escape: Implement assign phase.

Implementation of the assign/connect phase.
    Statements containing expressions which alias local, parameter,
    and global objects are analyzed and the alias relationship between
    objects containing pointers are captured in a connection graph to
    summarize the assignments within a function.
    
    Reviewed-on: https://go-review.googlesource.com/18302

From-SVN: r237424

gcc/go/gofrontend/MERGE

@@ -1,4 +1,4 @@
-054ff1ece3dd5888a445efeaf3ae197b16d4186f
+f768153eb2a7a72587c9c0997955cdbbc70322d0
 
 The first line of this file holds the git revision number of the last
 merge done from the gofrontend repository.

gcc/go/gofrontend/escape.h

@@ -206,7 +206,9 @@ class Node
   void
   set_encoding(int enc);
 
-  // Is this node a sink?
+  bool
+  is_big(Escape_context*) const;
+
   bool
   is_sink() const;
 
@@ -250,6 +252,11 @@ class Node
   static int
   max_encoding(int e, int etype);
 
+  // Return a modified encoding for an input parameter that flows into an
+  // output parameter.
+  static int
+  note_inout_flows(int e, int index, Level level);
+
  private:
   // The classification of this Node.
   Node_classification classification_;

gcc/go/gofrontend/gogo.h

@@ -2578,7 +2578,7 @@ class Label
  public:
   Label(const std::string& name)
     : name_(name), location_(Linemap::unknown_location()), snapshot_(NULL),
-      refs_(), is_used_(false), blabel_(NULL)
+      refs_(), is_used_(false), blabel_(NULL), depth_(DEPTH_UNKNOWN)
   { }
 
   // Return the label's name.
@@ -2601,6 +2601,26 @@ class Label
   set_is_used()
   { this->is_used_ = true; }
 
+  // Return whether this label is looping.
+  bool
+  looping() const
+  { return this->depth_ == DEPTH_LOOPING; }
+
+  // Set this label as looping.
+  void
+  set_looping()
+  { this->depth_ = DEPTH_LOOPING; }
+
+  // Return whether this label is nonlooping.
+  bool
+  nonlooping() const
+  { return this->depth_ == DEPTH_NONLOOPING; }
+
+  // Set this label as nonlooping.
+  void
+  set_nonlooping()
+  { this->depth_ = DEPTH_NONLOOPING; }
+
   // Return the location of the definition.
   Location
   location() const
@@ -2660,6 +2680,16 @@ class Label
   is_dummy_label() const
   { return this->name_ == "_"; }
 
+  // A classification of a label's looping depth.
+  enum Loop_depth
+  {
+    DEPTH_UNKNOWN,
+    // A label never jumped to.
+    DEPTH_NONLOOPING,
+    // A label jumped to.
+    DEPTH_LOOPING
+  };
+
  private:
   // The name of the label.
   std::string name_;
@@ -2675,6 +2705,8 @@ class Label
   bool is_used_;
   // The backend representation.
   Blabel* blabel_;
+  // The looping depth of this label, for escape analysis.
+  Loop_depth depth_;
 };
 
 // An unnamed label.  These are used when lowering loops.

gcc/go/gofrontend/statements.cc

@@ -1793,40 +1793,6 @@ Statement::make_statement(Expression* expr, bool is_ignored)
   return new Expression_statement(expr, is_ignored);
 }
 
-// A block statement--a list of statements which may include variable
-// definitions.
-
-class Block_statement : public Statement
-{
- public:
-  Block_statement(Block* block, Location location)
-    : Statement(STATEMENT_BLOCK, location),
-      block_(block)
-  { }
-
- protected:
-  int
-  do_traverse(Traverse* traverse)
-  { return this->block_->traverse(traverse); }
-
-  void
-  do_determine_types()
-  { this->block_->determine_types(); }
-
-  bool
-  do_may_fall_through() const
-  { return this->block_->may_fall_through(); }
-
-  Bstatement*
-  do_get_backend(Translate_context* context);
-
-  void
-  do_dump_statement(Ast_dump_context*) const;
-
- private:
-  Block* block_;
-};
-
 // Convert a block to the backend representation of a statement.
 
 Bstatement*
@@ -2944,37 +2910,13 @@ Statement::make_continue_statement(Unnamed_label* label,
   return new Bc_statement(false, label, location);
 }
 
-// A goto statement.
+// Class Goto_statement.
 
-class Goto_statement : public Statement
+int
+Goto_statement::do_traverse(Traverse*)
 {
- public:
-  Goto_statement(Label* label, Location location)
-    : Statement(STATEMENT_GOTO, location),
-      label_(label)
-  { }
-
- protected:
-  int
-  do_traverse(Traverse*)
-  { return TRAVERSE_CONTINUE; }
-
-  void
-  do_check_types(Gogo*);
-
-  bool
-  do_may_fall_through() const
-  { return false; }
-
-  Bstatement*
-  do_get_backend(Translate_context*);
-
-  void
-  do_dump_statement(Ast_dump_context*) const;
-
- private:
-  Label* label_;
-};
+  return TRAVERSE_CONTINUE;
+}
 
 // Check types for a label.  There aren't any types per se, but we use
 // this to give an error if the label was never defined.
@@ -3016,35 +2958,21 @@ Statement::make_goto_statement(Label* label, Location location)
   return new Goto_statement(label, location);
 }
 
-// A goto statement to an unnamed label.
+// Class Goto_unnamed_statement.
 
-class Goto_unnamed_statement : public Statement
+int
+Goto_unnamed_statement::do_traverse(Traverse*)
 {
- public:
-  Goto_unnamed_statement(Unnamed_label* label, Location location)
-    : Statement(STATEMENT_GOTO_UNNAMED, location),
-      label_(label)
-  { }
+  return TRAVERSE_CONTINUE;
+}
 
- protected:
-  int
-  do_traverse(Traverse*)
-  { return TRAVERSE_CONTINUE; }
+// Convert the goto unnamed statement to the backend representation.
 
-  bool
-  do_may_fall_through() const
-  { return false; }
-
-  Bstatement*
-  do_get_backend(Translate_context* context)
-  { return this->label_->get_goto(context, this->location()); }
-
-  void
-  do_dump_statement(Ast_dump_context*) const;
-
- private:
-  Unnamed_label* label_;
-};
+Bstatement*
+Goto_unnamed_statement::do_get_backend(Translate_context* context)
+{
+  return this->label_->get_goto(context, this->location());
+}
 
 // Dump the AST representation for an unnamed goto statement
 
@@ -3109,32 +3037,27 @@ Statement::make_label_statement(Label* label, Location location)
   return new Label_statement(label, location);
 }
 
-// An unnamed label statement.
+// Class Unnamed_label_statement.
 
-class Unnamed_label_statement : public Statement
+Unnamed_label_statement::Unnamed_label_statement(Unnamed_label* label)
+  : Statement(STATEMENT_UNNAMED_LABEL, label->location()),
+    label_(label)
+{ }
+
+int
+Unnamed_label_statement::do_traverse(Traverse*)
 {
- public:
-  Unnamed_label_statement(Unnamed_label* label)
-    : Statement(STATEMENT_UNNAMED_LABEL, label->location()),
-      label_(label)
-  { }
+  return TRAVERSE_CONTINUE;
+}
 
- protected:
-  int
-  do_traverse(Traverse*)
-  { return TRAVERSE_CONTINUE; }
+// Get the backend definition for this unnamed label statement.
 
-  Bstatement*
-  do_get_backend(Translate_context* context)
-  { return this->label_->get_definition(context); }
+Bstatement*
+Unnamed_label_statement::do_get_backend(Translate_context* context)
+{
+  return this->label_->get_definition(context);
+}
 
-  void
-  do_dump_statement(Ast_dump_context*) const;
-
- private:
-  // The label.
-  Unnamed_label* label_;
-};
 
 // Dump the AST representation for an unnamed label definition statement.
 
@@ -5209,7 +5132,9 @@ For_statement::do_lower(Gogo*, Named_object*, Block* enclosing,
 
   b->set_end_location(end_loc);
 
-  return Statement::make_block_statement(b, loc);
+  Statement* bs = Statement::make_block_statement(b, loc);
+  bs->block_statement()->set_is_lowered_for_statement();
+  return bs;
 }
 
 // Return the break label, creating it if necessary.

gcc/go/gofrontend/statements.h

@@ -19,9 +19,13 @@ class Assignment_statement;
 class Temporary_statement;
 class Variable_declaration_statement;
 class Expression_statement;
+class Block_statement;
 class Return_statement;
 class Thunk_statement;
+class Goto_statement;
+class Goto_unnamed_statement;
 class Label_statement;
+class Unnamed_label_statement;
 class If_statement;
 class For_statement;
 class For_range_statement;
@@ -366,6 +370,12 @@ class Statement
     return this->convert<Expression_statement, STATEMENT_EXPRESSION>();
   }
 
+  // If this is an block statement, return it.  Otherwise return
+  // NULL.
+  Block_statement*
+  block_statement()
+  { return this->convert<Block_statement, STATEMENT_BLOCK>(); }
+
   // If this is a return statement, return it.  Otherwise return NULL.
   Return_statement*
   return_statement()
@@ -376,11 +386,26 @@ class Statement
   Thunk_statement*
   thunk_statement();
 
+  // If this is a goto statement, return it.  Otherwise return NULL.
+  Goto_statement*
+  goto_statement()
+  { return this->convert<Goto_statement, STATEMENT_GOTO>(); }
+
+  // If this is a goto_unnamed statement, return it.  Otherwise return NULL.
+  Goto_unnamed_statement*
+  goto_unnamed_statement()
+  { return this->convert<Goto_unnamed_statement, STATEMENT_GOTO_UNNAMED>(); }
+
   // If this is a label statement, return it.  Otherwise return NULL.
   Label_statement*
   label_statement()
   { return this->convert<Label_statement, STATEMENT_LABEL>(); }
 
+  // If this is an unnamed_label statement, return it.  Otherwise return NULL.
+  Unnamed_label_statement*
+  unnamed_label_statement()
+  { return this->convert<Unnamed_label_statement, STATEMENT_UNNAMED_LABEL>(); }
+
   // If this is an if statement, return it.  Otherwise return NULL.
   If_statement*
   if_statement()
@@ -762,6 +787,50 @@ class Expression_statement : public Statement
   bool is_ignored_;
 };
 
+// A block statement--a list of statements which may include variable
+// definitions.
+
+class Block_statement : public Statement
+{
+ public:
+  Block_statement(Block* block, Location location)
+    : Statement(STATEMENT_BLOCK, location),
+      block_(block), is_lowered_for_statement_(false)
+  { }
+
+  void
+  set_is_lowered_for_statement()
+  { this->is_lowered_for_statement_ = true; }
+
+  bool
+  is_lowered_for_statement()
+  { return this->is_lowered_for_statement_; }
+
+ protected:
+  int
+  do_traverse(Traverse* traverse)
+  { return this->block_->traverse(traverse); }
+
+  void
+  do_determine_types()
+  { this->block_->determine_types(); }
+
+  bool
+  do_may_fall_through() const
+  { return this->block_->may_fall_through(); }
+
+  Bstatement*
+  do_get_backend(Translate_context* context);
+
+  void
+  do_dump_statement(Ast_dump_context*) const;
+
+ private:
+  Block* block_;
+  // True if this block statement represents a lowered for statement.
+  bool is_lowered_for_statement_;
+};
+
 // A send statement.
 
 class Send_statement : public Statement
@@ -1162,6 +1231,74 @@ class Defer_statement : public Thunk_statement
   do_dump_statement(Ast_dump_context*) const;
 };
 
+// A goto statement.
+
+class Goto_statement : public Statement
+{
+ public:
+  Goto_statement(Label* label, Location location)
+    : Statement(STATEMENT_GOTO, location),
+      label_(label)
+  { }
+
+  // Return the label being jumped to.
+  Label*
+  label() const
+  { return this->label_; }
+
+ protected:
+  int
+  do_traverse(Traverse*);
+
+  void
+  do_check_types(Gogo*);
+
+  bool
+  do_may_fall_through() const
+  { return false; }
+
+  Bstatement*
+  do_get_backend(Translate_context*);
+
+  void
+  do_dump_statement(Ast_dump_context*) const;
+
+ private:
+  Label* label_;
+};
+
+// A goto statement to an unnamed label.
+
+class Goto_unnamed_statement : public Statement
+{
+ public:
+  Goto_unnamed_statement(Unnamed_label* label, Location location)
+    : Statement(STATEMENT_GOTO_UNNAMED, location),
+      label_(label)
+  { }
+
+  Unnamed_label*
+  unnamed_label() const
+  { return this->label_; }
+
+ protected:
+  int
+  do_traverse(Traverse*);
+
+  bool
+  do_may_fall_through() const
+  { return false; }
+
+  Bstatement*
+  do_get_backend(Translate_context* context);
+
+  void
+  do_dump_statement(Ast_dump_context*) const;
+
+ private:
+  Unnamed_label* label_;
+};
+
 // A label statement.
 
 class Label_statement : public Statement
@@ -1173,7 +1310,7 @@ class Label_statement : public Statement
   { }
 
   // Return the label itself.
-  const Label*
+  Label*
   label() const
   { return this->label_; }
 
@@ -1192,6 +1329,28 @@ class Label_statement : public Statement
   Label* label_;
 };
 
+// An unnamed label statement.
+
+class Unnamed_label_statement : public Statement
+{
+ public:
+  Unnamed_label_statement(Unnamed_label* label);
+
+ protected:
+  int
+  do_traverse(Traverse*);
+
+  Bstatement*
+  do_get_backend(Translate_context* context);
+
+  void
+  do_dump_statement(Ast_dump_context*) const;
+
+ private:
+  // The label.
+  Unnamed_label* label_;
+};
+
 // An if statement.
 
 class If_statement : public Statement

gcc/go/gofrontend/types.cc

@@ -4502,10 +4502,7 @@ class Call_multiple_result_type : public Type
  protected:
   bool
   do_has_pointer() const
-  {
-    go_assert(saw_errors());
-    return false;
-  }
+  { return false; }
 
   bool
   do_compare_is_identity(Gogo*)