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Revert r236894 "[BasicAA] Fix zext & sext handling"

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This seems to have caused PR23626: Clang miscompiles webkit's base64 decoder

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@237984 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Hans Wennborg 2015-05-22 01:27:37 +00:00
parent 6b3b93fc8b
commit 253c092e56
2 changed files with 58 additions and 377 deletions
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255
lib/Analysis/BasicAliasAnalysis.cpp
View File

@ -162,26 +162,20 @@ static bool isObjectSize(const Value *V, uint64_t Size,
//===----------------------------------------------------------------------===// //===----------------------------------------------------------------------===//
namespace { namespace {
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 { struct VariableGEPIndex {
// An opaque Value - we can't decompose this further.
const Value *V; 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; int64_t Scale;
bool operator==(const VariableGEPIndex &Other) const { bool operator==(const VariableGEPIndex &Other) const {
return V == Other.V && ZExtBits == Other.ZExtBits && return V == Other.V && Extension == Other.Extension &&
SExtBits == Other.SExtBits && Scale == Other.Scale; Scale == Other.Scale;
} }
bool operator!=(const VariableGEPIndex &Other) const { bool operator!=(const VariableGEPIndex &Other) const {
@ -199,12 +193,10 @@ namespace {
/// ///
/// Note that this looks through extends, so the high bits may not be /// Note that this looks through extends, so the high bits may not be
/// represented in the result. /// represented in the result.
static const Value *GetLinearExpression(const Value *V, APInt &Scale, static Value *GetLinearExpression(Value *V, APInt &Scale, APInt &Offset,
APInt &Offset, unsigned &ZExtBits, ExtensionKind &Extension,
unsigned &SExtBits, const DataLayout &DL, unsigned Depth,
const DataLayout &DL, unsigned Depth, AssumptionCache *AC, DominatorTree *DT) {
AssumptionCache *AC, DominatorTree *DT,
bool &NSW, bool &NUW) {
assert(V->getType()->isIntegerTy() && "Not an integer value"); assert(V->getType()->isIntegerTy() && "Not an integer value");
// Limit our recursion depth. // Limit our recursion depth.
@ -214,32 +206,18 @@ static const Value *GetLinearExpression(const Value *V, APInt &Scale,
return V; return V;
} }
if (const ConstantInt *Const = dyn_cast<ConstantInt>(V)) { if (ConstantInt *Const = dyn_cast<ConstantInt>(V)) {
// if it's a constant, just convert it to an offset and remove the variable. // if it's a constant, just convert it to an offset
// If we've been called recursively the Offset bit width will be greater // and remove the variable.
// than the constant's (the Offset's always as wide as the outermost call), Offset += Const->getValue();
// 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"); assert(Scale == 0 && "Constant values don't have a scale");
return V; return V;
} }
if (const BinaryOperator *BOp = dyn_cast<BinaryOperator>(V)) { if (BinaryOperator *BOp = dyn_cast<BinaryOperator>(V)) {
if (ConstantInt *RHSC = dyn_cast<ConstantInt>(BOp->getOperand(1))) { 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()) { switch (BOp->getOpcode()) {
default: 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: case Instruction::Or:
// X|C == X+C if all the bits in C are unset in X. Otherwise we can't // X|C == X+C if all the bits in C are unset in X. Otherwise we can't
// analyze it. // analyze it.
@ -248,88 +226,45 @@ static const Value *GetLinearExpression(const Value *V, APInt &Scale,
break; break;
// FALL THROUGH. // FALL THROUGH.
case Instruction::Add: case Instruction::Add:
V = GetLinearExpression(BOp->getOperand(0), Scale, Offset, ZExtBits, V = GetLinearExpression(BOp->getOperand(0), Scale, Offset, Extension,
SExtBits, DL, Depth + 1, AC, DT, NSW, NUW); DL, Depth + 1, AC, DT);
Offset += RHS; Offset += RHSC->getValue();
break; return V;
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: case Instruction::Mul:
V = GetLinearExpression(BOp->getOperand(0), Scale, Offset, ZExtBits, V = GetLinearExpression(BOp->getOperand(0), Scale, Offset, Extension,
SExtBits, DL, Depth + 1, AC, DT, NSW, NUW); DL, Depth + 1, AC, DT);
Offset *= RHS; Offset *= RHSC->getValue();
Scale *= RHS; Scale *= RHSC->getValue();
break; return V;
case Instruction::Shl: case Instruction::Shl:
V = GetLinearExpression(BOp->getOperand(0), Scale, Offset, ZExtBits, V = GetLinearExpression(BOp->getOperand(0), Scale, Offset, Extension,
SExtBits, DL, Depth + 1, AC, DT, NSW, NUW); DL, Depth + 1, AC, DT);
Offset <<= RHS.getLimitedValue(); Offset <<= RHSC->getValue().getLimitedValue();
Scale <<= RHS.getLimitedValue(); Scale <<= RHSC->getValue().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; 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 // 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 // bits of a sign or zero extended value - just scales and offsets. The
// extensions have to be consistent though. // extensions have to be consistent though.
if (isa<SExtInst>(V) || isa<ZExtInst>(V)) { if ((isa<SExtInst>(V) && Extension != EK_ZeroExt) ||
(isa<ZExtInst>(V) && Extension != EK_SignExt)) {
Value *CastOp = cast<CastInst>(V)->getOperand(0); Value *CastOp = cast<CastInst>(V)->getOperand(0);
unsigned NewWidth = V->getType()->getPrimitiveSizeInBits(); unsigned OldWidth = Scale.getBitWidth();
unsigned SmallWidth = CastOp->getType()->getPrimitiveSizeInBits(); unsigned SmallWidth = CastOp->getType()->getPrimitiveSizeInBits();
unsigned OldZExtBits = ZExtBits, OldSExtBits = SExtBits; Scale = Scale.trunc(SmallWidth);
const Value *Result = Offset = Offset.trunc(SmallWidth);
GetLinearExpression(CastOp, Scale, Offset, ZExtBits, SExtBits, DL, Extension = isa<SExtInst>(V) ? EK_SignExt : EK_ZeroExt;
Depth + 1, AC, DT, NSW, NUW);
// zext(zext(%x)) == zext(%x), and similiarly for sext; we'll handle this Value *Result = GetLinearExpression(CastOp, Scale, Offset, Extension, DL,
// by just incrementing the number of bits we've extended by. Depth + 1, AC, DT);
unsigned ExtendedBy = NewWidth - SmallWidth; Scale = Scale.zext(OldWidth);
if (isa<SExtInst>(V) && ZExtBits == 0) { // We have to sign-extend even if Extension == EK_ZeroExt as we can't
// sext(sext(%x, a), b) == sext(%x, a + b) // decompose a sign extension (i.e. zext(x - 1) != zext(x) - zext(-1)).
Offset = Offset.sext(OldWidth);
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; return Result;
} }
@ -411,7 +346,7 @@ DecomposeGEPExpression(const Value *V, int64_t &BaseOffs,
gep_type_iterator GTI = gep_type_begin(GEPOp); gep_type_iterator GTI = gep_type_begin(GEPOp);
for (User::const_op_iterator I = GEPOp->op_begin()+1, for (User::const_op_iterator I = GEPOp->op_begin()+1,
E = GEPOp->op_end(); I != E; ++I) { E = GEPOp->op_end(); I != E; ++I) {
const Value *Index = *I; Value *Index = *I;
// Compute the (potentially symbolic) offset in bytes for this index. // Compute the (potentially symbolic) offset in bytes for this index.
if (StructType *STy = dyn_cast<StructType>(*GTI++)) { if (StructType *STy = dyn_cast<StructType>(*GTI++)) {
// For a struct, add the member offset. // For a struct, add the member offset.
@ -423,27 +358,25 @@ DecomposeGEPExpression(const Value *V, int64_t &BaseOffs,
} }
// For an array/pointer, add the element offset, explicitly scaled. // For an array/pointer, add the element offset, explicitly scaled.
if (const ConstantInt *CIdx = dyn_cast<ConstantInt>(Index)) { if (ConstantInt *CIdx = dyn_cast<ConstantInt>(Index)) {
if (CIdx->isZero()) continue; if (CIdx->isZero()) continue;
BaseOffs += DL.getTypeAllocSize(*GTI) * CIdx->getSExtValue(); BaseOffs += DL.getTypeAllocSize(*GTI) * CIdx->getSExtValue();
continue; continue;
} }
uint64_t Scale = DL.getTypeAllocSize(*GTI); uint64_t Scale = DL.getTypeAllocSize(*GTI);
unsigned ZExtBits = 0, SExtBits = 0; ExtensionKind Extension = EK_NotExtended;
// If the integer type is smaller than the pointer size, it is implicitly // If the integer type is smaller than the pointer size, it is implicitly
// sign extended to pointer size. // sign extended to pointer size.
unsigned Width = Index->getType()->getIntegerBitWidth(); unsigned Width = Index->getType()->getIntegerBitWidth();
unsigned PointerSize = DL.getPointerSizeInBits(AS); if (DL.getPointerSizeInBits(AS) > Width)
if (PointerSize > Width) Extension = EK_SignExt;
SExtBits += PointerSize - Width;
// Use GetLinearExpression to decompose the index into a C1*V+C2 form. // Use GetLinearExpression to decompose the index into a C1*V+C2 form.
APInt IndexScale(Width, 0), IndexOffset(Width, 0); APInt IndexScale(Width, 0), IndexOffset(Width, 0);
bool NSW = true, NUW = true; Index = GetLinearExpression(Index, IndexScale, IndexOffset, Extension, DL,
Index = GetLinearExpression(Index, IndexScale, IndexOffset, ZExtBits, 0, AC, DT);
SExtBits, DL, 0, AC, DT, NSW, NUW);
// The GEP index scale ("Scale") scales C1*V+C2, yielding (C1*V+C2)*Scale. // 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. // This gives us an aggregate computation of (C1*Scale)*V + C2*Scale.
@ -455,8 +388,8 @@ DecomposeGEPExpression(const Value *V, int64_t &BaseOffs,
// A[x][x] -> x*16 + x*4 -> x*20 // A[x][x] -> x*16 + x*4 -> x*20
// This also ensures that 'x' only appears in the index list once. // This also ensures that 'x' only appears in the index list once.
for (unsigned i = 0, e = VarIndices.size(); i != e; ++i) { for (unsigned i = 0, e = VarIndices.size(); i != e; ++i) {
if (VarIndices[i].V == Index && VarIndices[i].ZExtBits == ZExtBits && if (VarIndices[i].V == Index &&
VarIndices[i].SExtBits == SExtBits) { VarIndices[i].Extension == Extension) {
Scale += VarIndices[i].Scale; Scale += VarIndices[i].Scale;
VarIndices.erase(VarIndices.begin()+i); VarIndices.erase(VarIndices.begin()+i);
break; break;
@ -465,13 +398,13 @@ DecomposeGEPExpression(const Value *V, int64_t &BaseOffs,
// Make sure that we have a scale that makes sense for this target's // Make sure that we have a scale that makes sense for this target's
// pointer size. // pointer size.
if (unsigned ShiftBits = 64 - PointerSize) { if (unsigned ShiftBits = 64 - DL.getPointerSizeInBits(AS)) {
Scale <<= ShiftBits; Scale <<= ShiftBits;
Scale = (int64_t)Scale >> ShiftBits; Scale = (int64_t)Scale >> ShiftBits;
} }
if (Scale) { if (Scale) {
VariableGEPIndex Entry = {Index, ZExtBits, SExtBits, VariableGEPIndex Entry = {Index, Extension,
static_cast<int64_t>(Scale)}; static_cast<int64_t>(Scale)};
VarIndices.push_back(Entry); VarIndices.push_back(Entry);
} }
@ -605,20 +538,6 @@ namespace {
/// is we say noalias(V, phi(VA, VB)) if noalias(V, VA) and noalias(V, VB). /// is we say noalias(V, phi(VA, VB)) if noalias(V, VA) and noalias(V, VB).
bool isValueEqualInPotentialCycles(const Value *V1, const Value *V2); bool isValueEqualInPotentialCycles(const Value *V1, const Value *V2);
/// \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);
/// \brief Dest and Src are the variable indices from two decomposed /// \brief Dest and Src are the variable indices from two decomposed
/// GetElementPtr instructions GEP1 and GEP2 which have common base /// GetElementPtr instructions GEP1 and GEP2 which have common base
/// pointers. Subtract the GEP2 indices from GEP1 to find the symbolic /// pointers. Subtract the GEP2 indices from GEP1 to find the symbolic
@ -1057,60 +976,6 @@ aliasSameBasePointerGEPs(const GEPOperator *GEP1, uint64_t V1Size,
return AliasAnalysis::MayAlias; return AliasAnalysis::MayAlias;
} }
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 == UnknownSize ||
V2Size == 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, 1),
V1Offset(Width, 1);
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;
}
/// aliasGEP - Provide a bunch of ad-hoc rules to disambiguate a GEP instruction /// aliasGEP - Provide a bunch of ad-hoc rules to disambiguate a GEP instruction
/// against another pointer. We know that V1 is a GEP, but we don't know /// against another pointer. We know that V1 is a GEP, but we don't know
/// anything about V2. UnderlyingV1 is GetUnderlyingObject(GEP1, DL), /// anything about V2. UnderlyingV1 is GetUnderlyingObject(GEP1, DL),
@ -1333,7 +1198,7 @@ BasicAliasAnalysis::aliasGEP(const GEPOperator *GEP1, uint64_t V1Size,
// Zero-extension widens the variable, and so forces the sign // Zero-extension widens the variable, and so forces the sign
// bit to zero. // bit to zero.
bool IsZExt = GEP1VariableIndices[i].ZExtBits > 0 || isa<ZExtInst>(V); bool IsZExt = GEP1VariableIndices[i].Extension == EK_ZeroExt;
SignKnownZero |= IsZExt; SignKnownZero |= IsZExt;
SignKnownOne &= !IsZExt; SignKnownOne &= !IsZExt;
@ -1362,10 +1227,6 @@ BasicAliasAnalysis::aliasGEP(const GEPOperator *GEP1, uint64_t V1Size,
// don't alias if V2Size can fit in the gap between V2 and GEP1BasePtr. // don't alias if V2Size can fit in the gap between V2 and GEP1BasePtr.
if (AllPositive && GEP1BaseOffset > 0 && V2Size <= (uint64_t) GEP1BaseOffset) if (AllPositive && GEP1BaseOffset > 0 && V2Size <= (uint64_t) GEP1BaseOffset)
return NoAlias; 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 // Statically, we can see that the base objects are the same, but the
@ -1704,14 +1565,14 @@ void BasicAliasAnalysis::GetIndexDifference(
for (unsigned i = 0, e = Src.size(); i != e; ++i) { for (unsigned i = 0, e = Src.size(); i != e; ++i) {
const Value *V = Src[i].V; const Value *V = Src[i].V;
unsigned ZExtBits = Src[i].ZExtBits, SExtBits = Src[i].SExtBits; ExtensionKind Extension = Src[i].Extension;
int64_t Scale = Src[i].Scale; int64_t Scale = Src[i].Scale;
// Find V in Dest. This is N^2, but pointer indices almost never have more // Find V in Dest. This is N^2, but pointer indices almost never have more
// than a few variable indexes. // than a few variable indexes.
for (unsigned j = 0, e = Dest.size(); j != e; ++j) { for (unsigned j = 0, e = Dest.size(); j != e; ++j) {
if (!isValueEqualInPotentialCycles(Dest[j].V, V) || if (!isValueEqualInPotentialCycles(Dest[j].V, V) ||
Dest[j].ZExtBits != ZExtBits || Dest[j].SExtBits != SExtBits) Dest[j].Extension != Extension)
continue; continue;
// If we found it, subtract off Scale V's from the entry in Dest. If it // If we found it, subtract off Scale V's from the entry in Dest. If it
@ -1726,7 +1587,7 @@ void BasicAliasAnalysis::GetIndexDifference(
// If we didn't consume this entry, add it to the end of the Dest list. // If we didn't consume this entry, add it to the end of the Dest list.
if (Scale) { if (Scale) {
VariableGEPIndex Entry = {V, ZExtBits, SExtBits, -Scale}; VariableGEPIndex Entry = { V, Extension, -Scale };
Dest.push_back(Entry); Dest.push_back(Entry);
} }
} }

180
test/Analysis/BasicAA/q.bad.ll
View File

@ -1,180 +0,0 @@
; 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
}