register allocation

[roy rosen <roy.1rosen@gmail.com>]

Hi All,

I am looking at the code generated by my port and it seems that I have
a problem that too many copies between registers are generated.
I looked a bit at the register allocation and wanted to verify that I
understand its behavior.

Is that true that it first chooses a register class for each pseodo
and only then starts coloring?

I think that my problem is that in my architecture there are two
register classes which can do all arithmetic operation but class X can
also do loads and stores and class Y can also do DSP operations.

So when there are for example two DSP operations and between them some
arithmetic operations I expect to use only class Y but GCC prefers to
copy registers and do the arithmetic operations using X because for
some reason it determined that the prefered class for the registers in
the arithmetic operations is X.

It seems that determining the class does not look at the whole flow
but rather looks only at insns in which the register appears.

Do I understand the situation correctly?
Is there something I can do about it?

Thanks, Roy.