[PATCH 7/8] gdb/aarch64: Factor out most of the thread_architecture method

[Thiago Jung Bauermann]

The same logic will be used by a subsequent commit when remotely debugging
an aarch64-linux target.

The code isn't changed, just moved around.
---
 gdb/aarch64-linux-nat.c | 25 +------------------------
 gdb/aarch64-tdep.c      | 34 ++++++++++++++++++++++++++++++++++
 gdb/aarch64-tdep.h      |  2 ++
 3 files changed, 37 insertions(+), 24 deletions(-)

diff --git a/gdb/aarch64-linux-nat.c b/gdb/aarch64-linux-nat.c
index 633cbc08796c..ff4c69f6af7d 100644
--- a/gdb/aarch64-linux-nat.c
+++ b/gdb/aarch64-linux-nat.c
@@ -891,36 +891,13 @@ aarch64_linux_nat_target::thread_architecture (ptid_t ptid)
   inferior *inf = find_inferior_ptid (this, ptid);
   gdb_assert (inf != NULL);
 
-  /* If this is a 32-bit architecture, then this is ARM, not AArch64.
-     There's no SVE vectors here, so just return the inferior
-     architecture.  */
-  if (gdbarch_bfd_arch_info (inf->gdbarch)->bits_per_word == 32)
-    return inf->gdbarch;
-
-  /* Only return it if the current vector length matches the one in the tdep.  */
-  aarch64_gdbarch_tdep *tdep
-    = gdbarch_tdep<aarch64_gdbarch_tdep> (inf->gdbarch);
   int vq = aarch64_sve_get_vq (ptid.lwp ());
 
   /* If ptrace fails we can't determine vq, but the thread_architecture method
      always succeeds so all we can do here is assert that vq is valid.  */
   gdb_assert (vq >= 0);
-  if (vq == tdep->vq)
-    return inf->gdbarch;
-
-  /* We reach here if the vector length for the thread is different from its
-     value at process start.  Lookup gdbarch via info (potentially creating a
-     new one) by using a target description that corresponds to the new vq value
-     and the current architecture features.  */
-
-  const struct target_desc *tdesc = gdbarch_target_desc (inf->gdbarch);
-  aarch64_features features = aarch64_features_from_target_desc (tdesc);
-  features.vq = vq;
 
-  struct gdbarch_info info;
-  info.bfd_arch_info = bfd_lookup_arch (bfd_arch_aarch64, bfd_mach_aarch64);
-  info.target_desc = aarch64_read_description (features);
-  return gdbarch_find_by_info (info);
+  return aarch64_update_gdbarch (inf->gdbarch, vq);
 }
 
 /* Implement the "supports_memory_tagging" target_ops method.  */
diff --git a/gdb/aarch64-tdep.c b/gdb/aarch64-tdep.c
index 7229b53838e8..18c2b1ec1523 100644
--- a/gdb/aarch64-tdep.c
+++ b/gdb/aarch64-tdep.c
@@ -3420,6 +3420,40 @@ aarch64_cannot_store_register (struct gdbarch *gdbarch, int regnum)
 	  || regnum == AARCH64_PAUTH_CMASK_REGNUM (tdep->pauth_reg_base));
 }
 
+/* Helper function for the "thread_architecture" target_ops method.
+
+   Returns a new gdbarch that is equivalent to the given gdbarch, but with SVE
+   registers reflecting the given vq value.  */
+
+struct gdbarch *
+aarch64_update_gdbarch (struct gdbarch *gdbarch, uint64_t vq)
+{
+  /* If this is a 32-bit architecture, then this is ARM, not AArch64.
+     There's no SVE vectors here, so just return the inferior
+     architecture.  */
+  if (gdbarch_bfd_arch_info (gdbarch)->bits_per_word == 32)
+    return gdbarch;
+
+  /* Only return it if the current vector length matches the one in the tdep.  */
+  aarch64_gdbarch_tdep *tdep = gdbarch_tdep<aarch64_gdbarch_tdep> (gdbarch);
+  if (vq == tdep->vq)
+    return gdbarch;
+
+  /* We reach here if the vector length for the thread is different from its
+     value at process start.  Lookup gdbarch via info (potentially creating a
+     new one) by using a target description that corresponds to the new vq
+     value and the current architecture features.  */
+
+  const struct target_desc *tdesc = gdbarch_target_desc (gdbarch);
+  aarch64_features features = aarch64_features_from_target_desc (tdesc);
+  features.vq = vq;
+
+  struct gdbarch_info info;
+  info.bfd_arch_info = bfd_lookup_arch (bfd_arch_aarch64, bfd_mach_aarch64);
+  info.target_desc = aarch64_create_target_description (features);
+  return gdbarch_find_by_info (info);
+}
+
 /* Implement the stack_frame_destroyed_p gdbarch method.  */
 
 static int
diff --git a/gdb/aarch64-tdep.h b/gdb/aarch64-tdep.h
index d8513023c376..3d78515e167f 100644
--- a/gdb/aarch64-tdep.h
+++ b/gdb/aarch64-tdep.h
@@ -139,4 +139,6 @@ void aarch64_displaced_step_fixup (struct gdbarch *gdbarch,
 
 bool aarch64_displaced_step_hw_singlestep (struct gdbarch *gdbarch);
 
+struct gdbarch *aarch64_update_gdbarch (struct gdbarch *gdbarch, uint64_t vq);
+
 #endif /* aarch64-tdep.h */