diff --git a/compiler-rt/lib/builtins/udivmodti4.c b/compiler-rt/lib/builtins/udivmodti4.c
--- a/compiler-rt/lib/builtins/udivmodti4.c
+++ b/compiler-rt/lib/builtins/udivmodti4.c
@@ -24,6 +24,8 @@
                                             du_int *r) {
   const unsigned n_udword_bits = sizeof(du_int) * CHAR_BIT;
   const du_int b = (1ULL << (n_udword_bits / 2)); // Number base (32 bits)
+  const du_int mask =
+      (~0ULL >> (n_udword_bits / 2));             // Lower bits mask (32 bits)
   du_int un1, un0;                                // Norm. dividend LSD's
   du_int vn1, vn0;                                // Norm. divisor digits
   du_int q1, q0;                                  // Quotient digits
@@ -45,11 +47,11 @@
 
   // Break divisor up into two 32-bit digits.
   vn1 = v >> (n_udword_bits / 2);
-  vn0 = v & 0xFFFFFFFF;
+  vn0 = v & mask;
 
   // Break right half of dividend into two digits.
   un1 = un10 >> (n_udword_bits / 2);
-  un0 = un10 & 0xFFFFFFFF;
+  un0 = un10 & mask;
 
   // Compute the first quotient digit, q1.
   q1 = un64 / vn1;