[lworld] Integrated: 8285763: Implement new approach to dump inlined objects

[Alex Menkov]

On Wed, 27 Apr 2022 22:15:18 GMT, Alex Menkov <amenkov at openjdk.org> wrote:

> Implements new way to dump inlined objects.
> 
> Hprof file format changes:
> -- dump inlined fields in the holder object by introducing synthetic fields to hold the primitive fields of the inlined type.
>     HPROF_GC_CLASS_DUMP records describe the synthetic fields.
>     HPROF_GC_INSTANCE_DUMP records dump inlined object as fields of the holder object.
>     Example:
>         primitive class P1 {
>             byte b1;
>         }
>         primitive class P2 {
>             P1 p1;
>             int i1;
>         }
>         class Holder {
>             P1 p1;
>             P2 p2;
>         }
> 
>     HPROF_GC_CLASS_DUMP record for Holder class does not contain descriptions for p1 and p2 fields, but instead has:
>         p1.b1: byte;
>         p2.p1.b1: byte;
>         p2.i1: int;
> 
> -- new record type is added to describe class with inlined fields:
>     HPROF_INLINED_FIELDS
>     The record contains HPROF_CLASS_WITH_INLINED_FIELDS subrecords with the following format:
>         id         - class ID (dumped as HPROF_GC_CLASS_DUMP)
>         u2        - number of instance inlined fields (not including super)
> 
>     in the example above 2 (p1.b1, p2.p1.b1, p2.i1)
> 
>         [u2       - inlined field index (zero-based)
>          u2       - synthetic field count
>          id        - original field name (dumped as HPROF_UTF8)
>          id]*      - inlined field class ID (dumped by HPROF_GC_CLASS_DUMP)
> 
>     in the example above there are 2 elements:
>         [0, 1, "p1", P1 HPROF_GC_CLASS_DUMP record]
>         [1, 2, "p2", P2 HPROF_GC_CLASS_DUMP record]
> 
>     This records allows new hprof parser tools to restore original fields of the object;
>     Old tools will see synthetic fields which makes possible manual research of the dump.
> 
> -- flat arrays are dumped as HPROF_GC_PRIM_ARRAY_DUMP subrecords (may be byte/short/int array)
> 
> -- new record type is added to describe flat arrays:
>     HPROF_FLAT_ARRAYS
>     The record contains array of HPROF_FLAT_ARRAY subrecords:
>         id     - array object ID (dumped as HPROF_GC_PRIM_ARRAY_DUMP)
>         id     - element class ID (dumped by HPROF_GC_CLASS_DUMP)
> 
>     This records allows new hprof parsers to restore original type of the flat arrays;
>     Unfortunately old parsers can't extract much information from the array dump.

This pull request has now been integrated.

Changeset: 04181f90
Author:    Alex Menkov <amenkov at openjdk.org>
URL:       https://git.openjdk.java.net/valhalla/commit/04181f90aec4b5ffb738944e22bb6b78203b1567
Stats:     1228 lines in 9 files changed: 882 ins; 156 del; 190 mod

8285763: Implement new approach to dump inlined objects

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

PR: https://git.openjdk.java.net/valhalla/pull/686