compiler: revamp scheme for ordering calls to import init fcns.

    
    Switch to a new method for determining the order in which import init
    functions are invoked: build an init fcn dependence DAG and walk the DAG
    to rewrite/adjust priorities to account for discrepancies introduced by
    "go test".
    
    This patch includes a change to the export data format generated
    by gccgo. Older versions of gccgo will not be able to read object files
    produced by a newer gccgo, but the new gcc will still be able to read
    old object files.
    
    Fixes golang/go#15738.
    
    Reviewed-on: https://go-review.googlesource.com/25301

From-SVN: r239708

1 files changed, 42 insertions, 11 deletions

diff --git a/gcc/go/gofrontend/export.h b/gcc/go/gofrontend/export.h
index c3972d8..ee61d27 100644
--- a/gcc/go/gofrontend/export.h
+++ b/gcc/go/gofrontend/export.h
@@ -15,6 +15,7 @@ class Import_init;
 class Bindings;
 class Type;
 class Package;
+class Import_init_set;
 
 // Codes used for the builtin types.  These are all negative to make
 // them easily distinct from the codes assigned by Export::write_type.
@@ -47,6 +48,17 @@ enum Builtin_code
   SMALLEST_BUILTIN_CODE = -21
 };
 
+// Export data version number. New export data is written with the
+// "current" version, but there is support for reading files with
+// older version export data (at least for now).
+
+enum Export_data_version {
+  EXPORT_FORMAT_UNKNOWN = 0,
+  EXPORT_FORMAT_V1 = 1,
+  EXPORT_FORMAT_V2 = 2,
+  EXPORT_FORMAT_CURRENT = EXPORT_FORMAT_V2
+};
+
 // This class manages exporting Go declarations.  It handles the main
 // loop of exporting.  A pointer to this class is also passed to the
 // various specific export implementations.
@@ -103,12 +115,15 @@ class Export : public String_dump
 
   Export(Stream*);
 
-  // The magic code for version 1 export data.
-  static const int v1_magic_len = 4;
-  static const char v1_magic[v1_magic_len];
+  // Size of export data magic string (which includes version number).
+  static const int magic_len = 4;
 
-  // The length of the v1 checksum string.
-  static const int v1_checksum_len = 20;
+  // Magic strings (current version and older v1 version).
+  static const char cur_magic[magic_len];
+  static const char v1_magic[magic_len];
+
+  // The length of the checksum string.
+  static const int checksum_len = 20;
 
   // Register the builtin types.
   void
@@ -119,7 +134,6 @@ class Export : public String_dump
   // is nothing to export, this->stream_->write will not be called.
   // PREFIX is the package prefix.  PKGPATH is the package path.
   // Only one of PREFIX and PKGPATH will be non-empty.
-  // PACKAGE_PRIORITY is the priority to use for this package.
   // PACKAGES is all the packages we have seen.
   // IMPORTS is the explicitly imported packages.
   // IMPORT_INIT_FN is the name of the import initialization function
@@ -130,11 +144,10 @@ class Export : public String_dump
   export_globals(const std::string& package_name,
 		 const std::string& prefix,
 		 const std::string& pkgpath,
-		 int package_priority,
 		 const std::map<std::string, Package*>& packages,
 		 const std::map<std::string, Package*>& imports,
 		 const std::string& import_init_fn,
-		 const std::set<Import_init>& imported_init_fns,
+		 const Import_init_set& imported_init_fns,
 		 const Bindings* bindings);
 
   // Write a string to the export stream.
@@ -166,6 +179,14 @@ class Export : public String_dump
   void
   write_escape(std::string* note);
 
+  // Write an integer value.
+  void
+  write_int(int);
+
+  // Write an unsigned value.
+  void
+  write_unsigned(unsigned);
+
  private:
   Export(const Export&);
   Export& operator=(const Export&);
@@ -174,14 +195,24 @@ class Export : public String_dump
   void
   write_packages(const std::map<std::string, Package*>& packages);
 
+  typedef std::map<unsigned, std::set<unsigned> > Init_graph;
+
+  static void
+  add_init_graph_edge(Init_graph* init_graph, unsigned src, unsigned sink);
+
+  static void
+  populate_init_graph(Init_graph* init_graph,
+                      const Import_init_set& imported_init_fns,
+                      const std::map<std::string, unsigned>& init_idx);
+
   // Write out the imported packages.
   void
   write_imports(const std::map<std::string, Package*>& imports);
 
-  // Write out the imported initialization functions.
+  // Write out the imported initialization functions and init graph.
   void
-  write_imported_init_fns(const std::string& package_name, int priority,
-			  const std::string&, const std::set<Import_init>&);
+  write_imported_init_fns(const std::string& package_name,
+			  const std::string&, const Import_init_set&);
 
   // Register one builtin type.
   void