1 files changed, 46 insertions, 0 deletions
diff --git a/zjit/src/utils.rs b/zjit/src/utils.rs
new file mode 100644
index 0000000000..f12ab44c95
--- /dev/null
+++ b/zjit/src/utils.rs
@@ -0,0 +1,46 @@
+/// Trait for casting to [usize] that allows you to say `.as_usize()`.
+/// Implementation conditional on the cast preserving the numeric value on
+/// all inputs and being inexpensive.
+///
+/// [usize] is only guaranteed to be more than 16-bit wide, so we can't use
+/// `.into()` to cast an `u32` or an `u64` to a `usize` even though in all
+/// the platforms YJIT supports these two casts are pretty much no-ops.
+/// We could say `as usize` or `.try_convert().unwrap()` everywhere
+/// for those casts but they both have undesirable consequences if and when
+/// we decide to support 32-bit platforms. Unfortunately we can't implement
+/// [::core::convert::From] for [usize] since both the trait and the type are
+/// external. Naming the method `into()` also runs into naming conflicts.
+pub(crate) trait IntoUsize {
+    /// Convert to usize. Implementation conditional on width of [usize].
+    fn as_usize(self) -> usize;
+}
+
+#[cfg(target_pointer_width = "64")]
+impl IntoUsize for u64 {
+    fn as_usize(self) -> usize {
+        self as usize
+    }
+}
+
+#[cfg(target_pointer_width = "64")]
+impl IntoUsize for u32 {
+    fn as_usize(self) -> usize {
+        self as usize
+    }
+}
+
+impl IntoUsize for u16 {
+    /// Alias for `.into()`. For convenience so you could use the trait for
+    /// all unsgined types.
+    fn as_usize(self) -> usize {
+        self.into()
+    }
+}
+
+impl IntoUsize for u8 {
+    /// Alias for `.into()`. For convenience so you could use the trait for
+    /// all unsgined types.
+    fn as_usize(self) -> usize {
+        self.into()
+    }
+}