[PATCH v2 04/15] MIPS: Branch mapping support (pre-R6 to R6).

[Jovan Dmitrovic]

From: Robert Suchanek <Robert.Suchanek@imgtec.com>

Restrict mapping pre-R6 branches to R6 compact branches if there
is a non-NOP instruction in the delay slot, as compact branches in
microMIPS R6 do not have delay slots.

Signed-off-by: Robert Suchanek <Robert.Suchanek@imgtec.com>
Signed-off-by: Faraz Shahbazker <fshahbazker@wavecomp.com>
Signed-off-by: Milica Matic <milica.matic@htecgroup.com>

gas/ChangeLog:

        * config/tc-mips.c (append_insn): Disable converting from pre-R6 to R6
        compact branch instruction if delay slot is filled with non-NOP instruction.

include/ChangeLog:

        * opcode/mips.h (INSN2_CONVERTED_TO_COMPACT): New macro.

opcodes/ChangeLog:

        * mips-dis.c (is_isa_r6): New function.
        (print_insn_mips): Always dissasemble R6 converted compact branch.

---
 gas/config/tc-mips.c  | 34 +++++++++++++++++++++++++++++++++-
 include/opcode/mips.h |  2 ++
 opcodes/mips-dis.c    | 19 +++++++++++++++----
 3 files changed, 50 insertions(+), 5 deletions(-)

diff --git a/gas/config/tc-mips.c b/gas/config/tc-mips.c
index 8cd9f31c492..c7b677a213b 100644
--- a/gas/config/tc-mips.c
+++ b/gas/config/tc-mips.c
@@ -7750,6 +7750,37 @@ append_insn (struct mips_cl_insn *ip, expressionS *address_expr,
 			address_expr->X_add_number);
       *reloc_type = BFD_RELOC_UNUSED;
     }
+  else if (mips_opts.micromips
+	   && ISA_IS_R6 (mips_opts.isa)
+	   /* microMIPS pre-R6 to R6 branch/jump instruction mapping in
+	      noreorder block is restricted to have only a nop in the delay
+	      slot.  */
+	   && compact_branch_p (&history[0])
+	   && (history[0].insn_mo->pinfo2 & INSN2_CONVERTED_TO_COMPACT)
+	   && history[0].noreorder_p
+	   && strcmp (ip->insn_mo->name, "nop") != 0)
+    {
+      as_bad (_("unable to convert `%s' to its compact form because it has a non NOP "
+		"instruction (`%s') in its delay slot.  Please move the delay slot "
+		"instruction before the branch and disable noreorder."),
+	      history[0].insn_mo->name, ip->insn_mo->name);
+      add_fixed_insn (ip);
+    }
+  else if (mips_opts.micromips
+	   && ISA_IS_R6 (mips_opts.isa)
+	   && history[0].noreorder_p
+	   && (strcmp (history[0].insn_mo->name, "bal") == 0
+	       || strcmp (history[0].insn_mo->name, "jal") == 0
+	       || strcmp (history[0].insn_mo->name, "jalr") == 0
+	       || strcmp (history[0].insn_mo->name, "bgezal") == 0
+	       || strcmp (history[0].insn_mo->name, "bltzal") == 0))
+    {
+      as_bad (_("unable to convert `%s' to its compact form because the link register "
+		"would have a different value.  Please move the delay slot instruction "
+		"before the branch and disable noreorder."),
+	      history[0].insn_mo->name);
+      add_fixed_insn (ip);
+    }
   else if (mips_opts.micromips
 	   && address_expr
 	   && ((relax32 && *reloc_type == BFD_RELOC_16_PCREL_S2)
@@ -8083,8 +8114,9 @@ append_insn (struct mips_cl_insn *ip, expressionS *address_expr,
     }
 
   /* If we have just completed an unconditional branch, clear the history.  */
-  if ((delayed_branch_p (&history[1]) && uncond_branch_p (&history[1]))
+  if (((delayed_branch_p (&history[1]) && uncond_branch_p (&history[1]))
       || (compact_branch_p (&history[0]) && uncond_branch_p (&history[0])))
+      && !(history[0].insn_mo->pinfo2 & INSN2_CONVERTED_TO_COMPACT))
     {
       unsigned int i;
 
diff --git a/include/opcode/mips.h b/include/opcode/mips.h
index e5d9ef38177..a615cfdf2b4 100644
--- a/include/opcode/mips.h
+++ b/include/opcode/mips.h
@@ -887,6 +887,8 @@ mips_opcode_32bit_p (const struct mips_opcode *mo)
    encoding is needed or otherwise the final EXTEND entry will apply,
    for the disassembly of the prefix only.  */
 #define INSN2_SHORT_ONLY	    0x00010000
+/* This indicates pre-R6 instructions mapped to R6 ones.  */
+#define INSN2_CONVERTED_TO_COMPACT  0x00020000
 
 /* Masks used to mark instructions to indicate which MIPS ISA level
    they were introduced in.  INSN_ISA_MASK masks an enumeration that
diff --git a/opcodes/mips-dis.c b/opcodes/mips-dis.c
index a4cff73e268..b47b78c84fe 100644
--- a/opcodes/mips-dis.c
+++ b/opcodes/mips-dis.c
@@ -845,6 +845,17 @@ is_micromips (Elf_Internal_Ehdr *header)
   return 0;
 }
 
+/* Check if ISA is R6.  */
+
+static inline int
+is_isa_r6 (unsigned long isa)
+{
+  if ((isa & INSN_ISA_MASK) == ISA_MIPS32R6
+      || ((isa & INSN_ISA_MASK) == ISA_MIPS64R6))
+    return 1;
+  return 0;
+}
+
 /* Convert ASE flags from .MIPS.abiflags to internal values.  */
 
 static unsigned long
@@ -2068,10 +2079,10 @@ print_insn_mips (bfd_vma memaddr,
 	      && (word & op->mask) == op->match)
 	    {
 	      /* We always disassemble the jalx instruction, except for MIPS r6.  */
-	      if (!opcode_is_member (op, mips_isa, mips_ase, mips_processor)
-		 && (strcmp (op->name, "jalx")
-		     || (mips_isa & INSN_ISA_MASK) == ISA_MIPS32R6
-		     || (mips_isa & INSN_ISA_MASK) == ISA_MIPS64R6))
+	      if ((!opcode_is_member (op, mips_isa, mips_ase, mips_processor)
+		  && (strcmp (op->name, "jalx") || is_isa_r6 (mips_isa)))
+		  || (is_isa_r6 (op->membership)
+		      && (op->pinfo2 & INSN2_CONVERTED_TO_COMPACT)))
 		continue;
 
 	      /* Figure out instruction type and branch delay information.  */
-- 
2.34.1