8213469: Remove/fix leftovers from JDK-8213384: Move G1/C2 barrier verification into G1BarrierSetC2
Reviewed-by: kvn, roland
/*
* 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/g1BarrierSetRuntime.hpp"
#include "gc/g1/g1CardTable.hpp"
#include "gc/g1/g1ThreadLocalData.hpp"
#include "gc/g1/heapRegion.hpp"
#include "opto/arraycopynode.hpp"
#include "opto/compile.hpp"
#include "opto/graphKit.hpp"
#include "opto/idealKit.hpp"
#include "opto/macro.hpp"
#include "opto/rootnode.hpp"
#include "opto/type.hpp"
#include "utilities/macros.hpp"
const TypeFunc *G1BarrierSetC2::write_ref_field_pre_entry_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::write_ref_field_post_entry_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 = write_ref_field_pre_entry_Type();
__ make_leaf_call(tf, CAST_FROM_FN_PTR(address, G1BarrierSetRuntime::write_ref_field_pre_entry), "write_ref_field_pre_entry", 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, G1BarrierSetRuntime::write_ref_field_post_entry), "write_ref_field_post_entry", 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 = write_ref_field_post_entry_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();
Node* adr = access.addr().node();
Node* obj = access.base();
bool mismatched = (decorators & C2_MISMATCHED) != 0;
bool unknown = (decorators & ON_UNKNOWN_OOP_REF) != 0;
bool in_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 || !in_heap;
Node* top = Compile::current()->top();
Node* offset = adr->is_AddP() ? adr->in(AddPNode::Offset) : 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 = in_heap && (on_weak ||
(unknown && offset != top && obj != top));
if (!access.is_oop() || !need_read_barrier) {
return load;
}
assert(access.is_parse_access(), "entry not supported at optimization time");
C2ParseAccess& parse_access = static_cast<C2ParseAccess&>(access);
GraphKit* kit = parse_access.kit();
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, "write_ref_field_pre_entry") == 0 || strcmp(call->_name, "write_ref_field_post_entry") == 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() &&
this_region->in(ind)->in(0)->Opcode() == Op_If) {
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, G1BarrierSetRuntime::write_ref_field_post_entry)) {
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;
}
#ifdef ASSERT
void G1BarrierSetC2::verify_gc_barriers(Compile* compile, CompilePhase phase) const {
if (phase != BarrierSetC2::BeforeCodeGen) {
return;
}
// Verify G1 pre-barriers
const int marking_offset = in_bytes(G1ThreadLocalData::satb_mark_queue_active_offset());
ResourceArea *area = Thread::current()->resource_area();
Unique_Node_List visited(area);
Node_List worklist(area);
// We're going to walk control flow backwards starting from the Root
worklist.push(compile->root());
while (worklist.size() > 0) {
Node* x = worklist.pop();
if (x == NULL || x == compile->top()) continue;
if (visited.member(x)) {
continue;
} else {
visited.push(x);
}
if (x->is_Region()) {
for (uint i = 1; i < x->req(); i++) {
worklist.push(x->in(i));
}
} else {
worklist.push(x->in(0));
// We are looking for the pattern:
// /->ThreadLocal
// If->Bool->CmpI->LoadB->AddP->ConL(marking_offset)
// \->ConI(0)
// We want to verify that the If and the LoadB have the same control
// See GraphKit::g1_write_barrier_pre()
if (x->is_If()) {
IfNode *iff = x->as_If();
if (iff->in(1)->is_Bool() && iff->in(1)->in(1)->is_Cmp()) {
CmpNode *cmp = iff->in(1)->in(1)->as_Cmp();
if (cmp->Opcode() == Op_CmpI && cmp->in(2)->is_Con() && cmp->in(2)->bottom_type()->is_int()->get_con() == 0
&& cmp->in(1)->is_Load()) {
LoadNode* load = cmp->in(1)->as_Load();
if (load->Opcode() == Op_LoadB && load->in(2)->is_AddP() && load->in(2)->in(2)->Opcode() == Op_ThreadLocal
&& load->in(2)->in(3)->is_Con()
&& load->in(2)->in(3)->bottom_type()->is_intptr_t()->get_con() == marking_offset) {
Node* if_ctrl = iff->in(0);
Node* load_ctrl = load->in(0);
if (if_ctrl != load_ctrl) {
// Skip possible CProj->NeverBranch in infinite loops
if ((if_ctrl->is_Proj() && if_ctrl->Opcode() == Op_CProj)
&& (if_ctrl->in(0)->is_MultiBranch() && if_ctrl->in(0)->Opcode() == Op_NeverBranch)) {
if_ctrl = if_ctrl->in(0)->in(0);
}
}
assert(load_ctrl != NULL && if_ctrl == load_ctrl, "controls must match");
}
}
}
}
}
}
}
#endif