/* * Copyright (C) 2016 The Android Open Source Project * * Licensed under the Apache License, Version 2.0 (the "License"); * you may not use this file except in compliance with the License. * You may obtain a copy of the License at * * http://www.apache.org/licenses/LICENSE-2.0 * * Unless required by applicable law or agreed to in writing, software * distributed under the License is distributed on an "AS IS" BASIS, * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. * See the License for the specific language governing permissions and * limitations under the License. */ #include "loop_optimization.h" #include "arch/arm/instruction_set_features_arm.h" #include "arch/arm64/instruction_set_features_arm64.h" #include "arch/instruction_set.h" #include "arch/x86/instruction_set_features_x86.h" #include "arch/x86_64/instruction_set_features_x86_64.h" #include "code_generator.h" #include "driver/compiler_options.h" #include "linear_order.h" #include "mirror/array-inl.h" #include "mirror/string.h" namespace art { // Enables vectorization (SIMDization) in the loop optimizer. static constexpr bool kEnableVectorization = true; // // Static helpers. // // Base alignment for arrays/strings guaranteed by the Android runtime. static uint32_t BaseAlignment() { return kObjectAlignment; } // Hidden offset for arrays/strings guaranteed by the Android runtime. static uint32_t HiddenOffset(DataType::Type type, bool is_string_char_at) { return is_string_char_at ? mirror::String::ValueOffset().Uint32Value() : mirror::Array::DataOffset(DataType::Size(type)).Uint32Value(); } // Remove the instruction from the graph. A bit more elaborate than the usual // instruction removal, since there may be a cycle in the use structure. static void RemoveFromCycle(HInstruction* instruction) { instruction->RemoveAsUserOfAllInputs(); instruction->RemoveEnvironmentUsers(); instruction->GetBlock()->RemoveInstructionOrPhi(instruction, /*ensure_safety=*/ false); RemoveEnvironmentUses(instruction); ResetEnvironmentInputRecords(instruction); } // Detect a goto block and sets succ to the single successor. static bool IsGotoBlock(HBasicBlock* block, /*out*/ HBasicBlock** succ) { if (block->GetPredecessors().size() == 1 && block->GetSuccessors().size() == 1 && block->IsSingleGoto()) { *succ = block->GetSingleSuccessor(); return true; } return false; } // Detect an early exit loop. static bool IsEarlyExit(HLoopInformation* loop_info) { HBlocksInLoopReversePostOrderIterator it_loop(*loop_info); for (it_loop.Advance(); !it_loop.Done(); it_loop.Advance()) { for (HBasicBlock* successor : it_loop.Current()->GetSuccessors()) { if (!loop_info->Contains(*successor)) { return true; } } } return false; } // Forward declaration. static bool IsZeroExtensionAndGet(HInstruction* instruction, DataType::Type type, /*out*/ HInstruction** operand); // Detect a sign extension in instruction from the given type. // Returns the promoted operand on success. static bool IsSignExtensionAndGet(HInstruction* instruction, DataType::Type type, /*out*/ HInstruction** operand) { // Accept any already wider constant that would be handled properly by sign // extension when represented in the *width* of the given narrower data type // (the fact that Uint8/Uint16 normally zero extend does not matter here). int64_t value = 0; if (IsInt64AndGet(instruction, /*out*/ &value)) { switch (type) { case DataType::Type::kUint8: case DataType::Type::kInt8: if (IsInt<8>(value)) { *operand = instruction; return true; } return false; case DataType::Type::kUint16: case DataType::Type::kInt16: if (IsInt<16>(value)) { *operand = instruction; return true; } return false; default: return false; } } // An implicit widening conversion of any signed expression sign-extends. if (instruction->GetType() == type) { switch (type) { case DataType::Type::kInt8: case DataType::Type::kInt16: *operand = instruction; return true; default: return false; } } // An explicit widening conversion of a signed expression sign-extends. if (instruction->IsTypeConversion()) { HInstruction* conv = instruction->InputAt(0); DataType::Type from = conv->GetType(); switch (instruction->GetType()) { case DataType::Type::kInt32: case DataType::Type::kInt64: if (type == from && (from == DataType::Type::kInt8 || from == DataType::Type::kInt16 || from == DataType::Type::kInt32)) { *operand = conv; return true; } return false; case DataType::Type::kInt16: return type == DataType::Type::kUint16 && from == DataType::Type::kUint16 && IsZeroExtensionAndGet(instruction->InputAt(0), type, /*out*/ operand); default: return false; } } return false; } // Detect a zero extension in instruction from the given type. // Returns the promoted operand on success. static bool IsZeroExtensionAndGet(HInstruction* instruction, DataType::Type type, /*out*/ HInstruction** operand) { // Accept any already wider constant that would be handled properly by zero // extension when represented in the *width* of the given narrower data type // (the fact that Int8/Int16 normally sign extend does not matter here). int64_t value = 0; if (IsInt64AndGet(instruction, /*out*/ &value)) { switch (type) { case DataType::Type::kUint8: case DataType::Type::kInt8: if (IsUint<8>(value)) { *operand = instruction; return true; } return false; case DataType::Type::kUint16: case DataType::Type::kInt16: if (IsUint<16>(value)) { *operand = instruction; return true; } return false; default: return false; } } // An implicit widening conversion of any unsigned expression zero-extends. if (instruction->GetType() == type) { switch (type) { case DataType::Type::kUint8: case DataType::Type::kUint16: *operand = instruction; return true; default: return false; } } // An explicit widening conversion of an unsigned expression zero-extends. if (instruction->IsTypeConversion()) { HInstruction* conv = instruction->InputAt(0); DataType::Type from = conv->GetType(); switch (instruction->GetType()) { case DataType::Type::kInt32: case DataType::Type::kInt64: if (type == from && from == DataType::Type::kUint16) { *operand = conv; return true; } return false; case DataType::Type::kUint16: return type == DataType::Type::kInt16 && from == DataType::Type::kInt16 && IsSignExtensionAndGet(instruction->InputAt(0), type, /*out*/ operand); default: return false; } } return false; } // Detect situations with same-extension narrower operands. // Returns true on success and sets is_unsigned accordingly. static bool IsNarrowerOperands(HInstruction* a, HInstruction* b, DataType::Type type, /*out*/ HInstruction** r, /*out*/ HInstruction** s, /*out*/ bool* is_unsigned) { DCHECK(a != nullptr && b != nullptr); // Look for a matching sign extension. DataType::Type stype = HVecOperation::ToSignedType(type); if (IsSignExtensionAndGet(a, stype, r) && IsSignExtensionAndGet(b, stype, s)) { *is_unsigned = false; return true; } // Look for a matching zero extension. DataType::Type utype = HVecOperation::ToUnsignedType(type); if (IsZeroExtensionAndGet(a, utype, r) && IsZeroExtensionAndGet(b, utype, s)) { *is_unsigned = true; return true; } return false; } // As above, single operand. static bool IsNarrowerOperand(HInstruction* a, DataType::Type type, /*out*/ HInstruction** r, /*out*/ bool* is_unsigned) { DCHECK(a != nullptr); // Look for a matching sign extension. DataType::Type stype = HVecOperation::ToSignedType(type); if (IsSignExtensionAndGet(a, stype, r)) { *is_unsigned = false; return true; } // Look for a matching zero extension. DataType::Type utype = HVecOperation::ToUnsignedType(type); if (IsZeroExtensionAndGet(a, utype, r)) { *is_unsigned = true; return true; } return false; } // Compute relative vector length based on type difference. static uint32_t GetOtherVL(DataType::Type other_type, DataType::Type vector_type, uint32_t vl) { DCHECK(DataType::IsIntegralType(other_type)); DCHECK(DataType::IsIntegralType(vector_type)); DCHECK_GE(DataType::SizeShift(other_type), DataType::SizeShift(vector_type)); return vl >> (DataType::SizeShift(other_type) - DataType::SizeShift(vector_type)); } // Detect up to two added operands a and b and an acccumulated constant c. static bool IsAddConst(HInstruction* instruction, /*out*/ HInstruction** a, /*out*/ HInstruction** b, /*out*/ int64_t* c, int32_t depth = 8) { // don't search too deep int64_t value = 0; // Enter add/sub while still within reasonable depth. if (depth > 0) { if (instruction->IsAdd()) { return IsAddConst(instruction->InputAt(0), a, b, c, depth - 1) && IsAddConst(instruction->InputAt(1), a, b, c, depth - 1); } else if (instruction->IsSub() && IsInt64AndGet(instruction->InputAt(1), &value)) { *c -= value; return IsAddConst(instruction->InputAt(0), a, b, c, depth - 1); } } // Otherwise, deal with leaf nodes. if (IsInt64AndGet(instruction, &value)) { *c += value; return true; } else if (*a == nullptr) { *a = instruction; return true; } else if (*b == nullptr) { *b = instruction; return true; } return false; // too many operands } // Detect a + b + c with optional constant c. static bool IsAddConst2(HGraph* graph, HInstruction* instruction, /*out*/ HInstruction** a, /*out*/ HInstruction** b, /*out*/ int64_t* c) { // We want an actual add/sub and not the trivial case where {b: 0, c: 0}. if (IsAddOrSub(instruction) && IsAddConst(instruction, a, b, c) && *a != nullptr) { if (*b == nullptr) { // Constant is usually already present, unless accumulated. *b = graph->GetConstant(instruction->GetType(), (*c)); *c = 0; } return true; } return false; } // Detect a direct a - b or a hidden a - (-c). static bool IsSubConst2(HGraph* graph, HInstruction* instruction, /*out*/ HInstruction** a, /*out*/ HInstruction** b) { int64_t c = 0; if (instruction->IsSub()) { *a = instruction->InputAt(0); *b = instruction->InputAt(1); return true; } else if (IsAddConst(instruction, a, b, &c) && *a != nullptr && *b == nullptr) { // Constant for the hidden subtraction. *b = graph->GetConstant(instruction->GetType(), -c); return true; } return false; } // Detect reductions of the following forms, // x = x_phi + .. // x = x_phi - .. static bool HasReductionFormat(HInstruction* reduction, HInstruction* phi) { if (reduction->IsAdd()) { return (reduction->InputAt(0) == phi && reduction->InputAt(1) != phi) || (reduction->InputAt(0) != phi && reduction->InputAt(1) == phi); } else if (reduction->IsSub()) { return (reduction->InputAt(0) == phi && reduction->InputAt(1) != phi); } return false; } // Translates vector operation to reduction kind. static HVecReduce::ReductionKind GetReductionKind(HVecOperation* reduction) { if (reduction->IsVecAdd() || reduction->IsVecSub() || reduction->IsVecSADAccumulate() || reduction->IsVecDotProd()) { return HVecReduce::kSum; } LOG(FATAL) << "Unsupported SIMD reduction " << reduction->GetId(); UNREACHABLE(); } // Test vector restrictions. static bool HasVectorRestrictions(uint64_t restrictions, uint64_t tested) { return (restrictions & tested) != 0; } // Insert an instruction. static HInstruction* Insert(HBasicBlock* block, HInstruction* instruction) { DCHECK(block != nullptr); DCHECK(instruction != nullptr); block->InsertInstructionBefore(instruction, block->GetLastInstruction()); return instruction; } // Check that instructions from the induction sets are fully removed: have no uses // and no other instructions use them. static bool CheckInductionSetFullyRemoved(ScopedArenaSet* iset) { for (HInstruction* instr : *iset) { if (instr->GetBlock() != nullptr || !instr->GetUses().empty() || !instr->GetEnvUses().empty() || HasEnvironmentUsedByOthers(instr)) { return false; } } return true; } // Tries to statically evaluate condition of the specified "HIf" for other condition checks. static void TryToEvaluateIfCondition(HIf* instruction, HGraph* graph) { HInstruction* cond = instruction->InputAt(0); // If a condition 'cond' is evaluated in an HIf instruction then in the successors of the // IF_BLOCK we statically know the value of the condition 'cond' (TRUE in TRUE_SUCC, FALSE in // FALSE_SUCC). Using that we can replace another evaluation (use) EVAL of the same 'cond' // with TRUE value (FALSE value) if every path from the ENTRY_BLOCK to EVAL_BLOCK contains the // edge HIF_BLOCK->TRUE_SUCC (HIF_BLOCK->FALSE_SUCC). // if (cond) { if(cond) { // if (cond) {} if (1) {} // } else { =======> } else { // if (cond) {} if (0) {} // } } if (!cond->IsConstant()) { HBasicBlock* true_succ = instruction->IfTrueSuccessor(); HBasicBlock* false_succ = instruction->IfFalseSuccessor(); DCHECK_EQ(true_succ->GetPredecessors().size(), 1u); DCHECK_EQ(false_succ->GetPredecessors().size(), 1u); const HUseList& uses = cond->GetUses(); for (auto it = uses.begin(), end = uses.end(); it != end; /* ++it below */) { HInstruction* user = it->GetUser(); size_t index = it->GetIndex(); HBasicBlock* user_block = user->GetBlock(); // Increment `it` now because `*it` may disappear thanks to user->ReplaceInput(). ++it; if (true_succ->Dominates(user_block)) { user->ReplaceInput(graph->GetIntConstant(1), index); } else if (false_succ->Dominates(user_block)) { user->ReplaceInput(graph->GetIntConstant(0), index); } } } } // Peel the first 'count' iterations of the loop. static void PeelByCount(HLoopInformation* loop_info, int count, InductionVarRange* induction_range) { for (int i = 0; i < count; i++) { // Perform peeling. LoopClonerSimpleHelper helper(loop_info, induction_range); helper.DoPeeling(); } } // Returns the narrower type out of instructions a and b types. static DataType::Type GetNarrowerType(HInstruction* a, HInstruction* b) { DataType::Type type = a->GetType(); if (DataType::Size(b->GetType()) < DataType::Size(type)) { type = b->GetType(); } if (a->IsTypeConversion() && DataType::Size(a->InputAt(0)->GetType()) < DataType::Size(type)) { type = a->InputAt(0)->GetType(); } if (b->IsTypeConversion() && DataType::Size(b->InputAt(0)->GetType()) < DataType::Size(type)) { type = b->InputAt(0)->GetType(); } return type; } // // Public methods. // HLoopOptimization::HLoopOptimization(HGraph* graph, const CodeGenerator& codegen, HInductionVarAnalysis* induction_analysis, OptimizingCompilerStats* stats, const char* name) : HOptimization(graph, name, stats), compiler_options_(&codegen.GetCompilerOptions()), simd_register_size_(codegen.GetSIMDRegisterWidth()), induction_range_(induction_analysis), loop_allocator_(nullptr), global_allocator_(graph_->GetAllocator()), top_loop_(nullptr), last_loop_(nullptr), iset_(nullptr), reductions_(nullptr), simplified_(false), vector_length_(0), vector_refs_(nullptr), vector_static_peeling_factor_(0), vector_dynamic_peeling_candidate_(nullptr), vector_runtime_test_a_(nullptr), vector_runtime_test_b_(nullptr), vector_map_(nullptr), vector_permanent_map_(nullptr), vector_mode_(kSequential), vector_preheader_(nullptr), vector_header_(nullptr), vector_body_(nullptr), vector_index_(nullptr), arch_loop_helper_(ArchNoOptsLoopHelper::Create(compiler_options_ != nullptr ? compiler_options_->GetInstructionSet() : InstructionSet::kNone, global_allocator_)) { } bool HLoopOptimization::Run() { // Skip if there is no loop or the graph has try-catch/irreducible loops. // TODO: make this less of a sledgehammer. if (!graph_->HasLoops() || graph_->HasTryCatch() || graph_->HasIrreducibleLoops()) { return false; } // Phase-local allocator. ScopedArenaAllocator allocator(graph_->GetArenaStack()); loop_allocator_ = &allocator; // Perform loop optimizations. bool didLoopOpt = LocalRun(); if (top_loop_ == nullptr) { graph_->SetHasLoops(false); // no more loops } // Detach. loop_allocator_ = nullptr; last_loop_ = top_loop_ = nullptr; return didLoopOpt; } // // Loop setup and traversal. // bool HLoopOptimization::LocalRun() { bool didLoopOpt = false; // Build the linear order using the phase-local allocator. This step enables building // a loop hierarchy that properly reflects the outer-inner and previous-next relation. ScopedArenaVector linear_order(loop_allocator_->Adapter(kArenaAllocLinearOrder)); LinearizeGraph(graph_, &linear_order); // Build the loop hierarchy. for (HBasicBlock* block : linear_order) { if (block->IsLoopHeader()) { AddLoop(block->GetLoopInformation()); } } // Traverse the loop hierarchy inner-to-outer and optimize. Traversal can use // temporary data structures using the phase-local allocator. All new HIR // should use the global allocator. if (top_loop_ != nullptr) { ScopedArenaSet iset(loop_allocator_->Adapter(kArenaAllocLoopOptimization)); ScopedArenaSafeMap reds( std::less(), loop_allocator_->Adapter(kArenaAllocLoopOptimization)); ScopedArenaSet refs(loop_allocator_->Adapter(kArenaAllocLoopOptimization)); ScopedArenaSafeMap map( std::less(), loop_allocator_->Adapter(kArenaAllocLoopOptimization)); ScopedArenaSafeMap perm( std::less(), loop_allocator_->Adapter(kArenaAllocLoopOptimization)); // Attach. iset_ = &iset; reductions_ = &reds; vector_refs_ = &refs; vector_map_ = ↦ vector_permanent_map_ = &perm; // Traverse. didLoopOpt = TraverseLoopsInnerToOuter(top_loop_); // Detach. iset_ = nullptr; reductions_ = nullptr; vector_refs_ = nullptr; vector_map_ = nullptr; vector_permanent_map_ = nullptr; } return didLoopOpt; } void HLoopOptimization::AddLoop(HLoopInformation* loop_info) { DCHECK(loop_info != nullptr); LoopNode* node = new (loop_allocator_) LoopNode(loop_info); if (last_loop_ == nullptr) { // First loop. DCHECK(top_loop_ == nullptr); last_loop_ = top_loop_ = node; } else if (loop_info->IsIn(*last_loop_->loop_info)) { // Inner loop. node->outer = last_loop_; DCHECK(last_loop_->inner == nullptr); last_loop_ = last_loop_->inner = node; } else { // Subsequent loop. while (last_loop_->outer != nullptr && !loop_info->IsIn(*last_loop_->outer->loop_info)) { last_loop_ = last_loop_->outer; } node->outer = last_loop_->outer; node->previous = last_loop_; DCHECK(last_loop_->next == nullptr); last_loop_ = last_loop_->next = node; } } void HLoopOptimization::RemoveLoop(LoopNode* node) { DCHECK(node != nullptr); DCHECK(node->inner == nullptr); if (node->previous != nullptr) { // Within sequence. node->previous->next = node->next; if (node->next != nullptr) { node->next->previous = node->previous; } } else { // First of sequence. if (node->outer != nullptr) { node->outer->inner = node->next; } else { top_loop_ = node->next; } if (node->next != nullptr) { node->next->outer = node->outer; node->next->previous = nullptr; } } } bool HLoopOptimization::TraverseLoopsInnerToOuter(LoopNode* node) { bool changed = false; for ( ; node != nullptr; node = node->next) { // Visit inner loops first. Recompute induction information for this // loop if the induction of any inner loop has changed. if (TraverseLoopsInnerToOuter(node->inner)) { induction_range_.ReVisit(node->loop_info); changed = true; } // Repeat simplifications in the loop-body until no more changes occur. // Note that since each simplification consists of eliminating code (without // introducing new code), this process is always finite. do { simplified_ = false; SimplifyInduction(node); SimplifyBlocks(node); changed = simplified_ || changed; } while (simplified_); // Optimize inner loop. if (node->inner == nullptr) { changed = OptimizeInnerLoop(node) || changed; } } return changed; } // // Optimization. // void HLoopOptimization::SimplifyInduction(LoopNode* node) { HBasicBlock* header = node->loop_info->GetHeader(); HBasicBlock* preheader = node->loop_info->GetPreHeader(); // Scan the phis in the header to find opportunities to simplify an induction // cycle that is only used outside the loop. Replace these uses, if any, with // the last value and remove the induction cycle. // Examples: for (int i = 0; x != null; i++) { .... no i .... } // for (int i = 0; i < 10; i++, k++) { .... no k .... } return k; for (HInstructionIterator it(header->GetPhis()); !it.Done(); it.Advance()) { HPhi* phi = it.Current()->AsPhi(); if (TrySetPhiInduction(phi, /*restrict_uses*/ true) && TryAssignLastValue(node->loop_info, phi, preheader, /*collect_loop_uses*/ false)) { // Note that it's ok to have replaced uses after the loop with the last value, without // being able to remove the cycle. Environment uses (which are the reason we may not be // able to remove the cycle) within the loop will still hold the right value. We must // have tried first, however, to replace outside uses. if (CanRemoveCycle()) { simplified_ = true; for (HInstruction* i : *iset_) { RemoveFromCycle(i); } DCHECK(CheckInductionSetFullyRemoved(iset_)); } } } } void HLoopOptimization::SimplifyBlocks(LoopNode* node) { // Iterate over all basic blocks in the loop-body. for (HBlocksInLoopIterator it(*node->loop_info); !it.Done(); it.Advance()) { HBasicBlock* block = it.Current(); // Remove dead instructions from the loop-body. RemoveDeadInstructions(block->GetPhis()); RemoveDeadInstructions(block->GetInstructions()); // Remove trivial control flow blocks from the loop-body. if (block->GetPredecessors().size() == 1 && block->GetSuccessors().size() == 1 && block->GetSingleSuccessor()->GetPredecessors().size() == 1) { simplified_ = true; block->MergeWith(block->GetSingleSuccessor()); } else if (block->GetSuccessors().size() == 2) { // Trivial if block can be bypassed to either branch. HBasicBlock* succ0 = block->GetSuccessors()[0]; HBasicBlock* succ1 = block->GetSuccessors()[1]; HBasicBlock* meet0 = nullptr; HBasicBlock* meet1 = nullptr; if (succ0 != succ1 && IsGotoBlock(succ0, &meet0) && IsGotoBlock(succ1, &meet1) && meet0 == meet1 && // meets again meet0 != block && // no self-loop meet0->GetPhis().IsEmpty()) { // not used for merging simplified_ = true; succ0->DisconnectAndDelete(); if (block->Dominates(meet0)) { block->RemoveDominatedBlock(meet0); succ1->AddDominatedBlock(meet0); meet0->SetDominator(succ1); } } } } } bool HLoopOptimization::TryOptimizeInnerLoopFinite(LoopNode* node) { HBasicBlock* header = node->loop_info->GetHeader(); HBasicBlock* preheader = node->loop_info->GetPreHeader(); // Ensure loop header logic is finite. int64_t trip_count = 0; if (!induction_range_.IsFinite(node->loop_info, &trip_count)) { return false; } // Ensure there is only a single loop-body (besides the header). HBasicBlock* body = nullptr; for (HBlocksInLoopIterator it(*node->loop_info); !it.Done(); it.Advance()) { if (it.Current() != header) { if (body != nullptr) { return false; } body = it.Current(); } } CHECK(body != nullptr); // Ensure there is only a single exit point. if (header->GetSuccessors().size() != 2) { return false; } HBasicBlock* exit = (header->GetSuccessors()[0] == body) ? header->GetSuccessors()[1] : header->GetSuccessors()[0]; // Ensure exit can only be reached by exiting loop. if (exit->GetPredecessors().size() != 1) { return false; } // Detect either an empty loop (no side effects other than plain iteration) or // a trivial loop (just iterating once). Replace subsequent index uses, if any, // with the last value and remove the loop, possibly after unrolling its body. HPhi* main_phi = nullptr; if (TrySetSimpleLoopHeader(header, &main_phi)) { bool is_empty = IsEmptyBody(body); if (reductions_->empty() && // TODO: possible with some effort (is_empty || trip_count == 1) && TryAssignLastValue(node->loop_info, main_phi, preheader, /*collect_loop_uses*/ true)) { if (!is_empty) { // Unroll the loop-body, which sees initial value of the index. main_phi->ReplaceWith(main_phi->InputAt(0)); preheader->MergeInstructionsWith(body); } body->DisconnectAndDelete(); exit->RemovePredecessor(header); header->RemoveSuccessor(exit); header->RemoveDominatedBlock(exit); header->DisconnectAndDelete(); preheader->AddSuccessor(exit); preheader->AddInstruction(new (global_allocator_) HGoto()); preheader->AddDominatedBlock(exit); exit->SetDominator(preheader); RemoveLoop(node); // update hierarchy return true; } } // Vectorize loop, if possible and valid. if (kEnableVectorization && // Disable vectorization for debuggable graphs: this is a workaround for the bug // in 'GenerateNewLoop' which caused the SuspendCheck environment to be invalid. // TODO: b/138601207, investigate other possible cases with wrong environment values and // possibly switch back vectorization on for debuggable graphs. !graph_->IsDebuggable() && TrySetSimpleLoopHeader(header, &main_phi) && ShouldVectorize(node, body, trip_count) && TryAssignLastValue(node->loop_info, main_phi, preheader, /*collect_loop_uses*/ true)) { Vectorize(node, body, exit, trip_count); graph_->SetHasSIMD(true); // flag SIMD usage MaybeRecordStat(stats_, MethodCompilationStat::kLoopVectorized); return true; } return false; } bool HLoopOptimization::OptimizeInnerLoop(LoopNode* node) { return TryOptimizeInnerLoopFinite(node) || TryPeelingAndUnrolling(node); } // // Scalar loop peeling and unrolling: generic part methods. // bool HLoopOptimization::TryUnrollingForBranchPenaltyReduction(LoopAnalysisInfo* analysis_info, bool generate_code) { if (analysis_info->GetNumberOfExits() > 1) { return false; } uint32_t unrolling_factor = arch_loop_helper_->GetScalarUnrollingFactor(analysis_info); if (unrolling_factor == LoopAnalysisInfo::kNoUnrollingFactor) { return false; } if (generate_code) { // TODO: support other unrolling factors. DCHECK_EQ(unrolling_factor, 2u); // Perform unrolling. HLoopInformation* loop_info = analysis_info->GetLoopInfo(); LoopClonerSimpleHelper helper(loop_info, &induction_range_); helper.DoUnrolling(); // Remove the redundant loop check after unrolling. HIf* copy_hif = helper.GetBasicBlockMap()->Get(loop_info->GetHeader())->GetLastInstruction()->AsIf(); int32_t constant = loop_info->Contains(*copy_hif->IfTrueSuccessor()) ? 1 : 0; copy_hif->ReplaceInput(graph_->GetIntConstant(constant), 0u); } return true; } bool HLoopOptimization::TryPeelingForLoopInvariantExitsElimination(LoopAnalysisInfo* analysis_info, bool generate_code) { HLoopInformation* loop_info = analysis_info->GetLoopInfo(); if (!arch_loop_helper_->IsLoopPeelingEnabled()) { return false; } if (analysis_info->GetNumberOfInvariantExits() == 0) { return false; } if (generate_code) { // Perform peeling. LoopClonerSimpleHelper helper(loop_info, &induction_range_); helper.DoPeeling(); // Statically evaluate loop check after peeling for loop invariant condition. const SuperblockCloner::HInstructionMap* hir_map = helper.GetInstructionMap(); for (auto entry : *hir_map) { HInstruction* copy = entry.second; if (copy->IsIf()) { TryToEvaluateIfCondition(copy->AsIf(), graph_); } } } return true; } bool HLoopOptimization::TryFullUnrolling(LoopAnalysisInfo* analysis_info, bool generate_code) { // Fully unroll loops with a known and small trip count. int64_t trip_count = analysis_info->GetTripCount(); if (!arch_loop_helper_->IsLoopPeelingEnabled() || trip_count == LoopAnalysisInfo::kUnknownTripCount || !arch_loop_helper_->IsFullUnrollingBeneficial(analysis_info)) { return false; } if (generate_code) { // Peeling of the N first iterations (where N equals to the trip count) will effectively // eliminate the loop: after peeling we will have N sequential iterations copied into the loop // preheader and the original loop. The trip count of this loop will be 0 as the sequential // iterations are executed first and there are exactly N of them. Thus we can statically // evaluate the loop exit condition to 'false' and fully eliminate it. // // Here is an example of full unrolling of a loop with a trip count 2: // // loop_cond_1 // loop_body_1 <- First iteration. // | // \ v // ==\ loop_cond_2 // ==/ loop_body_2 <- Second iteration. // / | // <- v <- // loop_cond \ loop_cond \ <- This cond is always false. // loop_body _/ loop_body _/ // HLoopInformation* loop_info = analysis_info->GetLoopInfo(); PeelByCount(loop_info, trip_count, &induction_range_); HIf* loop_hif = loop_info->GetHeader()->GetLastInstruction()->AsIf(); int32_t constant = loop_info->Contains(*loop_hif->IfTrueSuccessor()) ? 0 : 1; loop_hif->ReplaceInput(graph_->GetIntConstant(constant), 0u); } return true; } bool HLoopOptimization::TryPeelingAndUnrolling(LoopNode* node) { HLoopInformation* loop_info = node->loop_info; int64_t trip_count = LoopAnalysis::GetLoopTripCount(loop_info, &induction_range_); LoopAnalysisInfo analysis_info(loop_info); LoopAnalysis::CalculateLoopBasicProperties(loop_info, &analysis_info, trip_count); if (analysis_info.HasInstructionsPreventingScalarOpts() || arch_loop_helper_->IsLoopNonBeneficialForScalarOpts(&analysis_info)) { return false; } if (!TryFullUnrolling(&analysis_info, /*generate_code*/ false) && !TryPeelingForLoopInvariantExitsElimination(&analysis_info, /*generate_code*/ false) && !TryUnrollingForBranchPenaltyReduction(&analysis_info, /*generate_code*/ false)) { return false; } // Run 'IsLoopClonable' the last as it might be time-consuming. if (!LoopClonerHelper::IsLoopClonable(loop_info)) { return false; } return TryFullUnrolling(&analysis_info) || TryPeelingForLoopInvariantExitsElimination(&analysis_info) || TryUnrollingForBranchPenaltyReduction(&analysis_info); } // // Loop vectorization. The implementation is based on the book by Aart J.C. Bik: // "The Software Vectorization Handbook. Applying Multimedia Extensions for Maximum Performance." // Intel Press, June, 2004 (http://www.aartbik.com/). // bool HLoopOptimization::ShouldVectorize(LoopNode* node, HBasicBlock* block, int64_t trip_count) { // Reset vector bookkeeping. vector_length_ = 0; vector_refs_->clear(); vector_static_peeling_factor_ = 0; vector_dynamic_peeling_candidate_ = nullptr; vector_runtime_test_a_ = vector_runtime_test_b_ = nullptr; // Phis in the loop-body prevent vectorization. if (!block->GetPhis().IsEmpty()) { return false; } // Scan the loop-body, starting a right-hand-side tree traversal at each left-hand-side // occurrence, which allows passing down attributes down the use tree. for (HInstructionIterator it(block->GetInstructions()); !it.Done(); it.Advance()) { if (!VectorizeDef(node, it.Current(), /*generate_code*/ false)) { return false; // failure to vectorize a left-hand-side } } // Prepare alignment analysis: // (1) find desired alignment (SIMD vector size in bytes). // (2) initialize static loop peeling votes (peeling factor that will // make one particular reference aligned), never to exceed (1). // (3) variable to record how many references share same alignment. // (4) variable to record suitable candidate for dynamic loop peeling. uint32_t desired_alignment = GetVectorSizeInBytes(); DCHECK_LE(desired_alignment, 16u); uint32_t peeling_votes[16] = { 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0 }; uint32_t max_num_same_alignment = 0; const ArrayReference* peeling_candidate = nullptr; // Data dependence analysis. Find each pair of references with same type, where // at least one is a write. Each such pair denotes a possible data dependence. // This analysis exploits the property that differently typed arrays cannot be // aliased, as well as the property that references either point to the same // array or to two completely disjoint arrays, i.e., no partial aliasing. // Other than a few simply heuristics, no detailed subscript analysis is done. // The scan over references also prepares finding a suitable alignment strategy. for (auto i = vector_refs_->begin(); i != vector_refs_->end(); ++i) { uint32_t num_same_alignment = 0; // Scan over all next references. for (auto j = i; ++j != vector_refs_->end(); ) { if (i->type == j->type && (i->lhs || j->lhs)) { // Found same-typed a[i+x] vs. b[i+y], where at least one is a write. HInstruction* a = i->base; HInstruction* b = j->base; HInstruction* x = i->offset; HInstruction* y = j->offset; if (a == b) { // Found a[i+x] vs. a[i+y]. Accept if x == y (loop-independent data dependence). // Conservatively assume a loop-carried data dependence otherwise, and reject. if (x != y) { return false; } // Count the number of references that have the same alignment (since // base and offset are the same) and where at least one is a write, so // e.g. a[i] = a[i] + b[i] counts a[i] but not b[i]). num_same_alignment++; } else { // Found a[i+x] vs. b[i+y]. Accept if x == y (at worst loop-independent data dependence). // Conservatively assume a potential loop-carried data dependence otherwise, avoided by // generating an explicit a != b disambiguation runtime test on the two references. if (x != y) { // To avoid excessive overhead, we only accept one a != b test. if (vector_runtime_test_a_ == nullptr) { // First test found. vector_runtime_test_a_ = a; vector_runtime_test_b_ = b; } else if ((vector_runtime_test_a_ != a || vector_runtime_test_b_ != b) && (vector_runtime_test_a_ != b || vector_runtime_test_b_ != a)) { return false; // second test would be needed } } } } } // Update information for finding suitable alignment strategy: // (1) update votes for static loop peeling, // (2) update suitable candidate for dynamic loop peeling. Alignment alignment = ComputeAlignment(i->offset, i->type, i->is_string_char_at); if (alignment.Base() >= desired_alignment) { // If the array/string object has a known, sufficient alignment, use the // initial offset to compute the static loop peeling vote (this always // works, since elements have natural alignment). uint32_t offset = alignment.Offset() & (desired_alignment - 1u); uint32_t vote = (offset == 0) ? 0 : ((desired_alignment - offset) >> DataType::SizeShift(i->type)); DCHECK_LT(vote, 16u); ++peeling_votes[vote]; } else if (BaseAlignment() >= desired_alignment && num_same_alignment > max_num_same_alignment) { // Otherwise, if the array/string object has a known, sufficient alignment // for just the base but with an unknown offset, record the candidate with // the most occurrences for dynamic loop peeling (again, the peeling always // works, since elements have natural alignment). max_num_same_alignment = num_same_alignment; peeling_candidate = &(*i); } } // for i // Find a suitable alignment strategy. SetAlignmentStrategy(peeling_votes, peeling_candidate); // Does vectorization seem profitable? if (!IsVectorizationProfitable(trip_count)) { return false; } // Success! return true; } void HLoopOptimization::Vectorize(LoopNode* node, HBasicBlock* block, HBasicBlock* exit, int64_t trip_count) { HBasicBlock* header = node->loop_info->GetHeader(); HBasicBlock* preheader = node->loop_info->GetPreHeader(); // Pick a loop unrolling factor for the vector loop. uint32_t unroll = arch_loop_helper_->GetSIMDUnrollingFactor( block, trip_count, MaxNumberPeeled(), vector_length_); uint32_t chunk = vector_length_ * unroll; DCHECK(trip_count == 0 || (trip_count >= MaxNumberPeeled() + chunk)); // A cleanup loop is needed, at least, for any unknown trip count or // for a known trip count with remainder iterations after vectorization. bool needs_cleanup = trip_count == 0 || ((trip_count - vector_static_peeling_factor_) % chunk) != 0; // Adjust vector bookkeeping. HPhi* main_phi = nullptr; bool is_simple_loop_header = TrySetSimpleLoopHeader(header, &main_phi); // refills sets DCHECK(is_simple_loop_header); vector_header_ = header; vector_body_ = block; // Loop induction type. DataType::Type induc_type = main_phi->GetType(); DCHECK(induc_type == DataType::Type::kInt32 || induc_type == DataType::Type::kInt64) << induc_type; // Generate the trip count for static or dynamic loop peeling, if needed: // ptc = ; HInstruction* ptc = nullptr; if (vector_static_peeling_factor_ != 0) { // Static loop peeling for SIMD alignment (using the most suitable // fixed peeling factor found during prior alignment analysis). DCHECK(vector_dynamic_peeling_candidate_ == nullptr); ptc = graph_->GetConstant(induc_type, vector_static_peeling_factor_); } else if (vector_dynamic_peeling_candidate_ != nullptr) { // Dynamic loop peeling for SIMD alignment (using the most suitable // candidate found during prior alignment analysis): // rem = offset % ALIGN; // adjusted as #elements // ptc = rem == 0 ? 0 : (ALIGN - rem); uint32_t shift = DataType::SizeShift(vector_dynamic_peeling_candidate_->type); uint32_t align = GetVectorSizeInBytes() >> shift; uint32_t hidden_offset = HiddenOffset(vector_dynamic_peeling_candidate_->type, vector_dynamic_peeling_candidate_->is_string_char_at); HInstruction* adjusted_offset = graph_->GetConstant(induc_type, hidden_offset >> shift); HInstruction* offset = Insert(preheader, new (global_allocator_) HAdd( induc_type, vector_dynamic_peeling_candidate_->offset, adjusted_offset)); HInstruction* rem = Insert(preheader, new (global_allocator_) HAnd( induc_type, offset, graph_->GetConstant(induc_type, align - 1u))); HInstruction* sub = Insert(preheader, new (global_allocator_) HSub( induc_type, graph_->GetConstant(induc_type, align), rem)); HInstruction* cond = Insert(preheader, new (global_allocator_) HEqual( rem, graph_->GetConstant(induc_type, 0))); ptc = Insert(preheader, new (global_allocator_) HSelect( cond, graph_->GetConstant(induc_type, 0), sub, kNoDexPc)); needs_cleanup = true; // don't know the exact amount } // Generate loop control: // stc = ; // ptc = min(stc, ptc); // vtc = stc - (stc - ptc) % chunk; // i = 0; HInstruction* stc = induction_range_.GenerateTripCount(node->loop_info, graph_, preheader); HInstruction* vtc = stc; if (needs_cleanup) { DCHECK(IsPowerOfTwo(chunk)); HInstruction* diff = stc; if (ptc != nullptr) { if (trip_count == 0) { HInstruction* cond = Insert(preheader, new (global_allocator_) HAboveOrEqual(stc, ptc)); ptc = Insert(preheader, new (global_allocator_) HSelect(cond, ptc, stc, kNoDexPc)); } diff = Insert(preheader, new (global_allocator_) HSub(induc_type, stc, ptc)); } HInstruction* rem = Insert( preheader, new (global_allocator_) HAnd(induc_type, diff, graph_->GetConstant(induc_type, chunk - 1))); vtc = Insert(preheader, new (global_allocator_) HSub(induc_type, stc, rem)); } vector_index_ = graph_->GetConstant(induc_type, 0); // Generate runtime disambiguation test: // vtc = a != b ? vtc : 0; if (vector_runtime_test_a_ != nullptr) { HInstruction* rt = Insert( preheader, new (global_allocator_) HNotEqual(vector_runtime_test_a_, vector_runtime_test_b_)); vtc = Insert(preheader, new (global_allocator_) HSelect(rt, vtc, graph_->GetConstant(induc_type, 0), kNoDexPc)); needs_cleanup = true; } // Generate alignment peeling loop, if needed: // for ( ; i < ptc; i += 1) // // // NOTE: The alignment forced by the peeling loop is preserved even if data is // moved around during suspend checks, since all analysis was based on // nothing more than the Android runtime alignment conventions. if (ptc != nullptr) { vector_mode_ = kSequential; GenerateNewLoop(node, block, graph_->TransformLoopForVectorization(vector_header_, vector_body_, exit), vector_index_, ptc, graph_->GetConstant(induc_type, 1), LoopAnalysisInfo::kNoUnrollingFactor); } // Generate vector loop, possibly further unrolled: // for ( ; i < vtc; i += chunk) // vector_mode_ = kVector; GenerateNewLoop(node, block, graph_->TransformLoopForVectorization(vector_header_, vector_body_, exit), vector_index_, vtc, graph_->GetConstant(induc_type, vector_length_), // increment per unroll unroll); HLoopInformation* vloop = vector_header_->GetLoopInformation(); // Generate cleanup loop, if needed: // for ( ; i < stc; i += 1) // if (needs_cleanup) { vector_mode_ = kSequential; GenerateNewLoop(node, block, graph_->TransformLoopForVectorization(vector_header_, vector_body_, exit), vector_index_, stc, graph_->GetConstant(induc_type, 1), LoopAnalysisInfo::kNoUnrollingFactor); } // Link reductions to their final uses. for (auto i = reductions_->begin(); i != reductions_->end(); ++i) { if (i->first->IsPhi()) { HInstruction* phi = i->first; HInstruction* repl = ReduceAndExtractIfNeeded(i->second); // Deal with regular uses. for (const HUseListNode& use : phi->GetUses()) { induction_range_.Replace(use.GetUser(), phi, repl); // update induction use } phi->ReplaceWith(repl); } } // Remove the original loop by disconnecting the body block // and removing all instructions from the header. block->DisconnectAndDelete(); while (!header->GetFirstInstruction()->IsGoto()) { header->RemoveInstruction(header->GetFirstInstruction()); } // Update loop hierarchy: the old header now resides in the same outer loop // as the old preheader. Note that we don't bother putting sequential // loops back in the hierarchy at this point. header->SetLoopInformation(preheader->GetLoopInformation()); // outward node->loop_info = vloop; } void HLoopOptimization::GenerateNewLoop(LoopNode* node, HBasicBlock* block, HBasicBlock* new_preheader, HInstruction* lo, HInstruction* hi, HInstruction* step, uint32_t unroll) { DCHECK(unroll == 1 || vector_mode_ == kVector); DataType::Type induc_type = lo->GetType(); // Prepare new loop. vector_preheader_ = new_preheader, vector_header_ = vector_preheader_->GetSingleSuccessor(); vector_body_ = vector_header_->GetSuccessors()[1]; HPhi* phi = new (global_allocator_) HPhi(global_allocator_, kNoRegNumber, 0, HPhi::ToPhiType(induc_type)); // Generate header and prepare body. // for (i = lo; i < hi; i += step) // HInstruction* cond = new (global_allocator_) HAboveOrEqual(phi, hi); vector_header_->AddPhi(phi); vector_header_->AddInstruction(cond); vector_header_->AddInstruction(new (global_allocator_) HIf(cond)); vector_index_ = phi; vector_permanent_map_->clear(); // preserved over unrolling for (uint32_t u = 0; u < unroll; u++) { // Generate instruction map. vector_map_->clear(); for (HInstructionIterator it(block->GetInstructions()); !it.Done(); it.Advance()) { bool vectorized_def = VectorizeDef(node, it.Current(), /*generate_code*/ true); DCHECK(vectorized_def); } // Generate body from the instruction map, but in original program order. HEnvironment* env = vector_header_->GetFirstInstruction()->GetEnvironment(); for (HInstructionIterator it(block->GetInstructions()); !it.Done(); it.Advance()) { auto i = vector_map_->find(it.Current()); if (i != vector_map_->end() && !i->second->IsInBlock()) { Insert(vector_body_, i->second); // Deal with instructions that need an environment, such as the scalar intrinsics. if (i->second->NeedsEnvironment()) { i->second->CopyEnvironmentFromWithLoopPhiAdjustment(env, vector_header_); } } } // Generate the induction. vector_index_ = new (global_allocator_) HAdd(induc_type, vector_index_, step); Insert(vector_body_, vector_index_); } // Finalize phi inputs for the reductions (if any). for (auto i = reductions_->begin(); i != reductions_->end(); ++i) { if (!i->first->IsPhi()) { DCHECK(i->second->IsPhi()); GenerateVecReductionPhiInputs(i->second->AsPhi(), i->first); } } // Finalize phi inputs for the loop index. phi->AddInput(lo); phi->AddInput(vector_index_); vector_index_ = phi; } bool HLoopOptimization::VectorizeDef(LoopNode* node, HInstruction* instruction, bool generate_code) { // Accept a left-hand-side array base[index] for // (1) supported vector type, // (2) loop-invariant base, // (3) unit stride index, // (4) vectorizable right-hand-side value. uint64_t restrictions = kNone; // Don't accept expressions that can throw. if (instruction->CanThrow()) { return false; } if (instruction->IsArraySet()) { DataType::Type type = instruction->AsArraySet()->GetComponentType(); HInstruction* base = instruction->InputAt(0); HInstruction* index = instruction->InputAt(1); HInstruction* value = instruction->InputAt(2); HInstruction* offset = nullptr; // For narrow types, explicit type conversion may have been // optimized way, so set the no hi bits restriction here. if (DataType::Size(type) <= 2) { restrictions |= kNoHiBits; } if (TrySetVectorType(type, &restrictions) && node->loop_info->IsDefinedOutOfTheLoop(base) && induction_range_.IsUnitStride(instruction, index, graph_, &offset) && VectorizeUse(node, value, generate_code, type, restrictions)) { if (generate_code) { GenerateVecSub(index, offset); GenerateVecMem(instruction, vector_map_->Get(index), vector_map_->Get(value), offset, type); } else { vector_refs_->insert(ArrayReference(base, offset, type, /*lhs*/ true)); } return true; } return false; } // Accept a left-hand-side reduction for // (1) supported vector type, // (2) vectorizable right-hand-side value. auto redit = reductions_->find(instruction); if (redit != reductions_->end()) { DataType::Type type = instruction->GetType(); // Recognize SAD idiom or direct reduction. if (VectorizeSADIdiom(node, instruction, generate_code, type, restrictions) || VectorizeDotProdIdiom(node, instruction, generate_code, type, restrictions) || (TrySetVectorType(type, &restrictions) && VectorizeUse(node, instruction, generate_code, type, restrictions))) { if (generate_code) { HInstruction* new_red = vector_map_->Get(instruction); vector_permanent_map_->Put(new_red, vector_map_->Get(redit->second)); vector_permanent_map_->Overwrite(redit->second, new_red); } return true; } return false; } // Branch back okay. if (instruction->IsGoto()) { return true; } // Otherwise accept only expressions with no effects outside the immediate loop-body. // Note that actual uses are inspected during right-hand-side tree traversal. return !IsUsedOutsideLoop(node->loop_info, instruction) && !instruction->DoesAnyWrite(); } bool HLoopOptimization::VectorizeUse(LoopNode* node, HInstruction* instruction, bool generate_code, DataType::Type type, uint64_t restrictions) { // Accept anything for which code has already been generated. if (generate_code) { if (vector_map_->find(instruction) != vector_map_->end()) { return true; } } // Continue the right-hand-side tree traversal, passing in proper // types and vector restrictions along the way. During code generation, // all new nodes are drawn from the global allocator. if (node->loop_info->IsDefinedOutOfTheLoop(instruction)) { // Accept invariant use, using scalar expansion. if (generate_code) { GenerateVecInv(instruction, type); } return true; } else if (instruction->IsArrayGet()) { // Deal with vector restrictions. bool is_string_char_at = instruction->AsArrayGet()->IsStringCharAt(); if (is_string_char_at && HasVectorRestrictions(restrictions, kNoStringCharAt)) { return false; } // Accept a right-hand-side array base[index] for // (1) matching vector type (exact match or signed/unsigned integral type of the same size), // (2) loop-invariant base, // (3) unit stride index, // (4) vectorizable right-hand-side value. HInstruction* base = instruction->InputAt(0); HInstruction* index = instruction->InputAt(1); HInstruction* offset = nullptr; if (HVecOperation::ToSignedType(type) == HVecOperation::ToSignedType(instruction->GetType()) && node->loop_info->IsDefinedOutOfTheLoop(base) && induction_range_.IsUnitStride(instruction, index, graph_, &offset)) { if (generate_code) { GenerateVecSub(index, offset); GenerateVecMem(instruction, vector_map_->Get(index), nullptr, offset, type); } else { vector_refs_->insert(ArrayReference(base, offset, type, /*lhs*/ false, is_string_char_at)); } return true; } } else if (instruction->IsPhi()) { // Accept particular phi operations. if (reductions_->find(instruction) != reductions_->end()) { // Deal with vector restrictions. if (HasVectorRestrictions(restrictions, kNoReduction)) { return false; } // Accept a reduction. if (generate_code) { GenerateVecReductionPhi(instruction->AsPhi()); } return true; } // TODO: accept right-hand-side induction? return false; } else if (instruction->IsTypeConversion()) { // Accept particular type conversions. HTypeConversion* conversion = instruction->AsTypeConversion(); HInstruction* opa = conversion->InputAt(0); DataType::Type from = conversion->GetInputType(); DataType::Type to = conversion->GetResultType(); if (DataType::IsIntegralType(from) && DataType::IsIntegralType(to)) { uint32_t size_vec = DataType::Size(type); uint32_t size_from = DataType::Size(from); uint32_t size_to = DataType::Size(to); // Accept an integral conversion // (1a) narrowing into vector type, "wider" operations cannot bring in higher order bits, or // (1b) widening from at least vector type, and // (2) vectorizable operand. if ((size_to < size_from && size_to == size_vec && VectorizeUse(node, opa, generate_code, type, restrictions | kNoHiBits)) || (size_to >= size_from && size_from >= size_vec && VectorizeUse(node, opa, generate_code, type, restrictions))) { if (generate_code) { if (vector_mode_ == kVector) { vector_map_->Put(instruction, vector_map_->Get(opa)); // operand pass-through } else { GenerateVecOp(instruction, vector_map_->Get(opa), nullptr, type); } } return true; } } else if (to == DataType::Type::kFloat32 && from == DataType::Type::kInt32) { DCHECK_EQ(to, type); // Accept int to float conversion for // (1) supported int, // (2) vectorizable operand. if (TrySetVectorType(from, &restrictions) && VectorizeUse(node, opa, generate_code, from, restrictions)) { if (generate_code) { GenerateVecOp(instruction, vector_map_->Get(opa), nullptr, type); } return true; } } return false; } else if (instruction->IsNeg() || instruction->IsNot() || instruction->IsBooleanNot()) { // Accept unary operator for vectorizable operand. HInstruction* opa = instruction->InputAt(0); if (VectorizeUse(node, opa, generate_code, type, restrictions)) { if (generate_code) { GenerateVecOp(instruction, vector_map_->Get(opa), nullptr, type); } return true; } } else if (instruction->IsAdd() || instruction->IsSub() || instruction->IsMul() || instruction->IsDiv() || instruction->IsAnd() || instruction->IsOr() || instruction->IsXor()) { // Deal with vector restrictions. if ((instruction->IsMul() && HasVectorRestrictions(restrictions, kNoMul)) || (instruction->IsDiv() && HasVectorRestrictions(restrictions, kNoDiv))) { return false; } // Accept binary operator for vectorizable operands. HInstruction* opa = instruction->InputAt(0); HInstruction* opb = instruction->InputAt(1); if (VectorizeUse(node, opa, generate_code, type, restrictions) && VectorizeUse(node, opb, generate_code, type, restrictions)) { if (generate_code) { GenerateVecOp(instruction, vector_map_->Get(opa), vector_map_->Get(opb), type); } return true; } } else if (instruction->IsShl() || instruction->IsShr() || instruction->IsUShr()) { // Recognize halving add idiom. if (VectorizeHalvingAddIdiom(node, instruction, generate_code, type, restrictions)) { return true; } // Deal with vector restrictions. HInstruction* opa = instruction->InputAt(0); HInstruction* opb = instruction->InputAt(1); HInstruction* r = opa; bool is_unsigned = false; if ((HasVectorRestrictions(restrictions, kNoShift)) || (instruction->IsShr() && HasVectorRestrictions(restrictions, kNoShr))) { return false; // unsupported instruction } else if (HasVectorRestrictions(restrictions, kNoHiBits)) { // Shifts right need extra care to account for higher order bits. // TODO: less likely shr/unsigned and ushr/signed can by flipping signess. if (instruction->IsShr() && (!IsNarrowerOperand(opa, type, &r, &is_unsigned) || is_unsigned)) { return false; // reject, unless all operands are sign-extension narrower } else if (instruction->IsUShr() && (!IsNarrowerOperand(opa, type, &r, &is_unsigned) || !is_unsigned)) { return false; // reject, unless all operands are zero-extension narrower } } // Accept shift operator for vectorizable/invariant operands. // TODO: accept symbolic, albeit loop invariant shift factors. DCHECK(r != nullptr); if (generate_code && vector_mode_ != kVector) { // de-idiom r = opa; } int64_t distance = 0; if (VectorizeUse(node, r, generate_code, type, restrictions) && IsInt64AndGet(opb, /*out*/ &distance)) { // Restrict shift distance to packed data type width. int64_t max_distance = DataType::Size(type) * 8; if (0 <= distance && distance < max_distance) { if (generate_code) { GenerateVecOp(instruction, vector_map_->Get(r), opb, type); } return true; } } } else if (instruction->IsAbs()) { // Deal with vector restrictions. HInstruction* opa = instruction->InputAt(0); HInstruction* r = opa; bool is_unsigned = false; if (HasVectorRestrictions(restrictions, kNoAbs)) { return false; } else if (HasVectorRestrictions(restrictions, kNoHiBits) && (!IsNarrowerOperand(opa, type, &r, &is_unsigned) || is_unsigned)) { return false; // reject, unless operand is sign-extension narrower } // Accept ABS(x) for vectorizable operand. DCHECK(r != nullptr); if (generate_code && vector_mode_ != kVector) { // de-idiom r = opa; } if (VectorizeUse(node, r, generate_code, type, restrictions)) { if (generate_code) { GenerateVecOp(instruction, vector_map_->Get(r), nullptr, HVecOperation::ToProperType(type, is_unsigned)); } return true; } } return false; } uint32_t HLoopOptimization::GetVectorSizeInBytes() { if (kIsDebugBuild) { InstructionSet isa = compiler_options_->GetInstructionSet(); // TODO: Remove this check when there are no implicit assumptions on the SIMD reg size. DCHECK_EQ(simd_register_size_, (isa == InstructionSet::kArm || isa == InstructionSet::kThumb2) ? 8u : 16u); } return simd_register_size_; } bool HLoopOptimization::TrySetVectorType(DataType::Type type, uint64_t* restrictions) { const InstructionSetFeatures* features = compiler_options_->GetInstructionSetFeatures(); switch (compiler_options_->GetInstructionSet()) { case InstructionSet::kArm: case InstructionSet::kThumb2: // Allow vectorization for all ARM devices, because Android assumes that // ARM 32-bit always supports advanced SIMD (64-bit SIMD). switch (type) { case DataType::Type::kBool: case DataType::Type::kUint8: case DataType::Type::kInt8: *restrictions |= kNoDiv | kNoReduction | kNoDotProd; return TrySetVectorLength(type, 8); case DataType::Type::kUint16: case DataType::Type::kInt16: *restrictions |= kNoDiv | kNoStringCharAt | kNoReduction | kNoDotProd; return TrySetVectorLength(type, 4); case DataType::Type::kInt32: *restrictions |= kNoDiv | kNoWideSAD; return TrySetVectorLength(type, 2); default: break; } return false; case InstructionSet::kArm64: // Allow vectorization for all ARM devices, because Android assumes that // ARMv8 AArch64 always supports advanced SIMD (128-bit SIMD). switch (type) { case DataType::Type::kBool: case DataType::Type::kUint8: case DataType::Type::kInt8: *restrictions |= kNoDiv; return TrySetVectorLength(type, 16); case DataType::Type::kUint16: case DataType::Type::kInt16: *restrictions |= kNoDiv; return TrySetVectorLength(type, 8); case DataType::Type::kInt32: *restrictions |= kNoDiv; return TrySetVectorLength(type, 4); case DataType::Type::kInt64: *restrictions |= kNoDiv | kNoMul; return TrySetVectorLength(type, 2); case DataType::Type::kFloat32: *restrictions |= kNoReduction; return TrySetVectorLength(type, 4); case DataType::Type::kFloat64: *restrictions |= kNoReduction; return TrySetVectorLength(type, 2); default: return false; } case InstructionSet::kX86: case InstructionSet::kX86_64: // Allow vectorization for SSE4.1-enabled X86 devices only (128-bit SIMD). if (features->AsX86InstructionSetFeatures()->HasSSE4_1()) { switch (type) { case DataType::Type::kBool: case DataType::Type::kUint8: case DataType::Type::kInt8: *restrictions |= kNoMul | kNoDiv | kNoShift | kNoAbs | kNoSignedHAdd | kNoUnroundedHAdd | kNoSAD | kNoDotProd; return TrySetVectorLength(type, 16); case DataType::Type::kUint16: *restrictions |= kNoDiv | kNoAbs | kNoSignedHAdd | kNoUnroundedHAdd | kNoSAD | kNoDotProd; return TrySetVectorLength(type, 8); case DataType::Type::kInt16: *restrictions |= kNoDiv | kNoAbs | kNoSignedHAdd | kNoUnroundedHAdd | kNoSAD; return TrySetVectorLength(type, 8); case DataType::Type::kInt32: *restrictions |= kNoDiv | kNoSAD; return TrySetVectorLength(type, 4); case DataType::Type::kInt64: *restrictions |= kNoMul | kNoDiv | kNoShr | kNoAbs | kNoSAD; return TrySetVectorLength(type, 2); case DataType::Type::kFloat32: *restrictions |= kNoReduction; return TrySetVectorLength(type, 4); case DataType::Type::kFloat64: *restrictions |= kNoReduction; return TrySetVectorLength(type, 2); default: break; } // switch type } return false; default: return false; } // switch instruction set } bool HLoopOptimization::TrySetVectorLengthImpl(uint32_t length) { DCHECK(IsPowerOfTwo(length) && length >= 2u); // First time set? if (vector_length_ == 0) { vector_length_ = length; } // Different types are acceptable within a loop-body, as long as all the corresponding vector // lengths match exactly to obtain a uniform traversal through the vector iteration space // (idiomatic exceptions to this rule can be handled by further unrolling sub-expressions). return vector_length_ == length; } void HLoopOptimization::GenerateVecInv(HInstruction* org, DataType::Type type) { if (vector_map_->find(org) == vector_map_->end()) { // In scalar code, just use a self pass-through for scalar invariants // (viz. expression remains itself). if (vector_mode_ == kSequential) { vector_map_->Put(org, org); return; } // In vector code, explicit scalar expansion is needed. HInstruction* vector = nullptr; auto it = vector_permanent_map_->find(org); if (it != vector_permanent_map_->end()) { vector = it->second; // reuse during unrolling } else { // Generates ReplicateScalar( (optional_type_conv) org ). HInstruction* input = org; DataType::Type input_type = input->GetType(); if (type != input_type && (type == DataType::Type::kInt64 || input_type == DataType::Type::kInt64)) { input = Insert(vector_preheader_, new (global_allocator_) HTypeConversion(type, input, kNoDexPc)); } vector = new (global_allocator_) HVecReplicateScalar(global_allocator_, input, type, vector_length_, kNoDexPc); vector_permanent_map_->Put(org, Insert(vector_preheader_, vector)); } vector_map_->Put(org, vector); } } void HLoopOptimization::GenerateVecSub(HInstruction* org, HInstruction* offset) { if (vector_map_->find(org) == vector_map_->end()) { HInstruction* subscript = vector_index_; int64_t value = 0; if (!IsInt64AndGet(offset, &value) || value != 0) { subscript = new (global_allocator_) HAdd(DataType::Type::kInt32, subscript, offset); if (org->IsPhi()) { Insert(vector_body_, subscript); // lacks layout placeholder } } vector_map_->Put(org, subscript); } } void HLoopOptimization::GenerateVecMem(HInstruction* org, HInstruction* opa, HInstruction* opb, HInstruction* offset, DataType::Type type) { uint32_t dex_pc = org->GetDexPc(); HInstruction* vector = nullptr; if (vector_mode_ == kVector) { // Vector store or load. bool is_string_char_at = false; HInstruction* base = org->InputAt(0); if (opb != nullptr) { vector = new (global_allocator_) HVecStore( global_allocator_, base, opa, opb, type, org->GetSideEffects(), vector_length_, dex_pc); } else { is_string_char_at = org->AsArrayGet()->IsStringCharAt(); vector = new (global_allocator_) HVecLoad(global_allocator_, base, opa, type, org->GetSideEffects(), vector_length_, is_string_char_at, dex_pc); } // Known (forced/adjusted/original) alignment? if (vector_dynamic_peeling_candidate_ != nullptr) { if (vector_dynamic_peeling_candidate_->offset == offset && // TODO: diffs too? DataType::Size(vector_dynamic_peeling_candidate_->type) == DataType::Size(type) && vector_dynamic_peeling_candidate_->is_string_char_at == is_string_char_at) { vector->AsVecMemoryOperation()->SetAlignment( // forced Alignment(GetVectorSizeInBytes(), 0)); } } else { vector->AsVecMemoryOperation()->SetAlignment( // adjusted/original ComputeAlignment(offset, type, is_string_char_at, vector_static_peeling_factor_)); } } else { // Scalar store or load. DCHECK(vector_mode_ == kSequential); if (opb != nullptr) { DataType::Type component_type = org->AsArraySet()->GetComponentType(); vector = new (global_allocator_) HArraySet( org->InputAt(0), opa, opb, component_type, org->GetSideEffects(), dex_pc); } else { bool is_string_char_at = org->AsArrayGet()->IsStringCharAt(); vector = new (global_allocator_) HArrayGet( org->InputAt(0), opa, org->GetType(), org->GetSideEffects(), dex_pc, is_string_char_at); } } vector_map_->Put(org, vector); } void HLoopOptimization::GenerateVecReductionPhi(HPhi* phi) { DCHECK(reductions_->find(phi) != reductions_->end()); DCHECK(reductions_->Get(phi->InputAt(1)) == phi); HInstruction* vector = nullptr; if (vector_mode_ == kSequential) { HPhi* new_phi = new (global_allocator_) HPhi( global_allocator_, kNoRegNumber, 0, phi->GetType()); vector_header_->AddPhi(new_phi); vector = new_phi; } else { // Link vector reduction back to prior unrolled update, or a first phi. auto it = vector_permanent_map_->find(phi); if (it != vector_permanent_map_->end()) { vector = it->second; } else { HPhi* new_phi = new (global_allocator_) HPhi( global_allocator_, kNoRegNumber, 0, HVecOperation::kSIMDType); vector_header_->AddPhi(new_phi); vector = new_phi; } } vector_map_->Put(phi, vector); } void HLoopOptimization::GenerateVecReductionPhiInputs(HPhi* phi, HInstruction* reduction) { HInstruction* new_phi = vector_map_->Get(phi); HInstruction* new_init = reductions_->Get(phi); HInstruction* new_red = vector_map_->Get(reduction); // Link unrolled vector loop back to new phi. for (; !new_phi->IsPhi(); new_phi = vector_permanent_map_->Get(new_phi)) { DCHECK(new_phi->IsVecOperation()); } // Prepare the new initialization. if (vector_mode_ == kVector) { // Generate a [initial, 0, .., 0] vector for add or // a [initial, initial, .., initial] vector for min/max. HVecOperation* red_vector = new_red->AsVecOperation(); HVecReduce::ReductionKind kind = GetReductionKind(red_vector); uint32_t vector_length = red_vector->GetVectorLength(); DataType::Type type = red_vector->GetPackedType(); if (kind == HVecReduce::ReductionKind::kSum) { new_init = Insert(vector_preheader_, new (global_allocator_) HVecSetScalars(global_allocator_, &new_init, type, vector_length, 1, kNoDexPc)); } else { new_init = Insert(vector_preheader_, new (global_allocator_) HVecReplicateScalar(global_allocator_, new_init, type, vector_length, kNoDexPc)); } } else { new_init = ReduceAndExtractIfNeeded(new_init); } // Set the phi inputs. DCHECK(new_phi->IsPhi()); new_phi->AsPhi()->AddInput(new_init); new_phi->AsPhi()->AddInput(new_red); // New feed value for next phi (safe mutation in iteration). reductions_->find(phi)->second = new_phi; } HInstruction* HLoopOptimization::ReduceAndExtractIfNeeded(HInstruction* instruction) { if (instruction->IsPhi()) { HInstruction* input = instruction->InputAt(1); if (HVecOperation::ReturnsSIMDValue(input)) { DCHECK(!input->IsPhi()); HVecOperation* input_vector = input->AsVecOperation(); uint32_t vector_length = input_vector->GetVectorLength(); DataType::Type type = input_vector->GetPackedType(); HVecReduce::ReductionKind kind = GetReductionKind(input_vector); HBasicBlock* exit = instruction->GetBlock()->GetSuccessors()[0]; // Generate a vector reduction and scalar extract // x = REDUCE( [x_1, .., x_n] ) // y = x_1 // along the exit of the defining loop. HInstruction* reduce = new (global_allocator_) HVecReduce( global_allocator_, instruction, type, vector_length, kind, kNoDexPc); exit->InsertInstructionBefore(reduce, exit->GetFirstInstruction()); instruction = new (global_allocator_) HVecExtractScalar( global_allocator_, reduce, type, vector_length, 0, kNoDexPc); exit->InsertInstructionAfter(instruction, reduce); } } return instruction; } #define GENERATE_VEC(x, y) \ if (vector_mode_ == kVector) { \ vector = (x); \ } else { \ DCHECK(vector_mode_ == kSequential); \ vector = (y); \ } \ break; void HLoopOptimization::GenerateVecOp(HInstruction* org, HInstruction* opa, HInstruction* opb, DataType::Type type) { uint32_t dex_pc = org->GetDexPc(); HInstruction* vector = nullptr; DataType::Type org_type = org->GetType(); switch (org->GetKind()) { case HInstruction::kNeg: DCHECK(opb == nullptr); GENERATE_VEC( new (global_allocator_) HVecNeg(global_allocator_, opa, type, vector_length_, dex_pc), new (global_allocator_) HNeg(org_type, opa, dex_pc)); case HInstruction::kNot: DCHECK(opb == nullptr); GENERATE_VEC( new (global_allocator_) HVecNot(global_allocator_, opa, type, vector_length_, dex_pc), new (global_allocator_) HNot(org_type, opa, dex_pc)); case HInstruction::kBooleanNot: DCHECK(opb == nullptr); GENERATE_VEC( new (global_allocator_) HVecNot(global_allocator_, opa, type, vector_length_, dex_pc), new (global_allocator_) HBooleanNot(opa, dex_pc)); case HInstruction::kTypeConversion: DCHECK(opb == nullptr); GENERATE_VEC( new (global_allocator_) HVecCnv(global_allocator_, opa, type, vector_length_, dex_pc), new (global_allocator_) HTypeConversion(org_type, opa, dex_pc)); case HInstruction::kAdd: GENERATE_VEC( new (global_allocator_) HVecAdd(global_allocator_, opa, opb, type, vector_length_, dex_pc), new (global_allocator_) HAdd(org_type, opa, opb, dex_pc)); case HInstruction::kSub: GENERATE_VEC( new (global_allocator_) HVecSub(global_allocator_, opa, opb, type, vector_length_, dex_pc), new (global_allocator_) HSub(org_type, opa, opb, dex_pc)); case HInstruction::kMul: GENERATE_VEC( new (global_allocator_) HVecMul(global_allocator_, opa, opb, type, vector_length_, dex_pc), new (global_allocator_) HMul(org_type, opa, opb, dex_pc)); case HInstruction::kDiv: GENERATE_VEC( new (global_allocator_) HVecDiv(global_allocator_, opa, opb, type, vector_length_, dex_pc), new (global_allocator_) HDiv(org_type, opa, opb, dex_pc)); case HInstruction::kAnd: GENERATE_VEC( new (global_allocator_) HVecAnd(global_allocator_, opa, opb, type, vector_length_, dex_pc), new (global_allocator_) HAnd(org_type, opa, opb, dex_pc)); case HInstruction::kOr: GENERATE_VEC( new (global_allocator_) HVecOr(global_allocator_, opa, opb, type, vector_length_, dex_pc), new (global_allocator_) HOr(org_type, opa, opb, dex_pc)); case HInstruction::kXor: GENERATE_VEC( new (global_allocator_) HVecXor(global_allocator_, opa, opb, type, vector_length_, dex_pc), new (global_allocator_) HXor(org_type, opa, opb, dex_pc)); case HInstruction::kShl: GENERATE_VEC( new (global_allocator_) HVecShl(global_allocator_, opa, opb, type, vector_length_, dex_pc), new (global_allocator_) HShl(org_type, opa, opb, dex_pc)); case HInstruction::kShr: GENERATE_VEC( new (global_allocator_) HVecShr(global_allocator_, opa, opb, type, vector_length_, dex_pc), new (global_allocator_) HShr(org_type, opa, opb, dex_pc)); case HInstruction::kUShr: GENERATE_VEC( new (global_allocator_) HVecUShr(global_allocator_, opa, opb, type, vector_length_, dex_pc), new (global_allocator_) HUShr(org_type, opa, opb, dex_pc)); case HInstruction::kAbs: DCHECK(opb == nullptr); GENERATE_VEC( new (global_allocator_) HVecAbs(global_allocator_, opa, type, vector_length_, dex_pc), new (global_allocator_) HAbs(org_type, opa, dex_pc)); default: break; } // switch CHECK(vector != nullptr) << "Unsupported SIMD operator"; vector_map_->Put(org, vector); } #undef GENERATE_VEC // // Vectorization idioms. // // Method recognizes the following idioms: // rounding halving add (a + b + 1) >> 1 for unsigned/signed operands a, b // truncated halving add (a + b) >> 1 for unsigned/signed operands a, b // Provided that the operands are promoted to a wider form to do the arithmetic and // then cast back to narrower form, the idioms can be mapped into efficient SIMD // implementation that operates directly in narrower form (plus one extra bit). // TODO: current version recognizes implicit byte/short/char widening only; // explicit widening from int to long could be added later. bool HLoopOptimization::VectorizeHalvingAddIdiom(LoopNode* node, HInstruction* instruction, bool generate_code, DataType::Type type, uint64_t restrictions) { // Test for top level arithmetic shift right x >> 1 or logical shift right x >>> 1 // (note whether the sign bit in wider precision is shifted in has no effect // on the narrow precision computed by the idiom). if ((instruction->IsShr() || instruction->IsUShr()) && IsInt64Value(instruction->InputAt(1), 1)) { // Test for (a + b + c) >> 1 for optional constant c. HInstruction* a = nullptr; HInstruction* b = nullptr; int64_t c = 0; if (IsAddConst2(graph_, instruction->InputAt(0), /*out*/ &a, /*out*/ &b, /*out*/ &c)) { // Accept c == 1 (rounded) or c == 0 (not rounded). bool is_rounded = false; if (c == 1) { is_rounded = true; } else if (c != 0) { return false; } // Accept consistent zero or sign extension on operands a and b. HInstruction* r = nullptr; HInstruction* s = nullptr; bool is_unsigned = false; if (!IsNarrowerOperands(a, b, type, &r, &s, &is_unsigned)) { return false; } // Deal with vector restrictions. if ((!is_unsigned && HasVectorRestrictions(restrictions, kNoSignedHAdd)) || (!is_rounded && HasVectorRestrictions(restrictions, kNoUnroundedHAdd))) { return false; } // Accept recognized halving add for vectorizable operands. Vectorized code uses the // shorthand idiomatic operation. Sequential code uses the original scalar expressions. DCHECK(r != nullptr && s != nullptr); if (generate_code && vector_mode_ != kVector) { // de-idiom r = instruction->InputAt(0); s = instruction->InputAt(1); } if (VectorizeUse(node, r, generate_code, type, restrictions) && VectorizeUse(node, s, generate_code, type, restrictions)) { if (generate_code) { if (vector_mode_ == kVector) { vector_map_->Put(instruction, new (global_allocator_) HVecHalvingAdd( global_allocator_, vector_map_->Get(r), vector_map_->Get(s), HVecOperation::ToProperType(type, is_unsigned), vector_length_, is_rounded, kNoDexPc)); MaybeRecordStat(stats_, MethodCompilationStat::kLoopVectorizedIdiom); } else { GenerateVecOp(instruction, vector_map_->Get(r), vector_map_->Get(s), type); } } return true; } } } return false; } // Method recognizes the following idiom: // q += ABS(a - b) for signed operands a, b // Provided that the operands have the same type or are promoted to a wider form. // Since this may involve a vector length change, the idiom is handled by going directly // to a sad-accumulate node (rather than relying combining finer grained nodes later). // TODO: unsigned SAD too? bool HLoopOptimization::VectorizeSADIdiom(LoopNode* node, HInstruction* instruction, bool generate_code, DataType::Type reduction_type, uint64_t restrictions) { // Filter integral "q += ABS(a - b);" reduction, where ABS and SUB // are done in the same precision (either int or long). if (!instruction->IsAdd() || (reduction_type != DataType::Type::kInt32 && reduction_type != DataType::Type::kInt64)) { return false; } HInstruction* acc = instruction->InputAt(0); HInstruction* abs = instruction->InputAt(1); HInstruction* a = nullptr; HInstruction* b = nullptr; if (abs->IsAbs() && abs->GetType() == reduction_type && IsSubConst2(graph_, abs->InputAt(0), /*out*/ &a, /*out*/ &b)) { DCHECK(a != nullptr && b != nullptr); } else { return false; } // Accept same-type or consistent sign extension for narrower-type on operands a and b. // The same-type or narrower operands are called r (a or lower) and s (b or lower). // We inspect the operands carefully to pick the most suited type. HInstruction* r = a; HInstruction* s = b; bool is_unsigned = false; DataType::Type sub_type = GetNarrowerType(a, b); if (reduction_type != sub_type && (!IsNarrowerOperands(a, b, sub_type, &r, &s, &is_unsigned) || is_unsigned)) { return false; } // Try same/narrower type and deal with vector restrictions. if (!TrySetVectorType(sub_type, &restrictions) || HasVectorRestrictions(restrictions, kNoSAD) || (reduction_type != sub_type && HasVectorRestrictions(restrictions, kNoWideSAD))) { return false; } // Accept SAD idiom for vectorizable operands. Vectorized code uses the shorthand // idiomatic operation. Sequential code uses the original scalar expressions. DCHECK(r != nullptr && s != nullptr); if (generate_code && vector_mode_ != kVector) { // de-idiom r = s = abs->InputAt(0); } if (VectorizeUse(node, acc, generate_code, sub_type, restrictions) && VectorizeUse(node, r, generate_code, sub_type, restrictions) && VectorizeUse(node, s, generate_code, sub_type, restrictions)) { if (generate_code) { if (vector_mode_ == kVector) { vector_map_->Put(instruction, new (global_allocator_) HVecSADAccumulate( global_allocator_, vector_map_->Get(acc), vector_map_->Get(r), vector_map_->Get(s), HVecOperation::ToProperType(reduction_type, is_unsigned), GetOtherVL(reduction_type, sub_type, vector_length_), kNoDexPc)); MaybeRecordStat(stats_, MethodCompilationStat::kLoopVectorizedIdiom); } else { // "GenerateVecOp()" must not be called more than once for each original loop body // instruction. As the SAD idiom processes both "current" instruction ("instruction") // and its ABS input in one go, we must check that for the scalar case the ABS instruction // has not yet been processed. if (vector_map_->find(abs) == vector_map_->end()) { GenerateVecOp(abs, vector_map_->Get(r), nullptr, reduction_type); } GenerateVecOp(instruction, vector_map_->Get(acc), vector_map_->Get(abs), reduction_type); } } return true; } return false; } // Method recognises the following dot product idiom: // q += a * b for operands a, b whose type is narrower than the reduction one. // Provided that the operands have the same type or are promoted to a wider form. // Since this may involve a vector length change, the idiom is handled by going directly // to a dot product node (rather than relying combining finer grained nodes later). bool HLoopOptimization::VectorizeDotProdIdiom(LoopNode* node, HInstruction* instruction, bool generate_code, DataType::Type reduction_type, uint64_t restrictions) { if (!instruction->IsAdd() || reduction_type != DataType::Type::kInt32) { return false; } HInstruction* const acc = instruction->InputAt(0); HInstruction* const mul = instruction->InputAt(1); if (!mul->IsMul() || mul->GetType() != reduction_type) { return false; } HInstruction* const mul_left = mul->InputAt(0); HInstruction* const mul_right = mul->InputAt(1); HInstruction* r = mul_left; HInstruction* s = mul_right; DataType::Type op_type = GetNarrowerType(mul_left, mul_right); bool is_unsigned = false; if (!IsNarrowerOperands(mul_left, mul_right, op_type, &r, &s, &is_unsigned)) { return false; } op_type = HVecOperation::ToProperType(op_type, is_unsigned); if (!TrySetVectorType(op_type, &restrictions) || HasVectorRestrictions(restrictions, kNoDotProd)) { return false; } DCHECK(r != nullptr && s != nullptr); // Accept dot product idiom for vectorizable operands. Vectorized code uses the shorthand // idiomatic operation. Sequential code uses the original scalar expressions. if (generate_code && vector_mode_ != kVector) { // de-idiom r = mul_left; s = mul_right; } if (VectorizeUse(node, acc, generate_code, op_type, restrictions) && VectorizeUse(node, r, generate_code, op_type, restrictions) && VectorizeUse(node, s, generate_code, op_type, restrictions)) { if (generate_code) { if (vector_mode_ == kVector) { vector_map_->Put(instruction, new (global_allocator_) HVecDotProd( global_allocator_, vector_map_->Get(acc), vector_map_->Get(r), vector_map_->Get(s), reduction_type, is_unsigned, GetOtherVL(reduction_type, op_type, vector_length_), kNoDexPc)); MaybeRecordStat(stats_, MethodCompilationStat::kLoopVectorizedIdiom); } else { // "GenerateVecOp()" must not be called more than once for each original loop body // instruction. As the DotProd idiom processes both "current" instruction ("instruction") // and its MUL input in one go, we must check that for the scalar case the MUL instruction // has not yet been processed. if (vector_map_->find(mul) == vector_map_->end()) { GenerateVecOp(mul, vector_map_->Get(r), vector_map_->Get(s), reduction_type); } GenerateVecOp(instruction, vector_map_->Get(acc), vector_map_->Get(mul), reduction_type); } } return true; } return false; } // // Vectorization heuristics. // Alignment HLoopOptimization::ComputeAlignment(HInstruction* offset, DataType::Type type, bool is_string_char_at, uint32_t peeling) { // Combine the alignment and hidden offset that is guaranteed by // the Android runtime with a known starting index adjusted as bytes. int64_t value = 0; if (IsInt64AndGet(offset, /*out*/ &value)) { uint32_t start_offset = HiddenOffset(type, is_string_char_at) + (value + peeling) * DataType::Size(type); return Alignment(BaseAlignment(), start_offset & (BaseAlignment() - 1u)); } // Otherwise, the Android runtime guarantees at least natural alignment. return Alignment(DataType::Size(type), 0); } void HLoopOptimization::SetAlignmentStrategy(uint32_t peeling_votes[], const ArrayReference* peeling_candidate) { // Current heuristic: pick the best static loop peeling factor, if any, // or otherwise use dynamic loop peeling on suggested peeling candidate. uint32_t max_vote = 0; for (int32_t i = 0; i < 16; i++) { if (peeling_votes[i] > max_vote) { max_vote = peeling_votes[i]; vector_static_peeling_factor_ = i; } } if (max_vote == 0) { vector_dynamic_peeling_candidate_ = peeling_candidate; } } uint32_t HLoopOptimization::MaxNumberPeeled() { if (vector_dynamic_peeling_candidate_ != nullptr) { return vector_length_ - 1u; // worst-case } return vector_static_peeling_factor_; // known exactly } bool HLoopOptimization::IsVectorizationProfitable(int64_t trip_count) { // Current heuristic: non-empty body with sufficient number of iterations (if known). // TODO: refine by looking at e.g. operation count, alignment, etc. // TODO: trip count is really unsigned entity, provided the guarding test // is satisfied; deal with this more carefully later uint32_t max_peel = MaxNumberPeeled(); if (vector_length_ == 0) { return false; // nothing found } else if (trip_count < 0) { return false; // guard against non-taken/large } else if ((0 < trip_count) && (trip_count < (vector_length_ + max_peel))) { return false; // insufficient iterations } return true; } // // Helpers. // bool HLoopOptimization::TrySetPhiInduction(HPhi* phi, bool restrict_uses) { // Start with empty phi induction. iset_->clear(); // Special case Phis that have equivalent in a debuggable setup. Our graph checker isn't // smart enough to follow strongly connected components (and it's probably not worth // it to make it so). See b/33775412. if (graph_->IsDebuggable() && phi->HasEquivalentPhi()) { return false; } // Lookup phi induction cycle. ArenaSet* set = induction_range_.LookupCycle(phi); if (set != nullptr) { for (HInstruction* i : *set) { // Check that, other than instructions that are no longer in the graph (removed earlier) // each instruction is removable and, when restrict uses are requested, other than for phi, // all uses are contained within the cycle. if (!i->IsInBlock()) { continue; } else if (!i->IsRemovable()) { return false; } else if (i != phi && restrict_uses) { // Deal with regular uses. for (const HUseListNode& use : i->GetUses()) { if (set->find(use.GetUser()) == set->end()) { return false; } } } iset_->insert(i); // copy } return true; } return false; } bool HLoopOptimization::TrySetPhiReduction(HPhi* phi) { DCHECK(iset_->empty()); // Only unclassified phi cycles are candidates for reductions. if (induction_range_.IsClassified(phi)) { return false; } // Accept operations like x = x + .., provided that the phi and the reduction are // used exactly once inside the loop, and by each other. HInputsRef inputs = phi->GetInputs(); if (inputs.size() == 2) { HInstruction* reduction = inputs[1]; if (HasReductionFormat(reduction, phi)) { HLoopInformation* loop_info = phi->GetBlock()->GetLoopInformation(); uint32_t use_count = 0; bool single_use_inside_loop = // Reduction update only used by phi. reduction->GetUses().HasExactlyOneElement() && !reduction->HasEnvironmentUses() && // Reduction update is only use of phi inside the loop. IsOnlyUsedAfterLoop(loop_info, phi, /*collect_loop_uses*/ true, &use_count) && iset_->size() == 1; iset_->clear(); // leave the way you found it if (single_use_inside_loop) { // Link reduction back, and start recording feed value. reductions_->Put(reduction, phi); reductions_->Put(phi, phi->InputAt(0)); return true; } } } return false; } bool HLoopOptimization::TrySetSimpleLoopHeader(HBasicBlock* block, /*out*/ HPhi** main_phi) { // Start with empty phi induction and reductions. iset_->clear(); reductions_->clear(); // Scan the phis to find the following (the induction structure has already // been optimized, so we don't need to worry about trivial cases): // (1) optional reductions in loop, // (2) the main induction, used in loop control. HPhi* phi = nullptr; for (HInstructionIterator it(block->GetPhis()); !it.Done(); it.Advance()) { if (TrySetPhiReduction(it.Current()->AsPhi())) { continue; } else if (phi == nullptr) { // Found the first candidate for main induction. phi = it.Current()->AsPhi(); } else { return false; } } // Then test for a typical loopheader: // s: SuspendCheck // c: Condition(phi, bound) // i: If(c) if (phi != nullptr && TrySetPhiInduction(phi, /*restrict_uses*/ false)) { HInstruction* s = block->GetFirstInstruction(); if (s != nullptr && s->IsSuspendCheck()) { HInstruction* c = s->GetNext(); if (c != nullptr && c->IsCondition() && c->GetUses().HasExactlyOneElement() && // only used for termination !c->HasEnvironmentUses()) { // unlikely, but not impossible HInstruction* i = c->GetNext(); if (i != nullptr && i->IsIf() && i->InputAt(0) == c) { iset_->insert(c); iset_->insert(s); *main_phi = phi; return true; } } } } return false; } bool HLoopOptimization::IsEmptyBody(HBasicBlock* block) { if (!block->GetPhis().IsEmpty()) { return false; } for (HInstructionIterator it(block->GetInstructions()); !it.Done(); it.Advance()) { HInstruction* instruction = it.Current(); if (!instruction->IsGoto() && iset_->find(instruction) == iset_->end()) { return false; } } return true; } bool HLoopOptimization::IsUsedOutsideLoop(HLoopInformation* loop_info, HInstruction* instruction) { // Deal with regular uses. for (const HUseListNode& use : instruction->GetUses()) { if (use.GetUser()->GetBlock()->GetLoopInformation() != loop_info) { return true; } } return false; } bool HLoopOptimization::IsOnlyUsedAfterLoop(HLoopInformation* loop_info, HInstruction* instruction, bool collect_loop_uses, /*out*/ uint32_t* use_count) { // Deal with regular uses. for (const HUseListNode& use : instruction->GetUses()) { HInstruction* user = use.GetUser(); if (iset_->find(user) == iset_->end()) { // not excluded? HLoopInformation* other_loop_info = user->GetBlock()->GetLoopInformation(); if (other_loop_info != nullptr && other_loop_info->IsIn(*loop_info)) { // If collect_loop_uses is set, simply keep adding those uses to the set. // Otherwise, reject uses inside the loop that were not already in the set. if (collect_loop_uses) { iset_->insert(user); continue; } return false; } ++*use_count; } } return true; } bool HLoopOptimization::TryReplaceWithLastValue(HLoopInformation* loop_info, HInstruction* instruction, HBasicBlock* block) { // Try to replace outside uses with the last value. if (induction_range_.CanGenerateLastValue(instruction)) { HInstruction* replacement = induction_range_.GenerateLastValue(instruction, graph_, block); // Deal with regular uses. const HUseList& uses = instruction->GetUses(); for (auto it = uses.begin(), end = uses.end(); it != end;) { HInstruction* user = it->GetUser(); size_t index = it->GetIndex(); ++it; // increment before replacing if (iset_->find(user) == iset_->end()) { // not excluded? if (kIsDebugBuild) { // We have checked earlier in 'IsOnlyUsedAfterLoop' that the use is after the loop. HLoopInformation* other_loop_info = user->GetBlock()->GetLoopInformation(); CHECK(other_loop_info == nullptr || !other_loop_info->IsIn(*loop_info)); } user->ReplaceInput(replacement, index); induction_range_.Replace(user, instruction, replacement); // update induction } } // Deal with environment uses. const HUseList& env_uses = instruction->GetEnvUses(); for (auto it = env_uses.begin(), end = env_uses.end(); it != end;) { HEnvironment* user = it->GetUser(); size_t index = it->GetIndex(); ++it; // increment before replacing if (iset_->find(user->GetHolder()) == iset_->end()) { // not excluded? // Only update environment uses after the loop. HLoopInformation* other_loop_info = user->GetHolder()->GetBlock()->GetLoopInformation(); if (other_loop_info == nullptr || !other_loop_info->IsIn(*loop_info)) { user->RemoveAsUserOfInput(index); user->SetRawEnvAt(index, replacement); replacement->AddEnvUseAt(user, index); } } } return true; } return false; } bool HLoopOptimization::TryAssignLastValue(HLoopInformation* loop_info, HInstruction* instruction, HBasicBlock* block, bool collect_loop_uses) { // Assigning the last value is always successful if there are no uses. // Otherwise, it succeeds in a no early-exit loop by generating the // proper last value assignment. uint32_t use_count = 0; return IsOnlyUsedAfterLoop(loop_info, instruction, collect_loop_uses, &use_count) && (use_count == 0 || (!IsEarlyExit(loop_info) && TryReplaceWithLastValue(loop_info, instruction, block))); } void HLoopOptimization::RemoveDeadInstructions(const HInstructionList& list) { for (HBackwardInstructionIterator i(list); !i.Done(); i.Advance()) { HInstruction* instruction = i.Current(); if (instruction->IsDeadAndRemovable()) { simplified_ = true; instruction->GetBlock()->RemoveInstructionOrPhi(instruction); } } } bool HLoopOptimization::CanRemoveCycle() { for (HInstruction* i : *iset_) { // We can never remove instructions that have environment // uses when we compile 'debuggable'. if (i->HasEnvironmentUses() && graph_->IsDebuggable()) { return false; } // A deoptimization should never have an environment input removed. for (const HUseListNode& use : i->GetEnvUses()) { if (use.GetUser()->GetHolder()->IsDeoptimize()) { return false; } } } return true; } } // namespace art