[patch] tree-phinode.c: Clean up remove_phi_node.

[Kazu Hirata <kazu at cs dot umass dot edu>]

Hi,

Attached is a patch to clean up remove_phi_node.

First note that there is some code duplication, namely calls to
release_ssa_name and release_phi_node.

Next note that the first iteration of the "for" loop in
remove_phi_node never has "t == phi" because of the second "if"
statement.

The patch cleans up remove_phi_node while resolving the problems
above.  It assumes that bb_for_stmt (phi) == bb.

Looking at the tree dump, I see that remove_phi_node now has 5 basic
blocks instead of 15 basic blocks.

The rdtsc instruction on x86 shows 5% speed-up although its effect is
not measurable on a larger scale.

Tested on i686-pc-linux-gnu.  OK to apply?

Kazu Hirata

2005-03-02  Kazu Hirata  <kazu@cs.umass.edu>

	* tree-phinodes.c (remove_phi_node): Clean up by factoring out
	calls to release_ssa_name and release_phi_node.

Index: tree-phinodes.c
===================================================================
RCS file: /cvs/gcc/gcc/gcc/tree-phinodes.c,v
retrieving revision 2.29
diff -c -d -p -r2.29 tree-phinodes.c
*** tree-phinodes.c	2 Dec 2004 02:49:29 -0000	2.29
--- tree-phinodes.c	1 Mar 2005 04:47:31 -0000
*************** remove_phi_args (edge e)
*** 404,439 ****
  void
  remove_phi_node (tree phi, tree prev, basic_block bb)
  {
!   if (prev)
!     {
!       /* Rewire the list if we are given a PREV pointer.  */
!       PHI_CHAIN (prev) = PHI_CHAIN (phi);
  
!       /* If we are deleting the PHI node, then we should release the
! 	 SSA_NAME node so that it can be reused.  */
!       release_ssa_name (PHI_RESULT (phi));
!       release_phi_node (phi);
!     }
!   else if (phi == phi_nodes (bb))
      {
!       /* Update the list head if removing the first element.  */
!       bb_ann (bb)->phi_nodes = PHI_CHAIN (phi);
! 
!       /* If we are deleting the PHI node, then we should release the
! 	 SSA_NAME node so that it can be reused.  */
!       release_ssa_name (PHI_RESULT (phi));
!       release_phi_node (phi);
      }
    else
      {
!       /* Traverse the list looking for the node to remove.  */
!       tree prev, t;
!       prev = NULL_TREE;
!       for (t = phi_nodes (bb); t && t != phi; t = PHI_CHAIN (t))
! 	prev = t;
!       if (t)
! 	remove_phi_node (t, prev, bb);
      }
  }
  
  
--- 404,430 ----
  void
  remove_phi_node (tree phi, tree prev, basic_block bb)
  {
!   tree *loc;
  
!   if (prev)
      {
!       loc = &PHI_CHAIN (prev);
      }
    else
      {
!       for (loc = &(bb_ann (bb)->phi_nodes);
! 	   *loc != phi;
! 	   loc = &PHI_CHAIN (*loc))
! 	;
      }
+ 
+   /* Remove PHI from the chain.  */
+   *loc = PHI_CHAIN (phi);
+ 
+   /* If we are deleting the PHI node, then we should release the
+      SSA_NAME node so that it can be reused.  */
+   release_ssa_name (PHI_RESULT (phi));
+   release_phi_node (phi);
  }