[llvm] r246502 - [BasicAA] Fix the handling of sext and zext in the analysis of GEPs.
Tom Stellard via llvm-commits
llvm-commits at lists.llvm.org
Tue Oct 27 08:50:59 PDT 2015
On Thu, Sep 10, 2015 at 03:28:11PM -0700, Hans Wennborg wrote:
> +Tom for 3.7.1
>
Do we still need this in the 3.7 branch? It looks like the commit that
introduced the bug (r221876) was already reverted in the 3.7 branch.
-Tom
> On Mon, Aug 31, 2015 at 4:04 PM, Hans Wennborg <hans at chromium.org> wrote:
> > The tag for 3.7.0 was committed last Friday, so it's too late for
> > that, but it seems like a good candidate for 3.7.1.
> >
> > I'm putting it on my list and will let Tom know about it when he
> > starts the 3.7.1 process.
> >
> > On Mon, Aug 31, 2015 at 3:40 PM, Quentin Colombet <qcolombet at apple.com> wrote:
> >> 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)
> >>>
> >>>
> >>> _______________________________________________
> >>> llvm-commits mailing list
> >>> llvm-commits at lists.llvm.org
> >>> http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-commits
> >>
More information about the llvm-commits
mailing list