[x86] expose cpuid and xgetbv intrinsics

Author: gnzlbg

src/x86/mod.rs

@@ -1,5 +1,7 @@
 //! `x86` and `x86_64` intrinsics.
 
+pub use self::x86::*;
+
 pub use self::sse::*;
 pub use self::sse2::*;
 pub use self::sse3::*;
@@ -28,6 +30,8 @@ mod macros;
 #[macro_use]
 mod runtime;
 
+mod x86;
+
 mod sse;
 mod sse2;
 mod sse3;

src/x86/runtime.rs

@@ -159,32 +159,25 @@ fn test_bit(x: usize, bit: u32) -> bool {
 /// [intel64_ref]: http://www.intel.de/content/dam/www/public/us/en/documents/manuals/64-ia-32-architectures-software-developer-instruction-set-reference-manual-325383.pdf
 /// [amd64_ref]: http://support.amd.com/TechDocs/24594.pdf
 fn detect_features() -> usize {
-    let extended_features_ebx;
-    let proc_info_ecx;
-    let proc_info_edx;
+    use super::x86::{CpuidResult, cpuid};
 
-    unsafe {
-        /// To obtain all feature flags we need two CPUID queries:
+    // 1. EAX=1, ECX=0: Queries "Processor Info and Feature Bits";
+    // Contains information about most x86 features.
+    let CpuidResult {ecx: proc_info_ecx, edx: proc_info_edx, .. }
+    = cpuid(0x0000_0001_u32, 0);
 
-        /// 1. EAX=1, ECX=0: Queries "Processor Info and Feature Bits"
-        /// This gives us most of the CPU features in ECX and EDX (see
-        /// below).
-        asm!("cpuid"
-             : "={ecx}"(proc_info_ecx), "={edx}"(proc_info_edx)
-             : "{eax}"(0x0000_0001_u32), "{ecx}"(0 as u32)
-             : :);
-
-        /// 2. EAX=7, ECX=0: Queries "Extended Features"
-        /// This gives us information about bmi,bmi2, and avx2 support
-        /// (see below); the result in ECX is not currently needed.
-        asm!("cpuid"
-             : "={ebx}"(extended_features_ebx)
-             : "{eax}"(0x0000_0007_u32), "{ecx}"(0 as u32)
-             : :);
-    }
+    // 2. EAX=7, ECX=0: Queries "Extended Features";
+    // Contains information about bmi,bmi2, and avx2 support.
+    let CpuidResult {ebx: extended_features_ebx, .. }
+    = cpuid(0x0000_0007_u32, 0);
 
     let mut value: usize = 0;
 
+    let proc_info_ecx = proc_info_ecx as usize;
+    let proc_info_edx = proc_info_edx as usize;
+
+    let extended_features_ebx = extended_features_ebx as usize;
+
     if test_bit(extended_features_ebx, 3) {
         value = set_bit(value, __Feature::bmi as u32);
     }
@@ -233,18 +226,7 @@ fn detect_features() -> usize {
     // org/mozilla-central/file/64bab5cbb9b6/mozglue/build/SSE.cpp#l190
     //
     if test_bit(proc_info_ecx, 26) && test_bit(proc_info_ecx, 27) {
-        /// XGETBV: reads the contents of the extended control
-        /// register (XCR).
-        unsafe fn xgetbv(xcr_no: u32) -> u64 {
-            let eax: u32;
-            let edx: u32;
-            // xgetbv
-            asm!("xgetbv"
-                 : "={eax}"(eax),  "={edx}"(edx)
-                 : "{ecx}"(xcr_no)
-                 : :);
-            ((edx as u64) << 32) | (eax as u64)
-        }
+        use super::x86::xgetbv;
 
         // This is safe because on x86 `xgetbv` is always available.
         if unsafe { xgetbv(0) } & 6 == 6 {

src/x86/x86.rs

@@ -0,0 +1,62 @@
+//! x86 intrinsics available on all hosts
+
+#[cfg(test)]
+use stdsimd_test::assert_instr;
+
+/// Result of the `cpuid` instruction.
+pub struct CpuidResult {
+    pub eax: u32,
+    pub ebx: u32,
+    pub ecx: u32,
+    pub edx: u32,
+}
+
+/// CPUID instruction.
+///
+/// The `request` parameter is passed in the `eax` register and the `ext`
+/// parameter in the `ecx` register.
+///
+/// The [CPUID Wikipedia page][wiki_cpuid] contains
+/// all the information about which flags to set to query which values, and in
+/// which registers these are reported.
+///
+/// The definitive references are:
+/// - [Intel 64 and IA-32 Architectures Software Developer's Manual Volume 2:
+///   Instruction Set Reference, A-Z][intel64_ref].
+/// - [AMD64 Architecture Programmer's Manual, Volume 3: General-Purpose and
+///   System Instructions][amd64_ref].
+///
+/// [wiki_cpuid]: https://en.wikipedia.org/wiki/CPUID
+/// [intel64_ref]: http://www.intel.de/content/dam/www/public/us/en/documents/manuals/64-ia-32-architectures-software-developer-instruction-set-reference-manual-325383.pdf
+/// [amd64_ref]: http://support.amd.com/TechDocs/24594.pdf
+#[inline(always)]
+#[cfg_attr(test, assert_instr(cpuid))]
+pub fn cpuid(request: u32, ext: u32) -> CpuidResult {
+    unsafe {
+        let mut r = ::std::mem::uninitialized::<CpuidResult>();
+        asm!("cpuid"
+             : "={eax}"(r.eax), "={ebx}"(r.ebx), "={ecx}"(r.ecx), "={edx}"(r.edx)
+             : "{eax}"(request), "{ecx}"(ext)
+             : :);
+        r
+    }
+}
+
+/// Reads the contents of the extended control register `XCR`
+/// specified in `xcr_no`.
+#[inline(always)]
+// FIXME: see
+// https://github.com/rust-lang-nursery/stdsimd/issues/167
+// #[target_feature = "+xsave"]
+#[cfg_attr(test, assert_instr(xgetbv))]
+pub unsafe fn xgetbv(xcr_no: u32) -> u64 {
+    let eax: u32;
+    let edx: u32;
+
+    asm!("xgetbv"
+         : "={eax}"(eax),  "={edx}"(edx)
+         : "{ecx}"(xcr_no)
+         : :);
+
+    ((edx as u64) << 32) | (eax as u64)
+}