RFR: 8365579: ml64.exe is not the right assembler for Windows aarch64 [v4]

[Magnus Ihse Bursie]

On Fri, 22 Aug 2025 23:52:10 GMT, Saint Wesonga <duke at openjdk.org> wrote:

>> [ml64](https://learn.microsoft.com/en-us/cpp/assembler/masm/ml-and-ml64-command-line-reference?view=msvc-170) is set as the assembler for the Windows platform but is specific to the x64 platform. The [armasm64](https://learn.microsoft.com/en-us/cpp/assembler/arm/arm-assembler-command-line-reference?view=msvc-170) assembler should be used for Windows AArch64.
>> 
>> The -c and -Ta options are only valid for ml64 and -Ta can be removed from CompileFile.gmk (assembling for x64 works without it).
>
> Saint Wesonga has updated the pull request incrementally with one additional commit since the last revision:
> 
>   Restore -Ta flag for x64 assembler

I'd like to see some more investigation into the removal of `-Ta` before integration, since it is documented as required.

An alternative to investigation is to keep it for ml64, by creating a new variable exposed to spec.gmk, similar to how cl.exe needs a `-out:` (or whatever it was called) for where to .obj files.

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PR Comment: https://git.openjdk.org/jdk/pull/26791#issuecomment-3216572092