[Mono-dev] Proposed endian optimization - s390x

[Alex Rønne Petersen]

Have you checked that GCC doesn't already optimize the functions here
into these instructions? If it doesn't, maybe we could write them in a
way that GCC more easily recognizes.

But if that's not the case, I don't see any particular reason we
couldn't do this.

Regards,
Alex

On Wed, Mar 11, 2015 at 8:05 PM, Neale Ferguson <neale at sinenomine.net> wrote:
> Hi,
>  I am proposing the following changes to mono-endian.h to optimize
> little-endian to big-endian processing for s390x. The architecture defines
> instructions for just this purpose so instead of doing shifts etc. we can
> just do this:
>
> --- a/mono/metadata/mono-endian.h
> +++ b/mono/metadata/mono-endian.h
> @@ -14,7 +14,49 @@ typedef union {
>         unsigned char cval [8];
>  } mono_rdouble;
>
> -#if NO_UNALIGNED_ACCESS
> +#if defined(__s390x__)
> +
> +#define read16(x)      s390x_read16(*(guint16 *)(x))
> +#define read32(x)      s390x_read32(*(guint32 *)(x))
> +#define read64(x)      s390x_read64(*(guint64 *)(x))
> +
> +static __inline__ guint16
> +s390x_read16(guint16 x)
> +{
> +       guint16 ret;
> +
> +       __asm__ ("      lrvr    %0,%1\n"
> +                "      sra     %0,16\n"
> +                : "=r" (ret) : "r" (x));
> +
> +       return(ret);
> +}
> +
> +static __inline__ guint32
> +s390x_read32(guint32 x)
> +{
> +       guint32 ret;
> +
> +       __asm__ ("      lrvr    %0,%1\n"
> +                : "=r" (ret) : "r" (x));
> +
> +       return(ret);
>
> +}
> +
> +static __inline__ guint64
> +s390x_read64(guint64 x)
> +{
> +       guint64 ret;
> +
> +       __asm__ ("      lrvgr   %0,%1\n"
> +                : "=r" (ret) : "r" (x));
> +
> +       return(ret);
> +}
> +
> +#else
> +
> +# if NO_UNALIGNED_ACCESS
>
>  guint16 mono_read16 (const unsigned char *x);
>  guint32 mono_read32 (const unsigned char *x);
> @@ -24,12 +66,14 @@ guint64 mono_read64 (const unsigned char *x);
>  #define read32(x) (mono_read32 ((const unsigned char *)(x)))
>  #define read64(x) (mono_read64 ((const unsigned char *)(x)))
>
> -#else
> +# else
>
>  #define read16(x) GUINT16_FROM_LE (*((const guint16 *) (x)))
>  #define read32(x) GUINT32_FROM_LE (*((const guint32 *) (x)))
>  #define read64(x) GUINT64_FROM_LE (*((const guint64 *) (x)))
>
> +# endif
> +
>  #endif
>
>  #define readr4(x,dest) \
>
>
> Any objections?
>
> Neale
>
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