gcc: xtensa: allow dynamic configuration

Import include/xtensa-dynconfig.h that defines XCHAL_* macros as fields
of a structure returned from the xtensa_get_config_v<x> function call.
Define that structure and fill it with default parameter values
specified in the include/xtensa-config.h.
Define reusable function xtensa_load_config that tries to load
configuration and return an address of an exported object from it.
Define the function xtensa_get_config_v1 that uses xtensa_load_config
to get structure xtensa_config_v1, either dynamically configured or the
default.

Provide essential XCHAL_* configuration parameters as __XCHAL_* built-in
macros. This way it will be possible to use them in libgcc and libc
without need to patch libgcc or libc source for the specific xtensa core
configuration.

gcc/
	* config.gcc (xtensa*-*-*): Add xtensa-dynconfig.o to extra_objs.
	* config/xtensa/t-xtensa (TM_H): Add xtensa-dynconfig.h.
	(xtensa-dynconfig.o): New rule.
	* config/xtensa/xtensa-dynconfig.c: New file.
	* config/xtensa/xtensa-protos.h (xtensa_get_config_strings): New
	declaration.
	* config/xtensa/xtensa.h (xtensa-config.h): Replace #include
	with xtensa-dynconfig.h
	(XCHAL_HAVE_MUL32_HIGH, XCHAL_HAVE_RELEASE_SYNC)
	(XCHAL_HAVE_S32C1I, XCHAL_HAVE_THREADPTR)
	(XCHAL_HAVE_FP_POSTINC): Drop definitions.
	(TARGET_DIV32): Replace with __XCHAL_HAVE_DIV32.
	(TARGET_CPU_CPP_BUILTINS): Add new 'builtin' variable and loop
	through string array returned by the xtensa_get_config_strings
	function call.

include/
	* xtensa-dynconfig.h: New file.

5 files changed, 184 insertions, 18 deletions

diff --git a/gcc/config.gcc b/gcc/config.gcc
index b5eda04..9519023 100644
--- a/gcc/config.gcc
+++ b/gcc/config.gcc
@@ -561,6 +561,7 @@ tic6x-*-*)
 	;;
 xtensa*-*-*)
 	extra_options="${extra_options} fused-madd.opt"
+	extra_objs="xtensa-dynconfig.o"
 	;;
 esac
 
diff --git a/gcc/config/xtensa/t-xtensa b/gcc/config/xtensa/t-xtensa
index 6d43b37..4e5b7de 100644
--- a/gcc/config/xtensa/t-xtensa
+++ b/gcc/config/xtensa/t-xtensa
@@ -16,5 +16,11 @@
 # along with GCC; see the file COPYING3.  If not see
 # <http://www.gnu.org/licenses/>.
 
-TM_H += $(srcdir)/../include/xtensa-config.h
+TM_H += $(srcdir)/../include/xtensa-config.h \
+	$(srcdir)/../include/xtensa-dynconfig.h
 $(out_object_file): gt-xtensa.h
+
+xtensa-dynconfig.o: $(srcdir)/config/xtensa/xtensa-dynconfig.c \
+  $(CONFIG_H) $(SYSTEM_H) $(srcdir)/../include/xtensa-dynconfig.h \
+  $(srcdir)/../include/xtensa-config.h
+	$(COMPILER) -c $(ALL_COMPILERFLAGS) $(ALL_CPPFLAGS) $<
diff --git a/gcc/config/xtensa/xtensa-dynconfig.c b/gcc/config/xtensa/xtensa-dynconfig.c
new file mode 100644
index 0000000..056204a
--- /dev/null
+++ b/gcc/config/xtensa/xtensa-dynconfig.c
@@ -0,0 +1,170 @@
+/* Xtensa configuration settings loader.
+   Copyright (C) 2022 Free Software Foundation, Inc.
+
+   This file is part of GCC.
+
+   GCC 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, or (at your option) any later
+   version.
+
+   GCC 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 GCC; see the file COPYING3.  If not see
+   <http://www.gnu.org/licenses/>.  */
+
+#include <config.h>
+#include <system.h>
+#include <coretypes.h>
+#include <diagnostic.h>
+#include <intl.h>
+#define XTENSA_CONFIG_DEFINITION
+#include "xtensa-config.h"
+#include "xtensa-dynconfig.h"
+
+#if defined (HAVE_DLFCN_H)
+#include <dlfcn.h>
+#elif defined (_WIN32)
+#include <windows.h>
+#define ENABLE_PLUGIN
+#endif
+
+#if !defined (HAVE_DLFCN_H) && defined (_WIN32)
+
+#define RTLD_LAZY 0      /* Dummy value.  */
+
+static void *
+dlopen (const char *file, int mode ATTRIBUTE_UNUSED)
+{
+  return LoadLibrary (file);
+}
+
+static void *
+dlsym (void *handle, const char *name)
+{
+  return (void *) GetProcAddress ((HMODULE) handle, name);
+}
+
+static int ATTRIBUTE_UNUSED
+dlclose (void *handle)
+{
+  FreeLibrary ((HMODULE) handle);
+  return 0;
+}
+
+static const char *
+dlerror (void)
+{
+  return _("Unable to load DLL.");
+}
+
+#endif /* !defined (HAVE_DLFCN_H) && defined (_WIN32)  */
+
+#define CONFIG_ENV_NAME "XTENSA_GNU_CONFIG"
+
+const void *xtensa_load_config (const char *name ATTRIBUTE_UNUSED,
+				const void *no_plugin_def,
+				const void *no_name_def ATTRIBUTE_UNUSED)
+{
+  static int init;
+#ifdef ENABLE_PLUGIN
+  static void *handle;
+  void *p;
+
+  if (!init)
+    {
+      const char *path = getenv (CONFIG_ENV_NAME);
+
+      init = 1;
+      if (!path)
+	return no_plugin_def;
+      handle = dlopen (path, RTLD_LAZY);
+      if (!handle)
+	{
+	  fatal_error (input_location,
+		       _("%qs is defined but could not be loaded: %s"),
+		       CONFIG_ENV_NAME, dlerror ());
+	  exit (FATAL_EXIT_CODE);
+	}
+      if (dlsym (handle, "plugin_is_GPL_compatible") == NULL)
+	{
+	  fatal_error (input_location,
+		       _("%qs plugin is not licensed under a GPL-compatible license"),
+		       CONFIG_ENV_NAME);
+	  exit (FATAL_EXIT_CODE);
+	}
+    }
+  else if (!handle)
+    {
+      return no_plugin_def;
+    }
+
+  p = dlsym (handle, name);
+  if (!p)
+    {
+      if (no_name_def)
+	return no_name_def;
+
+      fatal_error (input_location,
+		   _("%qs is loaded but symbol %qs is not found: %s"),
+		   CONFIG_ENV_NAME, name, dlerror ());
+      exit (FATAL_EXIT_CODE);
+    }
+  return p;
+#else
+  if (!init)
+    {
+      const char *path = getenv (CONFIG_ENV_NAME);
+
+      init = 1;
+      if (path)
+	{
+	  fatal_error (input_location,
+		       _("%qs is defined but plugin support is disabled"),
+		       CONFIG_ENV_NAME);
+	  exit (FATAL_EXIT_CODE);
+	}
+    }
+  return no_plugin_def;
+#endif
+}
+
+XTENSA_CONFIG_INSTANCE_LIST;
+
+#define _STRINGIFY(a) #a
+#define STRINGIFY(a) _STRINGIFY(a)
+
+#undef XTENSA_CONFIG_ENTRY
+#define XTENSA_CONFIG_ENTRY(a) "__" #a "=" STRINGIFY(a)
+
+static const char * const xtensa_config_strings[] = {
+    XTENSA_CONFIG_ENTRY_LIST,
+    NULL,
+};
+
+const struct xtensa_config_v1 *xtensa_get_config_v1 (void)
+{
+  static const struct xtensa_config_v1 *config;
+
+  if (!config)
+    config = (const struct xtensa_config_v1 *) xtensa_load_config ("xtensa_config_v1",
+								   &xtensa_config_v1,
+								   NULL);
+  return config;
+}
+
+const char * const *xtensa_get_config_strings (void)
+{
+  static const char * const *config_strings;
+
+  if (!config_strings)
+    config_strings = (const char * const *) xtensa_load_config ("xtensa_config_strings",
+								&xtensa_config_strings,
+								NULL);
+
+  return config_strings;
+}
diff --git a/gcc/config/xtensa/xtensa-protos.h b/gcc/config/xtensa/xtensa-protos.h
index bc75ad9..91a215e 100644
--- a/gcc/config/xtensa/xtensa-protos.h
+++ b/gcc/config/xtensa/xtensa-protos.h
@@ -81,5 +81,6 @@ extern void xtensa_expand_epilogue (bool);
 extern void order_regs_for_local_alloc (void);
 extern enum reg_class xtensa_regno_to_class (int regno);
 extern HOST_WIDE_INT xtensa_initial_elimination_offset (int from, int to);
+extern const char **xtensa_get_config_strings (void);
 
 #endif /* !__XTENSA_PROTOS_H__ */
diff --git a/gcc/config/xtensa/xtensa.h b/gcc/config/xtensa/xtensa.h
index 2275fe6..7e19306 100644
--- a/gcc/config/xtensa/xtensa.h
+++ b/gcc/config/xtensa/xtensa.h
@@ -19,27 +19,12 @@ along with GCC; see the file COPYING3.  If not see
 <http://www.gnu.org/licenses/>.  */
 
 /* Get Xtensa configuration settings */
-#include "xtensa-config.h"
+#include "xtensa-dynconfig.h"
 
 /* External variables defined in xtensa.cc.  */
 
 /* Macros used in the machine description to select various Xtensa
    configuration options.  */
-#ifndef XCHAL_HAVE_MUL32_HIGH
-#define XCHAL_HAVE_MUL32_HIGH 0
-#endif
-#ifndef XCHAL_HAVE_RELEASE_SYNC
-#define XCHAL_HAVE_RELEASE_SYNC 0
-#endif
-#ifndef XCHAL_HAVE_S32C1I
-#define XCHAL_HAVE_S32C1I 0
-#endif
-#ifndef XCHAL_HAVE_THREADPTR
-#define XCHAL_HAVE_THREADPTR 0
-#endif
-#ifndef XCHAL_HAVE_FP_POSTINC
-#define XCHAL_HAVE_FP_POSTINC 0
-#endif
 #define TARGET_BIG_ENDIAN	XCHAL_HAVE_BE
 #define TARGET_DENSITY		XCHAL_HAVE_DENSITY
 #define TARGET_MAC16		XCHAL_HAVE_MAC16
@@ -76,7 +61,7 @@ along with GCC; see the file COPYING3.  If not see
 #endif
 
 /* Define this if the target has no hardware divide instructions.  */
-#if !TARGET_DIV32
+#if !__XCHAL_HAVE_DIV32
 #define TARGET_HAS_NO_HW_DIVIDE
 #endif
 
@@ -84,6 +69,7 @@ along with GCC; see the file COPYING3.  If not see
 /* Target CPU builtins.  */
 #define TARGET_CPU_CPP_BUILTINS()					\
   do {									\
+    const char **builtin;						\
     builtin_assert ("cpu=xtensa");					\
     builtin_assert ("machine=xtensa");					\
     builtin_define ("__xtensa__");					\
@@ -93,6 +79,8 @@ along with GCC; see the file COPYING3.  If not see
     builtin_define (TARGET_BIG_ENDIAN ? "__XTENSA_EB__" : "__XTENSA_EL__"); \
     if (!TARGET_HARD_FLOAT)						\
       builtin_define ("__XTENSA_SOFT_FLOAT__");				\
+    for (builtin = xtensa_get_config_strings (); *builtin; ++builtin)	\
+      builtin_define (*builtin);					\
   } while (0)
 
 #define CPP_SPEC " %(subtarget_cpp_spec) "