compiler: remove escapes_ field from Variable and Result_variable

The fields were set to true initially and never set to false.
    These were left over from an earlier attempt at escape analysis.
    
    Reviewed-on: https://go-review.googlesource.com/c/155750

From-SVN: r267455

gcc/go/gofrontend/MERGE

@@ -1,4 +1,4 @@
-416baf55e4890acab244470f6457372987a17a68
+d9a30434440469c640a120fe7132057f5644d38c
 
 The first line of this file holds the git revision number of the last
 merge done from the gofrontend repository.

gcc/go/gofrontend/expressions.cc

@@ -3936,24 +3936,12 @@ Unary_expression::check_operand_address_taken(Gogo*)
   // If this->escapes_ is false at this point, then it was set to
   // false by an explicit call to set_does_not_escape, and the value
   // does not escape.  If this->escapes_ is true, we may be able to
-  // set it to false if taking the address of a variable that does not
+  // set it to false based on the escape analysis pass.
-  // escape.
+  if (this->escapes_)
-  Node* n = Node::make_node(this);
-  if ((n->encoding() & ESCAPE_MASK) == int(Node::ESCAPE_NONE))
-    this->escapes_ = false;
-
-  Named_object* var = NULL;
-  if (this->expr_->var_expression() != NULL)
-    var = this->expr_->var_expression()->named_object();
-  else if (this->expr_->enclosed_var_expression() != NULL)
-    var = this->expr_->enclosed_var_expression()->variable();
-
-  if (this->escapes_ && var != NULL)
     {
-      if (var->is_variable())
+      Node* n = Node::make_node(this);
-	this->escapes_ = var->var_value()->escapes();
+      if ((n->encoding() & ESCAPE_MASK) == int(Node::ESCAPE_NONE))
-      if (var->is_result_variable())
+	this->escapes_ = false;
-	this->escapes_ = var->result_var_value()->escapes();
     }
 
   this->expr_->address_taken(this->escapes_);

gcc/go/gofrontend/gogo.cc

@@ -6939,8 +6939,7 @@ Variable::Variable(Type* type, Expression* init, bool is_global,
     type_from_init_tuple_(false), type_from_range_index_(false),
     type_from_range_value_(false), type_from_chan_element_(false),
     is_type_switch_var_(false), determined_type_(false),
-    in_unique_section_(false), escapes_(true),
+    in_unique_section_(false), toplevel_decl_(NULL)
-    toplevel_decl_(NULL)
 {
   go_assert(type != NULL || init != NULL);
   go_assert(!is_parameter || init == NULL);

gcc/go/gofrontend/gogo.h

@@ -1863,11 +1863,7 @@ class Variable
   // Whether this variable should live in the heap.
   bool
   is_in_heap() const
-  {
+  { return this->is_address_taken_ && !this->is_global_; }
-    return this->is_address_taken_
-      && this->escapes_
-      && !this->is_global_;
-  }
 
   // Note that something takes the address of this variable.
   void
@@ -1885,16 +1881,6 @@ class Variable
   set_non_escaping_address_taken()
   { this->is_non_escaping_address_taken_ = true; }
 
-  // Return whether this variable escapes the function it is declared in.
-  bool
-  escapes()
-  { return this->escapes_; }
-
-  // Note that this variable does not escape the function it is declared in.
-  void
-  set_does_not_escape()
-  { this->escapes_ = false; }
-
   // Get the source location of the variable's declaration.
   Location
   location() const
@@ -2117,9 +2103,6 @@ class Variable
   // True if this variable should be put in a unique section.  This is
   // used for field tracking.
   bool in_unique_section_ : 1;
-  // Whether this variable escapes the function it is created in.  This is
-  // true until shown otherwise.
-  bool escapes_ : 1;
   // The top-level declaration for this variable. Only used for local
   // variables. Must be a Temporary_statement if not NULL.
   Statement* toplevel_decl_;
@@ -2135,7 +2118,7 @@ class Result_variable
 		  Location location)
     : type_(type), function_(function), index_(index), location_(location),
       backend_(NULL), is_address_taken_(false),
-      is_non_escaping_address_taken_(false), escapes_(true)
+      is_non_escaping_address_taken_(false)
   { }
 
   // Get the type of the result variable.
@@ -2179,23 +2162,10 @@ class Result_variable
   set_non_escaping_address_taken()
   { this->is_non_escaping_address_taken_ = true; }
 
-  // Return whether this variable escapes the function it is declared in.
-  bool
-  escapes()
-  { return this->escapes_; }
-
-  // Note that this variable does not escape the function it is declared in.
-  void
-  set_does_not_escape()
-  { this->escapes_ = false; }
-
   // Whether this variable should live in the heap.
   bool
   is_in_heap() const
-  {
+  { return this->is_address_taken_; }
-    return this->is_address_taken_
-      && this->escapes_;
-  }
 
   // Set the function.  This is used when cloning functions which call
   // recover.
@@ -2223,9 +2193,6 @@ class Result_variable
   // Whether something takes the address of this variable such that
   // the address does not escape the function.
   bool is_non_escaping_address_taken_;
-  // Whether this variable escapes the function it is created in.  This is
-  // true until shown otherwise.
-  bool escapes_;
 };
 
 // The value we keep for a named constant.  This lets us hold a type