[PATCH 10/13] RISC-V: Add support for literal instruction arguments

[Christoph Muellner]

From: Christoph Müllner <christoph.muellner@vrull.eu>

This patch introduces support for arbitrary literal instruction
arguments, that are not encoded in the opcode.

A typical use case for this feature would be an instruction that
applies an implicit shift by a constant value on an immediate
(that is a real operand). With this patch it is possible to make
this shift visible in the dissasembly and support such artificial
parameter as part of the asssembly code.

Signed-off-by: Christoph Müllner <christoph.muellner@vrull.eu>
---
 gas/config/tc-riscv.c | 14 ++++++++++++++
 opcodes/riscv-dis.c   | 10 ++++++++++
 2 files changed, 24 insertions(+)

diff --git a/gas/config/tc-riscv.c b/gas/config/tc-riscv.c
index 7f0db9fdb80..e89e9f492d9 100644
--- a/gas/config/tc-riscv.c
+++ b/gas/config/tc-riscv.c
@@ -1258,6 +1258,10 @@ validate_riscv_insn (const struct riscv_opcode *opc, int length)
 		goto unknown_validate_operand;
 	    }
 	  break;
+	case 'L': /* Literal.  */
+	  oparg += strcspn(oparg, ",") - 1;
+	  break;
+
 	case 'X': /* Integer immediate.  */
 	  {
 	    size_t n;
@@ -3295,6 +3299,16 @@ riscv_ip (char *str, struct riscv_cl_insn *ip, expressionS *imm_expr,
 	      asarg = expr_end;
 	      continue;
 
+	    case 'L': /* Literal.  */
+	      {
+		size_t n = strcspn (++oparg, ",");
+		if (strncmp (oparg, asarg, n))
+		  as_bad (_("unexpected literal (%s)"), asarg);
+		oparg += n - 1;
+		asarg += n;
+	      }
+	      continue;
+
 	    case 'X': /* Integer immediate.  */
 	      {
 		size_t n;
diff --git a/opcodes/riscv-dis.c b/opcodes/riscv-dis.c
index c6ddea16dda..a4b030aa415 100644
--- a/opcodes/riscv-dis.c
+++ b/opcodes/riscv-dis.c
@@ -563,6 +563,16 @@ print_insn_args (const char *oparg, insn_t l, bfd_vma pc, disassemble_info *info
 	  print (info->stream, dis_style_text, "%d", rs1);
 	  break;
 
+	case 'L': /* Literal. */
+	  oparg++;
+	  while (*oparg && *oparg != ',')
+	    {
+	      print (info->stream, dis_style_text, "%c", *oparg);
+	      oparg++;
+	    }
+	  oparg--;
+	  break;
+
 	case 'X': /* Integer immediate.  */
 	  {
 	    size_t n;
-- 
2.37.2