[PATCH 1/1] RISC-V: Add --march=help

[Hau Hsu]

Use --march=help to print all supported extensions and versions.

Here is part of the output of `as -march=help`:
All available -march extensions for RISC-V:
        e                                       1.9
        i                                       2.1, 2.0
        m                                       2.0
        a                                       2.1, 2.0
        f                                       2.2, 2.0
        d                                       2.2, 2.0
        q                                       2.2, 2.0
        c                                       2.0
        v                                       1.0
        h                                       1.0
        zicbom                                  1.0
        zicbop                                  1.0

This patch assumes that the supported extensions with the same versions
are listed together.

For example
static struct riscv_supported_ext riscv_supported_std_ext[] =
{
  ...
  {"i",         ISA_SPEC_CLASS_20191213,        2, 1, 0 },
  {"i",         ISA_SPEC_CLASS_20190608,        2, 1, 0 },
  {"i",         ISA_SPEC_CLASS_2P2,             2, 0, 0 },
  ...
};

For the "i" extension, 2.1.0 with different spec class are listed together.
This patch records the previous printed extension and version.  If the
current extension and version are the same as the previous one, skip
printing.
---
 bfd/ChangeLog         |  9 ++++++
 bfd/elfxx-riscv.c     | 64 +++++++++++++++++++++++++++++++++++++++++++
 bfd/elfxx-riscv.h     |  3 ++
 gas/ChangeLog         |  4 +++
 gas/config/tc-riscv.c |  6 ++++
 5 files changed, 86 insertions(+)

diff --git a/bfd/ChangeLog b/bfd/ChangeLog
index 97d0c585a56..66572927998 100644
--- a/bfd/ChangeLog
+++ b/bfd/ChangeLog
@@ -1,3 +1,12 @@
+2024-02-21 Hau Hsu  <hau.hsu@sifive.com>
+
+	* elfxx-riscv.h (riscv_print_extensions): New declaration.
+	* elfxx-riscv.c (riscv_print_extensions): New function. Print
+	available extensions and versions.
+	(riscv_same_extension_version): New function.
+	(riscv_same_extension_diff_version): New function.
+	(riscv_valid_ext): New function.
+
 2024-01-15  Nick Clifton  <nickc@redhat.com>
 
 	* 2.42 branch point.
diff --git a/bfd/elfxx-riscv.c b/bfd/elfxx-riscv.c
index 9a121b47121..108e26d5b30 100644
--- a/bfd/elfxx-riscv.c
+++ b/bfd/elfxx-riscv.c
@@ -2051,6 +2051,70 @@ riscv_set_default_arch (riscv_parse_subset_t *rps)
     }
 }
 
+static
+bool riscv_same_extension_version(
+  const struct riscv_supported_ext* ext1,
+  const struct riscv_supported_ext* ext2)
+{
+  return (strcmp(ext1->name, ext2->name) == 0
+          && ext1->major_version == ext2->major_version
+          && ext1->minor_version == ext2->minor_version);
+}
+
+static
+bool riscv_same_extension_diff_version(
+  const struct riscv_supported_ext* ext1,
+  const struct riscv_supported_ext* ext2)
+{
+  return (strcmp(ext1->name, ext2->name) == 0
+          && !(ext1->major_version == ext2->major_version
+               && ext1->minor_version == ext2->minor_version));
+}
+
+static
+bool riscv_valid_ext(const struct riscv_supported_ext *ext)
+{
+  return (ext->isa_spec_class != ISA_SPEC_CLASS_NONE
+          && ext->major_version != RISCV_UNKNOWN_VERSION
+          && ext->minor_version != RISCV_UNKNOWN_VERSION);
+}
+
+void riscv_print_extensions(void)
+{
+  /* Record the previous pritned extension.
+     Print the current one if they are not the same.  */
+  const struct riscv_supported_ext *cur = NULL, *prev = NULL;
+
+  int i, j;
+  printf ("All available -march extensions for RISC-V:");
+  for (i = 0; riscv_all_supported_ext[i] != NULL; i++)
+    {
+      const struct riscv_supported_ext *exts = riscv_all_supported_ext[i];
+      prev = NULL;
+      for (j = 0; exts[j].name != NULL; j++)
+        {
+          cur = &exts[j];
+          if (!riscv_valid_ext (cur))
+            continue;
+
+          if (prev && riscv_same_extension_version (prev, cur))
+            continue;
+
+          if (!prev || !riscv_same_extension_diff_version (prev, cur))
+            {
+              printf("\n\t%-40s%d.%d", cur->name, cur->major_version, cur->minor_version);
+              prev = &exts[j];
+            }
+          else
+            {
+              printf(", %d.%d", cur->major_version, cur->minor_version);
+              prev = &exts[j];
+            }
+        }
+    }
+  printf ("\n");
+}
+
 /* Function for parsing ISA string.
 
    Return Value:
diff --git a/bfd/elfxx-riscv.h b/bfd/elfxx-riscv.h
index ae4cbee7bc3..f3710ec7fab 100644
--- a/bfd/elfxx-riscv.h
+++ b/bfd/elfxx-riscv.h
@@ -121,6 +121,9 @@ riscv_multi_subset_supports (riscv_parse_subset_t *, enum riscv_insn_class);
 extern const char *
 riscv_multi_subset_supports_ext (riscv_parse_subset_t *, enum riscv_insn_class);
 
+extern void
+riscv_print_extensions(void);
+
 extern void
 bfd_elf32_riscv_set_data_segment_info (struct bfd_link_info *, int *);
 extern void
diff --git a/gas/ChangeLog b/gas/ChangeLog
index 88e61083c44..cebd9d94ae5 100644
--- a/gas/ChangeLog
+++ b/gas/ChangeLog
@@ -1,3 +1,7 @@
+2024-02-21 Hau Hsu  <hau.hsu@sifive.com>
+	* gas/config/tc-riscv.c (md_parse_option): Parse 'help' keyword in
+	march to print available extensions and versions.
+
 2024-02-19 Will Hawkins  <hawkinsw@obs.cr>
 
 	* config/tc-bpf.c (parse_expression): Change switch to if so that
diff --git a/gas/config/tc-riscv.c b/gas/config/tc-riscv.c
index a4161420128..e0910f59157 100644
--- a/gas/config/tc-riscv.c
+++ b/gas/config/tc-riscv.c
@@ -4034,6 +4034,12 @@ md_parse_option (int c, const char *arg)
   switch (c)
     {
     case OPTION_MARCH:
+      /* List all avaiable archs. */
+      if (strcmp (arg, "help") == 0)
+        {
+          riscv_print_extensions();
+          exit (EXIT_SUCCESS);
+        }
       default_arch_with_ext = arg;
       break;
 
-- 
2.31.1