RFR: 8302459: Missing late inline cleanup causes compiler/vectorapi/VectorLogicalOpIdentityTest.java IR failure [v4]

[Vladimir Ivanov]

On Fri, 7 Mar 2025 14:24:11 GMT, Damon Fenacci <dfenacci at openjdk.org> wrote:

>> # Issue
>> 
>> The `compiler/vectorapi/VectorLogicalOpIdentityTest.java` has been failing because C2 compiling the test `testAndMaskSameValue1` expects to have 1 `AndV` nodes but it has none.
>> 
>> # Cause
>> 
>> The issue has to do with the criteria that trigger a cleanup when performing late inlining. In the failing test, when the compiler tries to inline a `jdk.internal.vm.vector.VectorSupport::binaryOp` call, it fails because its argument is of the wrong type, mainly because some cast nodes “hide” the more “precise” type. 
>> The graph that leads to the issue looks like this:
>> ![1BCE8148-1E44-4CA1-AF8F-EFC6210FA740](https://github.com/user-attachments/assets/62dd917f-2dac-42a9-90cf-73eedcd3cf8a)
>> The compiler tries to inline `jdk.internal.vm.vector.VectorSupport::load` and it succeeds:
>> ![752E81C9-A37D-4626-81A9-E4A839FADD3D](https://github.com/user-attachments/assets/e61057b2-3093-4992-ba5a-b80e4000c0ec)
>> The node `3027 VectorBox` has type `IntMaxVector`. `912 CastPP` and `934 CheckCastPP` have type `IntVector`instead.
>> The compiler then tries to inline one of the 2 `bynaryOp` calls but it fails because it needs an argument of type `IntMaxVector` and the argument it is given, which is node `934 CheckCastPP` , has type `IntVector`.
>> 
>> This would not happen if between the 2 inlining attempts a _cleanup_ was triggered. IGVN would run and the 2 nodes  `912 CastPP` and `934 CheckCastPP` would be folded away. `binaryOp` could then be inlined since the types would match.
>> 
>> # Solution
>> 
>> Instead of fixing this specific case we try a more generic approach: when late inlining we keep track of failed intrinsics and re-examine them during IGVN. If the `Ideal` method for their call node is called, we reschedule the intrinsic attempt for that call.
>> 
>> # Testing
>> 
>> Additional test runs with `-XX:-TieredCompilation` are added to `VectorLogicalOpIdentityTest.java` and `VectorGatherMaskFoldingTest.java` as regression tests and `-XX:+IncrementalInlineForceCleanup` is removed from `VectorGatherMaskFoldingTest.java` (previously added as workaround for this issue)
>> 
>> Tests: Tier 1-4 (windows-x64, linux-x64/aarch64, and macosx-x64/aarch64; release and debug mode)
>
> Damon Fenacci has updated the pull request incrementally with one additional commit since the last revision:
> 
>   JDK-8302459: create method to prepend and reset generator

src/hotspot/share/opto/callnode.cpp line 1072:

> 1070: #endif
> 1071: 
> 1072: void CallJavaNode::prepend_and_reset_generator(PhaseGVN* phase, CallGenerator* cg) {

`prepend_and_reset_generator` sounds way too verbose. Maybe `register_for_late_inline` instead?

Also, `CallGenertaor* cg` argument is redundant. And `phase` is used just to extract `Compile*`.

Either 

void CallJavaNode::register_for_late_inline(Compile* C) {
  if (generator() != nullptr) {
    C->prepend_late_inline(generator());
    set_generator(nullptr);
  } else {
    assert(false, "repeated attempt");
  }
}


Or even drop `Compile* C` and use `Compile::current()`.

-------------

PR Review Comment: https://git.openjdk.org/jdk/pull/21682#discussion_r1985576552