gccrs: Compiler proper interface kicks off the pipeline

This is a wrapper to get out of C land in the rust-lang.cc and into our
class hierarchy for the rust front-end. We expect that the front-end only
support one source file input as the expansion pass will attempt to resolve
that relative pass and parse accordingly.

The main missing piece here is that we are using saw_errors() to return
early which is unnecessary but as our error handling has been improving
over time we will start to take advantage of error node in our type system
as well as error_mark_node from GCC. The caveat being that our lints/checks
expect no errors and will throw an assertion.

	gcc/rust/
	* rust-lang.cc: New.
	* rust-session-manager.cc: New.
	* rust-session-manager.h: New.

1 files changed, 456 insertions, 0 deletions

diff --git a/gcc/rust/rust-lang.cc b/gcc/rust/rust-lang.cc
new file mode 100644
index 0000000..241a9b4
--- /dev/null
+++ b/gcc/rust/rust-lang.cc
@@ -0,0 +1,456 @@
+// Copyright (C) 2020-2022 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 "rust-system.h"
+#include "rust-diagnostics.h"
+#include "coretypes.h"
+#include "target.h"
+#include "tree.h"
+#include "gimple-expr.h"
+#include "diagnostic.h"
+#include "opts.h"
+#include "fold-const.h"
+#include "gimplify.h"
+#include "stor-layout.h"
+#include "debug.h"
+#include "convert.h"
+#include "langhooks.h"
+#include "langhooks-def.h"
+#include "selftest.h"
+#include "rust-cfg-parser.h"
+#include "rust-privacy-ctx.h"
+#include "rust-ast-resolve-item.h"
+#include "rust-optional.h"
+
+#include <mpfr.h>
+// note: header files must be in this order or else forward declarations don't
+// work properly. Kinda dumb system, but have to live with it. clang-format
+// seems to mess it up
+/* Order: config, system, coretypes, target, tree, gimple-expr, diagnostic,
+ * opts, fold-const, gimplify, stor-layout, debug, convert, langhooks,
+ * langhooks-def */
+
+// FIXME: test saving intellisense
+#include "options.h"
+
+// version check to stop compiling if c++ isn't c++11 or higher
+#if __cplusplus < 201103
+#error                                                                         \
+  "GCC Rust frontend requires C++11 or higher. You can compile the g++ frontend first and then compile the Rust frontend using that."
+#endif
+// TODO: is this best way to do it? Is it allowed? (should be)
+
+/* General TODOs:
+ *  - convert all copies of expensive-to-copy (deep copy) AST objects into
+ * moves, if possible. Don't remove clone functionality - it may be required for
+ * e.g. HIR conversion.
+ */
+
+#include "rust-session-manager.h"
+
+// Language-dependent contents of a type. GTY() mark used for garbage collector.
+struct GTY (()) lang_type
+{
+};
+
+// Language-dependent contents of a decl.
+struct GTY (()) lang_decl
+{
+};
+
+// Language-dependent contents of an identifier.  This must include a
+// tree_identifier.
+struct GTY (()) lang_identifier
+{
+  struct tree_identifier common;
+};
+
+// The resulting tree type.
+union GTY ((
+  desc ("TREE_CODE (&%h.generic) == IDENTIFIER_NODE"),
+  chain_next (
+    "CODE_CONTAINS_STRUCT (TREE_CODE (&%h.generic), "
+    "TS_COMMON) ? ((union lang_tree_node *) TREE_CHAIN (&%h.generic)) : NULL")))
+  lang_tree_node
+{
+  union tree_node GTY ((tag ("0"), desc ("tree_node_structure (&%h)"))) generic;
+  struct lang_identifier GTY ((tag ("1"))) identifier;
+};
+
+// We don't use language_function.
+struct GTY (()) language_function
+{
+};
+
+// has to be in same compilation unit as session, so here for now
+void
+rust_add_target_info (const char *key, const char *value)
+{
+  sorry ("TODO");
+
+  Rust::Session::get_instance ().options.target_data.insert_key_value_pair (
+    key, value);
+}
+
+/* Language hooks.  */
+
+/* Initial lang hook called (possibly), used for initialisation.
+ * Must call build_common_tree_nodes, set_sizetype, build_common_tree_nodes_2,
+ * and build_common_builtin_nodes, as well as set global variable
+ * void_list_node. Apparently called after option handling? */
+static bool
+grs_langhook_init (void)
+{
+  /* Something to do with this:
+   This allows the code in d-builtins.cc to not have to worry about
+   converting (C signed char *) to (D char *) for string arguments of
+   built-in functions. The parameter (signed_char = false) specifies
+   whether char is signed.  */
+  build_common_tree_nodes (false);
+
+  // Creates a new TREE_LIST node with purpose NULL_TREE and value
+  // void_type_node
+  void_list_node = build_tree_list (NULL_TREE, void_type_node);
+
+  // Builds built-ins for middle-end after all front-end built-ins are already
+  // instantiated
+  build_common_builtin_nodes ();
+
+  mpfr_set_default_prec (128);
+
+  using_eh_for_cleanups ();
+
+  // initialise compiler session
+  Rust::Session::get_instance ().init ();
+
+  return true;
+}
+
+/* The option mask (something to do with options for specific frontends or
+ * something). */
+static unsigned int
+grs_langhook_option_lang_mask (void)
+{
+  return CL_Rust;
+}
+
+/* Initialize the options structure. */
+static void
+grs_langhook_init_options_struct (struct gcc_options *opts)
+{
+  /* Operations are always wrapping in Rust, even on signed integer. This is
+   * useful for the low level wrapping_{add, sub, mul} intrinsics, not for
+   * regular arithmetic operations which are checked for overflow anyway using
+   * builtins */
+  opts->x_flag_wrapv = 1;
+
+  /* We need to warn on unused variables by default */
+  opts->x_warn_unused_variable = 1;
+  /* For const variables too */
+  opts->x_warn_unused_const_variable = 1;
+  /* And finally unused result for #[must_use] */
+  opts->x_warn_unused_result = 1;
+
+  // nothing yet - used by frontends to change specific options for the language
+  Rust::Session::get_instance ().init_options ();
+}
+
+/* Main entry point for front-end, apparently. Finds input file names in global
+ * vars in_fnames and num_in_fnames. From this, frontend can take over and do
+ * actual parsing and initial compilation. This function must create a complete
+ * parse tree in a global var, and then return.
+ *
+ * Some consider this the "start of compilation". */
+static void
+grs_langhook_parse_file (void)
+{
+  rust_debug ("Preparing to parse files. ");
+
+  Rust::Session::get_instance ().handle_input_files (num_in_fnames, in_fnames);
+}
+
+/* Seems to get the exact type for a specific type - e.g. for scalar float with
+ * 32-bit bitsize, it returns float, and for 64-bit bitsize, it returns double.
+ * Used to map RTL nodes to machine modes or something like that. */
+static tree
+grs_langhook_type_for_mode (machine_mode mode, int unsignedp)
+{
+  // TODO: change all this later to match rustc types
+  if (mode == TYPE_MODE (float_type_node))
+    return float_type_node;
+
+  if (mode == TYPE_MODE (double_type_node))
+    return double_type_node;
+
+  if (mode == TYPE_MODE (intQI_type_node)) // quarter integer mode - single byte
+					   // treated as integer
+    return unsignedp ? unsigned_intQI_type_node : intQI_type_node;
+  if (mode
+      == TYPE_MODE (intHI_type_node)) // half integer mode - two-byte integer
+    return unsignedp ? unsigned_intHI_type_node : intHI_type_node;
+  if (mode
+      == TYPE_MODE (intSI_type_node)) // single integer mode - four-byte integer
+    return unsignedp ? unsigned_intSI_type_node : intSI_type_node;
+  if (mode
+      == TYPE_MODE (
+	intDI_type_node)) // double integer mode - eight-byte integer
+    return unsignedp ? unsigned_intDI_type_node : intDI_type_node;
+  if (mode
+      == TYPE_MODE (intTI_type_node)) // tetra integer mode - 16-byte integer
+    return unsignedp ? unsigned_intTI_type_node : intTI_type_node;
+
+  if (mode == TYPE_MODE (integer_type_node))
+    return unsignedp ? unsigned_type_node : integer_type_node;
+
+  if (mode == TYPE_MODE (long_integer_type_node))
+    return unsignedp ? long_unsigned_type_node : long_integer_type_node;
+
+  if (mode == TYPE_MODE (long_long_integer_type_node))
+    return unsignedp ? long_long_unsigned_type_node
+		     : long_long_integer_type_node;
+
+  if (COMPLEX_MODE_P (mode))
+    {
+      if (mode == TYPE_MODE (complex_float_type_node))
+	return complex_float_type_node;
+      if (mode == TYPE_MODE (complex_double_type_node))
+	return complex_double_type_node;
+      if (mode == TYPE_MODE (complex_long_double_type_node))
+	return complex_long_double_type_node;
+      if (mode == TYPE_MODE (complex_integer_type_node) && !unsignedp)
+	return complex_integer_type_node;
+    }
+  /* gcc_unreachable */
+  return NULL;
+}
+
+// Record a builtin function. We just ignore builtin functions.
+static tree
+grs_langhook_builtin_function (tree decl ATTRIBUTE_UNUSED)
+{
+  return decl;
+}
+
+/* Return true if we are in the global binding level (which is never,
+ * apparently). */
+static bool
+grs_langhook_global_bindings_p (void)
+{
+  // return current_function_decl == NULL_TREE;
+  // gcc_unreachable();
+  // return true;
+  return false;
+}
+
+/* Push a declaration into the current binding level.  We can't
+   usefully implement this since we don't want to convert from tree
+   back to one of our internal data structures.  I think the only way
+   this is used is to record a decl which is to be returned by
+   getdecls, and we could implement it for that purpose if
+   necessary.  */
+static tree
+grs_langhook_pushdecl (tree decl ATTRIBUTE_UNUSED)
+{
+  gcc_unreachable ();
+  return NULL;
+}
+
+/* This hook is used to get the current list of declarations as trees.
+   We don't support that; instead we use the write_globals hook.  This
+   can't simply crash because it is called by -gstabs.  */
+static tree
+grs_langhook_getdecls (void)
+{
+  // gcc_unreachable();
+  return NULL;
+}
+
+// Handle Rust-specific options. Return false if nothing happened.
+static bool
+grs_langhook_handle_option (
+  size_t scode, const char *arg, HOST_WIDE_INT value, int kind ATTRIBUTE_UNUSED,
+  location_t loc ATTRIBUTE_UNUSED,
+  const struct cl_option_handlers *handlers ATTRIBUTE_UNUSED)
+{
+  // Convert integer code to lang.opt enum codes with names.
+  enum opt_code code = (enum opt_code) scode;
+
+  // Delegate to session manager
+  return Rust::Session::get_instance ().handle_option (code, arg, value, kind,
+						       loc, handlers);
+}
+
+/* Run after parsing options.  */
+static bool
+grs_langhook_post_options (const char **pfilename ATTRIBUTE_UNUSED)
+{
+  // can be used to override other options if required
+
+  // satisfies an assert in init_excess_precision in toplev.cc
+  if (flag_excess_precision /*_cmdline*/ == EXCESS_PRECISION_DEFAULT)
+    flag_excess_precision /*_cmdline*/ = EXCESS_PRECISION_STANDARD;
+
+  /* Returning false means that the backend should be used.  */
+  return false;
+}
+
+/* Rust-specific gimplification. May need to gimplify e.g.
+ * CALL_EXPR_STATIC_CHAIN */
+static int
+grs_langhook_gimplify_expr (tree *expr_p ATTRIBUTE_UNUSED,
+			    gimple_seq *pre_p ATTRIBUTE_UNUSED,
+			    gimple_seq *post_p ATTRIBUTE_UNUSED)
+{
+  if (TREE_CODE (*expr_p) == CALL_EXPR
+      && CALL_EXPR_STATIC_CHAIN (*expr_p) != NULL_TREE)
+    gimplify_expr (&CALL_EXPR_STATIC_CHAIN (*expr_p), pre_p, post_p,
+		   is_gimple_val, fb_rvalue);
+  return GS_UNHANDLED;
+}
+
+static tree
+grs_langhook_eh_personality (void)
+{
+  static tree personality_decl;
+  if (personality_decl == NULL_TREE)
+    {
+      personality_decl = build_personality_function ("gccrs");
+      rust_preserve_from_gc (personality_decl);
+    }
+  return personality_decl;
+}
+
+tree
+convert (tree type, tree expr)
+{
+  if (type == error_mark_node || expr == error_mark_node
+      || TREE_TYPE (expr) == error_mark_node)
+    return error_mark_node;
+
+  if (type == TREE_TYPE (expr))
+    return expr;
+
+  if (TYPE_MAIN_VARIANT (type) == TYPE_MAIN_VARIANT (TREE_TYPE (expr)))
+    return fold_convert (type, expr);
+
+  switch (TREE_CODE (type))
+    {
+    case VOID_TYPE:
+    case BOOLEAN_TYPE:
+      return fold_convert (type, expr);
+    case INTEGER_TYPE:
+      return convert_to_integer (type, expr);
+    case POINTER_TYPE:
+      return convert_to_pointer (type, expr);
+    case REAL_TYPE:
+      return convert_to_real (type, expr);
+    case COMPLEX_TYPE:
+      return convert_to_complex (type, expr);
+    default:
+      break;
+    }
+
+  gcc_unreachable ();
+}
+
+/* FIXME: This is a hack to preserve trees that we create from the
+   garbage collector.  */
+
+static GTY (()) tree rust_gc_root;
+
+void
+rust_preserve_from_gc (tree t)
+{
+  rust_gc_root = tree_cons (NULL_TREE, t, rust_gc_root);
+}
+
+/* Convert an identifier for use in an error message.  */
+
+const char *
+rust_localize_identifier (const char *ident)
+{
+  return identifier_to_locale (ident);
+}
+
+/* The language hooks data structure. This is the main interface between the GCC
+ * front-end and the GCC middle-end/back-end. A list of language hooks could be
+ * found in <gcc>/langhooks.h
+ */
+#undef LANG_HOOKS_NAME
+#undef LANG_HOOKS_INIT
+#undef LANG_HOOKS_OPTION_LANG_MASK
+#undef LANG_HOOKS_INIT_OPTIONS_STRUCT
+#undef LANG_HOOKS_HANDLE_OPTION
+#undef LANG_HOOKS_POST_OPTIONS
+#undef LANG_HOOKS_PARSE_FILE
+#undef LANG_HOOKS_TYPE_FOR_MODE
+#undef LANG_HOOKS_BUILTIN_FUNCTION
+#undef LANG_HOOKS_GLOBAL_BINDINGS_P
+#undef LANG_HOOKS_PUSHDECL
+#undef LANG_HOOKS_GETDECLS
+#undef LANG_HOOKS_WRITE_GLOBALS
+#undef LANG_HOOKS_GIMPLIFY_EXPR
+#undef LANG_HOOKS_EH_PERSONALITY
+
+#define LANG_HOOKS_NAME "GNU Rust"
+#define LANG_HOOKS_INIT grs_langhook_init
+#define LANG_HOOKS_OPTION_LANG_MASK grs_langhook_option_lang_mask
+#define LANG_HOOKS_INIT_OPTIONS_STRUCT grs_langhook_init_options_struct
+#define LANG_HOOKS_HANDLE_OPTION grs_langhook_handle_option
+#define LANG_HOOKS_POST_OPTIONS grs_langhook_post_options
+/* Main lang-hook, apparently. Finds input file names in global vars in_fnames
+ * and num_in_fnames From this, frontend can take over and do actual parsing and
+ * initial compilation.
+ * This hook must create a complete parse tree in a global var, and then return.
+ */
+#define LANG_HOOKS_PARSE_FILE grs_langhook_parse_file
+#define LANG_HOOKS_TYPE_FOR_MODE grs_langhook_type_for_mode
+#define LANG_HOOKS_BUILTIN_FUNCTION grs_langhook_builtin_function
+#define LANG_HOOKS_GLOBAL_BINDINGS_P grs_langhook_global_bindings_p
+#define LANG_HOOKS_PUSHDECL grs_langhook_pushdecl
+#define LANG_HOOKS_GETDECLS grs_langhook_getdecls
+#define LANG_HOOKS_GIMPLIFY_EXPR grs_langhook_gimplify_expr
+#define LANG_HOOKS_EH_PERSONALITY grs_langhook_eh_personality
+
+#if CHECKING_P
+
+#undef LANG_HOOKS_RUN_LANG_SELFTESTS
+#define LANG_HOOKS_RUN_LANG_SELFTESTS selftest::run_rust_tests
+
+namespace selftest {
+
+void
+run_rust_tests ()
+{
+  // Call tests for the rust frontend here
+  rust_cfg_parser_test ();
+  rust_privacy_ctx_test ();
+  rust_crate_name_validation_test ();
+  rust_simple_path_resolve_test ();
+  rust_optional_test ();
+}
+} // namespace selftest
+
+#endif /* !CHECKING_P */
+
+// Expands all LANG_HOOKS_x of GCC
+struct lang_hooks lang_hooks = LANG_HOOKS_INITIALIZER;
+
+// These are for GCC's garbage collector to work properly or something
+#include "gt-rust-rust-lang.h"
+#include "gtype-rust.h"