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#![allow(unused_imports)]
use core::intrinsics;
// NOTE These functions are implemented using assembly because they using a custom
// calling convention which can't be implemented using a normal Rust function
// NOTE These functions are never mangled as they are not tested against compiler-rt
// and mangling ___chkstk would break the `jmp ___chkstk` instruction in __alloca
intrinsics! {
#[naked]
#[cfg(all(
windows,
target_env = "gnu",
not(feature = "no-asm")
))]
pub unsafe extern "C" fn ___chkstk_ms() {
core::arch::asm!(
"push %rcx",
"push %rax",
"cmp $0x1000,%rax",
"lea 24(%rsp),%rcx",
"jb 1f",
"2:",
"sub $0x1000,%rcx",
"test %rcx,(%rcx)",
"sub $0x1000,%rax",
"cmp $0x1000,%rax",
"ja 2b",
"1:",
"sub %rax,%rcx",
"test %rcx,(%rcx)",
"pop %rax",
"pop %rcx",
"ret",
options(noreturn, att_syntax)
);
}
#[naked]
#[cfg(all(
windows,
target_env = "gnu",
not(feature = "no-asm")
))]
pub unsafe extern "C" fn __alloca() {
core::arch::asm!(
"mov %rcx,%rax", // x64 _alloca is a normal function with parameter in rcx
"jmp ___chkstk", // Jump to ___chkstk since fallthrough may be unreliable"
options(noreturn, att_syntax)
);
}
#[naked]
#[cfg(all(
windows,
target_env = "gnu",
not(feature = "no-asm")
))]
pub unsafe extern "C" fn ___chkstk() {
core::arch::asm!(
"push %rcx",
"cmp $0x1000,%rax",
"lea 16(%rsp),%rcx", // rsp before calling this routine -> rcx
"jb 1f",
"2:",
"sub $0x1000,%rcx",
"test %rcx,(%rcx)",
"sub $0x1000,%rax",
"cmp $0x1000,%rax",
"ja 2b",
"1:",
"sub %rax,%rcx",
"test %rcx,(%rcx)",
"lea 8(%rsp),%rax", // load pointer to the return address into rax
"mov %rcx,%rsp", // install the new top of stack pointer into rsp
"mov -8(%rax),%rcx", // restore rcx
"push (%rax)", // push return address onto the stack
"sub %rsp,%rax", // restore the original value in rax
"ret",
options(noreturn, att_syntax)
);
}
}
// HACK(https://github.com/rust-lang/rust/issues/62785): x86_64-unknown-uefi needs special LLVM
// support unless we emit the _fltused
mod _fltused {
#[no_mangle]
#[used]
#[cfg(target_os = "uefi")]
static _fltused: i32 = 0;
}
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