RFR: 8372040: Remove Prefetch header vs inline header separation

[jonghoonpark]

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.

Thank you for the insightful discussion and feedback.

To summarize the next steps, I will:

1. Explicitly include `prefetch.inline.hpp` in `g1YoungGCPostEvacuateTasks.cpp` to follow the "Include What You Use" principle.

2. Add a comment to each platform-dependent prefetch inline file (e.g., `prefetch_linux_x86.inline.hpp`) stating: `// Included in runtime/prefetch.inline.hpp`

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PR Comment: https://git.openjdk.org/jdk/pull/29096#issuecomment-3728837840