8303951: Add asserts before record_method_not_compilable where possible #13038

eme64 · 2023-03-15T10:29:32Z

I went through all C2 bailouts, and checked if they are justified to bail out of compilation silently. I added asserts everywhere. Those that were hit, I inspected by hand.

Some of them seem to be justified. There I added comments why they are justified. They are cases that we do not want to handle in C2, and that are rare enough so that it probably does not matter.

For the following bailouts I did not add an assert, because it may have revealed a bug:
JDK-8304328 C2 Bailout "failed spill-split-recycle sanity check" reveals hidden issue with RA

Note:
JDK-8303466 C2: COMPILE SKIPPED: malformed control flow - only one IfProj
That bug bug was the reason for this RFE here. I added the assert for "malformed control flow". After this RFE here, that Bug will run into the assert on debug builds.

I ran tier1-6 and stress testing. Now running tier7-9.

Filed a follow-up RFE to do the same for BAILOUT in C1: JDK-8304532.

Note: the philosophy here is rather to have an assert too much that triggers in the future. Then we can re-evaluate and weaken or remove it - or maybe we find a bug that we can fix.

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Issue

JDK-8303951: Add asserts before record_method_not_compilable where possible

Reviewers

Vladimir Kozlov (@vnkozlov - Reviewer) ⚠️ Review applies to 28d41ffe
Tobias Hartmann (@TobiHartmann - Reviewer)

Reviewing

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Checkout this PR locally:
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$ git checkout pull/13038

Update a local copy of the PR:
$ git checkout pull/13038
$ git pull https://git.openjdk.org/jdk.git pull/13038/head

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Checkout this PR locally:
$ git pr checkout 13038

View PR using the GUI difftool:
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https://git.openjdk.org/jdk/pull/13038.diff

bridgekeeper · 2023-03-15T10:31:09Z

👋 Welcome back epeter! 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 · 2023-03-15T10:32:05Z

@eme64 this pull request can not be integrated into master due to one or more merge conflicts. To resolve these merge conflicts and update this pull request you can run the following commands in the local repository for your personal fork:

git checkout JDK-8303951
git fetch https://git.openjdk.org/jdk master
git merge FETCH_HEAD
# resolve conflicts and follow the instructions given by git merge
git commit -m "Merge master"
git push

openjdk · 2023-03-15T10:32:55Z

@eme64 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.

mlbridge · 2023-03-17T08:38:19Z

Webrevs

vnkozlov

General suggestion is to print more info on bailouts to help debugging.

vnkozlov · 2023-03-17T15:52:53Z

src/hotspot/share/compiler/compileBroker.cpp

@@ -2277,7 +2277,7 @@ void CompileBroker::invoke_compiler_on_method(CompileTask* task) {
    DirectivesStack::release(directive);

    if (!ci_env.failing() && !task->is_success()) {
-      //assert(false, "compiler should always document failure");
+      assert(false, "compiler should always document failure");


I suggest to add ci_env.failure_reason() to assert message.

vnkozlov · 2023-03-17T15:53:42Z

src/hotspot/share/opto/buildOopMap.cpp

@@ -251,6 +251,7 @@ OopMap *OopFlow::build_oop_map( Node *n, int max_reg, PhaseRegAlloc *regalloc, i

      // Check for a legal reg name in the oopMap and bailout if it is not.
      if (!omap->legal_vm_reg_name(r)) {
+        assert(false, "illegal oopMap register name");


Added information about r to assert message.

vnkozlov · 2023-03-17T15:53:52Z

src/hotspot/share/opto/buildOopMap.cpp

@@ -318,6 +319,7 @@ OopMap *OopFlow::build_oop_map( Node *n, int max_reg, PhaseRegAlloc *regalloc, i
      assert( !OptoReg::is_valid(_callees[reg]), "oop can't be callee save" );
      // Check for a legal reg name in the oopMap and bailout if it is not.
      if (!omap->legal_vm_reg_name(r)) {
+        assert(false, "illegal oopMap register name");


vnkozlov · 2023-03-17T15:55:02Z

src/hotspot/share/opto/compile.cpp

@@ -753,7 +753,11 @@ Compile::Compile( ciEnv* ci_env, ciMethod* target, int osr_bci,
    }
    if (failing())  return;
    if (cg == nullptr) {
-      record_method_not_compilable("cannot parse method");
+      const char* reason = InlineTree::check_can_parse(method());
+      assert(reason != nullptr, "cannot parse method: why?");


Add reason to assert's message.

reason is nullptr when the asser fails. I now say expect reason for parse failure.

vnkozlov · 2023-03-17T15:55:12Z

src/hotspot/share/opto/compile.cpp

@@ -762,7 +766,10 @@ Compile::Compile( ciEnv* ci_env, ciMethod* target, int osr_bci,
    JVMState* jvms = build_start_state(start(), tf());
    if ((jvms = cg->generate(jvms)) == nullptr) {
      if (!failure_reason_is(C2Compiler::retry_class_loading_during_parsing())) {
-        record_method_not_compilable("method parse failed");
+        assert(failure_reason() != nullptr, "method parse failed: why?");


vnkozlov · 2023-03-17T15:55:49Z

src/hotspot/share/opto/compile.cpp

@@ -3989,6 +3998,7 @@ bool Compile::final_graph_reshaping() {
      }
      // Recheck with a better notion of 'required_outcnt'
      if (n->outcnt() != required_outcnt) {
+        assert(false, "malformed control flow");


Print more info about n

vnkozlov · 2023-03-17T15:56:41Z

src/hotspot/share/opto/compile.cpp

@@ -4007,6 +4017,7 @@ bool Compile::final_graph_reshaping() {
    // must be infinite loops.
    for (DUIterator_Fast jmax, j = n->fast_outs(jmax); j < jmax; j++)
      if (!frc._visited.test(n->fast_out(j)->_idx)) {
+        assert(false, "infinite loop");


Print more info about n

vnkozlov · 2023-03-17T15:59:45Z

src/hotspot/share/opto/output.cpp

@@ -2844,6 +2844,7 @@ void Scheduling::anti_do_def( Block *b, Node *def, OptoReg::Name def_reg, int is
      pinch = new Node(1); // Pinch point to-be
    }
    if (pinch->_idx >= _regalloc->node_regs_max_index()) {
+      assert(false, "too many D-U pinch points");


More info about pinch node.

vnkozlov · 2023-03-17T16:06:47Z

Should we file a follow-up RFE to do the same for BAILOUT in C1?

Yes

vnkozlov

Looks good.

openjdk · 2023-03-20T16:38:16Z

@eme64 This change now passes all automated pre-integration checks.

ℹ️ This project also has non-automated pre-integration requirements. Please see the file CONTRIBUTING.md for details.

After integration, the commit message for the final commit will be:

8303951: Add asserts before record_method_not_compilable where possible

Reviewed-by: kvn, thartmann

You can use pull request commands such as /summary, /contributor and /issue to adjust it as needed.

At the time when this comment was updated there had been 62 new commits pushed to the master branch:

c433862: 6245410: javax.swing.text.html.CSS.Attribute: BACKGROUND_POSITION is not w3c spec compliant
91f407d: 8029301: Confusing error message for array creation method reference
e73411a: 8304376: Rename t1/t2 classes in com/sun/jdi/CLETest.java to avoid class duplication error in IDE
a2d8f63: 8288730: Add type parameter to Lookup::accessClass and Lookup::ensureInitialized
3777455: 8302191: Performance degradation for float/double modulo on Linux
760c012: 8304683: Memory leak in WB_IsMethodCompatible
75168ea: 8304134: jib bootstrapper fails to quote filename when checking download filetype
4154a98: 8301498: Replace NULL with nullptr in cpu/x86
ddf1e34: 8304089: Convert TraceDependencies to UL
358c61b: 8294972: Convert jdk.jlink internal plugins to use the Classfile API
... and 52 more: https://git.openjdk.org/jdk/compare/ebac7eec8e5923c66a80cbd66e79c354f30a07a3...master

As there are no conflicts, your changes will automatically be rebased on top of these commits when integrating. If you prefer to avoid this automatic rebasing, please check the documentation for the /integrate command for further details.

➡️ To integrate this PR with the above commit message to the master branch, type /integrate in a new comment.

TobiHartmann

Looks good overall, some comments below.

src/hotspot/share/opto/matcher.cpp

src/hotspot/share/opto/parse1.cpp

TobiHartmann · 2023-03-21T07:54:23Z

src/hotspot/share/opto/parse1.cpp

    C->record_method_not_compilable("OSR starts with non-empty stack");
    return;
  }
  // Do not OSR inside finally clauses:
  if (osr_block->has_trap_at(osr_block->start())) {
+    assert(false, "OSR starts with an immediate trap");
+    // Bailout. But we should probably kick into normal compilation?


"OSR inside finally clauses" sounds like it could easily happen.

It sounds likely, but I never saw it happen, up to tier9. So I suggest we leave the assert in, and once it is triggered, we can decide to remove it again. But then we also have an example, and we can check it in as a test, to justify the bailout.

TobiHartmann · 2023-03-21T07:59:46Z

src/hotspot/share/opto/parse1.cpp

@@ -208,11 +208,14 @@ void Parse::load_interpreter_state(Node* osr_buf) {
  // Check bailouts.  We currently do not perform on stack replacement
  // of loops in catch blocks or loops which branch with a non-empty stack.
  if (sp() != 0) {
+    // Bailout. But we should probably kick into normal compilation?


We shouldn't add a question which is equivalent to a ToDo (same below). The comment should explain how this could happen and if we think that making the method not compilable is too strong, we should file a follow-up issue to investigate/fix.

How common is this? We will still compile at C1, so normal compilation will kick in, right?

Ok, I will remove he question. I think you are right, we should at least still have C1 compilation. In my experiments, it was extremely rare, this case.

Co-authored-by: Tobias Hartmann <tobias.hartmann@oracle.com>

TobiHartmann

Thanks for making these changes, looks good to me.

eme64 · 2023-03-23T07:42:45Z

@vnkozlov @TobiHartmann thanks for the help and reviews!
/integrate

openjdk · 2023-03-23T07:44:26Z

Going to push as commit af4d560.
Since your change was applied there have been 62 commits pushed to the master branch:

c433862: 6245410: javax.swing.text.html.CSS.Attribute: BACKGROUND_POSITION is not w3c spec compliant
91f407d: 8029301: Confusing error message for array creation method reference
e73411a: 8304376: Rename t1/t2 classes in com/sun/jdi/CLETest.java to avoid class duplication error in IDE
a2d8f63: 8288730: Add type parameter to Lookup::accessClass and Lookup::ensureInitialized
3777455: 8302191: Performance degradation for float/double modulo on Linux
760c012: 8304683: Memory leak in WB_IsMethodCompatible
75168ea: 8304134: jib bootstrapper fails to quote filename when checking download filetype
4154a98: 8301498: Replace NULL with nullptr in cpu/x86
ddf1e34: 8304089: Convert TraceDependencies to UL
358c61b: 8294972: Convert jdk.jlink internal plugins to use the Classfile API
... and 52 more: https://git.openjdk.org/jdk/compare/ebac7eec8e5923c66a80cbd66e79c354f30a07a3...master

Your commit was automatically rebased without conflicts.

openjdk · 2023-03-23T07:44:44Z

@eme64 Pushed as commit af4d560.

💡 You may see a message that your pull request was closed with unmerged commits. This can be safely ignored.

8303951: Add asserts before record_method_not_compilable where possible

18a6071

openjdk bot added the merge-conflict Pull request has merge conflict with target branch label Mar 15, 2023

openjdk bot added the hotspot-compiler hotspot-compiler-dev@openjdk.org label Mar 15, 2023

manual merge after NULL nullptr

2cac926

openjdk bot removed the merge-conflict Pull request has merge conflict with target branch label Mar 15, 2023

eme64 added 3 commits March 16, 2023 10:07

moving spill-split-recycle bailout to future work

a998ce3

Out of stack space - expected bailout

1908f69

Merge branch 'master' into JDK-8303951

07b00ff

eme64 marked this pull request as ready for review March 17, 2023 08:30

openjdk bot added the rfr Pull request is ready for review label Mar 17, 2023

vnkozlov reviewed Mar 17, 2023

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addressing Vladimir K's review suggestions

28d41ff

vnkozlov approved these changes Mar 20, 2023

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TobiHartmann reviewed Mar 21, 2023

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eme64 and others added 2 commits March 22, 2023 13:52

Apply suggestions from code review

6e60f02

Co-authored-by: Tobias Hartmann <tobias.hartmann@oracle.com>

remove some of my bad comments

9a40a1a

eme64 requested a review from TobiHartmann March 22, 2023 13:11

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8303951: Add asserts before record_method_not_compilable where possible #13038

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8303951: Add asserts before record_method_not_compilable where possible #13038

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