[PATCH,RFC] Do not assign stack slots to ssa names

[Michael Matz]

Hi,

On Wed, 10 Jun 2009, Andrey Belevantsev wrote:

> When processing stack vars partitions for alias export patch, I have 
> noticed that sometimes we get SSA_NAMEs being allocated on stack, e.g. 
> V2SF vectors.  Richard suggested the attached patch to fix it.

Yeah, while discussing this I tried the same.  But it actually changes the 
underlying assumptions of the stack slot allocation code, in precisely the 
way that is tested ...

> patch is bootstrapped and tested (Ada enabled) on x86-64.  The only 
> failing test is stack protector test ssp-2.c, in which an array and a 
> loop counter get allocated on stack in a different order and thus 
> instead of overflowing the array the test overflows the loop counter and 
> hangs.

... here.  _All_ stack slot allocations need to be deferred when stack 
protector is on (for the reason the comment therein explains), so that the 
reordering gets a chance to do it's job.  So ...

> So I've also fixed the test.
> 
> Michael, what do you think of the patch?

... I don't think this is going to fly.  What was the real problem again?  
IIRC it could also be fixed by giving those stack slots their own 
partition, right?


Ciao,
Michael.