[patch] tree-phinodes.c: Speed up remove_phi_arg_num.

[Kazu Hirata]

Hi,

Attached is a patch to speed up remove_phi_arg_num by removing
unnecessary zeroing.

Now that the garbage collector no longer scans the array of PHI
arguments beyond num_args, we do not need to zero the PHI argument
that's being removed.

Note that all of these fields are properly set in add_phi_arg.  In
other words, add_phi_arg does not do things like leaving
PHI_ARG_NONZERO as is, expecting it to be set to false in
remove_phi_arg_num.

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

Kazu Hirata

2004-10-30  Kazu Hirata  <kazu@cs.umass.edu>

	* tree-phinodes.c (remove_phi_arg_num): Do not zero the
	element that's being removed.

Index: tree-phinodes.c
===================================================================
RCS file: /cvs/gcc/gcc/gcc/tree-phinodes.c,v
retrieving revision 2.14
diff -u -d -p -r2.14 tree-phinodes.c
--- tree-phinodes.c	29 Oct 2004 21:41:30 -0000	2.14
+++ tree-phinodes.c	29 Oct 2004 22:13:05 -0000
@@ -401,9 +401,6 @@ remove_phi_arg_num (tree phi, int i)
     }
 
   /* Shrink the vector and return.  */
-  SET_PHI_ARG_DEF (phi, num_elem - 1, NULL_TREE);
-  PHI_ARG_EDGE (phi, num_elem - 1) = NULL;
-  PHI_ARG_NONZERO (phi, num_elem - 1) = false;
   PHI_NUM_ARGS (phi)--;
 }