On Fri, Mar 28, 2008 at 10:51:16AM +0100, Klaas-Jan Stol wrote:
> Attached is a patch implementing:
>
> * ++ and -- postfix operators, implemented as n_sub and n_add (taking
> "1" as the 3rd operand), this is because each instruction must have an
> output register as far as I can tell (so "inc"/"dec" won't work).
It really needs to be inc/dec. And not only that, but the output
value of postfix ++ and -- needs to be the value _before_ the
inc/dec operation. So the PIR code for postfix:++ should be
something like:
%r = clone %0
inc %0
Also, they need to have the "is lvalue(1)" trait so that PAST
knows that the operand is to be treated as an lvalue.
> I wasn't sure how to implement +=; how to spell that? (as there's only
> a ":=" operator right now). I figured that ++ and -- are probably more
> used anyway, and if you want to += 2, then you can always use the
> normal assignment syntax.
Ideally += should be implemented as the two-argument 'add' opcode
in PIR... something like
add %0, %1
But the PAST compiler doesn't yet have a great way for distinguishing
a 2-argument add from a 3-argument add. We can get close with
add_p_p %0, %1
but of course that means that an expression like += 2 would end up
creating a PMC for the 2 constant. And PAST needs a way to know
that the result is in the %0 argument as opposed to a new
unique register (this is planned but not yet implemented).
> * <, <=, > and >= operators
The relational ops in the patch appear to be using iseq and
isne; I think it would make more sense for them to use islt,
isle, isgt, isge.
Also, we should have tests for all of the above.
Thanks!
Pm
