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[AA][NFC] Convert AliasResult to class containing offset for PartialAlias case.

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Add an ability to store `Offset` between partially aliased location. Use this
storage within returned `ResultAlias` instead of caching it in `AAQueryInfo`.

Reviewed By: asbirlea

Differential Revision: https://reviews.llvm.org/D98718
This commit is contained in:
dfukalov 2021-03-16 16:36:17 +03:00
parent cb0d7fd331
commit 1f5e832e39
9 changed files with 118 additions and 117 deletions
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115
include/llvm/Analysis/AliasAnalysis.h
View File

@ -78,21 +78,64 @@ class Value;
///
/// See docs/AliasAnalysis.html for more information on the specific meanings
/// of these values.
enum AliasResult : uint8_t {
/// The two locations do not alias at all.
///
/// This value is arranged to convert to false, while all other values
/// convert to true. This allows a boolean context to convert the result to
/// a binary flag indicating whether there is the possibility of aliasing.
NoAlias = 0,
/// The two locations may or may not alias. This is the least precise result.
MayAlias,
/// The two locations alias, but only due to a partial overlap.
PartialAlias,
/// The two locations precisely alias each other.
MustAlias,
class AliasResult {
private:
static const int OffsetBits = 23;
static const int AliasBits = 8;
static_assert(AliasBits + 1 + OffsetBits <= 32,
"AliasResult size is intended to be 4 bytes!");
unsigned int Alias : AliasBits;
unsigned int HasOffset : 1;
signed int Offset : OffsetBits;
public:
enum Result : uint8_t {
/// The two locations do not alias at all.
///
/// This value is arranged to convert to false, while all other values
/// convert to true. This allows a boolean context to convert the result to
/// a binary flag indicating whether there is the possibility of aliasing.
NoAlias = 0,
/// The two locations may or may not alias. This is the least precise
/// result.
MayAlias,
/// The two locations alias, but only due to a partial overlap.
PartialAlias,
/// The two locations precisely alias each other.
MustAlias,
};
static_assert(MustAlias < (1 << AliasBits),
"Not enough bit field size for the enum!");
explicit AliasResult() = delete;
constexpr AliasResult(const Result &Alias)
: Alias(Alias), HasOffset(false), Offset(0) {}
operator Result() const { return static_cast<Result>(Alias); }
constexpr bool hasOffset() const { return HasOffset; }
constexpr int32_t getOffset() const {
assert(HasOffset && "No offset!");
return Offset;
}
void setOffset(int32_t NewOffset) {
if (isInt<OffsetBits>(NewOffset)) {
HasOffset = true;
Offset = NewOffset;
}
}
/// Helper for processing AliasResult for swapped memory location pairs.
void swap(bool DoSwap) {
if (DoSwap && hasOffset())
setOffset(-getOffset());
}
};
static_assert(sizeof(AliasResult) == 4,
"AliasResult size is intended to be 4 bytes!");
/// << operator for AliasResult.
raw_ostream &operator<<(raw_ostream &OS, AliasResult AR);
@ -369,16 +412,6 @@ template <> struct DenseMapInfo<AACacheLoc> {
/// The information stored in an `AAQueryInfo` is currently limitted to the
/// caches used by BasicAA, but can further be extended to fit other AA needs.
class AAQueryInfo {
/// Storage for estimated relative offsets between two partially aliased
/// values. Used to optimize out redundant parts of loads/stores (in GVN/DSE).
/// These users cannot process quite complicated addresses (e.g. GEPs with
/// non-constant offsets). Used by BatchAAResults only.
bool CacheOffsets = false;
SmallDenseMap<std::pair<std::pair<const Value *, const Value *>,
std::pair<uint64_t, uint64_t>>,
int64_t, 4>
ClobberOffsets;
public:
using LocPair = std::pair<AACacheLoc, AACacheLoc>;
struct CacheEntry {
@ -406,9 +439,7 @@ public:
/// assumption is disproven.
SmallVector<AAQueryInfo::LocPair, 4> AssumptionBasedResults;
AAQueryInfo(bool CacheOffsets = false)
: CacheOffsets(CacheOffsets), ClobberOffsets(), AliasCache(),
IsCapturedCache() {}
AAQueryInfo() : AliasCache(), IsCapturedCache() {}
/// Create a new AAQueryInfo based on this one, but with the cache cleared.
/// This is used for recursive queries across phis, where cache results may
@ -418,33 +449,6 @@ public:
NewAAQI.Depth = Depth;
return NewAAQI;
}
Optional<int64_t> getClobberOffset(const Value *Ptr1, const Value *Ptr2,
uint64_t Size1, uint64_t Size2) const {
assert(CacheOffsets && "Clobber offset cached in batch mode only!");
const bool Swapped = Ptr1 > Ptr2;
if (Swapped) {
std::swap(Ptr1, Ptr2);
std::swap(Size1, Size2);
}
const auto IOff = ClobberOffsets.find({{Ptr1, Ptr2}, {Size1, Size2}});
if (IOff != ClobberOffsets.end())
return Swapped ? -IOff->second : IOff->second;
return None;
}
void setClobberOffset(const Value *Ptr1, const Value *Ptr2, uint64_t Size1,
uint64_t Size2, int64_t Offset) {
// Cache offset for batch mode only.
if (!CacheOffsets)
return;
if (Ptr1 > Ptr2) {
std::swap(Ptr1, Ptr2);
std::swap(Size1, Size2);
Offset = -Offset;
}
ClobberOffsets[{{Ptr1, Ptr2}, {Size1, Size2}}] = Offset;
}
};
class BatchAAResults;
@ -887,8 +891,7 @@ class BatchAAResults {
AAQueryInfo AAQI;
public:
BatchAAResults(AAResults &AAR, bool CacheOffsets = false)
: AA(AAR), AAQI(CacheOffsets) {}
BatchAAResults(AAResults &AAR) : AA(AAR), AAQI() {}
AliasResult alias(const MemoryLocation &LocA, const MemoryLocation &LocB) {
return AA.alias(LocA, LocB, AAQI);
}
@ -922,8 +925,6 @@ public:
MemoryLocation(V2, LocationSize::precise(1))) ==
AliasResult::MustAlias;
}
Optional<int64_t> getClobberOffset(const MemoryLocation &LocA,
const MemoryLocation &LocB) const;
};
/// Temporary typedef for legacy code that uses a generic \c AliasAnalysis

7
include/llvm/Analysis/AliasSetTracker.h
View File

@ -35,18 +35,17 @@
namespace llvm {
class AAResults;
class AliasResult;
class AliasSetTracker;
class BasicBlock;
class LoadInst;
class AnyMemSetInst;
class AnyMemTransferInst;
class BasicBlock;
class LoadInst;
class raw_ostream;
class StoreInst;
class VAArgInst;
class Value;
enum AliasResult : uint8_t;
class AliasSet : public ilist_node<AliasSet> {
friend class AliasSetTracker;

5
include/llvm/Analysis/MemorySSA.h
View File

@ -299,8 +299,9 @@ protected:
OptimizedAccessAlias = AR;
}
void setDefiningAccess(MemoryAccess *DMA, bool Optimized = false,
Optional<AliasResult> AR = AliasResult::MayAlias) {
void setDefiningAccess(
MemoryAccess *DMA, bool Optimized = false,
Optional<AliasResult> AR = AliasResult(AliasResult::MayAlias)) {
if (!Optimized) {
setOperand(0, DMA);
return;

11
lib/Analysis/AliasAnalysis.cpp
View File

@ -958,17 +958,6 @@ AAResults llvm::createLegacyPMAAResults(Pass &P, Function &F,
return AAR;
}
Optional<int64_t>
BatchAAResults::getClobberOffset(const MemoryLocation &LocA,
const MemoryLocation &LocB) const {
if (!LocA.Size.hasValue() || !LocB.Size.hasValue())
return None;
const Value *V1 = LocA.Ptr->stripPointerCastsForAliasAnalysis();
const Value *V2 = LocB.Ptr->stripPointerCastsForAliasAnalysis();
return AAQI.getClobberOffset(V1, V2, LocA.Size.getValue(),
LocB.Size.getValue());
}
bool llvm::isNoAliasCall(const Value *V) {
if (const auto *Call = dyn_cast<CallBase>(V))
return Call->hasRetAttr(Attribute::NoAlias);

32
lib/Analysis/BasicAliasAnalysis.cpp
View File

@ -1015,14 +1015,15 @@ AliasResult BasicAAResult::aliasGEP(
// TODO: This limitation exists for compile-time reasons. Relax it if we
// can avoid exponential pathological cases.
if (!isa<GEPOperator>(V2))
return MayAlias;
return AliasResult::MayAlias;
// If both accesses have unknown size, we can only check whether the base
// objects don't alias.
AliasResult BaseAlias = getBestAAResults().alias(
MemoryLocation::getBeforeOrAfter(UnderlyingV1),
MemoryLocation::getBeforeOrAfter(UnderlyingV2), AAQI);
return BaseAlias == NoAlias ? NoAlias : MayAlias;
return BaseAlias == AliasResult::NoAlias ? AliasResult::NoAlias
: AliasResult::MayAlias;
}
DecomposedGEP DecompGEP1 = DecomposeGEPExpression(GEP1, DL, &AC, DT);
@ -1090,8 +1091,9 @@ AliasResult BasicAAResult::aliasGEP(
const Value *RightPtr = GEP1;
LocationSize VLeftSize = V2Size;
LocationSize VRightSize = V1Size;
const bool Swapped = Off.isNegative();
if (Off.isNegative()) {
if (Swapped) {
// Swap if we have the situation where:
// + +
// | BaseOffset |
@ -1108,16 +1110,16 @@ AliasResult BasicAAResult::aliasGEP(
if (Off.ult(LSize)) {
// Conservatively drop processing if a phi was visited and/or offset is
// too big.
AliasResult AR = AliasResult::PartialAlias;
if (VisitedPhiBBs.empty() && VRightSize.hasValue() &&
Off.ule(INT64_MAX)) {
Off.ule(INT32_MAX) && (Off + VRightSize.getValue()).ule(LSize)) {
// Memory referenced by right pointer is nested. Save the offset in
// cache.
const uint64_t RSize = VRightSize.getValue();
if ((Off + RSize).ule(LSize))
AAQI.setClobberOffset(LeftPtr, RightPtr, LSize, RSize,
Off.getSExtValue());
// cache. Note that originally offset estimated as GEP1-V2, but
// AliasResult contains the shift that represents GEP1+Offset=V2.
AR.setOffset(-Off.getSExtValue());
AR.swap(Swapped);
}
return AliasResult::PartialAlias;
return AR;
}
return AliasResult::NoAlias;
}
@ -1531,7 +1533,8 @@ AliasResult BasicAAResult::aliasCheck(const Value *V1, LocationSize V1Size,
// Check the cache before climbing up use-def chains. This also terminates
// otherwise infinitely recursive queries.
AAQueryInfo::LocPair Locs({V1, V1Size}, {V2, V2Size});
if (V1 > V2)
const bool Swapped = V1 > V2;
if (Swapped)
std::swap(Locs.first, Locs.second);
const auto &Pair = AAQI.AliasCache.try_emplace(
Locs, AAQueryInfo::CacheEntry{AliasResult::NoAlias, 0});
@ -1542,7 +1545,10 @@ AliasResult BasicAAResult::aliasCheck(const Value *V1, LocationSize V1Size,
++Entry.NumAssumptionUses;
++AAQI.NumAssumptionUses;
}
return Entry.Result;
// Cache contains sorted {V1,V2} pairs but we should return original order.
auto Result = Entry.Result;
Result.swap(Swapped);
return Result;
}
int OrigNumAssumptionUses = AAQI.NumAssumptionUses;
@ -1563,6 +1569,8 @@ AliasResult BasicAAResult::aliasCheck(const Value *V1, LocationSize V1Size,
// This is a definitive result now, when considered as a root query.
AAQI.NumAssumptionUses -= Entry.NumAssumptionUses;
Entry.Result = Result;
// Cache contains sorted {V1,V2} pairs.
Entry.Result.swap(Swapped);
Entry.NumAssumptionUses = -1;
// If the assumption has been disproven, remove any results that may have

20
lib/Analysis/MemorySSA.cpp
View File

@ -286,7 +286,7 @@ instructionClobbersQuery(const MemoryDef *MD, const MemoryLocation &UseLoc,
case Intrinsic::invariant_end:
case Intrinsic::assume:
case Intrinsic::experimental_noalias_scope_decl:
return {false, AliasResult::NoAlias};
return {false, AliasResult(AliasResult::NoAlias)};
case Intrinsic::dbg_addr:
case Intrinsic::dbg_declare:
case Intrinsic::dbg_label:
@ -305,7 +305,8 @@ instructionClobbersQuery(const MemoryDef *MD, const MemoryLocation &UseLoc,
if (auto *DefLoad = dyn_cast<LoadInst>(DefInst))
if (auto *UseLoad = dyn_cast_or_null<LoadInst>(UseInst))
return {!areLoadsReorderable(UseLoad, DefLoad), AliasResult::MayAlias};
return {!areLoadsReorderable(UseLoad, DefLoad),
AliasResult(AliasResult::MayAlias)};
ModRefInfo I = AA.getModRefInfo(DefInst, UseLoc);
AR = isMustSet(I) ? AliasResult::MustAlias : AliasResult::MayAlias;
@ -344,7 +345,7 @@ struct UpwardsMemoryQuery {
const Instruction *Inst = nullptr;
// The MemoryAccess we actually got called with, used to test local domination
const MemoryAccess *OriginalAccess = nullptr;
Optional<AliasResult> AR = AliasResult::MayAlias;
Optional<AliasResult> AR = AliasResult(AliasResult::MayAlias);
bool SkipSelfAccess = false;
UpwardsMemoryQuery() = default;
@ -570,14 +571,14 @@ template <class AliasAnalysisType> class ClobberWalker {
for (MemoryAccess *Current : def_chain(Desc.Last)) {
Desc.Last = Current;
if (Current == StopAt || Current == SkipStopAt)
return {Current, false, AliasResult::MayAlias};
return {Current, false, AliasResult(AliasResult::MayAlias)};
if (auto *MD = dyn_cast<MemoryDef>(Current)) {
if (MSSA.isLiveOnEntryDef(MD))
return {MD, true, AliasResult::MustAlias};
return {MD, true, AliasResult(AliasResult::MustAlias)};
if (!--*UpwardWalkLimit)
return {Current, true, AliasResult::MayAlias};
return {Current, true, AliasResult(AliasResult::MayAlias)};
ClobberAlias CA =
instructionClobbersQuery(MD, Desc.Loc, Query->Inst, AA);
@ -591,7 +592,7 @@ template <class AliasAnalysisType> class ClobberWalker {
assert(isa<MemoryPhi>(Desc.Last) &&
"Ended at a non-clobber that's not a phi?");
return {Desc.Last, false, AliasResult::MayAlias};
return {Desc.Last, false, AliasResult(AliasResult::MayAlias)};
}
void addSearches(MemoryPhi *Phi, SmallVectorImpl<ListIndex> &PausedSearches,
@ -2490,8 +2491,9 @@ MemorySSA::ClobberWalkerBase<AliasAnalysisType>::getClobberingMemoryAccessBase(
StartingAccess->setOptimized(OptimizedAccess);
if (MSSA->isLiveOnEntryDef(OptimizedAccess))
StartingAccess->setOptimizedAccessType(None);
else if (Q.AR == AliasResult::MustAlias)
StartingAccess->setOptimizedAccessType(AliasResult::MustAlias);
else if (Q.AR && *Q.AR == AliasResult::MustAlias)
StartingAccess->setOptimizedAccessType(
AliasResult(AliasResult::MustAlias));
} else
OptimizedAccess = StartingAccess->getOptimized();

10
lib/Transforms/Scalar/DeadStoreElimination.cpp
View File

@ -402,9 +402,9 @@ isOverwrite(const Instruction *LaterI, const Instruction *EarlierI,
}
// If we hit a partial alias we may have a full overwrite
if (AAR == AliasResult::PartialAlias) {
int64_t Off = AA.getClobberOffset(Later, Earlier).getValueOr(0);
if (Off > 0 && (uint64_t)Off + EarlierSize <= LaterSize)
if (AAR == AliasResult::PartialAlias && AAR.hasOffset()) {
int32_t Off = AAR.getOffset();
if (Off >= 0 && (uint64_t)Off + EarlierSize <= LaterSize)
return OW_Complete;
}
@ -996,8 +996,8 @@ struct DSEState {
DSEState(Function &F, AliasAnalysis &AA, MemorySSA &MSSA, DominatorTree &DT,
PostDominatorTree &PDT, const TargetLibraryInfo &TLI)
: F(F), AA(AA), BatchAA(AA, /*CacheOffsets =*/true), MSSA(MSSA), DT(DT),
PDT(PDT), TLI(TLI), DL(F.getParent()->getDataLayout()) {}
: F(F), AA(AA), BatchAA(AA), MSSA(MSSA), DT(DT), PDT(PDT), TLI(TLI),
DL(F.getParent()->getDataLayout()) {}
static DSEState get(Function &F, AliasAnalysis &AA, MemorySSA &MSSA,
DominatorTree &DT, PostDominatorTree &PDT,

17
unittests/Analysis/AliasAnalysisTest.cpp
View File

@ -309,11 +309,11 @@ TEST_F(AliasAnalysisTest, PartialAliasOffset) {
%i2 = zext i32 %i to i64
%i3 = getelementptr inbounds float, float* %arg, i64 %i2
%i4 = bitcast float* %i3 to <2 x float>*
%L2 = load <2 x float>, <2 x float>* %i4, align 16
%L1 = load <2 x float>, <2 x float>* %i4, align 16
%i7 = add nuw nsw i32 %i, 1
%i8 = zext i32 %i7 to i64
%i9 = getelementptr inbounds float, float* %arg, i64 %i8
%L1 = load float, float* %i9, align 4
%L2 = load float, float* %i9, align 4
ret void
}
)",
@ -324,18 +324,13 @@ TEST_F(AliasAnalysisTest, PartialAliasOffset) {
Function *F = M->getFunction("foo");
const auto Loc1 = MemoryLocation::get(getInstructionByName(*F, "L1"));
auto Loc2 = MemoryLocation::get(getInstructionByName(*F, "L2"));
const auto Loc2 = MemoryLocation::get(getInstructionByName(*F, "L2"));
auto &AA = getAAResults(*F);
BatchAAResults BatchAA(AA, /*CacheOffsets =*/true);
EXPECT_EQ(AliasResult::PartialAlias, BatchAA.alias(Loc1, Loc2));
EXPECT_EQ(-4, BatchAA.getClobberOffset(Loc1, Loc2).getValueOr(0));
EXPECT_EQ(4, BatchAA.getClobberOffset(Loc2, Loc1).getValueOr(0));
// Check that no offset returned for different size.
Loc2.Size = LocationSize::precise(42);
EXPECT_EQ(0, BatchAA.getClobberOffset(Loc1, Loc2).getValueOr(0));
const auto AR = AA.alias(Loc1, Loc2);
EXPECT_EQ(AR, AliasResult::PartialAlias);
EXPECT_EQ(4, AR.getOffset());
}
class AAPassInfraTest : public testing::Test {

18
unittests/Analysis/MemorySSATest.cpp
View File

@ -1038,7 +1038,8 @@ TEST_F(MemorySSATest, TestLoadMustAlias) {
}
for (LoadInst *V : {LA3, LA4}) {
MemoryUse *MemUse = dyn_cast_or_null<MemoryUse>(MSSA.getMemoryAccess(V));
EXPECT_EQ(MemUse->getOptimizedAccessType(), AliasResult::MustAlias)
EXPECT_EQ(MemUse->getOptimizedAccessType().getValue(),
AliasResult::MustAlias)
<< "Load " << I << " doesn't have the correct alias information";
// EXPECT_EQ expands such that if we increment I above, it won't get
// incremented except when we try to print the error message.
@ -1087,7 +1088,8 @@ TEST_F(MemorySSATest, TestStoreMustAlias) {
EXPECT_EQ(MemDef->getOptimizedAccessType(), None)
<< "Store " << I << " doesn't have the correct alias information";
else
EXPECT_EQ(MemDef->getOptimizedAccessType(), AliasResult::MustAlias)
EXPECT_EQ(MemDef->getOptimizedAccessType().getValue(),
AliasResult::MustAlias)
<< "Store " << I << " doesn't have the correct alias information";
// EXPECT_EQ expands such that if we increment I above, it won't get
// incremented except when we try to print the error message.
@ -1121,7 +1123,8 @@ TEST_F(MemorySSATest, TestLoadMayAlias) {
unsigned I = 0;
for (LoadInst *V : {LA1, LB1}) {
MemoryUse *MemUse = dyn_cast_or_null<MemoryUse>(MSSA.getMemoryAccess(V));
EXPECT_EQ(MemUse->getOptimizedAccessType(), AliasResult::MayAlias)
EXPECT_EQ(MemUse->getOptimizedAccessType().getValue(),
AliasResult::MayAlias)
<< "Load " << I << " doesn't have the correct alias information";
// EXPECT_EQ expands such that if we increment I above, it won't get
// incremented except when we try to print the error message.
@ -1129,7 +1132,8 @@ TEST_F(MemorySSATest, TestLoadMayAlias) {
}
for (LoadInst *V : {LA2, LB2}) {
MemoryUse *MemUse = dyn_cast_or_null<MemoryUse>(MSSA.getMemoryAccess(V));
EXPECT_EQ(MemUse->getOptimizedAccessType(), AliasResult::MustAlias)
EXPECT_EQ(MemUse->getOptimizedAccessType().getValue(),
AliasResult::MustAlias)
<< "Load " << I << " doesn't have the correct alias information";
// EXPECT_EQ expands such that if we increment I above, it won't get
// incremented except when we try to print the error message.
@ -1189,13 +1193,15 @@ TEST_F(MemorySSATest, TestStoreMayAlias) {
EXPECT_EQ(MemDef->isOptimized(), true)
<< "Store " << I << " was not optimized";
if (I == 1 || I == 3 || I == 4)
EXPECT_EQ(MemDef->getOptimizedAccessType(), AliasResult::MayAlias)
EXPECT_EQ(MemDef->getOptimizedAccessType().getValue(),
AliasResult::MayAlias)
<< "Store " << I << " doesn't have the correct alias information";
else if (I == 0 || I == 2)
EXPECT_EQ(MemDef->getOptimizedAccessType(), None)
<< "Store " << I << " doesn't have the correct alias information";
else
EXPECT_EQ(MemDef->getOptimizedAccessType(), AliasResult::MustAlias)
EXPECT_EQ(MemDef->getOptimizedAccessType().getValue(),
AliasResult::MustAlias)
<< "Store " << I << " doesn't have the correct alias information";
// EXPECT_EQ expands such that if we increment I above, it won't get
// incremented except when we try to print the error message.