RISC-V: Imply 'Zicsr' from some privileged extensions

As 'H', 'Smstateen', 'Sscofpmf' and 'Sstc' define their own CSRs,
they implicitly require 'Zicsr' in the process.

This commit adds such implicications.

gas/ChangeLog:

	* testsuite/gas/riscv/march-imply-h.d: New test, at least for 'H'.

bfd/ChangeLog:

	* elfxx-riscv.c (riscv_implicit_subsets): Add 'Zicsr' implicications
	for privileged extensions 'H', 'Smstateen', 'Sscofpmf' and 'Sstc'.

bfd/elfxx-riscv.c

@@ -1047,6 +1047,7 @@ static struct riscv_implicit_subset riscv_implicit_subsets[] =
   {"g", "d",		check_implicit_always},
   {"g", "zicsr",	check_implicit_always},
   {"g", "zifencei",	check_implicit_always},
+  {"h", "zicsr",	check_implicit_always},
   {"q", "d",		check_implicit_always},
   {"v", "d",		check_implicit_always},
   {"v", "zve64d",	check_implicit_always},
@@ -1098,6 +1099,9 @@ static struct riscv_implicit_subset riscv_implicit_subsets[] =
   {"zks", "zbkx",	check_implicit_always},
   {"zks", "zksed",	check_implicit_always},
   {"zks", "zksh",	check_implicit_always},
+  {"smstateen", "zicsr",	check_implicit_always},
+  {"sscofpmf", "zicsr",		check_implicit_always},
+  {"sstc", "zicsr",		check_implicit_always},
   {NULL, NULL, NULL}
 };
 

gas/testsuite/gas/riscv/march-imply-h.d

@@ -0,0 +1,6 @@
+#as: -march=rv32ih -march-attr -misa-spec=20191213 -mpriv-spec=1.12
+#readelf: -A
+#source: empty.s
+Attribute Section: riscv
+File Attributes
+  Tag_RISCV_arch: "rv32i2p1_h1p0_zicsr2p0"