Index: lib/builtins/fixunsxfti.c
===================================================================
--- lib/builtins/fixunsxfti.c
+++ lib/builtins/fixunsxfti.c
@@ -20,30 +20,49 @@
  *          Negative values all become zero.
  */
 
-/* Assumption: long double is an intel 80 bit floating point type padded with 6 bytes
- *             tu_int is a 128 bit integral type
- *             value in long double is representable in tu_int or is negative 
+/* Assumption:
+ *  if __LDBL_MANT_DIG__ == 64, it's Intel 80-bit FP representation:
+ *     long double is an intel 80 bit floating point type padded with 6 bytes:
+ *     gggg gggg gggg gggg gggg gggg gggg gggg | gggg gggg gggg gggg seee eeee eeee eeee |
+ *     1mmm mmmm mmmm mmmm mmmm mmmm mmmm mmmm | mmmm mmmm mmmm mmmm mmmm mmmm mmmm mmmm
+ *  if __LDBL_MANT_DIG__ == 113, it's IEEE754 quad-precision floating point type:
+ *      sign: bit 127, exp: bit 126 - 112, mantissa: bit 111 - 0.
+ *  tu_int is a 128 bit integral type
+ *  value in long double is representable in tu_int or is negative
  */
 
-/* gggg gggg gggg gggg gggg gggg gggg gggg | gggg gggg gggg gggg seee eeee eeee eeee |
- * 1mmm mmmm mmmm mmmm mmmm mmmm mmmm mmmm | mmmm mmmm mmmm mmmm mmmm mmmm mmmm mmmm
- */
 
 COMPILER_RT_ABI tu_int
 __fixunsxfti(long double a)
 {
     long_double_bits fb;
     fb.f = a;
+#if __LDBL_MANT_DIG__ == 113
+    // IEEE754 quad-precision floating point type.
+    // sign: fb.u.high.s.high[31]
+    // exp: fb.u.high.s.high[16:30]
+    // mantissa: fb.u.high.s.high[0:15] | fb.u.high.s.low |  fb.u.low.all
+    int isNeg = (fb.u.high.s.high >> 31);
+    int e = (fb.u.high.s.high >> 16) - 16383;
+    // clear the sign and exponent fields and set implicit one.
+    tu_int r = (tu_int)((fb.u.high.s.high & 0xFFFF) | (1 << 16)) << 96;
+    r |= (tu_int)fb.u.high.s.low << 64;
+    r |= fb.u.low.all;
+#elif __LDBL_MANT_DIG__ == 64
+    int isNeg = fb.u.high.s.low & 0x00008000;
     int e = (fb.u.high.s.low & 0x00007FFF) - 16383;
-    if (e < 0 || (fb.u.high.s.low & 0x00008000))
+    tu_int r = fb.u.low.all;
+#else
+#   error("Unsupported __LDBL_MANT_DIG__:" ## __LDBL_MANT_DIG__)
+#endif
+    if (e < 0 || isNeg)
         return 0;
     if ((unsigned)e > sizeof(tu_int) * CHAR_BIT)
         return ~(tu_int)0;
-    tu_int r = fb.u.low.all;
-    if (e > 63)
-        r <<= (e - 63);
+    if (e >= __LDBL_MANT_DIG__)
+        r <<= (e - __LDBL_MANT_DIG__ + 1);
     else
-        r >>= (63 - e);
+        r >>= (__LDBL_MANT_DIG__ - 1 - e);
     return r;
 }
 
Index: test/builtins/Unit/fixunsxfti_test.c
===================================================================
--- test/builtins/Unit/fixunsxfti_test.c
+++ test/builtins/Unit/fixunsxfti_test.c
@@ -1,5 +1,4 @@
 // RUN: %clang_builtins %s %librt -o %t && %run %t
-// XFAIL: aarch64
 // test fails for aarch64 (see pr32260)
 
 //===-- fixunsxfti_test.c - Test __fixunsxfti -----------------------------===//
@@ -23,13 +22,15 @@
 // Returns: convert a to a unsigned long long, rounding toward zero.
 //          Negative values all become zero.
 
-// Assumption: long double is an intel 80 bit floating point type padded with 6 bytes
-//             tu_int is a 64 bit integral type
-//             value in long double is representable in tu_int or is negative 
-//                 (no range checking performed)
-
-// gggg gggg gggg gggg gggg gggg gggg gggg | gggg gggg gggg gggg seee eeee eeee eeee |
-// 1mmm mmmm mmmm mmmm mmmm mmmm mmmm mmmm | mmmm mmmm mmmm mmmm mmmm mmmm mmmm mmmm
+// Assumption:
+//   if __LDBL_MANT_DIG__ == 64, it's Intel 80-bit FP representation:
+//     long double is an intel 80 bit floating point type padded with 6 bytes:
+//     gggg gggg gggg gggg gggg gggg gggg gggg | gggg gggg gggg gggg seee eeee eeee eeee |
+//     1mmm mmmm mmmm mmmm mmmm mmmm mmmm mmmm | mmmm mmmm mmmm mmmm mmmm mmmm mmmm mmmm
+//   if __LDBL_MANT_DIG__ == 113, it's IEEE754 quad-precision floating point type:
+//      sign: bit 127, exp: bit 126 - 112, mantissa: bit 111 - 0.
+//  tu_int is a 128 bit integral type
+//  value in long double is representable in tu_int or is negative
 
 COMPILER_RT_ABI tu_int __fixunsxfti(long double a);
 
@@ -59,7 +60,6 @@
 #ifdef CRT_HAS_128BIT
     if (test__fixunsxfti(0.0, 0))
         return 1;
-
     if (test__fixunsxfti(0.5, 0))
         return 1;
     if (test__fixunsxfti(0.99, 0))