diff --git a/library/stdarch/crates/core_arch/src/x86/avx512f.rs b/library/stdarch/crates/core_arch/src/x86/avx512f.rs
index 5b64367d1f29..804ffc30d3a3 100644
--- a/library/stdarch/crates/core_arch/src/x86/avx512f.rs
+++ b/library/stdarch/crates/core_arch/src/x86/avx512f.rs
@@ -207,12 +207,4 @@ mod tests {
         );
         assert_eq_m512i(r, e);
     }
-
-    #[simd_test(enable = "avx512f")]
-    unsafe fn test_mm512_cmplt_epu64_mask() {
-        let a = _mm512_set_epi64(0, 1, -1, u64::MAX as i64, i64::MAX, i64::MIN, 100, -100);
-        let b = _mm512_set1_epi64(-1);
-        let m = _mm512_cmplt_epu64_mask(a, b);
-        assert_eq!(m, 0b11001111);
-    }
 }
diff --git a/library/stdarch/crates/core_arch/src/x86_64/avx512f.rs b/library/stdarch/crates/core_arch/src/x86_64/avx512f.rs
index 8c40235958e5..c4544a5acf6b 100644
--- a/library/stdarch/crates/core_arch/src/x86_64/avx512f.rs
+++ b/library/stdarch/crates/core_arch/src/x86_64/avx512f.rs
@@ -18,18 +18,27 @@ pub unsafe fn _mm512_set_epi64(
     e1: i64,
     e0: i64,
 ) -> __m512i {
-    let r = i64x8(e0, e1, e2, e3, e4, e5, e6, e7);
-    transmute(r)
+  _mm512_setr_epi64(e7, e6, e5, e4, e3, e2, e1, e0);
 }
 
-/// Compare packed unsigned 64-bit integers in a and b for less-than, and store the results in a mask vector.
+/// Sets packed 64-bit integers in `dst` with the supplied values in
+/// reverse order.
 ///
-/// [Intel's documentation](https://software.intel.com/sites/landingpage/IntrinsicsGuide/#expand=727,1063,4909,1062,1062&text=_mm512_cmplt_epu64)
+/// [Intel's documentation]( https://software.intel.com/sites/landingpage/IntrinsicsGuide/#expand=727,1063,4909,1062,1062,4909&text=_mm512_set_epi64)
 #[inline]
 #[target_feature(enable = "avx512f")]
-#[cfg_attr(test, assert_instr(vpcmpuq))]
-pub unsafe fn _mm512_cmplt_epu64_mask(a: __m512i, b: __m512i) -> __mmask8 {
-    simd_bitmask::<__m512i, _>(simd_lt(a.as_u64x8(), b.as_u64x8()))
+pub unsafe fn _mm512_setr_epi64(
+    e7: i64,
+    e6: i64,
+    e5: i64,
+    e4: i64,
+    e3: i64,
+    e2: i64,
+    e1: i64,
+    e0: i64,
+) -> __m512i {
+    let r = i64x8(e0, e1, e2, e3, e4, e5, e6, e7);
+    transmute(r)
 }
 
 #[cfg(test)]
@@ -47,4 +56,16 @@ mod tests {
         let m = _mm512_cmplt_epu64_mask(a, b);
         assert_eq!(m, 0b11001111);
     }
+
+    #[simd_test(enable = "avx512f")]
+    unsafe fn test_mm512_set_epi64() {
+        let r = _mm512_setr_epi64(0, 1, 2, 3, 4, 5, 6, 7);
+	assert_eq_m512i(r, _mm512_set_epi64(7, 6, 5, 4, 3, 2, 1, 0))
+    }
+
+    #[simd_test(enable = "avx512f")]
+    unsafe fn test_mm512_setr_epi64() {
+        let r = _mm512_set_epi64(0, 1, 2, 3, 4, 5, 6, 7);
+	assert_eq_m512i(r, _mm512_setr_epi64(7, 6, 5, 4, 3, 2, 1, 0))
+    }
 }