IRA memory cost calculation

[Michael Eager]

Jeff Law wrote:
> On 11/30/09 14:17, Michael Eager wrote:
>> I've run into a situation where assign_hard_reg()
>> decides that there are no registers available.
> That can certainly happen.  It's also the case that assign_hard_reg may 
> decide that memory is cheaper than a register and refuse to assign a 
> register for certain allocnos.
> 
>> This
>> results in a memory reference being substituted for a
>> pseudo-register.  There's no check to see if the modified
>> instruction is valid, which it isn't.
> reload performs this action, not IRA.   Reload is allowed to replace a 
> pseudo with its equivalent memory location, then emit whatever reloads 
> are necessary to fix up the resulting insn.  So what you need to do is 
> debug the generated reloads for the insn in question.
> 
> Often this kind of failure is a predicate, constraint or secondary 
> reload problem.

Thanks.  I did step through reload and it looked
like everything it was doing was OK.

I'll look at reload again and re-check constraints.


-- 
Michael Eager	 eager@eagercon.com
1960 Park Blvd., Palo Alto, CA 94306  650-325-8077