1 files changed, 62 insertions, 0 deletions
diff --git a/vendor/half/src/leading_zeros.rs b/vendor/half/src/leading_zeros.rs
new file mode 100644
index 0000000..6c73148
--- /dev/null
+++ b/vendor/half/src/leading_zeros.rs
@@ -0,0 +1,62 @@
+// https://doc.rust-lang.org/std/primitive.u16.html#method.leading_zeros
+
+#[cfg(not(any(all(
+    target_arch = "spirv",
+    not(all(
+        target_feature = "IntegerFunctions2INTEL",
+        target_feature = "SPV_INTEL_shader_integer_functions2"
+    ))
+))))]
+pub(crate) const fn leading_zeros_u16(x: u16) -> u32 {
+    x.leading_zeros()
+}
+
+#[cfg(all(
+    target_arch = "spirv",
+    not(all(
+        target_feature = "IntegerFunctions2INTEL",
+        target_feature = "SPV_INTEL_shader_integer_functions2"
+    ))
+))]
+pub(crate) const fn leading_zeros_u16(x: u16) -> u32 {
+    leading_zeros_u16_fallback(x)
+}
+
+#[cfg(any(
+    test,
+    all(
+        target_arch = "spirv",
+        not(all(
+            target_feature = "IntegerFunctions2INTEL",
+            target_feature = "SPV_INTEL_shader_integer_functions2"
+        ))
+    )
+))]
+const fn leading_zeros_u16_fallback(mut x: u16) -> u32 {
+    use crunchy::unroll;
+    let mut c = 0;
+    let msb = 1 << 15;
+    unroll! { for i in 0 .. 16 {
+        if x & msb == 0 {
+            c += 1;
+        } else {
+            return c;
+        }
+        #[allow(unused_assignments)]
+        if i < 15 {
+            x <<= 1;
+        }
+    }}
+    c
+}
+
+#[cfg(test)]
+mod test {
+
+    #[test]
+    fn leading_zeros_u16_fallback() {
+        for x in [44, 97, 304, 1179, 23571] {
+            assert_eq!(super::leading_zeros_u16_fallback(x), x.leading_zeros());
+        }
+    }
+}