regclass FLOAT_INT_REGS on x86/graph coloring allocator

[Michael Matz <matzmich at cs dot tu-berlin dot de>]

Hi,

is the above mentioned class really a correct one. I can see the usage for
it, but it contains the GENERAL_REGS (32 bit intergers) and the floating
point regs. Now in my allocator I have the problem, that DF-mode pseudos
have it as alternate class when they are involved in a memory move. The
problem here is, that if finally the pseudo gets alloced to a GENERAL_REG,
it needs two of them, while, if it gets a FLOAT_REG it only needs
one. This makes it impossible to know beforehand the number of conflicts
this pseudo will make, so the interference graph isn't correct. I could be
conservative and take such pseudo's as needing two regs in the graph, but
this unecessarily constrains it if finally the pseudo get a FLOAT_REG.

Also this class has other problems. One case was, that a DF pseudo was
involved in a memmove and some arithmetic, but still it got alternate
class FLOAT_INT_REGS. If now the allocator e.g. allocates %ebx to it, the
arithmetic operations are invalid.  reload() fixed them up, but I wanted
to get rid of reload as far as possible (I'm so far, that I only need the
register eliminations from reload, on code only doing stuff in
GENERAL_REGS). So, the question is, are such irregular classes valid for
the prefered or alternate class, and are there other ports also having
such things?


Ciao,
Michael.