RFR: 8341586: RISC-V: build fail with gcc9

[Kim Barrett]

On Sun, 6 Oct 2024 13:28:30 GMT, SendaoYan <syan at openjdk.org> wrote:

> Hi all,
> The `src/hotspot/cpu/riscv/icache_riscv.cpp` build fails `riscv_flush_icache.cpp:51:29: error: requested alignment 64 is larger than 16 [-Werror=attributes]` with gcc9. Alignment 16 will be enough.
> 
> Addiontional testing:
> 
> - [x] riscv native build with release conf and slowdebug conf
> - [ ] jtreg tier1 tests with release build

Not a review, just a drive-by comment.

It's unclear from the report whether the issue is with gcc9, or with gcc9+.
Note that gcc10 is the minimum supported version since JDK 23.  So maybe this
isn't really an issue for JDK 23+.

(I'm surprised configuring JDK 24 with gcc9 works, rather than failing with a
complaint about not meeting the minimum required compiler version.)

https://github.com/openjdk/jdk/blame/50426b3841240c5fda0df11439e52fa1ae9e7e07/make/autoconf/toolchain.m4#L53

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PR Comment: https://git.openjdk.org/jdk/pull/21376#issuecomment-2395463696