RFR: 8320206: Some intrinsics/stubs missing vzeroupper on x86_64

[Vladimir Kozlov]

On Wed, 15 Nov 2023 21:28:46 GMT, Sandhya Viswanathan <sviswanathan at openjdk.org> wrote:

> The following intrinsics/stubs are missing vzeroupper:
> adler32 (since JDK17)
> count_positives (since JDK 9)
> chacha20 (since JDK 20)
> string indexOfChar (since JDK 9)
> 
> Adding the missing vzeroupper to avoid AVX-SSE transition penalties.

I have no question about generating vzeroupper at the end of JITed code because it could be called from Interpreter.
My question only about vzeroupper in intrinsics stubs.  Vivek did not answer my question during [8178811 RFR](https://mail.openjdk.org/pipermail/hotspot-compiler-dev/2017-April/026134.html) you pointed.
He mentioned Interpreter and C1 (we may need to look on C1 code generation to avoid vzeroupper). But they do not call all intrinsics as I said. And they are not performance critical.

-------------

PR Comment: https://git.openjdk.org/jdk/pull/16678#issuecomment-1815661968