reload question - the compiler fails to find register to spill in a class

[Tomer Benyamini]

Hi,

I'm developing a gcc based compiler and in a certain scenario I get the following reload crash:
"error: unable to find a register to spill in class 'AB_REGS'"

I looked into it and it looks like it happens when all the AB_REGS registers are taken as function arguments, and the prefered class in a certain insn for a pseudo register is AB_REGS. This despite the fact that an alternative that includes GENERAL_REGS (r) has been chosen for that insn.

Why does reload crash and doesn't try to use other registers from GENERAL_REGS class?
What is the correct way to handle this problem?

Thanks,
Tomer