[PATCH] tree-inline: Fix TREE_READONLY of parameter replacements

[Martin Jambor]

Hi,

tree-inline leaves behind VAR_DECLs which are TREE_READONLY (because
they are copies of const parameters) but are written to because they
need to be initialized.  This patch resets the flag if any
initialization is performed, regardless of if the type needs
construction or not.

There are other sources of variables which are incorrectly marked as
TREE_READOLY, but with this patch and a verifier catching them I can
at least compile the Ada run-time library.

Bootstrapped and tested on x86_64-linux and aarch64-linux, LTO bootstrap
on x86_64-linux is ongoing.  OK for trunk if it passes?

Thanks,

Martin


gcc/ChangeLog:

2021-06-22  Martin Jambor  <mjambor@suse.cz>

	* tree-inline.c (setup_one_parameter): Set TREE_READONLY of the
	param replacement to zero if it is initialized, regardless if it
	needs constructing.
---
 gcc/tree-inline.c | 13 +------------
 1 file changed, 1 insertion(+), 12 deletions(-)

diff --git a/gcc/tree-inline.c b/gcc/tree-inline.c
index 4a0dc3b6b60..ac8abcd400b 100644
--- a/gcc/tree-inline.c
+++ b/gcc/tree-inline.c
@@ -3491,18 +3491,6 @@ setup_one_parameter (copy_body_data *id, tree p, tree value, tree fn,
      automatically replaced by the VAR_DECL.  */
   insert_decl_map (id, p, var);
 
-  /* Even if P was TREE_READONLY, the new VAR should not be.
-     In the original code, we would have constructed a
-     temporary, and then the function body would have never
-     changed the value of P.  However, now, we will be
-     constructing VAR directly.  The constructor body may
-     change its value multiple times as it is being
-     constructed.  Therefore, it must not be TREE_READONLY;
-     the back-end assumes that TREE_READONLY variable is
-     assigned to only once.  */
-  if (TYPE_NEEDS_CONSTRUCTING (TREE_TYPE (p)))
-    TREE_READONLY (var) = 0;
-
   tree rhs = value;
   if (value
       && value != error_mark_node
@@ -3549,6 +3537,7 @@ setup_one_parameter (copy_body_data *id, tree p, tree value, tree fn,
 	  return insert_init_debug_bind (id, bb, var, rhs, NULL);
 	}
 
+      TREE_READONLY (var) = 0;
       STRIP_USELESS_TYPE_CONVERSION (rhs);
 
       /* If we are in SSA form properly remap the default definition
-- 
2.31.1