--- /dev/null Thu Jan 01 00:00:00 1970 +0000
+++ b/src/hotspot/share/c1/c1_Optimizer.cpp Tue Sep 12 19:03:39 2017 +0200
@@ -0,0 +1,1201 @@
+/*
+ * Copyright (c) 1999, 2017, Oracle and/or its affiliates. All rights reserved.
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
+ *
+ * This code is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation.
+ *
+ * This code is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
+ * version 2 for more details (a copy is included in the LICENSE file that
+ * accompanied this code).
+ *
+ * You should have received a copy of the GNU General Public License version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
+ * or visit www.oracle.com if you need additional information or have any
+ * questions.
+ *
+ */
+
+#include "precompiled.hpp"
+#include "c1/c1_Canonicalizer.hpp"
+#include "c1/c1_Optimizer.hpp"
+#include "c1/c1_ValueMap.hpp"
+#include "c1/c1_ValueSet.inline.hpp"
+#include "c1/c1_ValueStack.hpp"
+#include "memory/resourceArea.hpp"
+#include "utilities/bitMap.inline.hpp"
+#include "compiler/compileLog.hpp"
+
+typedef GrowableArray<ValueSet*> ValueSetList;
+
+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);
+ }
+
+ CompileLog* log = _hir->compilation()->log();
+ if (log != NULL)
+ log->set_context("optimize name='cee'");
+ }
+
+ ~CE_Eliminator() {
+ CompileLog* log = _hir->compilation()->log();
+ if (log != NULL)
+ log->clear_context(); // skip marker if nothing was printed
+ }
+
+ 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();
+
+ // 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_->state_before();
+ 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);
+ CompileLog* log = _hir->compilation()->log();
+ if (log != NULL)
+ log->set_context("optimize name='eliminate_blocks'");
+ }
+
+ ~BlockMerger() {
+ CompileLog* log = _hir->compilation()->log();
+ if (log != NULL)
+ log->clear_context(); // skip marker if nothing was printed
+ }
+
+ 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();
+ Instruction* next = sux->next();
+ assert(prev->as_BlockEnd() == NULL, "must not be a BlockEnd");
+ prev->set_next(next);
+ prev->fixup_block_pointers();
+ 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_TypeCast (TypeCast* 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_UnsafeGetAndSetObject(UnsafeGetAndSetObject* x);
+ void do_ProfileCall (ProfileCall* x);
+ void do_ProfileReturnType (ProfileReturnType* x);
+ void do_ProfileInvoke (ProfileInvoke* x);
+ void do_RuntimeCall (RuntimeCall* x);
+ void do_MemBar (MemBar* x);
+ void do_RangeCheckPredicate(RangeCheckPredicate* x);
+#ifdef ASSERT
+ void do_Assert (Assert* x);
+#endif
+};
+
+
+// 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.at(block->block_id()); }
+ void set_state_for (BlockBegin* block, ValueSet* stack) { _block_states.at_put(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(), BlockBegin::number_of_blocks(), NULL)
+ , _work_list(new BlockList()) {
+ _visitable_instructions = new ValueSet();
+ _visitor.set_eliminator(this);
+ CompileLog* log = _opt->ir()->compilation()->log();
+ if (log != NULL)
+ log->set_context("optimize name='null_check_elimination'");
+ }
+
+ ~NullCheckEliminator() {
+ CompileLog* log = _opt->ir()->compilation()->log();
+ if (log != NULL)
+ log->clear_context(); // skip marker if nothing was printed
+ }
+
+ 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);
+ void handle_ProfileCall (ProfileCall* x);
+ void handle_ProfileReturnType (ProfileReturnType* 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_TypeCast (TypeCast* 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_UnsafeGetAndSetObject(UnsafeGetAndSetObject* x) {}
+void NullCheckVisitor::do_ProfileCall (ProfileCall* x) { nce()->clear_last_explicit_null_check();
+ nce()->handle_ProfileCall(x); }
+void NullCheckVisitor::do_ProfileReturnType (ProfileReturnType* x) { nce()->handle_ProfileReturnType(x); }
+void NullCheckVisitor::do_ProfileInvoke (ProfileInvoke* x) {}
+void NullCheckVisitor::do_RuntimeCall (RuntimeCall* x) {}
+void NullCheckVisitor::do_MemBar (MemBar* x) {}
+void NullCheckVisitor::do_RangeCheckPredicate(RangeCheckPredicate* x) {}
+#ifdef ASSERT
+void NullCheckVisitor::do_Assert (Assert* x) {}
+#endif
+
+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 NullCheckEliminator::handle_ProfileCall(ProfileCall* x) {
+ for (int i = 0; i < x->nb_profiled_args(); i++) {
+ x->set_arg_needs_null_check(i, !set_contains(x->profiled_arg_at(i)));
+ }
+}
+
+void NullCheckEliminator::handle_ProfileReturnType(ProfileReturnType* x) {
+ x->set_needs_null_check(!set_contains(x->ret()));
+}
+
+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, nblocks, false);
+
+ blocks.push(ir()->start());
+ visited_block.at_put(ir()->start()->block_id(), true);
+ for (int i = 0; i < blocks.length(); i++) {
+ BlockBegin* b = blocks.at(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.at(id)) {
+ blocks.push(excp);
+ visited_block.at_put(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.at(id)) {
+ blocks.push(next);
+ visited_block.at_put(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());
+ }
+}