RISC-V: Disable the CSR checking by default.

Add new .option `csr-check/no-csr-check` and GAS option `-mcsr-check
/-mno-csr-check` to enbale/disable the CSR checking.  Disable the CSR
checking by default.

	gas/
	* config/tc-riscv.c: Add new .option and GAS options to enbale/disable
	the CSR checking.  We disable the CSR checking by default.
	(reg_lookup_internal): Check the `riscv_opts.csr_check`
	before we doing the CSR checking.

	* doc/c-riscv.texi: Add description for the new .option and assembler
	options.

	* testsuite/gas/riscv/priv-reg-fail-fext.d: Add `-mcsr-check` to enable
	the CSR checking.
	* testsuite/gas/riscv/priv-reg-fail-rv32-only.d: Likewise.

1 files changed, 21 insertions, 1 deletions

diff --git a/gas/config/tc-riscv.c b/gas/config/tc-riscv.c
index 2f95d41..5972f02 100644
--- a/gas/config/tc-riscv.c
+++ b/gas/config/tc-riscv.c
@@ -83,6 +83,7 @@ struct riscv_set_options
   int rve; /* Generate RVE code.  */
   int relax; /* Emit relocs the linker is allowed to relax.  */
   int arch_attr; /* Emit arch attribute.  */
+  int csr_check; /* Enable the CSR checking.  */
 };
 
 static struct riscv_set_options riscv_opts =
@@ -92,6 +93,7 @@ static struct riscv_set_options riscv_opts =
   0,	/* rve */
   1,	/* relax */
   DEFAULT_RISCV_ATTR, /* arch_attr */
+  0.	/* csr_check */
 };
 
 static void
@@ -572,7 +574,9 @@ reg_lookup_internal (const char *s, enum reg_class class)
   if (riscv_opts.rve && class == RCLASS_GPR && DECODE_REG_NUM (r) > 15)
     return -1;
 
-  if (class == RCLASS_CSR && !reg_csr_lookup_internal (s))
+  if (class == RCLASS_CSR
+      && riscv_opts.csr_check
+      && !reg_csr_lookup_internal (s))
     return -1;
 
   return DECODE_REG_NUM (r);
@@ -2272,6 +2276,8 @@ enum options
   OPTION_NO_RELAX,
   OPTION_ARCH_ATTR,
   OPTION_NO_ARCH_ATTR,
+  OPTION_CSR_CHECK,
+  OPTION_NO_CSR_CHECK,
   OPTION_END_OF_ENUM
 };
 
@@ -2286,6 +2292,8 @@ struct option md_longopts[] =
   {"mno-relax", no_argument, NULL, OPTION_NO_RELAX},
   {"march-attr", no_argument, NULL, OPTION_ARCH_ATTR},
   {"mno-arch-attr", no_argument, NULL, OPTION_NO_ARCH_ATTR},
+  {"mcsr-check", no_argument, NULL, OPTION_CSR_CHECK},
+  {"mno-csr-check", no_argument, NULL, OPTION_NO_CSR_CHECK},
 
   {NULL, no_argument, NULL, 0}
 };
@@ -2364,6 +2372,14 @@ md_parse_option (int c, const char *arg)
       riscv_opts.arch_attr = FALSE;
       break;
 
+    case OPTION_CSR_CHECK:
+      riscv_opts.csr_check = TRUE;
+      break;
+
+    case OPTION_NO_CSR_CHECK:
+      riscv_opts.csr_check = FALSE;
+      break;
+
     default:
       return 0;
     }
@@ -2756,6 +2772,10 @@ s_riscv_option (int x ATTRIBUTE_UNUSED)
     riscv_opts.relax = TRUE;
   else if (strcmp (name, "norelax") == 0)
     riscv_opts.relax = FALSE;
+  else if (strcmp (name, "csr-check") == 0)
+    riscv_opts.csr_check = TRUE;
+  else if (strcmp (name, "no-csr-check") == 0)
+    riscv_opts.csr_check = FALSE;
   else if (strcmp (name, "push") == 0)
     {
       struct riscv_option_stack *s;