Remove has_cpuid

Author: workingjubilee

crates/core_arch/src/x86/cpuid.rs

@@ -96,73 +96,6 @@ pub unsafe fn __cpuid(leaf: u32) -> CpuidResult {
     __cpuid_count(leaf, 0)
 }
 
-/// Does the host support the `cpuid` instruction?
-#[inline]
-#[unstable(feature = "stdarch_x86_has_cpuid", issue = "60123")]
-pub fn has_cpuid() -> bool {
-    #[cfg(target_env = "sgx")]
-    {
-        false
-    }
-    #[cfg(all(not(target_env = "sgx"), target_arch = "x86_64"))]
-    {
-        true
-    }
-    #[cfg(all(not(target_env = "sgx"), target_arch = "x86"))]
-    {
-        // Optimization for i586 and i686 Rust targets which SSE enabled
-        // and support cpuid:
-        #[cfg(target_feature = "sse")]
-        {
-            true
-        }
-
-        // If SSE is not enabled, detect whether cpuid is available:
-        #[cfg(not(target_feature = "sse"))]
-        unsafe {
-            // On `x86` the `cpuid` instruction is not always available.
-            // This follows the approach indicated in:
-            // http://wiki.osdev.org/CPUID#Checking_CPUID_availability
-            // https://software.intel.com/en-us/articles/using-cpuid-to-detect-the-presence-of-sse-41-and-sse-42-instruction-sets/
-            // which detects whether `cpuid` is available by checking whether
-            // the 21st bit of the EFLAGS register is modifiable or not.
-            // If it is, then `cpuid` is available.
-            let result: u32;
-            asm!(
-                // Read eflags and save a copy of it
-                "pushfd",
-                "pop {result}",
-                "mov {result}, {saved_flags}",
-                // Flip 21st bit of the flags
-                "xor $0x200000, {result}",
-                // Load the modified flags and read them back.
-                // Bit 21 can only be modified if cpuid is available.
-                "push {result}",
-                "popfd",
-                "pushfd",
-                "pop {result}",
-                // Use xor to find out whether bit 21 has changed
-                "xor {saved_flags}, {result}",
-                result = out(reg) result,
-                saved_flags = out(reg) _,
-                options(nomem, att_syntax),
-            );
-            // There is a race between popfd (A) and pushfd (B)
-            // where other bits beyond 21st may have been modified due to
-            // interrupts, a debugger stepping through the asm, etc.
-            //
-            // Therefore, explicitly check whether the 21st bit
-            // was modified or not.
-            //
-            // If the result is zero, the cpuid bit was not modified.
-            // If the result is `0x200000` (non-zero), then the cpuid
-            // was correctly modified and the CPU supports the cpuid
-            // instruction:
-            (result & 0x200000) != 0
-        }
-    }
-}
-
 /// Returns the highest-supported `leaf` (`EAX`) and sub-leaf (`ECX`) `cpuid`
 /// values.
 ///
@@ -179,22 +112,3 @@ pub unsafe fn __get_cpuid_max(leaf: u32) -> (u32, u32) {
     let CpuidResult { eax, ebx, .. } = __cpuid(leaf);
     (eax, ebx)
 }
-
-#[cfg(test)]
-mod tests {
-    use crate::core_arch::x86::*;
-
-    #[test]
-    #[cfg_attr(miri, ignore)] // Uses inline assembly
-    fn test_always_has_cpuid() {
-        // all currently-tested targets have the instruction
-        // FIXME: add targets without `cpuid` to CI
-        assert!(cpuid::has_cpuid());
-    }
-
-    #[test]
-    #[cfg_attr(miri, ignore)] // Uses inline assembly
-    fn test_has_cpuid_idempotent() {
-        assert_eq!(cpuid::has_cpuid(), cpuid::has_cpuid());
-    }
-}

crates/std_detect/src/detect/os/x86.rs

@@ -28,9 +28,8 @@ use crate::detect::{bit, cache, Feature};
 pub(crate) fn detect_features() -> cache::Initializer {
     let mut value = cache::Initializer::default();
 
-    // If the x86 CPU does not support the CPUID instruction then it is too
-    // old to support any of the currently-detectable features.
-    if !has_cpuid() {
+    if cfg!(target_env = "sgx") {
+        // doesn't support this because it is untrusted data
         return value;
     }
 

crates/std_detect/src/lib.rs

@@ -20,10 +20,6 @@
 #![cfg_attr(test, allow(unused_imports))]
 #![no_std]
 #![allow(internal_features)]
-#![cfg_attr(
-    any(target_arch = "x86", target_arch = "x86_64"),
-    feature(stdarch_x86_has_cpuid)
-)]
 
 #[cfg(test)]
 #[macro_use]