| /* |
| * 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/instruction_set.h" |
| #include "arch/arm/instruction_set_features_arm.h" |
| #include "arch/arm64/instruction_set_features_arm64.h" |
| #include "arch/mips/instruction_set_features_mips.h" |
| #include "arch/mips64/instruction_set_features_mips64.h" |
| #include "arch/x86/instruction_set_features_x86.h" |
| #include "arch/x86_64/instruction_set_features_x86_64.h" |
| #include "driver/compiler_driver.h" |
| #include "linear_order.h" |
| |
| namespace art { |
| |
| // Enables vectorization (SIMDization) in the loop optimizer. |
| static constexpr bool kEnableVectorization = true; |
| |
| // All current SIMD targets want 16-byte alignment. |
| static constexpr size_t kAlignedBase = 16; |
| |
| // 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); |
| } |
| |
| // 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; |
| } |
| |
| // Detect a sign extension from the given type. Returns the promoted operand on success. |
| static bool IsSignExtensionAndGet(HInstruction* instruction, |
| Primitive::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 char normally zero extends does not matter here). |
| int64_t value = 0; |
| if (IsInt64AndGet(instruction, /*out*/ &value)) { |
| switch (type) { |
| case Primitive::kPrimByte: |
| if (std::numeric_limits<int8_t>::min() <= value && |
| std::numeric_limits<int8_t>::max() >= value) { |
| *operand = instruction; |
| return true; |
| } |
| return false; |
| case Primitive::kPrimChar: |
| case Primitive::kPrimShort: |
| if (std::numeric_limits<int16_t>::min() <= value && |
| std::numeric_limits<int16_t>::max() <= value) { |
| *operand = instruction; |
| return true; |
| } |
| return false; |
| default: |
| return false; |
| } |
| } |
| // An implicit widening conversion of a signed integer to an integral type sign-extends |
| // the two's-complement representation of the integer value to fill the wider format. |
| if (instruction->GetType() == type && (instruction->IsArrayGet() || |
| instruction->IsStaticFieldGet() || |
| instruction->IsInstanceFieldGet())) { |
| switch (type) { |
| case Primitive::kPrimByte: |
| case Primitive::kPrimShort: |
| *operand = instruction; |
| return true; |
| default: |
| return false; |
| } |
| } |
| // TODO: perhaps explicit conversions later too? |
| // (this may return something different from instruction) |
| return false; |
| } |
| |
| // Detect a zero extension from the given type. Returns the promoted operand on success. |
| static bool IsZeroExtensionAndGet(HInstruction* instruction, |
| Primitive::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 byte/short normally sign extend does not matter here). |
| int64_t value = 0; |
| if (IsInt64AndGet(instruction, /*out*/ &value)) { |
| switch (type) { |
| case Primitive::kPrimByte: |
| if (std::numeric_limits<uint8_t>::min() <= value && |
| std::numeric_limits<uint8_t>::max() >= value) { |
| *operand = instruction; |
| return true; |
| } |
| return false; |
| case Primitive::kPrimChar: |
| case Primitive::kPrimShort: |
| if (std::numeric_limits<uint16_t>::min() <= value && |
| std::numeric_limits<uint16_t>::max() <= value) { |
| *operand = instruction; |
| return true; |
| } |
| return false; |
| default: |
| return false; |
| } |
| } |
| // An implicit widening conversion of a char to an integral type zero-extends |
| // the representation of the char value to fill the wider format. |
| if (instruction->GetType() == type && (instruction->IsArrayGet() || |
| instruction->IsStaticFieldGet() || |
| instruction->IsInstanceFieldGet())) { |
| if (type == Primitive::kPrimChar) { |
| *operand = instruction; |
| return true; |
| } |
| } |
| // A sign (or zero) extension followed by an explicit removal of just the |
| // higher sign bits is equivalent to a zero extension of the underlying operand. |
| if (instruction->IsAnd()) { |
| int64_t mask = 0; |
| HInstruction* a = instruction->InputAt(0); |
| HInstruction* b = instruction->InputAt(1); |
| // In (a & b) find (mask & b) or (a & mask) with sign or zero extension on the non-mask. |
| if ((IsInt64AndGet(a, /*out*/ &mask) && (IsSignExtensionAndGet(b, type, /*out*/ operand) || |
| IsZeroExtensionAndGet(b, type, /*out*/ operand))) || |
| (IsInt64AndGet(b, /*out*/ &mask) && (IsSignExtensionAndGet(a, type, /*out*/ operand) || |
| IsZeroExtensionAndGet(a, type, /*out*/ operand)))) { |
| switch ((*operand)->GetType()) { |
| case Primitive::kPrimByte: return mask == std::numeric_limits<uint8_t>::max(); |
| case Primitive::kPrimChar: |
| case Primitive::kPrimShort: return mask == std::numeric_limits<uint16_t>::max(); |
| default: return false; |
| } |
| } |
| } |
| // TODO: perhaps explicit conversions later too? |
| 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, |
| Primitive::Type type, |
| /*out*/ HInstruction** r, |
| /*out*/ HInstruction** s, |
| /*out*/ bool* is_unsigned) { |
| if (IsSignExtensionAndGet(a, type, r) && IsSignExtensionAndGet(b, type, s)) { |
| *is_unsigned = false; |
| return true; |
| } else if (IsZeroExtensionAndGet(a, type, r) && IsZeroExtensionAndGet(b, type, s)) { |
| *is_unsigned = true; |
| return true; |
| } |
| return false; |
| } |
| |
| // As above, single operand. |
| static bool IsNarrowerOperand(HInstruction* a, |
| Primitive::Type type, |
| /*out*/ HInstruction** r, |
| /*out*/ bool* is_unsigned) { |
| if (IsSignExtensionAndGet(a, type, r)) { |
| *is_unsigned = false; |
| return true; |
| } else if (IsZeroExtensionAndGet(a, type, r)) { |
| *is_unsigned = true; |
| return true; |
| } |
| return false; |
| } |
| |
| // Detect up to two instructions a and b, and an acccumulated constant c. |
| static bool IsAddConstHelper(HInstruction* instruction, |
| /*out*/ HInstruction** a, |
| /*out*/ HInstruction** b, |
| /*out*/ int64_t* c, |
| int32_t depth) { |
| static constexpr int32_t kMaxDepth = 8; // don't search too deep |
| int64_t value = 0; |
| if (IsInt64AndGet(instruction, &value)) { |
| *c += value; |
| return true; |
| } else if (instruction->IsAdd() && depth <= kMaxDepth) { |
| return IsAddConstHelper(instruction->InputAt(0), a, b, c, depth + 1) && |
| IsAddConstHelper(instruction->InputAt(1), a, b, c, depth + 1); |
| } else if (*a == nullptr) { |
| *a = instruction; |
| return true; |
| } else if (*b == nullptr) { |
| *b = instruction; |
| return true; |
| } |
| return false; // too many non-const operands |
| } |
| |
| // Detect a + b + c for an optional constant c. |
| static bool IsAddConst(HInstruction* instruction, |
| /*out*/ HInstruction** a, |
| /*out*/ HInstruction** b, |
| /*out*/ int64_t* c) { |
| if (instruction->IsAdd()) { |
| // Try to find a + b and accumulated c. |
| if (IsAddConstHelper(instruction->InputAt(0), a, b, c, /*depth*/ 0) && |
| IsAddConstHelper(instruction->InputAt(1), a, b, c, /*depth*/ 0) && |
| *b != nullptr) { |
| return true; |
| } |
| // Found a + b. |
| *a = instruction->InputAt(0); |
| *b = instruction->InputAt(1); |
| *c = 0; |
| return true; |
| } |
| return false; |
| } |
| |
| // 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; |
| } |
| |
| // |
| // Class methods. |
| // |
| |
| HLoopOptimization::HLoopOptimization(HGraph* graph, |
| CompilerDriver* compiler_driver, |
| HInductionVarAnalysis* induction_analysis) |
| : HOptimization(graph, kLoopOptimizationPassName), |
| compiler_driver_(compiler_driver), |
| induction_range_(induction_analysis), |
| loop_allocator_(nullptr), |
| global_allocator_(graph_->GetArena()), |
| top_loop_(nullptr), |
| last_loop_(nullptr), |
| iset_(nullptr), |
| induction_simplication_count_(0), |
| simplified_(false), |
| vector_length_(0), |
| vector_refs_(nullptr), |
| vector_peeling_candidate_(nullptr), |
| vector_runtime_test_a_(nullptr), |
| vector_runtime_test_b_(nullptr), |
| vector_map_(nullptr) { |
| } |
| |
| void 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; |
| } |
| |
| // Phase-local allocator that draws from the global pool. Since the allocator |
| // itself resides on the stack, it is destructed on exiting Run(), which |
| // implies its underlying memory is released immediately. |
| ArenaAllocator allocator(global_allocator_->GetArenaPool()); |
| loop_allocator_ = &allocator; |
| |
| // Perform loop optimizations. |
| LocalRun(); |
| if (top_loop_ == nullptr) { |
| graph_->SetHasLoops(false); // no more loops |
| } |
| |
| // Detach. |
| loop_allocator_ = nullptr; |
| last_loop_ = top_loop_ = nullptr; |
| } |
| |
| void HLoopOptimization::LocalRun() { |
| // 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. |
| ArenaVector<HBasicBlock*> linear_order(loop_allocator_->Adapter(kArenaAllocLinearOrder)); |
| LinearizeGraph(graph_, loop_allocator_, &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) { |
| ArenaSet<HInstruction*> iset(loop_allocator_->Adapter(kArenaAllocLoopOptimization)); |
| ArenaSet<ArrayReference> refs(loop_allocator_->Adapter(kArenaAllocLoopOptimization)); |
| ArenaSafeMap<HInstruction*, HInstruction*> map( |
| std::less<HInstruction*>(), loop_allocator_->Adapter(kArenaAllocLoopOptimization)); |
| // Attach. |
| iset_ = &iset; |
| vector_refs_ = &refs; |
| vector_map_ = ↦ |
| // Traverse. |
| TraverseLoopsInnerToOuter(top_loop_); |
| // Detach. |
| iset_ = nullptr; |
| vector_refs_ = nullptr; |
| vector_map_ = nullptr; |
| } |
| } |
| |
| 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; |
| } |
| } |
| } |
| |
| void HLoopOptimization::TraverseLoopsInnerToOuter(LoopNode* node) { |
| for ( ; node != nullptr; node = node->next) { |
| // Visit inner loops first. |
| uint32_t current_induction_simplification_count = induction_simplication_count_; |
| if (node->inner != nullptr) { |
| TraverseLoopsInnerToOuter(node->inner); |
| } |
| // Recompute induction information of this loop if the induction |
| // of any inner loop has been simplified. |
| if (current_induction_simplification_count != induction_simplication_count_) { |
| induction_range_.ReVisit(node->loop_info); |
| } |
| // 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); |
| } while (simplified_); |
| // Optimize inner loop. |
| if (node->inner == nullptr) { |
| OptimizeInnerLoop(node); |
| } |
| } |
| } |
| |
| // |
| // 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(); |
| iset_->clear(); // prepare phi induction |
| 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. |
| if (CanRemoveCycle()) { |
| for (HInstruction* i : *iset_) { |
| RemoveFromCycle(i); |
| } |
| simplified_ = true; |
| } |
| } |
| } |
| } |
| |
| 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); |
| } |
| } |
| } |
| } |
| } |
| |
| void HLoopOptimization::OptimizeInnerLoop(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; |
| } |
| |
| // 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; |
| } |
| body = it.Current(); |
| } |
| } |
| CHECK(body != nullptr); |
| // Ensure there is only a single exit point. |
| if (header->GetSuccessors().size() != 2) { |
| return; |
| } |
| 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; |
| } |
| // 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. |
| HInstruction* phi = header->GetFirstPhi(); |
| iset_->clear(); // prepare phi induction |
| if (TrySetSimpleLoopHeader(header)) { |
| bool is_empty = IsEmptyBody(body); |
| if ((is_empty || trip_count == 1) && |
| TryAssignLastValue(node->loop_info, phi, preheader, /*collect_loop_uses*/ true)) { |
| if (!is_empty) { |
| // Unroll the loop-body, which sees initial value of the index. |
| phi->ReplaceWith(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; |
| } |
| } |
| |
| // Vectorize loop, if possible and valid. |
| if (kEnableVectorization) { |
| iset_->clear(); // prepare phi induction |
| if (TrySetSimpleLoopHeader(header) && |
| ShouldVectorize(node, body, trip_count) && |
| TryAssignLastValue(node->loop_info, phi, preheader, /*collect_loop_uses*/ true)) { |
| Vectorize(node, body, exit, trip_count); |
| graph_->SetHasSIMD(true); // flag SIMD usage |
| return; |
| } |
| } |
| } |
| |
| // |
| // 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_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 |
| } |
| } |
| |
| // Does vectorization seem profitable? |
| if (!IsVectorizationProfitable(trip_count)) { |
| return false; |
| } |
| |
| // 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. |
| for (auto i = vector_refs_->begin(); i != vector_refs_->end(); ++i) { |
| 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; |
| } |
| } 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 |
| } |
| } |
| } |
| } |
| } |
| } |
| |
| // Consider dynamic loop peeling for alignment. |
| SetPeelingCandidate(trip_count); |
| |
| // Success! |
| return true; |
| } |
| |
| void HLoopOptimization::Vectorize(LoopNode* node, |
| HBasicBlock* block, |
| HBasicBlock* exit, |
| int64_t trip_count) { |
| Primitive::Type induc_type = Primitive::kPrimInt; |
| HBasicBlock* header = node->loop_info->GetHeader(); |
| HBasicBlock* preheader = node->loop_info->GetPreHeader(); |
| |
| // Pick a loop unrolling factor for the vector loop. |
| uint32_t unroll = GetUnrollingFactor(block, trip_count); |
| uint32_t chunk = vector_length_ * unroll; |
| |
| // 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 % chunk) != 0; |
| |
| // Adjust vector bookkeeping. |
| iset_->clear(); // prepare phi induction |
| bool is_simple_loop_header = TrySetSimpleLoopHeader(header); // fills iset_ |
| DCHECK(is_simple_loop_header); |
| vector_header_ = header; |
| vector_body_ = block; |
| |
| // Generate dynamic loop peeling trip count, if needed: |
| // ptc = <peeling-needed-for-candidate> |
| HInstruction* ptc = nullptr; |
| if (vector_peeling_candidate_ != nullptr) { |
| DCHECK_LT(vector_length_, trip_count) << "dynamic peeling currently requires known trip count"; |
| // |
| // TODO: Implement this. Compute address of first access memory location and |
| // compute peeling factor to obtain kAlignedBase alignment. |
| // |
| needs_cleanup = true; |
| } |
| |
| // Generate loop control: |
| // stc = <trip-count>; |
| // 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) { |
| diff = Insert(preheader, new (global_allocator_) HSub(induc_type, stc, ptc)); |
| } |
| HInstruction* rem = Insert( |
| preheader, new (global_allocator_) HAnd(induc_type, |
| diff, |
| graph_->GetIntConstant(chunk - 1))); |
| vtc = Insert(preheader, new (global_allocator_) HSub(induc_type, stc, rem)); |
| } |
| vector_index_ = graph_->GetIntConstant(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_->GetIntConstant(0), kNoDexPc)); |
| needs_cleanup = true; |
| } |
| |
| // Generate dynamic peeling loop for alignment, if needed: |
| // for ( ; i < ptc; i += 1) |
| // <loop-body> |
| if (ptc != nullptr) { |
| vector_mode_ = kSequential; |
| GenerateNewLoop(node, |
| block, |
| graph_->TransformLoopForVectorization(vector_header_, vector_body_, exit), |
| vector_index_, |
| ptc, |
| graph_->GetIntConstant(1), |
| /*unroll*/ 1); |
| } |
| |
| // Generate vector loop, possibly further unrolled: |
| // for ( ; i < vtc; i += chunk) |
| // <vectorized-loop-body> |
| vector_mode_ = kVector; |
| GenerateNewLoop(node, |
| block, |
| graph_->TransformLoopForVectorization(vector_header_, vector_body_, exit), |
| vector_index_, |
| vtc, |
| graph_->GetIntConstant(vector_length_), // increment per unroll |
| unroll); |
| HLoopInformation* vloop = vector_header_->GetLoopInformation(); |
| |
| // Generate cleanup loop, if needed: |
| // for ( ; i < stc; i += 1) |
| // <loop-body> |
| if (needs_cleanup) { |
| vector_mode_ = kSequential; |
| GenerateNewLoop(node, |
| block, |
| graph_->TransformLoopForVectorization(vector_header_, vector_body_, exit), |
| vector_index_, |
| stc, |
| graph_->GetIntConstant(1), |
| /*unroll*/ 1); |
| } |
| |
| // 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); |
| Primitive::Type induc_type = Primitive::kPrimInt; |
| // 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) |
| // <loop-body> |
| 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; |
| for (uint32_t u = 0; u < unroll; u++) { |
| // Clear map, leaving loop invariants setup during unrolling. |
| if (u == 0) { |
| vector_map_->clear(); |
| } else { |
| for (auto i = vector_map_->begin(); i != vector_map_->end(); ) { |
| if (i->second->IsVecReplicateScalar()) { |
| DCHECK(node->loop_info->IsDefinedOutOfTheLoop(i->first)); |
| ++i; |
| } else { |
| i = vector_map_->erase(i); |
| } |
| } |
| } |
| // Generate instruction map. |
| 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_); |
| } |
| } |
| } |
| vector_index_ = new (global_allocator_) HAdd(induc_type, vector_index_, step); |
| Insert(vector_body_, vector_index_); |
| } |
| // Finalize phi for the loop index. |
| phi->AddInput(lo); |
| phi->AddInput(vector_index_); |
| vector_index_ = phi; |
| } |
| |
| // TODO: accept reductions at left-hand-side, mixed-type store idioms, etc. |
| 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; |
| if (instruction->IsArraySet()) { |
| Primitive::Type type = instruction->AsArraySet()->GetComponentType(); |
| HInstruction* base = instruction->InputAt(0); |
| HInstruction* index = instruction->InputAt(1); |
| HInstruction* value = instruction->InputAt(2); |
| HInstruction* offset = nullptr; |
| 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; |
| } |
| // 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(); |
| } |
| |
| // TODO: saturation arithmetic. |
| bool HLoopOptimization::VectorizeUse(LoopNode* node, |
| HInstruction* instruction, |
| bool generate_code, |
| Primitive::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. |
| if (instruction->AsArrayGet()->IsStringCharAt() && |
| HasVectorRestrictions(restrictions, kNoStringCharAt)) { |
| return false; |
| } |
| // Accept a right-hand-side array base[index] for |
| // (1) exact matching vector type, |
| // (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 (type == 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)); |
| } |
| return true; |
| } |
| } else if (instruction->IsTypeConversion()) { |
| // Accept particular type conversions. |
| HTypeConversion* conversion = instruction->AsTypeConversion(); |
| HInstruction* opa = conversion->InputAt(0); |
| Primitive::Type from = conversion->GetInputType(); |
| Primitive::Type to = conversion->GetResultType(); |
| if ((to == Primitive::kPrimByte || |
| to == Primitive::kPrimChar || |
| to == Primitive::kPrimShort) && from == Primitive::kPrimInt) { |
| // Accept a "narrowing" type conversion from a "wider" computation for |
| // (1) conversion into final required type, |
| // (2) vectorizable operand, |
| // (3) "wider" operations cannot bring in higher order bits. |
| if (to == type && VectorizeUse(node, opa, generate_code, type, restrictions | kNoHiBits)) { |
| 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 == Primitive::kPrimFloat && from == Primitive::kPrimInt) { |
| 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 vectorization idioms. |
| 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 = Primitive::ComponentSize(type) * 8; |
| if (0 <= distance && distance < max_distance) { |
| if (generate_code) { |
| GenerateVecOp(instruction, vector_map_->Get(r), opb, type); |
| } |
| return true; |
| } |
| } |
| } else if (instruction->IsInvokeStaticOrDirect()) { |
| // Accept particular intrinsics. |
| HInvokeStaticOrDirect* invoke = instruction->AsInvokeStaticOrDirect(); |
| switch (invoke->GetIntrinsic()) { |
| case Intrinsics::kMathAbsInt: |
| case Intrinsics::kMathAbsLong: |
| case Intrinsics::kMathAbsFloat: |
| case Intrinsics::kMathAbsDouble: { |
| // 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, type); |
| } |
| return true; |
| } |
| return false; |
| } |
| case Intrinsics::kMathMinIntInt: |
| case Intrinsics::kMathMinLongLong: |
| case Intrinsics::kMathMinFloatFloat: |
| case Intrinsics::kMathMinDoubleDouble: |
| case Intrinsics::kMathMaxIntInt: |
| case Intrinsics::kMathMaxLongLong: |
| case Intrinsics::kMathMaxFloatFloat: |
| case Intrinsics::kMathMaxDoubleDouble: { |
| // Deal with vector restrictions. |
| HInstruction* opa = instruction->InputAt(0); |
| HInstruction* opb = instruction->InputAt(1); |
| HInstruction* r = opa; |
| HInstruction* s = opb; |
| bool is_unsigned = false; |
| if (HasVectorRestrictions(restrictions, kNoMinMax)) { |
| return false; |
| } else if (HasVectorRestrictions(restrictions, kNoHiBits) && |
| !IsNarrowerOperands(opa, opb, type, &r, &s, &is_unsigned)) { |
| return false; // reject, unless all operands are same-extension narrower |
| } |
| // Accept MIN/MAX(x, y) for vectorizable operands. |
| DCHECK(r != nullptr && s != nullptr); |
| if (generate_code && vector_mode_ != kVector) { // de-idiom |
| r = opa; |
| s = opb; |
| } |
| if (VectorizeUse(node, r, generate_code, type, restrictions) && |
| VectorizeUse(node, s, generate_code, type, restrictions)) { |
| if (generate_code) { |
| GenerateVecOp( |
| instruction, vector_map_->Get(r), vector_map_->Get(s), type, is_unsigned); |
| } |
| return true; |
| } |
| return false; |
| } |
| default: |
| return false; |
| } // switch |
| } |
| return false; |
| } |
| |
| bool HLoopOptimization::TrySetVectorType(Primitive::Type type, uint64_t* restrictions) { |
| const InstructionSetFeatures* features = compiler_driver_->GetInstructionSetFeatures(); |
| switch (compiler_driver_->GetInstructionSet()) { |
| case kArm: |
| case kThumb2: |
| // Allow vectorization for all ARM devices, because Android assumes that |
| // ARM 32-bit always supports advanced SIMD. |
| switch (type) { |
| case Primitive::kPrimBoolean: |
| case Primitive::kPrimByte: |
| *restrictions |= kNoDiv; |
| return TrySetVectorLength(8); |
| case Primitive::kPrimChar: |
| case Primitive::kPrimShort: |
| *restrictions |= kNoDiv | kNoStringCharAt; |
| return TrySetVectorLength(4); |
| case Primitive::kPrimInt: |
| *restrictions |= kNoDiv; |
| return TrySetVectorLength(2); |
| default: |
| break; |
| } |
| return false; |
| case kArm64: |
| // Allow vectorization for all ARM devices, because Android assumes that |
| // ARMv8 AArch64 always supports advanced SIMD. |
| switch (type) { |
| case Primitive::kPrimBoolean: |
| case Primitive::kPrimByte: |
| *restrictions |= kNoDiv; |
| return TrySetVectorLength(16); |
| case Primitive::kPrimChar: |
| case Primitive::kPrimShort: |
| *restrictions |= kNoDiv; |
| return TrySetVectorLength(8); |
| case Primitive::kPrimInt: |
| *restrictions |= kNoDiv; |
| return TrySetVectorLength(4); |
| case Primitive::kPrimLong: |
| *restrictions |= kNoDiv | kNoMul | kNoMinMax; |
| return TrySetVectorLength(2); |
| case Primitive::kPrimFloat: |
| return TrySetVectorLength(4); |
| case Primitive::kPrimDouble: |
| return TrySetVectorLength(2); |
| default: |
| return false; |
| } |
| case kX86: |
| case kX86_64: |
| // Allow vectorization for SSE4-enabled X86 devices only (128-bit vectors). |
| if (features->AsX86InstructionSetFeatures()->HasSSE4_1()) { |
| switch (type) { |
| case Primitive::kPrimBoolean: |
| case Primitive::kPrimByte: |
| *restrictions |= kNoMul | kNoDiv | kNoShift | kNoAbs | kNoSignedHAdd | kNoUnroundedHAdd; |
| return TrySetVectorLength(16); |
| case Primitive::kPrimChar: |
| case Primitive::kPrimShort: |
| *restrictions |= kNoDiv | kNoAbs | kNoSignedHAdd | kNoUnroundedHAdd; |
| return TrySetVectorLength(8); |
| case Primitive::kPrimInt: |
| *restrictions |= kNoDiv; |
| return TrySetVectorLength(4); |
| case Primitive::kPrimLong: |
| *restrictions |= kNoMul | kNoDiv | kNoShr | kNoAbs | kNoMinMax; |
| return TrySetVectorLength(2); |
| case Primitive::kPrimFloat: |
| *restrictions |= kNoMinMax; // -0.0 vs +0.0 |
| return TrySetVectorLength(4); |
| case Primitive::kPrimDouble: |
| *restrictions |= kNoMinMax; // -0.0 vs +0.0 |
| return TrySetVectorLength(2); |
| default: |
| break; |
| } // switch type |
| } |
| return false; |
| case kMips: |
| if (features->AsMipsInstructionSetFeatures()->HasMsa()) { |
| switch (type) { |
| case Primitive::kPrimBoolean: |
| case Primitive::kPrimByte: |
| *restrictions |= kNoDiv; |
| return TrySetVectorLength(16); |
| case Primitive::kPrimChar: |
| case Primitive::kPrimShort: |
| *restrictions |= kNoDiv | kNoStringCharAt; |
| return TrySetVectorLength(8); |
| case Primitive::kPrimInt: |
| *restrictions |= kNoDiv; |
| return TrySetVectorLength(4); |
| case Primitive::kPrimLong: |
| *restrictions |= kNoDiv; |
| return TrySetVectorLength(2); |
| case Primitive::kPrimFloat: |
| *restrictions |= kNoMinMax; // min/max(x, NaN) |
| return TrySetVectorLength(4); |
| case Primitive::kPrimDouble: |
| *restrictions |= kNoMinMax; // min/max(x, NaN) |
| return TrySetVectorLength(2); |
| default: |
| break; |
| } // switch type |
| } |
| return false; |
| case kMips64: |
| if (features->AsMips64InstructionSetFeatures()->HasMsa()) { |
| switch (type) { |
| case Primitive::kPrimBoolean: |
| case Primitive::kPrimByte: |
| *restrictions |= kNoDiv; |
| return TrySetVectorLength(16); |
| case Primitive::kPrimChar: |
| case Primitive::kPrimShort: |
| *restrictions |= kNoDiv | kNoStringCharAt; |
| return TrySetVectorLength(8); |
| case Primitive::kPrimInt: |
| *restrictions |= kNoDiv; |
| return TrySetVectorLength(4); |
| case Primitive::kPrimLong: |
| *restrictions |= kNoDiv; |
| return TrySetVectorLength(2); |
| case Primitive::kPrimFloat: |
| *restrictions |= kNoMinMax; // min/max(x, NaN) |
| return TrySetVectorLength(4); |
| case Primitive::kPrimDouble: |
| *restrictions |= kNoMinMax; // min/max(x, NaN) |
| return TrySetVectorLength(2); |
| default: |
| break; |
| } // switch type |
| } |
| return false; |
| default: |
| return false; |
| } // switch instruction set |
| } |
| |
| bool HLoopOptimization::TrySetVectorLength(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, Primitive::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 = new (global_allocator_) HVecReplicateScalar( |
| global_allocator_, org, type, vector_length_); |
| vector_map_->Put(org, Insert(vector_preheader_, 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(Primitive::kPrimInt, 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, |
| Primitive::Type type) { |
| HInstruction* vector = nullptr; |
| if (vector_mode_ == kVector) { |
| // Vector store or load. |
| HInstruction* base = org->InputAt(0); |
| if (opb != nullptr) { |
| vector = new (global_allocator_) HVecStore( |
| global_allocator_, base, opa, opb, type, vector_length_); |
| } else { |
| bool is_string_char_at = org->AsArrayGet()->IsStringCharAt(); |
| vector = new (global_allocator_) HVecLoad( |
| global_allocator_, base, opa, type, vector_length_, is_string_char_at); |
| } |
| // Known dynamically enforced alignment? |
| // TODO: detect offset + constant differences. |
| // TODO: long run, static alignment analysis? |
| if (vector_peeling_candidate_ != nullptr && |
| vector_peeling_candidate_->base == base && |
| vector_peeling_candidate_->offset == offset) { |
| vector->AsVecMemoryOperation()->SetAlignment(Alignment(kAlignedBase, 0)); |
| } |
| } else { |
| // Scalar store or load. |
| DCHECK(vector_mode_ == kSequential); |
| if (opb != nullptr) { |
| vector = new (global_allocator_) HArraySet(org->InputAt(0), opa, opb, type, kNoDexPc); |
| } else { |
| bool is_string_char_at = org->AsArrayGet()->IsStringCharAt(); |
| vector = new (global_allocator_) HArrayGet( |
| org->InputAt(0), opa, type, kNoDexPc, is_string_char_at); |
| } |
| } |
| vector_map_->Put(org, vector); |
| } |
| |
| #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, |
| Primitive::Type type, |
| bool is_unsigned) { |
| if (vector_mode_ == kSequential) { |
| // Non-converting scalar code follows implicit integral promotion. |
| if (!org->IsTypeConversion() && (type == Primitive::kPrimBoolean || |
| type == Primitive::kPrimByte || |
| type == Primitive::kPrimChar || |
| type == Primitive::kPrimShort)) { |
| type = Primitive::kPrimInt; |
| } |
| } |
| HInstruction* vector = nullptr; |
| switch (org->GetKind()) { |
| case HInstruction::kNeg: |
| DCHECK(opb == nullptr); |
| GENERATE_VEC( |
| new (global_allocator_) HVecNeg(global_allocator_, opa, type, vector_length_), |
| new (global_allocator_) HNeg(type, opa)); |
| case HInstruction::kNot: |
| DCHECK(opb == nullptr); |
| GENERATE_VEC( |
| new (global_allocator_) HVecNot(global_allocator_, opa, type, vector_length_), |
| new (global_allocator_) HNot(type, opa)); |
| case HInstruction::kBooleanNot: |
| DCHECK(opb == nullptr); |
| GENERATE_VEC( |
| new (global_allocator_) HVecNot(global_allocator_, opa, type, vector_length_), |
| new (global_allocator_) HBooleanNot(opa)); |
| case HInstruction::kTypeConversion: |
| DCHECK(opb == nullptr); |
| GENERATE_VEC( |
| new (global_allocator_) HVecCnv(global_allocator_, opa, type, vector_length_), |
| new (global_allocator_) HTypeConversion(type, opa, kNoDexPc)); |
| case HInstruction::kAdd: |
| GENERATE_VEC( |
| new (global_allocator_) HVecAdd(global_allocator_, opa, opb, type, vector_length_), |
| new (global_allocator_) HAdd(type, opa, opb)); |
| case HInstruction::kSub: |
| GENERATE_VEC( |
| new (global_allocator_) HVecSub(global_allocator_, opa, opb, type, vector_length_), |
| new (global_allocator_) HSub(type, opa, opb)); |
| case HInstruction::kMul: |
| GENERATE_VEC( |
| new (global_allocator_) HVecMul(global_allocator_, opa, opb, type, vector_length_), |
| new (global_allocator_) HMul(type, opa, opb)); |
| case HInstruction::kDiv: |
| GENERATE_VEC( |
| new (global_allocator_) HVecDiv(global_allocator_, opa, opb, type, vector_length_), |
| new (global_allocator_) HDiv(type, opa, opb, kNoDexPc)); |
| case HInstruction::kAnd: |
| GENERATE_VEC( |
| new (global_allocator_) HVecAnd(global_allocator_, opa, opb, type, vector_length_), |
| new (global_allocator_) HAnd(type, opa, opb)); |
| case HInstruction::kOr: |
| GENERATE_VEC( |
| new (global_allocator_) HVecOr(global_allocator_, opa, opb, type, vector_length_), |
| new (global_allocator_) HOr(type, opa, opb)); |
| case HInstruction::kXor: |
| GENERATE_VEC( |
| new (global_allocator_) HVecXor(global_allocator_, opa, opb, type, vector_length_), |
| new (global_allocator_) HXor(type, opa, opb)); |
| case HInstruction::kShl: |
| GENERATE_VEC( |
| new (global_allocator_) HVecShl(global_allocator_, opa, opb, type, vector_length_), |
| new (global_allocator_) HShl(type, opa, opb)); |
| case HInstruction::kShr: |
| GENERATE_VEC( |
| new (global_allocator_) HVecShr(global_allocator_, opa, opb, type, vector_length_), |
| new (global_allocator_) HShr(type, opa, opb)); |
| case HInstruction::kUShr: |
| GENERATE_VEC( |
| new (global_allocator_) HVecUShr(global_allocator_, opa, opb, type, vector_length_), |
| new (global_allocator_) HUShr(type, opa, opb)); |
| case HInstruction::kInvokeStaticOrDirect: { |
| HInvokeStaticOrDirect* invoke = org->AsInvokeStaticOrDirect(); |
| if (vector_mode_ == kVector) { |
| switch (invoke->GetIntrinsic()) { |
| case Intrinsics::kMathAbsInt: |
| case Intrinsics::kMathAbsLong: |
| case Intrinsics::kMathAbsFloat: |
| case Intrinsics::kMathAbsDouble: |
| DCHECK(opb == nullptr); |
| vector = new (global_allocator_) HVecAbs(global_allocator_, opa, type, vector_length_); |
| break; |
| case Intrinsics::kMathMinIntInt: |
| case Intrinsics::kMathMinLongLong: |
| case Intrinsics::kMathMinFloatFloat: |
| case Intrinsics::kMathMinDoubleDouble: { |
| vector = new (global_allocator_) |
| HVecMin(global_allocator_, opa, opb, type, vector_length_, is_unsigned); |
| break; |
| } |
| case Intrinsics::kMathMaxIntInt: |
| case Intrinsics::kMathMaxLongLong: |
| case Intrinsics::kMathMaxFloatFloat: |
| case Intrinsics::kMathMaxDoubleDouble: { |
| vector = new (global_allocator_) |
| HVecMax(global_allocator_, opa, opb, type, vector_length_, is_unsigned); |
| break; |
| } |
| default: |
| LOG(FATAL) << "Unsupported SIMD intrinsic"; |
| UNREACHABLE(); |
| } // switch invoke |
| } else { |
| // In scalar code, simply clone the method invoke, and replace its operands with the |
| // corresponding new scalar instructions in the loop. The instruction will get an |
| // environment while being inserted from the instruction map in original program order. |
| DCHECK(vector_mode_ == kSequential); |
| size_t num_args = invoke->GetNumberOfArguments(); |
| HInvokeStaticOrDirect* new_invoke = new (global_allocator_) HInvokeStaticOrDirect( |
| global_allocator_, |
| num_args, |
| invoke->GetType(), |
| invoke->GetDexPc(), |
| invoke->GetDexMethodIndex(), |
| invoke->GetResolvedMethod(), |
| invoke->GetDispatchInfo(), |
| invoke->GetInvokeType(), |
| invoke->GetTargetMethod(), |
| invoke->GetClinitCheckRequirement()); |
| HInputsRef inputs = invoke->GetInputs(); |
| size_t num_inputs = inputs.size(); |
| DCHECK_LE(num_args, num_inputs); |
| DCHECK_EQ(num_inputs, new_invoke->GetInputs().size()); // both invokes agree |
| for (size_t index = 0; index < num_inputs; ++index) { |
| HInstruction* new_input = index < num_args |
| ? vector_map_->Get(inputs[index]) |
| : inputs[index]; // beyond arguments: just pass through |
| new_invoke->SetArgumentAt(index, new_input); |
| } |
| new_invoke->SetIntrinsic(invoke->GetIntrinsic(), |
| kNeedsEnvironmentOrCache, |
| kNoSideEffects, |
| kNoThrow); |
| vector = new_invoke; |
| } |
| break; |
| } |
| 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 |
| // regular 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, |
| Primitive::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). |
| int64_t distance = 0; |
| if ((instruction->IsShr() || |
| instruction->IsUShr()) && |
| IsInt64AndGet(instruction->InputAt(1), /*out*/ &distance) && distance == 1) { |
| // Test for (a + b + c) >> 1 for optional constant c. |
| HInstruction* a = nullptr; |
| HInstruction* b = nullptr; |
| int64_t c = 0; |
| if (IsAddConst(instruction->InputAt(0), /*out*/ &a, /*out*/ &b, /*out*/ &c)) { |
| DCHECK(a != nullptr && b != nullptr); |
| // 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), |
| type, |
| vector_length_, |
| is_unsigned, |
| is_rounded)); |
| } else { |
| GenerateVecOp(instruction, vector_map_->Get(r), vector_map_->Get(s), type); |
| } |
| } |
| return true; |
| } |
| } |
| } |
| return false; |
| } |
| |
| // |
| // Vectorization heuristics. |
| // |
| |
| 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. |
| if (vector_length_ == 0) { |
| return false; // nothing found |
| } else if (0 < trip_count && trip_count < vector_length_) { |
| return false; // insufficient iterations |
| } |
| return true; |
| } |
| |
| void HLoopOptimization::SetPeelingCandidate(int64_t trip_count ATTRIBUTE_UNUSED) { |
| // Current heuristic: none. |
| // TODO: implement |
| } |
| |
| uint32_t HLoopOptimization::GetUnrollingFactor(HBasicBlock* block, int64_t trip_count) { |
| // Current heuristic: unroll by 2 on ARM64/X86 for large known trip |
| // counts and small loop bodies. |
| // TODO: refine with operation count, remaining iterations, etc. |
| // Artem had some really cool ideas for this already. |
| switch (compiler_driver_->GetInstructionSet()) { |
| case kArm64: |
| case kX86: |
| case kX86_64: { |
| size_t num_instructions = block->GetInstructions().CountSize(); |
| if (num_instructions <= 10 && trip_count >= 4 * vector_length_) { |
| return 2; |
| } |
| return 1; |
| } |
| default: |
| return 1; |
| } |
| } |
| |
| // |
| // Helpers. |
| // |
| |
| bool HLoopOptimization::TrySetPhiInduction(HPhi* phi, bool restrict_uses) { |
| // 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; |
| } |
| DCHECK(iset_->empty()); |
| ArenaSet<HInstruction*>* 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) { |
| for (const HUseListNode<HInstruction*>& use : i->GetUses()) { |
| if (set->find(use.GetUser()) == set->end()) { |
| return false; |
| } |
| } |
| } |
| iset_->insert(i); // copy |
| } |
| return true; |
| } |
| return false; |
| } |
| |
| // Find: phi: Phi(init, addsub) |
| // s: SuspendCheck |
| // c: Condition(phi, bound) |
| // i: If(c) |
| // TODO: Find a less pattern matching approach? |
| bool HLoopOptimization::TrySetSimpleLoopHeader(HBasicBlock* block) { |
| DCHECK(iset_->empty()); |
| HInstruction* phi = block->GetFirstPhi(); |
| if (phi != nullptr && |
| phi->GetNext() == nullptr && |
| TrySetPhiInduction(phi->AsPhi(), /*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); |
| 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) { |
| for (const HUseListNode<HInstruction*>& 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*/ int32_t* use_count) { |
| for (const HUseListNode<HInstruction*>& 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); |
| const HUseList<HInstruction*>& 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 |
| } |
| } |
| const HUseList<HEnvironment*>& 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); |
| } |
| } |
| } |
| induction_simplication_count_++; |
| 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. |
| int32_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<HEnvironment*>& use : i->GetEnvUses()) { |
| if (use.GetUser()->GetHolder()->IsDeoptimize()) { |
| return false; |
| } |
| } |
| } |
| return true; |
| } |
| |
| } // namespace art |