[abm] use lzcnt and popcnt features

Author: gnzlbg

src/x86/abm.rs

@@ -1,10 +1,6 @@
 //! Advanced Bit Manipulation (ABM) instructions
 //! 
-//! That is, POPCNT and LZCNT. These instructions have their own CPUID bits to
-//! indicate support.
-//!
-//! TODO: it is unclear which target feature to use here. SSE4.2 should be good
-//! enough but we might need to use BMI for LZCNT if there are any problems.
+//! The POPCNT and LZCNT have their own CPUID bits to indicate support.
 //!
 //! The references are:
 //!
@@ -19,50 +15,50 @@
 ///
 /// When the operand is zero, it returns its size in bits.
 #[inline(always)]
-#[target_feature = "+sse4.2"]
+#[target_feature = "+lzcnt"]
 pub fn _lzcnt_u32(x: u32) -> u32 { x.leading_zeros() }
 
 /// Counts the leading most significant zero bits.
 ///
 /// When the operand is zero, it returns its size in bits.
 #[inline(always)]
-#[target_feature = "+sse4.2"]
+#[target_feature = "+lzcnt"]
 pub fn _lzcnt_u64(x: u64) -> u64 { x.leading_zeros() as u64 }
 
 /// Counts the bits that are set.
 #[inline(always)]
-#[target_feature = "+sse4.2"]
+#[target_feature = "+popcnt"]
 pub fn _popcnt32(x: u32) -> u32 { x.count_ones() }
 
 /// Counts the bits that are set.
 #[inline(always)]
-#[target_feature = "+sse4.2"]
+#[target_feature = "+popcnt"]
 pub fn _popcnt64(x: u64) -> u64 { x.count_ones() as u64 }
 
-#[cfg(all(test, target_feature = "sse4.2", any(target_arch = "x86", target_arch = "x86_64")))]
+#[cfg(all(test, target_feature = "bmi", any(target_arch = "x86", target_arch = "x86_64")))]
 mod tests {
     use x86::abm;
 
     #[test]
-    #[target_feature = "+sse4.2"]
+    #[target_feature = "+lzcnt"]
     fn _lzcnt_u32() {
         assert_eq!(abm::_lzcnt_u32(0b0101_1010u32), 25u32);
     }
 
     #[test]
-    #[target_feature = "+sse4.2"]
+    #[target_feature = "+lzcnt"]
     fn _lzcnt_u64() {
         assert_eq!(abm::_lzcnt_u64(0b0101_1010u64), 57u64);
     }
 
     #[test]
-    #[target_feature = "+sse4.2"]
+    #[target_feature = "+popcnt"]
     fn _popcnt32() {
         assert_eq!(abm::_popcnt32(0b0101_1010u32), 4);
     }
 
     #[test]
-    #[target_feature = "+sse4.2"]
+    #[target_feature = "+popcnt"]
     fn _popcnt64() {
         assert_eq!(abm::_popcnt64(0b0101_1010u64), 4);
     }