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.

8 files changed, 70 insertions, 38 deletions

diff --git a/gdb/aarch64-fbsd-nat.c b/gdb/aarch64-fbsd-nat.c
index 910bf5b..fb7a29b 100644
--- a/gdb/aarch64-fbsd-nat.c
+++ b/gdb/aarch64-fbsd-nat.c
@@ -149,8 +149,9 @@ aarch64_fbsd_nat_target::store_registers (struct regcache *regcache,
 const struct target_desc *
 aarch64_fbsd_nat_target::read_description ()
 {
-  bool tls = have_regset (inferior_ptid, NT_ARM_TLS) != 0;
-  return aarch64_read_description (0, false, false, tls);
+  aarch64_features features;
+  features.tls = have_regset (inferior_ptid, NT_ARM_TLS) != 0;
+  return aarch64_read_description (features);
 }
 
 #ifdef HAVE_DBREG
diff --git a/gdb/aarch64-fbsd-tdep.c b/gdb/aarch64-fbsd-tdep.c
index fdf0795..891546b 100644
--- a/gdb/aarch64-fbsd-tdep.c
+++ b/gdb/aarch64-fbsd-tdep.c
@@ -178,7 +178,10 @@ aarch64_fbsd_core_read_description (struct gdbarch *gdbarch,
 {
   asection *tls = bfd_get_section_by_name (abfd, ".reg-aarch-tls");
 
-  return aarch64_read_description (0, false, false, tls != nullptr);
+  aarch64_features features;
+  features.tls = tls != nullptr;
+
+  return aarch64_read_description (features);
 }
 
 /* Implement the get_thread_local_address gdbarch method.  */
diff --git a/gdb/aarch64-linux-nat.c b/gdb/aarch64-linux-nat.c
index 10b0ca1..9cde72b 100644
--- a/gdb/aarch64-linux-nat.c
+++ b/gdb/aarch64-linux-nat.c
@@ -709,11 +709,13 @@ aarch64_linux_nat_target::read_description ()
   CORE_ADDR hwcap = linux_get_hwcap (this);
   CORE_ADDR hwcap2 = linux_get_hwcap2 (this);
 
-  bool pauth_p = hwcap & AARCH64_HWCAP_PACA;
-  bool mte_p = hwcap2 & HWCAP2_MTE;
+  aarch64_features features;
+  features.vq = aarch64_sve_get_vq (tid);
+  features.pauth = hwcap & AARCH64_HWCAP_PACA;
+  features.mte = hwcap2 & HWCAP2_MTE;
+  features.tls = true;
 
-  return aarch64_read_description (aarch64_sve_get_vq (tid), pauth_p, mte_p,
-				   true);
+  return aarch64_read_description (features);
 }
 
 /* Convert a native/host siginfo object, into/from the siginfo in the
diff --git a/gdb/aarch64-linux-tdep.c b/gdb/aarch64-linux-tdep.c
index dbebcd4..453692d 100644
--- a/gdb/aarch64-linux-tdep.c
+++ b/gdb/aarch64-linux-tdep.c
@@ -779,10 +779,13 @@ aarch64_linux_core_read_description (struct gdbarch *gdbarch,
   CORE_ADDR hwcap = linux_get_hwcap (target);
   CORE_ADDR hwcap2 = linux_get_hwcap2 (target);
 
-  bool pauth_p = hwcap & AARCH64_HWCAP_PACA;
-  bool mte_p = hwcap2 & HWCAP2_MTE;
-  return aarch64_read_description (aarch64_linux_core_read_vq (gdbarch, abfd),
-				   pauth_p, mte_p, tls != nullptr);
+  aarch64_features features;
+  features.vq = aarch64_linux_core_read_vq (gdbarch, abfd);
+  features.pauth = hwcap & AARCH64_HWCAP_PACA;
+  features.mte = hwcap2 & HWCAP2_MTE;
+  features.tls = tls != nullptr;
+
+  return aarch64_read_description (features);
 }
 
 /* Implementation of `gdbarch_stap_is_single_operand', as defined in
diff --git a/gdb/aarch64-tdep.c b/gdb/aarch64-tdep.c
index c3abd3a..e35c083 100644
--- a/gdb/aarch64-tdep.c
+++ b/gdb/aarch64-tdep.c
@@ -52,13 +52,14 @@
 
 #include "opcode/aarch64.h"
 #include <algorithm>
+#include <unordered_map>
 
 /* A Homogeneous Floating-Point or Short-Vector Aggregate may have at most
    four members.  */
 #define HA_MAX_NUM_FLDS		4
 
 /* All possible aarch64 target descriptors.  */
-static target_desc *tdesc_aarch64_list[AARCH64_MAX_SVE_VQ + 1][2/*pauth*/][2 /* mte */][2 /* tls */];
+static std::unordered_map <aarch64_features, target_desc *> tdesc_aarch64_map;
 
 /* The standard register names, and all the valid aliases for them.  */
 static const struct
@@ -3332,18 +3333,18 @@ aarch64_displaced_step_hw_singlestep (struct gdbarch *gdbarch)
    TLS_P indicates the presence of the Thread Local Storage feature.  */
 
 const target_desc *
-aarch64_read_description (uint64_t vq, bool pauth_p, bool mte_p, bool tls_p)
+aarch64_read_description (const aarch64_features &features)
 {
-  if (vq > AARCH64_MAX_SVE_VQ)
-    error (_("VQ is %" PRIu64 ", maximum supported value is %d"), vq,
+  if (features.vq > AARCH64_MAX_SVE_VQ)
+    error (_("VQ is %" PRIu64 ", maximum supported value is %d"), features.vq,
 	   AARCH64_MAX_SVE_VQ);
 
-  struct target_desc *tdesc = tdesc_aarch64_list[vq][pauth_p][mte_p][tls_p];
+  struct target_desc *tdesc = tdesc_aarch64_map[features];
 
   if (tdesc == NULL)
     {
-      tdesc = aarch64_create_target_description (vq, pauth_p, mte_p, tls_p);
-      tdesc_aarch64_list[vq][pauth_p][mte_p][tls_p] = tdesc;
+      tdesc = aarch64_create_target_description (features);
+      tdesc_aarch64_map[features] = tdesc;
     }
 
   return tdesc;
@@ -3450,7 +3451,11 @@ aarch64_gdbarch_init (struct gdbarch_info info, struct gdbarch_list *arches)
      value.  */
   const struct target_desc *tdesc = info.target_desc;
   if (!tdesc_has_registers (tdesc) || vq != aarch64_get_tdesc_vq (tdesc))
-    tdesc = aarch64_read_description (vq, false, false, false);
+    {
+      aarch64_features features;
+      features.vq = vq;
+      tdesc = aarch64_read_description (features);
+    }
   gdb_assert (tdesc);
 
   feature_core = tdesc_find_feature (tdesc,"org.gnu.gdb.aarch64.core");
diff --git a/gdb/aarch64-tdep.h b/gdb/aarch64-tdep.h
index 8efacd5..b85a3d3 100644
--- a/gdb/aarch64-tdep.h
+++ b/gdb/aarch64-tdep.h
@@ -120,8 +120,7 @@ struct aarch64_gdbarch_tdep : gdbarch_tdep
   }
 };
 
-const target_desc *aarch64_read_description (uint64_t vq, bool pauth_p,
-					     bool mte_p, bool tls_p);
+const target_desc *aarch64_read_description (const aarch64_features &features);
 
 extern int aarch64_process_record (struct gdbarch *gdbarch,
 			       struct regcache *regcache, CORE_ADDR addr);
diff --git a/gdb/arch/aarch64.c b/gdb/arch/aarch64.c
index 733a3fd..0f73286 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 8496a03..72ec419 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