Use aarch64_features to describe register features in target descriptions.

Replace the sve bool member of aarch64_features with a vq member that
holds the vector quotient.  It is zero if SVE is not present.

Add std::hash<> specialization and operator== so that aarch64_features
can be used as a key with std::unordered_map<>.

Change the various functions that create or lookup aarch64 target
descriptions to accept a const aarch64_features object rather than a
growing number of arguments.

Replace the multi-dimension tdesc_aarch64_list arrays used to cache
target descriptions with unordered_maps indexed by aarch64_feature.

2 files changed, 36 insertions, 17 deletions

diff --git a/gdb/arch/aarch64.c b/gdb/arch/aarch64.c
index 733a3fd6d2a..0f73286f145 100644
--- a/gdb/arch/aarch64.c
+++ b/gdb/arch/aarch64.c
@@ -29,8 +29,7 @@
 /* See arch/aarch64.h.  */
 
 target_desc *
-aarch64_create_target_description (uint64_t vq, bool pauth_p, bool mte_p,
-				   bool tls_p)
+aarch64_create_target_description (const aarch64_features &features)
 {
   target_desc_up tdesc = allocate_target_description ();
 
@@ -42,19 +41,19 @@ aarch64_create_target_description (uint64_t vq, bool pauth_p, bool mte_p,
 
   regnum = create_feature_aarch64_core (tdesc.get (), regnum);
 
-  if (vq == 0)
+  if (features.vq == 0)
     regnum = create_feature_aarch64_fpu (tdesc.get (), regnum);
   else
-    regnum = create_feature_aarch64_sve (tdesc.get (), regnum, vq);
+    regnum = create_feature_aarch64_sve (tdesc.get (), regnum, features.vq);
 
-  if (pauth_p)
+  if (features.pauth)
     regnum = create_feature_aarch64_pauth (tdesc.get (), regnum);
 
   /* Memory tagging extension registers.  */
-  if (mte_p)
+  if (features.mte)
     regnum = create_feature_aarch64_mte (tdesc.get (), regnum);
 
-  if (tls_p)
+  if (features.tls)
     regnum = create_feature_aarch64_tls (tdesc.get (), regnum);
 
   return tdesc.release ();
diff --git a/gdb/arch/aarch64.h b/gdb/arch/aarch64.h
index 8496a0341f7..72ec4193eba 100644
--- a/gdb/arch/aarch64.h
+++ b/gdb/arch/aarch64.h
@@ -26,23 +26,43 @@
    used to select register sets.  */
 struct aarch64_features
 {
-  bool sve = false;
+  /* A non zero VQ value indicates both the presence of SVE and the
+     Vector Quotient - the number of 128bit chunks in an SVE Z
+     register.  */
+  uint64_t vq = 0;
+
   bool pauth = false;
   bool mte = false;
   bool tls = false;
 };
 
-/* Create the aarch64 target description.  A non zero VQ value indicates both
-   the presence of SVE and the Vector Quotient - the number of 128bit chunks in
-   an SVE Z register.  HAS_PAUTH_P indicates the presence of the PAUTH
-   feature.
-
-   MTE_P indicates the presence of the Memory Tagging Extension feature.
+inline bool operator==(const aarch64_features &lhs, const aarch64_features &rhs)
+{
+  return lhs.vq == rhs.vq
+    && lhs.pauth == rhs.pauth
+    && lhs.mte == rhs.mte
+    && lhs.tls == rhs.tls;
+}
+
+template<>
+struct std::hash<aarch64_features>
+{
+  std::size_t operator()(const aarch64_features &features) const noexcept
+  {
+    std::size_t h;
+
+    h = features.vq;
+    h = h << 1 | features.pauth;
+    h = h << 1 | features.mte;
+    h = h << 1 | features.tls;
+    return h;
+  }
+};
 
-   TLS_P indicates the presence of the Thread Local Storage feature.  */
+/* Create the aarch64 target description.  */
 
-target_desc *aarch64_create_target_description (uint64_t vq, bool has_pauth_p,
-						bool mte_p, bool tls_p);
+target_desc *
+  aarch64_create_target_description (const aarch64_features &features);
 
 /* Register numbers of various important registers.
    Note that on SVE, the Z registers reuse the V register numbers and the V