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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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8 changes: 5 additions & 3 deletions src/hotspot/share/opto/parseHelper.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -164,8 +164,10 @@ void Parse::array_store_check() {
// 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.
if (MonomorphicArrayCheck && !too_many_traps(Deoptimization::Reason_array_check) && !tak->klass_is_exact()
&& tak->isa_aryklassptr()) {
if (MonomorphicArrayCheck &&
!too_many_traps(Deoptimization::Reason_array_check) &&
!tak->klass_is_exact() &&
tak->isa_aryklassptr()) {
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Looks like an implicit nullptr check. Not allowed by code style ;)

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Can you quickly explain this change from tak != TypeInstKlassPtr::OBJECT so I don't need to investigate myself, please?

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Looks like an implicit nullptr check. Not allowed by code style ;)

But the verb here is isa and we use these as a bool a lot, though :/

Can you quickly explain this change from tak != TypeInstKlassPtr::OBJECT so I don't need to investigate myself, please?

The bottom type of an array can be either Object or an array of some kind, so tak != TypeInstKlassPtr::OBJECT is the same as tak->isa_aryklassptr().

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Ah great, thanks for the explanation!

// Regarding the fourth condition in the if-statement from above:
//
// If the compiler has determined that the type of array 'ary' (represented
Expand Down Expand Up @@ -220,7 +222,7 @@ 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");
assert(array_klass->is_Con() == a_e_klass->is_Con() || StressReflectiveCode, "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