This patch to the Go frontend changes it to not produce a closure for an embedded function if one is not needed. Earlier, when Go permitted comparisons of function types, it was necessary to always create a closure for an embedded function, so that each embedded function would be reliably distinct. Go 1 removed function comparisons, for this and other reasons. Now, if an embedded function does not require a closure, because it does not refer to any variables defined in enclosing functions, we don't need to create a closure. Bootstrapped and ran Go testsuite on x86_64-unknown-linux-gnu. Committed to mainline and 4.7 branch.
Ian
diff -r b7d2ae6bea1b go/expressions.cc --- a/go/expressions.cc Fri May 25 11:21:08 2012 -0700 +++ b/go/expressions.cc Fri May 25 14:11:54 2012 -0700 @@ -1312,30 +1312,18 @@ && TREE_CODE(TREE_OPERAND(fnaddr, 0)) == FUNCTION_DECL); TREE_ADDRESSABLE(TREE_OPERAND(fnaddr, 0)) = 1; - // For a normal non-nested function call, that is all we have to do. - if (!this->function_->is_function() - || this->function_->func_value()->enclosing() == NULL) - { - go_assert(this->closure_ == NULL); - return fnaddr; - } - - // For a nested function call, we have to always allocate a - // trampoline. If we don't always allocate, then closures will not - // be reliably distinct. - Expression* closure = this->closure_; - tree closure_tree; - if (closure == NULL) - closure_tree = null_pointer_node; - else - { - // Get the value of the closure. This will be a pointer to - // space allocated on the heap. - closure_tree = closure->get_tree(context); - if (closure_tree == error_mark_node) - return error_mark_node; - go_assert(POINTER_TYPE_P(TREE_TYPE(closure_tree))); - } + // If there is no closure, that is all have to do. + if (this->closure_ == NULL) + return fnaddr; + + go_assert(this->function_->func_value()->enclosing() != NULL); + + // Get the value of the closure. This will be a pointer to space + // allocated on the heap. + tree closure_tree = this->closure_->get_tree(context); + if (closure_tree == error_mark_node) + return error_mark_node; + go_assert(POINTER_TYPE_P(TREE_TYPE(closure_tree))); // Now we need to build some code on the heap. This code will load // the static chain pointer with the closure and then jump to the