2009-04-09 Catherine Moore <clm@codesourcery.com>

        * config/tc-mips.c (mips_fix_24k): Declare.
        (check_for_24k_errata): New.
        (mips_cleanup): Call check_for_24k_errata.
        (start_noreorder): Likewise.
        (md_mips_end): Likewise.
        (s_change_sec): Likewise.
        (s_change_section): Likewise.
        (append_insn): Call check_for_24k_errata.  Prevent
        ERET/DERET instructions from being moved into delay
        slots.
        (OPTION_FIX_24K): New.
        (OPTION_NO_FIX_24k) New.
        (md_longopts): Add "mfix-24k" and "mno-fix-24k".
        (md_parse_option): Handle fix-24k options.
        (md_show_usage): Display fix-24k options.
        * doc/c-mips.texi: Document.
        * testsuite/gas/mips/mips.exp: Run new tests.
        * testsuite/gas/mips/eret.s: New test.
        * testsuite/gas/mips/eret.d: New test output.
        * testsuite/gas/mips/eret.l: New test output.

1 files changed, 131 insertions, 3 deletions

diff --git a/gas/config/tc-mips.c b/gas/config/tc-mips.c
index 62d4e4f..5c85845 100644
--- a/gas/config/tc-mips.c
+++ b/gas/config/tc-mips.c
@@ -760,6 +760,9 @@ static int mips_fix_vr4120;
 /* ...likewise -mfix-vr4130.  */
 static int mips_fix_vr4130;
 
+/* ...likewise -mfix-24k.  */
+static int mips_fix_24k;
+
 /* We don't relax branches by default, since this causes us to expand
    `la .l2 - .l1' if there's a branch between .l1 and .l2, because we
    fail to compute the offset before expanding the macro to the most
@@ -1789,6 +1792,85 @@ reg_lookup (char **s, unsigned int types, unsigned int *regnop)
   return reg >= 0;
 }
 
+#define INSN_ERET  0x42000018
+#define INSN_DERET 0x4200001f
+
+/*  Implement the ERET/DERET Errata for MIPS 24k.
+ 
+    If an ERET/DERET is encountered in a noreorder block,
+    warn if the ERET/DERET is followed by a branch instruction.
+    Also warn if the ERET/DERET is the last instruction in the 
+    noreorder block.
+
+    IF an ERET/DERET is in a reorder block and is followed by a
+    branch instruction, insert a nop.  */
+
+static void
+check_for_24k_errata (struct mips_cl_insn *insn, int eret_ndx)
+{
+  bfd_boolean next_insn_is_branch = FALSE;
+
+  /* eret_ndx will be -1 for the last instruction in a section
+     and the ERET/DERET will be in insn, not history.  */
+  if (insn
+      && eret_ndx == -1
+      && (insn->insn_opcode == INSN_ERET
+	  || insn->insn_opcode == INSN_DERET)
+      && insn->noreorder_p)
+    {
+      as_warn (_("ERET and DERET must be followed by a NOP on the 24K."));
+      return;
+    }
+   
+  if (history[eret_ndx].insn_opcode != INSN_ERET
+      && history[eret_ndx].insn_opcode != INSN_DERET)
+    return;
+
+  if (!insn)
+    {
+      if (history[eret_ndx].noreorder_p)
+	as_warn (_("ERET and DERET must be followed by a NOP on the 24K."));
+      return;
+    }
+
+  next_insn_is_branch = ((insn->insn_opcode == INSN_ERET)
+			 || (insn->insn_opcode == INSN_DERET)
+			 || (insn->insn_mo->pinfo
+			     & (INSN_UNCOND_BRANCH_DELAY
+				| INSN_COND_BRANCH_DELAY
+				| INSN_COND_BRANCH_LIKELY)));
+
+  if (next_insn_is_branch && history[eret_ndx].noreorder_p)
+    {
+      as_warn (_("ERET and DERET must be followed by a NOP on the 24K."));
+      return;
+    }
+
+  /* Emit nop if the next instruction is a branch.  */ 
+  if (next_insn_is_branch)
+    {
+      long nop_where, br_where;
+      struct frag *nop_frag, *br_frag;
+      struct mips_cl_insn br_insn, nop_insn;
+
+      emit_nop ();
+
+      nop_insn = history[eret_ndx - 1]; 
+      nop_frag = history[eret_ndx - 1].frag;
+      nop_where = history[eret_ndx - 1].where;
+
+      br_insn = history[eret_ndx];
+      br_frag = history[eret_ndx].frag;
+      br_where = history[eret_ndx].where;
+
+      move_insn (&nop_insn, br_frag, br_where);
+      move_insn (&br_insn, nop_frag, nop_where);
+
+      history[eret_ndx-1] = br_insn;
+      history[eret_ndx] = nop_insn;
+    }
+}
+
 /* Return TRUE if opcode MO is valid on the currently selected ISA and
    architecture.  If EXPANSIONP is TRUE then this check is done while
    expanding a macro.  Use is_opcode_valid_16 for MIPS16 opcodes.  */
@@ -2074,6 +2156,9 @@ md_begin (void)
 void
 md_mips_end (void)
 {
+  if (mips_fix_24k)
+    check_for_24k_errata ((struct mips_cl_insn *) &history[0], -1);
+
   if (! ECOFF_DEBUGGING)
     md_obj_end ();
 }
@@ -2705,6 +2790,7 @@ append_insn (struct mips_cl_insn *ip, expressionS *address_expr,
 	     bfd_reloc_code_real_type *reloc_type)
 {
   unsigned long prev_pinfo, pinfo;
+  int hndx_24k = 0;
   relax_stateT prev_insn_frag_type = 0;
   bfd_boolean relaxed_branch = FALSE;
   segment_info_type *si = seg_info (now_seg);
@@ -3238,7 +3324,11 @@ append_insn (struct mips_cl_insn *ip, expressionS *address_expr,
 	      || (mips_opts.mips16 && history[0].fixp[0])
 	      /* If the previous instruction is a sync, sync.l, or
 		 sync.p, we can not swap.  */
-	      || (prev_pinfo & INSN_SYNC))
+	      || (prev_pinfo & INSN_SYNC)
+	      /* If the previous instruction is an ERET or
+		 DERET, avoid the swap.  */
+              || (history[0].insn_opcode == INSN_ERET)
+              || (history[0].insn_opcode == INSN_DERET))
 	    {
 	      if (mips_opts.mips16
 		  && (pinfo & INSN_UNCOND_BRANCH_DELAY)
@@ -3258,6 +3348,8 @@ append_insn (struct mips_cl_insn *ip, expressionS *address_expr,
 		     slot, and bump the destination address.  */
 		  insert_into_history (0, 1, ip);
 		  emit_nop ();
+		  if (mips_fix_24k)
+		    hndx_24k++;
 		}
 		
 	      if (mips_relax.sequence)
@@ -3297,7 +3389,14 @@ append_insn (struct mips_cl_insn *ip, expressionS *address_expr,
 	  /* If that was an unconditional branch, forget the previous
 	     insn information.  */
 	  if (pinfo & INSN_UNCOND_BRANCH_DELAY)
-	    mips_no_prev_insn ();
+	    {
+	      /* Check for eret/deret before clearing history.  */
+	      if (mips_fix_24k)
+		check_for_24k_errata (
+			(struct mips_cl_insn *) &history[hndx_24k],
+			hndx_24k+1);
+	      mips_no_prev_insn ();
+	    }
 	}
       else if (pinfo & INSN_COND_BRANCH_LIKELY)
 	{
@@ -3307,6 +3406,8 @@ append_insn (struct mips_cl_insn *ip, expressionS *address_expr,
 	     the next instruction.  */
 	  insert_into_history (0, 1, ip);
 	  emit_nop ();
+	  if (mips_fix_24k)
+	    hndx_24k++;
 	}
       else
 	insert_into_history (0, 1, ip);
@@ -3314,6 +3415,10 @@ append_insn (struct mips_cl_insn *ip, expressionS *address_expr,
   else
     insert_into_history (0, 1, ip);
 
+  if (mips_fix_24k)
+    check_for_24k_errata ((struct mips_cl_insn *) &history[hndx_24k],
+			  hndx_24k+1);
+
   /* We just output an insn, so the next one doesn't have a label.  */
   mips_clear_insn_labels ();
 }
@@ -3400,6 +3505,9 @@ start_noreorder (void)
 static void
 end_noreorder (void)
 {
+  if (mips_fix_24k)
+    check_for_24k_errata (NULL, 0);
+
   mips_opts.noreorder--;
   if (mips_opts.noreorder == 0 && prev_nop_frag != NULL)
     {
@@ -11175,7 +11283,9 @@ enum options
     OPTION_M3900,
     OPTION_NO_M3900,
     OPTION_M7000_HILO_FIX,
-    OPTION_MNO_7000_HILO_FIX,
+    OPTION_MNO_7000_HILO_FIX, 
+    OPTION_FIX_24K,
+    OPTION_NO_FIX_24K,
     OPTION_FIX_VR4120,
     OPTION_NO_FIX_VR4120,
     OPTION_FIX_VR4130,
@@ -11268,6 +11378,8 @@ struct option md_longopts[] =
   {"mno-fix-vr4120", no_argument, NULL, OPTION_NO_FIX_VR4120},
   {"mfix-vr4130",    no_argument, NULL, OPTION_FIX_VR4130},
   {"mno-fix-vr4130", no_argument, NULL, OPTION_NO_FIX_VR4130},
+  {"mfix-24k",    no_argument, NULL, OPTION_FIX_24K},
+  {"mno-fix-24k", no_argument, NULL, OPTION_NO_FIX_24K},
 
   /* Miscellaneous options.  */
   {"trap", no_argument, NULL, OPTION_TRAP},
@@ -11521,6 +11633,14 @@ md_parse_option (int c, char *arg)
       mips_opts.ase_smartmips = 0;
       break;
 
+    case OPTION_FIX_24K:
+      mips_fix_24k = 1;
+      break;
+
+    case OPTION_NO_FIX_24K:
+      mips_fix_24k = 0;
+      break;
+
     case OPTION_FIX_VR4120:
       mips_fix_vr4120 = 1;
       break;
@@ -12468,6 +12588,10 @@ s_change_sec (int sec)
 #endif
 
   mips_emit_delays ();
+
+  if (mips_fix_24k)
+    check_for_24k_errata ((struct mips_cl_insn *) &history[0], -1);
+
   switch (sec)
     {
     case 't':
@@ -12526,6 +12650,9 @@ s_change_section (int ignore ATTRIBUTE_UNUSED)
   if (!IS_ELF)
     return;
 
+  if (mips_fix_24k)
+    check_for_24k_errata ((struct mips_cl_insn *) &history[0], -1);
+
   section_name = input_line_pointer;
   c = get_symbol_end ();
   if (c)
@@ -15457,6 +15584,7 @@ MIPS options:\n\
   fprintf (stream, _("\
 -mfix-vr4120		work around certain VR4120 errata\n\
 -mfix-vr4130		work around VR4130 mflo/mfhi errata\n\
+-mfix-24k		insert a nop after ERET and DERET instructions\n\
 -mgp32			use 32-bit GPRs, regardless of the chosen ISA\n\
 -mfp32			use 32-bit FPRs, regardless of the chosen ISA\n\
 -msym32			assume all symbols have 32-bit values\n\