1 files changed, 71 insertions, 0 deletions
diff --git a/gcc/cp/semantics.c b/gcc/cp/semantics.c
index 5ff70ff..d33ef42 100644
--- a/gcc/cp/semantics.c
+++ b/gcc/cp/semantics.c
@@ -10679,4 +10679,75 @@ cp_build_vec_convert (tree arg, location_t loc, tree type,
   return build_call_expr_internal_loc (loc, IFN_VEC_CONVERT, type, 1, arg);
 }
 
+/* Finish __builtin_bit_cast (type, arg).  */
+
+tree
+cp_build_bit_cast (location_t loc, tree type, tree arg,
+		   tsubst_flags_t complain)
+{
+  if (error_operand_p (type))
+    return error_mark_node;
+  if (!dependent_type_p (type))
+    {
+      if (!complete_type_or_maybe_complain (type, NULL_TREE, complain))
+	return error_mark_node;
+      if (TREE_CODE (type) == ARRAY_TYPE)
+	{
+	  /* std::bit_cast for destination ARRAY_TYPE is not possible,
+	     as functions may not return an array, so don't bother trying
+	     to support this (and then deal with VLAs etc.).  */
+	  error_at (loc, "%<__builtin_bit_cast%> destination type %qT "
+			 "is an array type", type);
+	  return error_mark_node;
+	}
+      if (!trivially_copyable_p (type))
+	{
+	  error_at (loc, "%<__builtin_bit_cast%> destination type %qT "
+			 "is not trivially copyable", type);
+	  return error_mark_node;
+	}
+    }
+
+  if (error_operand_p (arg))
+    return error_mark_node;
+
+  if (!type_dependent_expression_p (arg))
+    {
+      if (TREE_CODE (TREE_TYPE (arg)) == ARRAY_TYPE)
+	{
+	  /* Don't perform array-to-pointer conversion.  */
+	  arg = mark_rvalue_use (arg, loc, true);
+	  if (!complete_type_or_maybe_complain (TREE_TYPE (arg), arg, complain))
+	    return error_mark_node;
+	}
+      else
+	arg = decay_conversion (arg, complain);
+
+      if (error_operand_p (arg))
+	return error_mark_node;
+
+      if (!trivially_copyable_p (TREE_TYPE (arg)))
+	{
+	  error_at (cp_expr_loc_or_loc (arg, loc),
+		    "%<__builtin_bit_cast%> source type %qT "
+		    "is not trivially copyable", TREE_TYPE (arg));
+	  return error_mark_node;
+	}
+      if (!dependent_type_p (type)
+	  && !cp_tree_equal (TYPE_SIZE_UNIT (type),
+			     TYPE_SIZE_UNIT (TREE_TYPE (arg))))
+	{
+	  error_at (loc, "%<__builtin_bit_cast%> source size %qE "
+			 "not equal to destination type size %qE",
+			 TYPE_SIZE_UNIT (TREE_TYPE (arg)),
+			 TYPE_SIZE_UNIT (type));
+	  return error_mark_node;
+	}
+    }
+
+  tree ret = build_min (BIT_CAST_EXPR, type, arg);
+  SET_EXPR_LOCATION (ret, loc);
+  return ret;
+}
+
 #include "gt-cp-semantics.h"