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use crate::settings::{self, LibcallCallConv};
use core::fmt;
use core::str;
use target_lexicon::{CallingConvention, Triple};
#[cfg(feature = "enable-serde")]
use serde_derive::{Deserialize, Serialize};
/// Calling convention identifiers.
#[derive(Debug, Copy, Clone, PartialEq, Eq, Hash)]
#[cfg_attr(feature = "enable-serde", derive(Serialize, Deserialize))]
pub enum CallConv {
/// Best performance, not ABI-stable.
Fast,
/// Smallest caller code size, not ABI-stable.
Cold,
/// Supports tail calls, not ABI-stable.
//
// Currently, this is basically sys-v except that callees pop stack
// arguments, rather than callers. Expected to change even more in the
// future, however!
Tail,
/// System V-style convention used on many platforms.
SystemV,
/// Windows "fastcall" convention, also used for x64 and ARM.
WindowsFastcall,
/// Mac aarch64 calling convention, which is a tweaked aarch64 ABI.
AppleAarch64,
/// Specialized convention for the probestack function.
Probestack,
/// Wasmtime equivalent of SystemV, not ABI-stable.
///
/// FIXME: remove this when Wasmtime uses the "tail" calling convention for
/// all wasm functions.
WasmtimeSystemV,
/// The winch calling convention, not ABI-stable.
///
/// The main difference to WasmtimeSystemV is that the winch calling
/// convention defines no callee-save registers, and restricts the number
/// of return registers to one integer, and one floating point.
Winch,
}
impl CallConv {
/// Return the default calling convention for the given target triple.
pub fn triple_default(triple: &Triple) -> Self {
match triple.default_calling_convention() {
// Default to System V for unknown targets because most everything
// uses System V.
Ok(CallingConvention::SystemV) | Err(()) => Self::SystemV,
Ok(CallingConvention::AppleAarch64) => Self::AppleAarch64,
Ok(CallingConvention::WindowsFastcall) => Self::WindowsFastcall,
Ok(unimp) => unimplemented!("calling convention: {:?}", unimp),
}
}
/// Returns the calling convention used for libcalls according to the current flags.
pub fn for_libcall(flags: &settings::Flags, default_call_conv: CallConv) -> Self {
match flags.libcall_call_conv() {
LibcallCallConv::IsaDefault => default_call_conv,
LibcallCallConv::Fast => Self::Fast,
LibcallCallConv::Cold => Self::Cold,
LibcallCallConv::SystemV => Self::SystemV,
LibcallCallConv::WindowsFastcall => Self::WindowsFastcall,
LibcallCallConv::AppleAarch64 => Self::AppleAarch64,
LibcallCallConv::Probestack => Self::Probestack,
}
}
/// Does this calling convention support tail calls?
pub fn supports_tail_calls(&self) -> bool {
match self {
CallConv::Tail => true,
_ => false,
}
}
/// Is the calling convention extending the Windows Fastcall ABI?
pub fn extends_windows_fastcall(self) -> bool {
match self {
Self::WindowsFastcall => true,
_ => false,
}
}
/// Is the calling convention extending the Apple aarch64 ABI?
pub fn extends_apple_aarch64(self) -> bool {
match self {
Self::AppleAarch64 => true,
_ => false,
}
}
}
impl fmt::Display for CallConv {
fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
f.write_str(match *self {
Self::Fast => "fast",
Self::Cold => "cold",
Self::Tail => "tail",
Self::SystemV => "system_v",
Self::WindowsFastcall => "windows_fastcall",
Self::AppleAarch64 => "apple_aarch64",
Self::Probestack => "probestack",
Self::WasmtimeSystemV => "wasmtime_system_v",
Self::Winch => "winch",
})
}
}
impl str::FromStr for CallConv {
type Err = ();
fn from_str(s: &str) -> Result<Self, Self::Err> {
match s {
"fast" => Ok(Self::Fast),
"cold" => Ok(Self::Cold),
"tail" => Ok(Self::Tail),
"system_v" => Ok(Self::SystemV),
"windows_fastcall" => Ok(Self::WindowsFastcall),
"apple_aarch64" => Ok(Self::AppleAarch64),
"probestack" => Ok(Self::Probestack),
"wasmtime_system_v" => Ok(Self::WasmtimeSystemV),
"winch" => Ok(Self::Winch),
_ => Err(()),
}
}
}