Rust: Make 'tree'-level 'MAIN_NAME_P' work

'gcc/tree.h':

    #define main_identifier_node		global_trees[TI_MAIN_IDENTIFIER]
    #define MAIN_NAME_P(NODE) \
      (IDENTIFIER_NODE_CHECK (NODE) == main_identifier_node)

..., which is not initialized by default, but has to be set up by every front
end individually.  'MAIN_NAME_P' enables certain code optimizations, but is
especially also relevant for back ends that emit additional program entry setup
code for 'main'.

	gcc/rust/
	* backend/rust-compile-base.cc (HIRCompileBase::compile_function):
	For 'main', initialize 'main_identifier_node'.

1 files changed, 6 insertions, 0 deletions

diff --git a/gcc/rust/backend/rust-compile-base.cc b/gcc/rust/backend/rust-compile-base.cc
index 9650d1a..19bf242 100644
--- a/gcc/rust/backend/rust-compile-base.cc
+++ b/gcc/rust/backend/rust-compile-base.cc
@@ -523,6 +523,12 @@ HIRCompileBase::compile_function (
 
   // we don't mangle the main fn since we haven't implemented the main shim
   bool is_main_fn = fn_name.compare ("main") == 0;
+  if (is_main_fn)
+    {
+      rust_assert (!main_identifier_node);
+      /* So that 'MAIN_NAME_P' works.  */
+      main_identifier_node = get_identifier (ir_symbol_name.c_str ());
+    }
   std::string asm_name = fn_name;
 
   unsigned int flags = 0;