compiler: move some escape check to Mark_address_taken

    
    Move some check of escape state earlier, from get_backend to
    Mark_address_taken. So we can reclaim escape analysis Nodes
    before kicking off the backend (not done in this CL). Also it
    makes it easier to check variables and closures do not escape
    when the escape analysis is run for the runtime package (also
    not done in this CL).
    
    Reviewed-on: https://go-review.googlesource.com/85735

From-SVN: r256406

gcc/go/gofrontend/MERGE

-cf5a64066fa21b20beae0b895c05d26af53e13e0
+584fdecefce831c3471dbd4857ba0ce0be2b5212
 
 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

@@ -12383,9 +12383,7 @@ Allocation_expression::do_get_backend(Translate_context* context)
   Gogo* gogo = context->gogo();
   Location loc = this->location();
 
-  Node* n = Node::make_node(this);
-  if (this->allocate_on_stack_
-      || (n->encoding() & ESCAPE_MASK) == int(Node::ESCAPE_NONE))
+  if (this->allocate_on_stack_)
     {
       int64_t size;
       bool ok = this->type_->backend_type_size(gogo, &size);
@@ -13161,13 +13159,8 @@ Slice_construction_expression::do_get_backend(Translate_context* context)
     }
   else
     {
+      go_assert(this->storage_escapes_ || this->element_count() == 0);
       space = Expression::make_heap_expression(this->array_val_, loc);
-      Node* n = Node::make_node(this);
-      if ((n->encoding() & ESCAPE_MASK) == int(Node::ESCAPE_NONE))
-	{
-	  n = Node::make_node(space);
-	  n->set_encoding(Node::ESCAPE_NONE);
-	}
     }
 
   // Build a constructor for the slice.
@@ -14261,8 +14254,7 @@ Heap_expression::do_get_backend(Translate_context* context)
   Btype* btype = this->type()->get_backend(gogo);
 
   Expression* alloc = Expression::make_allocation(etype, loc);
-  Node* n = Node::make_node(this);
-  if ((n->encoding() & ESCAPE_MASK) == int(Node::ESCAPE_NONE))
+  if (this->allocate_on_stack_)
     alloc->allocation_expression()->set_allocate_on_stack();
   Bexpression* space = alloc->get_backend(context);
 

gcc/go/gofrontend/expressions.h

@@ -3870,13 +3870,17 @@ class Heap_expression : public Expression
  public:
   Heap_expression(Expression* expr, Location location)
     : Expression(EXPRESSION_HEAP, location),
-      expr_(expr)
+      expr_(expr), allocate_on_stack_(false)
   { }
 
   Expression*
   expr() const
   { return this->expr_; }
 
+  void
+  set_allocate_on_stack()
+  { this->allocate_on_stack_ = true; }
+
  protected:
   int
   do_traverse(Traverse* traverse)
@@ -3910,6 +3914,8 @@ class Heap_expression : public Expression
  private:
   // The expression which is being put on the heap.
   Expression* expr_;
+  // Whether or not this is a stack allocation.
+  bool allocate_on_stack_;
 };
 
 // A receive expression.

gcc/go/gofrontend/wb.cc

@@ -65,6 +65,25 @@ Mark_address_taken::expression(Expression** pexpr)
       aie->array()->address_taken(escapes);
     }
 
+  if (expr->allocation_expression() != NULL)
+    {
+      Node* n = Node::make_node(expr);
+      if ((n->encoding() & ESCAPE_MASK) == Node::ESCAPE_NONE)
+        expr->allocation_expression()->set_allocate_on_stack();
+    }
+  if (expr->heap_expression() != NULL)
+    {
+      Node* n = Node::make_node(expr);
+      if ((n->encoding() & ESCAPE_MASK) == Node::ESCAPE_NONE)
+        expr->heap_expression()->set_allocate_on_stack();
+    }
+  if (expr->slice_literal() != NULL)
+    {
+      Node* n = Node::make_node(expr);
+      if ((n->encoding() & ESCAPE_MASK) == Node::ESCAPE_NONE)
+        expr->slice_literal()->set_storage_does_not_escape();
+    }
+
   // Rewrite non-escaping makeslice with constant size to stack allocation.
   Unsafe_type_conversion_expression* uce =
     expr->unsafe_conversion_expression();