Re: [Qemu-devel] [PATCH v2 1/4] target/mips: Fix emulation of ILVEV.<B|H|W> on big endian host

[Richard Henderson <richard.henderson@linaro.org>]

On 6/20/19 3:45 PM, Aleksandar Markovic wrote:
> From: Aleksandar Markovic <amarkovic@wavecomp.com>
> 
> Fix emulation of ILVEV.<B|H|W> on big endian host by applying
> mapping of data element indexes from one endian to another.
> 
> Signed-off-by: Aleksandar Markovic <amarkovic@wavecomp.com>
> Reviewed-by: Aleksandar Rikalo <arikalo@wavecomp.com>
> ---
>  target/mips/msa_helper.c | 37 +++++++++++++++++++++++++++++++++++++
>  1 file changed, 37 insertions(+)
> 
> diff --git a/target/mips/msa_helper.c b/target/mips/msa_helper.c
> index be059a3..215d8af 100644
> --- a/target/mips/msa_helper.c
> +++ b/target/mips/msa_helper.c
> @@ -1737,6 +1737,24 @@ void helper_msa_ilvev_df(CPUMIPSState *env, uint32_t df, uint32_t wd,
>  
>      switch (df) {
>      case DF_BYTE:
> +#if defined(TARGET_WORDS_BIGENDIAN)

The commit message talks about the endianness of the host, whereas this check
is for the endianness of the target.


> +        pwd->b[8]  = pws->b[9];
> +        pwd->b[9]  = pwt->b[9];
> +        pwd->b[10] = pws->b[11];
> +        pwd->b[11] = pwt->b[11];
> +        pwd->b[12] = pws->b[13];
> +        pwd->b[13] = pwt->b[13];
> +        pwd->b[14] = pws->b[15];
> +        pwd->b[15] = pwt->b[15];
> +        pwd->b[0]  = pws->b[1];
> +        pwd->b[1]  = pwt->b[1];
> +        pwd->b[2]  = pws->b[3];
> +        pwd->b[3]  = pwt->b[3];
> +        pwd->b[4]  = pws->b[5];
> +        pwd->b[5]  = pwt->b[5];
> +        pwd->b[6]  = pws->b[7];
> +        pwd->b[7]  = pwt->b[7];
> +#else
>          pwd->b[15] = pws->b[14];
>          pwd->b[14] = pwt->b[14];
>          pwd->b[13] = pws->b[12];

FWIW, avoiding this sort of duplication is why other targets define helper
macros like

PPC:
#define VsrB(i) u8[15 - (i)]
etc

ARM, S390:
/* Note that vector data is stored in host-endian 64-bit chunks,
   so addressing units smaller than that needs a host-endian fixup.  */
#ifdef HOST_WORDS_BIGENDIAN
#define H1(x)  ((x) ^ 7)
etc


r~