Re: Help with reloading

[Jeff Law <law at redhat dot com>]

On 12/20/10 01:47, Mohamed Shafi wrote:
> > I think this is a case where you're going to need a secondary reload to
> > force the immediate into a register if the destination is a non-symbolic MEM
> > or a pseudo without a hard reg and its equivalent address is non-symbolic.
>      I am not sure how i should be implementing this.
>      Currently in define_expand for move i have code to force the
> immediate value into a register if the destination is not a symbolic
> address. If i understand correctly this is the only place where i can
> decide what to do with the source depending on the destination. right?
Just changing the movxx expander is not sufficient since for this case 
you do not know until reload time whether or not a particular insn needs 
an extra register to implement the move.   That's the whole point of the 
secondary reload mechanism -- to allow you to allocate a scratch 
register during reloading to handle oddball cases like this.


In your secondary reload code you'll need to check for the case where 
the destination is a MEM and the source is an unallocated pseudo with a 
constant equivalent and return a suitable register class for that case.

Jeff