Adds new intrinsic declaration

Author: aaishwarymishra

library/core/src/intrinsics/mod.rs

@@ -3577,7 +3577,6 @@ pub const fn discriminant_value<T>(_v: &T) -> <T as DiscriminantKind>::Discrimin
     unimplemented!()
 }
 
-extern "rust-intrinsic" {
     /// Rust's "try catch" construct for unwinding. Invokes the function pointer `try_fn` with the
     /// data pointer `data`, and calls `catch_fn` if unwinding occurs while `try_fn` runs.
     ///
@@ -3594,18 +3593,26 @@ extern "rust-intrinsic" {
     ///
     /// For more information, see the compiler's source, as well as the documentation for the stable
     /// version of this intrinsic, `std::panic::catch_unwind`.
+    #[rustc_intrinsic]
+    #[rustc_intrinsic_must_be_overridden]
     #[rustc_nounwind]
-    pub fn catch_unwind(try_fn: fn(*mut u8), data: *mut u8, catch_fn: fn(*mut u8, *mut u8)) -> i32;
+    pub unsafe fn catch_unwind(_try_fn: fn(*mut u8), _data: *mut u8, _catch_fn: fn(*mut u8, *mut u8)) -> i32 {
+        unreachable!() 
+    }
 
     /// Emits a `nontemporal` store, which gives a hint to the CPU that the data should not be held
     /// in cache. Except for performance, this is fully equivalent to `ptr.write(val)`.
     ///
     /// Not all architectures provide such an operation. For instance, x86 does not: while `MOVNT`
     /// exists, that operation is *not* equivalent to `ptr.write(val)` (`MOVNT` writes can be reordered
     /// in ways that are not allowed for regular writes).
+    #[rustc_intrinsic]
+    #[rustc_intrinsic_must_be_overridden]
     #[rustc_nounwind]
-    pub fn nontemporal_store<T>(ptr: *mut T, val: T);
-}
+    pub unsafe fn nontemporal_store<T>(_ptr: *mut T, _val: T) {
+        unreachable!() 
+    }
+
 
 /// See documentation of `<*const T>::offset_from` for details.
 #[rustc_intrinsic_const_stable_indirect]