scale;
> + AllPositive =
> + (SignKnownZero && Scale >= 0) || (SignKnownOne && Scale < 0);
> + }
> + }
> +
> Modulo = Modulo ^ (Modulo & (Modulo - 1));
>
> // We can compute the difference between the two addresses
> @@ -964,6 +1067,16 @@ AliasResult BasicAliasAnalysis::aliasGEP
> V2Size != MemoryLocation::UnknownSize && ModOffset >= V2Size &&
> V1Size <= Modulo - ModOffset)
> return NoAlias;
> +
> + // If we know all the variables are positive, then GEP1 >= GEP1BasePtr.
> + // If GEP1BasePtr > V2 (GEP1BaseOffset > 0) then we know the pointers
> + // don't alias if V2Size can fit in the gap between V2 and GEP1BasePtr.
> + if (AllPositive && GEP1BaseOffset > 0 && V2Size <= (uint64_t)GEP1BaseOffset)
> + return NoAlias;
> +
> + if (constantOffsetHeuristic(GEP1VariableIndices, V1Size, V2Size,
> + GEP1BaseOffset, DL, AC1, DT))
> + return NoAlias;
> }
>
> // Statically, we can see that the base objects are the same, but the
> @@ -1333,14 +1446,14 @@ void BasicAliasAnalysis::GetIndexDiffere
>
> for (unsigned i = 0, e = Src.size(); i != e; ++i) {
> const Value *V = Src[i].V;
> - ExtensionKind Extension = Src[i].Extension;
> + unsigned ZExtBits = Src[i].ZExtBits, SExtBits = Src[i].SExtBits;
> int64_t Scale = Src[i].Scale;
>
> // 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 (!isValueEqualInPotentialCycles(Dest[j].V, V) ||
> - Dest[j].Extension != Extension)
> + Dest[j].ZExtBits != ZExtBits || Dest[j].SExtBits != SExtBits)
> continue;
>
> // If we found it, subtract off Scale V's from the entry in Dest. If it
> @@ -1355,8 +1468,62 @@ void BasicAliasAnalysis::GetIndexDiffere
>
> // If we didn't consume this entry, add it to the end of the Dest list.
> if (Scale) {
> - VariableGEPIndex Entry = {V, Extension, -Scale};
> + VariableGEPIndex Entry = {V, ZExtBits, SExtBits, -Scale};
> Dest.push_back(Entry);
> }
> }
> }
> +
> +bool BasicAliasAnalysis::constantOffsetHeuristic(
> + const SmallVectorImpl<VariableGEPIndex> &VarIndices, uint64_t V1Size,
> + uint64_t V2Size, int64_t BaseOffset, const DataLayout *DL,
> + AssumptionCache *AC, DominatorTree *DT) {
> + if (VarIndices.size() != 2 || V1Size == MemoryLocation::UnknownSize ||
> + V2Size == MemoryLocation::UnknownSize || !DL)
> + return false;
> +
> + const VariableGEPIndex &Var0 = VarIndices[0], &Var1 = VarIndices[1];
> +
> + if (Var0.ZExtBits != Var1.ZExtBits || Var0.SExtBits != Var1.SExtBits ||
> + Var0.Scale != -Var1.Scale)
> + return false;
> +
> + unsigned Width = Var1.V->getType()->getIntegerBitWidth();
> +
> + // We'll strip off the Extensions of Var0 and Var1 and do another round
> + // of GetLinearExpression decomposition. In the example above, if Var0
> + // is zext(%x + 1) we should get V1 == %x and V1Offset == 1.
> +
> + APInt V0Scale(Width, 0), V0Offset(Width, 0), V1Scale(Width, 0),
> + V1Offset(Width, 0);
> + bool NSW = true, NUW = true;
> + unsigned V0ZExtBits = 0, V0SExtBits = 0, V1ZExtBits = 0, V1SExtBits = 0;
> + const Value *V0 = GetLinearExpression(Var0.V, V0Scale, V0Offset, V0ZExtBits,
> + V0SExtBits, *DL, 0, AC, DT, NSW, NUW);
> + NSW = true, NUW = true;
> + const Value *V1 = GetLinearExpression(Var1.V, V1Scale, V1Offset, V1ZExtBits,
> + V1SExtBits, *DL, 0, AC, DT, NSW, NUW);
> +
> + if (V0Scale != V1Scale || V0ZExtBits != V1ZExtBits ||
> + V0SExtBits != V1SExtBits || !isValueEqualInPotentialCycles(V0, V1))
> + return false;
> +
> + // We have a hit - Var0 and Var1 only differ by a constant offset!
> +
> + // If we've been sext'ed then zext'd the maximum difference between Var0 and
> + // Var1 is possible to calculate, but we're just interested in the absolute
> + // minumum difference between the two. The minimum distance may occur due to
> + // wrapping; consider "add i3 %i, 5": if %i == 7 then 7 + 5 mod 8 == 4, and so
> + // the minimum distance between %i and %i + 5 is 3.
> + APInt MinDiff = V0Offset - V1Offset,
> + Wrapped = APInt::getMaxValue(Width) - MinDiff + APInt(Width, 1);
> + MinDiff = APIntOps::umin(MinDiff, Wrapped);
> + uint64_t MinDiffBytes = MinDiff.getZExtValue() * std::abs(Var0.Scale);
> +
> + // We can't definitely say whether GEP1 is before or after V2 due to wrapping
> + // arithmetic (i.e. for some values of GEP1 and V2 GEP1 < V2, and for other
> + // values GEP1 > V2). We'll therefore only declare NoAlias if both V1Size and
> + // V2Size can fit in the MinDiffBytes gap.
> + return V1Size + std::abs(BaseOffset) <= MinDiffBytes &&
> + V2Size + std::abs(BaseOffset) <= MinDiffBytes;
> +}
>
> Added: llvm/trunk/test/Analysis/BasicAA/bug.23540.ll
> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Analysis/BasicAA/bug.23540.ll?rev=246502&view=auto
> ==============================================================================
> --- llvm/trunk/test/Analysis/BasicAA/bug.23540.ll (added)
> +++ llvm/trunk/test/Analysis/BasicAA/bug.23540.ll Mon Aug 31 17:32:47 2015
> @@ -0,0 +1,17 @@
> +; RUN: opt < %s -basicaa -aa-eval -print-all-alias-modref-info -disable-output 2>&1 | FileCheck %s
> +target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
> +target triple = "x86_64-unknown-linux-gnu"
> +
> + at c = external global i32
> +
> +; CHECK-LABEL: f
> +; CHECK: PartialAlias: i32* %arrayidx, i32* %arrayidx6
> +define void @f() {
> + %idxprom = zext i32 undef to i64
> + %add4 = add i32 0, 1
> + %idxprom5 = zext i32 %add4 to i64
> + %arrayidx6 = getelementptr inbounds i32, i32* @c, i64 %idxprom5
> + %arrayidx = getelementptr inbounds i32, i32* @c, i64 %idxprom
> + ret void
> +}
> +
>
> Added: llvm/trunk/test/Analysis/BasicAA/bug.23626.ll
> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Analysis/BasicAA/bug.23626.ll?rev=246502&view=auto
> ==============================================================================
> --- llvm/trunk/test/Analysis/BasicAA/bug.23626.ll (added)
> +++ llvm/trunk/test/Analysis/BasicAA/bug.23626.ll Mon Aug 31 17:32:47 2015
> @@ -0,0 +1,31 @@
> +; RUN: opt < %s -basicaa -aa-eval -print-all-alias-modref-info -disable-output 2>&1 | FileCheck %s
> +target datalayout = "e-m:o-i64:64-f80:128-n8:16:32:64-S128"
> +target triple = "x86_64-apple-darwin13.4.0"
> +
> +; CHECK-LABEL: compute1
> +; CHECK: PartialAlias: i32* %arrayidx8, i32* %out
> +; CHECK: PartialAlias: i32* %arrayidx11, i32* %out
> +; CHECK: PartialAlias: i32* %arrayidx11, i32* %arrayidx8
> +; CHECK: PartialAlias: i32* %arrayidx14, i32* %out
> +; CHECK: PartialAlias: i32* %arrayidx14, i32* %arrayidx8
> +; CHECK: PartialAlias: i32* %arrayidx11, i32* %arrayidx14
> +define void @compute1(i32 %num.0.lcssa, i32* %out) {
> + %idxprom = zext i32 %num.0.lcssa to i64
> + %arrayidx8 = getelementptr inbounds i32, i32* %out, i64 %idxprom
> + %add9 = or i32 %num.0.lcssa, 1
> + %idxprom10 = zext i32 %add9 to i64
> + %arrayidx11 = getelementptr inbounds i32, i32* %out, i64 %idxprom10
> + %add12 = or i32 %num.0.lcssa, 2
> + %idxprom13 = zext i32 %add12 to i64
> + %arrayidx14 = getelementptr inbounds i32, i32* %out, i64 %idxprom13
> + ret void
> +}
> +
> +; CHECK-LABEL: compute2
> +; CHECK: PartialAlias: i32* %arrayidx11, i32* %out.addr
> +define void @compute2(i32 %num, i32* %out.addr) {
> + %add9 = add i32 %num, 1
> + %idxprom10 = zext i32 %add9 to i64
> + %arrayidx11 = getelementptr inbounds i32, i32* %out.addr, i64 %idxprom10
> + ret void
> +}
>
> Modified: llvm/trunk/test/Analysis/BasicAA/phi-aa.ll
> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Analysis/BasicAA/phi-aa.ll?rev=246502&r1=246501&r2=246502&view=diff
> ==============================================================================
> --- llvm/trunk/test/Analysis/BasicAA/phi-aa.ll (original)
> +++ llvm/trunk/test/Analysis/BasicAA/phi-aa.ll Mon Aug 31 17:32:47 2015
> @@ -39,6 +39,7 @@ return:
>
> ; CHECK-LABEL: pr18068
> ; CHECK: MayAlias: i32* %0, i32* %arrayidx5
> +; CHECK: NoAlias: i32* %arrayidx13, i32* %arrayidx5
>
> define i32 @pr18068(i32* %jj7, i32* %j) {
> entry:
>
> Added: llvm/trunk/test/Analysis/BasicAA/q.bad.ll
> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Analysis/BasicAA/q.bad.ll?rev=246502&view=auto
> ==============================================================================
> --- llvm/trunk/test/Analysis/BasicAA/q.bad.ll (added)
> +++ llvm/trunk/test/Analysis/BasicAA/q.bad.ll Mon Aug 31 17:32:47 2015
> @@ -0,0 +1,180 @@
> +; RUN: opt < %s -basicaa -aa-eval -print-all-alias-modref-info -disable-output 2>&1 | FileCheck %s
> +target datalayout = "e-m:e-p:32:32-i64:64-v128:64:128-a:0:32-n32-S64"
> +target triple = "thumbv7--linux-gnueabi"
> +
> +; CHECK-LABEL: test_zext_sext_amounts255
> +; CHECK: NoAlias: i8* %a, i8* %b
> +define void @test_zext_sext_amounts255(i8* %mem) {
> + %sext.1 = sext i8 255 to i16
> + %sext.zext.1 = zext i16 %sext.1 to i64
> + %sext.2 = sext i8 255 to i32
> + %sext.zext.2 = zext i32 %sext.2 to i64
> + %a = getelementptr inbounds i8, i8* %mem, i64 %sext.zext.1
> + %b = getelementptr inbounds i8, i8* %mem, i64 %sext.zext.2
> + ret void
> +}
> +
> +; CHECK-LABEL: test_zext_sext_amounts
> +; CHECK: PartialAlias: i8* %a, i8* %b
> +; %a and %b only PartialAlias as, although they're both zext(sext(%num)) they'll extend the sign by a different
> +; number of bits before zext-ing the remainder.
> +define void @test_zext_sext_amounts(i8* %mem, i8 %num) {
> + %sext.1 = sext i8 %num to i16
> + %sext.zext.1 = zext i16 %sext.1 to i64
> + %sext.2 = sext i8 %num to i32
> + %sext.zext.2 = zext i32 %sext.2 to i64
> + %a = getelementptr inbounds i8, i8* %mem, i64 %sext.zext.1
> + %b = getelementptr inbounds i8, i8* %mem, i64 %sext.zext.2
> + ret void
> +}
> +
> +; CHECK-LABEL: based_on_pr18068
> +; CHECK: NoAlias: i8* %a, i8* %b
> +; CHECK: NoAlias: i8* %a, i8* %c
> +define void @based_on_pr18068(i32 %loaded, i8* %mem) {
> + %loaded.64 = zext i32 %loaded to i64
> + %add1 = add i32 %loaded, -1 ; unsigned wraps unless %loaded == 0
> + %add1.64 = zext i32 %add1 to i64 ; is zext(%loaded) always != zext(%loaded - 1)? Yes -> NoAlias
> + %sub1 = sub i32 %loaded, 1 ; unsigned wraps iff %loaded == 0
> + %sub1.64 = zext i32 %sub1 to i64 ; is zext(%loaded) always != zext(%loaded - 1)? Yes -> NoAlias
> + %a = getelementptr inbounds i8, i8* %mem, i64 %loaded.64
> + %b = getelementptr inbounds i8, i8* %mem, i64 %add1.64
> + %c = getelementptr inbounds i8, i8* %mem, i64 %sub1.64
> + ret void
> +}
> +
> +; CHECK-LABEL: test_path_dependence
> +; CHECK: PartialAlias: i8* %a, i8* %b
> +; CHECK: MustAlias: i8* %a, i8* %c
> +; CHECK: PartialAlias: i8* %a, i8* %d
> +define void @test_path_dependence(i32 %p, i8* %mem) {
> + %p.minus1 = add i32 %p, -1 ; this will always unsigned-wrap, unless %p == 0
> + %p.minus1.64 = zext i32 %p.minus1 to i64
> + %p.64.again = add i64 %p.minus1.64, 1 ; either %p (if we wrapped) or 4294967296 (if we didn't)
> +
> + %p.nsw.nuw.minus1 = sub nsw nuw i32 %p, 1 ; as nuw we know %p >= 1, and as nsw %p <= 2147483647
> + %p.nsw.nuw.minus1.64 = zext i32 %p.nsw.nuw.minus1 to i64
> + %p.nsw.nuw.64.again = add nsw nuw i64 %p.nsw.nuw.minus1.64, 1 ; ...so always exactly %p
> +
> + %p.nsw.minus1 = sub nsw i32 %p, 1 ; only nsw, so can only guarantee %p != 0x10000000
> + %p.nsw.minus1.64 = zext i32 %p.nsw.minus1 to i64 ; when %p > 0x10000000 (ie <= 0 as a signed number) then the zext will make this a huge positive number
> + %p.nsw.64.again = add nsw i64 %p.nsw.minus1.64, 1 ; ...and so this is very much != %p
> +
> + %p.64 = zext i32 %p to i64
> + %a = getelementptr inbounds i8, i8* %mem, i64 %p.64
> + %b = getelementptr inbounds i8, i8* %mem, i64 %p.64.again
> + %c = getelementptr inbounds i8, i8* %mem, i64 %p.nsw.nuw.64.again
> + %d = getelementptr inbounds i8, i8* %mem, i64 %p.nsw.64.again
> + ret void
> +}
> +
> +; CHECK-LABEL: test_zext_sext_255
> +; CHECK: NoAlias: i8* %a, i8* %b
> +define void @test_zext_sext_255(i8* %mem) {
> + %zext.255 = zext i8 255 to i16 ; 0x00FF
> + %sext.255 = sext i8 255 to i16 ; 0xFFFF
> + %zext.sext.255 = zext i16 %sext.255 to i32 ; 0x0000FFFF
> + %sext.zext.255 = sext i16 %zext.255 to i32 ; 0x000000FF
> + %zext.zext.sext.255 = zext i32 %zext.sext.255 to i64
> + %zext.sext.zext.255 = zext i32 %sext.zext.255 to i64
> + %a = getelementptr inbounds i8, i8* %mem, i64 %zext.zext.sext.255
> + %b = getelementptr inbounds i8, i8* %mem, i64 %zext.sext.zext.255
> + ret void
> +}
> +
> +; CHECK-LABEL: test_zext_sext_num
> +; CHECK: PartialAlias: i8* %a, i8* %b
> +; %a and %b NoAlias if %num == 255 (see @test_zext_sext_255), but %a and %b NoAlias for other values of %num (e.g. 0)
> +define void @test_zext_sext_num(i8* %mem, i8 %num) {
> + %zext.num = zext i8 %num to i16
> + %sext.num = sext i8 %num to i16
> + %zext.sext.num = zext i16 %sext.num to i32
> + %sext.zext.num = sext i16 %zext.num to i32
> + %zext.zext.sext.num = zext i32 %zext.sext.num to i64
> + %zext.sext.zext.num = zext i32 %sext.zext.num to i64
> + %a = getelementptr inbounds i8, i8* %mem, i64 %zext.zext.sext.num
> + %b = getelementptr inbounds i8, i8* %mem, i64 %zext.sext.zext.num
> + ret void
> +}
> +
> +; CHECK-LABEL: uncompressStream
> +; CHECK: MustAlias: i8* %a, i8* %b
> +; CHECK: NoAlias: i8* %a, i8* %c
> +define void @uncompressStream(i8* %mem) {
> + %zext.255 = zext i8 255 to i32
> + %sext.255 = sext i8 255 to i32
> + %a = getelementptr inbounds i8, i8* %mem, i32 255
> + %b = getelementptr inbounds i8, i8* %mem, i32 %zext.255
> + %c = getelementptr inbounds i8, i8* %mem, i32 %sext.255
> + ret void
> +}
> +
> +; CHECK-LABEL: constantOffsetHeuristic_i3_i32
> +; CHECK: NoAlias: i32* %a, i32* %b
> +; CHECK: NoAlias: i32* %a, i32* %c
> +; CHECK: NoAlias: i32* %b, i32* %c
> +define void @constantOffsetHeuristic_i3_i32(i32* %mem, i3 %val) {
> + %zext.plus.7 = add nsw i3 %val, 7
> + %zext.plus.4 = add nsw i3 %val, 4
> + %zext.val = zext i3 %val to i32
> + %zext.4 = zext i3 %zext.plus.4 to i32
> + %zext.7 = zext i3 %zext.plus.7 to i32
> + %a = getelementptr inbounds i32, i32* %mem, i32 %zext.4
> + %b = getelementptr inbounds i32, i32* %mem, i32 %zext.7
> + %c = getelementptr inbounds i32, i32* %mem, i32 %zext.val
> + ret void
> +}
> +
> +; CHECK-LABEL: constantOffsetHeuristic_i8_i32
> +; CHECK: NoAlias: i32* %a, i32* %b
> +; CHECK: NoAlias: i32* %a, i32* %c
> +; CHECK: NoAlias: i32* %b, i32* %c
> +define void @constantOffsetHeuristic_i8_i32(i32* %mem, i8 %val) {
> + %zext.plus.7 = add nsw i8 %val, 7
> + %zext.plus.4 = add nsw i8 %val, 4
> + %zext.val = zext i8 %val to i32
> + %zext.4 = zext i8 %zext.plus.4 to i32
> + %zext.7 = zext i8 %zext.plus.7 to i32
> + %a = getelementptr inbounds i32, i32* %mem, i32 %zext.4
> + %b = getelementptr inbounds i32, i32* %mem, i32 %zext.7
> + %c = getelementptr inbounds i32, i32* %mem, i32 %zext.val
> + ret void
> +}
> +
> +; CHECK-LABEL: constantOffsetHeuristic_i3_i8
> +; CHECK: PartialAlias: i32* %a, i32* %b
> +; CHECK: NoAlias: i32* %a, i32* %c
> +; CHECK: PartialAlias: i32* %b, i32* %c
> +define void @constantOffsetHeuristic_i3_i8(i8* %mem, i3 %val) {
> + %zext.plus.7 = add nsw i3 %val, 7
> + %zext.plus.4 = add nsw i3 %val, 4
> + %zext.val = zext i3 %val to i32
> + %zext.4 = zext i3 %zext.plus.4 to i32
> + %zext.7 = zext i3 %zext.plus.7 to i32
> + %a.8 = getelementptr inbounds i8, i8* %mem, i32 %zext.4
> + %b.8 = getelementptr inbounds i8, i8* %mem, i32 %zext.7
> + %c.8 = getelementptr inbounds i8, i8* %mem, i32 %zext.val
> + %a = bitcast i8* %a.8 to i32*
> + %b = bitcast i8* %b.8 to i32*
> + %c = bitcast i8* %c.8 to i32*
> + ret void
> +}
> +
> +; CHECK-LABEL: constantOffsetHeuristic_i8_i8
> +; CHECK: PartialAlias: i32* %a, i32* %b
> +; CHECK: NoAlias: i32* %a, i32* %c
> +; CHECK: NoAlias: i32* %b, i32* %c
> +define void @constantOffsetHeuristic_i8_i8(i8* %mem, i8 %val) {
> + %zext.plus.7 = add nsw i8 %val, 7
> + %zext.plus.4 = add nsw i8 %val, 4
> + %zext.val = zext i8 %val to i32
> + %zext.4 = zext i8 %zext.plus.4 to i32
> + %zext.7 = zext i8 %zext.plus.7 to i32
> + %a.8 = getelementptr inbounds i8, i8* %mem, i32 %zext.4
> + %b.8 = getelementptr inbounds i8, i8* %mem, i32 %zext.7
> + %c.8 = getelementptr inbounds i8, i8* %mem, i32 %zext.val
> + %a = bitcast i8* %a.8 to i32*
> + %b = bitcast i8* %b.8 to i32*
> + %c = bitcast i8* %c.8 to i32*
> + ret void
> +}
>
> Copied: llvm/trunk/test/Analysis/BasicAA/zext.ll (from r245393, llvm/trunk/test/Analysis/BasicAA/zext.ll)
> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Analysis/BasicAA/zext.ll?p2=llvm/trunk/test/Analysis/BasicAA/zext.ll&p1=llvm/trunk/test/Analysis/BasicAA/zext.ll&r1=245393&r2=246502&rev=246502&view=diff
> ==============================================================================
> --- llvm/trunk/test/Analysis/BasicAA/zext.ll (original)
> +++ llvm/trunk/test/Analysis/BasicAA/zext.ll Mon Aug 31 17:32:47 2015
> @@ -205,5 +205,27 @@ define void @test_const_eval_scaled(i8*
> ret void
> }
>
> +; CHECK-LABEL: Function: foo
> +; CHECK: MustAlias: float* %arrayidx, float* %arrayidx4.84
> +define float @foo(i32 *%A, float %rend, float** %wayar) {
> +entry:
> + %x0 = load i32, i32* %A, align 4
> + %conv = sext i32 %x0 to i64
> + %mul = shl nsw i64 %conv, 3
> + %call = tail call i8* @malloc(i64 %mul)
> + %x1 = bitcast i8* %call to float*
> +
> + %sub = add nsw i32 %x0, -1
> + %idxprom = sext i32 %sub to i64
> + %arrayidx = getelementptr inbounds float, float* %x1, i64 %idxprom
> + store float %rend, float* %arrayidx, align 8
> +
> + %indvars.iv76.83 = add nsw i64 %conv, -1
> + %arrayidx4.84 = getelementptr inbounds float, float* %x1, i64 %indvars.iv76.83
> + %x4 = load float, float* %arrayidx4.84, align 8
> +
> + ret float %x4
> +}
> +
> ; Function Attrs: nounwind
> declare noalias i8* @malloc(i64)
>
>
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