Re: [RFC PATCH] target/i386: avoid copying junk to extended ZMMReg fields

[Peter Maydell]

On Mon, 11 Apr 2022 at 17:56, Paolo Bonzini <pbonzini@redhat.com> wrote:
> Yeah, I actually wrote the memcpy() invocation because I was going to
> look at AVX later this year, which of course you couldn't know. :)
> What I came up after stealing parts of your nice comment is the
> following:
>
> /*
>   * Copy the relevant parts of a Reg value around. In the case where
>   * sizeof(Reg) > SIZE, these helpers operate only on the lower bytes of
>   * a 64 byte ZMMReg, so we must copy only those and keep the top bytes
>   * untouched in the guest-visible destination destination register.
>   * Note that the "lower bytes" are placed last in memory on big-endian
>   * hosts, which store the vector backwards in memory.  In that case the
>   * copy *starts* at B(SIZE - 1) and ends at B(0), the opposite of
>   * the little-endian case.
>   */
> #ifdef HOST_WORDS_BIGENDIAN
> #define MOVE(d, r) memcpy(&((d).B(SIZE - 1)), &(d).B(SIZE - 1), SIZE)

Typo -- 2nd argument should be operating on 'r', not 'd'.

> #else
> #define MOVE(d, r) memcpy(&(d).B(0), &(r).B(0), SIZE)
> #endif

Otherwise looks good.

thanks
-- PMM