RFR: 8254719: ZGC: Clean up includes

[Stefan Karlsson]

On Tue, 13 Oct 2020 22:18:52 GMT, Per Liden <pliden at openjdk.org> wrote:

> I noticed quite a few includes in ZGC that are no longer needed and can be cleaned out. As a side-effect I noticed that
> `stackWatermark.hpp` and `threadSMR.hpp` weren't self contained, so I had to fix that too.
> Builds on all Oracle platforms.

I think there are too many removal of includes that shouldn't be removed, IMHO. Could you take another pass and check
all the files? I commented on some of the files, but didn't look at them all.

src/hotspot/share/gc/z/zHeap.hpp line 41:

> 39: #include "gc/z/zWorkers.hpp"
> 40:
> 41: class Page;

Did you mean ZPage?

src/hotspot/share/gc/z/zMark.hpp line 31:

> 29: #include "gc/z/zMarkTerminate.hpp"
> 30: #include "oops/oopsHierarchy.hpp"
> 31: #include "utilities/globalDefinitions.hpp"

This file uses definitions brought by globalDefinitions.hpp, so I don't see the reason for removing it.

src/hotspot/share/gc/z/zRelocate.cpp line 30:

> 28: #include "gc/z/zHeap.hpp"
> 29: #include "gc/z/zOopClosures.inline.hpp"
> 30: #include "gc/z/zPage.hpp"

This file calls `forwarding->page()->object_iterate(&cl);` so it *should* be including zPage.inline.hpp

src/hotspot/share/gc/z/zRelocate.hpp line 27:

> 25: #define SHARE_GC_Z_ZRELOCATE_HPP
> 26:
> 27: #include "gc/z/zWorkers.hpp"

This could also be forward declared, right?

src/hotspot/share/gc/z/zRelocationSet.cpp line 27:

> 25: #include "gc/z/zForwarding.hpp"
> 26: #include "gc/z/zRelocationSet.hpp"
> 27: #include "memory/allocation.hpp"

Uses REALLOC_C_HEAP_ARRAY, so probably should keep allocation.hpp

src/hotspot/share/gc/z/zRelocationSetSelector.cpp line 33:

> 31: #include "runtime/globals.hpp"
> 32: #include "utilities/debug.hpp"
> 33: #include "utilities/powerOfTwo.hpp"

Uses exact_log2, so shouldn't be removed.

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Changes requested by stefank (Reviewer).

PR: https://git.openjdk.java.net/jdk/pull/644