RFR: 8372040: Remove Prefetch header vs inline header separation

[David Holmes]

On Wed, 7 Jan 2026 17:47:47 GMT, jonghoonpark <duke at openjdk.org> wrote:

> related jira issue: https://bugs.openjdk.org/browse/JDK-8372040
> 
> ---
> 
> ## Changes
> 
> - Merged `prefetch.hpp` into `prefetch.inline.hpp` and removed the redundant `prefetch.hpp`. Updated all call sites accordingly.
> - Removed `runtime/prefetch.inline.hpp` from `generation.hpp` to adhere to the rule that standard headers should not include inline headers.
>     - Added the inclusion of `runtime/prefetch.inline.hpp` to `cardTableRS.cpp` instead.
> - Removed `runtime/prefetch.hpp` from `g1YoungGCPostEvacuateTasks.cpp` as it is already included via `g1HeapRegion.inline.hpp`.
> 
> ---
> 
> Verified with tier1 testing; no regressions found.

Given the OS_CPU_HEADER_INLINE files are not intended to be included directly by anything except their shared counterpart, I think it looks very odd to write it as-if we expect it to be included directly. To me the comment, per orderAccess files suffices if this is a concern.

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PR Comment: https://git.openjdk.org/jdk/pull/29096#issuecomment-3725510972