[PATCH v2] RISC-V: Add --march=help

[Hau Hsu <hau.hsu@sifive.com>]

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

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 "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.

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

Signed-off-by: Hau Hsu <hau.hsu@sifive.com>
---
 bfd/ChangeLog     |  9 ++++++
 bfd/elfxx-riscv.c | 72 +++++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 81 insertions(+)

diff --git a/bfd/ChangeLog b/bfd/ChangeLog
index 97d0c585a56..0807a2e0bcb 100644
--- a/bfd/ChangeLog
+++ b/bfd/ChangeLog
@@ -1,3 +1,12 @@
+2024-01-17 Hau Hsu  <hau.hsu@sifive.com>
+
+	* elfxx-riscv.c (riscv_parse_subset): Parse 'help' keyword to print
+	  available extension and versions.
+	(riscv_print_extensions): New function.
+	(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..bb394a589b1 100644
--- a/bfd/elfxx-riscv.c
+++ b/bfd/elfxx-riscv.c
@@ -2051,6 +2051,71 @@ 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);
+}
+
+static
+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:
@@ -2089,6 +2154,13 @@ riscv_parse_subset (riscv_parse_subset_t *rps,
     }
 
   p = arch;
+  /* List all avaiable archs. */
+  if (strcmp (p, "help") == 0)
+    {
+      riscv_print_extensions();
+      exit (EXIT_SUCCESS);
+    }
+
   if (startswith (p, "rv32"))
     {
       *rps->xlen = 32;
-- 
2.37.1