constify exact_div intrinsic

compiler/rustc_const_eval/src/interpret/intrinsics.rs

@@ -243,6 +243,11 @@ impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
                 let discr_val = self.read_discriminant(&place.into())?.0;
                 self.write_scalar(discr_val, dest)?;
             }
+            sym::exact_div => {
+                let l = self.read_immediate(&args[0])?;
+                let r = self.read_immediate(&args[1])?;
+                self.exact_div(&l, &r, dest)?;
+            }
             sym::unchecked_shl
             | sym::unchecked_shr
             | sym::unchecked_add

library/core/src/intrinsics.rs

@@ -1851,6 +1851,7 @@ extern "rust-intrinsic" {
     /// `x % y != 0` or `y == 0` or `x == T::MIN && y == -1`
     ///
     /// This intrinsic does not have a stable counterpart.
+    #[rustc_const_unstable(feature = "const_exact_div", issue = "none")]
     pub fn exact_div<T: Copy>(x: T, y: T) -> T;
 
     /// Performs an unchecked division, resulting in undefined behavior

library/core/src/lib.rs

@@ -109,6 +109,7 @@
 #![feature(const_cmp)]
 #![feature(const_discriminant)]
 #![feature(const_eval_select)]
+#![feature(const_exact_div)]
 #![feature(const_float_bits_conv)]
 #![feature(const_float_classify)]
 #![feature(const_fmt_arguments_new)]

src/tools/miri/src/shims/intrinsics/mod.rs

@@ -368,11 +368,6 @@ pub trait EvalContextExt<'mir, 'tcx: 'mir>: crate::MiriInterpCxExt<'mir, 'tcx> {
             }
 
             // Other
-            "exact_div" => {
-                let [num, denom] = check_arg_count(args)?;
-                this.exact_div(&this.read_immediate(num)?, &this.read_immediate(denom)?, dest)?;
-            }
-
             "breakpoint" => {
                 let [] = check_arg_count(args)?;
                 // normally this would raise a SIGTRAP, which aborts if no debugger is connected