memcpy: Create separate fallback.rs file

Signed-off-by: Joe Richey <[email protected]>

Author: josephlr

src/mem/fallback.rs

@@ -0,0 +1,60 @@
+use super::c_int;
+
+#[cfg_attr(all(feature = "mem", not(feature = "mangled-names")), no_mangle)]
+pub unsafe extern "C" fn memcpy(dest: *mut u8, src: *const u8, n: usize) -> *mut u8 {
+    let mut i = 0;
+    while i < n {
+        *dest.offset(i as isize) = *src.offset(i as isize);
+        i += 1;
+    }
+    dest
+}
+
+#[cfg_attr(all(feature = "mem", not(feature = "mangled-names")), no_mangle)]
+pub unsafe extern "C" fn memmove(dest: *mut u8, src: *const u8, n: usize) -> *mut u8 {
+    if src < dest as *const u8 {
+        // copy from end
+        let mut i = n;
+        while i != 0 {
+            i -= 1;
+            *dest.offset(i as isize) = *src.offset(i as isize);
+        }
+    } else {
+        // copy from beginning
+        let mut i = 0;
+        while i < n {
+            *dest.offset(i as isize) = *src.offset(i as isize);
+            i += 1;
+        }
+    }
+    dest
+}
+
+#[cfg_attr(all(feature = "mem", not(feature = "mangled-names")), no_mangle)]
+pub unsafe extern "C" fn memset(s: *mut u8, c: c_int, n: usize) -> *mut u8 {
+    let mut i = 0;
+    while i < n {
+        *s.offset(i as isize) = c as u8;
+        i += 1;
+    }
+    s
+}
+
+#[cfg_attr(all(feature = "mem", not(feature = "mangled-names")), no_mangle)]
+pub unsafe extern "C" fn memcmp(s1: *const u8, s2: *const u8, n: usize) -> i32 {
+    let mut i = 0;
+    while i < n {
+        let a = *s1.offset(i as isize);
+        let b = *s2.offset(i as isize);
+        if a != b {
+            return a as i32 - b as i32;
+        }
+        i += 1;
+    }
+    0
+}
+
+#[cfg_attr(all(feature = "mem", not(feature = "mangled-names")), no_mangle)]
+pub unsafe extern "C" fn bcmp(s1: *const u8, s2: *const u8, n: usize) -> i32 {
+    memcmp(s1, s2, n)
+}

src/mem/mod.rs

@@ -5,69 +5,15 @@ type c_int = i16;
 #[cfg(not(target_pointer_width = "16"))]
 type c_int = i32;
 
+// memcpy and friends have optimized implementations on some architectures
+#[path = "fallback.rs"]
+mod memcpy;
+pub use self::memcpy::*;
+
 use core::intrinsics::{atomic_load_unordered, atomic_store_unordered, exact_div};
 use core::mem;
 use core::ops::{BitOr, Shl};
 
-#[cfg_attr(all(feature = "mem", not(feature = "mangled-names")), no_mangle)]
-pub unsafe extern "C" fn memcpy(dest: *mut u8, src: *const u8, n: usize) -> *mut u8 {
-    let mut i = 0;
-    while i < n {
-        *dest.offset(i as isize) = *src.offset(i as isize);
-        i += 1;
-    }
-    dest
-}
-
-#[cfg_attr(all(feature = "mem", not(feature = "mangled-names")), no_mangle)]
-pub unsafe extern "C" fn memmove(dest: *mut u8, src: *const u8, n: usize) -> *mut u8 {
-    if src < dest as *const u8 {
-        // copy from end
-        let mut i = n;
-        while i != 0 {
-            i -= 1;
-            *dest.offset(i as isize) = *src.offset(i as isize);
-        }
-    } else {
-        // copy from beginning
-        let mut i = 0;
-        while i < n {
-            *dest.offset(i as isize) = *src.offset(i as isize);
-            i += 1;
-        }
-    }
-    dest
-}
-
-#[cfg_attr(all(feature = "mem", not(feature = "mangled-names")), no_mangle)]
-pub unsafe extern "C" fn memset(s: *mut u8, c: c_int, n: usize) -> *mut u8 {
-    let mut i = 0;
-    while i < n {
-        *s.offset(i as isize) = c as u8;
-        i += 1;
-    }
-    s
-}
-
-#[cfg_attr(all(feature = "mem", not(feature = "mangled-names")), no_mangle)]
-pub unsafe extern "C" fn memcmp(s1: *const u8, s2: *const u8, n: usize) -> i32 {
-    let mut i = 0;
-    while i < n {
-        let a = *s1.offset(i as isize);
-        let b = *s2.offset(i as isize);
-        if a != b {
-            return a as i32 - b as i32;
-        }
-        i += 1;
-    }
-    0
-}
-
-#[cfg_attr(all(feature = "mem", not(feature = "mangled-names")), no_mangle)]
-pub unsafe extern "C" fn bcmp(s1: *const u8, s2: *const u8, n: usize) -> i32 {
-    memcmp(s1, s2, n)
-}
-
 // `bytes` must be a multiple of `mem::size_of::<T>()`
 fn memcpy_element_unordered_atomic<T: Copy>(dest: *mut T, src: *const T, bytes: usize) {
     unsafe {