speed up Xtensa GAS port

[Bob Wilson <bwilson at tensilica dot com>]

I'm committing this patch to speed up the Xtensa port of GAS.  It makes a minor 
change to the order of fields in the "vliw_insn" structure so that most of the 
fields can be zero'ed with a single memset call.  It also adds a small 
optimization for the common case of an instruction with a single operation slot. 
 Tested with no regressions for an xtensa-elf target.

2005-12-20  Sterling Augustine  <sterling@tensilica.com>

	* config/tc-xtensa.c (xg_find_narrowest_format): Optimize 1 slot case.
	(xg_init_vinsn): Remove redundant initialization.
	(xg_clear_vinsn): Zero all the slots with a single memset.
	* config/xtensa-istack.h (vliw_insn): Move insnbuf field after slots.

Index: config/tc-xtensa.c
===================================================================
RCS file: /cvs/src/src/gas/config/tc-xtensa.c,v
retrieving revision 1.49
diff -u -p -r1.49 tc-xtensa.c
--- config/tc-xtensa.c	27 Oct 2005 22:16:31 -0000	1.49
+++ config/tc-xtensa.c	20 Dec 2005 17:51:13 -0000
@@ -6403,6 +6403,9 @@ xg_find_narrowest_format (vliw_insn *vin
   vliw_insn v_copy = *vinsn;
   xtensa_opcode nop_opcode = xtensa_nop_opcode;
 
+  if (vinsn->num_slots == 1)
+    return xg_get_single_format (vinsn->slots[0].opcode);
+
   for (format = 0; format < xtensa_isa_num_formats (isa); format++)
     {
       v_copy = *vinsn;
@@ -11417,8 +11420,6 @@ xg_init_vinsn (vliw_insn *v)
 
   for (i = 0; i < MAX_SLOTS; i++)
     {
-      tinsn_init (&v->slots[i]);
-      v->slots[i].opcode = XTENSA_UNDEFINED;
       v->slotbuf[i] = xtensa_insnbuf_alloc (isa);
       if (v->slotbuf[i] == NULL)
 	as_fatal (_("out of memory"));
@@ -11430,6 +11431,9 @@ static void
 xg_clear_vinsn (vliw_insn *v)
 {
   int i;
+
+  memset (v, 0, offsetof (vliw_insn, insnbuf));
+
   v->format = XTENSA_UNDEFINED;
   v->num_slots = 0;
   v->inside_bundle = FALSE;
@@ -11438,10 +11442,7 @@ xg_clear_vinsn (vliw_insn *v)
     debug_type = xt_saved_debug_type;
 
   for (i = 0; i < MAX_SLOTS; i++)
-    {
-      memset (&v->slots[i], 0, sizeof (TInsn));
-      v->slots[i].opcode = XTENSA_UNDEFINED;
-    }
+    v->slots[i].opcode = XTENSA_UNDEFINED;
 }
 
 
Index: config/xtensa-istack.h
===================================================================
RCS file: /cvs/src/src/gas/config/xtensa-istack.h,v
retrieving revision 1.6
diff -u -p -r1.6 xtensa-istack.h
--- config/xtensa-istack.h	17 Oct 2005 18:17:08 -0000	1.6
+++ config/xtensa-istack.h	20 Dec 2005 17:51:13 -0000
@@ -89,10 +89,10 @@ expressionS *tinsn_get_tok (TInsn *, int
 typedef struct vliw_insn
 {
   xtensa_format format;
-  xtensa_insnbuf insnbuf;
   int num_slots;
   unsigned int inside_bundle;
   TInsn slots[MAX_SLOTS];
+  xtensa_insnbuf insnbuf;
   xtensa_insnbuf slotbuf[MAX_SLOTS];
 } vliw_insn;