[gcc r13-1711] go: fix f(g()) where g returns zero-sized type

[gcc r13-1711] go: fix f(g()) where g returns zero-sized type

[Ian Lance Taylor]

https://gcc.gnu.org/g:5054bc001d9b66fe68d938790f08f48621c6b976

commit r13-1711-g5054bc001d9b66fe68d938790f08f48621c6b976
Author: Ian Lance Taylor <iant@golang.org>
Date:   Fri Jul 15 08:02:13 2022 -0700

    go: fix f(g()) where g returns zero-sized type
    
    Test case is https://go.dev/cl/417481.
    
    Fixes golang/go#23868
    
            * go-gcc.cc (Gcc_backend::call_expression): Handle a void
            argument, as for f(g()) where g returns a zero-sized type.

Diff:
---
 gcc/go/go-gcc.cc | 13 +++++++++++++
 1 file changed, 13 insertions(+)

diff --git a/gcc/go/go-gcc.cc b/gcc/go/go-gcc.cc
index f3de7a8c183..7b4b2adb058 100644
--- a/gcc/go/go-gcc.cc
+++ b/gcc/go/go-gcc.cc
@@ -2112,6 +2112,19 @@ Gcc_backend::call_expression(Bfunction*, // containing fcn for call
       args[i] = fn_args.at(i)->get_tree();
       if (args[i] == error_mark_node)
         return this->error_expression();
+      if (TREE_TYPE(args[i]) == void_type_node)
+	{
+	  // This can happen for a case like f(g()) where g returns a
+	  // zero-sized type, because in that case we've changed g to
+	  // return void.
+	  tree t = TYPE_ARG_TYPES(TREE_TYPE(TREE_TYPE(fn)));
+	  for (size_t j = 0; j < i; ++j)
+	    t = TREE_CHAIN(t);
+	  tree arg_type = TREE_TYPE(TREE_VALUE(t));
+	  args[i] = fold_build2_loc(EXPR_LOCATION(args[i]), COMPOUND_EXPR,
+				    arg_type, args[i],
+				    build_zero_cst(arg_type));
+	}
     }
 
   tree fndecl = fn;