//------------------------------array_store_check------------------------------
// pull array from stack and check that the store is valid
void Parse::array_store_check() {
// Shorthand access to array store elements without popping them.
Node *obj = peek(0);
Node *idx = peek(1);
Node *ary = peek(2);
if (_gvn.type(obj) == TypePtr::NULL_PTR) {
// There's never a type check on null values.
// This cutout lets us avoid the uncommon_trap(Reason_array_check)
// below, which turns into a performance liability if the
// gen_checkcast folds up completely.
return;
}
// Extract the array klass type
int klass_offset = oopDesc::klass_offset_in_bytes();
Node* p = basic_plus_adr( ary, ary, klass_offset );
// p's type is array-of-OOPS plus klass_offset
Node* array_klass = _gvn.transform( LoadKlassNode::make(_gvn, immutable_memory(), p, TypeInstPtr::KLASS) );
// Get the array klass
const TypeKlassPtr *tak = _gvn.type(array_klass)->is_klassptr();
// array_klass's type is generally INexact array-of-oop. Heroically
// cast the array klass to EXACT array and uncommon-trap if the cast
// fails.
bool always_see_exact_class = false;
if (MonomorphicArrayCheck
&& !too_many_traps(Deoptimization::Reason_array_check)) {
always_see_exact_class = true;
// (If no MDO at all, hope for the best, until a trap actually occurs.)
}
// Is the array klass is exactly its defined type?
if (always_see_exact_class && !tak->klass_is_exact()) {
// Make a constant out of the inexact array klass
const TypeKlassPtr *extak = tak->cast_to_exactness(true)->is_klassptr();
Node* con = makecon(extak);
Node* cmp = _gvn.transform(new (C) CmpPNode( array_klass, con ));
Node* bol = _gvn.transform(new (C) BoolNode( cmp, BoolTest::eq ));
Node* ctrl= control();
{ BuildCutout unless(this, bol, PROB_MAX);
uncommon_trap(Deoptimization::Reason_array_check,
Deoptimization::Action_maybe_recompile,
tak->klass());
}
if (stopped()) { // MUST uncommon-trap?
set_control(ctrl); // Then Don't Do It, just fall into the normal checking
} else { // Cast array klass to exactness:
// Use the exact constant value we know it is.
replace_in_map(array_klass,con);
CompileLog* log = C->log();
if (log != NULL) {
log->elem("cast_up reason='monomorphic_array' from='%d' to='(exact)'",
log->identify(tak->klass()));
}
array_klass = con; // Use cast value moving forward
}
}
// Come here for polymorphic array klasses
// Extract the array element class
int element_klass_offset = in_bytes(ObjArrayKlass::element_klass_offset());
Node *p2 = basic_plus_adr(array_klass, array_klass, element_klass_offset);
Node *a_e_klass = _gvn.transform( LoadKlassNode::make(_gvn, immutable_memory(), p2, tak) );
// Check (the hard way) and throw if not a subklass.
// Result is ignored, we just need the CFG effects.
gen_checkcast( obj, a_e_klass );
}
//------------------------------array_store_check------------------------------
// pull array from stack and check that the store is valid
void Parse::array_store_check() {
// Shorthand access to array store elements without popping them.
Node *obj = peek(0);
Node *idx = peek(1);
Node *ary = peek(2);
if (_gvn.type(obj) == TypePtr::NULL_PTR) {
// There's never a type check on null values.
// This cutout lets us avoid the uncommon_trap(Reason_array_check)
// below, which turns into a performance liability if the
// gen_checkcast folds up completely.
return;
}
// Extract the array klass type
int klass_offset = oopDesc::klass_offset_in_bytes();
Node* p = basic_plus_adr( ary, ary, klass_offset );
// p's type is array-of-OOPS plus klass_offset
Node* array_klass = _gvn.transform(LoadKlassNode::make(_gvn, NULL, immutable_memory(), p, TypeInstPtr::KLASS));
// Get the array klass
const TypeKlassPtr *tak = _gvn.type(array_klass)->is_klassptr();
// The type of array_klass is usually INexact array-of-oop. Heroically
// cast array_klass to EXACT array and uncommon-trap if the cast fails.
// Make constant out of the inexact array klass, but use it only if the cast
// succeeds.
bool always_see_exact_class = false;
if (MonomorphicArrayCheck
&& !too_many_traps(Deoptimization::Reason_array_check)
&& !tak->klass_is_exact()
&& tak != TypeKlassPtr::OBJECT) {
// Regarding the fourth condition in the if-statement from above:
//
// If the compiler has determined that the type of array 'ary' (represented
// by 'array_klass') is java/lang/Object, the compiler must not assume that
// the array 'ary' is monomorphic.
//
// If 'ary' were of type java/lang/Object, this arraystore would have to fail,
// because it is not possible to perform a arraystore into an object that is not
// a "proper" array.
//
// Therefore, let's obtain at runtime the type of 'ary' and check if we can still
// successfully perform the store.
//
// The implementation reasons for the condition are the following:
//
// java/lang/Object is the superclass of all arrays, but it is represented by the VM
// as an InstanceKlass. The checks generated by gen_checkcast() (see below) expect
// 'array_klass' to be ObjArrayKlass, which can result in invalid memory accesses.
//
// See issue JDK-8057622 for details.
always_see_exact_class = true;
// (If no MDO at all, hope for the best, until a trap actually occurs.)
// Make a constant out of the inexact array klass
const TypeKlassPtr *extak = tak->cast_to_exactness(true)->is_klassptr();
Node* con = makecon(extak);
Node* cmp = _gvn.transform(new CmpPNode( array_klass, con ));
Node* bol = _gvn.transform(new BoolNode( cmp, BoolTest::eq ));
Node* ctrl= control();
{ BuildCutout unless(this, bol, PROB_MAX);
uncommon_trap(Deoptimization::Reason_array_check,
Deoptimization::Action_maybe_recompile,
tak->klass());
}
if (stopped()) { // MUST uncommon-trap?
set_control(ctrl); // Then Don't Do It, just fall into the normal checking
} else { // Cast array klass to exactness:
// Use the exact constant value we know it is.
replace_in_map(array_klass,con);
CompileLog* log = C->log();
if (log != NULL) {
log->elem("cast_up reason='monomorphic_array' from='%d' to='(exact)'",
log->identify(tak->klass()));
}
array_klass = con; // Use cast value moving forward
}
}
// Come here for polymorphic array klasses
// Extract the array element class
int element_klass_offset = in_bytes(ObjArrayKlass::element_klass_offset());
Node *p2 = basic_plus_adr(array_klass, array_klass, element_klass_offset);
// We are allowed to use the constant type only if cast succeeded. If always_see_exact_class is true,
// we must set a control edge from the IfTrue node created by the uncommon_trap above to the
// LoadKlassNode.
Node* a_e_klass = _gvn.transform(LoadKlassNode::make(_gvn, always_see_exact_class ? control() : NULL,
immutable_memory(), p2, tak));
// Check (the hard way) and throw if not a subklass.
// Result is ignored, we just need the CFG effects.
gen_checkcast(obj, a_e_klass);
}
