nak: Add a util library

Currently, all we do here is implement div_ceil() and next_multiple_of()
because these helpers are super useful but currently an experimental
Rust feature.  This should be a drop-in for the feature so we can delete
it once the feature stabilizes with little to no effect.

Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/24998>

src/nouveau/compiler/nak.rs

@@ -8,6 +8,7 @@ mod nak_ir;
 mod nak_opt_copy_prop;
 mod nak_opt_dce;
 mod nir;
+mod util;
 
 use nak_bindings::*;
 use nak_from_nir::*;

src/nouveau/compiler/util.rs

@@ -0,0 +1,54 @@
+/*
+ * Copyright © 2022 Collabora, Ltd.
+ * SPDX-License-Identifier: MIT
+ */
+
+use std::ops::Mul;
+
+/** Provides div_ceil()
+ *
+ * This is a nightly feature so we can't rely on it yet.
+ * https://github.com/rust-lang/rust/issues/88581
+ */
+pub trait DivCeil<Rhs = Self> {
+    type Output;
+
+    fn div_ceil(&self, a: Rhs) -> Self::Output;
+}
+
+macro_rules! impl_uint_div_ceil {
+    ($ty: ty) => {
+        impl DivCeil<$ty> for $ty {
+            type Output = $ty;
+
+            fn div_ceil(&self, d: $ty) -> $ty {
+                (*self + (d - 1)) / d
+            }
+        }
+    };
+}
+
+impl_uint_div_ceil!(u8);
+impl_uint_div_ceil!(u16);
+impl_uint_div_ceil!(u32);
+impl_uint_div_ceil!(u64);
+impl_uint_div_ceil!(usize);
+
+/** Provides next_multiple_of()
+ *
+ * This is a nightly feature so we can't rely on it yet.
+ * https://github.com/rust-lang/rust/issues/88581
+ */
+pub trait NextMultipleOf<Rhs = Self> {
+    type Output;
+
+    fn next_multiple_of(&self, a: Rhs) -> Self::Output;
+}
+
+impl<T: Copy + DivCeil<Output = T> + Mul<Output = T>> NextMultipleOf<T> for T {
+    type Output = T;
+
+    fn next_multiple_of(&self, a: T) -> T {
+        self.div_ceil(a) * a
+    }
+}