Re: [patch] tree-phinodes.c: Speed up resize_phi_node.

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

Hi Diego,

> > 	* tree-phinodes.c (resize_phi_node): Copy only a portion of
> > 	the PHI node currently in use.
> > 
> OK with a comment above the computation of OLD_SIZE explaining why the
> shortcut is safe.

Thanks.  Attached is the final patch that I committed.

Kazu Hirata

2004-11-03  Kazu Hirata  <kazu@cs.umass.edu>

	* tree-phinodes.c (resize_phi_node): Copy only a portion of
	the PHI node currently in use.

Index: tree-phinodes.c
===================================================================
RCS file: /cvs/gcc/gcc/gcc/tree-phinodes.c,v
retrieving revision 2.17
diff -c -d -p -r2.17 tree-phinodes.c
*** tree-phinodes.c	2 Nov 2004 13:23:05 -0000	2.17
--- tree-phinodes.c	3 Nov 2004 21:22:11 -0000
*************** resize_phi_node (tree *phi, int len)
*** 254,262 ****
  
    gcc_assert (len >= PHI_ARG_CAPACITY (*phi));
  
!   /* Note that OLD_SIZE is guaranteed to be smaller than SIZE.  */
    old_size = (sizeof (struct tree_phi_node)
! 	     + (PHI_ARG_CAPACITY (*phi) - 1) * sizeof (struct phi_arg_d));
  
    new_phi = allocate_phi_node (len);
  
--- 254,264 ----
  
    gcc_assert (len >= PHI_ARG_CAPACITY (*phi));
  
!   /* The garbage collector will not look at the PHI node beyond the
!      first PHI_NUM_ARGS elements.  Therefore, all we have to copy is a
!      portion of the PHI node currently in use.  */
    old_size = (sizeof (struct tree_phi_node)
! 	     + (PHI_NUM_ARGS (*phi) - 1) * sizeof (struct phi_arg_d));
  
    new_phi = allocate_phi_node (len);