/* * Copyright (c) 2018, Oracle and/or its affiliates. All rights reserved. * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. * * This code is free software; you can redistribute it and/or modify it * under the terms of the GNU General Public License version 2 only, as * published by the Free Software Foundation. * * This code is distributed in the hope that it will be useful, but WITHOUT * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License * version 2 for more details (a copy is included in the LICENSE file that * accompanied this code). * * You should have received a copy of the GNU General Public License version * 2 along with this work; if not, write to the Free Software Foundation, * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. * * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA * or visit www.oracle.com if you need additional information or have any * questions. * */ #include "precompiled.hpp" #include "gc/g1/c2/g1BarrierSetC2.hpp" #include "gc/g1/g1BarrierSet.hpp" #include "gc/g1/g1CardTable.hpp" #include "gc/g1/g1ThreadLocalData.hpp" #include "gc/g1/heapRegion.hpp" #include "opto/arraycopynode.hpp" #include "opto/graphKit.hpp" #include "opto/idealKit.hpp" #include "opto/macro.hpp" #include "opto/type.hpp" #include "runtime/sharedRuntime.hpp" #include "utilities/macros.hpp" const TypeFunc *G1BarrierSetC2::g1_wb_pre_Type() { const Type **fields = TypeTuple::fields(2); fields[TypeFunc::Parms+0] = TypeInstPtr::NOTNULL; // original field value fields[TypeFunc::Parms+1] = TypeRawPtr::NOTNULL; // thread const TypeTuple *domain = TypeTuple::make(TypeFunc::Parms+2, fields); // create result type (range) fields = TypeTuple::fields(0); const TypeTuple *range = TypeTuple::make(TypeFunc::Parms+0, fields); return TypeFunc::make(domain, range); } const TypeFunc *G1BarrierSetC2::g1_wb_post_Type() { const Type **fields = TypeTuple::fields(2); fields[TypeFunc::Parms+0] = TypeRawPtr::NOTNULL; // Card addr fields[TypeFunc::Parms+1] = TypeRawPtr::NOTNULL; // thread const TypeTuple *domain = TypeTuple::make(TypeFunc::Parms+2, fields); // create result type (range) fields = TypeTuple::fields(0); const TypeTuple *range = TypeTuple::make(TypeFunc::Parms, fields); return TypeFunc::make(domain, range); } #define __ ideal. /* * Determine if the G1 pre-barrier can be removed. The pre-barrier is * required by SATB to make sure all objects live at the start of the * marking are kept alive, all reference updates need to any previous * reference stored before writing. * * If the previous value is NULL there is no need to save the old value. * References that are NULL are filtered during runtime by the barrier * code to avoid unnecessary queuing. * * However in the case of newly allocated objects it might be possible to * prove that the reference about to be overwritten is NULL during compile * time and avoid adding the barrier code completely. * * The compiler needs to determine that the object in which a field is about * to be written is newly allocated, and that no prior store to the same field * has happened since the allocation. * * Returns true if the pre-barrier can be removed */ bool G1BarrierSetC2::g1_can_remove_pre_barrier(GraphKit* kit, PhaseTransform* phase, Node* adr, BasicType bt, uint adr_idx) const { intptr_t offset = 0; Node* base = AddPNode::Ideal_base_and_offset(adr, phase, offset); AllocateNode* alloc = AllocateNode::Ideal_allocation(base, phase); if (offset == Type::OffsetBot) { return false; // cannot unalias unless there are precise offsets } if (alloc == NULL) { return false; // No allocation found } intptr_t size_in_bytes = type2aelembytes(bt); Node* mem = kit->memory(adr_idx); // start searching here... for (int cnt = 0; cnt < 50; cnt++) { if (mem->is_Store()) { Node* st_adr = mem->in(MemNode::Address); intptr_t st_offset = 0; Node* st_base = AddPNode::Ideal_base_and_offset(st_adr, phase, st_offset); if (st_base == NULL) { break; // inscrutable pointer } // Break we have found a store with same base and offset as ours so break if (st_base == base && st_offset == offset) { break; } if (st_offset != offset && st_offset != Type::OffsetBot) { const int MAX_STORE = BytesPerLong; if (st_offset >= offset + size_in_bytes || st_offset <= offset - MAX_STORE || st_offset <= offset - mem->as_Store()->memory_size()) { // Success: The offsets are provably independent. // (You may ask, why not just test st_offset != offset and be done? // The answer is that stores of different sizes can co-exist // in the same sequence of RawMem effects. We sometimes initialize // a whole 'tile' of array elements with a single jint or jlong.) mem = mem->in(MemNode::Memory); continue; // advance through independent store memory } } if (st_base != base && MemNode::detect_ptr_independence(base, alloc, st_base, AllocateNode::Ideal_allocation(st_base, phase), phase)) { // Success: The bases are provably independent. mem = mem->in(MemNode::Memory); continue; // advance through independent store memory } } else if (mem->is_Proj() && mem->in(0)->is_Initialize()) { InitializeNode* st_init = mem->in(0)->as_Initialize(); AllocateNode* st_alloc = st_init->allocation(); // Make sure that we are looking at the same allocation site. // The alloc variable is guaranteed to not be null here from earlier check. if (alloc == st_alloc) { // Check that the initialization is storing NULL so that no previous store // has been moved up and directly write a reference Node* captured_store = st_init->find_captured_store(offset, type2aelembytes(T_OBJECT), phase); if (captured_store == NULL || captured_store == st_init->zero_memory()) { return true; } } } // Unless there is an explicit 'continue', we must bail out here, // because 'mem' is an inscrutable memory state (e.g., a call). break; } return false; } // G1 pre/post barriers void G1BarrierSetC2::pre_barrier(GraphKit* kit, bool do_load, Node* ctl, Node* obj, Node* adr, uint alias_idx, Node* val, const TypeOopPtr* val_type, Node* pre_val, BasicType bt) const { // Some sanity checks // Note: val is unused in this routine. if (do_load) { // We need to generate the load of the previous value assert(obj != NULL, "must have a base"); assert(adr != NULL, "where are loading from?"); assert(pre_val == NULL, "loaded already?"); assert(val_type != NULL, "need a type"); if (use_ReduceInitialCardMarks() && g1_can_remove_pre_barrier(kit, &kit->gvn(), adr, bt, alias_idx)) { return; } } else { // In this case both val_type and alias_idx are unused. assert(pre_val != NULL, "must be loaded already"); // Nothing to be done if pre_val is null. if (pre_val->bottom_type() == TypePtr::NULL_PTR) return; assert(pre_val->bottom_type()->basic_type() == T_OBJECT, "or we shouldn't be here"); } assert(bt == T_OBJECT, "or we shouldn't be here"); IdealKit ideal(kit, true); Node* tls = __ thread(); // ThreadLocalStorage Node* no_base = __ top(); Node* zero = __ ConI(0); Node* zeroX = __ ConX(0); float likely = PROB_LIKELY(0.999); float unlikely = PROB_UNLIKELY(0.999); BasicType active_type = in_bytes(SATBMarkQueue::byte_width_of_active()) == 4 ? T_INT : T_BYTE; assert(in_bytes(SATBMarkQueue::byte_width_of_active()) == 4 || in_bytes(SATBMarkQueue::byte_width_of_active()) == 1, "flag width"); // Offsets into the thread const int marking_offset = in_bytes(G1ThreadLocalData::satb_mark_queue_active_offset()); const int index_offset = in_bytes(G1ThreadLocalData::satb_mark_queue_index_offset()); const int buffer_offset = in_bytes(G1ThreadLocalData::satb_mark_queue_buffer_offset()); // Now the actual pointers into the thread Node* marking_adr = __ AddP(no_base, tls, __ ConX(marking_offset)); Node* buffer_adr = __ AddP(no_base, tls, __ ConX(buffer_offset)); Node* index_adr = __ AddP(no_base, tls, __ ConX(index_offset)); // Now some of the values Node* marking = __ load(__ ctrl(), marking_adr, TypeInt::INT, active_type, Compile::AliasIdxRaw); // if (!marking) __ if_then(marking, BoolTest::ne, zero, unlikely); { BasicType index_bt = TypeX_X->basic_type(); assert(sizeof(size_t) == type2aelembytes(index_bt), "Loading G1 SATBMarkQueue::_index with wrong size."); Node* index = __ load(__ ctrl(), index_adr, TypeX_X, index_bt, Compile::AliasIdxRaw); if (do_load) { // load original value // alias_idx correct?? pre_val = __ load(__ ctrl(), adr, val_type, bt, alias_idx); } // if (pre_val != NULL) __ if_then(pre_val, BoolTest::ne, kit->null()); { Node* buffer = __ load(__ ctrl(), buffer_adr, TypeRawPtr::NOTNULL, T_ADDRESS, Compile::AliasIdxRaw); // is the queue for this thread full? __ if_then(index, BoolTest::ne, zeroX, likely); { // decrement the index Node* next_index = kit->gvn().transform(new SubXNode(index, __ ConX(sizeof(intptr_t)))); // Now get the buffer location we will log the previous value into and store it Node *log_addr = __ AddP(no_base, buffer, next_index); __ store(__ ctrl(), log_addr, pre_val, T_OBJECT, Compile::AliasIdxRaw, MemNode::unordered); // update the index __ store(__ ctrl(), index_adr, next_index, index_bt, Compile::AliasIdxRaw, MemNode::unordered); } __ else_(); { // logging buffer is full, call the runtime const TypeFunc *tf = g1_wb_pre_Type(); __ make_leaf_call(tf, CAST_FROM_FN_PTR(address, SharedRuntime::g1_wb_pre), "g1_wb_pre", pre_val, tls); } __ end_if(); // (!index) } __ end_if(); // (pre_val != NULL) } __ end_if(); // (!marking) // Final sync IdealKit and GraphKit. kit->final_sync(ideal); } /* * G1 similar to any GC with a Young Generation requires a way to keep track of * references from Old Generation to Young Generation to make sure all live * objects are found. G1 also requires to keep track of object references * between different regions to enable evacuation of old regions, which is done * as part of mixed collections. References are tracked in remembered sets and * is continuously updated as reference are written to with the help of the * post-barrier. * * To reduce the number of updates to the remembered set the post-barrier * filters updates to fields in objects located in the Young Generation, * the same region as the reference, when the NULL is being written or * if the card is already marked as dirty by an earlier write. * * Under certain circumstances it is possible to avoid generating the * post-barrier completely if it is possible during compile time to prove * the object is newly allocated and that no safepoint exists between the * allocation and the store. * * In the case of slow allocation the allocation code must handle the barrier * as part of the allocation in the case the allocated object is not located * in the nursery, this would happen for humongous objects. This is similar to * how CMS is required to handle this case, see the comments for the method * CollectedHeap::new_deferred_store_barrier and OptoRuntime::new_deferred_store_barrier. * A deferred card mark is required for these objects and handled in the above * mentioned methods. * * Returns true if the post barrier can be removed */ bool G1BarrierSetC2::g1_can_remove_post_barrier(GraphKit* kit, PhaseTransform* phase, Node* store, Node* adr) const { intptr_t offset = 0; Node* base = AddPNode::Ideal_base_and_offset(adr, phase, offset); AllocateNode* alloc = AllocateNode::Ideal_allocation(base, phase); if (offset == Type::OffsetBot) { return false; // cannot unalias unless there are precise offsets } if (alloc == NULL) { return false; // No allocation found } // Start search from Store node Node* mem = store->in(MemNode::Control); if (mem->is_Proj() && mem->in(0)->is_Initialize()) { InitializeNode* st_init = mem->in(0)->as_Initialize(); AllocateNode* st_alloc = st_init->allocation(); // Make sure we are looking at the same allocation if (alloc == st_alloc) { return true; } } return false; } // // Update the card table and add card address to the queue // void G1BarrierSetC2::g1_mark_card(GraphKit* kit, IdealKit& ideal, Node* card_adr, Node* oop_store, uint oop_alias_idx, Node* index, Node* index_adr, Node* buffer, const TypeFunc* tf) const { Node* zero = __ ConI(0); Node* zeroX = __ ConX(0); Node* no_base = __ top(); BasicType card_bt = T_BYTE; // Smash zero into card. MUST BE ORDERED WRT TO STORE __ storeCM(__ ctrl(), card_adr, zero, oop_store, oop_alias_idx, card_bt, Compile::AliasIdxRaw); // Now do the queue work __ if_then(index, BoolTest::ne, zeroX); { Node* next_index = kit->gvn().transform(new SubXNode(index, __ ConX(sizeof(intptr_t)))); Node* log_addr = __ AddP(no_base, buffer, next_index); // Order, see storeCM. __ store(__ ctrl(), log_addr, card_adr, T_ADDRESS, Compile::AliasIdxRaw, MemNode::unordered); __ store(__ ctrl(), index_adr, next_index, TypeX_X->basic_type(), Compile::AliasIdxRaw, MemNode::unordered); } __ else_(); { __ make_leaf_call(tf, CAST_FROM_FN_PTR(address, SharedRuntime::g1_wb_post), "g1_wb_post", card_adr, __ thread()); } __ end_if(); } void G1BarrierSetC2::post_barrier(GraphKit* kit, Node* ctl, Node* oop_store, Node* obj, Node* adr, uint alias_idx, Node* val, BasicType bt, bool use_precise) const { // If we are writing a NULL then we need no post barrier if (val != NULL && val->is_Con() && val->bottom_type() == TypePtr::NULL_PTR) { // Must be NULL const Type* t = val->bottom_type(); assert(t == Type::TOP || t == TypePtr::NULL_PTR, "must be NULL"); // No post barrier if writing NULLx return; } if (use_ReduceInitialCardMarks() && obj == kit->just_allocated_object(kit->control())) { // We can skip marks on a freshly-allocated object in Eden. // Keep this code in sync with new_deferred_store_barrier() in runtime.cpp. // That routine informs GC to take appropriate compensating steps, // upon a slow-path allocation, so as to make this card-mark // elision safe. return; } if (use_ReduceInitialCardMarks() && g1_can_remove_post_barrier(kit, &kit->gvn(), oop_store, adr)) { return; } if (!use_precise) { // All card marks for a (non-array) instance are in one place: adr = obj; } // (Else it's an array (or unknown), and we want more precise card marks.) assert(adr != NULL, ""); IdealKit ideal(kit, true); Node* tls = __ thread(); // ThreadLocalStorage Node* no_base = __ top(); float unlikely = PROB_UNLIKELY(0.999); Node* young_card = __ ConI((jint)G1CardTable::g1_young_card_val()); Node* dirty_card = __ ConI((jint)G1CardTable::dirty_card_val()); Node* zeroX = __ ConX(0); const TypeFunc *tf = g1_wb_post_Type(); // Offsets into the thread const int index_offset = in_bytes(G1ThreadLocalData::dirty_card_queue_index_offset()); const int buffer_offset = in_bytes(G1ThreadLocalData::dirty_card_queue_buffer_offset()); // Pointers into the thread Node* buffer_adr = __ AddP(no_base, tls, __ ConX(buffer_offset)); Node* index_adr = __ AddP(no_base, tls, __ ConX(index_offset)); // Now some values // Use ctrl to avoid hoisting these values past a safepoint, which could // potentially reset these fields in the JavaThread. Node* index = __ load(__ ctrl(), index_adr, TypeX_X, TypeX_X->basic_type(), Compile::AliasIdxRaw); Node* buffer = __ load(__ ctrl(), buffer_adr, TypeRawPtr::NOTNULL, T_ADDRESS, Compile::AliasIdxRaw); // Convert the store obj pointer to an int prior to doing math on it // Must use ctrl to prevent "integerized oop" existing across safepoint Node* cast = __ CastPX(__ ctrl(), adr); // Divide pointer by card size Node* card_offset = __ URShiftX( cast, __ ConI(CardTable::card_shift) ); // Combine card table base and card offset Node* card_adr = __ AddP(no_base, byte_map_base_node(kit), card_offset ); // If we know the value being stored does it cross regions? if (val != NULL) { // Does the store cause us to cross regions? // Should be able to do an unsigned compare of region_size instead of // and extra shift. Do we have an unsigned compare?? // Node* region_size = __ ConI(1 << HeapRegion::LogOfHRGrainBytes); Node* xor_res = __ URShiftX ( __ XorX( cast, __ CastPX(__ ctrl(), val)), __ ConI(HeapRegion::LogOfHRGrainBytes)); // if (xor_res == 0) same region so skip __ if_then(xor_res, BoolTest::ne, zeroX); { // No barrier if we are storing a NULL __ if_then(val, BoolTest::ne, kit->null(), unlikely); { // Ok must mark the card if not already dirty // load the original value of the card Node* card_val = __ load(__ ctrl(), card_adr, TypeInt::INT, T_BYTE, Compile::AliasIdxRaw); __ if_then(card_val, BoolTest::ne, young_card); { kit->sync_kit(ideal); kit->insert_mem_bar(Op_MemBarVolatile, oop_store); __ sync_kit(kit); Node* card_val_reload = __ load(__ ctrl(), card_adr, TypeInt::INT, T_BYTE, Compile::AliasIdxRaw); __ if_then(card_val_reload, BoolTest::ne, dirty_card); { g1_mark_card(kit, ideal, card_adr, oop_store, alias_idx, index, index_adr, buffer, tf); } __ end_if(); } __ end_if(); } __ end_if(); } __ end_if(); } else { // The Object.clone() intrinsic uses this path if !ReduceInitialCardMarks. // We don't need a barrier here if the destination is a newly allocated object // in Eden. Otherwise, GC verification breaks because we assume that cards in Eden // are set to 'g1_young_gen' (see G1CardTable::verify_g1_young_region()). assert(!use_ReduceInitialCardMarks(), "can only happen with card marking"); Node* card_val = __ load(__ ctrl(), card_adr, TypeInt::INT, T_BYTE, Compile::AliasIdxRaw); __ if_then(card_val, BoolTest::ne, young_card); { g1_mark_card(kit, ideal, card_adr, oop_store, alias_idx, index, index_adr, buffer, tf); } __ end_if(); } // Final sync IdealKit and GraphKit. kit->final_sync(ideal); } // Helper that guards and inserts a pre-barrier. void G1BarrierSetC2::insert_pre_barrier(GraphKit* kit, Node* base_oop, Node* offset, Node* pre_val, bool need_mem_bar) const { // We could be accessing the referent field of a reference object. If so, when G1 // is enabled, we need to log the value in the referent field in an SATB buffer. // This routine performs some compile time filters and generates suitable // runtime filters that guard the pre-barrier code. // Also add memory barrier for non volatile load from the referent field // to prevent commoning of loads across safepoint. // Some compile time checks. // If offset is a constant, is it java_lang_ref_Reference::_reference_offset? const TypeX* otype = offset->find_intptr_t_type(); if (otype != NULL && otype->is_con() && otype->get_con() != java_lang_ref_Reference::referent_offset) { // Constant offset but not the reference_offset so just return return; } // We only need to generate the runtime guards for instances. const TypeOopPtr* btype = base_oop->bottom_type()->isa_oopptr(); if (btype != NULL) { if (btype->isa_aryptr()) { // Array type so nothing to do return; } const TypeInstPtr* itype = btype->isa_instptr(); if (itype != NULL) { // Can the klass of base_oop be statically determined to be // _not_ a sub-class of Reference and _not_ Object? ciKlass* klass = itype->klass(); if ( klass->is_loaded() && !klass->is_subtype_of(kit->env()->Reference_klass()) && !kit->env()->Object_klass()->is_subtype_of(klass)) { return; } } } // The compile time filters did not reject base_oop/offset so // we need to generate the following runtime filters // // if (offset == java_lang_ref_Reference::_reference_offset) { // if (instance_of(base, java.lang.ref.Reference)) { // pre_barrier(_, pre_val, ...); // } // } float likely = PROB_LIKELY( 0.999); float unlikely = PROB_UNLIKELY(0.999); IdealKit ideal(kit); Node* referent_off = __ ConX(java_lang_ref_Reference::referent_offset); __ if_then(offset, BoolTest::eq, referent_off, unlikely); { // Update graphKit memory and control from IdealKit. kit->sync_kit(ideal); Node* ref_klass_con = kit->makecon(TypeKlassPtr::make(kit->env()->Reference_klass())); Node* is_instof = kit->gen_instanceof(base_oop, ref_klass_con); // Update IdealKit memory and control from graphKit. __ sync_kit(kit); Node* one = __ ConI(1); // is_instof == 0 if base_oop == NULL __ if_then(is_instof, BoolTest::eq, one, unlikely); { // Update graphKit from IdeakKit. kit->sync_kit(ideal); // Use the pre-barrier to record the value in the referent field pre_barrier(kit, false /* do_load */, __ ctrl(), NULL /* obj */, NULL /* adr */, max_juint /* alias_idx */, NULL /* val */, NULL /* val_type */, pre_val /* pre_val */, T_OBJECT); if (need_mem_bar) { // Add memory barrier to prevent commoning reads from this field // across safepoint since GC can change its value. kit->insert_mem_bar(Op_MemBarCPUOrder); } // Update IdealKit from graphKit. __ sync_kit(kit); } __ end_if(); // _ref_type != ref_none } __ end_if(); // offset == referent_offset // Final sync IdealKit and GraphKit. kit->final_sync(ideal); } #undef __ Node* G1BarrierSetC2::load_at_resolved(C2Access& access, const Type* val_type) const { DecoratorSet decorators = access.decorators(); GraphKit* kit = access.kit(); Node* adr = access.addr().node(); Node* obj = access.base(); bool mismatched = (decorators & C2_MISMATCHED) != 0; bool unknown = (decorators & ON_UNKNOWN_OOP_REF) != 0; bool on_heap = (decorators & IN_HEAP) != 0; bool on_weak = (decorators & ON_WEAK_OOP_REF) != 0; bool is_unordered = (decorators & MO_UNORDERED) != 0; bool need_cpu_mem_bar = !is_unordered || mismatched || !on_heap; Node* offset = adr->is_AddP() ? adr->in(AddPNode::Offset) : kit->top(); Node* load = CardTableBarrierSetC2::load_at_resolved(access, val_type); // If we are reading the value of the referent field of a Reference // object (either by using Unsafe directly or through reflection) // then, if G1 is enabled, we need to record the referent in an // SATB log buffer using the pre-barrier mechanism. // Also we need to add memory barrier to prevent commoning reads // from this field across safepoint since GC can change its value. bool need_read_barrier = on_heap && (on_weak || (unknown && offset != kit->top() && obj != kit->top())); if (!access.is_oop() || !need_read_barrier) { return load; } if (on_weak) { // Use the pre-barrier to record the value in the referent field pre_barrier(kit, false /* do_load */, kit->control(), NULL /* obj */, NULL /* adr */, max_juint /* alias_idx */, NULL /* val */, NULL /* val_type */, load /* pre_val */, T_OBJECT); // Add memory barrier to prevent commoning reads from this field // across safepoint since GC can change its value. kit->insert_mem_bar(Op_MemBarCPUOrder); } else if (unknown) { // We do not require a mem bar inside pre_barrier if need_mem_bar // is set: the barriers would be emitted by us. insert_pre_barrier(kit, obj, offset, load, !need_cpu_mem_bar); } return load; } bool G1BarrierSetC2::is_gc_barrier_node(Node* node) const { if (CardTableBarrierSetC2::is_gc_barrier_node(node)) { return true; } if (node->Opcode() != Op_CallLeaf) { return false; } CallLeafNode *call = node->as_CallLeaf(); if (call->_name == NULL) { return false; } return strcmp(call->_name, "g1_wb_pre") == 0 || strcmp(call->_name, "g1_wb_post") == 0; } void G1BarrierSetC2::eliminate_gc_barrier(PhaseMacroExpand* macro, Node* node) const { assert(node->Opcode() == Op_CastP2X, "ConvP2XNode required"); assert(node->outcnt() <= 2, "expects 1 or 2 users: Xor and URShift nodes"); // It could be only one user, URShift node, in Object.clone() intrinsic // but the new allocation is passed to arraycopy stub and it could not // be scalar replaced. So we don't check the case. // An other case of only one user (Xor) is when the value check for NULL // in G1 post barrier is folded after CCP so the code which used URShift // is removed. // Take Region node before eliminating post barrier since it also // eliminates CastP2X node when it has only one user. Node* this_region = node->in(0); assert(this_region != NULL, ""); // Remove G1 post barrier. // Search for CastP2X->Xor->URShift->Cmp path which // checks if the store done to a different from the value's region. // And replace Cmp with #0 (false) to collapse G1 post barrier. Node* xorx = node->find_out_with(Op_XorX); if (xorx != NULL) { Node* shift = xorx->unique_out(); Node* cmpx = shift->unique_out(); assert(cmpx->is_Cmp() && cmpx->unique_out()->is_Bool() && cmpx->unique_out()->as_Bool()->_test._test == BoolTest::ne, "missing region check in G1 post barrier"); macro->replace_node(cmpx, macro->makecon(TypeInt::CC_EQ)); // Remove G1 pre barrier. // Search "if (marking != 0)" check and set it to "false". // There is no G1 pre barrier if previous stored value is NULL // (for example, after initialization). if (this_region->is_Region() && this_region->req() == 3) { int ind = 1; if (!this_region->in(ind)->is_IfFalse()) { ind = 2; } if (this_region->in(ind)->is_IfFalse()) { Node* bol = this_region->in(ind)->in(0)->in(1); assert(bol->is_Bool(), ""); cmpx = bol->in(1); if (bol->as_Bool()->_test._test == BoolTest::ne && cmpx->is_Cmp() && cmpx->in(2) == macro->intcon(0) && cmpx->in(1)->is_Load()) { Node* adr = cmpx->in(1)->as_Load()->in(MemNode::Address); const int marking_offset = in_bytes(G1ThreadLocalData::satb_mark_queue_active_offset()); if (adr->is_AddP() && adr->in(AddPNode::Base) == macro->top() && adr->in(AddPNode::Address)->Opcode() == Op_ThreadLocal && adr->in(AddPNode::Offset) == macro->MakeConX(marking_offset)) { macro->replace_node(cmpx, macro->makecon(TypeInt::CC_EQ)); } } } } } else { assert(!use_ReduceInitialCardMarks(), "can only happen with card marking"); // This is a G1 post barrier emitted by the Object.clone() intrinsic. // Search for the CastP2X->URShiftX->AddP->LoadB->Cmp path which checks if the card // is marked as young_gen and replace the Cmp with 0 (false) to collapse the barrier. Node* shift = node->find_out_with(Op_URShiftX); assert(shift != NULL, "missing G1 post barrier"); Node* addp = shift->unique_out(); Node* load = addp->find_out_with(Op_LoadB); assert(load != NULL, "missing G1 post barrier"); Node* cmpx = load->unique_out(); assert(cmpx->is_Cmp() && cmpx->unique_out()->is_Bool() && cmpx->unique_out()->as_Bool()->_test._test == BoolTest::ne, "missing card value check in G1 post barrier"); macro->replace_node(cmpx, macro->makecon(TypeInt::CC_EQ)); // There is no G1 pre barrier in this case } // Now CastP2X can be removed since it is used only on dead path // which currently still alive until igvn optimize it. assert(node->outcnt() == 0 || node->unique_out()->Opcode() == Op_URShiftX, ""); macro->replace_node(node, macro->top()); } Node* G1BarrierSetC2::step_over_gc_barrier(Node* c) const { if (!use_ReduceInitialCardMarks() && c != NULL && c->is_Region() && c->req() == 3) { for (uint i = 1; i < c->req(); i++) { if (c->in(i) != NULL && c->in(i)->is_Region() && c->in(i)->req() == 3) { Node* r = c->in(i); for (uint j = 1; j < r->req(); j++) { if (r->in(j) != NULL && r->in(j)->is_Proj() && r->in(j)->in(0) != NULL && r->in(j)->in(0)->Opcode() == Op_CallLeaf && r->in(j)->in(0)->as_Call()->entry_point() == CAST_FROM_FN_PTR(address, SharedRuntime::g1_wb_post)) { Node* call = r->in(j)->in(0); c = c->in(i == 1 ? 2 : 1); if (c != NULL) { c = c->in(0); if (c != NULL) { c = c->in(0); assert(call->in(0) == NULL || call->in(0)->in(0) == NULL || call->in(0)->in(0)->in(0) == NULL || call->in(0)->in(0)->in(0)->in(0) == NULL || call->in(0)->in(0)->in(0)->in(0)->in(0) == NULL || c == call->in(0)->in(0)->in(0)->in(0)->in(0), "bad barrier shape"); return c; } } } } } } } return c; }