Question of the suitable time to call `free_bb_for_insn()'

Question of the suitable time to call `free_bb_for_insn()'

[Ling-hua Tseng]

I'm porting the GCC 4.0.2 (2005-08-11 snapshot) to a new VLIW architecture.

I figured out the `free_bb_for_insn()' is called before the reorg pass,
and I would like to use the CFG in the reorg pass for a reason.

The reason is:
    I would like to change flag_schedule_insns_after_reload to 0 by the macro OVERRIDE_OPTIONS if it was set,
    and then I would like to call the sched2 pass in some location of the hook TARGET_MACHINE_DEPENDENT_REORG.
    Perhaps I will manually do some instruction scheduling in the reorg pass in the future.

So I have two questions:
    1. Is it safe to move the line `free_bb_for_insn ();' to the next line of `rest_of_handle_machine_reorg ();' ?
    2. If it is safe, would the GCC team like to move it to there for allowing other ones can use CFG info
        in the reorg pass?

By the way, I noticed that the ia64 port did something which is similar to mine.
But it do some effort for recoding something before the reorg pass.
Moreover, it's forced to call the `schedule_ebbs()' however(I'd like to call `schedule_insns()').

Thanks a lot.

Re: Question of the suitable time to call `free_bb_for_insn()'

[Ling-hua Tseng]

I'm sorry that I didn't trace the cfgrtl.c before I posting the question.
Now I see that I can get the info again by calling compute_bb_for_insn().

On Sun, 14 Aug 2005 09:15:49 +0800, Ling-hua Tseng wrote
> I'm porting the GCC 4.0.2 (2005-08-11 snapshot) to a new VLIW architecture.
> 
> I figured out the `free_bb_for_insn()' is called before the reorg 
> pass, and I would like to use the CFG in the reorg pass for a reason.
> 
> The reason is:
>     I would like to change flag_schedule_insns_after_reload to 0 by 
> the macro OVERRIDE_OPTIONS if it was set,    and then I would like 
> to call the sched2 pass in some location of the hook 
TARGET_MACHINE_DEPENDENT_REORG.
>     Perhaps I will manually do some instruction scheduling in the 
> reorg pass in the future.
> 
> So I have two questions:
> 
>     1. Is it safe to move the line `free_bb_for_insn ();' to the 
> next line of `rest_of_handle_machine_reorg ();' ?
>     2. If it is safe, would the GCC team like to move it to there 
> for allowing other ones can use CFG info        in the reorg pass?
> 
> By the way, I noticed that the ia64 port did something which is 
> similar to mine. But it do some effort for recoding something before 
> the reorg pass. Moreover, it's forced to call the `schedule_ebbs()' 
> however(I'd like to call `schedule_insns()').
> 
> Thanks a lot.

Re: Question of the suitable time to call `free_bb_for_insn()'

[Richard Henderson]

On Sun, Aug 14, 2005 at 09:15:49AM +0800, Ling-hua Tseng wrote:
> I figured out the `free_bb_for_insn()' is called before the reorg pass,
> and I would like to use the CFG in the reorg pass for a reason.

You can't, because the reorg pass destroys the CFG.  You'd have to
recompute the CFG from scratch.


r~