> -----Original Message-----
> From: Richard Biener [mailto:richard.guent...@gmail.com]
> Sent: 13 March 2014 13:24
> To: Paulo Matos
> Cc: gcc@gcc.gnu.org
> Subject: Re: dom requires PROP_loops
>
>
> Probably RTL cfgcleaup needs the same treatment as GIMPLE cfgcleanup
> then - allow removal if loop properties allows it.
>
In both cfgcleanup.c and tree-cfgcleanup.c I can see code that protects loop
latches, but I see no code that allows removal of latch if property allows it.
From what you say I would expect this would already be implemented in
tree-cfgcleanup.c, however what actually happens is that since current_loops is
non-null (PROP_loops is not destroyed in tree loopdone), tree-cfgcleanup call
chain ends up calling cleanup_tree_cfg_bb on the bb loop latch and
tree_forwarder_block_p returns false for bb because of the following code
thereby not removing the latch:
if (current_loops)
{
basic_block dest;
/* Protect loop latches, headers and preheaders. */
if (bb->loop_father->header == bb)
return false;
dest = EDGE_SUCC (bb, 0)->dest;
if (dest->loop_father->header == dest)
return false;
}
Why do we need to protect the latch?
Paulo Matos
> Richard.
>
