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8348411: C2: Remove the control input of LoadKlassNode and LoadNKlassNode #23274

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8348411: C2: Remove the control input of LoadKlassNode and LoadNKlassNode #23274

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79cf199
remove control input of LoadKlassNode
merykitty Jan 23, 2025
ff924de
remove always_see_exact_class
merykitty Jan 23, 2025
c676188
clearer intention, revert formatting, add assert
merykitty Jan 30, 2025
175232a
format
merykitty Jan 30, 2025
7c2b595
Merge branch 'master' into loadklassctrl
merykitty Feb 6, 2025
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43 changes: 22 additions & 21 deletions src/hotspot/share/opto/parseHelper.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -165,27 +165,27 @@ void Parse::array_store_check() {
// Make constant out of the inexact array klass, but use it only if the cast
// succeeds.
if (MonomorphicArrayCheck && !too_many_traps(Deoptimization::Reason_array_check) && !tak->klass_is_exact()
&& tak != TypeInstKlassPtr::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.
&& tak->isa_aryklassptr()) {
// 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.

// Make a constant out of the exact array klass
const TypeAryKlassPtr* extak = tak->cast_to_exactness(true)->is_aryklassptr();
Expand Down Expand Up @@ -220,6 +220,7 @@ void Parse::array_store_check() {
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));
assert(StressReflectiveCode || array_klass->is_Con() == a_e_klass->is_Con(), "a constant array type must come with a constant element type");

// Check (the hard way) and throw if not a subklass.
// Result is ignored, we just need the CFG effects.
Expand Down