Change the memcmp and bcmp return type to c_int

Fix the return type of `memcmp` and `bcmp` builtin functions on targets
with a `c_int` other than `i32`.

Linked issue: rust-lang/rust#144076

Author: supersurviveur

compiler-builtins/src/mem/impls.rs

@@ -15,6 +15,7 @@
 // this use. Of course this is not a guarantee that such use will work, it just means that this
 // crate doing wrapping pointer arithmetic with a method that must not wrap won't be the problem if
 // something does go wrong at runtime.
+use core::ffi::c_int;
 use core::intrinsics::likely;
 
 const WORD_SIZE: usize = core::mem::size_of::<usize>();
@@ -384,13 +385,13 @@ 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) -> i32 {
+pub unsafe fn compare_bytes(s1: *const u8, s2: *const u8, n: usize) -> c_int {
     let mut i = 0;
     while i < n {
         let a = *s1.wrapping_add(i);
         let b = *s2.wrapping_add(i);
         if a != b {
-            return a as i32 - b as i32;
+            return c_int::from(a) - c_int::from(b);
         }
         i += 1;
     }

compiler-builtins/src/mem/mod.rs

@@ -37,12 +37,12 @@ intrinsics! {
     }
 
     #[mem_builtin]
-    pub unsafe extern "C" fn memcmp(s1: *const u8, s2: *const u8, n: usize) -> i32 {
+    pub unsafe extern "C" fn memcmp(s1: *const u8, s2: *const u8, n: usize) -> core::ffi::c_int {
         impls::compare_bytes(s1, s2, n)
     }
 
     #[mem_builtin]
-    pub unsafe extern "C" fn bcmp(s1: *const u8, s2: *const u8, n: usize) -> i32 {
+    pub unsafe extern "C" fn bcmp(s1: *const u8, s2: *const u8, n: usize) -> core::ffi::c_int {
         memcmp(s1, s2, n)
     }