core/stdarch/crates/core_arch/src/x86/cpuid.rs
1//! `cpuid` intrinsics
2#![allow(clippy::module_name_repetitions)]
3
4use crate::arch::asm;
5#[cfg(test)]
6use stdarch_test::assert_instr;
7
8/// Result of the `cpuid` instruction.
9#[allow(clippy::missing_inline_in_public_items)]
10// ^^ the derived impl of Debug for CpuidResult is not #[inline] and that's OK.
11#[derive(Copy, Clone, Debug, Eq, Ord, PartialEq, PartialOrd)]
12#[stable(feature = "simd_x86", since = "1.27.0")]
13pub struct CpuidResult {
14 /// EAX register.
15 #[stable(feature = "simd_x86", since = "1.27.0")]
16 pub eax: u32,
17 /// EBX register.
18 #[stable(feature = "simd_x86", since = "1.27.0")]
19 pub ebx: u32,
20 /// ECX register.
21 #[stable(feature = "simd_x86", since = "1.27.0")]
22 pub ecx: u32,
23 /// EDX register.
24 #[stable(feature = "simd_x86", since = "1.27.0")]
25 pub edx: u32,
26}
27
28/// Returns the result of the `cpuid` instruction for a given `leaf` (`EAX`)
29/// and `sub_leaf` (`ECX`).
30///
31/// The highest-supported leaf value is returned by the first tuple argument of
32/// [`__get_cpuid_max(0)`](fn.__get_cpuid_max.html). For leaves containing
33/// sub-leaves, the second tuple argument returns the highest-supported
34/// sub-leaf value.
35///
36/// The [CPUID Wikipedia page][wiki_cpuid] contains how to query which
37/// information using the `EAX` and `ECX` registers, and the interpretation of
38/// the results returned in `EAX`, `EBX`, `ECX`, and `EDX`.
39///
40/// The references are:
41/// - [Intel 64 and IA-32 Architectures Software Developer's Manual Volume 2:
42/// Instruction Set Reference, A-Z][intel64_ref].
43/// - [AMD64 Architecture Programmer's Manual, Volume 3: General-Purpose and
44/// System Instructions][amd64_ref].
45///
46/// [wiki_cpuid]: https://en.wikipedia.org/wiki/CPUID
47/// [intel64_ref]: https://cdrdv2-public.intel.com/671110/325383-sdm-vol-2abcd.pdf
48/// [amd64_ref]: http://support.amd.com/TechDocs/24594.pdf
49#[inline]
50#[cfg_attr(test, assert_instr(cpuid))]
51#[stable(feature = "simd_x86", since = "1.27.0")]
52pub unsafe fn __cpuid_count(leaf: u32, sub_leaf: u32) -> CpuidResult {
53 let eax;
54 let ebx;
55 let ecx;
56 let edx;
57
58 // LLVM sometimes reserves `ebx` for its internal use, we so we need to use
59 // a scratch register for it instead.
60 #[cfg(target_arch = "x86")]
61 {
62 asm!(
63 "mov {0}, ebx",
64 "cpuid",
65 "xchg {0}, ebx",
66 out(reg) ebx,
67 inout("eax") leaf => eax,
68 inout("ecx") sub_leaf => ecx,
69 out("edx") edx,
70 options(nostack, preserves_flags),
71 );
72 }
73 #[cfg(target_arch = "x86_64")]
74 {
75 asm!(
76 "mov {0:r}, rbx",
77 "cpuid",
78 "xchg {0:r}, rbx",
79 out(reg) ebx,
80 inout("eax") leaf => eax,
81 inout("ecx") sub_leaf => ecx,
82 out("edx") edx,
83 options(nostack, preserves_flags),
84 );
85 }
86 CpuidResult { eax, ebx, ecx, edx }
87}
88
89/// See [`__cpuid_count`](fn.__cpuid_count.html).
90#[inline]
91#[cfg_attr(test, assert_instr(cpuid))]
92#[stable(feature = "simd_x86", since = "1.27.0")]
93pub unsafe fn __cpuid(leaf: u32) -> CpuidResult {
94 __cpuid_count(leaf, 0)
95}
96
97/// Returns the highest-supported `leaf` (`EAX`) and sub-leaf (`ECX`) `cpuid`
98/// values.
99///
100/// If `cpuid` is supported, and `leaf` is zero, then the first tuple argument
101/// contains the highest `leaf` value that `cpuid` supports. For `leaf`s
102/// containing sub-leafs, the second tuple argument contains the
103/// highest-supported sub-leaf value.
104///
105/// See also [`__cpuid`](fn.__cpuid.html) and
106/// [`__cpuid_count`](fn.__cpuid_count.html).
107#[inline]
108#[stable(feature = "simd_x86", since = "1.27.0")]
109pub unsafe fn __get_cpuid_max(leaf: u32) -> (u32, u32) {
110 let CpuidResult { eax, ebx, .. } = __cpuid(leaf);
111 (eax, ebx)
112}