[vectorIntrinsics+mask] RFR: 8266287: Basic mask IR implementation for the Vector API masking feature support [v2]

[Xiaohong Gong]

On Wed, 12 May 2021 10:50:30 GMT, Jatin Bhateja <jbhateja at openjdk.org> wrote:

>> Xiaohong Gong has updated the pull request with a new target base due to a merge or a rebase. The pull request now contains three commits:
>> 
>>  - Use "Flag_is_predicated_vector" for masked vector nodes
>>  - Merge branch 'vectorIntrinsics+mask'
>>  - 8266287: Basic mask IR implementation for the Vector API masking feature support
>
> src/hotspot/share/opto/vectorIntrinsics.cpp line 84:
> 
>> 82:   assert(check_vbox(vbox_type), "");
>> 83:   const TypeVect* vt = is_vector_mask(vbox_type->klass()) ?
>> 84:                        TypeVect::makemask(elem_bt, num_elem) : TypeVect::make(elem_bt, num_elem);
> 
> Box type which is an envelope type should still be the same e.g. Int256VectorMask. Value contained in the Masked Box should be of type vectmask.

Hi @jatin-bhateja , it seems the type of `VectorBox/VectorUnbox` should be exactly matched with the `value` boxed. For such an optimization `// VectorUnbox (VectorBox v) ==> v`, if the type of `v` is a vector mask type while the `VectorUnbox` type is expected to be a vector type, the final result of this optimization would change the result type of `VectorUnbox` to be a mask type. Some type checks or assertion will fail. I met the following issue when I run the jtreg tests after changing type of `VectorBox/VectorUnbox` back to vector type:

# A fatal error has been detected by the Java Runtime Environment:
#
#  Internal Error (/home/ent-user/panama-vector/src/hotspot/share/opto/type.cpp:2412), pid=433543, tid=433698
#  Error: assert(base() == v->base()) failed
#
# JRE version: OpenJDK Runtime Environment (17.0) (fastdebug build 17-internal+0-git-8123588d66)
# Java VM: OpenJDK 64-Bit Server VM (fastdebug 17-internal+0-git-8123588d66, mixed mode, sharing, compressed oops, compressed class ptrs, g1 gc, linux-aarch64)
# Problematic frame:
# V  [libjvm.so+0x19f3108]  TypeVect::xmeet(Type const*) const+0x138
#
# Core dump will be written. Default location: Core dumps may be processed with "/usr/lib/systemd/systemd-coredump %P %u %g %s %t %c %h %e" (or dumping to /home/ent-user/jtreg/jtreg-hg/build/images/jtreg/jtwork/scratch/2/core.433543)
#
# If you would like to submit a bug report, please visit:
#   https://bugreport.java.com/bugreport/crash.jsp

Do you have any strong reason that we must define a vector type for `VectorBox/VectorUnbox`?

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

PR: https://git.openjdk.java.net/panama-vector/pull/78