Re: Difference between 'FOR_EACH_BB' and 'for (i=0; i<n_basic_blocks; i++){}'

["sean yang" <seanatpurdue at hotmail dot com>]

Thanks. after reading expunge_block(), i am curious whether " 'for (i=0; 
i<n_basic_blocks; i++){}" even works: from one hand, as routines such as 
'compute_defs_uses_and_gen()' uses it, it should work; from the other hand, 
from the code of expunge_block, BASIC_BLOCK[n_basic_blocks-1] may not be the 
last element in the BASIC_BLOCK array.
For example,
BASIC_BLOCK is like this, [b0, NULL, b1, NULL, b3 ]; aparently, 
n_basic_blocks ==3.

Shouldn't those code with 'for (i=0; i<n_basic_blocks; i++){}" be a problem? 
Maybe it did not cause a problem because all these code get executed before 
any basic_block cleanup.

Thanks,
Sean

---------------------------------------------
   expunge_block (basic_block b)
   {
     unlink_block (b);
     BASIC_BLOCK (b->index) = NULL;
     n_basic_blocks--;
     /* We should be able to ggc_free here, but we are not.
        The dead SSA_NAMES are left pointing to dead statements that are 
pointing
        to dead basic blocks making garbage collector to die.
        We should be able to release all dead SSA_NAMES and at the same 
time we should
        clear out BB pointer of dead statements consistently.  */
   }
-----------------------------------------------


> From: Diego Novillo <dnovillo@redhat.com>
> To: sean yang <seanatpurdue@hotmail.com>
> CC: gcc@gcc.gnu.org
> Subject: Re: Difference between 'FOR_EACH_BB' and 'for (i=0; 
> i<n_basic_blocks;  i++){}'
> Date: Thu, 01 Jun 2006 14:51:54 -0400
>
> sean yang wrote on 06/01/06 14:44:
>
> > 'for (i=0; i<n_basic_blocks; i++){bb=BASIC_BLOCK(i);}'  traverses 
> accoring to the
> > BB's index (because BASIC_BLOCK(i)->index ==i)
> >
> The first form may take you to a NULL basic block.  See expunge_block.

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