Auto merge of rust-lang#15244 - HKalbasi:mir, r=HKalbasi

Support read_via_copy intrinsic

Author: bors

crates/hir-ty/src/consteval/tests/intrinsics.rs

@@ -163,6 +163,24 @@ fn transmute() {
     );
 }
 
+#[test]
+fn read_via_copy() {
+    check_number(
+        r#"
+        extern "rust-intrinsic" {
+            pub fn read_via_copy<T>(e: *const T) -> T;
+            pub fn volatile_load<T>(e: *const T) -> T;
+        }
+
+        const GOAL: i32 = {
+            let x = 2;
+            read_via_copy(&x) + volatile_load(&x)
+        };
+        "#,
+        4,
+    );
+}
+
 #[test]
 fn const_eval_select() {
     check_number(

crates/hir-ty/src/mir/eval/shim.rs

@@ -888,6 +888,13 @@ impl Evaluator<'_> {
                 }
                 not_supported!("FnOnce was not available for executing const_eval_select");
             }
+            "read_via_copy" | "volatile_load" => {
+                let [arg] = args else {
+                    return Err(MirEvalError::TypeError("read_via_copy args are not provided"));
+                };
+                let addr = Address::from_bytes(arg.interval.get(self)?)?;
+                destination.write_from_interval(self, Interval { addr, size: destination.size })
+            }
             _ => not_supported!("unknown intrinsic {name}"),
         }
     }