bextr

x86_64 pr5ocessors ( 64Bit AMD at least ) offer the instruction bextr
(
AMD64 Architecture Programmer's Manual, Vol. 1:
Extgract Bitfield
...
The BEXTR instruction ( ... ) extracts a contiguous field of bits from 
the first source operand, as specified by the control field setting in 
the second source
operand and pots the extracted field into the least significant bit 
positions of the
destination. The remaining bits in the destination regitser are cleared to 0
)
but "as"/"gas" seems not to know bextr ( SuSE Linux 11.4 desktop ), but 
maybe it's
just that my operand coding
e.g.
bextr -8(%rbp),%r8,$4,%eax
is wrong.
Intended above ist take starting bit No from r8, fieldwidth 4, 
destination eax.
Unfortunately
the AMD- manual let's me only guess how doe denote it.
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