/* * Copyright (c) 1999, 2011, 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 "c1/c1_Canonicalizer.hpp" #include "c1/c1_Optimizer.hpp" #include "c1/c1_ValueMap.hpp" #include "c1/c1_ValueSet.hpp" #include "c1/c1_ValueStack.hpp" #include "utilities/bitMap.inline.hpp" define_array(ValueSetArray, ValueSet*); define_stack(ValueSetList, ValueSetArray); Optimizer::Optimizer(IR* ir) { assert(ir->is_valid(), "IR must be valid"); _ir = ir; } class CE_Eliminator: public BlockClosure { private: IR* _hir; int _cee_count; // the number of CEs successfully eliminated int _ifop_count; // the number of IfOps successfully simplified int _has_substitution; public: CE_Eliminator(IR* hir) : _cee_count(0), _ifop_count(0), _hir(hir) { _has_substitution = false; _hir->iterate_preorder(this); if (_has_substitution) { // substituted some ifops/phis, so resolve the substitution SubstitutionResolver sr(_hir); } } int cee_count() const { return _cee_count; } int ifop_count() const { return _ifop_count; } void adjust_exception_edges(BlockBegin* block, BlockBegin* sux) { int e = sux->number_of_exception_handlers(); for (int i = 0; i < e; i++) { BlockBegin* xhandler = sux->exception_handler_at(i); block->add_exception_handler(xhandler); assert(xhandler->is_predecessor(sux), "missing predecessor"); if (sux->number_of_preds() == 0) { // sux is disconnected from graph so disconnect from exception handlers xhandler->remove_predecessor(sux); } if (!xhandler->is_predecessor(block)) { xhandler->add_predecessor(block); } } } virtual void block_do(BlockBegin* block); private: Value make_ifop(Value x, Instruction::Condition cond, Value y, Value tval, Value fval); }; void CE_Eliminator::block_do(BlockBegin* block) { // 1) find conditional expression // check if block ends with an If If* if_ = block->end()->as_If(); if (if_ == NULL) return; // check if If works on int or object types // (we cannot handle If's working on long, float or doubles yet, // since IfOp doesn't support them - these If's show up if cmp // operations followed by If's are eliminated) ValueType* if_type = if_->x()->type(); if (!if_type->is_int() && !if_type->is_object()) return; BlockBegin* t_block = if_->tsux(); BlockBegin* f_block = if_->fsux(); Instruction* t_cur = t_block->next(); Instruction* f_cur = f_block->next(); // one Constant may be present between BlockBegin and BlockEnd Value t_const = NULL; Value f_const = NULL; if (t_cur->as_Constant() != NULL && !t_cur->can_trap()) { t_const = t_cur; t_cur = t_cur->next(); } if (f_cur->as_Constant() != NULL && !f_cur->can_trap()) { f_const = f_cur; f_cur = f_cur->next(); } // check if both branches end with a goto Goto* t_goto = t_cur->as_Goto(); if (t_goto == NULL) return; Goto* f_goto = f_cur->as_Goto(); if (f_goto == NULL) return; // check if both gotos merge into the same block BlockBegin* sux = t_goto->default_sux(); if (sux != f_goto->default_sux()) return; // check if at least one word was pushed on sux_state // inlining depths must match ValueStack* if_state = if_->state(); ValueStack* sux_state = sux->state(); if (if_state->scope()->level() > sux_state->scope()->level()) { while (sux_state->scope() != if_state->scope()) { if_state = if_state->caller_state(); assert(if_state != NULL, "states do not match up"); } } else if (if_state->scope()->level() < sux_state->scope()->level()) { while (sux_state->scope() != if_state->scope()) { sux_state = sux_state->caller_state(); assert(sux_state != NULL, "states do not match up"); } } if (sux_state->stack_size() <= if_state->stack_size()) return; // check if phi function is present at end of successor stack and that // only this phi was pushed on the stack Value sux_phi = sux_state->stack_at(if_state->stack_size()); if (sux_phi == NULL || sux_phi->as_Phi() == NULL || sux_phi->as_Phi()->block() != sux) return; if (sux_phi->type()->size() != sux_state->stack_size() - if_state->stack_size()) return; // get the values that were pushed in the true- and false-branch Value t_value = t_goto->state()->stack_at(if_state->stack_size()); Value f_value = f_goto->state()->stack_at(if_state->stack_size()); // backend does not support floats assert(t_value->type()->base() == f_value->type()->base(), "incompatible types"); if (t_value->type()->is_float_kind()) return; // check that successor has no other phi functions but sux_phi // this can happen when t_block or f_block contained additonal stores to local variables // that are no longer represented by explicit instructions for_each_phi_fun(sux, phi, if (phi != sux_phi) return; ); // true and false blocks can't have phis for_each_phi_fun(t_block, phi, return; ); for_each_phi_fun(f_block, phi, return; ); // 2) substitute conditional expression // with an IfOp followed by a Goto // cut if_ away and get node before Instruction* cur_end = if_->prev(block); // append constants of true- and false-block if necessary // clone constants because original block must not be destroyed assert((t_value != f_const && f_value != t_const) || t_const == f_const, "mismatch"); if (t_value == t_const) { t_value = new Constant(t_const->type()); NOT_PRODUCT(t_value->set_printable_bci(if_->printable_bci())); cur_end = cur_end->set_next(t_value); } if (f_value == f_const) { f_value = new Constant(f_const->type()); NOT_PRODUCT(f_value->set_printable_bci(if_->printable_bci())); cur_end = cur_end->set_next(f_value); } Value result = make_ifop(if_->x(), if_->cond(), if_->y(), t_value, f_value); assert(result != NULL, "make_ifop must return a non-null instruction"); if (!result->is_linked() && result->can_be_linked()) { NOT_PRODUCT(result->set_printable_bci(if_->printable_bci())); cur_end = cur_end->set_next(result); } // append Goto to successor ValueStack* state_before = if_->is_safepoint() ? if_->state_before() : NULL; Goto* goto_ = new Goto(sux, state_before, if_->is_safepoint() || t_goto->is_safepoint() || f_goto->is_safepoint()); // prepare state for Goto ValueStack* goto_state = if_state; goto_state = goto_state->copy(ValueStack::StateAfter, goto_state->bci()); goto_state->push(result->type(), result); assert(goto_state->is_same(sux_state), "states must match now"); goto_->set_state(goto_state); cur_end = cur_end->set_next(goto_, goto_state->bci()); // Adjust control flow graph BlockBegin::disconnect_edge(block, t_block); BlockBegin::disconnect_edge(block, f_block); if (t_block->number_of_preds() == 0) { BlockBegin::disconnect_edge(t_block, sux); } adjust_exception_edges(block, t_block); if (f_block->number_of_preds() == 0) { BlockBegin::disconnect_edge(f_block, sux); } adjust_exception_edges(block, f_block); // update block end block->set_end(goto_); // substitute the phi if possible if (sux_phi->as_Phi()->operand_count() == 1) { assert(sux_phi->as_Phi()->operand_at(0) == result, "screwed up phi"); sux_phi->set_subst(result); _has_substitution = true; } // 3) successfully eliminated a conditional expression _cee_count++; if (PrintCEE) { tty->print_cr("%d. CEE in B%d (B%d B%d)", cee_count(), block->block_id(), t_block->block_id(), f_block->block_id()); tty->print_cr("%d. IfOp in B%d", ifop_count(), block->block_id()); } _hir->verify(); } Value CE_Eliminator::make_ifop(Value x, Instruction::Condition cond, Value y, Value tval, Value fval) { if (!OptimizeIfOps) { return new IfOp(x, cond, y, tval, fval); } tval = tval->subst(); fval = fval->subst(); if (tval == fval) { _ifop_count++; return tval; } x = x->subst(); y = y->subst(); Constant* y_const = y->as_Constant(); if (y_const != NULL) { IfOp* x_ifop = x->as_IfOp(); if (x_ifop != NULL) { // x is an ifop, y is a constant Constant* x_tval_const = x_ifop->tval()->subst()->as_Constant(); Constant* x_fval_const = x_ifop->fval()->subst()->as_Constant(); if (x_tval_const != NULL && x_fval_const != NULL) { Instruction::Condition x_ifop_cond = x_ifop->cond(); Constant::CompareResult t_compare_res = x_tval_const->compare(cond, y_const); Constant::CompareResult f_compare_res = x_fval_const->compare(cond, y_const); // not_comparable here is a valid return in case we're comparing unloaded oop constants if (t_compare_res != Constant::not_comparable && f_compare_res != Constant::not_comparable) { Value new_tval = t_compare_res == Constant::cond_true ? tval : fval; Value new_fval = f_compare_res == Constant::cond_true ? tval : fval; _ifop_count++; if (new_tval == new_fval) { return new_tval; } else { return new IfOp(x_ifop->x(), x_ifop_cond, x_ifop->y(), new_tval, new_fval); } } } } else { Constant* x_const = x->as_Constant(); if (x_const != NULL) { // x and y are constants Constant::CompareResult x_compare_res = x_const->compare(cond, y_const); // not_comparable here is a valid return in case we're comparing unloaded oop constants if (x_compare_res != Constant::not_comparable) { _ifop_count++; return x_compare_res == Constant::cond_true ? tval : fval; } } } } return new IfOp(x, cond, y, tval, fval); } void Optimizer::eliminate_conditional_expressions() { // find conditional expressions & replace them with IfOps CE_Eliminator ce(ir()); } class BlockMerger: public BlockClosure { private: IR* _hir; int _merge_count; // the number of block pairs successfully merged public: BlockMerger(IR* hir) : _hir(hir) , _merge_count(0) { _hir->iterate_preorder(this); } bool try_merge(BlockBegin* block) { BlockEnd* end = block->end(); if (end->as_Goto() != NULL) { assert(end->number_of_sux() == 1, "end must have exactly one successor"); // Note: It would be sufficient to check for the number of successors (= 1) // in order to decide if this block can be merged potentially. That // would then also include switch statements w/ only a default case. // However, in that case we would need to make sure the switch tag // expression is executed if it can produce observable side effects. // We should probably have the canonicalizer simplifying such switch // statements and then we are sure we don't miss these merge opportunities // here (was bug - gri 7/7/99). BlockBegin* sux = end->default_sux(); if (sux->number_of_preds() == 1 && !sux->is_entry_block() && !end->is_safepoint()) { // merge the two blocks #ifdef ASSERT // verify that state at the end of block and at the beginning of sux are equal // no phi functions must be present at beginning of sux ValueStack* sux_state = sux->state(); ValueStack* end_state = end->state(); assert(end_state->scope() == sux_state->scope(), "scopes must match"); assert(end_state->stack_size() == sux_state->stack_size(), "stack not equal"); assert(end_state->locals_size() == sux_state->locals_size(), "locals not equal"); int index; Value sux_value; for_each_stack_value(sux_state, index, sux_value) { assert(sux_value == end_state->stack_at(index), "stack not equal"); } for_each_local_value(sux_state, index, sux_value) { assert(sux_value == end_state->local_at(index), "locals not equal"); } assert(sux_state->caller_state() == end_state->caller_state(), "caller not equal"); #endif // find instruction before end & append first instruction of sux block Instruction* prev = end->prev(block); Instruction* next = sux->next(); assert(prev->as_BlockEnd() == NULL, "must not be a BlockEnd"); prev->set_next(next); sux->disconnect_from_graph(); block->set_end(sux->end()); // add exception handlers of deleted block, if any for (int k = 0; k < sux->number_of_exception_handlers(); k++) { BlockBegin* xhandler = sux->exception_handler_at(k); block->add_exception_handler(xhandler); // also substitute predecessor of exception handler assert(xhandler->is_predecessor(sux), "missing predecessor"); xhandler->remove_predecessor(sux); if (!xhandler->is_predecessor(block)) { xhandler->add_predecessor(block); } } // debugging output _merge_count++; if (PrintBlockElimination) { tty->print_cr("%d. merged B%d & B%d (stack size = %d)", _merge_count, block->block_id(), sux->block_id(), sux->state()->stack_size()); } _hir->verify(); If* if_ = block->end()->as_If(); if (if_) { IfOp* ifop = if_->x()->as_IfOp(); Constant* con = if_->y()->as_Constant(); bool swapped = false; if (!con || !ifop) { ifop = if_->y()->as_IfOp(); con = if_->x()->as_Constant(); swapped = true; } if (con && ifop) { Constant* tval = ifop->tval()->as_Constant(); Constant* fval = ifop->fval()->as_Constant(); if (tval && fval) { // Find the instruction before if_, starting with ifop. // When if_ and ifop are not in the same block, prev // becomes NULL In such (rare) cases it is not // profitable to perform the optimization. Value prev = ifop; while (prev != NULL && prev->next() != if_) { prev = prev->next(); } if (prev != NULL) { Instruction::Condition cond = if_->cond(); BlockBegin* tsux = if_->tsux(); BlockBegin* fsux = if_->fsux(); if (swapped) { cond = Instruction::mirror(cond); } BlockBegin* tblock = tval->compare(cond, con, tsux, fsux); BlockBegin* fblock = fval->compare(cond, con, tsux, fsux); if (tblock != fblock && !if_->is_safepoint()) { If* newif = new If(ifop->x(), ifop->cond(), false, ifop->y(), tblock, fblock, if_->state_before(), if_->is_safepoint()); newif->set_state(if_->state()->copy()); assert(prev->next() == if_, "must be guaranteed by above search"); NOT_PRODUCT(newif->set_printable_bci(if_->printable_bci())); prev->set_next(newif); block->set_end(newif); _merge_count++; if (PrintBlockElimination) { tty->print_cr("%d. replaced If and IfOp at end of B%d with single If", _merge_count, block->block_id()); } _hir->verify(); } } } } } return true; } } return false; } virtual void block_do(BlockBegin* block) { _hir->verify(); // repeat since the same block may merge again while (try_merge(block)) { _hir->verify(); } } }; void Optimizer::eliminate_blocks() { // merge blocks if possible BlockMerger bm(ir()); } class NullCheckEliminator; class NullCheckVisitor: public InstructionVisitor { private: NullCheckEliminator* _nce; NullCheckEliminator* nce() { return _nce; } public: NullCheckVisitor() {} void set_eliminator(NullCheckEliminator* nce) { _nce = nce; } void do_Phi (Phi* x); void do_Local (Local* x); void do_Constant (Constant* x); void do_LoadField (LoadField* x); void do_StoreField (StoreField* x); void do_ArrayLength (ArrayLength* x); void do_LoadIndexed (LoadIndexed* x); void do_StoreIndexed (StoreIndexed* x); void do_NegateOp (NegateOp* x); void do_ArithmeticOp (ArithmeticOp* x); void do_ShiftOp (ShiftOp* x); void do_LogicOp (LogicOp* x); void do_CompareOp (CompareOp* x); void do_IfOp (IfOp* x); void do_Convert (Convert* x); void do_NullCheck (NullCheck* x); void do_Invoke (Invoke* x); void do_NewInstance (NewInstance* x); void do_NewTypeArray (NewTypeArray* x); void do_NewObjectArray (NewObjectArray* x); void do_NewMultiArray (NewMultiArray* x); void do_CheckCast (CheckCast* x); void do_InstanceOf (InstanceOf* x); void do_MonitorEnter (MonitorEnter* x); void do_MonitorExit (MonitorExit* x); void do_Intrinsic (Intrinsic* x); void do_BlockBegin (BlockBegin* x); void do_Goto (Goto* x); void do_If (If* x); void do_IfInstanceOf (IfInstanceOf* x); void do_TableSwitch (TableSwitch* x); void do_LookupSwitch (LookupSwitch* x); void do_Return (Return* x); void do_Throw (Throw* x); void do_Base (Base* x); void do_OsrEntry (OsrEntry* x); void do_ExceptionObject(ExceptionObject* x); void do_RoundFP (RoundFP* x); void do_UnsafeGetRaw (UnsafeGetRaw* x); void do_UnsafePutRaw (UnsafePutRaw* x); void do_UnsafeGetObject(UnsafeGetObject* x); void do_UnsafePutObject(UnsafePutObject* x); void do_UnsafePrefetchRead (UnsafePrefetchRead* x); void do_UnsafePrefetchWrite(UnsafePrefetchWrite* x); void do_ProfileCall (ProfileCall* x); void do_ProfileInvoke (ProfileInvoke* x); void do_RuntimeCall (RuntimeCall* x); void do_MemBar (MemBar* x); }; // Because of a static contained within (for the purpose of iteration // over instructions), it is only valid to have one of these active at // a time class NullCheckEliminator: public ValueVisitor { private: Optimizer* _opt; ValueSet* _visitable_instructions; // Visit each instruction only once per basic block BlockList* _work_list; // Basic blocks to visit bool visitable(Value x) { assert(_visitable_instructions != NULL, "check"); return _visitable_instructions->contains(x); } void mark_visited(Value x) { assert(_visitable_instructions != NULL, "check"); _visitable_instructions->remove(x); } void mark_visitable(Value x) { assert(_visitable_instructions != NULL, "check"); _visitable_instructions->put(x); } void clear_visitable_state() { assert(_visitable_instructions != NULL, "check"); _visitable_instructions->clear(); } ValueSet* _set; // current state, propagated to subsequent BlockBegins ValueSetList _block_states; // BlockBegin null-check states for all processed blocks NullCheckVisitor _visitor; NullCheck* _last_explicit_null_check; bool set_contains(Value x) { assert(_set != NULL, "check"); return _set->contains(x); } void set_put (Value x) { assert(_set != NULL, "check"); _set->put(x); } void set_remove (Value x) { assert(_set != NULL, "check"); _set->remove(x); } BlockList* work_list() { return _work_list; } void iterate_all(); void iterate_one(BlockBegin* block); ValueSet* state() { return _set; } void set_state_from (ValueSet* state) { _set->set_from(state); } ValueSet* state_for (BlockBegin* block) { return _block_states[block->block_id()]; } void set_state_for (BlockBegin* block, ValueSet* stack) { _block_states[block->block_id()] = stack; } // Returns true if caused a change in the block's state. bool merge_state_for(BlockBegin* block, ValueSet* incoming_state); public: // constructor NullCheckEliminator(Optimizer* opt) : _opt(opt) , _set(new ValueSet()) , _last_explicit_null_check(NULL) , _block_states(BlockBegin::number_of_blocks(), NULL) , _work_list(new BlockList()) { _visitable_instructions = new ValueSet(); _visitor.set_eliminator(this); } Optimizer* opt() { return _opt; } IR* ir () { return opt()->ir(); } // Process a graph void iterate(BlockBegin* root); void visit(Value* f); // In some situations (like NullCheck(x); getfield(x)) the debug // information from the explicit NullCheck can be used to populate // the getfield, even if the two instructions are in different // scopes; this allows implicit null checks to be used but the // correct exception information to be generated. We must clear the // last-traversed NullCheck when we reach a potentially-exception- // throwing instruction, as well as in some other cases. void set_last_explicit_null_check(NullCheck* check) { _last_explicit_null_check = check; } NullCheck* last_explicit_null_check() { return _last_explicit_null_check; } Value last_explicit_null_check_obj() { return (_last_explicit_null_check ? _last_explicit_null_check->obj() : NULL); } NullCheck* consume_last_explicit_null_check() { _last_explicit_null_check->unpin(Instruction::PinExplicitNullCheck); _last_explicit_null_check->set_can_trap(false); return _last_explicit_null_check; } void clear_last_explicit_null_check() { _last_explicit_null_check = NULL; } // Handlers for relevant instructions // (separated out from NullCheckVisitor for clarity) // The basic contract is that these must leave the instruction in // the desired state; must not assume anything about the state of // the instruction. We make multiple passes over some basic blocks // and the last pass is the only one whose result is valid. void handle_AccessField (AccessField* x); void handle_ArrayLength (ArrayLength* x); void handle_LoadIndexed (LoadIndexed* x); void handle_StoreIndexed (StoreIndexed* x); void handle_NullCheck (NullCheck* x); void handle_Invoke (Invoke* x); void handle_NewInstance (NewInstance* x); void handle_NewArray (NewArray* x); void handle_AccessMonitor (AccessMonitor* x); void handle_Intrinsic (Intrinsic* x); void handle_ExceptionObject (ExceptionObject* x); void handle_Phi (Phi* x); }; // NEEDS_CLEANUP // There may be other instructions which need to clear the last // explicit null check. Anything across which we can not hoist the // debug information for a NullCheck instruction must clear it. It // might be safer to pattern match "NullCheck ; {AccessField, // ArrayLength, LoadIndexed}" but it is more easily structured this way. // Should test to see performance hit of clearing it for all handlers // with empty bodies below. If it is negligible then we should leave // that in for safety, otherwise should think more about it. void NullCheckVisitor::do_Phi (Phi* x) { nce()->handle_Phi(x); } void NullCheckVisitor::do_Local (Local* x) {} void NullCheckVisitor::do_Constant (Constant* x) { /* FIXME: handle object constants */ } void NullCheckVisitor::do_LoadField (LoadField* x) { nce()->handle_AccessField(x); } void NullCheckVisitor::do_StoreField (StoreField* x) { nce()->handle_AccessField(x); } void NullCheckVisitor::do_ArrayLength (ArrayLength* x) { nce()->handle_ArrayLength(x); } void NullCheckVisitor::do_LoadIndexed (LoadIndexed* x) { nce()->handle_LoadIndexed(x); } void NullCheckVisitor::do_StoreIndexed (StoreIndexed* x) { nce()->handle_StoreIndexed(x); } void NullCheckVisitor::do_NegateOp (NegateOp* x) {} void NullCheckVisitor::do_ArithmeticOp (ArithmeticOp* x) { if (x->can_trap()) nce()->clear_last_explicit_null_check(); } void NullCheckVisitor::do_ShiftOp (ShiftOp* x) {} void NullCheckVisitor::do_LogicOp (LogicOp* x) {} void NullCheckVisitor::do_CompareOp (CompareOp* x) {} void NullCheckVisitor::do_IfOp (IfOp* x) {} void NullCheckVisitor::do_Convert (Convert* x) {} void NullCheckVisitor::do_NullCheck (NullCheck* x) { nce()->handle_NullCheck(x); } void NullCheckVisitor::do_Invoke (Invoke* x) { nce()->handle_Invoke(x); } void NullCheckVisitor::do_NewInstance (NewInstance* x) { nce()->handle_NewInstance(x); } void NullCheckVisitor::do_NewTypeArray (NewTypeArray* x) { nce()->handle_NewArray(x); } void NullCheckVisitor::do_NewObjectArray (NewObjectArray* x) { nce()->handle_NewArray(x); } void NullCheckVisitor::do_NewMultiArray (NewMultiArray* x) { nce()->handle_NewArray(x); } void NullCheckVisitor::do_CheckCast (CheckCast* x) { nce()->clear_last_explicit_null_check(); } void NullCheckVisitor::do_InstanceOf (InstanceOf* x) {} void NullCheckVisitor::do_MonitorEnter (MonitorEnter* x) { nce()->handle_AccessMonitor(x); } void NullCheckVisitor::do_MonitorExit (MonitorExit* x) { nce()->handle_AccessMonitor(x); } void NullCheckVisitor::do_Intrinsic (Intrinsic* x) { nce()->handle_Intrinsic(x); } void NullCheckVisitor::do_BlockBegin (BlockBegin* x) {} void NullCheckVisitor::do_Goto (Goto* x) {} void NullCheckVisitor::do_If (If* x) {} void NullCheckVisitor::do_IfInstanceOf (IfInstanceOf* x) {} void NullCheckVisitor::do_TableSwitch (TableSwitch* x) {} void NullCheckVisitor::do_LookupSwitch (LookupSwitch* x) {} void NullCheckVisitor::do_Return (Return* x) {} void NullCheckVisitor::do_Throw (Throw* x) { nce()->clear_last_explicit_null_check(); } void NullCheckVisitor::do_Base (Base* x) {} void NullCheckVisitor::do_OsrEntry (OsrEntry* x) {} void NullCheckVisitor::do_ExceptionObject(ExceptionObject* x) { nce()->handle_ExceptionObject(x); } void NullCheckVisitor::do_RoundFP (RoundFP* x) {} void NullCheckVisitor::do_UnsafeGetRaw (UnsafeGetRaw* x) {} void NullCheckVisitor::do_UnsafePutRaw (UnsafePutRaw* x) {} void NullCheckVisitor::do_UnsafeGetObject(UnsafeGetObject* x) {} void NullCheckVisitor::do_UnsafePutObject(UnsafePutObject* x) {} void NullCheckVisitor::do_UnsafePrefetchRead (UnsafePrefetchRead* x) {} void NullCheckVisitor::do_UnsafePrefetchWrite(UnsafePrefetchWrite* x) {} void NullCheckVisitor::do_ProfileCall (ProfileCall* x) { nce()->clear_last_explicit_null_check(); } void NullCheckVisitor::do_ProfileInvoke (ProfileInvoke* x) {} void NullCheckVisitor::do_RuntimeCall (RuntimeCall* x) {} void NullCheckVisitor::do_MemBar (MemBar* x) {} void NullCheckEliminator::visit(Value* p) { assert(*p != NULL, "should not find NULL instructions"); if (visitable(*p)) { mark_visited(*p); (*p)->visit(&_visitor); } } bool NullCheckEliminator::merge_state_for(BlockBegin* block, ValueSet* incoming_state) { ValueSet* state = state_for(block); if (state == NULL) { state = incoming_state->copy(); set_state_for(block, state); return true; } else { bool changed = state->set_intersect(incoming_state); if (PrintNullCheckElimination && changed) { tty->print_cr("Block %d's null check state changed", block->block_id()); } return changed; } } void NullCheckEliminator::iterate_all() { while (work_list()->length() > 0) { iterate_one(work_list()->pop()); } } void NullCheckEliminator::iterate_one(BlockBegin* block) { clear_visitable_state(); // clear out an old explicit null checks set_last_explicit_null_check(NULL); if (PrintNullCheckElimination) { tty->print_cr(" ...iterating block %d in null check elimination for %s::%s%s", block->block_id(), ir()->method()->holder()->name()->as_utf8(), ir()->method()->name()->as_utf8(), ir()->method()->signature()->as_symbol()->as_utf8()); } // Create new state if none present (only happens at root) if (state_for(block) == NULL) { ValueSet* tmp_state = new ValueSet(); set_state_for(block, tmp_state); // Initial state is that local 0 (receiver) is non-null for // non-static methods ValueStack* stack = block->state(); IRScope* scope = stack->scope(); ciMethod* method = scope->method(); if (!method->is_static()) { Local* local0 = stack->local_at(0)->as_Local(); assert(local0 != NULL, "must be"); assert(local0->type() == objectType, "invalid type of receiver"); if (local0 != NULL) { // Local 0 is used in this scope tmp_state->put(local0); if (PrintNullCheckElimination) { tty->print_cr("Local 0 (value %d) proven non-null upon entry", local0->id()); } } } } // Must copy block's state to avoid mutating it during iteration // through the block -- otherwise "not-null" states can accidentally // propagate "up" through the block during processing of backward // branches and algorithm is incorrect (and does not converge) set_state_from(state_for(block)); // allow visiting of Phis belonging to this block for_each_phi_fun(block, phi, mark_visitable(phi); ); BlockEnd* e = block->end(); assert(e != NULL, "incomplete graph"); int i; // Propagate the state before this block into the exception // handlers. They aren't true successors since we aren't guaranteed // to execute the whole block before executing them. Also putting // them on first seems to help reduce the amount of iteration to // reach a fixed point. for (i = 0; i < block->number_of_exception_handlers(); i++) { BlockBegin* next = block->exception_handler_at(i); if (merge_state_for(next, state())) { if (!work_list()->contains(next)) { work_list()->push(next); } } } // Iterate through block, updating state. for (Instruction* instr = block; instr != NULL; instr = instr->next()) { // Mark instructions in this block as visitable as they are seen // in the instruction list. This keeps the iteration from // visiting instructions which are references in other blocks or // visiting instructions more than once. mark_visitable(instr); if (instr->is_pinned() || instr->can_trap() || (instr->as_NullCheck() != NULL)) { mark_visited(instr); instr->input_values_do(this); instr->visit(&_visitor); } } // Propagate state to successors if necessary for (i = 0; i < e->number_of_sux(); i++) { BlockBegin* next = e->sux_at(i); if (merge_state_for(next, state())) { if (!work_list()->contains(next)) { work_list()->push(next); } } } } void NullCheckEliminator::iterate(BlockBegin* block) { work_list()->push(block); iterate_all(); } void NullCheckEliminator::handle_AccessField(AccessField* x) { if (x->is_static()) { if (x->as_LoadField() != NULL) { // If the field is a non-null static final object field (as is // often the case for sun.misc.Unsafe), put this LoadField into // the non-null map ciField* field = x->field(); if (field->is_constant()) { ciConstant field_val = field->constant_value(); BasicType field_type = field_val.basic_type(); if (field_type == T_OBJECT || field_type == T_ARRAY) { ciObject* obj_val = field_val.as_object(); if (!obj_val->is_null_object()) { if (PrintNullCheckElimination) { tty->print_cr("AccessField %d proven non-null by static final non-null oop check", x->id()); } set_put(x); } } } } // Be conservative clear_last_explicit_null_check(); return; } Value obj = x->obj(); if (set_contains(obj)) { // Value is non-null => update AccessField if (last_explicit_null_check_obj() == obj && !x->needs_patching()) { x->set_explicit_null_check(consume_last_explicit_null_check()); x->set_needs_null_check(true); if (PrintNullCheckElimination) { tty->print_cr("Folded NullCheck %d into AccessField %d's null check for value %d", x->explicit_null_check()->id(), x->id(), obj->id()); } } else { x->set_explicit_null_check(NULL); x->set_needs_null_check(false); if (PrintNullCheckElimination) { tty->print_cr("Eliminated AccessField %d's null check for value %d", x->id(), obj->id()); } } } else { set_put(obj); if (PrintNullCheckElimination) { tty->print_cr("AccessField %d of value %d proves value to be non-null", x->id(), obj->id()); } // Ensure previous passes do not cause wrong state x->set_needs_null_check(true); x->set_explicit_null_check(NULL); } clear_last_explicit_null_check(); } void NullCheckEliminator::handle_ArrayLength(ArrayLength* x) { Value array = x->array(); if (set_contains(array)) { // Value is non-null => update AccessArray if (last_explicit_null_check_obj() == array) { x->set_explicit_null_check(consume_last_explicit_null_check()); x->set_needs_null_check(true); if (PrintNullCheckElimination) { tty->print_cr("Folded NullCheck %d into ArrayLength %d's null check for value %d", x->explicit_null_check()->id(), x->id(), array->id()); } } else { x->set_explicit_null_check(NULL); x->set_needs_null_check(false); if (PrintNullCheckElimination) { tty->print_cr("Eliminated ArrayLength %d's null check for value %d", x->id(), array->id()); } } } else { set_put(array); if (PrintNullCheckElimination) { tty->print_cr("ArrayLength %d of value %d proves value to be non-null", x->id(), array->id()); } // Ensure previous passes do not cause wrong state x->set_needs_null_check(true); x->set_explicit_null_check(NULL); } clear_last_explicit_null_check(); } void NullCheckEliminator::handle_LoadIndexed(LoadIndexed* x) { Value array = x->array(); if (set_contains(array)) { // Value is non-null => update AccessArray if (last_explicit_null_check_obj() == array) { x->set_explicit_null_check(consume_last_explicit_null_check()); x->set_needs_null_check(true); if (PrintNullCheckElimination) { tty->print_cr("Folded NullCheck %d into LoadIndexed %d's null check for value %d", x->explicit_null_check()->id(), x->id(), array->id()); } } else { x->set_explicit_null_check(NULL); x->set_needs_null_check(false); if (PrintNullCheckElimination) { tty->print_cr("Eliminated LoadIndexed %d's null check for value %d", x->id(), array->id()); } } } else { set_put(array); if (PrintNullCheckElimination) { tty->print_cr("LoadIndexed %d of value %d proves value to be non-null", x->id(), array->id()); } // Ensure previous passes do not cause wrong state x->set_needs_null_check(true); x->set_explicit_null_check(NULL); } clear_last_explicit_null_check(); } void NullCheckEliminator::handle_StoreIndexed(StoreIndexed* x) { Value array = x->array(); if (set_contains(array)) { // Value is non-null => update AccessArray if (PrintNullCheckElimination) { tty->print_cr("Eliminated StoreIndexed %d's null check for value %d", x->id(), array->id()); } x->set_needs_null_check(false); } else { set_put(array); if (PrintNullCheckElimination) { tty->print_cr("StoreIndexed %d of value %d proves value to be non-null", x->id(), array->id()); } // Ensure previous passes do not cause wrong state x->set_needs_null_check(true); } clear_last_explicit_null_check(); } void NullCheckEliminator::handle_NullCheck(NullCheck* x) { Value obj = x->obj(); if (set_contains(obj)) { // Already proven to be non-null => this NullCheck is useless if (PrintNullCheckElimination) { tty->print_cr("Eliminated NullCheck %d for value %d", x->id(), obj->id()); } // Don't unpin since that may shrink obj's live range and make it unavailable for debug info. // The code generator won't emit LIR for a NullCheck that cannot trap. x->set_can_trap(false); } else { // May be null => add to map and set last explicit NullCheck x->set_can_trap(true); // make sure it's pinned if it can trap x->pin(Instruction::PinExplicitNullCheck); set_put(obj); set_last_explicit_null_check(x); if (PrintNullCheckElimination) { tty->print_cr("NullCheck %d of value %d proves value to be non-null", x->id(), obj->id()); } } } void NullCheckEliminator::handle_Invoke(Invoke* x) { if (!x->has_receiver()) { // Be conservative clear_last_explicit_null_check(); return; } Value recv = x->receiver(); if (!set_contains(recv)) { set_put(recv); if (PrintNullCheckElimination) { tty->print_cr("Invoke %d of value %d proves value to be non-null", x->id(), recv->id()); } } clear_last_explicit_null_check(); } void NullCheckEliminator::handle_NewInstance(NewInstance* x) { set_put(x); if (PrintNullCheckElimination) { tty->print_cr("NewInstance %d is non-null", x->id()); } } void NullCheckEliminator::handle_NewArray(NewArray* x) { set_put(x); if (PrintNullCheckElimination) { tty->print_cr("NewArray %d is non-null", x->id()); } } void NullCheckEliminator::handle_ExceptionObject(ExceptionObject* x) { set_put(x); if (PrintNullCheckElimination) { tty->print_cr("ExceptionObject %d is non-null", x->id()); } } void NullCheckEliminator::handle_AccessMonitor(AccessMonitor* x) { Value obj = x->obj(); if (set_contains(obj)) { // Value is non-null => update AccessMonitor if (PrintNullCheckElimination) { tty->print_cr("Eliminated AccessMonitor %d's null check for value %d", x->id(), obj->id()); } x->set_needs_null_check(false); } else { set_put(obj); if (PrintNullCheckElimination) { tty->print_cr("AccessMonitor %d of value %d proves value to be non-null", x->id(), obj->id()); } // Ensure previous passes do not cause wrong state x->set_needs_null_check(true); } clear_last_explicit_null_check(); } void NullCheckEliminator::handle_Intrinsic(Intrinsic* x) { if (!x->has_receiver()) { if (x->id() == vmIntrinsics::_arraycopy) { for (int i = 0; i < x->number_of_arguments(); i++) { x->set_arg_needs_null_check(i, !set_contains(x->argument_at(i))); } } // Be conservative clear_last_explicit_null_check(); return; } Value recv = x->receiver(); if (set_contains(recv)) { // Value is non-null => update Intrinsic if (PrintNullCheckElimination) { tty->print_cr("Eliminated Intrinsic %d's null check for value %d", x->id(), recv->id()); } x->set_needs_null_check(false); } else { set_put(recv); if (PrintNullCheckElimination) { tty->print_cr("Intrinsic %d of value %d proves value to be non-null", x->id(), recv->id()); } // Ensure previous passes do not cause wrong state x->set_needs_null_check(true); } clear_last_explicit_null_check(); } void NullCheckEliminator::handle_Phi(Phi* x) { int i; bool all_non_null = true; if (x->is_illegal()) { all_non_null = false; } else { for (i = 0; i < x->operand_count(); i++) { Value input = x->operand_at(i); if (!set_contains(input)) { all_non_null = false; } } } if (all_non_null) { // Value is non-null => update Phi if (PrintNullCheckElimination) { tty->print_cr("Eliminated Phi %d's null check for phifun because all inputs are non-null", x->id()); } x->set_needs_null_check(false); } else if (set_contains(x)) { set_remove(x); } } void Optimizer::eliminate_null_checks() { ResourceMark rm; NullCheckEliminator nce(this); if (PrintNullCheckElimination) { tty->print_cr("Starting null check elimination for method %s::%s%s", ir()->method()->holder()->name()->as_utf8(), ir()->method()->name()->as_utf8(), ir()->method()->signature()->as_symbol()->as_utf8()); } // Apply to graph nce.iterate(ir()->start()); // walk over the graph looking for exception // handlers and iterate over them as well int nblocks = BlockBegin::number_of_blocks(); BlockList blocks(nblocks); boolArray visited_block(nblocks, false); blocks.push(ir()->start()); visited_block[ir()->start()->block_id()] = true; for (int i = 0; i < blocks.length(); i++) { BlockBegin* b = blocks[i]; // exception handlers need to be treated as additional roots for (int e = b->number_of_exception_handlers(); e-- > 0; ) { BlockBegin* excp = b->exception_handler_at(e); int id = excp->block_id(); if (!visited_block[id]) { blocks.push(excp); visited_block[id] = true; nce.iterate(excp); } } // traverse successors BlockEnd *end = b->end(); for (int s = end->number_of_sux(); s-- > 0; ) { BlockBegin* next = end->sux_at(s); int id = next->block_id(); if (!visited_block[id]) { blocks.push(next); visited_block[id] = true; } } } if (PrintNullCheckElimination) { tty->print_cr("Done with null check elimination for method %s::%s%s", ir()->method()->holder()->name()->as_utf8(), ir()->method()->name()->as_utf8(), ir()->method()->signature()->as_symbol()->as_utf8()); } }