gdb: LoongArch: Add initial target description support

This commit adds initial target description support for LoongArch.

Signed-off-by: Zhensong Liu <liuzhensong@loongson.cn>
Signed-off-by: Qing zhang <zhangqing@loongson.cn>
Signed-off-by: Youling Tang <tangyouling@loongson.cn>
Signed-off-by: Tiezhu Yang <yangtiezhu@loongson.cn>

2 files changed, 161 insertions, 0 deletions

diff --git a/gdb/arch/loongarch.c b/gdb/arch/loongarch.c
new file mode 100644
index 00000000000..934f6e489c5
--- /dev/null
+++ b/gdb/arch/loongarch.c
@@ -0,0 +1,88 @@
+/* Copyright (C) 2022 Free Software Foundation, Inc.
+
+   This file is part of GDB.
+
+   This program is free software; you can redistribute it and/or modify
+   it under the terms of the GNU General Public License as published by
+   the Free Software Foundation; either version 3 of the License, or
+   (at your option) any later version.
+
+   This program is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
+
+#include "gdbsupport/common-defs.h"
+#include "loongarch.h"
+#include <stdlib.h>
+#include <unordered_map>
+
+/* Target description features.  */
+
+#include "../features/loongarch/base32.c"
+#include "../features/loongarch/base64.c"
+
+static target_desc_up
+loongarch_create_target_description (const struct loongarch_gdbarch_features features)
+{
+  /* Now we should create a new target description.  */
+  target_desc_up tdesc = allocate_target_description ();
+
+  std::string arch_name = "loongarch";
+
+  if (features.xlen == 4)
+    arch_name.append ("32");
+  else if (features.xlen == 8)
+    arch_name.append ("64");
+
+  set_tdesc_architecture (tdesc.get (), arch_name.c_str ());
+
+  long regnum = 0;
+
+  /* For now we only support creating 32-bit or 64-bit x-registers.  */
+  if (features.xlen == 4)
+    regnum = create_feature_loongarch_base32 (tdesc.get (), regnum);
+  else if (features.xlen == 8)
+    regnum = create_feature_loongarch_base64 (tdesc.get (), regnum);
+
+  return tdesc;
+}
+
+/* Wrapper used by std::unordered_map to generate hash for feature set.  */
+struct loongarch_gdbarch_features_hasher
+{
+  std::size_t
+  operator() (const loongarch_gdbarch_features &features) const noexcept
+  {
+    return features.hash ();
+  }
+};
+
+/* Cache of previously seen target descriptions, indexed by the feature set
+   that created them.  */
+static std::unordered_map<loongarch_gdbarch_features,
+			  const target_desc_up,
+			  loongarch_gdbarch_features_hasher> loongarch_tdesc_cache;
+
+const target_desc *
+loongarch_lookup_target_description (const struct loongarch_gdbarch_features features)
+{
+  /* Lookup in the cache.  If we find it then return the pointer out of
+     the target_desc_up (which is a unique_ptr).  This is safe as the
+     loongarch_tdesc_cache will exist until GDB exits.  */
+  const auto it = loongarch_tdesc_cache.find (features);
+  if (it != loongarch_tdesc_cache.end ())
+    return it->second.get ();
+
+  target_desc_up tdesc (loongarch_create_target_description (features));
+
+  /* Add to the cache, and return a pointer borrowed from the
+     target_desc_up.  This is safe as the cache (and the pointers
+     contained within it) are not deleted until GDB exits.  */
+  target_desc *ptr = tdesc.get ();
+  loongarch_tdesc_cache.emplace (features, std::move (tdesc));
+  return ptr;
+}
diff --git a/gdb/arch/loongarch.h b/gdb/arch/loongarch.h
new file mode 100644
index 00000000000..9e10df967d1
--- /dev/null
+++ b/gdb/arch/loongarch.h
@@ -0,0 +1,73 @@
+/* Common target-dependent functionality for LoongArch
+
+   Copyright (C) 2022 Free Software Foundation, Inc.
+
+   This file is part of GDB.
+
+   This program is free software; you can redistribute it and/or modify
+   it under the terms of the GNU General Public License as published by
+   the Free Software Foundation; either version 3 of the License, or
+   (at your option) any later version.
+
+   This program is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
+
+#ifndef ARCH_LOONGARCH_H
+#define ARCH_LOONGARCH_H
+
+#include "gdbsupport/tdesc.h"
+
+/* The set of LoongArch architectural features that we track that impact how
+   we configure the actual gdbarch instance.  We hold one of these in the
+   gdbarch_tdep structure, and use it to distinguish between different
+   LoongArch gdbarch instances.
+
+   The information in here ideally comes from the target description,
+   however, if the target doesn't provide a target description then we will
+   create a default target description by first populating one of these
+   based on what we know about the binary being executed, and using that to
+   drive default target description creation.  */
+
+struct loongarch_gdbarch_features
+{
+  /* The size of the x-registers in bytes.  This is either 4 (loongarch32)
+     or 8 (loongarch64).  No other value is valid.  Initialise to the invalid
+     0 value so we can spot if one of these is used uninitialised.  */
+  int xlen = 0;
+
+  /* Equality operator.  */
+  bool operator== (const struct loongarch_gdbarch_features &rhs) const
+  {
+    return (xlen == rhs.xlen);
+  }
+
+  /* Inequality operator.  */
+  bool operator!= (const struct loongarch_gdbarch_features &rhs) const
+  {
+    return !((*this) == rhs);
+  }
+
+  /* Used by std::unordered_map to hash feature sets.  */
+  std::size_t hash () const noexcept
+  {
+    std::size_t val = (xlen & 0x1f) << 5;
+    return val;
+  }
+};
+
+/* Lookup an already existing target description matching FEATURES, or
+   create a new target description if this is the first time we have seen
+   FEATURES.  For the same FEATURES the same target_desc is always
+   returned.  This is important when trying to lookup gdbarch objects as
+   GDBARCH_LIST_LOOKUP_BY_INFO performs a pointer comparison on target
+   descriptions to find candidate gdbarch objects.  */
+
+const target_desc *loongarch_lookup_target_description
+	(const struct loongarch_gdbarch_features features);
+
+#endif /* ARCH_LOONGARCH_H  */