Register allocation in GCC 4

[Nathan Sidwell]

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

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