core/stdarch/crates/core_arch/src/x86/
fxsr.rs

1//! FXSR floating-point context fast save and restore.
2
3#[cfg(test)]
4use stdarch_test::assert_instr;
5
6#[allow(improper_ctypes)]
7unsafe extern "C" {
8    #[link_name = "llvm.x86.fxsave"]
9    fn fxsave(p: *mut u8);
10    #[link_name = "llvm.x86.fxrstor"]
11    fn fxrstor(p: *const u8);
12}
13
14/// Saves the `x87` FPU, `MMX` technology, `XMM`, and `MXCSR` registers to the
15/// 512-byte-long 16-byte-aligned memory region `mem_addr`.
16///
17/// A misaligned destination operand raises a general-protection (#GP) or an
18/// alignment check exception (#AC).
19///
20/// See [`FXSAVE`][fxsave] and [`FXRSTOR`][fxrstor].
21///
22/// [fxsave]: http://www.felixcloutier.com/x86/FXSAVE.html
23/// [fxrstor]: http://www.felixcloutier.com/x86/FXRSTOR.html
24///
25/// [Intel's documentation](https://www.intel.com/content/www/us/en/docs/intrinsics-guide/index.html#text=_fxsave)
26#[inline]
27#[target_feature(enable = "fxsr")]
28#[cfg_attr(test, assert_instr(fxsave))]
29#[stable(feature = "simd_x86", since = "1.27.0")]
30pub unsafe fn _fxsave(mem_addr: *mut u8) {
31    fxsave(mem_addr)
32}
33
34/// Restores the `XMM`, `MMX`, `MXCSR`, and `x87` FPU registers from the
35/// 512-byte-long 16-byte-aligned memory region `mem_addr`.
36///
37/// The contents of this memory region should have been written to by a
38/// previous
39/// `_fxsave` or `_fxsave64` intrinsic.
40///
41/// A misaligned destination operand raises a general-protection (#GP) or an
42/// alignment check exception (#AC).
43///
44/// See [`FXSAVE`][fxsave] and [`FXRSTOR`][fxrstor].
45///
46/// [fxsave]: http://www.felixcloutier.com/x86/FXSAVE.html
47/// [fxrstor]: http://www.felixcloutier.com/x86/FXRSTOR.html
48///
49/// [Intel's documentation](https://www.intel.com/content/www/us/en/docs/intrinsics-guide/index.html#text=_fxrstor)
50#[inline]
51#[target_feature(enable = "fxsr")]
52#[cfg_attr(test, assert_instr(fxrstor))]
53#[stable(feature = "simd_x86", since = "1.27.0")]
54pub unsafe fn _fxrstor(mem_addr: *const u8) {
55    fxrstor(mem_addr)
56}
57
58#[cfg(test)]
59mod tests {
60    use crate::core_arch::x86::*;
61    use std::{cmp::PartialEq, fmt};
62    use stdarch_test::simd_test;
63
64    #[repr(align(16))]
65    struct FxsaveArea {
66        data: [u8; 512], // 512 bytes
67    }
68
69    impl FxsaveArea {
70        fn new() -> FxsaveArea {
71            FxsaveArea { data: [0; 512] }
72        }
73        fn ptr(&mut self) -> *mut u8 {
74            self.data.as_mut_ptr()
75        }
76    }
77
78    #[simd_test(enable = "fxsr")]
79    #[cfg_attr(miri, ignore)] // Register saving/restoring is not supported in Miri
80    unsafe fn test_fxsave() {
81        let mut a = FxsaveArea::new();
82        let mut b = FxsaveArea::new();
83
84        fxsr::_fxsave(a.ptr());
85        fxsr::_fxrstor(a.ptr());
86        fxsr::_fxsave(b.ptr());
87    }
88}
core/stdarch/crates/core_arch/src/x86/fxsr.rs

core/stdarch/crates/core_arch/src/x86/
fxsr.rs
