RISC-V: Implement Ztso extension

This patch support ZTSO extension. It will turn on the tso flag for elf_flags
once we have enabled Ztso extension.  This is intended to implement v0.1 of
the proposed specification which can be found in Chapter 25 of,
https://github.com/riscv/riscv-isa-manual/releases/download/draft-20220723-10eea63/riscv-spec.pdf.

bfd\ChangeLog:

        * elfnn-riscv.c (_bfd_riscv_elf_merge_private_bfd_data): Set TSO flag.
        * elfxx-riscv.c: Add Ztso's arch.

binutils\ChangeLog:

        * readelf.c (get_machine_flags): Set TSO flag.

gas\ChangeLog:

        * config/tc-riscv.c (riscv_set_tso): Ditto.
        (riscv_set_arch): Ditto.
        * testsuite/gas/riscv/ztso.d: New test.

include\ChangeLog:

        * elf/riscv.h (EF_RISCV_TSO): Ditto.

bfd/elfnn-riscv.c

@@ -3872,6 +3872,9 @@ _bfd_riscv_elf_merge_private_bfd_data (bfd *ibfd, struct bfd_link_info *info)
   /* Allow linking RVC and non-RVC, and keep the RVC flag.  */
   elf_elfheader (obfd)->e_flags |= new_flags & EF_RISCV_RVC;
 
+  /* Allow linking TSO and non-TSO, and keep the TSO flag.  */
+  elf_elfheader (obfd)->e_flags |= new_flags & EF_RISCV_TSO;
+
   return true;
 
  fail:

bfd/elfxx-riscv.c

@@ -1204,6 +1204,7 @@ static struct riscv_supported_ext riscv_supported_std_z_ext[] =
   {"zvl16384b",		ISA_SPEC_CLASS_DRAFT,		1, 0,  0 },
   {"zvl32768b",		ISA_SPEC_CLASS_DRAFT,		1, 0,  0 },
   {"zvl65536b",		ISA_SPEC_CLASS_DRAFT,		1, 0,  0 },
+  {"ztso",		ISA_SPEC_CLASS_DRAFT,		0, 1,  0 },
   {NULL, 0, 0, 0, 0}
 };
 

binutils/readelf.c

@@ -4079,6 +4079,9 @@ get_machine_flags (Filedata * filedata, unsigned e_flags, unsigned e_machine)
 	  if (e_flags & EF_RISCV_RVE)
 	    strcat (buf, ", RVE");
 
+	  if (e_flags & EF_RISCV_TSO)
+	    strcat (buf, ", TSO");
+
 	  switch (e_flags & EF_RISCV_FLOAT_ABI)
 	    {
 	    case EF_RISCV_FLOAT_ABI_SOFT:

gas/config/tc-riscv.c

@@ -257,6 +257,14 @@ riscv_set_rvc (bool rvc_value)
   riscv_opts.rvc = rvc_value;
 }
 
+/* Turn on the tso flag for elf_flags once we have enabled ztso extension.  */
+
+static void
+riscv_set_tso ()
+{
+  elf_flags |= EF_RISCV_TSO;
+}
+
 /* This linked list records all enabled extensions, which are parsed from
    the architecture string.  The architecture string can be set by the
    -march option, the elf architecture attributes, and the --with-arch
@@ -307,6 +315,9 @@ riscv_set_arch (const char *s)
   riscv_set_rvc (false);
   if (riscv_subset_supports (&riscv_rps_as, "c"))
     riscv_set_rvc (true);
+
+  if (riscv_subset_supports (&riscv_rps_as, "ztso"))
+    riscv_set_tso ();
 }
 
 /* Indicate -mabi option is explictly set.  */

gas/testsuite/gas/riscv/ztso.d

@@ -0,0 +1,8 @@
+#as: -march=rv64i_ztso
+#readelf: -h
+#source: empty.s
+
+ELF Header:
+#...
+[ 	]+Flags:[ 	]+0x10, TSO.*
+#...

include/elf/riscv.h

@@ -121,6 +121,9 @@ END_RELOC_NUMBERS (R_RISCV_max)
 /* RISC-V specific values for st_other.  */
 #define STO_RISCV_VARIANT_CC 0x80
 
+/* File uses the TSO model. */
+#define EF_RISCV_TSO 0x0010
+
 /* Additional section types.  */
 #define SHT_RISCV_ATTRIBUTES 0x70000003 /* Section holds attributes.  */