Hi,
The X86 instruction sar accepts only an immediate or the cl register as
shift width. The question is how to tell the compiler to use cl instead
of ecx/rcx.
I've solved my problem by casting the input parameter to unsigned char
in the input constraint:
"Ic"((unsigned char)shift)
(See also: http://linuxtv.org/hg/~tmerle/v4l2-library/rev/660e9b799e4b)
When browsing through the <bits/byteswap.h> header I noticed the
following instruction: __asm__ ("rorw $8, %w0"). The 'w' seems to limit
the zeroth input parameter to word size. Where is this behavior
documented? I looked at
http://gcc.gnu.org/onlinedocs/gcc/Extended-Asm.html
but couldn't find something related.
What's the "correct" approach here? Casting or using "sar %b2,%1"?
Thanks,
Gregor
