Add RDTSC and RDTSCP intrinsics (rust-lang#264)

Author: shepmaster

coresimd/src/x86/i586/mod.rs

@@ -5,6 +5,8 @@ pub use self::xsave::*;
 
 pub use self::bswap::*;
 
+pub use self::rdtsc::*;
+
 pub use self::sse::*;
 pub use self::sse2::*;
 pub use self::sse3::*;
@@ -26,6 +28,8 @@ mod xsave;
 
 mod bswap;
 
+mod rdtsc;
+
 mod sse;
 mod sse2;
 mod sse3;

coresimd/src/x86/i586/rdtsc.rs

@@ -0,0 +1,69 @@
+#[cfg(test)]
+use stdsimd_test::assert_instr;
+
+/// Reads the current value of the processor’s time-stamp counter.
+///
+/// The processor monotonically increments the time-stamp counter MSR
+/// every clock cycle and resets it to 0 whenever the processor is
+/// reset.
+///
+/// The RDTSC instruction is not a serializing instruction. It does
+/// not necessarily wait until all previous instructions have been
+/// executed before reading the counter. Similarly, subsequent
+/// instructions may begin execution before the read operation is
+/// performed.
+///
+/// On processors that support the Intel 64 architecture, the
+/// high-order 32 bits of each of RAX and RDX are cleared.
+#[inline(always)]
+#[cfg_attr(test, assert_instr(rdtsc))]
+pub unsafe fn _rdtsc() -> u64 {
+    rdtsc()
+}
+
+/// Reads the current value of the processor’s time-stamp counter and
+/// the IA32_TSC_AUX MSR.
+///
+/// The processor monotonically increments the time-stamp counter MSR
+/// every clock cycle and resets it to 0 whenever the processor is
+/// reset.
+///
+/// The RDTSCP instruction waits until all previous instructions have
+/// been executed before reading the counter. However, subsequent
+/// instructions may begin execution before the read operation is
+/// performed.
+///
+/// On processors that support the Intel 64 architecture, the
+/// high-order 32 bits of each of RAX, RDX, and RCX are cleared.
+#[inline(always)]
+#[cfg_attr(test, assert_instr(rdtscp))]
+pub unsafe fn _rdtscp(aux: *mut u32) -> u64 {
+    rdtscp(aux as *mut _)
+}
+
+#[allow(improper_ctypes)]
+extern "C" {
+    #[link_name = "llvm.x86.rdtsc"]
+    fn rdtsc() -> u64;
+    #[link_name = "llvm.x86.rdtscp"]
+    fn rdtscp(aux: *mut u8) -> u64;
+}
+
+#[cfg(test)]
+mod tests {
+    use stdsimd_test::simd_test;
+    use x86::i586::rdtsc;
+
+    #[simd_test = "sse2"]
+    unsafe fn _rdtsc() {
+        let r = rdtsc::_rdtsc();
+        assert_ne!(r, 0); // The chances of this being 0 are infinitesimal
+    }
+
+    #[simd_test = "sse2"]
+    unsafe fn _rdtscp() {
+        let mut aux = 0;
+        let r = rdtsc::_rdtscp(&mut aux);
+        assert_ne!(r, 0); // The chances of this being 0 are infinitesimal
+    }
+}