Re: [patch] tree-ssa-threadupdate.c: Remove copy_phis_to_block.

[Jeffrey A Law <law at redhat dot com>]

On Sun, 2004-11-07 at 01:20 -0500, Kazu Hirata wrote:
> Hi,
> 
> Attached is a patch to remove copy_phis_to_block as it is a duplicate
> of tree-ssa.c:flush_pending_stmt.
> 
> thread_block makes several copies of the basic block that a jump is
> threaded through and then calls copy_phis_to_block to install
> appropriate PHI arguments to each copy.  Note that
> 
> 1) these copies are made while keeping the order of PHI nodes
>    identical to the original basic block, and that
> 
> 2) ssa_redirect_edge stuffs PENDING_STMT in the same order as the PHI
>    nodes at the original basic block.
> 
> so the order of PHI nodes in PENDING_STMT and those at each copy are
> the same.  Thus copy_phis_to_block could walk through PENDING_STMT and
> the PHI chain at the same time like so:
> 
>   for (phi = phi_nodes (e->dest), arg = PENDING_STMT (e);
>        phi;
>        phi = TREE_CHAIN (phi), arg = TREE_CHAIN (arg))
>     {
>       :
>       :
>     }
> 
> rather than searching for a PHI node for every element in the linked
> list pointed to by PENDING_STMT.
> 
> It turns out that once we implement the idea above, copy_phis_to_block
> ends up being identical to tree-ssa.c:flush_pending_stmt, so the patch
> simply replaces the call to copy_phis_to_block with
> flush_pending_stmt.
> 
> Tested on i686-pc-linux-gnu.  OK to apply?
> 
> Kazu Hirata
> 
> 2004-11-07  Kazu Hirata  <kazu@cs.umass.edu>
> 
> 	* tree-ssa-threadupdate.c (copy_phis_to_block): Remove.
> 	(thread_block): Call flush_pending_stmt instead of
> 	copy_phis_to_block.
OK.

jeff