Patch: Add a stop bit in alignment for alloc.

[H. J. Lu]

On Tue, Mar 02, 2004 at 06:24:44PM -0800, Jim Wilson wrote:
> On Tue, 2004-03-02 at 12:36, H. J. Lu wrote:
> > 	* config/tc-ia64.c (align_frag): New.
> > 	(md_assemble): Set the tc_frag_data field in align_frag for
> > 	IA64_OPCODE_FIRST instructions.
> > 	(ia64_md_do_align): Set align_frag.
> > 	(ia64_handle_align): Add a stop bit if needed.
> 
> This looks good to me.
> 
> However, I don't think it is fool proof.  When we create an
> rs_align_code frag, we call frag_align_code, which calls frag_var, which
> calls frag_grow with the requested alignment - 1.  If there is no room
> left in this obstack, then frag_grow will create a new frag.  So in some
> cases, the alignment frag will be the one after align_frag.
> 
> There is also a loop in frag_grow which implies that the alignment frag
> could be arbitrarily later, however, it isn't clear to me why the loop
> is there.  So it looks like in rare cases the alignment frag could be
> two after align_frag, and maybe in even rarer cases it could be farther.
> 
> In order to handle this, I think we need a loop to search forward from
> align_frag to find the real alignment frag.  The first frag starting
> from align_frag that has rs_align_code is the alignment frag.

Here is the new patch.


H.J.
-------------- next part --------------
2004-03-02  H.J. Lu  <hongjiu.lu@intel.com>

	* config/tc-ia64.c (align_frag): New.
	(md_assemble): Set the tc_frag_data field in align_frag for
	IA64_OPCODE_FIRST instructions.
	(ia64_md_do_align): Set align_frag.
	(ia64_handle_align): Add a stop bit if needed.

	* config/tc-ia64.h (TC_FRAG_TYPE): New.
	(TC_FRAG_INIT): New.

--- gas/config/tc-ia64.c.alloc	2004-02-24 09:32:19.000000000 -0800
+++ gas/config/tc-ia64.c	2004-03-02 18:52:25.000000000 -0800
@@ -636,6 +636,9 @@ static struct gr {
   valueT value;
 } gr_values[128] = {{ 1, 0, 0 }};
 
+/* Remember the alignment frag.  */
+static fragS *align_frag;
+
 /* These are the routines required to output the various types of
    unwind records.  */
 
@@ -9990,7 +9993,24 @@ md_assemble (str)
   flags = idesc->flags;
 
   if ((flags & IA64_OPCODE_FIRST) != 0)
-    insn_group_break (1, 0, 0);
+    {
+      /* The alignment frag has to end with a stop bit only if the
+	 next instruction after the alignment directive has to be
+	 the first instruction in an instruction group.  */
+      if (align_frag)
+	{
+	  while (align_frag->fr_type != rs_align_code)
+	    {
+	      align_frag = align_frag->fr_next;
+	      assert (align_frag);
+	    }
+	  if (align_frag->fr_next == frag_now)
+	    align_frag->tc_frag_data = 1;
+	}
+
+      insn_group_break (1, 0, 0);
+    }
+  align_frag = NULL;
 
   if ((flags & IA64_OPCODE_NO_PRED) != 0 && qp_regno != 0)
     {
@@ -10808,6 +10828,8 @@ ia64_md_do_align (n, fill, len, max)
      int len ATTRIBUTE_UNUSED;
      int max ATTRIBUTE_UNUSED;
 {
+  /* The current frag is an alignment frag.  */
+  align_frag = frag_now;
   if (subseg_text_p (now_seg))
     ia64_flush_insns ();
 }
@@ -10823,13 +10845,20 @@ ia64_handle_align (fragp)
   static const unsigned char le_nop[]
     = { 0x0c, 0x00, 0x00, 0x00, 0x01, 0x00, 0x00, 0x00,
 	0x00, 0x02, 0x00, 0x00, 0x00, 0x00, 0x04, 0x00};
+  static const unsigned char le_nop_stop[]
+    = { 0x0d, 0x00, 0x00, 0x00, 0x01, 0x00, 0x00, 0x00,
+	0x00, 0x02, 0x00, 0x00, 0x00, 0x00, 0x04, 0x00};
 
   int bytes;
   char *p;
+  const unsigned char *nop;
 
   if (fragp->fr_type != rs_align_code)
     return;
 
+  /* Check if this frag has to end with a stop bit.  */
+  nop = fragp->tc_frag_data ? le_nop_stop : le_nop;
+
   bytes = fragp->fr_next->fr_address - fragp->fr_address - fragp->fr_fix;
   p = fragp->fr_literal + fragp->fr_fix;
 
@@ -10845,7 +10874,7 @@ ia64_handle_align (fragp)
     }
 
   /* Instruction bundles are always little-endian.  */
-  memcpy (p, le_nop, 16);
+  memcpy (p, nop, 16);
   fragp->fr_var = 16;
 }
 
--- gas/config/tc-ia64.h.alloc	2004-03-01 09:05:22.000000000 -0800
+++ gas/config/tc-ia64.h	2004-03-02 12:11:27.000000000 -0800
@@ -159,6 +159,10 @@ extern void ia64_convert_frag (fragS *);
 #define TC_DWARF2_EMIT_OFFSET		ia64_dwarf2_emit_offset
 #define tc_check_label(l)		ia64_check_label (l)
 
+/* Record if an alignment frag should end with a stop bit.  */
+#define TC_FRAG_TYPE			int
+#define TC_FRAG_INIT(FRAGP)		do {(FRAGP)->tc_frag_data = 0;}while (0)
+
 #define MAX_MEM_FOR_RS_ALIGN_CODE  (15 + 16)
 
 #define WORKING_DOT_WORD	/* don't do broken word processing for now */