diff --git a/library/compiler-builtins/src/mem/impls.rs b/library/compiler-builtins/src/mem/impls.rs
index f31366d765c1..72003a5c472b 100644
--- a/library/compiler-builtins/src/mem/impls.rs
+++ b/library/compiler-builtins/src/mem/impls.rs
@@ -267,7 +267,7 @@ pub unsafe fn set_bytes(mut s: *mut u8, c: u8, mut n: usize) {
 }
 
 #[inline(always)]
-pub unsafe fn compare_bytes(s1: *const u8, s2: *const u8, n: usize) {
+pub unsafe fn compare_bytes(s1: *const u8, s2: *const u8, n: usize) -> i32 {
     let mut i = 0;
     while i < n {
         let a = *s1.add(i);
diff --git a/library/compiler-builtins/src/mem/x86_64.rs b/library/compiler-builtins/src/mem/x86_64.rs
index 0bfacf713c57..fc89aa768d33 100644
--- a/library/compiler-builtins/src/mem/x86_64.rs
+++ b/library/compiler-builtins/src/mem/x86_64.rs
@@ -102,11 +102,7 @@ pub unsafe fn set_bytes(dest: *mut u8, c: u8, count: usize) {
 }
 
 #[inline(always)]
-pub unsafe fn compare_bytes(
-    a: *const u8,
-    b: *const u8,
-    n: usize,
-) -> i32 {
+pub unsafe fn compare_bytes(a: *const u8, b: *const u8, n: usize) -> i32 {
     unsafe fn cmp<T, U, F>(mut a: *const T, mut b: *const T, n: usize, f: F) -> i32
     where
         T: Clone + Copy + Eq,
diff --git a/library/compiler-builtins/testcrate/tests/mem.rs b/library/compiler-builtins/testcrate/tests/mem.rs
index 8385dfc2cec9..48ac95adc17f 100644
--- a/library/compiler-builtins/testcrate/tests/mem.rs
+++ b/library/compiler-builtins/testcrate/tests/mem.rs
@@ -116,55 +116,26 @@ fn memset_nonzero() {
 
 #[test]
 fn memcmp_eq() {
-    let arr1: [u8; 32] = [
-        0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24,
-        25, 26, 27, 28, 29, 30, 31,
-    ];
-    let arr2: [u8; 32] = [
-        0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24,
-        25, 26, 27, 28, 29, 30, 31,
-    ];
-    for i in 0..32 {
+    let arr1 @ arr2 = gen_arr::<256>();
+    for i in 0..256 {
         unsafe {
-            assert_eq!(memcmp(arr1.as_ptr(), arr2.as_ptr(), i), 0);
-            assert_eq!(memcmp(arr2.as_ptr(), arr1.as_ptr(), i), 0);
+            assert_eq!(memcmp(arr1.0.as_ptr(), arr2.0.as_ptr(), i), 0);
+            assert_eq!(memcmp(arr2.0.as_ptr(), arr1.0.as_ptr(), i), 0);
         }
     }
 }
 
 #[test]
 fn memcmp_ne() {
-    let arr1: [u8; 8] = [0, 1, 2, 3, 4, 5, 6, 7];
-    let arr2: [u8; 8] = [0, 1, 2, 3, 4, 5, 7, 7];
-    unsafe {
-        assert!(memcmp(arr1.as_ptr(), arr2.as_ptr(), 8) < 0);
-        assert!(memcmp(arr2.as_ptr(), arr1.as_ptr(), 8) > 0);
-    }
-}
-
-#[test]
-fn memcmp_ne_16() {
-    let arr1: [u8; 16] = [0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15];
-    let arr2: [u8; 16] = [0, 1, 2, 3, 4, 5, 7, 7, 8, 9, 10, 11, 12, 13, 14, 15];
-    unsafe {
-        assert!(memcmp(arr1.as_ptr(), arr2.as_ptr(), 16) < 0);
-        assert!(memcmp(arr2.as_ptr(), arr1.as_ptr(), 16) > 0);
-    }
-}
-
-#[test]
-fn memcmp_ne_32() {
-    let arr1: [u8; 32] = [
-        0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
-        0, 0, 0, 0,
-    ];
-    let arr2: [u8; 32] = [
-        0, 1, 2, 3, 4, 5, 7, 7, 8, 9, 10, 11, 12, 13, 14, 15, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
-        0, 0, 0, 0,
-    ];
-    unsafe {
-        assert!(memcmp(arr1.as_ptr(), arr2.as_ptr(), 32) < 0);
-        assert!(memcmp(arr2.as_ptr(), arr1.as_ptr(), 32) > 0);
+    let arr1 @ arr2 = gen_arr::<256>();
+    for i in 0..256 {
+        let mut diff_arr = arr1;
+        diff_arr.0[i] = 127;
+        let expect = diff_arr.0[i].cmp(&arr2.0[i]);
+        for k in i + 1..256 {
+            let result = unsafe { memcmp(diff_arr.0.as_ptr(), arr2.0.as_ptr(), k) };
+            assert_eq!(expect, result.cmp(&0));
+        }
     }
 }