8344035: Replace predicate walking code in Loop Unswitching with a predicate visitor #22828

chhagedorn · 2024-12-19T13:56:41Z

This patch is a follow up to the clean-ups done with JDK-8342945 and introduces a new predicate visitor for Loop Unswitching to update the last remaining custom predicate cloning code.

This patch includes the following:

New CloneUnswitchedLoopPredicatesVisitor class which delegates the cloning work to a new ClonePredicateToTargetLoop class.
- We walk the predicate chain in the PredicateIterator and call the CloneUnswitchedLoopPredicatesVisitor for each visited predicate. Then we clone the predicate on the fly to the target loop.
New ClonePredicateToTargetLoop class:
- Clones Parse Predicates
- Clones Template Assertion Predicates
  - Includes rewiring of control dependent data nodes
- Rewires the cloned predicates to the target loop with new TargetLoopPredicateChain class:
  - Keeps track of the current chain head, which is the target loop itself when the chain is still empty.
  - Each time a new predicate is inserted at the target loop, the old predicate chain head is set as output of the new predicate.
  - An example is shown as class comment at TargetLoopPredicateChain.
  - I plan to reuse this class later again when also updating CreateAssertionPredicatesVisitor which is done when we tackle the actual still remaining Assertion Predicate bugs.
Removal of custom predicate cloning code found in PhaseIdealLoop.
Changed steps performed in Loop Unswitching from:
1. Clone loop
2. Clone predicates and insert them below the unswitched loop selector If projections
3. Connect the cloned predicates to the unswitched loops
to:
1. Clone loop
2. Connect unswitched loop selector If projections to unswitched loops such that they are now the new loop entries
3. Clone predicates and insert them between the unswitched loop selector If projections and the unswitched loops
Rename/update get_template_assertion_predicates()/TemplateAssertionPredicateCollector to reflect the only use left.

Thanks,
Christian

Progress

Change must be properly reviewed (1 review required, with at least 1 Reviewer)
Change must not contain extraneous whitespace
Commit message must refer to an issue

Issue

JDK-8344035: Replace predicate walking code in Loop Unswitching with a predicate visitor (Sub-task - P4)

Reviewing

Using git

Checkout this PR locally:
$ git fetch https://git.openjdk.org/jdk.git pull/22828/head:pull/22828
$ git checkout pull/22828

Update a local copy of the PR:
$ git checkout pull/22828
$ git pull https://git.openjdk.org/jdk.git pull/22828/head

Using Skara CLI tools

Checkout this PR locally:
$ git pr checkout 22828

View PR using the GUI difftool:
$ git pr show -t 22828

Using diff file

Download this PR as a diff file:
https://git.openjdk.org/jdk/pull/22828.diff

Using Webrev

Link to Webrev Comment

…edicate visitor

bridgekeeper · 2024-12-19T13:57:12Z

👋 Welcome back chagedorn! A progress list of the required criteria for merging this PR into master will be added to the body of your pull request. There are additional pull request commands available for use with this pull request.

openjdk · 2024-12-19T13:57:14Z

❗ This change is not yet ready to be integrated.
See the Progress checklist in the description for automated requirements.

openjdk · 2024-12-19T13:57:41Z

@chhagedorn The following label will be automatically applied to this pull request:

hotspot-compiler

When this pull request is ready to be reviewed, an "RFR" email will be sent to the corresponding mailing list. If you would like to change these labels, use the /label pull request command.

chhagedorn · 2024-12-19T13:57:07Z

src/hotspot/share/opto/loopPredicate.cpp

-                                                        const int opcode, const bool rewire_uncommon_proj_phi_inputs,
-                                                        AssertionPredicateType assertion_predicate_type) {
+                                                        const int opcode, const bool rewire_uncommon_proj_phi_inputs) {


Squeezed this in here: assertion_predicate_type is dead.

chhagedorn · 2024-12-19T13:57:27Z

src/hotspot/share/opto/loopPredicate.cpp

+void PhaseIdealLoop::get_opaque_template_assertion_predicate_nodes(ParsePredicateSuccessProj* parse_predicate_proj,
+                                                                   Unique_Node_List& list) {


Only applied a renaming here.

chhagedorn · 2024-12-19T13:57:55Z

src/hotspot/share/opto/loopUnswitch.cpp

+  void unswitch(const UnswitchedLoopSelector& unswitched_loop_selector) {
+    const uint first_false_path_loop_node_index = _phase->C->unique();
+    clone_loop(unswitched_loop_selector);
+
+    move_parse_and_template_assertion_predicates_to_unswitched_loops(unswitched_loop_selector,
+                                                                     first_false_path_loop_node_index);
+    DEBUG_ONLY(verify_unswitched_loop_versions(_loop->_head->as_Loop(), unswitched_loop_selector);)
+
+    _phase->recompute_dom_depth();
+    remove_unswitch_candidate_from_loops(unswitched_loop_selector);


New order of operation (see PR description).

chhagedorn · 2024-12-19T13:58:38Z

src/hotspot/share/opto/loopUnswitch.cpp

+    const UnswitchedLoopSelector& unswitched_loop_selector, const uint first_false_path_loop_node_index) const {
+    const NodeInOriginalLoopBody node_in_true_path_loop_body(first_false_path_loop_node_index, _old_new);
+    const NodeInClonedLoopBody node_in_false_path_loop_body(first_false_path_loop_node_index);
+    CloneUnswitchedLoopPredicatesVisitor
+    clone_unswitched_loop_predicates_visitor(_loop_head, old_to_new(_loop_head)->as_Loop(), node_in_true_path_loop_body,
+                                             node_in_false_path_loop_body, _phase);
+    Node* source_loop_entry = unswitched_loop_selector.selector()->in(0);
+    PredicateIterator predicate_iterator(source_loop_entry);
+    predicate_iterator.for_each(clone_unswitched_loop_predicates_visitor);


The main part that is new here: We use visitors to clone the predicates and rewire them correctly.

chhagedorn · 2024-12-19T13:58:45Z

src/hotspot/share/opto/loopUnswitch.cpp

+  Node* old_to_new(const Node* old) const {
+    return _old_new[old->_idx];
+  }


Only moved.

mlbridge · 2024-12-19T14:04:22Z

Webrevs

00: Full (9cc2db29)

8344035: Replace predicate walking code in Loop Unswitching with a pr…

9cc2db2

…edicate visitor

openjdk bot added the hotspot-compiler [email protected] label Dec 19, 2024

chhagedorn commented Dec 19, 2024

View reviewed changes

chhagedorn marked this pull request as ready for review December 19, 2024 14:00

openjdk bot added the rfr Pull request is ready for review label Dec 19, 2024

Provide feedback

Saved searches

Use saved searches to filter your results more quickly

8344035: Replace predicate walking code in Loop Unswitching with a predicate visitor #22828

8344035: Replace predicate walking code in Loop Unswitching with a predicate visitor #22828

chhagedorn commented Dec 19, 2024 •

edited by openjdk bot

Loading

bridgekeeper bot commented Dec 19, 2024

openjdk bot commented Dec 19, 2024

openjdk bot commented Dec 19, 2024

chhagedorn Dec 19, 2024

chhagedorn Dec 19, 2024

chhagedorn Dec 19, 2024

chhagedorn Dec 19, 2024

chhagedorn Dec 19, 2024

mlbridge bot commented Dec 19, 2024

		void PhaseIdealLoop::get_opaque_template_assertion_predicate_nodes(ParsePredicateSuccessProj* parse_predicate_proj,
		Unique_Node_List& list) {

8344035: Replace predicate walking code in Loop Unswitching with a predicate visitor #22828

Are you sure you want to change the base?

8344035: Replace predicate walking code in Loop Unswitching with a predicate visitor #22828

Conversation

chhagedorn commented Dec 19, 2024 • edited by openjdk bot Loading

Progress

Issue

Reviewing

bridgekeeper bot commented Dec 19, 2024

openjdk bot commented Dec 19, 2024

openjdk bot commented Dec 19, 2024

chhagedorn Dec 19, 2024

Choose a reason for hiding this comment

chhagedorn Dec 19, 2024

Choose a reason for hiding this comment

chhagedorn Dec 19, 2024

Choose a reason for hiding this comment

chhagedorn Dec 19, 2024

Choose a reason for hiding this comment

chhagedorn Dec 19, 2024

Choose a reason for hiding this comment

mlbridge bot commented Dec 19, 2024

Webrevs

chhagedorn commented Dec 19, 2024 •

edited by openjdk bot

Loading