Re: [Qemu-devel] [RFC PATCH v4 75/75] target/i386: convert pmovmskb/movmskps/movmskpd helpers to gvec style

[Richard Henderson]

On 8/21/19 10:29 AM, Jan Bobek wrote:
> +    for (intptr_t i = 0; i * sizeof(uint8_t) < oprsz; ++i) {
> +        const uint8_t t = a->B(i) & (1 << 7);
> +        ret |= i < 8 ? t >> (7 - i) : t << (i - 7);

You can avoid this variable shift by doing

  uint32_t t = a->B(i) >> 7;
  ret |= t << i;

> +uint64_t glue(helper_pmovmskbq, SUFFIX)(Reg *a, uint32_t desc)
> +{
> +    return glue(helper_pmovmskbd, SUFFIX)(a, desc);
>  }
...
> +DEF_GEN_INSN2_GVEC(vpmovmskb, Gd, Uqq, sd1_ool, XMM_OPRSZ, XMM_MAXSZ, 
> pmovmskbd_xmm)
> +DEF_GEN_INSN2_GVEC(vpmovmskb, Gq, Uqq, sq1_ool, XMM_OPRSZ, XMM_MAXSZ, 
> pmovmskbq_xmm)

What is the difference between these two?

Given that we aren't attempting avx512, uint32_t is sufficient for all of the
bytes of a YMM register.

I have a feeling that some of this should simply use target_ulong, so that a
direct assignment to the general register can be done without extra extensions
within the generated code.


r~