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8134758: Final String field values should be trusted as stable

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Reviewed-by: kvn, thartmann
This commit is contained in:
Aleksey Shipilev 2015-09-01 19:48:10 +03:00
parent 3b19bff980
commit 7c7692856a
1 changed files with 10 additions and 8 deletions
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18
hotspot/src/share/vm/opto/memnode.cpp
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@ -1677,6 +1677,9 @@ const Type *LoadNode::Value( PhaseTransform *phase ) const {
if (klass == env->String_klass() &&
adr->is_AddP() && off != Type::OffsetBot) {
// For constant Strings treat the final fields as compile time constants.
// While we can list what field types java.lang.String has, it is more
// future-proof to handle all possible field types, anticipating future
// changes and experiments in String code.
Node* base = adr->in(AddPNode::Base);
const TypeOopPtr* t = phase->type(base)->isa_oopptr();
if (t != NULL && t->singleton()) {
@ -1684,14 +1687,13 @@ const Type *LoadNode::Value( PhaseTransform *phase ) const {
if (field != NULL && field->is_final()) {
ciObject* string = t->const_oop();
ciConstant constant = string->as_instance()->field_value(field);
if (constant.basic_type() == T_INT) {
return TypeInt::make(constant.as_int());
} else if (constant.basic_type() == T_ARRAY) {
if (adr->bottom_type()->is_ptr_to_narrowoop()) {
return TypeNarrowOop::make_from_constant(constant.as_object(), true);
} else {
return TypeOopPtr::make_from_constant(constant.as_object(), true);
}
// Type::make_from_constant does not handle narrow oops, so handle it here.
// Everything else can use the factory method.
if ((constant.basic_type() == T_ARRAY || constant.basic_type() == T_OBJECT)
&& adr->bottom_type()->is_ptr_to_narrowoop()) {
return TypeNarrowOop::make_from_constant(constant.as_object(), true);
} else {
return Type::make_from_constant(constant, true);
}
}
}