Attempt to use `intrinsics!`

src/int/mod.rs

@@ -301,64 +301,67 @@ macro_rules! impl_wide_int {
 impl_wide_int!(u32, u64, 32);
 impl_wide_int!(u64, u128, 64);
 
-#[no_mangle]
-#[cfg(any(
-    target_pointer_width = "16",
-    target_pointer_width = "32",
-    target_pointer_width = "64"
-))]
-pub extern "C" fn __clzsi2(mut x: usize) -> usize {
-    // TODO: const this? Would require const-if
-    let mut y: usize;
-    let mut n: usize = {
+intrinsics! {
+    #[cfg(any(
+        target_pointer_width = "16",
+        target_pointer_width = "32",
+        target_pointer_width = "64"
+    ))]
+    pub extern "C" fn __clzsi2(x: usize) -> usize {
+        // TODO: const this? Would require const-if
+        // Note(Lokathor): the `intrinsics!` macro can't process mut inputs
+        let mut x = x; 
+        let mut y: usize;
+        let mut n: usize = {
+            #[cfg(target_pointer_width = "64")]
+            {
+                64
+            }
+            #[cfg(target_pointer_width = "32")]
+            {
+                32
+            }
+            #[cfg(target_pointer_width = "16")]
+            {
+                16
+            }
+        };
         #[cfg(target_pointer_width = "64")]
         {
-            64
+            y = x >> 32;
+            if y != 0 {
+                n -= 32;
+                x = y;
+            }
         }
-        #[cfg(target_pointer_width = "32")]
+        #[cfg(any(target_pointer_width = "32", target_pointer_width = "64"))]
         {
-            32
+            y = x >> 16;
+            if y != 0 {
+                n -= 16;
+                x = y;
+            }
         }
-        #[cfg(target_pointer_width = "16")]
-        {
-            16
+        y = x >> 8;
+        if y != 0 {
+            n -= 8;
+            x = y;
         }
-    };
-    #[cfg(target_pointer_width = "64")]
-    {
-        y = x >> 32;
+        y = x >> 4;
         if y != 0 {
-            n -= 32;
+            n -= 4;
             x = y;
         }
-    }
-    #[cfg(any(target_pointer_width = "32", target_pointer_width = "64"))]
-    {
-        y = x >> 16;
+        y = x >> 2;
         if y != 0 {
-            n -= 16;
+            n -= 2;
             x = y;
         }
-    }
-    y = x >> 8;
-    if y != 0 {
-        n -= 8;
-        x = y;
-    }
-    y = x >> 4;
-    if y != 0 {
-        n -= 4;
-        x = y;
-    }
-    y = x >> 2;
-    if y != 0 {
-        n -= 2;
-        x = y;
-    }
-    y = x >> 1;
-    if y != 0 {
-        n - 2
-    } else {
-        n - x
+        y = x >> 1;
+        if y != 0 {
+            n - 2
+        } else {
+            n - x
+        }
     }
 }