1 files changed, 29 insertions, 23 deletions

diff --git a/gcc/cp/cp-gimplify.cc b/gcc/cp/cp-gimplify.cc
index bdf6e5f..a282c39 100644
--- a/gcc/cp/cp-gimplify.cc
+++ b/gcc/cp/cp-gimplify.cc
@@ -1052,27 +1052,6 @@ cp_fold_immediate_r (tree *stmt_p, int *walk_subtrees, void *data_)
 
   switch (TREE_CODE (stmt))
     {
-    /* Unfortunately we must handle code like
-	 false ? bar () : 42
-       where we have to check bar too.  The cp_fold call in cp_fold_r could
-       fold the ?: into a constant before we see it here.  */
-    case COND_EXPR:
-      /* If we are called from cp_fold_immediate, we don't need to worry about
-	 cp_fold folding away the COND_EXPR.  */
-      if (data->flags & ff_fold_immediate)
-	break;
-      if (TREE_OPERAND (stmt, 1)
-	  && cp_walk_tree (&TREE_OPERAND (stmt, 1), cp_fold_immediate_r, data,
-			   nullptr))
-	return error_mark_node;
-      if (TREE_OPERAND (stmt, 2)
-	  && cp_walk_tree (&TREE_OPERAND (stmt, 2), cp_fold_immediate_r, data,
-			   nullptr))
-	return error_mark_node;
-      /* We're done here.  Don't clear *walk_subtrees here though: we're called
-	 from cp_fold_r and we must let it recurse on the expression with
-	 cp_fold.  */
-      break;
     case PTRMEM_CST:
       if (TREE_CODE (PTRMEM_CST_MEMBER (stmt)) == FUNCTION_DECL
 	  && DECL_IMMEDIATE_FUNCTION_P (PTRMEM_CST_MEMBER (stmt)))
@@ -1162,8 +1141,35 @@ cp_fold_r (tree *stmt_p, int *walk_subtrees, void *data_)
   tree stmt = *stmt_p;
   enum tree_code code = TREE_CODE (stmt);
 
-  if (cxx_dialect > cxx17)
-    cp_fold_immediate_r (stmt_p, walk_subtrees, data);
+  if (cxx_dialect >= cxx20)
+    {
+      /* Unfortunately we must handle code like
+	   false ? bar () : 42
+	 where we have to check bar too.  The cp_fold call below could
+	 fold the ?: into a constant before we've checked it.  */
+      if (code == COND_EXPR)
+	{
+	  auto then_fn = cp_fold_r, else_fn = cp_fold_r;
+	  /* See if we can figure out if either of the branches is dead.  If it
+	     is, we don't need to do everything that cp_fold_r does.  */
+	  tree cond = maybe_constant_value (TREE_OPERAND (stmt, 0));
+	  if (integer_zerop (cond))
+	    then_fn = cp_fold_immediate_r;
+	  else if (TREE_CODE (cond) == INTEGER_CST)
+	    else_fn = cp_fold_immediate_r;
+
+	  cp_walk_tree (&TREE_OPERAND (stmt, 0), cp_fold_r, data, nullptr);
+	  if (TREE_OPERAND (stmt, 1))
+	    cp_walk_tree (&TREE_OPERAND (stmt, 1), then_fn, data,
+			  nullptr);
+	  if (TREE_OPERAND (stmt, 2))
+	    cp_walk_tree (&TREE_OPERAND (stmt, 2), else_fn, data,
+			  nullptr);
+	  *walk_subtrees = 0;
+	  /* Don't return yet, still need the cp_fold below.  */
+	}
+      cp_fold_immediate_r (stmt_p, walk_subtrees, data);
+    }
 
   *stmt_p = stmt = cp_fold (*stmt_p, data->flags);