implement the write_bytes() intrinsic

src/terminator/intrinsic.rs

@@ -402,6 +402,18 @@ impl<'a, 'tcx> EvalContext<'a, 'tcx> {
                 }
             }
 
+            "write_bytes" => {
+                let u8 = self.tcx.types.u8;
+                let ty = substs.type_at(0);
+                let ty_align = self.type_align(ty)?;
+                let val_byte = self.value_to_primval(arg_vals[1], u8)?.to_u128()? as u8;
+                let size = self.type_size(ty)?.expect("write_bytes() type must be sized");
+                let ptr = arg_vals[0].read_ptr(&self.memory)?;
+                let count = self.value_to_primval(arg_vals[2], usize)?.to_u64()?;
+                self.memory.check_align(ptr, size * count, ty_align)?;
+                self.memory.write_repeat(ptr, val_byte, size * count)?;
+            }
+
             name => return Err(EvalError::Unimplemented(format!("unimplemented intrinsic: {}", name))),
         }
 

tests/run-pass/write-bytes.rs

@@ -0,0 +1,45 @@
+#[repr(C)]
+#[derive(Copy, Clone)]
+struct Foo {
+    a: u64,
+    b: u64,
+    c: u64,
+}
+
+fn main() {
+    const LENGTH: usize = 10;
+    let mut v: [u64; LENGTH] = [0; LENGTH];
+
+    for idx in 0..LENGTH {
+        assert_eq!(v[idx], 0);
+    }
+
+    unsafe {
+        let p = v.as_mut_ptr();
+        ::std::ptr::write_bytes(p, 0xab, LENGTH);
+    }
+
+    for idx in 0..LENGTH {
+        assert_eq!(v[idx], 0xabababababababab);
+    }
+
+    // -----
+
+    let mut w: [Foo; LENGTH] = [Foo { a: 0, b: 0, c: 0 }; LENGTH];
+    for idx in 0..LENGTH {
+        assert_eq!(w[idx].a, 0);
+        assert_eq!(w[idx].b, 0);
+        assert_eq!(w[idx].c, 0);
+    }
+
+    unsafe {
+        let p = w.as_mut_ptr();
+        ::std::ptr::write_bytes(p, 0xcd, LENGTH);
+    }
+
+    for idx in 0..LENGTH {
+        assert_eq!(w[idx].a, 0xcdcdcdcdcdcdcdcd);
+        assert_eq!(w[idx].b, 0xcdcdcdcdcdcdcdcd);
+        assert_eq!(w[idx].c, 0xcdcdcdcdcdcdcdcd);
+    }
+}