| //===------ DeLICM.cpp -----------------------------------------*- C++ -*-===// |
| // |
| // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions. |
| // See https://llvm.org/LICENSE.txt for license information. |
| // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception |
| // |
| //===----------------------------------------------------------------------===// |
| // |
| // Undo the effect of Loop Invariant Code Motion (LICM) and |
| // GVN Partial Redundancy Elimination (PRE) on SCoP-level. |
| // |
| // Namely, remove register/scalar dependencies by mapping them back to array |
| // elements. |
| // |
| //===----------------------------------------------------------------------===// |
| |
| #include "polly/DeLICM.h" |
| #include "polly/LinkAllPasses.h" |
| #include "polly/Options.h" |
| #include "polly/ScopInfo.h" |
| #include "polly/ScopPass.h" |
| #include "polly/Support/GICHelper.h" |
| #include "polly/Support/ISLOStream.h" |
| #include "polly/Support/ISLTools.h" |
| #include "polly/ZoneAlgo.h" |
| #include "llvm/ADT/Statistic.h" |
| #include "llvm/InitializePasses.h" |
| |
| #define DEBUG_TYPE "polly-delicm" |
| |
| using namespace polly; |
| using namespace llvm; |
| |
| namespace { |
| |
| cl::opt<int> |
| DelicmMaxOps("polly-delicm-max-ops", |
| cl::desc("Maximum number of isl operations to invest for " |
| "lifetime analysis; 0=no limit"), |
| cl::init(1000000), cl::cat(PollyCategory)); |
| |
| cl::opt<bool> DelicmOverapproximateWrites( |
| "polly-delicm-overapproximate-writes", |
| cl::desc( |
| "Do more PHI writes than necessary in order to avoid partial accesses"), |
| cl::init(false), cl::Hidden, cl::cat(PollyCategory)); |
| |
| cl::opt<bool> DelicmPartialWrites("polly-delicm-partial-writes", |
| cl::desc("Allow partial writes"), |
| cl::init(true), cl::Hidden, |
| cl::cat(PollyCategory)); |
| |
| cl::opt<bool> |
| DelicmComputeKnown("polly-delicm-compute-known", |
| cl::desc("Compute known content of array elements"), |
| cl::init(true), cl::Hidden, cl::cat(PollyCategory)); |
| |
| STATISTIC(DeLICMAnalyzed, "Number of successfully analyzed SCoPs"); |
| STATISTIC(DeLICMOutOfQuota, |
| "Analyses aborted because max_operations was reached"); |
| STATISTIC(MappedValueScalars, "Number of mapped Value scalars"); |
| STATISTIC(MappedPHIScalars, "Number of mapped PHI scalars"); |
| STATISTIC(TargetsMapped, "Number of stores used for at least one mapping"); |
| STATISTIC(DeLICMScopsModified, "Number of SCoPs optimized"); |
| |
| STATISTIC(NumValueWrites, "Number of scalar value writes after DeLICM"); |
| STATISTIC(NumValueWritesInLoops, |
| "Number of scalar value writes nested in affine loops after DeLICM"); |
| STATISTIC(NumPHIWrites, "Number of scalar phi writes after DeLICM"); |
| STATISTIC(NumPHIWritesInLoops, |
| "Number of scalar phi writes nested in affine loops after DeLICM"); |
| STATISTIC(NumSingletonWrites, "Number of singleton writes after DeLICM"); |
| STATISTIC(NumSingletonWritesInLoops, |
| "Number of singleton writes nested in affine loops after DeLICM"); |
| |
| isl::union_map computeReachingOverwrite(isl::union_map Schedule, |
| isl::union_map Writes, |
| bool InclPrevWrite, |
| bool InclOverwrite) { |
| return computeReachingWrite(Schedule, Writes, true, InclPrevWrite, |
| InclOverwrite); |
| } |
| |
| /// Compute the next overwrite for a scalar. |
| /// |
| /// @param Schedule { DomainWrite[] -> Scatter[] } |
| /// Schedule of (at least) all writes. Instances not in @p |
| /// Writes are ignored. |
| /// @param Writes { DomainWrite[] } |
| /// The element instances that write to the scalar. |
| /// @param InclPrevWrite Whether to extend the timepoints to include |
| /// the timepoint where the previous write happens. |
| /// @param InclOverwrite Whether the reaching overwrite includes the timepoint |
| /// of the overwrite itself. |
| /// |
| /// @return { Scatter[] -> DomainDef[] } |
| isl::union_map computeScalarReachingOverwrite(isl::union_map Schedule, |
| isl::union_set Writes, |
| bool InclPrevWrite, |
| bool InclOverwrite) { |
| |
| // { DomainWrite[] } |
| auto WritesMap = isl::union_map::from_domain(Writes); |
| |
| // { [Element[] -> Scatter[]] -> DomainWrite[] } |
| auto Result = computeReachingOverwrite( |
| std::move(Schedule), std::move(WritesMap), InclPrevWrite, InclOverwrite); |
| |
| return Result.domain_factor_range(); |
| } |
| |
| /// Overload of computeScalarReachingOverwrite, with only one writing statement. |
| /// Consequently, the result consists of only one map space. |
| /// |
| /// @param Schedule { DomainWrite[] -> Scatter[] } |
| /// @param Writes { DomainWrite[] } |
| /// @param InclPrevWrite Include the previous write to result. |
| /// @param InclOverwrite Include the overwrite to the result. |
| /// |
| /// @return { Scatter[] -> DomainWrite[] } |
| isl::map computeScalarReachingOverwrite(isl::union_map Schedule, |
| isl::set Writes, bool InclPrevWrite, |
| bool InclOverwrite) { |
| isl::space ScatterSpace = getScatterSpace(Schedule); |
| isl::space DomSpace = Writes.get_space(); |
| |
| isl::union_map ReachOverwrite = computeScalarReachingOverwrite( |
| Schedule, isl::union_set(Writes), InclPrevWrite, InclOverwrite); |
| |
| isl::space ResultSpace = ScatterSpace.map_from_domain_and_range(DomSpace); |
| return singleton(std::move(ReachOverwrite), ResultSpace); |
| } |
| |
| /// Try to find a 'natural' extension of a mapped to elements outside its |
| /// domain. |
| /// |
| /// @param Relevant The map with mapping that may not be modified. |
| /// @param Universe The domain to which @p Relevant needs to be extended. |
| /// |
| /// @return A map with that associates the domain elements of @p Relevant to the |
| /// same elements and in addition the elements of @p Universe to some |
| /// undefined elements. The function prefers to return simple maps. |
| isl::union_map expandMapping(isl::union_map Relevant, isl::union_set Universe) { |
| Relevant = Relevant.coalesce(); |
| isl::union_set RelevantDomain = Relevant.domain(); |
| isl::union_map Simplified = Relevant.gist_domain(RelevantDomain); |
| Simplified = Simplified.coalesce(); |
| return Simplified.intersect_domain(Universe); |
| } |
| |
| /// Represent the knowledge of the contents of any array elements in any zone or |
| /// the knowledge we would add when mapping a scalar to an array element. |
| /// |
| /// Every array element at every zone unit has one of two states: |
| /// |
| /// - Unused: Not occupied by any value so a transformation can change it to |
| /// other values. |
| /// |
| /// - Occupied: The element contains a value that is still needed. |
| /// |
| /// The union of Unused and Unknown zones forms the universe, the set of all |
| /// elements at every timepoint. The universe can easily be derived from the |
| /// array elements that are accessed someway. Arrays that are never accessed |
| /// also never play a role in any computation and can hence be ignored. With a |
| /// given universe, only one of the sets needs to stored implicitly. Computing |
| /// the complement is also an expensive operation, hence this class has been |
| /// designed that only one of sets is needed while the other is assumed to be |
| /// implicit. It can still be given, but is mostly ignored. |
| /// |
| /// There are two use cases for the Knowledge class: |
| /// |
| /// 1) To represent the knowledge of the current state of ScopInfo. The unused |
| /// state means that an element is currently unused: there is no read of it |
| /// before the next overwrite. Also called 'Existing'. |
| /// |
| /// 2) To represent the requirements for mapping a scalar to array elements. The |
| /// unused state means that there is no change/requirement. Also called |
| /// 'Proposed'. |
| /// |
| /// In addition to these states at unit zones, Knowledge needs to know when |
| /// values are written. This is because written values may have no lifetime (one |
| /// reason is that the value is never read). Such writes would therefore never |
| /// conflict, but overwrite values that might still be required. Another source |
| /// of problems are multiple writes to the same element at the same timepoint, |
| /// because their order is undefined. |
| class Knowledge { |
| private: |
| /// { [Element[] -> Zone[]] } |
| /// Set of array elements and when they are alive. |
| /// Can contain a nullptr; in this case the set is implicitly defined as the |
| /// complement of #Unused. |
| /// |
| /// The set of alive array elements is represented as zone, as the set of live |
| /// values can differ depending on how the elements are interpreted. |
| /// Assuming a value X is written at timestep [0] and read at timestep [1] |
| /// without being used at any later point, then the value is alive in the |
| /// interval ]0,1[. This interval cannot be represented by an integer set, as |
| /// it does not contain any integer point. Zones allow us to represent this |
| /// interval and can be converted to sets of timepoints when needed (e.g., in |
| /// isConflicting when comparing to the write sets). |
| /// @see convertZoneToTimepoints and this file's comment for more details. |
| isl::union_set Occupied; |
| |
| /// { [Element[] -> Zone[]] } |
| /// Set of array elements when they are not alive, i.e. their memory can be |
| /// used for other purposed. Can contain a nullptr; in this case the set is |
| /// implicitly defined as the complement of #Occupied. |
| isl::union_set Unused; |
| |
| /// { [Element[] -> Zone[]] -> ValInst[] } |
| /// Maps to the known content for each array element at any interval. |
| /// |
| /// Any element/interval can map to multiple known elements. This is due to |
| /// multiple llvm::Value referring to the same content. Examples are |
| /// |
| /// - A value stored and loaded again. The LoadInst represents the same value |
| /// as the StoreInst's value operand. |
| /// |
| /// - A PHINode is equal to any one of the incoming values. In case of |
| /// LCSSA-form, it is always equal to its single incoming value. |
| /// |
| /// Two Knowledges are considered not conflicting if at least one of the known |
| /// values match. Not known values are not stored as an unnamed tuple (as |
| /// #Written does), but maps to nothing. |
| /// |
| /// Known values are usually just defined for #Occupied elements. Knowing |
| /// #Unused contents has no advantage as it can be overwritten. |
| isl::union_map Known; |
| |
| /// { [Element[] -> Scatter[]] -> ValInst[] } |
| /// The write actions currently in the scop or that would be added when |
| /// mapping a scalar. Maps to the value that is written. |
| /// |
| /// Written values that cannot be identified are represented by an unknown |
| /// ValInst[] (an unnamed tuple of 0 dimension). It conflicts with itself. |
| isl::union_map Written; |
| |
| /// Check whether this Knowledge object is well-formed. |
| void checkConsistency() const { |
| #ifndef NDEBUG |
| // Default-initialized object |
| if (Occupied.is_null() && Unused.is_null() && Known.is_null() && |
| Written.is_null()) |
| return; |
| |
| assert(!Occupied.is_null() || !Unused.is_null()); |
| assert(!Known.is_null()); |
| assert(!Written.is_null()); |
| |
| // If not all fields are defined, we cannot derived the universe. |
| if (Occupied.is_null() || Unused.is_null()) |
| return; |
| |
| assert(Occupied.is_disjoint(Unused)); |
| auto Universe = Occupied.unite(Unused); |
| |
| assert(!Known.domain().is_subset(Universe).is_false()); |
| assert(!Written.domain().is_subset(Universe).is_false()); |
| #endif |
| } |
| |
| public: |
| /// Initialize a nullptr-Knowledge. This is only provided for convenience; do |
| /// not use such an object. |
| Knowledge() {} |
| |
| /// Create a new object with the given members. |
| Knowledge(isl::union_set Occupied, isl::union_set Unused, |
| isl::union_map Known, isl::union_map Written) |
| : Occupied(std::move(Occupied)), Unused(std::move(Unused)), |
| Known(std::move(Known)), Written(std::move(Written)) { |
| checkConsistency(); |
| } |
| |
| /// Return whether this object was not default-constructed. |
| bool isUsable() const { |
| return (Occupied.is_null() || Unused.is_null()) && !Known.is_null() && |
| !Written.is_null(); |
| } |
| |
| /// Print the content of this object to @p OS. |
| void print(llvm::raw_ostream &OS, unsigned Indent = 0) const { |
| if (isUsable()) { |
| if (!Occupied.is_null()) |
| OS.indent(Indent) << "Occupied: " << Occupied << "\n"; |
| else |
| OS.indent(Indent) << "Occupied: <Everything else not in Unused>\n"; |
| if (!Unused.is_null()) |
| OS.indent(Indent) << "Unused: " << Unused << "\n"; |
| else |
| OS.indent(Indent) << "Unused: <Everything else not in Occupied>\n"; |
| OS.indent(Indent) << "Known: " << Known << "\n"; |
| OS.indent(Indent) << "Written : " << Written << '\n'; |
| } else { |
| OS.indent(Indent) << "Invalid knowledge\n"; |
| } |
| } |
| |
| /// Combine two knowledges, this and @p That. |
| void learnFrom(Knowledge That) { |
| assert(!isConflicting(*this, That)); |
| assert(!Unused.is_null() && !That.Occupied.is_null()); |
| assert( |
| That.Unused.is_null() && |
| "This function is only prepared to learn occupied elements from That"); |
| assert(Occupied.is_null() && "This function does not implement " |
| "`this->Occupied = " |
| "this->Occupied.unite(That.Occupied);`"); |
| |
| Unused = Unused.subtract(That.Occupied); |
| Known = Known.unite(That.Known); |
| Written = Written.unite(That.Written); |
| |
| checkConsistency(); |
| } |
| |
| /// Determine whether two Knowledges conflict with each other. |
| /// |
| /// In theory @p Existing and @p Proposed are symmetric, but the |
| /// implementation is constrained by the implicit interpretation. That is, @p |
| /// Existing must have #Unused defined (use case 1) and @p Proposed must have |
| /// #Occupied defined (use case 1). |
| /// |
| /// A conflict is defined as non-preserved semantics when they are merged. For |
| /// instance, when for the same array and zone they assume different |
| /// llvm::Values. |
| /// |
| /// @param Existing One of the knowledges with #Unused defined. |
| /// @param Proposed One of the knowledges with #Occupied defined. |
| /// @param OS Dump the conflict reason to this output stream; use |
| /// nullptr to not output anything. |
| /// @param Indent Indention for the conflict reason. |
| /// |
| /// @return True, iff the two knowledges are conflicting. |
| static bool isConflicting(const Knowledge &Existing, |
| const Knowledge &Proposed, |
| llvm::raw_ostream *OS = nullptr, |
| unsigned Indent = 0) { |
| assert(!Existing.Unused.is_null()); |
| assert(!Proposed.Occupied.is_null()); |
| |
| #ifndef NDEBUG |
| if (!Existing.Occupied.is_null() && !Proposed.Unused.is_null()) { |
| auto ExistingUniverse = Existing.Occupied.unite(Existing.Unused); |
| auto ProposedUniverse = Proposed.Occupied.unite(Proposed.Unused); |
| assert(ExistingUniverse.is_equal(ProposedUniverse) && |
| "Both inputs' Knowledges must be over the same universe"); |
| } |
| #endif |
| |
| // Do the Existing and Proposed lifetimes conflict? |
| // |
| // Lifetimes are described as the cross-product of array elements and zone |
| // intervals in which they are alive (the space { [Element[] -> Zone[]] }). |
| // In the following we call this "element/lifetime interval". |
| // |
| // In order to not conflict, one of the following conditions must apply for |
| // each element/lifetime interval: |
| // |
| // 1. If occupied in one of the knowledges, it is unused in the other. |
| // |
| // - or - |
| // |
| // 2. Both contain the same value. |
| // |
| // Instead of partitioning the element/lifetime intervals into a part that |
| // both Knowledges occupy (which requires an expensive subtraction) and for |
| // these to check whether they are known to be the same value, we check only |
| // the second condition and ensure that it also applies when then first |
| // condition is true. This is done by adding a wildcard value to |
| // Proposed.Known and Existing.Unused such that they match as a common known |
| // value. We use the "unknown ValInst" for this purpose. Every |
| // Existing.Unused may match with an unknown Proposed.Occupied because these |
| // never are in conflict with each other. |
| auto ProposedOccupiedAnyVal = makeUnknownForDomain(Proposed.Occupied); |
| auto ProposedValues = Proposed.Known.unite(ProposedOccupiedAnyVal); |
| |
| auto ExistingUnusedAnyVal = makeUnknownForDomain(Existing.Unused); |
| auto ExistingValues = Existing.Known.unite(ExistingUnusedAnyVal); |
| |
| auto MatchingVals = ExistingValues.intersect(ProposedValues); |
| auto Matches = MatchingVals.domain(); |
| |
| // Any Proposed.Occupied must either have a match between the known values |
| // of Existing and Occupied, or be in Existing.Unused. In the latter case, |
| // the previously added "AnyVal" will match each other. |
| if (!Proposed.Occupied.is_subset(Matches)) { |
| if (OS) { |
| auto Conflicting = Proposed.Occupied.subtract(Matches); |
| auto ExistingConflictingKnown = |
| Existing.Known.intersect_domain(Conflicting); |
| auto ProposedConflictingKnown = |
| Proposed.Known.intersect_domain(Conflicting); |
| |
| OS->indent(Indent) << "Proposed lifetime conflicting with Existing's\n"; |
| OS->indent(Indent) << "Conflicting occupied: " << Conflicting << "\n"; |
| if (!ExistingConflictingKnown.is_empty()) |
| OS->indent(Indent) |
| << "Existing Known: " << ExistingConflictingKnown << "\n"; |
| if (!ProposedConflictingKnown.is_empty()) |
| OS->indent(Indent) |
| << "Proposed Known: " << ProposedConflictingKnown << "\n"; |
| } |
| return true; |
| } |
| |
| // Do the writes in Existing conflict with occupied values in Proposed? |
| // |
| // In order to not conflict, it must either write to unused lifetime or |
| // write the same value. To check, we remove the writes that write into |
| // Proposed.Unused (they never conflict) and then see whether the written |
| // value is already in Proposed.Known. If there are multiple known values |
| // and a written value is known under different names, it is enough when one |
| // of the written values (assuming that they are the same value under |
| // different names, e.g. a PHINode and one of the incoming values) matches |
| // one of the known names. |
| // |
| // We convert here the set of lifetimes to actual timepoints. A lifetime is |
| // in conflict with a set of write timepoints, if either a live timepoint is |
| // clearly within the lifetime or if a write happens at the beginning of the |
| // lifetime (where it would conflict with the value that actually writes the |
| // value alive). There is no conflict at the end of a lifetime, as the alive |
| // value will always be read, before it is overwritten again. The last |
| // property holds in Polly for all scalar values and we expect all users of |
| // Knowledge to check this property also for accesses to MemoryKind::Array. |
| auto ProposedFixedDefs = |
| convertZoneToTimepoints(Proposed.Occupied, true, false); |
| auto ProposedFixedKnown = |
| convertZoneToTimepoints(Proposed.Known, isl::dim::in, true, false); |
| |
| auto ExistingConflictingWrites = |
| Existing.Written.intersect_domain(ProposedFixedDefs); |
| auto ExistingConflictingWritesDomain = ExistingConflictingWrites.domain(); |
| |
| auto CommonWrittenVal = |
| ProposedFixedKnown.intersect(ExistingConflictingWrites); |
| auto CommonWrittenValDomain = CommonWrittenVal.domain(); |
| |
| if (!ExistingConflictingWritesDomain.is_subset(CommonWrittenValDomain)) { |
| if (OS) { |
| auto ExistingConflictingWritten = |
| ExistingConflictingWrites.subtract_domain(CommonWrittenValDomain); |
| auto ProposedConflictingKnown = ProposedFixedKnown.subtract_domain( |
| ExistingConflictingWritten.domain()); |
| |
| OS->indent(Indent) |
| << "Proposed a lifetime where there is an Existing write into it\n"; |
| OS->indent(Indent) << "Existing conflicting writes: " |
| << ExistingConflictingWritten << "\n"; |
| if (!ProposedConflictingKnown.is_empty()) |
| OS->indent(Indent) |
| << "Proposed conflicting known: " << ProposedConflictingKnown |
| << "\n"; |
| } |
| return true; |
| } |
| |
| // Do the writes in Proposed conflict with occupied values in Existing? |
| auto ExistingAvailableDefs = |
| convertZoneToTimepoints(Existing.Unused, true, false); |
| auto ExistingKnownDefs = |
| convertZoneToTimepoints(Existing.Known, isl::dim::in, true, false); |
| |
| auto ProposedWrittenDomain = Proposed.Written.domain(); |
| auto KnownIdentical = ExistingKnownDefs.intersect(Proposed.Written); |
| auto IdenticalOrUnused = |
| ExistingAvailableDefs.unite(KnownIdentical.domain()); |
| if (!ProposedWrittenDomain.is_subset(IdenticalOrUnused)) { |
| if (OS) { |
| auto Conflicting = ProposedWrittenDomain.subtract(IdenticalOrUnused); |
| auto ExistingConflictingKnown = |
| ExistingKnownDefs.intersect_domain(Conflicting); |
| auto ProposedConflictingWritten = |
| Proposed.Written.intersect_domain(Conflicting); |
| |
| OS->indent(Indent) << "Proposed writes into range used by Existing\n"; |
| OS->indent(Indent) << "Proposed conflicting writes: " |
| << ProposedConflictingWritten << "\n"; |
| if (!ExistingConflictingKnown.is_empty()) |
| OS->indent(Indent) |
| << "Existing conflicting known: " << ExistingConflictingKnown |
| << "\n"; |
| } |
| return true; |
| } |
| |
| // Does Proposed write at the same time as Existing already does (order of |
| // writes is undefined)? Writing the same value is permitted. |
| auto ExistingWrittenDomain = Existing.Written.domain(); |
| auto BothWritten = |
| Existing.Written.domain().intersect(Proposed.Written.domain()); |
| auto ExistingKnownWritten = filterKnownValInst(Existing.Written); |
| auto ProposedKnownWritten = filterKnownValInst(Proposed.Written); |
| auto CommonWritten = |
| ExistingKnownWritten.intersect(ProposedKnownWritten).domain(); |
| |
| if (!BothWritten.is_subset(CommonWritten)) { |
| if (OS) { |
| auto Conflicting = BothWritten.subtract(CommonWritten); |
| auto ExistingConflictingWritten = |
| Existing.Written.intersect_domain(Conflicting); |
| auto ProposedConflictingWritten = |
| Proposed.Written.intersect_domain(Conflicting); |
| |
| OS->indent(Indent) << "Proposed writes at the same time as an already " |
| "Existing write\n"; |
| OS->indent(Indent) << "Conflicting writes: " << Conflicting << "\n"; |
| if (!ExistingConflictingWritten.is_empty()) |
| OS->indent(Indent) |
| << "Exiting write: " << ExistingConflictingWritten << "\n"; |
| if (!ProposedConflictingWritten.is_empty()) |
| OS->indent(Indent) |
| << "Proposed write: " << ProposedConflictingWritten << "\n"; |
| } |
| return true; |
| } |
| |
| return false; |
| } |
| }; |
| |
| /// Implementation of the DeLICM/DePRE transformation. |
| class DeLICMImpl : public ZoneAlgorithm { |
| private: |
| /// Knowledge before any transformation took place. |
| Knowledge OriginalZone; |
| |
| /// Current knowledge of the SCoP including all already applied |
| /// transformations. |
| Knowledge Zone; |
| |
| /// Number of StoreInsts something can be mapped to. |
| int NumberOfCompatibleTargets = 0; |
| |
| /// The number of StoreInsts to which at least one value or PHI has been |
| /// mapped to. |
| int NumberOfTargetsMapped = 0; |
| |
| /// The number of llvm::Value mapped to some array element. |
| int NumberOfMappedValueScalars = 0; |
| |
| /// The number of PHIs mapped to some array element. |
| int NumberOfMappedPHIScalars = 0; |
| |
| /// Determine whether two knowledges are conflicting with each other. |
| /// |
| /// @see Knowledge::isConflicting |
| bool isConflicting(const Knowledge &Proposed) { |
| raw_ostream *OS = nullptr; |
| LLVM_DEBUG(OS = &llvm::dbgs()); |
| return Knowledge::isConflicting(Zone, Proposed, OS, 4); |
| } |
| |
| /// Determine whether @p SAI is a scalar that can be mapped to an array |
| /// element. |
| bool isMappable(const ScopArrayInfo *SAI) { |
| assert(SAI); |
| |
| if (SAI->isValueKind()) { |
| auto *MA = S->getValueDef(SAI); |
| if (!MA) { |
| LLVM_DEBUG( |
| dbgs() |
| << " Reject because value is read-only within the scop\n"); |
| return false; |
| } |
| |
| // Mapping if value is used after scop is not supported. The code |
| // generator would need to reload the scalar after the scop, but it |
| // does not have the information to where it is mapped to. Only the |
| // MemoryAccesses have that information, not the ScopArrayInfo. |
| auto Inst = MA->getAccessInstruction(); |
| for (auto User : Inst->users()) { |
| if (!isa<Instruction>(User)) |
| return false; |
| auto UserInst = cast<Instruction>(User); |
| |
| if (!S->contains(UserInst)) { |
| LLVM_DEBUG(dbgs() << " Reject because value is escaping\n"); |
| return false; |
| } |
| } |
| |
| return true; |
| } |
| |
| if (SAI->isPHIKind()) { |
| auto *MA = S->getPHIRead(SAI); |
| assert(MA); |
| |
| // Mapping of an incoming block from before the SCoP is not supported by |
| // the code generator. |
| auto PHI = cast<PHINode>(MA->getAccessInstruction()); |
| for (auto Incoming : PHI->blocks()) { |
| if (!S->contains(Incoming)) { |
| LLVM_DEBUG(dbgs() |
| << " Reject because at least one incoming block is " |
| "not in the scop region\n"); |
| return false; |
| } |
| } |
| |
| return true; |
| } |
| |
| LLVM_DEBUG(dbgs() << " Reject ExitPHI or other non-value\n"); |
| return false; |
| } |
| |
| /// Compute the uses of a MemoryKind::Value and its lifetime (from its |
| /// definition to the last use). |
| /// |
| /// @param SAI The ScopArrayInfo representing the value's storage. |
| /// |
| /// @return { DomainDef[] -> DomainUse[] }, { DomainDef[] -> Zone[] } |
| /// First element is the set of uses for each definition. |
| /// The second is the lifetime of each definition. |
| std::tuple<isl::union_map, isl::map> |
| computeValueUses(const ScopArrayInfo *SAI) { |
| assert(SAI->isValueKind()); |
| |
| // { DomainRead[] } |
| auto Reads = makeEmptyUnionSet(); |
| |
| // Find all uses. |
| for (auto *MA : S->getValueUses(SAI)) |
| Reads = Reads.unite(getDomainFor(MA)); |
| |
| // { DomainRead[] -> Scatter[] } |
| auto ReadSchedule = getScatterFor(Reads); |
| |
| auto *DefMA = S->getValueDef(SAI); |
| assert(DefMA); |
| |
| // { DomainDef[] } |
| auto Writes = getDomainFor(DefMA); |
| |
| // { DomainDef[] -> Scatter[] } |
| auto WriteScatter = getScatterFor(Writes); |
| |
| // { Scatter[] -> DomainDef[] } |
| auto ReachDef = getScalarReachingDefinition(DefMA->getStatement()); |
| |
| // { [DomainDef[] -> Scatter[]] -> DomainUse[] } |
| auto Uses = isl::union_map(ReachDef.reverse().range_map()) |
| .apply_range(ReadSchedule.reverse()); |
| |
| // { DomainDef[] -> Scatter[] } |
| auto UseScatter = |
| singleton(Uses.domain().unwrap(), |
| Writes.get_space().map_from_domain_and_range(ScatterSpace)); |
| |
| // { DomainDef[] -> Zone[] } |
| auto Lifetime = betweenScatter(WriteScatter, UseScatter, false, true); |
| |
| // { DomainDef[] -> DomainRead[] } |
| auto DefUses = Uses.domain_factor_domain(); |
| |
| return std::make_pair(DefUses, Lifetime); |
| } |
| |
| /// Try to map a MemoryKind::Value to a given array element. |
| /// |
| /// @param SAI Representation of the scalar's memory to map. |
| /// @param TargetElt { Scatter[] -> Element[] } |
| /// Suggestion where to map a scalar to when at a timepoint. |
| /// |
| /// @return true if the scalar was successfully mapped. |
| bool tryMapValue(const ScopArrayInfo *SAI, isl::map TargetElt) { |
| assert(SAI->isValueKind()); |
| |
| auto *DefMA = S->getValueDef(SAI); |
| assert(DefMA->isValueKind()); |
| assert(DefMA->isMustWrite()); |
| auto *V = DefMA->getAccessValue(); |
| auto *DefInst = DefMA->getAccessInstruction(); |
| |
| // Stop if the scalar has already been mapped. |
| if (!DefMA->getLatestScopArrayInfo()->isValueKind()) |
| return false; |
| |
| // { DomainDef[] -> Scatter[] } |
| auto DefSched = getScatterFor(DefMA); |
| |
| // Where each write is mapped to, according to the suggestion. |
| // { DomainDef[] -> Element[] } |
| auto DefTarget = TargetElt.apply_domain(DefSched.reverse()); |
| simplify(DefTarget); |
| LLVM_DEBUG(dbgs() << " Def Mapping: " << DefTarget << '\n'); |
| |
| auto OrigDomain = getDomainFor(DefMA); |
| auto MappedDomain = DefTarget.domain(); |
| if (!OrigDomain.is_subset(MappedDomain)) { |
| LLVM_DEBUG( |
| dbgs() |
| << " Reject because mapping does not encompass all instances\n"); |
| return false; |
| } |
| |
| // { DomainDef[] -> Zone[] } |
| isl::map Lifetime; |
| |
| // { DomainDef[] -> DomainUse[] } |
| isl::union_map DefUses; |
| |
| std::tie(DefUses, Lifetime) = computeValueUses(SAI); |
| LLVM_DEBUG(dbgs() << " Lifetime: " << Lifetime << '\n'); |
| |
| /// { [Element[] -> Zone[]] } |
| auto EltZone = Lifetime.apply_domain(DefTarget).wrap(); |
| simplify(EltZone); |
| |
| // When known knowledge is disabled, just return the unknown value. It will |
| // either get filtered out or conflict with itself. |
| // { DomainDef[] -> ValInst[] } |
| isl::map ValInst; |
| if (DelicmComputeKnown) |
| ValInst = makeValInst(V, DefMA->getStatement(), |
| LI->getLoopFor(DefInst->getParent())); |
| else |
| ValInst = makeUnknownForDomain(DefMA->getStatement()); |
| |
| // { DomainDef[] -> [Element[] -> Zone[]] } |
| auto EltKnownTranslator = DefTarget.range_product(Lifetime); |
| |
| // { [Element[] -> Zone[]] -> ValInst[] } |
| auto EltKnown = ValInst.apply_domain(EltKnownTranslator); |
| simplify(EltKnown); |
| |
| // { DomainDef[] -> [Element[] -> Scatter[]] } |
| auto WrittenTranslator = DefTarget.range_product(DefSched); |
| |
| // { [Element[] -> Scatter[]] -> ValInst[] } |
| auto DefEltSched = ValInst.apply_domain(WrittenTranslator); |
| simplify(DefEltSched); |
| |
| Knowledge Proposed(EltZone, {}, filterKnownValInst(EltKnown), DefEltSched); |
| if (isConflicting(Proposed)) |
| return false; |
| |
| // { DomainUse[] -> Element[] } |
| auto UseTarget = DefUses.reverse().apply_range(DefTarget); |
| |
| mapValue(SAI, std::move(DefTarget), std::move(UseTarget), |
| std::move(Lifetime), std::move(Proposed)); |
| return true; |
| } |
| |
| /// After a scalar has been mapped, update the global knowledge. |
| void applyLifetime(Knowledge Proposed) { |
| Zone.learnFrom(std::move(Proposed)); |
| } |
| |
| /// Map a MemoryKind::Value scalar to an array element. |
| /// |
| /// Callers must have ensured that the mapping is valid and not conflicting. |
| /// |
| /// @param SAI The ScopArrayInfo representing the scalar's memory to |
| /// map. |
| /// @param DefTarget { DomainDef[] -> Element[] } |
| /// The array element to map the scalar to. |
| /// @param UseTarget { DomainUse[] -> Element[] } |
| /// The array elements the uses are mapped to. |
| /// @param Lifetime { DomainDef[] -> Zone[] } |
| /// The lifetime of each llvm::Value definition for |
| /// reporting. |
| /// @param Proposed Mapping constraints for reporting. |
| void mapValue(const ScopArrayInfo *SAI, isl::map DefTarget, |
| isl::union_map UseTarget, isl::map Lifetime, |
| Knowledge Proposed) { |
| // Redirect the read accesses. |
| for (auto *MA : S->getValueUses(SAI)) { |
| // { DomainUse[] } |
| auto Domain = getDomainFor(MA); |
| |
| // { DomainUse[] -> Element[] } |
| auto NewAccRel = UseTarget.intersect_domain(Domain); |
| simplify(NewAccRel); |
| |
| assert(isl_union_map_n_map(NewAccRel.get()) == 1); |
| MA->setNewAccessRelation(isl::map::from_union_map(NewAccRel)); |
| } |
| |
| auto *WA = S->getValueDef(SAI); |
| WA->setNewAccessRelation(DefTarget); |
| applyLifetime(Proposed); |
| |
| MappedValueScalars++; |
| NumberOfMappedValueScalars += 1; |
| } |
| |
| isl::map makeValInst(Value *Val, ScopStmt *UserStmt, Loop *Scope, |
| bool IsCertain = true) { |
| // When known knowledge is disabled, just return the unknown value. It will |
| // either get filtered out or conflict with itself. |
| if (!DelicmComputeKnown) |
| return makeUnknownForDomain(UserStmt); |
| return ZoneAlgorithm::makeValInst(Val, UserStmt, Scope, IsCertain); |
| } |
| |
| /// Express the incoming values of a PHI for each incoming statement in an |
| /// isl::union_map. |
| /// |
| /// @param SAI The PHI scalar represented by a ScopArrayInfo. |
| /// |
| /// @return { PHIWriteDomain[] -> ValInst[] } |
| isl::union_map determinePHIWrittenValues(const ScopArrayInfo *SAI) { |
| auto Result = makeEmptyUnionMap(); |
| |
| // Collect the incoming values. |
| for (auto *MA : S->getPHIIncomings(SAI)) { |
| // { DomainWrite[] -> ValInst[] } |
| isl::union_map ValInst; |
| auto *WriteStmt = MA->getStatement(); |
| |
| auto Incoming = MA->getIncoming(); |
| assert(!Incoming.empty()); |
| if (Incoming.size() == 1) { |
| ValInst = makeValInst(Incoming[0].second, WriteStmt, |
| LI->getLoopFor(Incoming[0].first)); |
| } else { |
| // If the PHI is in a subregion's exit node it can have multiple |
| // incoming values (+ maybe another incoming edge from an unrelated |
| // block). We cannot directly represent it as a single llvm::Value. |
| // We currently model it as unknown value, but modeling as the PHIInst |
| // itself could be OK, too. |
| ValInst = makeUnknownForDomain(WriteStmt); |
| } |
| |
| Result = Result.unite(ValInst); |
| } |
| |
| assert(Result.is_single_valued() && |
| "Cannot have multiple incoming values for same incoming statement"); |
| return Result; |
| } |
| |
| /// Try to map a MemoryKind::PHI scalar to a given array element. |
| /// |
| /// @param SAI Representation of the scalar's memory to map. |
| /// @param TargetElt { Scatter[] -> Element[] } |
| /// Suggestion where to map the scalar to when at a |
| /// timepoint. |
| /// |
| /// @return true if the PHI scalar has been mapped. |
| bool tryMapPHI(const ScopArrayInfo *SAI, isl::map TargetElt) { |
| auto *PHIRead = S->getPHIRead(SAI); |
| assert(PHIRead->isPHIKind()); |
| assert(PHIRead->isRead()); |
| |
| // Skip if already been mapped. |
| if (!PHIRead->getLatestScopArrayInfo()->isPHIKind()) |
| return false; |
| |
| // { DomainRead[] -> Scatter[] } |
| auto PHISched = getScatterFor(PHIRead); |
| |
| // { DomainRead[] -> Element[] } |
| auto PHITarget = PHISched.apply_range(TargetElt); |
| simplify(PHITarget); |
| LLVM_DEBUG(dbgs() << " Mapping: " << PHITarget << '\n'); |
| |
| auto OrigDomain = getDomainFor(PHIRead); |
| auto MappedDomain = PHITarget.domain(); |
| if (!OrigDomain.is_subset(MappedDomain)) { |
| LLVM_DEBUG( |
| dbgs() |
| << " Reject because mapping does not encompass all instances\n"); |
| return false; |
| } |
| |
| // { DomainRead[] -> DomainWrite[] } |
| auto PerPHIWrites = computePerPHI(SAI); |
| if (PerPHIWrites.is_null()) { |
| LLVM_DEBUG( |
| dbgs() << " Reject because cannot determine incoming values\n"); |
| return false; |
| } |
| |
| // { DomainWrite[] -> Element[] } |
| auto WritesTarget = PerPHIWrites.apply_domain(PHITarget).reverse(); |
| simplify(WritesTarget); |
| |
| // { DomainWrite[] } |
| auto UniverseWritesDom = isl::union_set::empty(ParamSpace.ctx()); |
| |
| for (auto *MA : S->getPHIIncomings(SAI)) |
| UniverseWritesDom = UniverseWritesDom.unite(getDomainFor(MA)); |
| |
| auto RelevantWritesTarget = WritesTarget; |
| if (DelicmOverapproximateWrites) |
| WritesTarget = expandMapping(WritesTarget, UniverseWritesDom); |
| |
| auto ExpandedWritesDom = WritesTarget.domain(); |
| if (!DelicmPartialWrites && |
| !UniverseWritesDom.is_subset(ExpandedWritesDom)) { |
| LLVM_DEBUG( |
| dbgs() << " Reject because did not find PHI write mapping for " |
| "all instances\n"); |
| if (DelicmOverapproximateWrites) |
| LLVM_DEBUG(dbgs() << " Relevant Mapping: " |
| << RelevantWritesTarget << '\n'); |
| LLVM_DEBUG(dbgs() << " Deduced Mapping: " << WritesTarget |
| << '\n'); |
| LLVM_DEBUG(dbgs() << " Missing instances: " |
| << UniverseWritesDom.subtract(ExpandedWritesDom) |
| << '\n'); |
| return false; |
| } |
| |
| // { DomainRead[] -> Scatter[] } |
| isl::union_map PerPHIWriteScatterUmap = PerPHIWrites.apply_range(Schedule); |
| isl::map PerPHIWriteScatter = |
| singleton(PerPHIWriteScatterUmap, PHISched.get_space()); |
| |
| // { DomainRead[] -> Zone[] } |
| auto Lifetime = betweenScatter(PerPHIWriteScatter, PHISched, false, true); |
| simplify(Lifetime); |
| LLVM_DEBUG(dbgs() << " Lifetime: " << Lifetime << "\n"); |
| |
| // { DomainWrite[] -> Zone[] } |
| auto WriteLifetime = isl::union_map(Lifetime).apply_domain(PerPHIWrites); |
| |
| // { DomainWrite[] -> ValInst[] } |
| auto WrittenValue = determinePHIWrittenValues(SAI); |
| |
| // { DomainWrite[] -> [Element[] -> Scatter[]] } |
| auto WrittenTranslator = WritesTarget.range_product(Schedule); |
| |
| // { [Element[] -> Scatter[]] -> ValInst[] } |
| auto Written = WrittenValue.apply_domain(WrittenTranslator); |
| simplify(Written); |
| |
| // { DomainWrite[] -> [Element[] -> Zone[]] } |
| auto LifetimeTranslator = WritesTarget.range_product(WriteLifetime); |
| |
| // { DomainWrite[] -> ValInst[] } |
| auto WrittenKnownValue = filterKnownValInst(WrittenValue); |
| |
| // { [Element[] -> Zone[]] -> ValInst[] } |
| auto EltLifetimeInst = WrittenKnownValue.apply_domain(LifetimeTranslator); |
| simplify(EltLifetimeInst); |
| |
| // { [Element[] -> Zone[] } |
| auto Occupied = LifetimeTranslator.range(); |
| simplify(Occupied); |
| |
| Knowledge Proposed(Occupied, {}, EltLifetimeInst, Written); |
| if (isConflicting(Proposed)) |
| return false; |
| |
| mapPHI(SAI, std::move(PHITarget), std::move(WritesTarget), |
| std::move(Lifetime), std::move(Proposed)); |
| return true; |
| } |
| |
| /// Map a MemoryKind::PHI scalar to an array element. |
| /// |
| /// Callers must have ensured that the mapping is valid and not conflicting |
| /// with the common knowledge. |
| /// |
| /// @param SAI The ScopArrayInfo representing the scalar's memory to |
| /// map. |
| /// @param ReadTarget { DomainRead[] -> Element[] } |
| /// The array element to map the scalar to. |
| /// @param WriteTarget { DomainWrite[] -> Element[] } |
| /// New access target for each PHI incoming write. |
| /// @param Lifetime { DomainRead[] -> Zone[] } |
| /// The lifetime of each PHI for reporting. |
| /// @param Proposed Mapping constraints for reporting. |
| void mapPHI(const ScopArrayInfo *SAI, isl::map ReadTarget, |
| isl::union_map WriteTarget, isl::map Lifetime, |
| Knowledge Proposed) { |
| // { Element[] } |
| isl::space ElementSpace = ReadTarget.get_space().range(); |
| |
| // Redirect the PHI incoming writes. |
| for (auto *MA : S->getPHIIncomings(SAI)) { |
| // { DomainWrite[] } |
| auto Domain = getDomainFor(MA); |
| |
| // { DomainWrite[] -> Element[] } |
| auto NewAccRel = WriteTarget.intersect_domain(Domain); |
| simplify(NewAccRel); |
| |
| isl::space NewAccRelSpace = |
| Domain.get_space().map_from_domain_and_range(ElementSpace); |
| isl::map NewAccRelMap = singleton(NewAccRel, NewAccRelSpace); |
| MA->setNewAccessRelation(NewAccRelMap); |
| } |
| |
| // Redirect the PHI read. |
| auto *PHIRead = S->getPHIRead(SAI); |
| PHIRead->setNewAccessRelation(ReadTarget); |
| applyLifetime(Proposed); |
| |
| MappedPHIScalars++; |
| NumberOfMappedPHIScalars++; |
| } |
| |
| /// Search and map scalars to memory overwritten by @p TargetStoreMA. |
| /// |
| /// Start trying to map scalars that are used in the same statement as the |
| /// store. For every successful mapping, try to also map scalars of the |
| /// statements where those are written. Repeat, until no more mapping |
| /// opportunity is found. |
| /// |
| /// There is currently no preference in which order scalars are tried. |
| /// Ideally, we would direct it towards a load instruction of the same array |
| /// element. |
| bool collapseScalarsToStore(MemoryAccess *TargetStoreMA) { |
| assert(TargetStoreMA->isLatestArrayKind()); |
| assert(TargetStoreMA->isMustWrite()); |
| |
| auto TargetStmt = TargetStoreMA->getStatement(); |
| |
| // { DomTarget[] } |
| auto TargetDom = getDomainFor(TargetStmt); |
| |
| // { DomTarget[] -> Element[] } |
| auto TargetAccRel = getAccessRelationFor(TargetStoreMA); |
| |
| // { Zone[] -> DomTarget[] } |
| // For each point in time, find the next target store instance. |
| auto Target = |
| computeScalarReachingOverwrite(Schedule, TargetDom, false, true); |
| |
| // { Zone[] -> Element[] } |
| // Use the target store's write location as a suggestion to map scalars to. |
| auto EltTarget = Target.apply_range(TargetAccRel); |
| simplify(EltTarget); |
| LLVM_DEBUG(dbgs() << " Target mapping is " << EltTarget << '\n'); |
| |
| // Stack of elements not yet processed. |
| SmallVector<MemoryAccess *, 16> Worklist; |
| |
| // Set of scalars already tested. |
| SmallPtrSet<const ScopArrayInfo *, 16> Closed; |
| |
| // Lambda to add all scalar reads to the work list. |
| auto ProcessAllIncoming = [&](ScopStmt *Stmt) { |
| for (auto *MA : *Stmt) { |
| if (!MA->isLatestScalarKind()) |
| continue; |
| if (!MA->isRead()) |
| continue; |
| |
| Worklist.push_back(MA); |
| } |
| }; |
| |
| auto *WrittenVal = TargetStoreMA->getAccessInstruction()->getOperand(0); |
| if (auto *WrittenValInputMA = TargetStmt->lookupInputAccessOf(WrittenVal)) |
| Worklist.push_back(WrittenValInputMA); |
| else |
| ProcessAllIncoming(TargetStmt); |
| |
| auto AnyMapped = false; |
| auto &DL = S->getRegion().getEntry()->getModule()->getDataLayout(); |
| auto StoreSize = |
| DL.getTypeAllocSize(TargetStoreMA->getAccessValue()->getType()); |
| |
| while (!Worklist.empty()) { |
| auto *MA = Worklist.pop_back_val(); |
| |
| auto *SAI = MA->getScopArrayInfo(); |
| if (Closed.count(SAI)) |
| continue; |
| Closed.insert(SAI); |
| LLVM_DEBUG(dbgs() << "\n Trying to map " << MA << " (SAI: " << SAI |
| << ")\n"); |
| |
| // Skip non-mappable scalars. |
| if (!isMappable(SAI)) |
| continue; |
| |
| auto MASize = DL.getTypeAllocSize(MA->getAccessValue()->getType()); |
| if (MASize > StoreSize) { |
| LLVM_DEBUG( |
| dbgs() << " Reject because storage size is insufficient\n"); |
| continue; |
| } |
| |
| // Try to map MemoryKind::Value scalars. |
| if (SAI->isValueKind()) { |
| if (!tryMapValue(SAI, EltTarget)) |
| continue; |
| |
| auto *DefAcc = S->getValueDef(SAI); |
| ProcessAllIncoming(DefAcc->getStatement()); |
| |
| AnyMapped = true; |
| continue; |
| } |
| |
| // Try to map MemoryKind::PHI scalars. |
| if (SAI->isPHIKind()) { |
| if (!tryMapPHI(SAI, EltTarget)) |
| continue; |
| // Add inputs of all incoming statements to the worklist. Prefer the |
| // input accesses of the incoming blocks. |
| for (auto *PHIWrite : S->getPHIIncomings(SAI)) { |
| auto *PHIWriteStmt = PHIWrite->getStatement(); |
| bool FoundAny = false; |
| for (auto Incoming : PHIWrite->getIncoming()) { |
| auto *IncomingInputMA = |
| PHIWriteStmt->lookupInputAccessOf(Incoming.second); |
| if (!IncomingInputMA) |
| continue; |
| |
| Worklist.push_back(IncomingInputMA); |
| FoundAny = true; |
| } |
| |
| if (!FoundAny) |
| ProcessAllIncoming(PHIWrite->getStatement()); |
| } |
| |
| AnyMapped = true; |
| continue; |
| } |
| } |
| |
| if (AnyMapped) { |
| TargetsMapped++; |
| NumberOfTargetsMapped++; |
| } |
| return AnyMapped; |
| } |
| |
| /// Compute when an array element is unused. |
| /// |
| /// @return { [Element[] -> Zone[]] } |
| isl::union_set computeLifetime() const { |
| // { Element[] -> Zone[] } |
| auto ArrayUnused = computeArrayUnused(Schedule, AllMustWrites, AllReads, |
| false, false, true); |
| |
| auto Result = ArrayUnused.wrap(); |
| |
| simplify(Result); |
| return Result; |
| } |
| |
| /// Determine when an array element is written to, and which value instance is |
| /// written. |
| /// |
| /// @return { [Element[] -> Scatter[]] -> ValInst[] } |
| isl::union_map computeWritten() const { |
| // { [Element[] -> Scatter[]] -> ValInst[] } |
| auto EltWritten = applyDomainRange(AllWriteValInst, Schedule); |
| |
| simplify(EltWritten); |
| return EltWritten; |
| } |
| |
| /// Determine whether an access touches at most one element. |
| /// |
| /// The accessed element could be a scalar or accessing an array with constant |
| /// subscript, such that all instances access only that element. |
| /// |
| /// @param MA The access to test. |
| /// |
| /// @return True, if zero or one elements are accessed; False if at least two |
| /// different elements are accessed. |
| bool isScalarAccess(MemoryAccess *MA) { |
| auto Map = getAccessRelationFor(MA); |
| auto Set = Map.range(); |
| return Set.is_singleton(); |
| } |
| |
| /// Print mapping statistics to @p OS. |
| void printStatistics(llvm::raw_ostream &OS, int Indent = 0) const { |
| OS.indent(Indent) << "Statistics {\n"; |
| OS.indent(Indent + 4) << "Compatible overwrites: " |
| << NumberOfCompatibleTargets << "\n"; |
| OS.indent(Indent + 4) << "Overwrites mapped to: " << NumberOfTargetsMapped |
| << '\n'; |
| OS.indent(Indent + 4) << "Value scalars mapped: " |
| << NumberOfMappedValueScalars << '\n'; |
| OS.indent(Indent + 4) << "PHI scalars mapped: " |
| << NumberOfMappedPHIScalars << '\n'; |
| OS.indent(Indent) << "}\n"; |
| } |
| |
| public: |
| DeLICMImpl(Scop *S, LoopInfo *LI) : ZoneAlgorithm("polly-delicm", S, LI) {} |
| |
| /// Calculate the lifetime (definition to last use) of every array element. |
| /// |
| /// @return True if the computed lifetimes (#Zone) is usable. |
| bool computeZone() { |
| // Check that nothing strange occurs. |
| collectCompatibleElts(); |
| |
| isl::union_set EltUnused; |
| isl::union_map EltKnown, EltWritten; |
| |
| { |
| IslMaxOperationsGuard MaxOpGuard(IslCtx.get(), DelicmMaxOps); |
| |
| computeCommon(); |
| |
| EltUnused = computeLifetime(); |
| EltKnown = computeKnown(true, false); |
| EltWritten = computeWritten(); |
| } |
| DeLICMAnalyzed++; |
| |
| if (EltUnused.is_null() || EltKnown.is_null() || EltWritten.is_null()) { |
| assert(isl_ctx_last_error(IslCtx.get()) == isl_error_quota && |
| "The only reason that these things have not been computed should " |
| "be if the max-operations limit hit"); |
| DeLICMOutOfQuota++; |
| LLVM_DEBUG(dbgs() << "DeLICM analysis exceeded max_operations\n"); |
| DebugLoc Begin, End; |
| getDebugLocations(getBBPairForRegion(&S->getRegion()), Begin, End); |
| OptimizationRemarkAnalysis R(DEBUG_TYPE, "OutOfQuota", Begin, |
| S->getEntry()); |
| R << "maximal number of operations exceeded during zone analysis"; |
| S->getFunction().getContext().diagnose(R); |
| return false; |
| } |
| |
| Zone = OriginalZone = Knowledge({}, EltUnused, EltKnown, EltWritten); |
| LLVM_DEBUG(dbgs() << "Computed Zone:\n"; OriginalZone.print(dbgs(), 4)); |
| |
| assert(Zone.isUsable() && OriginalZone.isUsable()); |
| return true; |
| } |
| |
| /// Try to map as many scalars to unused array elements as possible. |
| /// |
| /// Multiple scalars might be mappable to intersecting unused array element |
| /// zones, but we can only chose one. This is a greedy algorithm, therefore |
| /// the first processed element claims it. |
| void greedyCollapse() { |
| bool Modified = false; |
| |
| for (auto &Stmt : *S) { |
| for (auto *MA : Stmt) { |
| if (!MA->isLatestArrayKind()) |
| continue; |
| if (!MA->isWrite()) |
| continue; |
| |
| if (MA->isMayWrite()) { |
| LLVM_DEBUG(dbgs() << "Access " << MA |
| << " pruned because it is a MAY_WRITE\n"); |
| OptimizationRemarkMissed R(DEBUG_TYPE, "TargetMayWrite", |
| MA->getAccessInstruction()); |
| R << "Skipped possible mapping target because it is not an " |
| "unconditional overwrite"; |
| S->getFunction().getContext().diagnose(R); |
| continue; |
| } |
| |
| if (Stmt.getNumIterators() == 0) { |
| LLVM_DEBUG(dbgs() << "Access " << MA |
| << " pruned because it is not in a loop\n"); |
| OptimizationRemarkMissed R(DEBUG_TYPE, "WriteNotInLoop", |
| MA->getAccessInstruction()); |
| R << "skipped possible mapping target because it is not in a loop"; |
| S->getFunction().getContext().diagnose(R); |
| continue; |
| } |
| |
| if (isScalarAccess(MA)) { |
| LLVM_DEBUG(dbgs() |
| << "Access " << MA |
| << " pruned because it writes only a single element\n"); |
| OptimizationRemarkMissed R(DEBUG_TYPE, "ScalarWrite", |
| MA->getAccessInstruction()); |
| R << "skipped possible mapping target because the memory location " |
| "written to does not depend on its outer loop"; |
| S->getFunction().getContext().diagnose(R); |
| continue; |
| } |
| |
| if (!isa<StoreInst>(MA->getAccessInstruction())) { |
| LLVM_DEBUG(dbgs() << "Access " << MA |
| << " pruned because it is not a StoreInst\n"); |
| OptimizationRemarkMissed R(DEBUG_TYPE, "NotAStore", |
| MA->getAccessInstruction()); |
| R << "skipped possible mapping target because non-store instructions " |
| "are not supported"; |
| S->getFunction().getContext().diagnose(R); |
| continue; |
| } |
| |
| // Check for more than one element acces per statement instance. |
| // Currently we expect write accesses to be functional, eg. disallow |
| // |
| // { Stmt[0] -> [i] : 0 <= i < 2 } |
| // |
| // This may occur when some accesses to the element write/read only |
| // parts of the element, eg. a single byte. Polly then divides each |
| // element into subelements of the smallest access length, normal access |
| // then touch multiple of such subelements. It is very common when the |
| // array is accesses with memset, memcpy or memmove which take i8* |
| // arguments. |
| isl::union_map AccRel = MA->getLatestAccessRelation(); |
| if (!AccRel.is_single_valued().is_true()) { |
| LLVM_DEBUG(dbgs() << "Access " << MA |
| << " is incompatible because it writes multiple " |
| "elements per instance\n"); |
| OptimizationRemarkMissed R(DEBUG_TYPE, "NonFunctionalAccRel", |
| MA->getAccessInstruction()); |
| R << "skipped possible mapping target because it writes more than " |
| "one element"; |
| S->getFunction().getContext().diagnose(R); |
| continue; |
| } |
| |
| isl::union_set TouchedElts = AccRel.range(); |
| if (!TouchedElts.is_subset(CompatibleElts)) { |
| LLVM_DEBUG( |
| dbgs() |
| << "Access " << MA |
| << " is incompatible because it touches incompatible elements\n"); |
| OptimizationRemarkMissed R(DEBUG_TYPE, "IncompatibleElts", |
| MA->getAccessInstruction()); |
| R << "skipped possible mapping target because a target location " |
| "cannot be reliably analyzed"; |
| S->getFunction().getContext().diagnose(R); |
| continue; |
| } |
| |
| assert(isCompatibleAccess(MA)); |
| NumberOfCompatibleTargets++; |
| LLVM_DEBUG(dbgs() << "Analyzing target access " << MA << "\n"); |
| if (collapseScalarsToStore(MA)) |
| Modified = true; |
| } |
| } |
| |
| if (Modified) |
| DeLICMScopsModified++; |
| } |
| |
| /// Dump the internal information about a performed DeLICM to @p OS. |
| void print(llvm::raw_ostream &OS, int Indent = 0) { |
| if (!Zone.isUsable()) { |
| OS.indent(Indent) << "Zone not computed\n"; |
| return; |
| } |
| |
| printStatistics(OS, Indent); |
| if (!isModified()) { |
| OS.indent(Indent) << "No modification has been made\n"; |
| return; |
| } |
| printAccesses(OS, Indent); |
| } |
| |
| /// Return whether at least one transformation been applied. |
| bool isModified() const { return NumberOfTargetsMapped > 0; } |
| }; |
| |
| static std::unique_ptr<DeLICMImpl> collapseToUnused(Scop &S, LoopInfo &LI) { |
| std::unique_ptr<DeLICMImpl> Impl = std::make_unique<DeLICMImpl>(&S, &LI); |
| |
| if (!Impl->computeZone()) { |
| LLVM_DEBUG(dbgs() << "Abort because cannot reliably compute lifetimes\n"); |
| return Impl; |
| } |
| |
| LLVM_DEBUG(dbgs() << "Collapsing scalars to unused array elements...\n"); |
| Impl->greedyCollapse(); |
| |
| LLVM_DEBUG(dbgs() << "\nFinal Scop:\n"); |
| LLVM_DEBUG(dbgs() << S); |
| |
| return Impl; |
| } |
| |
| static std::unique_ptr<DeLICMImpl> runDeLICM(Scop &S, LoopInfo &LI) { |
| std::unique_ptr<DeLICMImpl> Impl = collapseToUnused(S, LI); |
| |
| Scop::ScopStatistics ScopStats = S.getStatistics(); |
| NumValueWrites += ScopStats.NumValueWrites; |
| NumValueWritesInLoops += ScopStats.NumValueWritesInLoops; |
| NumPHIWrites += ScopStats.NumPHIWrites; |
| NumPHIWritesInLoops += ScopStats.NumPHIWritesInLoops; |
| NumSingletonWrites += ScopStats.NumSingletonWrites; |
| NumSingletonWritesInLoops += ScopStats.NumSingletonWritesInLoops; |
| |
| return Impl; |
| } |
| |
| static PreservedAnalyses runDeLICMUsingNPM(Scop &S, ScopAnalysisManager &SAM, |
| ScopStandardAnalysisResults &SAR, |
| SPMUpdater &U, raw_ostream *OS) { |
| LoopInfo &LI = SAR.LI; |
| std::unique_ptr<DeLICMImpl> Impl = runDeLICM(S, LI); |
| |
| if (OS) { |
| *OS << "Printing analysis 'Polly - DeLICM/DePRE' for region: '" |
| << S.getName() << "' in function '" << S.getFunction().getName() |
| << "':\n"; |
| if (Impl) { |
| assert(Impl->getScop() == &S); |
| |
| *OS << "DeLICM result:\n"; |
| Impl->print(*OS); |
| } |
| } |
| |
| if (!Impl->isModified()) |
| return PreservedAnalyses::all(); |
| |
| PreservedAnalyses PA; |
| PA.preserveSet<AllAnalysesOn<Module>>(); |
| PA.preserveSet<AllAnalysesOn<Function>>(); |
| PA.preserveSet<AllAnalysesOn<Loop>>(); |
| return PA; |
| } |
| |
| class DeLICMWrapperPass : public ScopPass { |
| private: |
| DeLICMWrapperPass(const DeLICMWrapperPass &) = delete; |
| const DeLICMWrapperPass &operator=(const DeLICMWrapperPass &) = delete; |
| |
| /// The pass implementation, also holding per-scop data. |
| std::unique_ptr<DeLICMImpl> Impl; |
| |
| public: |
| static char ID; |
| explicit DeLICMWrapperPass() : ScopPass(ID) {} |
| |
| virtual void getAnalysisUsage(AnalysisUsage &AU) const override { |
| AU.addRequiredTransitive<ScopInfoRegionPass>(); |
| AU.addRequired<LoopInfoWrapperPass>(); |
| AU.setPreservesAll(); |
| } |
| |
| virtual bool runOnScop(Scop &S) override { |
| // Free resources for previous scop's computation, if not yet done. |
| releaseMemory(); |
| |
| auto &LI = getAnalysis<LoopInfoWrapperPass>().getLoopInfo(); |
| Impl = runDeLICM(S, LI); |
| |
| return Impl->isModified(); |
| } |
| |
| virtual void printScop(raw_ostream &OS, Scop &S) const override { |
| if (!Impl) |
| return; |
| assert(Impl->getScop() == &S); |
| |
| OS << "DeLICM result:\n"; |
| Impl->print(OS); |
| } |
| |
| virtual void releaseMemory() override { Impl.reset(); } |
| }; |
| |
| char DeLICMWrapperPass::ID; |
| } // anonymous namespace |
| |
| Pass *polly::createDeLICMWrapperPass() { return new DeLICMWrapperPass(); } |
| |
| INITIALIZE_PASS_BEGIN(DeLICMWrapperPass, "polly-delicm", "Polly - DeLICM/DePRE", |
| false, false) |
| INITIALIZE_PASS_DEPENDENCY(ScopInfoWrapperPass) |
| INITIALIZE_PASS_DEPENDENCY(LoopInfoWrapperPass) |
| INITIALIZE_PASS_END(DeLICMWrapperPass, "polly-delicm", "Polly - DeLICM/DePRE", |
| false, false) |
| |
| llvm::PreservedAnalyses DeLICMPass::run(Scop &S, ScopAnalysisManager &SAM, |
| ScopStandardAnalysisResults &SAR, |
| SPMUpdater &U) { |
| return runDeLICMUsingNPM(S, SAM, SAR, U, nullptr); |
| } |
| |
| llvm::PreservedAnalyses DeLICMPrinterPass::run(Scop &S, |
| ScopAnalysisManager &SAM, |
| ScopStandardAnalysisResults &SAR, |
| SPMUpdater &U) { |
| return runDeLICMUsingNPM(S, SAM, SAR, U, &OS); |
| } |
| |
| bool polly::isConflicting( |
| isl::union_set ExistingOccupied, isl::union_set ExistingUnused, |
| isl::union_map ExistingKnown, isl::union_map ExistingWrites, |
| isl::union_set ProposedOccupied, isl::union_set ProposedUnused, |
| isl::union_map ProposedKnown, isl::union_map ProposedWrites, |
| llvm::raw_ostream *OS, unsigned Indent) { |
| Knowledge Existing(std::move(ExistingOccupied), std::move(ExistingUnused), |
| std::move(ExistingKnown), std::move(ExistingWrites)); |
| Knowledge Proposed(std::move(ProposedOccupied), std::move(ProposedUnused), |
| std::move(ProposedKnown), std::move(ProposedWrites)); |
| |
| return Knowledge::isConflicting(Existing, Proposed, OS, Indent); |
| } |