+/* If we lack umul_ppmm but have smul_ppmm, define umul_ppmm in terms of
+ smul_ppmm. */
+#if !defined (umul_ppmm) && defined (smul_ppmm)
+#define umul_ppmm(w1, w0, u, v) \
+ do { \
+ UWtype __w1; \
+ UWtype __xm0 = (u), __xm1 = (v); \
+ smul_ppmm (__w1, w0, __xm0, __xm1); \
+ (w1) = __w1 + (-(__xm0 >> (W_TYPE_SIZE - 1)) & __xm1) \
+ + (-(__xm1 >> (W_TYPE_SIZE - 1)) & __xm0); \
+ } while (0)
+#endif
+
+/* If we still don't have umul_ppmm, define it using plain C. */