RFR: 8308869: C2: use profile data in subtype checks when profile has more than one class [v14]

[Roland Westrelin]

> In this simple micro benchmark:
> 
> https://github.com/franz1981/java-puzzles/blob/main/src/main/java/red/hat/puzzles/polymorphism/RequireNonNullCheckcastScalability.java#L70
> 
> Performance drops sharply with polluted profile:
> 
> 
> Benchmark                                         (typePollution)   Mode  Cnt     Score    Error   Units
> RequireNonNullCheckcastScalability.isDuplicated1            false  thrpt   10  1453.372 ± 24.919  ops/us
> 
> 
> to:
> 
> 
> Benchmark                                         (typePollution)   Mode  Cnt   Score   Error   Units
> RequireNonNullCheckcastScalability.isDuplicated1             true  thrpt   10  28.579 ± 2.280  ops/us
> 
> 
> The test has 2 type checks to 2 different interfaces so caching with
> `secondary_super_cache` doesn't help.
> 
> The micro-benchmark only uses 2 different concrete classes
> (`DuplicatedContext` and `NonDuplicatedContext`) and they are recorded
> in profile data at the type checks. But c2 only take advantage of
> profile data at type checks if they report a single class.
> 
> What I propose is that the full blown type check expanded in
> `Phase::gen_subtype_check()` takes advantage of profile data. So in
> the case of the micro benchmark, before checking the
> `secondary_super_cache`, generated code checks whether the object
> being type checked is a `DuplicatedContext` or a
> `NonDuplicatedContext`.
> 
> This works fairly well on this micro benchmark:
> 
> 
> Benchmark                                         (typePollution)   Mode  Cnt    Score    Error   Units
> RequireNonNullCheckcastScalability.isDuplicated1             true  thrpt   10  871.224 ± 20.750  ops/us
> 
> 
> It also scales much better if there are multiple threads running the
> same test (`secondary_super_cache` doesn't scale well: see
> JDK-8180450).
> 
> Now if the micro-benchmark is changed according to the comment:
> 
> https://github.com/franz1981/java-puzzles/blob/d2d60af3d0dfe7a2567807395138edcb1d1c24f5/src/main/java/red/hat/puzzles/polymorphism/RequireNonNullCheckcastScalability.java#L62
> 
> so the type check hits in the `secondary_super_cache`, the current
> code performs much better:
> 
> 
> Benchmark                                         (typePollution)   Mode  Cnt    Score    Error   Units
> RequireNonNullCheckcastScalability.isDuplicated1             true  thrpt   10  871.224 ± 20.750  ops/us
> 
> 
> but leveraging profiling as explained above performs even better:
> 
> 
> Benchmark                                         (typePollution)   Mode  Cnt     Score    Error   Units
> RequireNonNullCheckcastScalability.isDuplic...

Roland Westrelin has updated the pull request with a new target base due to a merge or a rebase. The pull request now contains 33 commits:

 - Merge branch 'master' into JDK-8308869
 - Update src/hotspot/share/opto/subtypenode.hpp
   
   Co-authored-by: Tobias Hartmann <tobias.hartmann at oracle.com>
 - review
 - Merge branch 'master' into JDK-8308869
 - Update src/hotspot/cpu/aarch64/c1_LIRAssembler_aarch64.cpp
   
   Co-authored-by: Tobias Hartmann <tobias.hartmann at oracle.com>
 - Update src/hotspot/cpu/aarch64/c1_LIRAssembler_aarch64.cpp
   
   Co-authored-by: Tobias Hartmann <tobias.hartmann at oracle.com>
 - Update src/hotspot/cpu/riscv/c1_LIRAssembler_riscv.cpp
   
   Co-authored-by: Tobias Hartmann <tobias.hartmann at oracle.com>
 - Update src/hotspot/cpu/riscv/c1_LIRAssembler_riscv.cpp
   
   Co-authored-by: Tobias Hartmann <tobias.hartmann at oracle.com>
 - Update src/hotspot/cpu/x86/c1_LIRAssembler_x86.cpp
   
   Co-authored-by: Tobias Hartmann <tobias.hartmann at oracle.com>
 - Update src/hotspot/cpu/x86/c1_LIRAssembler_x86.cpp
   
   Co-authored-by: Tobias Hartmann <tobias.hartmann at oracle.com>
 - ... and 23 more: https://git.openjdk.org/jdk/compare/62a953f4...cba248e4

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

Changes: https://git.openjdk.org/jdk/pull/14375/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=14375&range=13
  Stats: 1170 lines in 36 files changed: 706 ins; 329 del; 135 mod
  Patch: https://git.openjdk.org/jdk/pull/14375.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/14375/head:pull/14375

PR: https://git.openjdk.org/jdk/pull/14375