Notes
-----

   There is some trickery concerning the `mul' and `imul' instructions
that deserves mention.  The 16-, 32-, and 64-bit expanding multiplies
(base opcode `0xf6'; extension 4 for `mul' and 5 for `imul') can be
output only in the one operand form.  Thus, `imul %ebx, %eax' does
*not* select the expanding multiply; the expanding multiply would
clobber the `%edx' register, and this would confuse `gcc' output.  Use
`imul %ebx' to get the 64-bit product in `%edx:%eax'.

   We have added a two operand form of `imul' when the first operand is
an immediate mode expression and the second operand is a register.
This is just a shorthand, so that, multiplying `%eax' by 69, for
example, can be done with `imul $69, %eax' rather than `imul $69, %eax,
%eax'.