Register allocation failure

[Dan Towner <dant at picochip dot com>]

Hi all,

I am writing a port of gcc for a 16-bit DSP. Up until now, the port has 
been based upon gcc 3.1, but I recently updated it to use the mainline 
source code of gcc. In this guise, I am encountering the following problem.

For a particular test case (991118-1.c actually), I get an assertion 
failure at the very start of insert-save. This is caused by the saving 
of register 1, which is a caller save register. From what I can find 
out, this register is being saved as the result of allocating a 
pseudo-register to register 1. If I look at the results of local 
register allocation (.lreg) this particular pseudo-register crosses 
several function calls, so surely it should conflict with the caller 
save register, and not be used? Furthermore, if I look in the global 
register dump (.dreg) it states that the pseudo-register conflicts with 
various hard registers, but not r1.

As far as I can see, there are two scenarios: 1) because the 
pseudo-register crosses function calls, it should conflict with all 
caller save registers, or 2) if the allocator has run out of registers, 
and thus uses a caller-save register, then the abort in saving the 
register in caller-save is incorrect? Or am I missing something?

Thanks,

Dan.

=============================================================================
Daniel Towner
picoChip Designs Ltd., Riverside Buildings, 108, Walcot Street, BATH, 
BA1 5BG
dant at picochip dot com
07786 702589