From 63dcb526a753eb48b7c6bd757d60360e9c908c28 Mon Sep 17 00:00:00 2001
From: Elias Kauppi <elkku.kauppi@gmail.com>
Date: Thu, 14 Mar 2024 23:02:11 +0200
Subject: [PATCH] non-x86_64 support fixes

---
 src/deinterleave.rs |  4 ++++
 src/interleave.rs   |  4 ++++
 src/lib.rs          | 30 +++++++++++++++++++++++++-----
 3 files changed, 33 insertions(+), 5 deletions(-)

diff --git a/src/deinterleave.rs b/src/deinterleave.rs
index a67831c..49e0cb3 100644
--- a/src/deinterleave.rs
+++ b/src/deinterleave.rs
@@ -98,6 +98,7 @@ pub trait DeinterleaveBMI2<const N: usize>: Deinterleave<N> {
     unsafe fn deinterleave_bmi2(self, lsb: usize) -> <Self as Deinterleave<N>>::Output;
 }
 
+#[cfg(target_arch = "x86_64")]
 macro_rules! impl_deinterleave_bmi2_32 {
     ($($impl_type:ty => $dim:expr);*) => {
         $(
@@ -114,6 +115,7 @@ macro_rules! impl_deinterleave_bmi2_32 {
     };
 }
 
+#[cfg(target_arch = "x86_64")]
 macro_rules! impl_deinterleave_bmi2_64 {
     ($($impl_type:ty => $dim:expr);*) => {
         $(
@@ -130,6 +132,7 @@ macro_rules! impl_deinterleave_bmi2_64 {
     };
 }
 
+#[cfg(target_arch = "x86_64")]
 impl_deinterleave_bmi2_32! {
     u16 => 2;
     u32 => 2;
@@ -137,6 +140,7 @@ impl_deinterleave_bmi2_32! {
     u32 => 4
 }
 
+#[cfg(target_arch = "x86_64")]
 impl_deinterleave_bmi2_64! {
     u64 => 2;
     u64 => 3;
diff --git a/src/interleave.rs b/src/interleave.rs
index bc4c0ed..4862eb8 100644
--- a/src/interleave.rs
+++ b/src/interleave.rs
@@ -100,6 +100,7 @@ pub trait InterleaveBMI2<const N: usize>: Interleave<N> {
     unsafe fn interleave_bmi2(self) -> <Self as Interleave<N>>::Output;
 }
 
+#[cfg(target_arch = "x86_64")]
 macro_rules! impl_interleave_bmi2_32 {
     ($($dim:expr, $impl_type:ty);*) => {
         $(
@@ -113,6 +114,7 @@ macro_rules! impl_interleave_bmi2_32 {
     };
 }
 
+#[cfg(target_arch = "x86_64")]
 macro_rules! impl_interleave_bmi2_64 {
     ($($dim:expr, $impl_type:ty);*) => {
         $(
@@ -126,6 +128,7 @@ macro_rules! impl_interleave_bmi2_64 {
     };
 }
 
+#[cfg(target_arch = "x86_64")]
 impl_interleave_bmi2_32! {
     2, u8;
     3, u8;
@@ -133,6 +136,7 @@ impl_interleave_bmi2_32! {
     2, u16
 }
 
+#[cfg(target_arch = "x86_64")]
 impl_interleave_bmi2_64! {
     5, u8;
     6, u8;
diff --git a/src/lib.rs b/src/lib.rs
index 7a94e41..8d6b3b5 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -111,6 +111,8 @@ where
 /// Optionally, you can acquire a [`HardwareSupportToken`](crate::bmi2::HardwareSupportToken), and then call
 /// [`index_of`](crate::bmi2::index_of) and [`coord_of`](crate::bmi2::coord_of) without unsafe.
 ///
+/// Note that the bmi2 instruction set is supported only on modern x86_64 CPUs.
+///
 /// # Examples
 ///
 /// ```
@@ -128,7 +130,7 @@ where
 /// ```
 pub mod bmi2 {
     use crate::{
-        deinterleave::DeinterleaveBMI2, interleave::InterleaveBMI2, util, Deinterleave, Interleave,
+        deinterleave::DeinterleaveBMI2, interleave::InterleaveBMI2, Deinterleave, Interleave,
     };
 
     /// Returns true if the CPU supports the bmi2 instruction set.
@@ -180,7 +182,15 @@ pub mod bmi2 {
         // SAFETY: Having an instance of `HardwareSupportToken` guarantees that
         // the `bmi2` instruction set is supported by the CPU and that it is safe
         // to call `index_of_unchecked`.
-        unsafe { index_of_unchecked(array) }
+        #[cfg(target_arch = "x86_64")]
+        unsafe {
+            index_of_unchecked(array)
+        }
+        #[cfg(not(target_arch = "x86_64"))]
+        {
+            let _ = array;
+            unreachable!("HardwareSupportToken cannot be created on non-x86_64 platforms")
+        }
     }
 
     /// Calculates Z-order curve index for given sequence of coordinates.
@@ -212,13 +222,14 @@ pub mod bmi2 {
     /// ```
     #[inline]
     #[target_feature(enable = "bmi2")]
+    #[cfg(target_arch = "x86_64")]
     pub unsafe fn index_of_unchecked<I, const N: usize>(
         array: [I; N],
     ) -> <I as Interleave<N>>::Output
     where
         I: InterleaveBMI2<N>,
     {
-        util::generic_index_of(array, |idx| idx.interleave_bmi2())
+        crate::util::generic_index_of(array, |idx| idx.interleave_bmi2())
     }
 
     /// Safe wrapper around [`coord_of_unchecked`] that requires a
@@ -235,7 +246,15 @@ pub mod bmi2 {
         // SAFETY: Having an instance of `HardwareSupportToken` guarantees that
         // the `bmi2` instruction set is supported by the CPU and that it is safe
         // to call `coord_of_unchecked`.
-        unsafe { coord_of_unchecked(index) }
+        #[cfg(target_arch = "x86_64")]
+        unsafe {
+            coord_of_unchecked(index)
+        }
+        #[cfg(not(target_arch = "x86_64"))]
+        {
+            let _ = index;
+            unreachable!("HardwareSupportToken cannot be created on non-x86_64 platforms")
+        }
     }
 
     /// Returns the 2D coordinates of the given Z-order curve index.
@@ -269,13 +288,14 @@ pub mod bmi2 {
     /// ```
     #[inline]
     #[target_feature(enable = "bmi2")]
+    #[cfg(target_arch = "x86_64")]
     pub unsafe fn coord_of_unchecked<I, const N: usize>(
         index: I,
     ) -> [<I as Deinterleave<N>>::Output; N]
     where
         I: DeinterleaveBMI2<N> + Copy,
     {
-        util::generic_coord_of(index, |idx, i| idx.deinterleave_bmi2(i))
+        crate::util::generic_coord_of(index, |idx, i| idx.deinterleave_bmi2(i))
     }
 }