wasmtime_internal_fiber/
stackswitch.rs

1//! ISA-specific stack-switching routines.
2
3// The bodies are defined in inline assembly in the conditionally
4// included modules below; their symbols are visible in the binary and
5// accessed via the `extern "C"` declarations below that.
6
7cfg_if::cfg_if! {
8    if #[cfg(target_arch = "aarch64")] {
9        mod aarch64;
10        pub(crate) use supported::*;
11        pub(crate) use aarch64::*;
12    } else if #[cfg(target_arch = "x86_64")] {
13        mod x86_64;
14        pub(crate) use supported::*;
15        pub(crate) use x86_64::*;
16    } else if #[cfg(target_arch = "x86")] {
17        mod x86;
18        pub(crate) use supported::*;
19        pub(crate) use x86::*;
20    } else if #[cfg(target_arch = "arm")] {
21        mod arm;
22        pub(crate) use supported::*;
23        pub(crate) use arm::*;
24    } else if #[cfg(target_arch = "s390x")] {
25        mod s390x;
26        pub(crate) use supported::*;
27        pub(crate) use s390x::*;
28    } else if #[cfg(target_arch = "riscv64")]  {
29        mod riscv64;
30        pub(crate) use supported::*;
31        pub(crate) use riscv64::*;
32    } else {
33        // No support for this platform. Don't fail compilation though and
34        // instead defer the error to happen at runtime when a fiber is created.
35        // Should help keep compiles working and narrows the failure to only
36        // situations that need fibers on unsupported platforms.
37        pub(crate) use unsupported::*;
38    }
39}
40
41/// A helper module to get reeported above in each case that we actually have
42/// stack-switching routines available in inline asm. The fall-through case
43/// though reexports the `unsupported` module instead.
44#[allow(
45    dead_code,
46    reason = "expected to have dead code in some configurations"
47)]
48mod supported {
49    pub const SUPPORTED_ARCH: bool = true;
50}
51
52/// Helper module reexported in the fallback case above when the current host
53/// architecture is not supported for stack switching. The `SUPPORTED_ARCH`
54/// boolean here is set to `false` which causes `Fiber::new` to return `false`.
55#[allow(
56    dead_code,
57    reason = "expected to have dead code in some configurations"
58)]
59mod unsupported {
60    pub const SUPPORTED_ARCH: bool = false;
61
62    pub(crate) unsafe fn wasmtime_fiber_init(
63        _top_of_stack: *mut u8,
64        _entry: extern "C" fn(*mut u8, *mut u8),
65        _entry_arg0: *mut u8,
66    ) {
67        unreachable!();
68    }
69
70    pub(crate) unsafe fn wasmtime_fiber_switch(_top_of_stack: *mut u8) {
71        unreachable!();
72    }
73}
wasmtime_internal_fiber/stackswitch.rs

wasmtime_internal_fiber/
stackswitch.rs
