Re: how to inline "ROR/ROL" asm instructions in C ?? (help wanted)

Ge' Weijers (ge@Progressive-Systems.Com)
Thu, 8 Oct 1998 12:49:54 -0400 (EDT)

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On Sun, 4 Oct 1998, Werner Koch wrote:

> #if defined(__GNUC__) && defined(__i386__)
> static inline u32
> rol(int n, u32 x)
> {
> __asm__("roll %%cl,%0"
> :"=r" (x)
> :"0" (x),"c" (n));
> return x;
> }
> #else
> #define rol(n,x) ( ((x) << (n)) | ((x) >> (32-(n))) )
> #endif

I use

    __asm__ ("roll %2,%0" : "=r"(x) : "0" (x) , "ic" ((unsigned char)n));

to get an inlined literal rotation count if it happens to be a
constant. A minor addition.

Ge'

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Ge' Weijers Voice: (614)326 4600
Progressive Systems, Inc. FAX: (614)326 4601
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