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8354383: C2: enable sinking of Type nodes out of loop #25396

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8354383: C2: enable sinking of Type nodes out of loop #25396

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6a87d37
fix
rwestrel Apr 10, 2025
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rwestrel Apr 11, 2025
bebfec3
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rwestrel May 26, 2025
303bb31
Update src/hotspot/share/opto/loopopts.cpp
rwestrel May 26, 2025
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8 changes: 7 additions & 1 deletion src/hotspot/share/opto/loopopts.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -1676,6 +1676,10 @@ bool PhaseIdealLoop::safe_for_if_replacement(const Node* dom) const {
// like various versions of induction variable+offset. Clone the
// computation per usage to allow it to sink out of the loop.
void PhaseIdealLoop::try_sink_out_of_loop(Node* n) {
bool is_raw_to_oop_cast = n->is_ConstraintCast() &&
n->in(1)->bottom_type()->isa_rawptr() &&
!n->bottom_type()->isa_rawptr();

if (has_ctrl(n) &&
!n->is_Phi() &&
!n->is_Bool() &&
Expand All @@ -1685,7 +1689,9 @@ void PhaseIdealLoop::try_sink_out_of_loop(Node* n) {
!n->is_OpaqueNotNull() &&
!n->is_OpaqueInitializedAssertionPredicate() &&
!n->is_OpaqueTemplateAssertionPredicate() &&
!n->is_Type()) {
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I cannot remember exactly, how often was it a problem without JDK-8349479? If it was more common, we might want to only allow it when KillPathsReachableByDeadTypeNode is set.

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I made that change.
As far as I remember, the logic removed by JDK-8319372 played a key role in those failures. Not sure if any were still reproducible after than one.

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Yes, that matches what I remember. Maybe JDK-8319372 can now be reverted with JDK-8349479 in?

!is_raw_to_oop_cast && // don't extend live ranges of raw oops
(KillPathsReachableByDeadTypeNode || !n->is_Type())
) {
Node *n_ctrl = get_ctrl(n);
IdealLoopTree *n_loop = get_loop(n_ctrl);

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