frame pointer must be single register?

frame pointer must be single register?

[DJ Delorie]

Is there an unwritten rule that the frame pointer must be a single
hard register?  I'm working on a port where $fp is a register pair,
and I've seen gcc allocate the second register to other things
(causing all sorts of problems).

Re: frame pointer must be single register?

[Paul Koning]

On Jul 8, 2011, at 1:07 PM, DJ Delorie wrote:

> 
> Is there an unwritten rule that the frame pointer must be a single
> hard register?  I'm working on a port where $fp is a register pair,
> and I've seen gcc allocate the second register to other things
> (causing all sorts of problems).

Would it suffice simply to mark the second register as a reserved register?  That should take it away from the allocator, right?

	paul

Re: frame pointer must be single register?

[Jeff Law]

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On 07/08/11 11:07, DJ Delorie wrote:
> Is there an unwritten rule that the frame pointer must be a single
> hard register?  I'm working on a port where $fp is a register pair,
> and I've seen gcc allocate the second register to other things
> (causing all sorts of problems).
It's certainly caused problems (some of which I believe have been fixed
within the last year or so)...  I think there's a port (AVR?) that may
have similar characteristics.

jeff

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Re: frame pointer must be single register?

[Georg-Johann Lay]

Jeff Law wrote:
> On 07/08/11 11:07, DJ Delorie wrote:
>> Is there an unwritten rule that the frame pointer must be a single
>> hard register?  I'm working on a port where $fp is a register pair,
>> and I've seen gcc allocate the second register to other things
>> (causing all sorts of problems).
> It's certainly caused problems (some of which I believe have been fixed
> within the last year or so)...  I think there's a port (AVR?) that may
> have similar characteristics.
> 
> jeff

Yes, and fixing the second part appears not to be the right approach.
I just committed a patch to fix PR46779, PR45291.

Johann