Red Hat ENTERPRISE LINUX 4 Manual page 195

Chapter 6. Extensions to the C Language Family
Intel 386--
i386.h
q
, , , or
a b c d
that do not use upper halves)
Q
, , , or
a b c d
R
Legacy register--equivalent to
with 8-bit upper halves in a single instruction)
A
Specifies the
32-bit mode) intended to be returned with the
and the register holding the least significant bits.
a
f
Floating point register
t
First (top of stack) floating point register
u
Second floating point register
a
register
a
b
register
b
c
register
c
C
Specifies constant that can be easily constructed in SSE register without loading it from
memory.
d
register
d
D
register
di
S
register
si
register for the i386. For x86-64 it is equivalent to
register. (for 8-bit instructions, that do use upper halves)
r
or registers. This is primarily useful for 64-bit integer values (when in
a d
class in i386 mode. (for non-8-bit registers used together
register holding the most significant bits
d
class. (for 8-bit instructions
r
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