8233820: Test crashed with assert(phi->operand_count() != 1 || phi->subst() != phi) failed: missed trivial simplification
Summary: Verification code needs to skip illegal phi functions.
Reviewed-by: thartmann, vlivanov
/*
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* 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
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*
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* 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).
*
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* 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
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#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) : _hir(hir), _cee_count(0), _ifop_count(0) {
_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; );
// Only replace safepoint gotos if state_before information is available (if is a safepoint)
bool is_safepoint = if_->is_safepoint();
if (!is_safepoint && (t_goto->is_safepoint() || f_goto->is_safepoint())) {
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, 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) {
Phi* sux_phi = sux_value->as_Phi();
if (sux_phi != NULL && sux_phi->is_illegal()) continue;
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)
, _work_list(new BlockList())
, _set(new ValueSet())
, _block_states(BlockBegin::number_of_blocks(), BlockBegin::number_of_blocks(), NULL)
, _last_explicit_null_check(NULL) {
_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 (is_reference_type(field_type)) {
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());
}
}