Re: [ros-dev] [ros-diffs] [greatlrd] 23826: Wrote RtlUshotByteSwap RtlUlongByteSwap and RtlUlonglongByteSwap to asm code. but we need a C api for header to linking it right. Put the asm version to i386

[Reuel ben Yisrael]

greatlrd(a)svn.reactos.org wrote:
>  Author: greatlrd
> Date: Thu Aug 31 01:17:53 2006
> New Revision: 23826
> URL: http://svn.reactos.org/svn/reactos?rev=23826&view=rev
> Log:
> Wrote  RtlUshotByteSwap RtlUlongByteSwap and  RtlUlonglongByteSwap to asm code.
>    but we need a C api for header to linking it right. Put the asm version to i386
>  
sure there must be away to avoid this double-function-call overhead?
>  +.globl _UlongByteSwap
> +
> +.intel_syntax noprefix
> +
> +/* FUNCTIONS ***************************************************************/
> +
> +_UlongByteSwap:
> +                       push  ebp          // save base
> +                       mov   ebp,esp      // move stack to base
> +                       mov   eax,[ebp+8]  // load the ULONG
> +                       bswap eax          // swap the ULONG
> +                       pop   ebp          // restore the base
> +                       ret
>  
this should work:
_UlongByteSwap:
                       mov   eax,[esp+8]  // load the ULONG
                       bswap eax          // swap the ULONG
                       ret
>  +.globl _UlonglongByteSwap
> +
> +.intel_syntax noprefix
> +
> +/* FUNCTIONS ***************************************************************/
> +
> +_UlonglongByteSwap:
> +                       push  ebp          // save base
> +                       mov   ebp,esp      // move stack to base
> +                       mov   edx,[ebp+8]  // load the higher part of ULONGLONG
> +                       mov   eax,[ebp+12] // load the lower part of ULONGLONG
> +                       bswap edx          // swap the higher part
> +                       bswap eax          // swap the lower part
> +                       pop   ebp          // restore the base
> +                       ret
>  
_UlonglongByteSwap:
                       mov   edx,[esp+8]  // load the higher part of ULONGLONG
                       mov   eax,[esp+12] // load the lower part of ULONGLONG
                       bswap edx          // swap the higher part
                       bswap eax          // swap the lower part
                       ret
>  +_UshortByteSwap:
> +                       push  ebp          // save base
> +                       mov   ebp,esp      // move stack to base
> +                       mov   eax,[ebp+8]  // load the USHORT
> +                       bswap eax          // swap the USHORT, xchg is slow so we use
> bswap with rol
> +                       rol   eax,16       // make it USHORT
> +                       pop   ebp          // restore the base
> +                       ret
>  
_UshortByteSwap:
                       mov   eax,[esp+8]  // load the USHORT
                       bswap eax          // swap the USHORT, xchg is slow so we use bswap
with rol
                       rol   eax,16       // make it USHORT
                       ret
or to save a byte...
_UshortByteSwap:
                       mov   ebx,[esp+8]  // load the USHORT
                       mov   al, bh
                       mov   ah, bl
                       ret