Re: [PATCH] Fix dom ICE (PR tree-optimization/55329)

[Jeff Law <law@redhat.com>]

On 11/15/2012 01:14 PM, Jakub Jelinek wrote:
> Hi!
>
> On the following testcase we ICE, because tree_ssa_dominator_optimize
> modifies the bitmap while iterating it.  In particular, it contained just
> a single bit in it, bitmap_clear_bit turned the bitmap into empty bitmap and
> bitmap_set_bit on a lower bit reused the same bitmap_element with lower
> index, but higher bit set in it, therefore EXECUTE_IF_SET_IN_BITMAP in next
> iteration gave bit above highest basic block.
>
> Fixed by never clearing any bits from the bitmap while traversing it,
> it isn't IMHO a big deal, gimple_purge_all_dead_eh_edges will in a few
> insns find out the forwarder block doesn't have any EDGE_EH edges and will
> do nothing for it, on the other side to handle even chained forwarder blocks
> it loops to find the last one.  Insertion of bits looks safe to me, we don't
> care if those inserted bits are processed again or not (nothing will be done
> for them anymore).
>
> Bootstrapped/regtested on x86_64-linux and i686-linux, ok for trunk?
>
> 2012-11-15  Jakub Jelinek  <jakub@redhat.com>
>
> 	PR tree-optimization/55329
> 	* tree-ssa-dom.c (tree_ssa_dominator_optimize): Never clear
> 	bits in needed_eh_cleanup while iterating over the bitmap.
> 	Look through all forwarder blocks at once.
>
> 	* g++.dg/opt/pr55329.C: New test.
This is fine.

I've still got a todo on my list from 2009 to have checking code to 
detect when a bitmap is changing while we're iterating on it.

jeff