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Reimplement _xgetbv with LLVM intrinsics (#958)

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`_xgetbv` was reimplemented to use inline assembly in #333 since LLVM
3.9 didn't export the intrinsic we needed to use.  LLVM 4.0 has since
rectified that issue, and since rust's minimum supported version of LLVM
is 8.0, this change can be reverted.
This commit is contained in:
Andrew Sadler
2020-11-24 21:38:17 +01:00
committed by GitHub
parent ea5a0d01d3
commit f0ed8c497d
1 changed files with 3 additions and 4 deletions
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7
library/stdarch/crates/core_arch/src/x86/xsave.rs
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@@ -12,6 +12,8 @@ extern "C" {
fn xrstor(p: *const u8, hi: u32, lo: u32);
#[link_name = "llvm.x86.xsetbv"]
fn xsetbv(v: u32, hi: u32, lo: u32);
#[link_name = "llvm.x86.xgetbv"]
fn xgetbv(v: u32) -> i64;
#[link_name = "llvm.x86.xsaveopt"]
fn xsaveopt(p: *mut u8, hi: u32, lo: u32);
#[link_name = "llvm.x86.xsavec"]
@@ -85,10 +87,7 @@ pub unsafe fn _xsetbv(a: u32, val: u64) {
#[cfg_attr(test, assert_instr(xgetbv))]
#[stable(feature = "simd_x86", since = "1.27.0")]
pub unsafe fn _xgetbv(xcr_no: u32) -> u64 {
let eax: u32;
let edx: u32;
llvm_asm!("xgetbv" : "={eax}"(eax), "={edx}"(edx) : "{ecx}"(xcr_no));
((edx as u64) << 32) | (eax as u64)
xgetbv(xcr_no) as u64
}
/// Performs a full or partial save of the enabled processor states to memory at