very confused about single_set

2006-02-19 Thread Kenneth Zadeck 
Steven, Zdenek

1) single_set is built on top of single_set2.
2) single_set_2 uses REG_UNUSED notes.
3) tree-ssa-loop-ivops.c:seq_cost uses single_set.

I can find no indication that rtl dfa is run here to provide the
information for single_set to produce the correct answer.

Inquiring minds want to know.

Kenny

Re: very confused about single_set

2006-02-19 Thread Daniel Berlin 
On Sun, 2006-02-19 at 09:56 -0500, Kenneth Zadeck wrote:
> Steven, Zdenek
> 
> 1) single_set is built on top of single_set2.
Yes
> 2) single_set_2 uses REG_UNUSED notes.
Only if there are multiple sets.

> 3) tree-ssa-loop-ivops.c:seq_cost uses single_set.

This is because Zdenek builds RTL to determine target costs.

> 
> I can find no indication that rtl dfa is run here to provide the
> information for single_set to produce the correct answer.

I don't understand what you mean.
Why does the DFA need to be run to produce the correct answer?
(Our ports use Deterministic Finite Automaton based schedulers, so
saying DFA is an ambiguous term at best)

Or do you mean DataFlow Analysis, in which case, i'm sure everyone
expects the notes are always up to date (even though they may not be).

Re: very confused about single_set

2006-02-19 Thread Kenneth Zadeck 
Daniel Berlin wrote:
> On Sun, 2006-02-19 at 09:56 -0500, Kenneth Zadeck wrote:
>   
>> Steven, Zdenek
>>
>> 1) single_set is built on top of single_set2.
>> 
> Yes
>   
>> 2) single_set_2 uses REG_UNUSED notes.
>> 
> Only if there are multiple sets.
>
>   
>> 3) tree-ssa-loop-ivops.c:seq_cost uses single_set.
>> 
>
> This is because Zdenek builds RTL to determine target costs.
>
>   
>> I can find no indication that rtl dfa is run here to provide the
>> information for single_set to produce the correct answer.
>> 
>
> I don't understand what you mean.
> Why does the DFA need to be run to produce the correct answer?
> (Our ports use Deterministic Finite Automaton based schedulers, so
> saying DFA is an ambiguous term at best)
>
> Or do you mean DataFlow Analysis, in which case, i'm sure everyone
> expects the notes are always up to date (even though they may not be).
>
>
>   
I was refering to the reg_unused notes not being there at all when this
is called.  You are correct that this is not so much a correctness issue
as a place where the code is pessimistic.

kenny

Re: very confused about single_set

2006-02-19 Thread Zdenek Dvorak 
Hello,

> 1) single_set is built on top of single_set2.
> 2) single_set_2 uses REG_UNUSED notes.
> 3) tree-ssa-loop-ivops.c:seq_cost uses single_set.
> 
> I can find no indication that rtl dfa is run here to provide the
> information for single_set to produce the correct answer.

it is not.  Nevertheless, the notes are only relevant for insns with
more than one set, which are not common enough to care about them.
(also, seq_cost will disappear soon).

Zdenek