[PATCH 01/12] gdb: add supports_arch_info callback to gdbarch_register

[Simon Marchi <simon.marchi@efficios.com>]

From: Lancelot SIX <lancelot.six@amd.com>

In the ROCm GDB port, there are some amdgcn architectures known by BFD
that we don't actually support in GDB.  We don't want
gdbarch_printable_names to return these architectures.

gdbarch_printable_names is used for a few things:

 - completion of the "set architecture" command
 - the gdb.architecture_names function in Python
 - foreach-arch selftests

Add an optional callback to gdbarch_register that is a predicate
indicating whether the gdbarch supports the given bfd_arch_info.  by
default, it is nullptr, meaning that the gdbarch accepts all "mach"s for
that architecture known by BFD.

Change-Id: I712f94351b0b34ed1f42e5cf7fc7ba051315d860
Co-Authored-By: Simon Marchi <simon.marchi@efficios.com>
---
 gdb/arch-utils.c | 9 +++++++--
 gdb/gdbarch.h    | 4 +++-
 2 files changed, 10 insertions(+), 3 deletions(-)

diff --git a/gdb/arch-utils.c b/gdb/arch-utils.c
index 60ffdc5e16a..dbe78647d5e 100644
--- a/gdb/arch-utils.c
+++ b/gdb/arch-utils.c
@@ -1211,6 +1211,7 @@ struct gdbarch_registration
   enum bfd_architecture bfd_architecture;
   gdbarch_init_ftype *init;
   gdbarch_dump_tdep_ftype *dump_tdep;
+  gdbarch_supports_arch_info_ftype *supports_arch_info;
   struct gdbarch_list *arches;
   struct gdbarch_registration *next;
 };
@@ -1234,7 +1235,9 @@ gdbarch_printable_names ()
 	internal_error (_("gdbarch_architecture_names: multi-arch unknown"));
       do
 	{
-	  arches.push_back (ap->printable_name);
+	  if (rego->supports_arch_info == nullptr
+	      || rego->supports_arch_info (ap))
+	    arches.push_back (ap->printable_name);
 	  ap = ap->next;
 	}
       while (ap != NULL);
@@ -1247,7 +1250,8 @@ gdbarch_printable_names ()
 void
 gdbarch_register (enum bfd_architecture bfd_architecture,
 		  gdbarch_init_ftype *init,
-		  gdbarch_dump_tdep_ftype *dump_tdep)
+		  gdbarch_dump_tdep_ftype *dump_tdep,
+		  gdbarch_supports_arch_info_ftype *supports_arch_info)
 {
   struct gdbarch_registration **curr;
   const struct bfd_arch_info *bfd_arch_info;
@@ -1280,6 +1284,7 @@ gdbarch_register (enum bfd_architecture bfd_architecture,
   (*curr)->bfd_architecture = bfd_architecture;
   (*curr)->init = init;
   (*curr)->dump_tdep = dump_tdep;
+  (*curr)->supports_arch_info = supports_arch_info;
   (*curr)->arches = NULL;
   (*curr)->next = NULL;
 }
diff --git a/gdb/gdbarch.h b/gdb/gdbarch.h
index f2ba5f97765..aea6c4335d9 100644
--- a/gdb/gdbarch.h
+++ b/gdb/gdbarch.h
@@ -268,10 +268,12 @@ struct gdbarch_info
 
 typedef struct gdbarch *(gdbarch_init_ftype) (struct gdbarch_info info, struct gdbarch_list *arches);
 typedef void (gdbarch_dump_tdep_ftype) (struct gdbarch *gdbarch, struct ui_file *file);
+typedef bool (gdbarch_supports_arch_info_ftype) (const struct bfd_arch_info *);
 
 extern void gdbarch_register (enum bfd_architecture architecture,
 			      gdbarch_init_ftype *init,
-			      gdbarch_dump_tdep_ftype *dump_tdep = nullptr);
+			      gdbarch_dump_tdep_ftype *dump_tdep = nullptr,
+			      gdbarch_supports_arch_info_ftype *supports_arch_info = nullptr);
 
 
 /* Return a vector of the valid architecture names.  Since architectures are
-- 
2.38.1