[REVIEW ONLY 1/1] RISC-V: Add stub support for the 'Svadu' extension

[Tsukasa OI <research_trasio@irq.a4lg.com>]

From: Tsukasa OI <research_trasio@irq.a4lg.com>

This commit implements support for 'Svadu' extension.  Because it does not
add any instructions or CSRs (but adds bits to existing CSRs), this commit
only adds extension name support and implication to the 'Zicsr' extension.

This is based on the "Hardware Updating of PTE A/D Bits (Svadu)"
specification, version 1.0-rc1 (Frozen):
<https://github.com/riscv/riscv-svadu/releases/tag/v1.0-rc1>

bfd/ChangeLog:

	* elfxx-riscv.c (riscv_implicit_subsets): Add implication from
	'Svadu' to 'Zicsr'.  (riscv_supported_std_s_ext) Add 'Svadu'.
---
 bfd/elfxx-riscv.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/bfd/elfxx-riscv.c b/bfd/elfxx-riscv.c
index cb65024beaff..9189b7da8374 100644
--- a/bfd/elfxx-riscv.c
+++ b/bfd/elfxx-riscv.c
@@ -1189,6 +1189,7 @@ static struct riscv_implicit_subset riscv_implicit_subsets[] =
   {"sscofpmf", "zicsr",		check_implicit_always},
   {"ssstateen", "zicsr",	check_implicit_always},
   {"sstc", "zicsr",		check_implicit_always},
+  {"svadu", "zicsr",		check_implicit_always},
   {NULL, NULL, NULL}
 };
 
@@ -1334,6 +1335,7 @@ static struct riscv_supported_ext riscv_supported_std_s_ext[] =
   {"sscofpmf",		ISA_SPEC_CLASS_DRAFT,		1, 0, 0 },
   {"ssstateen",		ISA_SPEC_CLASS_DRAFT,		1, 0, 0 },
   {"sstc",		ISA_SPEC_CLASS_DRAFT,		1, 0, 0 },
+  {"svadu",		ISA_SPEC_CLASS_DRAFT,		1, 0, 0 },
   {"svinval",		ISA_SPEC_CLASS_DRAFT,		1, 0, 0 },
   {"svnapot",		ISA_SPEC_CLASS_DRAFT,		1, 0, 0 },
   {"svpbmt",		ISA_SPEC_CLASS_DRAFT,		1, 0, 0 },
-- 
2.42.0