escape: Analyze multiple result type assertions.

For multi-result type assertions, the object being converted is hidden
    behind unsafe conversions and calls to runtime methods.  This change
    allows the analysis to make edges between the result of the assertion
    and the object being asserted.
    
    Reviewed-on: https://go-review.googlesource.com/10661

From-SVN: r225751

gcc/go/gofrontend/MERGE

@@ -1,4 +1,4 @@
-a5122ab435cf40c22b110487eb5f189ee28e77f4
+1b3d945d201bcb1238f15ef154c6e4671e4c6f5c
 
 The first line of this file holds the git revision number of the last
 merge done from the gofrontend repository.

gcc/go/gofrontend/escape.cc

@@ -547,6 +547,41 @@ Build_connection_graphs::resolve_var_reference(Expression* expr)
 	expr = expr->type_guard_expression()->expr();
 	break;
 
+      case Expression::EXPRESSION_UNSAFE_CONVERSION:
+	{
+	  Expression* e = expr->unsafe_conversion_expression()->expr();
+	  if (e->call_result_expression() != NULL
+	      && e->call_result_expression()->index() == 0)
+	    {
+	      // a, ok := p.(T) gets lowered into a call to one of the interface
+	      // to type conversion functions instead of a type guard expression.
+	      // We only want to make a connection between a and p, the bool
+	      // result should not escape because p escapes.
+	      e = e->call_result_expression()->call();
+
+	      Named_object* fn =
+		e->call_expression()->fn()->func_expression()->named_object();
+	      std::string fn_name = fn->name();
+	      if (fn->package() == NULL
+		  && fn->is_function_declaration()
+		  && !fn->func_declaration_value()->asm_name().empty())
+		{
+		  if (fn_name == "ifaceI2E2"
+		      || fn_name == "ifaceI2I2")
+		    e = e->call_expression()->args()->at(0);
+		  else if (fn_name == "ifaceE2I2"
+			   || fn_name == "ifaceI2I2"
+			   || fn_name == "ifaceE2T2P"
+			   || fn_name == "ifaceI2T2P"
+			   || fn_name == "ifaceE2T2"
+			   || fn_name == "ifaceI2T2")
+		    e = e->call_expression()->args()->at(1);
+		}
+	    }
+	  expr = e;
+	}
+	break;
+
       default:
 	done = true;
 	break;

gcc/go/gofrontend/expressions.cc

@@ -3391,52 +3391,7 @@ Expression::make_cast(Type* type, Expression* val, Location location)
   return new Type_conversion_expression(type, val, location);
 }
 
-// An unsafe type conversion, used to pass values to builtin functions.
-
-class Unsafe_type_conversion_expression : public Expression
-{
- public:
-  Unsafe_type_conversion_expression(Type* type, Expression* expr,
-				    Location location)
-    : Expression(EXPRESSION_UNSAFE_CONVERSION, location),
-      type_(type), expr_(expr)
-  { }
-
- protected:
-  int
-  do_traverse(Traverse* traverse);
-
-  bool
-  do_is_immutable() const;
-
-  Type*
-  do_type()
-  { return this->type_; }
-
-  void
-  do_determine_type(const Type_context*)
-  { this->expr_->determine_type_no_context(); }
-
-  Expression*
-  do_copy()
-  {
-    return new Unsafe_type_conversion_expression(this->type_,
-						 this->expr_->copy(),
-						 this->location());
-  }
-
-  Bexpression*
-  do_get_backend(Translate_context*);
-
-  void
-  do_dump_expression(Ast_dump_context*) const;
-
- private:
-  // The type to convert to.
-  Type* type_;
-  // The expression to convert.
-  Expression* expr_;
-};
+// Class Unsafe_type_conversion_expression.
 
 // Traversal.
 

gcc/go/gofrontend/expressions.h

@@ -32,6 +32,7 @@ class Temporary_reference_expression;
 class Set_and_use_temporary_expression;
 class String_expression;
 class Type_conversion_expression;
+class Unsafe_type_conversion_expression;
 class Unary_expression;
 class Binary_expression;
 class Call_expression;
@@ -571,6 +572,15 @@ class Expression
   conversion_expression()
   { return this->convert<Type_conversion_expression, EXPRESSION_CONVERSION>(); }
 
+  // If this is an unsafe conversion expression, return the
+  // Unsafe_type_conversion_expression structure.  Otherwise, return NULL.
+  Unsafe_type_conversion_expression*
+  unsafe_conversion_expression()
+  {
+    return this->convert<Unsafe_type_conversion_expression,
+			 EXPRESSION_UNSAFE_CONVERSION>();
+  }
+
   // Return whether this is the expression nil.
   bool
   is_nil_expression() const
@@ -1505,6 +1515,57 @@ class Type_conversion_expression : public Expression
   bool may_convert_function_types_;
 };
 
+// An unsafe type conversion, used to pass values to builtin functions.
+
+class Unsafe_type_conversion_expression : public Expression
+{
+ public:
+  Unsafe_type_conversion_expression(Type* type, Expression* expr,
+				    Location location)
+    : Expression(EXPRESSION_UNSAFE_CONVERSION, location),
+      type_(type), expr_(expr)
+  { }
+
+  Expression*
+  expr() const
+  { return this->expr_; }
+
+ protected:
+  int
+  do_traverse(Traverse* traverse);
+
+  bool
+  do_is_immutable() const;
+
+  Type*
+  do_type()
+  { return this->type_; }
+
+  void
+  do_determine_type(const Type_context*)
+  { this->expr_->determine_type_no_context(); }
+
+  Expression*
+  do_copy()
+  {
+    return new Unsafe_type_conversion_expression(this->type_,
+						 this->expr_->copy(),
+						 this->location());
+  }
+
+  Bexpression*
+  do_get_backend(Translate_context*);
+
+  void
+  do_dump_expression(Ast_dump_context*) const;
+
+ private:
+  // The type to convert to.
+  Type* type_;
+  // The expression to convert.
+  Expression* expr_;
+};
+
 // A Unary expression.
 
 class Unary_expression : public Expression
@@ -2024,6 +2085,10 @@ class Call_result_expression : public Expression
   call() const
   { return this->call_; }
 
+  unsigned int
+  index() const
+  { return this->index_; }
+
  protected:
   int
   do_traverse(Traverse*);