On Thu, May 16, 2002 at 11:06:50PM -0400, John Baldwin wrote:
> With gcc 2.95, when a register was passed to this function, the value
> was zero-extended using the zapnot instruction.
If so, that was incorrect.
The Alpha OSF/1 ABI specifies that all 32-bit arguments and return values
are to be sign-extended in their registers, regardless of the signedness
of the type involved.
This is done because manipulating sign-extended values is much more
efficient on the architecture. Not that gcc always takes advantage...
However, in this case I don't think that has anything to do with it.
Your inline assembly is wrong. You passed a 32-bit type to the asm,
and got a correct 32-bit value. Except that you then use it as a
64-bit value. You can expect, in general, for gcc to give you garbage
in the high-order bits. Why? Because you've not given the compiler
any reason to think that it matters. Certainly you wouldn't want the
compiler to extend the value if you were only going to store the
low N bits.
So you're going to have to change this to either
"r" ((long)(int)cmpval)
or
"r" ((unsigned long)cmpval)
as you choose. Naturally, the first is more efficient, since you
don't have to have the zap in the inline assembly.
r~
