--- /dev/null 2017-03-07 11:44:12.271151064 +0100 +++ new/src/share/vm/gc/g1/c2G1BSCodeGen.cpp 2017-04-25 16:46:13.467171763 +0200 @@ -0,0 +1,736 @@ +/* + * Copyright (c) 2017, 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 "opto/arraycopynode.hpp" +#include "opto/graphKit.hpp" +#include "opto/idealKit.hpp" +#include "opto/macro.hpp" +#include "opto/type.hpp" +#include "gc/g1/c2G1BSCodeGen.hpp" +#include "gc/g1/g1BarrierSet.hpp" +#include "gc/g1/g1CardTable.hpp" +#include "gc/g1/heapRegion.hpp" +#include "utilities/macros.hpp" + +const TypeFunc *C2G1BSCodeGen::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 *C2G1BSCodeGen::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 C2G1BSCodeGen::g1_can_remove_pre_barrier(GraphKit* kit, + PhaseTransform* phase, + Node* adr, + BasicType bt, + uint adr_idx) { + 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 C2G1BSCodeGen::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) { + // 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_ctrl = NULL; + 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(JavaThread::satb_mark_queue_offset() + // 648 + SATBMarkQueue::byte_offset_of_active()); + const int index_offset = in_bytes(JavaThread::satb_mark_queue_offset() + // 656 + SATBMarkQueue::byte_offset_of_index()); + const int buffer_offset = in_bytes(JavaThread::satb_mark_queue_offset() + // 652 + SATBMarkQueue::byte_offset_of_buf()); + + // 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, G1BarrierSet::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 C2G1BSCodeGen::g1_can_remove_post_barrier(GraphKit* kit, + PhaseTransform* phase, Node* store, + Node* adr) { + 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 C2G1BSCodeGen::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) { + 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, G1BarrierSet::g1_wb_post), "g1_wb_post", card_adr, __ thread()); + } __ end_if(); + +} + +void C2G1BSCodeGen::post_barrier(GraphKit* kit, + Node* ctl, + Node* oop_store, + Node* obj, + Node* adr, + uint alias_idx, + Node* val, + BasicType bt, + bool use_precise) { + // 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(JavaThread::dirty_card_queue_offset() + + DirtyCardQueue::byte_offset_of_index()); + const int buffer_offset = in_bytes(JavaThread::dirty_card_queue_offset() + + DirtyCardQueue::byte_offset_of_buf()); + + // 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 C2G1BSCodeGen::insert_pre_barrier(GraphKit* kit, Node* base_oop, Node* offset, + Node* pre_val, bool need_mem_bar) { + // 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* C2G1BSCodeGen::load_at_resolved(GraphKit* kit, Node* obj, Node* adr, const TypePtr* adr_type, const Type* val_type, BasicType bt, C2DecoratorSet decorators) { + bool is_obj = bt == T_OBJECT || bt == T_ARRAY; + bool mismatched = (decorators & C2_MISMATCHED) != 0; + bool anonymous = (decorators & C2_ACCESS_ON_ANONYMOUS) != 0; + bool on_heap = (decorators & C2_ACCESS_ON_HEAP) != 0; + bool on_weak = (decorators & C2_ACCESS_ON_WEAK) != 0; + bool is_relaxed = (decorators & C2_MO_RELAXED) != 0; + bool need_cpu_mem_bar = !is_relaxed || mismatched || !on_heap; + + Node* offset = adr->is_AddP() ? adr->in(AddPNode::Offset) : kit->top(); + Node* load = C2CardTableModRefBSCodeGen::load_at_resolved(kit, obj, adr, adr_type, val_type, bt, decorators); + + // 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 || (anonymous && offset != kit->top() && obj != kit->top())); + + if (!is_obj || !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 (anonymous) { + // 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 C2G1BSCodeGen::is_gc_barrier_node(Node* node) { + if (C2CardTableModRefBSCodeGen::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 C2G1BSCodeGen::eliminate_gc_barrier(PhaseMacroExpand* macro, Node* node) { + 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(JavaThread::satb_mark_queue_offset() + + SATBMarkQueue::byte_offset_of_active()); + 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()); +}