[Patch] Add options to Xtensa to prevent certain branch relaxations

[Sterling Augustine <sterling at tensilica dot com>]

Under certain circumstances, it is undesirable for the Xtensa port of 
gas to relax branches into flix-style branches.  The attached patch adds 
options to control this behavior.

Tested under xtensa-unknown-elf

2009-01-07  Sterling Augustine  <sterling@tensilica.com>

	* config/tc-xtensa.c (produce_flix): New.
	(option_flix, optoin_no_generate_flix, option_no_flix) Define.
	(md_longopts): Add support for them.
	(md_parse_option): Likewise.
	(md_show_usage): Add help message.
	(finish_vinsn): Don't allow multi-slot flix when produce_flix
	option is set to FLIX_NONE.
	* config/xtensa-relax.c (transition_applies): Only relax to
	flix branches when produce_flix equals FLIX_ALL.
	* config/xtensa-relax.h (flix_level, FLIX_ALL, FLIX_NO_GENERATE
	FLIX_NONE): New.
	(produce_flix): Declare.

Index: config/tc-xtensa.c
===================================================================
RCS file: /cvs/src/src/gas/config/tc-xtensa.c,v
retrieving revision 1.107
diff -u -p -r1.107 tc-xtensa.c
--- config/tc-xtensa.c	21 Nov 2008 22:13:31 -0000	1.107
+++ config/tc-xtensa.c	7 Jan 2009 01:06:32 -0000
@@ -591,6 +591,7 @@ static xtensa_opcode xtensa_waiti_opcode
 /* Command-line Options.  */
 
 bfd_boolean use_literal_section = TRUE;
+enum flix_level produce_flix = FLIX_ALL;
 static bfd_boolean align_targets = TRUE;
 static bfd_boolean warn_unaligned_branch_targets = FALSE;
 static bfd_boolean has_a0_b_retw = FALSE;
@@ -635,6 +636,10 @@ enum
   option_density = OPTION_MD_BASE,
   option_no_density,
 
+  option_flix,
+  option_no_generate_flix,
+  option_no_flix,
+
   option_relax,
   option_no_relax,
 
@@ -693,6 +698,10 @@ struct option md_longopts[] =
   { "density", no_argument, NULL, option_density },
   { "no-density", no_argument, NULL, option_no_density },
 
+  { "flix", no_argument, NULL, option_flix },
+  { "no-generate-flix", no_argument, NULL, option_no_generate_flix },
+  { "no-allow-flix", no_argument, NULL, option_no_flix },
+
   /* Both "relax" and "generics" are deprecated and treated as equivalent
      to the "transform" option.  */
   { "relax", no_argument, NULL, option_relax },
@@ -775,6 +784,15 @@ md_parse_option (int c, char *arg)
     case option_no_link_relax:
       linkrelax = 0;
       return 1;
+    case option_flix:
+      produce_flix = FLIX_ALL;
+      return 1;
+    case option_no_generate_flix:
+      produce_flix = FLIX_NO_GENERATE;
+      return 1;
+    case option_no_flix:
+      produce_flix = FLIX_NONE;
+      return 1;
     case option_generics:
       as_warn (_("--generics is deprecated; use --transform instead"));
       return md_parse_option (option_transform, arg);
@@ -941,6 +959,16 @@ Xtensa options:\n\
   --[no-]target-align     [Do not] try to align branch targets\n\
   --[no-]longcalls        [Do not] emit 32-bit call sequences\n\
   --[no-]transform        [Do not] transform instructions\n\
+  --flix                  both allow hand-written and generate flix bundles\n\
+  --no-generate-flix      allow hand-written but do not generate\n\
+                          flix bundles\n\
+  --no-allow-flix         neither allow hand-written nor generate\n\
+                          flix bundles\n\
   --rename-section old=new Rename section 'old' to 'new'\n", stream);
 }
 
@@ -6180,6 +6208,14 @@ finish_vinsn (vliw_insn *vinsn)
   if (vinsn->format == XTENSA_UNDEFINED)
     vinsn->format = xg_find_narrowest_format (vinsn);
 
+  if (xtensa_format_num_slots (xtensa_default_isa, vinsn->format) > 1
+      && produce_flix == FLIX_NONE)
+    {
+      as_bad (_("The option \"--no-allow-flix\" prohibits multi-slot flix."));
+      xg_clear_vinsn (vinsn);
+      return;
+    }
+
   if (vinsn->format == XTENSA_UNDEFINED)
     {
       as_where (&file_name, &line);
Index: config/xtensa-relax.c
===================================================================
RCS file: /cvs/src/src/gas/config/xtensa-relax.c,v
retrieving revision 1.18
diff -u -p -r1.18 xtensa-relax.c
--- config/xtensa-relax.c	4 Nov 2008 23:11:02 -0000	1.18
+++ config/xtensa-relax.c	7 Jan 2009 01:06:32 -0000
@@ -1543,9 +1543,12 @@ transition_applies (insn_pattern *initia
 	  else if (!strcmp (option_name, "Loops"))
 	    option_available = (XCHAL_HAVE_LOOPS == 1);
 	  else if (!strcmp (option_name, "WideBranches"))
-	    option_available = (XCHAL_HAVE_WIDE_BRANCHES == 1);
+	    option_available 
+	      = (XCHAL_HAVE_WIDE_BRANCHES == 1 && produce_flix == FLIX_ALL);
 	  else if (!strcmp (option_name, "PredictedBranches"))
-	    option_available = (XCHAL_HAVE_PREDICTED_BRANCHES == 1);
+	    option_available
+	      = (XCHAL_HAVE_PREDICTED_BRANCHES == 1
+		 && produce_flix == FLIX_ALL);
 	  else if (!strcmp (option_name, "Booleans"))
 	    option_available = (XCHAL_HAVE_BOOLEANS == 1);
 	  else
Index: config/xtensa-relax.h
===================================================================
RCS file: /cvs/src/src/gas/config/xtensa-relax.h,v
retrieving revision 1.9
diff -u -p -r1.9 xtensa-relax.h
--- config/xtensa-relax.h	4 Nov 2008 23:11:02 -0000	1.9
+++ config/xtensa-relax.h	7 Jan 2009 01:06:32 -0000
@@ -177,4 +177,13 @@ extern TransitionTable *xg_build_widen_t
 extern bfd_boolean xg_has_userdef_op_fn (OpType);
 extern long xg_apply_userdef_op_fn (OpType, long);
 
+enum flix_level
+{
+  FLIX_ALL,
+  FLIX_NO_GENERATE,
+  FLIX_NONE
+};
+
+extern enum flix_level produce_flix;
+
 #endif /* !XTENSA_RELAX_H */