+(defknown sc-number-or-lose (symbol) sc-number
+ (foldable))
+
+;;;; memory barriers
+
+(defknown sb!vm:%compiler-barrier () (values) ())
+(defknown sb!vm:%memory-barrier () (values) ())
+(defknown sb!vm:%read-barrier () (values) ())
+(defknown sb!vm:%write-barrier () (values) ())
+(defknown sb!vm:%data-dependency-barrier () (values) ())
+
+