[Rust,front-end,v2,36/37] gccrs: compiler proper interface kicks off the pipeline

Message ID 20220824115956.737931-37-philip.herron@embecosm.com
State New
Headers
Series [Rust,front-end,v2,01/37] Use DW_ATE_UTF for the Rust 'char' type |

Commit Message

herron.philip@googlemail.com Aug. 24, 2022, 11:59 a.m. UTC
  From: Philip Herron <philip.herron@embecosm.com>

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            |  452 ++++++++++++
 gcc/rust/rust-session-manager.cc | 1189 ++++++++++++++++++++++++++++++
 gcc/rust/rust-session-manager.h  |  358 +++++++++
 3 files changed, 1999 insertions(+)
 create mode 100644 gcc/rust/rust-lang.cc
 create mode 100644 gcc/rust/rust-session-manager.cc
 create mode 100644 gcc/rust/rust-session-manager.h
  

Patch

diff --git a/gcc/rust/rust-lang.cc b/gcc/rust/rust-lang.cc
new file mode 100644
index 00000000000..c9af790f66b
--- /dev/null
+++ b/gcc/rust/rust-lang.cc
@@ -0,0 +1,452 @@ 
+// 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-diagnostics.h"
+#include "config.h"
+#include "system.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-system.h"
+#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;
+
+  // 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 fold (convert_to_integer (type, expr));
+    case POINTER_TYPE:
+      return fold (convert_to_pointer (type, expr));
+    case REAL_TYPE:
+      return fold (convert_to_real (type, expr));
+    case COMPLEX_TYPE:
+      return fold (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"
diff --git a/gcc/rust/rust-session-manager.cc b/gcc/rust/rust-session-manager.cc
new file mode 100644
index 00000000000..6d7f1a85f19
--- /dev/null
+++ b/gcc/rust/rust-session-manager.cc
@@ -0,0 +1,1189 @@ 
+// 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-session-manager.h"
+#include "rust-diagnostics.h"
+#include "rust-unsafe-checker.h"
+#include "rust-lex.h"
+#include "rust-parse.h"
+#include "rust-macro-expand.h"
+#include "rust-ast-resolve.h"
+#include "rust-ast-lower.h"
+#include "rust-hir-type-check.h"
+#include "rust-privacy-check.h"
+#include "rust-const-checker.h"
+#include "rust-tycheck-dump.h"
+#include "rust-compile.h"
+#include "rust-cfg-parser.h"
+#include "rust-lint-scan-deadcode.h"
+#include "rust-lint-unused-var.h"
+#include "rust-hir-dump.h"
+#include "rust-ast-dump.h"
+#include "rust-export-metadata.h"
+#include "rust-imports.h"
+#include "rust-extern-crate.h"
+#include "rust-attributes.h"
+
+#include "diagnostic.h"
+#include "input.h"
+#include "selftest.h"
+#include "target.h"
+
+extern bool
+saw_errors (void);
+
+extern Linemap *
+rust_get_linemap ();
+
+extern Backend *
+rust_get_backend ();
+
+namespace Rust {
+
+const char *kLexDumpFile = "gccrs.lex.dump";
+const char *kASTDumpFile = "gccrs.ast.dump";
+const char *kASTPrettyDumpFile = "gccrs.ast-pretty.dump";
+const char *kASTExpandedDumpFile = "gccrs.ast-expanded.dump";
+const char *kHIRDumpFile = "gccrs.hir.dump";
+const char *kHIRPrettyDumpFile = "gccrs.hir-pretty.dump";
+const char *kHIRTypeResolutionDumpFile = "gccrs.type-resolution.dump";
+const char *kTargetOptionsDumpFile = "gccrs.target-options.dump";
+
+const std::string kDefaultCrateName = "rust_out";
+const size_t kMaxNameLength = 64;
+
+Session &
+Session::get_instance ()
+{
+  static Session instance;
+  return instance;
+}
+
+static std::string
+infer_crate_name (const std::string &filename)
+{
+  if (filename == "-")
+    return kDefaultCrateName;
+
+  std::string crate = std::string (filename);
+  size_t path_sep = crate.find_last_of (file_separator);
+
+  // find the base filename
+  if (path_sep != std::string::npos)
+    crate.erase (0, path_sep + 1);
+
+  // find the file stem name (remove file extension)
+  size_t ext_position = crate.find_last_of ('.');
+  if (ext_position != std::string::npos)
+    crate.erase (ext_position);
+
+  // Replace all the '-' symbols with '_' per Rust rules
+  for (auto &c : crate)
+    {
+      if (c == '-')
+	c = '_';
+    }
+  return crate;
+}
+
+/* Validate the crate name using the ASCII rules
+   TODO: Support Unicode version of the rules */
+
+static bool
+validate_crate_name (const std::string &crate_name, Error &error)
+{
+  if (crate_name.empty ())
+    {
+      error = Error (Location (), "crate name cannot be empty");
+      return false;
+    }
+  if (crate_name.length () > kMaxNameLength)
+    {
+      error = Error (Location (), "crate name cannot exceed %lu characters",
+		     (unsigned long) kMaxNameLength);
+      return false;
+    }
+  for (auto &c : crate_name)
+    {
+      if (!(ISALNUM (c) || c == '_'))
+	{
+	  error = Error (Location (),
+			 "invalid character %<%c%> in crate name: %<%s%>", c,
+			 crate_name.c_str ());
+	  return false;
+	}
+    }
+  return true;
+}
+
+void
+Session::init ()
+{
+  options.target_data.insert_key_value_pair ("target_pointer_width",
+					     std::to_string (POINTER_SIZE));
+  options.target_data.insert_key_value_pair ("target_endian", BYTES_BIG_ENDIAN
+								? "big"
+								: "little");
+
+  // setup singleton linemap
+  linemap = rust_get_linemap ();
+
+  // setup backend to GCC GIMPLE
+  backend = rust_get_backend ();
+
+  // setup mappings class
+  mappings = Analysis::Mappings::get ();
+}
+
+/* Initialise default options. Actually called before handle_option, unlike init
+ * itself. */
+void
+Session::init_options ()
+{}
+
+// Handle option selection.
+bool
+Session::handle_option (
+  enum opt_code code, const char *arg, HOST_WIDE_INT value ATTRIBUTE_UNUSED,
+  int kind ATTRIBUTE_UNUSED, location_t loc ATTRIBUTE_UNUSED,
+  const struct cl_option_handlers *handlers ATTRIBUTE_UNUSED)
+{
+  // used to store whether results of various stuff are successful
+  bool ret = true;
+
+  // Handles options as listed in lang.opt.
+  switch (code)
+    {
+    case OPT_I:
+      case OPT_L: {
+	// TODO: add search path
+	const std::string p = std::string (arg);
+	add_search_path (p);
+      }
+      break;
+
+    case OPT_frust_crate_:
+      // set the crate name
+      if (arg != nullptr)
+	{
+	  auto error = Error (Location (), std::string ());
+	  if ((ret = validate_crate_name (arg, error)))
+	    {
+	      options.set_crate_name (arg);
+	      options.crate_name_set_manually = true;
+	    }
+	  else
+	    {
+	      rust_assert (!error.message.empty ());
+	      error.emit_error ();
+	    }
+	}
+      else
+	ret = false;
+      break;
+
+    case OPT_frust_dump_:
+      // enable dump and return whether this was successful
+      if (arg != nullptr)
+	{
+	  ret = enable_dump (std::string (arg));
+	}
+      else
+	{
+	  ret = false;
+	}
+      break;
+
+    case OPT_frust_mangling_:
+      Compile::Mangler::set_mangling (flag_rust_mangling);
+      break;
+
+      case OPT_frust_cfg_: {
+	auto string_arg = std::string (arg);
+	ret = handle_cfg_option (string_arg);
+	break;
+      }
+
+    case OPT_frust_edition_:
+      options.set_edition (flag_rust_edition);
+      break;
+
+    case OPT_frust_metadata_output_:
+      options.set_metadata_output (arg);
+      break;
+
+    default:
+      break;
+    }
+
+  return ret;
+}
+
+bool
+Session::handle_cfg_option (std::string &input)
+{
+  std::string key;
+  std::string value;
+
+  // Refactor this if needed
+  if (!parse_cfg_option (input, key, value))
+    {
+      rust_error_at (
+	Location (),
+	"invalid argument to %<-frust-cfg%>: Accepted formats are "
+	"%<-frust-cfg=key%> or %<-frust-cfg=key=\"value\"%> (quoted)");
+      return false;
+    }
+
+  if (value.empty ())
+    // rustc does not seem to error on dup key
+    options.target_data.insert_key (key);
+  else
+    options.target_data.insert_key_value_pair (key, value);
+
+  return true;
+}
+
+/* Enables a certain dump depending on the name passed in. Returns true if
+ * name is valid, false otherwise. */
+bool
+Session::enable_dump (std::string arg)
+{
+  if (arg.empty ())
+    {
+      rust_error_at (
+	Location (),
+	"dump option was not given a name. choose %<lex%>, %<parse%>, "
+	"%<register_plugins%>, %<injection%>, %<expansion%>, %<resolution%>,"
+	" %<target_options%>, %<hir%>, or %<all%>");
+      return false;
+    }
+
+  if (arg == "all")
+    {
+      options.enable_all_dump_options ();
+    }
+  else if (arg == "lex")
+    {
+      options.enable_dump_option (CompileOptions::LEXER_DUMP);
+    }
+  else if (arg == "parse")
+    {
+      options.enable_dump_option (CompileOptions::PARSER_AST_DUMP);
+    }
+  else if (arg == "ast-pretty")
+    {
+      options.enable_dump_option (CompileOptions::AST_DUMP_PRETTY);
+    }
+  else if (arg == "register_plugins")
+    {
+      options.enable_dump_option (CompileOptions::REGISTER_PLUGINS_DUMP);
+    }
+  else if (arg == "injection")
+    {
+      options.enable_dump_option (CompileOptions::INJECTION_DUMP);
+    }
+  else if (arg == "expansion")
+    {
+      options.enable_dump_option (CompileOptions::EXPANSION_DUMP);
+    }
+  else if (arg == "resolution")
+    {
+      options.enable_dump_option (CompileOptions::RESOLUTION_DUMP);
+    }
+  else if (arg == "target_options")
+    {
+      options.enable_dump_option (CompileOptions::TARGET_OPTION_DUMP);
+    }
+  else if (arg == "hir")
+    {
+      options.enable_dump_option (CompileOptions::HIR_DUMP);
+    }
+  else if (arg == "hir-pretty")
+    {
+      options.enable_dump_option (CompileOptions::HIR_DUMP_PRETTY);
+    }
+  else
+    {
+      rust_error_at (
+	Location (),
+	"dump option %qs was unrecognised. choose %<lex%>, %<parse%>, "
+	"%<register_plugins%>, %<injection%>, %<expansion%>, %<resolution%>,"
+	" %<target_options%>, or %<hir%>",
+	arg.c_str ());
+      return false;
+    }
+  return true;
+}
+
+/* Actual main entry point for front-end. Called from langhook to parse files.
+ */
+void
+Session::handle_input_files (int num_files, const char **files)
+{
+  if (num_files != 1)
+    rust_fatal_error (Location (),
+		      "only one file may be specified on the command line");
+
+  const auto &file = files[0];
+
+  if (options.crate_name.empty ())
+    {
+      auto filename = "-";
+      if (num_files > 0)
+	filename = files[0];
+
+      auto crate_name = infer_crate_name (filename);
+      rust_debug ("inferred crate name: %s", crate_name.c_str ());
+      // set the preliminary crate name here
+      // we will figure out the real crate name in `handle_crate_name`
+      options.set_crate_name (crate_name);
+    }
+
+  CrateNum crate_num = mappings->get_next_crate_num (options.get_crate_name ());
+  mappings->set_current_crate (crate_num);
+
+  rust_debug ("Attempting to parse file: %s", file);
+  compile_crate (file);
+}
+
+void
+Session::handle_crate_name (const AST::Crate &parsed_crate)
+{
+  auto mappings = Analysis::Mappings::get ();
+  auto crate_name_changed = false;
+  auto error = Error (Location (), std::string ());
+
+  for (const auto &attr : parsed_crate.inner_attrs)
+    {
+      if (attr.get_path () != "crate_name")
+	continue;
+      if (!attr.has_attr_input ())
+	{
+	  rust_error_at (attr.get_locus (),
+			 "%<crate_name%> accepts one argument");
+	  continue;
+	}
+
+      auto &literal
+	= static_cast<AST::AttrInputLiteral &> (attr.get_attr_input ());
+      const auto &msg_str = literal.get_literal ().as_string ();
+      if (!validate_crate_name (msg_str, error))
+	{
+	  error.locus = attr.get_locus ();
+	  error.emit_error ();
+	  continue;
+	}
+
+      auto options = Session::get_instance ().options;
+      if (options.crate_name_set_manually && (options.crate_name != msg_str))
+	{
+	  rust_error_at (attr.get_locus (),
+			 "%<-frust-crate-name%> and %<#[crate_name]%> are "
+			 "required to match, but %qs does not match %qs",
+			 options.crate_name.c_str (), msg_str.c_str ());
+	}
+      crate_name_changed = true;
+      options.set_crate_name (msg_str);
+      mappings->set_crate_name (mappings->get_current_crate (), msg_str);
+    }
+
+  options.crate_name_set_manually |= crate_name_changed;
+  if (!options.crate_name_set_manually
+      && !validate_crate_name (options.crate_name, error))
+    {
+      error.emit_error ();
+      rust_inform (linemap->get_location (0),
+		   "crate name inferred from this file");
+    }
+}
+
+// Parses a single file with filename filename.
+void
+Session::compile_crate (const char *filename)
+{
+  RAIIFile file_wrap (filename);
+  if (!file_wrap.ok ())
+    {
+      rust_error_at (Location (), "cannot open filename %s: %m", filename);
+      return;
+    }
+
+  // parse file here
+  /* create lexer and parser - these are file-specific and so aren't instance
+   * variables */
+  Lexer lex (filename, std::move (file_wrap), linemap);
+  Parser<Lexer> parser (lex);
+
+  // generate crate from parser
+  std::unique_ptr<AST::Crate> ast_crate = parser.parse_crate ();
+
+  // handle crate name
+  handle_crate_name (*ast_crate.get ());
+
+  // dump options
+  if (options.dump_option_enabled (CompileOptions::LEXER_DUMP))
+    {
+      dump_lex (parser);
+    }
+  if (options.dump_option_enabled (CompileOptions::PARSER_AST_DUMP))
+    {
+      dump_ast (parser, *ast_crate.get ());
+    }
+  if (options.dump_option_enabled (CompileOptions::AST_DUMP_PRETTY))
+    {
+      dump_ast_pretty (*ast_crate.get ());
+    }
+  if (options.dump_option_enabled (CompileOptions::TARGET_OPTION_DUMP))
+    {
+      options.target_data.dump_target_options ();
+    }
+
+  if (saw_errors ())
+    return;
+
+  // setup the mappings for this AST
+  CrateNum current_crate = mappings->get_current_crate ();
+  AST::Crate &parsed_crate
+    = mappings->insert_ast_crate (std::move (ast_crate), current_crate);
+
+  /* basic pipeline:
+   *  - lex
+   *  - parse
+   *  - register plugins (dummy stage for now) - attribute injection? what is
+   * this? (attribute injection is injecting attributes specified in command
+   * line into crate root)
+   *  - injection (some lint checks or dummy, register builtin macros, crate
+   * injection)
+   *  - expansion (expands all macros, maybe build test harness, AST
+   * validation, maybe macro crate)
+   *  - resolution (name resolution, type resolution, maybe feature checking,
+   * maybe buffered lints)
+   *  TODO not done */
+
+  rust_debug ("\033[0;31mSUCCESSFULLY PARSED CRATE \033[0m");
+
+  // If -fsyntax-only was passed, we can just skip the remaining passes.
+  // Parsing errors are already emitted in `parse_crate()`
+  if (flag_syntax_only)
+    return;
+
+  // register plugins pipeline stage
+  register_plugins (parsed_crate);
+  rust_debug ("\033[0;31mSUCCESSFULLY REGISTERED PLUGINS \033[0m");
+  if (options.dump_option_enabled (CompileOptions::REGISTER_PLUGINS_DUMP))
+    {
+      // TODO: what do I dump here?
+    }
+
+  // injection pipeline stage
+  injection (parsed_crate);
+  rust_debug ("\033[0;31mSUCCESSFULLY FINISHED INJECTION \033[0m");
+  if (options.dump_option_enabled (CompileOptions::INJECTION_DUMP))
+    {
+      // TODO: what do I dump here? injected crate names?
+    }
+
+  Analysis::AttributeChecker ().go (parsed_crate);
+
+  // expansion pipeline stage
+  expansion (parsed_crate);
+  rust_debug ("\033[0;31mSUCCESSFULLY FINISHED EXPANSION \033[0m");
+  if (options.dump_option_enabled (CompileOptions::EXPANSION_DUMP))
+    {
+      // dump AST with expanded stuff
+      rust_debug ("BEGIN POST-EXPANSION AST DUMP");
+      dump_ast_expanded (parser, parsed_crate);
+      rust_debug ("END POST-EXPANSION AST DUMP");
+    }
+
+  // resolution pipeline stage
+  Resolver::NameResolution::Resolve (parsed_crate);
+  if (options.dump_option_enabled (CompileOptions::RESOLUTION_DUMP))
+    {
+      // TODO: what do I dump here? resolved names? AST with resolved names?
+    }
+
+  if (saw_errors ())
+    return;
+
+  // lower AST to HIR
+  std::unique_ptr<HIR::Crate> lowered
+    = HIR::ASTLowering::Resolve (parsed_crate);
+  if (saw_errors ())
+    return;
+
+  // add the mappings to it
+  HIR::Crate &hir = mappings->insert_hir_crate (std::move (lowered));
+  if (options.dump_option_enabled (CompileOptions::HIR_DUMP))
+    {
+      dump_hir (hir);
+    }
+  if (options.dump_option_enabled (CompileOptions::HIR_DUMP_PRETTY))
+    {
+      dump_hir_pretty (hir);
+    }
+
+  // type resolve
+  Resolver::TypeResolution::Resolve (hir);
+  if (options.dump_option_enabled (CompileOptions::TYPE_RESOLUTION_DUMP))
+    {
+      dump_type_resolution (hir);
+    }
+
+  if (saw_errors ())
+    return;
+
+  // Various HIR error passes. The privacy pass happens before the unsafe checks
+  Privacy::Resolver::resolve (hir);
+  if (saw_errors ())
+    return;
+
+  HIR::UnsafeChecker ().go (hir);
+  HIR::ConstChecker ().go (hir);
+
+  if (saw_errors ())
+    return;
+
+  // do compile to gcc generic
+  Compile::Context ctx (backend);
+  Compile::CompileCrate::Compile (hir, &ctx);
+
+  // we can't do static analysis if there are errors to worry about
+  if (!saw_errors ())
+    {
+      // lints
+      Analysis::ScanDeadcode::Scan (hir);
+      Analysis::UnusedVariables::Lint (ctx);
+
+      // metadata
+      bool specified_emit_metadata
+	= flag_rust_embed_metadata || options.metadata_output_path_set ();
+      if (!specified_emit_metadata)
+	{
+	  Metadata::PublicInterface::ExportTo (
+	    hir, Metadata::PublicInterface::expected_metadata_filename ());
+	}
+      else
+	{
+	  if (flag_rust_embed_metadata)
+	    Metadata::PublicInterface::Export (hir);
+	  if (options.metadata_output_path_set ())
+	    Metadata::PublicInterface::ExportTo (
+	      hir, options.get_metadata_output ());
+	}
+    }
+
+  // pass to GCC middle-end
+  ctx.write_to_backend ();
+}
+
+void
+Session::register_plugins (AST::Crate &crate ATTRIBUTE_UNUSED)
+{
+  rust_debug ("ran register_plugins (with no body)");
+}
+
+// TODO: move somewhere else
+bool
+contains_name (const AST::AttrVec &attrs, std::string name)
+{
+  for (const auto &attr : attrs)
+    {
+      if (attr.get_path () == name)
+	return true;
+    }
+
+  return false;
+}
+
+void
+Session::injection (AST::Crate &crate)
+{
+  rust_debug ("started injection");
+
+  // lint checks in future maybe?
+
+  // register builtin macros
+  /* In rustc, builtin macros are divided into 3 categories depending on use -
+   * "bang" macros, "attr" macros, and "derive" macros. I think the meanings
+   * of these categories should be fairly obvious to anyone who has used rust.
+   * Builtin macro list by category: Bang
+   *      - asm
+   *      - assert
+   *      - cfg
+   *      - column
+   *      - compile_error
+   *      - concat_idents
+   *      - concat
+   *      - env
+   *      - file
+   *      - format_args_nl
+   *      - format_args
+   *      - global_asm
+   *      - include_bytes
+   *      - include_str
+   *      - include
+   *      - line
+   *      - log_syntax
+   *      - module_path
+   *      - option_env
+   *      - stringify
+   *      - trace_macros
+   *  Attr
+   *      - bench
+   *      - global_allocator
+   *      - test
+   *      - test_case
+   *  Derive
+   *      - Clone
+   *      - Copy
+   *      - Debug
+   *      - Default
+   *      - Eq
+   *      - Hash
+   *      - Ord
+   *      - PartialEq
+   *      - PartialOrd
+   *      - RustcDecodable
+   *      - RustcEncodable
+   * rustc also has a "quote" macro that is defined differently and is
+   * supposedly not stable so eh. */
+  /* TODO: actually implement injection of these macros. In particular, derive
+   * macros, cfg, and test should be prioritised since they seem to be used
+   * the most. */
+
+  // crate injection
+  std::vector<std::string> names;
+  if (contains_name (crate.inner_attrs, "no_core"))
+    {
+      // no prelude
+      injected_crate_name = "";
+    }
+  else if (contains_name (crate.inner_attrs, "no_std"))
+    {
+      names.push_back ("core");
+
+      if (!contains_name (crate.inner_attrs, "compiler_builtins"))
+	{
+	  names.push_back ("compiler_builtins");
+	}
+
+      injected_crate_name = "core";
+    }
+  else
+    {
+      names.push_back ("std");
+
+      injected_crate_name = "std";
+    }
+
+  // reverse iterate through names to insert crate items in "forward" order at
+  // beginning of crate
+  for (auto it = names.rbegin (); it != names.rend (); ++it)
+    {
+      // create "macro use" attribute for use on extern crate item to enable
+      // loading macros from it
+      AST::Attribute attr (AST::SimplePath::from_str ("macro_use", Location ()),
+			   nullptr);
+
+      // create "extern crate" item with the name
+      std::unique_ptr<AST::ExternCrate> extern_crate (
+	new AST::ExternCrate (*it, AST::Visibility::create_error (),
+			      {std::move (attr)},
+			      Linemap::unknown_location ()));
+
+      // insert at beginning
+      // crate.items.insert (crate.items.begin (), std::move (extern_crate));
+    }
+
+  // create use tree path
+  // prelude is injected_crate_name
+  // FIXME: Once we do want to include the standard library, add the prelude
+  // use item
+  // std::vector<AST::SimplePathSegment> segments
+  //   = {AST::SimplePathSegment (injected_crate_name, Location ()),
+  //      AST::SimplePathSegment ("prelude", Location ()),
+  //      AST::SimplePathSegment ("v1", Location ())};
+  // // create use tree and decl
+  // std::unique_ptr<AST::UseTreeGlob> use_tree (
+  //   new AST::UseTreeGlob (AST::UseTreeGlob::PATH_PREFIXED,
+  //     		  AST::SimplePath (std::move (segments)), Location ()));
+  // AST::Attribute prelude_attr (AST::SimplePath::from_str ("prelude_import",
+  //     						  Location ()),
+  //     		       nullptr);
+  // std::unique_ptr<AST::UseDeclaration> use_decl (
+  //   new AST::UseDeclaration (std::move (use_tree),
+  //     		     AST::Visibility::create_error (),
+  //     		     {std::move (prelude_attr)}, Location ()));
+
+  // crate.items.insert (crate.items.begin (), std::move (use_decl));
+
+  /* TODO: potentially add checking attribute crate type? I can't figure out
+   * what this does currently comment says "Unconditionally collect crate
+   * types from attributes to make them used", which presumably refers to
+   * checking the linkage info by "crate_type". It also seems to ensure that
+   * an invalid crate type is not specified, so maybe just do that. Valid
+   * crate types: bin lib dylib staticlib cdylib rlib proc-macro */
+
+  // this crate type will have options affecting the metadata ouput
+
+  rust_debug ("finished injection");
+}
+
+void
+Session::expansion (AST::Crate &crate)
+{
+  rust_debug ("started expansion");
+
+  /* rustc has a modification to windows PATH temporarily here, which may end
+   * up being required */
+
+  // create macro expansion config?
+  // if not, would at least have to configure recursion_limit
+  ExpansionCfg cfg;
+
+  // create extctxt? from parse session, cfg, and resolver?
+  /* expand by calling cxtctxt object's monotonic_expander's expand_crate
+   * method. */
+  MacroExpander expander (crate, cfg, *this);
+  expander.expand_crate ();
+
+  // error reporting - check unused macros, get missing fragment specifiers
+
+  // build test harness
+
+  // ast validation (also with proc macro decls)
+
+  // maybe create macro crate if not rustdoc
+
+  rust_debug ("finished expansion");
+}
+
+void
+Session::dump_lex (Parser<Lexer> &parser) const
+{
+  std::ofstream out;
+  out.open (kLexDumpFile);
+  if (out.fail ())
+    {
+      rust_error_at (Linemap::unknown_location (), "cannot open %s:%m; ignored",
+		     kLexDumpFile);
+      return;
+    }
+
+  // TODO: rewrite lexer dump or something so that it allows for the crate
+  // to already be parsed
+  parser.debug_dump_lex_output (out);
+  out.close ();
+}
+
+void
+Session::dump_ast (Parser<Lexer> &parser, AST::Crate &crate) const
+{
+  std::ofstream out;
+  out.open (kASTDumpFile);
+  if (out.fail ())
+    {
+      rust_error_at (Linemap::unknown_location (), "cannot open %s:%m; ignored",
+		     kASTDumpFile);
+      return;
+    }
+
+  parser.debug_dump_ast_output (crate, out);
+  out.close ();
+}
+
+void
+Session::dump_ast_pretty (AST::Crate &crate) const
+{
+  std::ofstream out;
+  out.open (kASTPrettyDumpFile);
+  if (out.fail ())
+    {
+      rust_error_at (Linemap::unknown_location (), "cannot open %s:%m; ignored",
+		     kASTDumpFile);
+      return;
+    }
+
+  AST::Dump (out).go (crate);
+
+  out.close ();
+}
+
+void
+Session::dump_ast_expanded (Parser<Lexer> &parser, AST::Crate &crate) const
+{
+  std::ofstream out;
+  out.open (kASTExpandedDumpFile);
+  if (out.fail ())
+    {
+      rust_error_at (Linemap::unknown_location (), "cannot open %s:%m; ignored",
+		     kASTExpandedDumpFile);
+      return;
+    }
+
+  parser.debug_dump_ast_output (crate, out);
+  out.close ();
+}
+
+void
+Session::dump_hir (HIR::Crate &crate) const
+{
+  std::ofstream out;
+  out.open (kHIRDumpFile);
+  if (out.fail ())
+    {
+      rust_error_at (Linemap::unknown_location (), "cannot open %s:%m; ignored",
+		     kHIRDumpFile);
+      return;
+    }
+
+  out << crate.as_string ();
+  out.close ();
+}
+
+void
+Session::dump_hir_pretty (HIR::Crate &crate) const
+{
+  std::ofstream out;
+  out.open (kHIRPrettyDumpFile);
+  if (out.fail ())
+    {
+      rust_error_at (Linemap::unknown_location (), "cannot open %s:%m; ignored",
+		     kHIRPrettyDumpFile);
+      return;
+    }
+
+  HIR::Dump (out).go (crate);
+  out.close ();
+}
+
+void
+Session::dump_type_resolution (HIR::Crate &hir) const
+{
+  std::ofstream out;
+  out.open (kHIRTypeResolutionDumpFile);
+  if (out.fail ())
+    {
+      rust_error_at (Linemap::unknown_location (), "cannot open %s:%m; ignored",
+		     kHIRTypeResolutionDumpFile);
+      return;
+    }
+
+  Resolver::TypeResolverDump::go (hir, out);
+  out.close ();
+}
+
+// imports
+
+NodeId
+Session::load_extern_crate (const std::string &crate_name, Location locus)
+{
+  // has it already been loaded?
+  CrateNum found_crate_num = UNKNOWN_CREATENUM;
+  bool found = mappings->lookup_crate_name (crate_name, found_crate_num);
+  if (found)
+    {
+      NodeId resolved_node_id = UNKNOWN_NODEID;
+      bool resolved
+	= mappings->crate_num_to_nodeid (found_crate_num, resolved_node_id);
+      rust_assert (resolved);
+
+      return resolved_node_id;
+    }
+
+  std::string relative_import_path = "";
+  Import::Stream *s
+    = Import::open_package (crate_name, locus, relative_import_path);
+  if (s == NULL)
+    {
+      rust_error_at (locus, "failed to locate crate %<%s%>",
+		     crate_name.c_str ());
+      return UNKNOWN_NODEID;
+    }
+
+  Imports::ExternCrate extern_crate (*s);
+  bool ok = extern_crate.load (locus);
+  if (!ok)
+    {
+      rust_error_at (locus, "failed to load crate metadata");
+      return UNKNOWN_NODEID;
+    }
+
+  // ensure the current vs this crate name don't collide
+  const std::string current_crate_name = mappings->get_current_crate_name ();
+  if (current_crate_name.compare (extern_crate.get_crate_name ()) == 0)
+    {
+      rust_error_at (locus, "current crate name %<%s%> collides with this",
+		     current_crate_name.c_str ());
+      return UNKNOWN_NODEID;
+    }
+
+  // setup mappings
+  CrateNum saved_crate_num = mappings->get_current_crate ();
+  CrateNum crate_num
+    = mappings->get_next_crate_num (extern_crate.get_crate_name ());
+  mappings->set_current_crate (crate_num);
+
+  // then lets parse this as a 2nd crate
+  Lexer lex (extern_crate.get_metadata ());
+  Parser<Lexer> parser (lex);
+  std::unique_ptr<AST::Crate> metadata_crate = parser.parse_crate ();
+  AST::Crate &parsed_crate
+    = mappings->insert_ast_crate (std::move (metadata_crate), crate_num);
+
+  // name resolve it
+  Resolver::NameResolution::Resolve (parsed_crate);
+
+  // perform hir lowering
+  std::unique_ptr<HIR::Crate> lowered
+    = HIR::ASTLowering::Resolve (parsed_crate);
+  HIR::Crate &hir = mappings->insert_hir_crate (std::move (lowered));
+
+  // perform type resolution
+  Resolver::TypeResolution::Resolve (hir);
+
+  // always restore the crate_num
+  mappings->set_current_crate (saved_crate_num);
+
+  return parsed_crate.get_node_id ();
+}
+//
+
+void
+TargetOptions::dump_target_options () const
+{
+  std::ofstream out;
+  out.open (kTargetOptionsDumpFile);
+  if (out.fail ())
+    {
+      rust_error_at (Linemap::unknown_location (), "cannot open %s:%m; ignored",
+		     kTargetOptionsDumpFile);
+      return;
+    }
+
+  if (features.empty ())
+    {
+      out << "No target options available!\n";
+    }
+
+  for (const auto &pairs : features)
+    {
+      for (const auto &value : pairs.second)
+	out << pairs.first + ": \"" + value + "\"\n";
+
+      if (pairs.second.empty ())
+	out << pairs.first + "\n";
+    }
+
+  out.close ();
+}
+
+void
+TargetOptions::init_derived_values ()
+{
+  // enable derived values based on target families
+  if (has_key_value_pair ("target_family", "unix"))
+    insert_key ("unix");
+  if (has_key_value_pair ("target_family", "windows"))
+    insert_key ("windows");
+
+  // implicitly enable features - this should not be required in general
+  if (has_key_value_pair ("target_feature", "aes"))
+    enable_implicit_feature_reqs ("aes");
+  if (has_key_value_pair ("target_feature", "avx"))
+    enable_implicit_feature_reqs ("sse4.2");
+  if (has_key_value_pair ("target_feature", "avx2"))
+    enable_implicit_feature_reqs ("avx");
+  if (has_key_value_pair ("target_feature", "pclmulqdq"))
+    enable_implicit_feature_reqs ("sse2");
+  if (has_key_value_pair ("target_feature", "sha"))
+    enable_implicit_feature_reqs ("sse2");
+  if (has_key_value_pair ("target_feature", "sse2"))
+    enable_implicit_feature_reqs ("sse");
+  if (has_key_value_pair ("target_feature", "sse3"))
+    enable_implicit_feature_reqs ("sse2");
+  if (has_key_value_pair ("target_feature", "sse4.1"))
+    enable_implicit_feature_reqs ("sse3");
+  if (has_key_value_pair ("target_feature", "sse4.2"))
+    enable_implicit_feature_reqs ("sse4.1");
+  if (has_key_value_pair ("target_feature", "ssse3"))
+    enable_implicit_feature_reqs ("sse3");
+}
+
+void
+TargetOptions::enable_implicit_feature_reqs (std::string feature)
+{
+  if (feature == "aes")
+    enable_implicit_feature_reqs ("sse2");
+  else if (feature == "avx")
+    enable_implicit_feature_reqs ("sse4.2");
+  else if (feature == "avx2")
+    enable_implicit_feature_reqs ("avx");
+  else if (feature == "fma")
+    enable_implicit_feature_reqs ("avx");
+  else if (feature == "pclmulqdq")
+    enable_implicit_feature_reqs ("sse2");
+  else if (feature == "sha")
+    enable_implicit_feature_reqs ("sse2");
+  else if (feature == "sse2")
+    enable_implicit_feature_reqs ("sse");
+  else if (feature == "sse3")
+    enable_implicit_feature_reqs ("sse2");
+  else if (feature == "sse4.1")
+    enable_implicit_feature_reqs ("sse3");
+  else if (feature == "sse4.2")
+    enable_implicit_feature_reqs ("sse4.1");
+  else if (feature == "ssse3")
+    enable_implicit_feature_reqs ("sse3");
+
+  if (!has_key_value_pair ("target_feature", feature))
+    {
+      insert_key_value_pair ("target_feature", feature);
+
+      rust_debug ("had to implicitly enable feature '%s'!", feature.c_str ());
+    }
+}
+
+// NOTEs:
+/* mrustc compile pipeline:
+ *  - target load (pass target spec to parser?)
+ *  - parse (convert source to AST)
+ *  - load crates (load any explicitly mentioned extern crates [not all of
+ * them])
+ *  - expand (AST transformations from attributes and macros, loads remaining
+ * extern crates [std/core and any triggered by macro expansion])
+ *  - implicit crates (test harness, allocator crate, panic crate)
+ *  - resolve use (annotate every 'use' item with source [supposedly handles
+ * nasty recursion])
+ *  - resolve index (generate index of visible items for every module [avoids
+ * recursion in next pass])
+ *  - resolve absolute (resolve all paths into either variable names
+ * [types/values] or absolute paths)
+ *  - HIR lower (convert modified AST to simpler HIR [both expressions and
+ * module tree])
+ *  - resolve type aliases (replace any usages of type aliases with actual
+ * type [except associated types])
+ *  - resolve bind (iterate HIR tree and set binding annotations on all
+ * concrete types [avoids path lookups later])
+ *  - resolve HIR markings (generate "markings" [e.g. for Copy/Send/Sync/...]
+ * for all types
+ *  - sort impls (small pass - sort impls into groups)
+ *  - resolve UFCS outer (determine source trait for all top-level <T>::Type
+ * [qualified] paths)
+ *  - resolve UFCS paths (do the same, but include for exprs this time. also
+ * normalises results of previous pass [expanding known associated types])
+ *  - constant evaluate (evaluate all constants)
+ *  - typecheck outer (checks impls are sane)
+ *  - typecheck expressions (resolve and check types for all exprs)
+ *  - expand HIR annotate (annotate how exprs are used - used for closure
+ * extractions and reborrows)
+ *  - expand HIR closures (extract closures into structs implementing Fn*
+ * traits)
+ *  - expand HIR vtables (generate vtables for types with dyn dispatch)
+ *  - expand HIR calls (converts method and callable calls into explicit
+ * function calls)
+ *  - expand HIR reborrows (apply reborrow rules [taking '&mut *v' instead of
+ * 'v'])
+ *  - expand HIR erasedtype (replace all erased types 'impl Trait' with the
+ * true type)
+ *  - typecheck expressions (validate - double check that previous passes
+ * haven't broke type system rules)
+ *  - lower MIR (convert HIR exprs into a control-flow graph [MIR])
+ *  - MIR validate (check that the generated MIR is consistent)
+ *  - MIR cleanup (perform various transformations on MIR - replace reads of
+ * const items with the item itself; convert casts to unsized types into
+ * 'MakeDst' operations)
+ *  - MIR optimise (perform various simple optimisations on the MIR - constant
+ * propagation, dead code elimination, borrow elimination, some inlining)
+ *  - MIR validate PO (re-validate the MIR)
+ *  - MIR validate full (optionally: perform expensive state-tracking
+ * validation on MIR)
+ *  - trans enumerate (enumerate all items needed for code generation,
+ * primarily types used for generics)
+ *  - trans auto impls (create magic trait impls as enumerated in previous
+ * pass)
+ *  - trans monomorph (generate monomorphised copies of all functions [with
+ * generics replaced with real types])
+ *  - MIR optimise inline (run optimisation again, this time with full type
+ * info [primarily for inlining])
+ *  - HIR serialise (write out HIR dump [module tree and generic/inline MIR])
+ *  - trans codegen (generate final output file: emit C source file and call C
+ * compiler) */
+
+/* rustc compile pipeline (basic, in way less detail):
+ *  - parse input (parse .rs to AST)
+ *  - name resolution, macro expansion, and configuration (process AST
+ * recursively, resolving paths, expanding macros, processing #[cfg] nodes
+ * [i.e. maybe stripping stuff from AST])
+ *  - lower to HIR
+ *  - type check and other analyses (e.g. privacy checking)
+ *  - lower to MIR and post-processing (and do stuff like borrow checking)
+ *  - translation to LLVM IR and LLVM optimisations (produce the .o files)
+ *  - linking (link together .o files) */
+
+/* Pierced-together rustc compile pipeline (from source):
+ *  - parse input (parse file to crate)
+ *  - register plugins (attributes injection, set various options, register
+ * lints, load plugins)
+ *  - expansion/configure and expand (initial 'cfg' processing, 'loading
+ * compiler plugins', syntax expansion, secondary 'cfg' expansion, synthesis
+ * of a test harness if required, injection of any std lib dependency and
+ * prelude, and name resolution) - actually documented inline
+ *      - seeming pierced-together order: pre-AST expansion lint checks,
+ * registering builtin macros, crate injection, then expand all macros, then
+ * maybe build test harness, AST validation, maybe create a macro crate (if
+ * not rustdoc), name resolution, complete gated feature checking, add all
+ * buffered lints
+ *  - create global context (lower to HIR)
+ *  - analysis on global context (HIR optimisations? create MIR?)
+ *  - code generation
+ *  - link */
+} // namespace Rust
+
+#if CHECKING_P
+namespace selftest {
+void
+rust_crate_name_validation_test (void)
+{
+  auto error = Rust::Error (Location (), std::string ());
+  ASSERT_TRUE (Rust::validate_crate_name ("example", error));
+  ASSERT_TRUE (Rust::validate_crate_name ("abcdefg_1234", error));
+  ASSERT_TRUE (Rust::validate_crate_name ("1", error));
+  // FIXME: The next test does not pass as of current implementation
+  // ASSERT_TRUE (Rust::CompileOptions::validate_crate_name ("惊吓"));
+  // NOTE: - is not allowed in the crate name ...
+
+  ASSERT_FALSE (Rust::validate_crate_name ("abcdefg-1234", error));
+  ASSERT_FALSE (Rust::validate_crate_name ("a+b", error));
+  ASSERT_FALSE (Rust::validate_crate_name ("/a+b/", error));
+
+  /* Tests for crate name inference */
+  ASSERT_EQ (Rust::infer_crate_name ("c.rs"), "c");
+  // NOTE: ... but - is allowed when in the filename
+  ASSERT_EQ (Rust::infer_crate_name ("a-b.rs"), "a_b");
+  ASSERT_EQ (Rust::infer_crate_name ("book.rs.txt"), "book.rs");
+#if defined(HAVE_DOS_BASED_FILE_SYSTEM)
+  ASSERT_EQ (Rust::infer_crate_name ("a\\c\\a-b.rs"), "a_b");
+#else
+  ASSERT_EQ (Rust::infer_crate_name ("a/c/a-b.rs"), "a_b");
+#endif
+}
+} // namespace selftest
+#endif // CHECKING_P
diff --git a/gcc/rust/rust-session-manager.h b/gcc/rust/rust-session-manager.h
new file mode 100644
index 00000000000..99dd107239b
--- /dev/null
+++ b/gcc/rust/rust-session-manager.h
@@ -0,0 +1,358 @@ 
+// 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-session-manager.h"
+
+#ifndef RUST_SESSION_MANAGER_H
+#define RUST_SESSION_MANAGER_H
+
+#include "rust-linemap.h"
+#include "rust-backend.h"
+#include "rust-hir-map.h"
+#include "safe-ctype.h"
+
+#include "config.h"
+#include "rust-system.h"
+#include "coretypes.h"
+#include "options.h"
+
+namespace Rust {
+// parser forward decl
+template <typename ManagedTokenSource> class Parser;
+class Lexer;
+// crate forward decl
+namespace AST {
+struct Crate;
+}
+// crate forward decl
+namespace HIR {
+struct Crate;
+}
+
+/* Data related to target, most useful for conditional compilation and
+ * whatever. */
+struct TargetOptions
+{
+  /* TODO: maybe make private and access through helpers to allow changes to
+   * impl */
+  std::unordered_map<std::string, std::unordered_set<std::string> > features;
+
+public:
+  // Returns whether a key is defined in the feature set.
+  bool has_key (std::string key) const
+  {
+    return features.find (key) != features.end ();
+  }
+
+  // Returns whether a key exists with the given value in the feature set.
+  bool has_key_value_pair (std::string key, std::string value) const
+  {
+    auto it = features.find (key);
+    if (it != features.end ())
+      {
+	auto set = it->second;
+	auto it2 = set.find (value);
+	if (it2 != set.end ())
+	  return true;
+      }
+    return false;
+  }
+
+  /* Returns the singular value from the key, or if the key has multiple, an
+   * empty string. */
+  std::string get_singular_value (std::string key) const
+  {
+    auto it = features.find (key);
+    if (it != features.end ())
+      {
+	auto set = it->second;
+	if (set.size () == 1)
+	  return *set.begin ();
+      }
+    return "";
+  }
+
+  /* Returns all values associated with a key (including none), or an empty
+   * set if no key is found. */
+  std::unordered_set<std::string> get_values_for_key (std::string key) const
+  {
+    auto it = features.find (key);
+    if (it != features.end ())
+      return it->second;
+    return {};
+  }
+
+  /* Inserts a key (no value) into the feature set. This will do nothing if
+   * the key already exists. This returns whether the insertion was successful
+   * (i.e. whether key already existed). */
+  bool insert_key (std::string key)
+  {
+    return features
+      .insert (std::make_pair (key, std::unordered_set<std::string> ()))
+      .second;
+  }
+
+  // Inserts a key-value pair into the feature set.
+  void insert_key_value_pair (std::string key, std::string value)
+  {
+    auto existing_set = get_values_for_key (key);
+    existing_set.insert (std::move (value));
+    features[std::move (key)] = std::move (existing_set);
+  }
+
+  // Dump all target options to stderr.
+  void dump_target_options () const;
+
+  /* Creates derived values and implicit enables after all target info is
+   * added (e.g. "unix"). */
+  void init_derived_values ();
+
+  /* Enables all requirements for the feature given, and will enable feature
+   * itself if not enabled. */
+  void enable_implicit_feature_reqs (std::string feature);
+
+  /* According to reference, Rust uses either multi-map key-values or just
+   * values (although values may be aliases for a key-value value). This seems
+   * like overkill. Thus, depending on whether the attributes used in cfg are
+   * fixed or not, I think I'll either put each non-multimap "key-value" as a
+   * separate field and have the multimap "key-values" in a regular map for
+   * that one key, or actually use a multimap.
+   *
+   * rustc itself uses a set of key-value tuples where the second tuple
+   * element is optional. This gets rid of the requirement to make a
+   * multi-map, I guess, but seems like it might make search slow (unless all
+   * "is defined"-only ones have empty string as second element). */
+  /* cfg attributes:
+   * - target_arch: single value
+   * - target_feature: multiple values possible
+   * - target_os: single value
+   * - target_family: single value (or no value?)
+   * - unix: set when target_family = "unix"
+   * - windows: set when target_family = "windows"
+   *  - if these are just syntactic sugar, then maybe have a separate set or
+   * map for this kind of stuff
+   * - target_env: set when needed for disambiguation about ABI - usually
+   * empty string for GNU, complicated
+   *  - seems to be a single value (if any)
+   * - target_endian: single value; "little" or "big"
+   * - target_pointer_width: single value, "32" for 32-bit pointers, etc.
+   * - target_vendor, single value
+   * - test: set when testing is being done
+   *  - again, seems similar to a "is defined" rather than "is equal to" like
+   * unix
+   * - debug_assertions: seems to "is defined"
+   * - proc_macro: no idea, bad docs. seems to be boolean, so maybe "is
+   * defined"
+   */
+};
+
+// Defines compiler options (e.g. dump, etc.).
+struct CompileOptions
+{
+  enum DumpOption
+  {
+    LEXER_DUMP,
+    PARSER_AST_DUMP,
+    AST_DUMP_PRETTY,
+    REGISTER_PLUGINS_DUMP,
+    INJECTION_DUMP,
+    EXPANSION_DUMP,
+    RESOLUTION_DUMP,
+    TARGET_OPTION_DUMP,
+    HIR_DUMP,
+    HIR_DUMP_PRETTY,
+    TYPE_RESOLUTION_DUMP,
+  };
+
+  std::set<DumpOption> dump_options;
+
+  /* configuration options - actually useful for conditional compilation and
+   * whatever data related to target arch, features, os, family, env, endian,
+   * pointer width, vendor */
+  TargetOptions target_data;
+  std::string crate_name;
+  bool crate_name_set_manually = false;
+  bool enable_test = false;
+  bool debug_assertions = false;
+  bool proc_macro = false;
+  std::string metadata_output_path;
+
+  enum class Edition
+  {
+    E2015 = 0,
+    E2018,
+    E2021,
+  } edition
+    = Edition::E2015;
+
+  bool dump_option_enabled (DumpOption option) const
+  {
+    return dump_options.find (option) != dump_options.end ();
+  }
+
+  void enable_dump_option (DumpOption option) { dump_options.insert (option); }
+
+  void enable_all_dump_options ()
+  {
+    enable_dump_option (DumpOption::LEXER_DUMP);
+    enable_dump_option (DumpOption::PARSER_AST_DUMP);
+    enable_dump_option (DumpOption::AST_DUMP_PRETTY);
+    enable_dump_option (DumpOption::REGISTER_PLUGINS_DUMP);
+    enable_dump_option (DumpOption::INJECTION_DUMP);
+    enable_dump_option (DumpOption::EXPANSION_DUMP);
+    enable_dump_option (DumpOption::RESOLUTION_DUMP);
+    enable_dump_option (DumpOption::TARGET_OPTION_DUMP);
+    enable_dump_option (DumpOption::HIR_DUMP);
+    enable_dump_option (DumpOption::HIR_DUMP_PRETTY);
+    enable_dump_option (DumpOption::TYPE_RESOLUTION_DUMP);
+  }
+
+  void set_crate_name (std::string name)
+  {
+    rust_assert (!name.empty ());
+
+    crate_name = std::move (name);
+  }
+
+  const std::string &get_crate_name () const
+  {
+    rust_assert (!crate_name.empty ());
+    return crate_name;
+  }
+
+  void set_edition (int raw_edition)
+  {
+    edition = static_cast<Edition> (raw_edition);
+  }
+
+  const Edition &get_edition () { return edition; }
+
+  void set_metadata_output (const std::string &path)
+  {
+    metadata_output_path = path;
+  }
+
+  const std::string &get_metadata_output () const
+  {
+    return metadata_output_path;
+  }
+
+  bool metadata_output_path_set () const
+  {
+    return !metadata_output_path.empty ();
+  }
+};
+
+/* Defines a compiler session. This is for a single compiler invocation, so
+ * potentially includes parsing multiple crates. */
+struct Session
+{
+  CompileOptions options;
+  /* This should really be in a per-crate storage area but it is wiped with
+   * every file so eh. */
+  std::string injected_crate_name;
+
+  /* extra files get included during late stages of compilation (e.g. macro
+   * expansion) */
+  std::vector<std::string> extra_files;
+
+  // backend wrapper to GCC GENERIC
+  Backend *backend;
+
+  // backend linemap
+  Linemap *linemap;
+
+  // mappings
+  Analysis::Mappings *mappings;
+
+public:
+  /* Get a reference to the static session instance */
+  static Session &get_instance ();
+
+  Session () = default;
+  ~Session () = default;
+
+  /* This initializes the compiler session. Corresponds to langhook
+   * grs_langhook_init(). Note that this is called after option handling. */
+  void init ();
+
+  // delete those constructors so we don't access the singleton in any
+  // other way than via `get_instance()`
+  Session (Session const &) = delete;
+  void operator= (Session const &) = delete;
+
+  bool handle_option (enum opt_code code, const char *arg, HOST_WIDE_INT value,
+		      int kind, location_t loc,
+		      const struct cl_option_handlers *handlers);
+  void handle_input_files (int num_files, const char **files);
+  void init_options ();
+  void handle_crate_name (const AST::Crate &parsed_crate);
+
+  /* This function saves the filename data into the session manager using the
+   * `move` semantics, and returns a C-style string referencing the input
+   * std::string */
+  inline const char *include_extra_file (std::string filename)
+  {
+    extra_files.push_back (std::move (filename));
+    return extra_files.back ().c_str ();
+  }
+
+  NodeId load_extern_crate (const std::string &crate_name, Location locus);
+
+private:
+  void compile_crate (const char *filename);
+  bool enable_dump (std::string arg);
+
+  void dump_lex (Parser<Lexer> &parser) const;
+  void dump_ast (Parser<Lexer> &parser, AST::Crate &crate) const;
+  void dump_ast_pretty (AST::Crate &crate) const;
+  void dump_ast_expanded (Parser<Lexer> &parser, AST::Crate &crate) const;
+  void dump_hir (HIR::Crate &crate) const;
+  void dump_hir_pretty (HIR::Crate &crate) const;
+  void dump_type_resolution (HIR::Crate &crate) const;
+
+  // pipeline stages - TODO maybe move?
+  /* Register plugins pipeline stage. TODO maybe move to another object?
+   * Currently dummy stage. In future will handle attribute injection
+   * (top-level inner attribute creation from command line arguments), setting
+   * options maybe, registering lints maybe, loading plugins maybe. */
+  void register_plugins (AST::Crate &crate);
+
+  /* Injection pipeline stage. TODO maybe move to another object? Maybe have
+   * some lint checks (in future, obviously), register builtin macros, crate
+   * injection. */
+  void injection (AST::Crate &crate);
+
+  /* Expansion pipeline stage. TODO maybe move to another object? Expands all
+   * macros, maybe build test harness in future, AST validation, maybe create
+   * macro crate (if not rustdoc).*/
+  void expansion (AST::Crate &crate);
+
+  // handle cfg_option
+  bool handle_cfg_option (std::string &data);
+};
+
+} // namespace Rust
+
+#if CHECKING_P
+namespace selftest {
+extern void
+rust_crate_name_validation_test (void);
+}
+#endif // CHECKING_P
+
+#endif