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Re: Register allocation in GCC 4


Nathan Sidwell wrote:
Jon Beniston wrote:

Hi,

I'm updating a GCC port to 4.0.0. I am seeing a problem whereby registers
that are set to 1 in fixed_regs are being used. The problem is occuring
quite early on in the compiler, as the registers appear in the 00.expand
dump. The problem seems to occur for a DCmode value that is being allocated
to several registers. The first 4 of these registers are not in fixed_regs,
but the last 4 are (regs are 16-bit). I have made sure HARD_REGNO_MODE_OK
for all these registers returns 0, but that hasn't had an effect. Can anyone
suggest where I need to be looking to track this down?


If I understand correctly the DCmode value occupies 8 registers, the last 4
of which are fixed regs.

HARD_REGNO_MODE_OK should return 0 for the first 4 too.
oh, sorry you said that :)

stick a breakpoint where that rtl is being created.  I guess it must be
to do with function calling or some target machine thingy, as those are the
only places hard regs get mentioned before register allocation.

nathan

--
Nathan Sidwell    ::   http://www.codesourcery.com   ::     CodeSourcery LLC
nathan@codesourcery.com    ::     http://www.planetfall.pwp.blueyonder.co.uk


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