c++: Handle structured bindings like anon unions in initializers [PR108474]

As reported by Andrew Pinski, structured bindings (with the exception
of the ones using std::tuple_{size,element} and get which are really
standalone variables in addition to the binding one) also use
DECL_VALUE_EXPR and needs the same treatment in static initializers.

On Sun, Jan 22, 2023 at 07:19:07PM -0500, Jason Merrill wrote:
> Though, actually, why not instead fix expand_expr_real_1 (and staticp) to
> look through DECL_VALUE_EXPR?

Doing it when emitting the initializers seems to be too late to me,
we in various spots try to put parts of the static var DECL_INITIAL expressions
into the IL, or e.g. for varpool purposes remember which vars are referenced
there.

This patch moves it to record_reference, which is called from varpool_node::analyze
and so about the same time as gimplification of the bodies which also
replaces DECL_VALUE_EXPRs.

2023-01-24  Jakub Jelinek  <jakub@redhat.com>

	PR c++/108474
	* cgraphbuild.cc: Include gimplify.h.
	(record_reference): Replace VAR_DECLs with DECL_HAS_VALUE_EXPR_P with
	their corresponding DECL_VALUE_EXPR expressions after unsharing.

	* cp-gimplify.cc (cp_fold_r): Revert 2023-01-19 changes.

	* g++.dg/cpp1z/decomp57.C: New test.
	* g++.dg/cpp1z/decomp58.C: New test.

1 files changed, 0 insertions, 10 deletions

diff --git a/gcc/cp/cp-gimplify.cc b/gcc/cp/cp-gimplify.cc
index 92cd309..a35cedd 100644
--- a/gcc/cp/cp-gimplify.cc
+++ b/gcc/cp/cp-gimplify.cc
@@ -1035,16 +1035,6 @@ cp_fold_r (tree *stmt_p, int *walk_subtrees, void *data_)
 	}
       break;
 
-    case VAR_DECL:
-      /* In initializers replace anon union artificial VAR_DECLs
-	 with their DECL_VALUE_EXPRs, as nothing will do it later.  */
-      if (DECL_ANON_UNION_VAR_P (stmt) && !data->genericize)
-	{
-	  *stmt_p = stmt = unshare_expr (DECL_VALUE_EXPR (stmt));
-	  break;
-	}
-      break;
-
     default:
       break;
     }