Mercurial > hg > truffle
diff src/share/vm/c1/c1_Optimizer.cpp @ 0:a61af66fc99e jdk7-b24
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author | duke |
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date | Sat, 01 Dec 2007 00:00:00 +0000 |
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children | 80206b8a9128 |
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--- /dev/null Thu Jan 01 00:00:00 1970 +0000 +++ b/src/share/vm/c1/c1_Optimizer.cpp Sat Dec 01 00:00:00 2007 +0000 @@ -0,0 +1,1070 @@ +/* + * Copyright 1999-2006 Sun Microsystems, Inc. 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 Sun Microsystems, Inc., 4150 Network Circle, Santa Clara, + * CA 95054 USA or visit www.sun.com if you need additional information or + * have any questions. + * + */ + +#include "incls/_precompiled.incl" +#include "incls/_c1_Optimizer.cpp.incl" + +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 _has_substitution; + + public: + CE_Eliminator(IR* hir) : _cee_count(0), _hir(hir) { + _has_substitution = false; + _hir->iterate_preorder(this); + if (_has_substitution) { + // substituted some phis so resolve the substitution + SubstitutionResolver sr(_hir); + } + } + int cee_count() const { return _cee_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) { + // 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 + ValueStack* sux_state = sux->state(); + 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); + int bci = if_->bci(); + + // 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()); + cur_end = cur_end->set_next(t_value, bci); + } + if (f_value == f_const) { + f_value = new Constant(f_const->type()); + cur_end = cur_end->set_next(f_value, bci); + } + + // it is very unlikely that the condition can be statically decided + // (this was checked previously by the Canonicalizer), so always + // append IfOp + Value result = new IfOp(if_->x(), if_->cond(), if_->y(), t_value, f_value); + cur_end = cur_end->set_next(result, bci); + + // 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(); + while (sux_state->scope() != goto_state->scope()) { + goto_state = goto_state->pop_scope(); + assert(goto_state != NULL, "states do not match up"); + } + goto_state = goto_state->copy(); + goto_state->push(result->type(), result); + assert(goto_state->is_same_across_scopes(sux_state), "states must match now"); + goto_->set_state(goto_state); + + // Steal the bci for the goto from the sux + cur_end = cur_end->set_next(goto_, sux->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()); + } + + _hir->verify(); + } +}; + + +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(); + while (end_state->scope() != sux_state->scope()) { + // match up inlining level + end_state = end_state->pop_scope(); + } + 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, next->bci()); + 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); + tsux = if_->fsux(); + fsux = if_->tsux(); + } + + 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"); + prev->set_next(newif, if_->bci()); + 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_ProfileCounter (ProfileCounter* 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 { + private: + static NullCheckEliminator* _static_nce; + static void do_value(Value* vp); + + 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); + + // 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) {} +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()->clear_last_explicit_null_check(); } +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_ProfileCounter (ProfileCounter* x) {} + + +NullCheckEliminator* NullCheckEliminator::_static_nce = NULL; + + +void NullCheckEliminator::do_value(Value* p) { + assert(*p != NULL, "should not find NULL instructions"); + if (_static_nce->visitable(*p)) { + _static_nce->mark_visited(*p); + (*p)->visit(&_static_nce->_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) { + _static_nce = this; + 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_root() || instr->can_trap() || (instr->as_NullCheck() != NULL)) { + mark_visited(instr); + instr->input_values_do(&NullCheckEliminator::do_value); + 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()) { + // 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()); + } +}