[patch] Fix PR C++/90448

[Eric Botcazou]

Hi,

this is a regression present on the mainline and 10 branch for architectures
that pass all structure types by reference, e.g. 32-bit PowerPC or SPARC.

Jakub posted a detailed analysis in the audit trail and this boils down to
the RTL expander trying to take the address of a DECL whose RTX is a register.

Bootstrapped/regtested on x86-64/Linux, PowerPC64/Linux and SPARC/Solaris,
OK for the mainline and 10 branch?


2021-03-08  Eric Botcazou  <ebotca...@adacore.com>

        PR C++/90448
        * calls.c (initialize_argument_information): When the argument
        is passed by reference, do not make a copy in a thunk only if
        the argument is already in memory.  Remove redundant test for
        the case of callee copy.

-- 
Eric Botcazou
diff --git a/gcc/calls.c b/gcc/calls.c
index 1fea022ad8a..ff606204772 100644
--- a/gcc/calls.c
+++ b/gcc/calls.c
@@ -2388,19 +2388,17 @@ initialize_argument_information (int num_actuals ATTRIBUTE_UNUSED,
       function_arg_info arg (type, argpos < n_named_args);
       if (pass_by_reference (args_so_far_pnt, arg))
 	{
-	  bool callee_copies;
-	  tree base = NULL_TREE;
-
-	  callee_copies = reference_callee_copied (args_so_far_pnt, arg);
-
-	  /* If we're compiling a thunk, pass through invisible references
-	     instead of making a copy.  */
-	  if (call_from_thunk_p
-	      || (callee_copies
-		  && !TREE_ADDRESSABLE (type)
-		  && (base = get_base_address (args[i].tree_value))
-		  && TREE_CODE (base) != SSA_NAME
-		  && (!DECL_P (base) || MEM_P (DECL_RTL (base)))))
+	  const bool callee_copies
+	    = reference_callee_copied (args_so_far_pnt, arg);
+	  tree base;
+
+	  /* If we're compiling a thunk, pass directly the address of an object
+	     already in memory, instead of making a copy.  Likewise if we want
+	     to make the copy in the callee instead of the caller.  */
+	  if ((call_from_thunk_p || callee_copies)
+	      && (base = get_base_address (args[i].tree_value))
+	      && TREE_CODE (base) != SSA_NAME
+	      && (!DECL_P (base) || MEM_P (DECL_RTL (base))))
 	    {
 	      /* We may have turned the parameter value into an SSA name.
 		 Go back to the original parameter so we can take the