: [result]"=r" (y) /* Rotation result. */
: [value]"r" (x) /* Rotated value. */
: /* No clobbers */
);
In the code section, operands are referenced by a percent sign followed by the related symbolic name enclosed in square brackets. It refers to the entry in one of the operand lists that contains the same symbolic name. From the rotating bits example:
%[result] refers to output operand, the C variable y, and
%[value] refers to the input operand, the C variable x.