Merge pull request #1925 from sayantn/make-const

Make X86 intrinsics `const`

Author: Amanieu

crates/core_arch/src/lib.rs

@@ -34,7 +34,10 @@
     aarch64_unstable_target_feature,
     bigint_helper_methods,
     funnel_shifts,
-    avx10_target_feature
+    avx10_target_feature,
+    const_trait_impl,
+    const_cmp,
+    const_eval_select
 )]
 #![cfg_attr(test, feature(test, abi_vectorcall, stdarch_internal))]
 #![deny(clippy::missing_inline_in_public_items)]

crates/core_arch/src/mod.rs

@@ -5,6 +5,11 @@
 #[macro_use]
 mod macros;
 
+#[cfg(test)]
+mod test;
+#[cfg(test)]
+use test::assert_eq_const;
+
 #[cfg(any(target_arch = "riscv32", target_arch = "riscv64", doc))]
 mod riscv_shared;
 

crates/core_arch/src/simd.rs

@@ -3,13 +3,15 @@
 #![allow(non_camel_case_types)]
 
 #[inline(always)]
-pub(crate) unsafe fn simd_imax<T: Copy>(a: T, b: T) -> T {
+#[rustc_const_unstable(feature = "stdarch_const_helpers", issue = "none")]
+pub(crate) const unsafe fn simd_imax<T: Copy>(a: T, b: T) -> T {
     let mask: T = crate::intrinsics::simd::simd_gt(a, b);
     crate::intrinsics::simd::simd_select(mask, a, b)
 }
 
 #[inline(always)]
-pub(crate) unsafe fn simd_imin<T: Copy>(a: T, b: T) -> T {
+#[rustc_const_unstable(feature = "stdarch_const_helpers", issue = "none")]
+pub(crate) const unsafe fn simd_imin<T: Copy>(a: T, b: T) -> T {
     let mask: T = crate::intrinsics::simd::simd_lt(a, b);
     crate::intrinsics::simd::simd_select(mask, a, b)
 }
@@ -35,7 +37,8 @@ macro_rules! simd_ty {
             }
             // FIXME: Workaround rust@60637
             #[inline(always)]
-            pub(crate) fn splat(value: $elem_type) -> Self {
+            #[rustc_const_unstable(feature = "stdarch_const_helpers", issue = "none")]
+            pub(crate) const fn splat(value: $elem_type) -> Self {
                 #[derive(Copy, Clone)]
                 #[repr(simd)]
                 struct JustOne([$elem_type; 1]);
@@ -50,12 +53,12 @@ macro_rules! simd_ty {
             /// Use for testing only.
             // FIXME: Workaround rust@60637
             #[inline(always)]
-            pub(crate) fn extract(&self, index: usize) -> $elem_type {
+            pub(crate) const fn extract(&self, index: usize) -> $elem_type {
                 self.as_array()[index]
             }
 
             #[inline]
-            pub(crate) fn as_array(&self) -> &[$elem_type; $len] {
+            pub(crate) const fn as_array(&self) -> &[$elem_type; $len] {
                 let simd_ptr: *const Self = self;
                 let array_ptr: *const [$elem_type; $len] = simd_ptr.cast();
                 // SAFETY: We can always read the prefix of a simd type as an array.
@@ -65,7 +68,8 @@ macro_rules! simd_ty {
             }
         }
 
-        impl core::cmp::PartialEq for $id {
+        #[rustc_const_unstable(feature = "stdarch_const_helpers", issue = "none")]
+        const impl core::cmp::PartialEq for $id {
             #[inline]
             fn eq(&self, other: &Self) -> bool {
                 self.as_array() == other.as_array()
@@ -101,7 +105,8 @@ macro_rules! simd_m_ty {
 
             // FIXME: Workaround rust@60637
             #[inline(always)]
-            pub(crate) fn splat(value: bool) -> Self {
+            #[rustc_const_unstable(feature = "stdarch_const_helpers", issue = "none")]
+            pub(crate) const fn splat(value: bool) -> Self {
                 #[derive(Copy, Clone)]
                 #[repr(simd)]
                 struct JustOne([$elem_type; 1]);
@@ -112,7 +117,7 @@ macro_rules! simd_m_ty {
             }
 
             #[inline]
-            pub(crate) fn as_array(&self) -> &[$elem_type; $len] {
+            pub(crate) const fn as_array(&self) -> &[$elem_type; $len] {
                 let simd_ptr: *const Self = self;
                 let array_ptr: *const [$elem_type; $len] = simd_ptr.cast();
                 // SAFETY: We can always read the prefix of a simd type as an array.
@@ -122,7 +127,8 @@ macro_rules! simd_m_ty {
             }
         }
 
-        impl core::cmp::PartialEq for $id {
+        #[rustc_const_unstable(feature = "stdarch_const_helpers", issue = "none")]
+        const impl core::cmp::PartialEq for $id {
             #[inline]
             fn eq(&self, other: &Self) -> bool {
                 self.as_array() == other.as_array()

crates/core_arch/src/test.rs

@@ -0,0 +1,25 @@
+use crate::fmt::Debug;
+
+#[track_caller]
+#[allow(unused)]
+pub(crate) fn assert_eq_rt<T: PartialEq + Debug>(a: &T, b: &T) {
+    std::assert_eq!(a, b)
+}
+
+#[allow(unused)]
+macro_rules! assert_eq_const {
+    ($a:expr, $b:expr $(,)?) => {{
+        #[inline(always)]
+        #[rustc_const_unstable(feature = "stdarch_const_helpers", issue = "none")]
+        const fn assert_eq_ct<T: [const] PartialEq>(a: &T, b: &T) {
+            assert!(a == b, concat!("`", stringify!($a), "` != `", stringify!($b), "`"));
+        }
+
+        $crate::intrinsics::const_eval_select((&$a, &$b), assert_eq_ct, $crate::core_arch::test::assert_eq_rt);
+    }};
+    ($a:expr, $b:expr, $($t:tt)+) => {
+        ::std::assert_eq!($a, $b, $($t)+)
+    };
+}
+
+pub(crate) use assert_eq_const;

crates/core_arch/src/x86/abm.rs

@@ -29,7 +29,8 @@ use stdarch_test::assert_instr;
 #[target_feature(enable = "lzcnt")]
 #[cfg_attr(test, assert_instr(lzcnt))]
 #[stable(feature = "simd_x86", since = "1.27.0")]
-pub fn _lzcnt_u32(x: u32) -> u32 {
+#[rustc_const_unstable(feature = "stdarch_const_x86", issue = "149298")]
+pub const fn _lzcnt_u32(x: u32) -> u32 {
     x.leading_zeros()
 }
 
@@ -40,23 +41,25 @@ pub fn _lzcnt_u32(x: u32) -> u32 {
 #[target_feature(enable = "popcnt")]
 #[cfg_attr(test, assert_instr(popcnt))]
 #[stable(feature = "simd_x86", since = "1.27.0")]
-pub fn _popcnt32(x: i32) -> i32 {
+#[rustc_const_unstable(feature = "stdarch_const_x86", issue = "149298")]
+pub const fn _popcnt32(x: i32) -> i32 {
     x.count_ones() as i32
 }
 
 #[cfg(test)]
 mod tests {
+    use crate::core_arch::assert_eq_const as assert_eq;
     use stdarch_test::simd_test;
 
     use crate::core_arch::x86::*;
 
     #[simd_test(enable = "lzcnt")]
-    unsafe fn test_lzcnt_u32() {
+    const unsafe fn test_lzcnt_u32() {
         assert_eq!(_lzcnt_u32(0b0101_1010), 25);
     }
 
     #[simd_test(enable = "popcnt")]
-    unsafe fn test_popcnt32() {
+    const unsafe fn test_popcnt32() {
         assert_eq!(_popcnt32(0b0101_1010), 4);
     }
 }