[PATCH v2 10/11] RISC-V: Add support for literal instruction arguments

[Christoph Muellner <christoph.muellner@vrull.eu>]

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 | 10 ++++++++++
 opcodes/riscv-dis.c   |  9 +++++++++
 2 files changed, 19 insertions(+)

diff --git a/gas/config/tc-riscv.c b/gas/config/tc-riscv.c
index 694d079863d..c8bee193730 100644
--- a/gas/config/tc-riscv.c
+++ b/gas/config/tc-riscv.c
@@ -1265,6 +1265,9 @@ validate_riscv_insn (const struct riscv_opcode *opc, int length)
 
 	    switch (*++oparg)
 	      {
+		case 'l': /* Literal.  */
+		  oparg += strcspn(oparg, ",") - 1;
+		  break;
 		case 's': /* 'XsN@S' ... N-bit signed immediate at bit S.  */
 		  goto use_imm;
 		case 'u': /* 'XuN@S' ... N-bit unsigned immediate at bit S.  */
@@ -3300,6 +3303,13 @@ riscv_ip (char *str, struct riscv_cl_insn *ip, expressionS *imm_expr,
 
 		switch (*++oparg)
 		  {
+		    case 'l': /* Literal.  */
+		      n = strcspn (++oparg, ",");
+		      if (strncmp (oparg, asarg, n))
+			as_bad (_("unexpected literal (%s)"), asarg);
+		      oparg += n - 1;
+		      asarg += n;
+		      continue;
 		    case 's': /* 'XsN@S' ... N-bit signed immediate at bit S.  */
 		      sign = true;
 		      goto parse_imm;
diff --git a/opcodes/riscv-dis.c b/opcodes/riscv-dis.c
index c6ddea16dda..bc8588522d5 100644
--- a/opcodes/riscv-dis.c
+++ b/opcodes/riscv-dis.c
@@ -571,6 +571,15 @@ print_insn_args (const char *oparg, insn_t l, bfd_vma pc, disassemble_info *info
 
 	    switch (*++oparg)
 	      {
+		case 'l': /* Literal.  */
+		  oparg++;
+		  while (*oparg && *oparg != ',')
+		    {
+		      print (info->stream, dis_style_text, "%c", *oparg);
+		      oparg++;
+		    }
+		  oparg--;
+		  break;
 		case 's': /* 'XsN@S' ... N-bit signed immediate at bit S.  */
 		  sign = true;
 		  goto print_imm;
-- 
2.37.2