[Xtensa] fix obscure assembler relaxation bug

[Bob Wilson <bwilson at tensilica dot com>]

I've committed this patch from Sterling Augustine to fix a relaxation bug in 
GAS.  The problem can't be reproduced with the default Xtensa processor 
configuration, but I ran the testsuite to make sure the fix doesn't break 
anything else.  Apparently this bug has been latent for years, but it only 
happens for unusual processor configurations.

--Bob

2008-02-05  Sterling Augustine  <sterling@tensilica.com>
	
	* config/tc-xtensa.c (relax_frag_immed): Change internal consistency
	checks into assertions.  When relaxation produces an operation that
	does not fit in the current FLIX instruction, make sure that the
	operation is relaxed as needed to account for being placed following
	the current instruction.

Index: config/tc-xtensa.c
===================================================================
RCS file: /cvs/src/src/gas/config/tc-xtensa.c,v
retrieving revision 1.97
diff -u -p -r1.97 tc-xtensa.c
--- config/tc-xtensa.c	18 Jan 2008 19:13:48 -0000	1.97
+++ config/tc-xtensa.c	5 Feb 2008 19:03:18 -0000
@@ -8997,9 +8997,8 @@ relax_frag_immed (segT segP,
   IStack istack;
   offsetT frag_offset;
   int num_steps;
-  fragS *lit_fragP;
   int num_text_bytes, num_literal_bytes;
-  int literal_diff, total_text_diff, this_text_diff, first;
+  int literal_diff, total_text_diff, this_text_diff;
 
   assert (fragP->fr_opcode != NULL);
 
@@ -9038,36 +9037,46 @@ relax_frag_immed (segT segP,
   istack_init (&istack);
   num_steps = xg_assembly_relax (&istack, &tinsn, segP, fragP, frag_offset,
 				 min_steps, stretch);
-  if (num_steps < min_steps)
-    {
-      as_fatal (_("internal error: relaxation failed"));
-      return 0;
-    }
-
-  if (num_steps > RELAX_IMMED_MAXSTEPS)
-    {
-      as_fatal (_("internal error: relaxation requires too many steps"));
-      return 0;
-    }
+  assert (num_steps >= min_steps && num_steps <= RELAX_IMMED_MAXSTEPS);
 
   fragP->tc_frag_data.slot_subtypes[slot] = (int) RELAX_IMMED + num_steps;
 
   /* Figure out the number of bytes needed.  */
-  lit_fragP = 0;
   num_literal_bytes = get_num_stack_literal_bytes (&istack);
-  literal_diff =
-    num_literal_bytes - fragP->tc_frag_data.literal_expansion[slot];
-  first = 0;
-  while (istack.insn[first].opcode == XTENSA_UNDEFINED)
-    first++;
-
+  literal_diff
+    = num_literal_bytes - fragP->tc_frag_data.literal_expansion[slot];
   num_text_bytes = get_num_stack_text_bytes (&istack);
 
   if (from_wide_insn)
     {
+      int first = 0;
+      while (istack.insn[first].opcode == XTENSA_UNDEFINED)
+	first++;
+
       num_text_bytes += old_size;
       if (opcode_fits_format_slot (istack.insn[first].opcode, fmt, slot))
 	num_text_bytes -= xg_get_single_size (istack.insn[first].opcode);
+      else
+	{
+	  /* The first instruction in the relaxed sequence will go after
+	     the current wide instruction, and thus its symbolic immediates
+	     might not fit.  */
+	  
+	  istack_init (&istack);
+	  num_steps = xg_assembly_relax (&istack, &tinsn, segP, fragP, 
+					 frag_offset + old_size,
+					 min_steps, stretch + old_size);
+	  assert (num_steps >= min_steps && num_steps <= RELAX_IMMED_MAXSTEPS);
+
+	  fragP->tc_frag_data.slot_subtypes[slot] 
+	    = (int) RELAX_IMMED + num_steps;
+
+	  num_literal_bytes = get_num_stack_literal_bytes (&istack);
+	  literal_diff 
+	    = num_literal_bytes - fragP->tc_frag_data.literal_expansion[slot];
+	  
+	  num_text_bytes = get_num_stack_text_bytes (&istack) + old_size;
+	}
     }
 
   total_text_diff = num_text_bytes - old_size;
@@ -9086,7 +9095,7 @@ relax_frag_immed (segT segP,
   /* Find the associated expandable literal for this.  */
   if (literal_diff != 0)
     {
-      lit_fragP = fragP->tc_frag_data.literal_frags[slot];
+      fragS *lit_fragP = fragP->tc_frag_data.literal_frags[slot];
       if (lit_fragP)
 	{
 	  assert (literal_diff == 4);