Use the core::arch intrinsics where possible

src/controlregs.rs

@@ -1,6 +1,8 @@
 //! Functions to read and write control registers.
 //! See Intel Vol. 3a Section 2.5, especially Figure 2-7.
 
+use arch::{_xgetbv, _xsetbv};
+
 bitflags! {
     pub struct Cr0: usize {
         const CR0_ENABLE_PAGING = 1 << 31;
@@ -102,16 +104,11 @@ pub unsafe fn cr4_write(val: Cr4) {
 /// Read Extended Control Register XCR0.
 /// Only supported if CR4_ENABLE_OS_XSAVE is set.
 pub unsafe fn xcr0() -> Xcr0 {
-    let high: u32;
-    let low: u32;
-    asm!("xgetbv" : "={eax}"(low), "={edx}"(high) : "{ecx}"(0));
-    Xcr0::from_bits_truncate((high as u64) << 32 | low as u64)
+    Xcr0::from_bits_truncate(_xgetbv(0))
 }
 
 /// Write to Extended Control Register XCR0.
 /// Only supported if CR4_ENABLE_OS_XSAVE is set.
 pub unsafe fn xcr0_write(val: Xcr0) {
-    let high: u32 = (val.bits >> 32) as u32;
-    let low: u32 = val.bits as u32;
-    asm!("xsetbv" :: "{eax}"(low), "{ecx}"(0), "{edx}"(high));
+    _xsetbv(0, val.bits);
 }

src/lib.rs

@@ -15,6 +15,11 @@ extern crate phf;
 #[macro_use]
 extern crate std;
 
+#[cfg(target_arch = "x86")]
+use core::arch::x86 as arch;
+#[cfg(target_arch = "x86_64")]
+use core::arch::x86_64 as arch;
+
 macro_rules! check_flag {
     ($doc:meta, $fun:ident, $flag:expr) => (
         #[$doc]

src/time.rs

@@ -1,5 +1,8 @@
 //! Functions to read time stamp counters on x86.
 
+use core::mem;
+use arch::{_rdtsc, __rdtscp};
+
 /// Read the time stamp counter.
 ///
 /// The RDTSC instruction is not a serializing instruction.
@@ -13,13 +16,8 @@
 /// # Safety
 /// * Causes a GP fault if the TSD flag in register CR4 is set and the CPL
 ///   is greater than 0.
-#[allow(unused_mut)]
 pub unsafe fn rdtsc() -> u64 {
-    let mut low: u32;
-    let mut high: u32;
-
-    asm!("rdtsc" : "={eax}" (low), "={edx}" (high));
-    ((high as u64) << 32) | (low as u64)
+    mem::transmute(_rdtsc())
 }
 
 /// Read the time stamp counter.
@@ -35,11 +33,7 @@ pub unsafe fn rdtsc() -> u64 {
 /// # Safety
 /// * Causes a GP fault if the TSD flag in register CR4 is set and the
 ///   CPL is greater than 0.
-#[allow(unused_mut)]
 pub unsafe fn rdtscp() -> u64 {
-    let mut low: u32;
-    let mut high: u32;
-
-    asm!("rdtscp" : "={eax}" (low), "={edx}" (high) ::: "volatile");
-    ((high as u64) << 32) | (low as u64)
+    let mut _aux = 0;
+    __rdtscp(&mut _aux)
 }