RFR: 8266967: debug.cpp utility find() should print Java Object fields.

[Kevin Walls]

This change enables debug.cpp's find() utility to print Java Objects with their fields.

find() calls os::print_location, and Java heap objects are printed with instanceKlass oop_print_on.
Removing the ifdef for defining oop_print_on for instanceKlass, and also on methods in FieldPrinter and FieldDescriptor, make this work.


Checking other uses of os::print_location this might affect:

macroAssembler_x86.cpp has MacroAssembler::print_state32 and MacroAssembler::print_state64
which use os::print_location to print register contents and print words at top of stack.
These will be more verbose, as it already is in non-PRODUCT builds.

vmError uses os::print_location when showing the stack, i.e. this output:

Stack slot to memory mapping:
stack at sp + 0 slots: 0x0000000000000002 is an unknown value
..etc...

...will be more verbose when Java object references are found (for the 8 stack slots it tries to show).


Shenandoah uses os::print_location once, but for non-Java heap objects so nothing changes.


Manual testing on Linux-x64 and Windows: old behaviour shows these two lines only:

"Executing find"
0x00000000ff0a03e0 is an oop: jdk.internal.loader.ClassLoaders$AppClassLoader
{0x00000000ff0a03e0} - klass: 'jdk/internal/loader/ClassLoaders$AppClassLoader'

...then with the change the full info:

"Executing find"
0x00000000ff0a03e0 is an oop: jdk.internal.loader.ClassLoaders$AppClassLoader
{0x00000000ff0a03e0} - klass: 'jdk/internal/loader/ClassLoaders$AppClassLoader'
 - ---- fields (total size 13 words):
 - private 'defaultAssertionStatus' 'Z' @12  false
 - private final 'parent' 'Ljava/lang/ClassLoader;' @24  a 'jdk/internal/loader/ClassLoaders$PlatformClassLoader'{0x00000000ff0a0a
40} (ff0a0a40)
 - private final 'name' 'Ljava/lang/String;' @28  "app"{0x00000000ff0d0060} (ff0d0060)
 - private final 'unnamedModule' 'Ljava/lang/Module;' @32  a 'java/lang/Module'{0x00000000ff0a0448} (ff0a0448)
...etc...

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

Commit messages:
 - 8266967: debug.cpp utility find() should print Java Object fields.

Changes: https://git.openjdk.java.net/jdk/pull/4011/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=4011&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8266967
  Stats: 20 lines in 4 files changed: 5 ins; 12 del; 3 mod
  Patch: https://git.openjdk.java.net/jdk/pull/4011.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/4011/head:pull/4011

PR: https://git.openjdk.java.net/jdk/pull/4011