1 use crate::settings::{self, LibcallCallConv};
2 use core::fmt;
3 use core::str;
4 use target_lexicon::{CallingConvention, Triple};
5 
6 #[cfg(feature = "enable-serde")]
7 use serde_derive::{Deserialize, Serialize};
8 
9 /// Calling convention identifiers.
10 #[derive(Debug, Copy, Clone, PartialEq, Eq, Hash)]
11 #[cfg_attr(feature = "enable-serde", derive(Serialize, Deserialize))]
12 pub enum CallConv {
13     /// Best performance, not ABI-stable.
14     Fast,
15     /// Smallest caller code size, not ABI-stable.
16     Cold,
17     /// Supports tail calls, not ABI-stable.
18     //
19     // Currently, this is basically sys-v except that callees pop stack
20     // arguments, rather than callers. Expected to change even more in the
21     // future, however!
22     Tail,
23     /// System V-style convention used on many platforms.
24     SystemV,
25     /// Windows "fastcall" convention, also used for x64 and ARM.
26     WindowsFastcall,
27     /// Mac aarch64 calling convention, which is a tweaked aarch64 ABI.
28     AppleAarch64,
29     /// Specialized convention for the probestack function.
30     Probestack,
31     /// Wasmtime equivalent of SystemV, not ABI-stable.
32     ///
33     /// FIXME: remove this when Wasmtime uses the "tail" calling convention for
34     /// all wasm functions.
35     WasmtimeSystemV,
36     /// The winch calling convention, not ABI-stable.
37     ///
38     /// The main difference to WasmtimeSystemV is that the winch calling
39     /// convention defines no callee-save registers, and restricts the number
40     /// of return registers to one integer, and one floating point.
41     Winch,
42 }
43 
44 impl CallConv {
45     /// Return the default calling convention for the given target triple.
46     pub fn triple_default(triple: &Triple) -> Self {
47         match triple.default_calling_convention() {
48             // Default to System V for unknown targets because most everything
49             // uses System V.
50             Ok(CallingConvention::SystemV) | Err(()) => Self::SystemV,
51             Ok(CallingConvention::AppleAarch64) => Self::AppleAarch64,
52             Ok(CallingConvention::WindowsFastcall) => Self::WindowsFastcall,
53             Ok(unimp) => unimplemented!("calling convention: {:?}", unimp),
54         }
55     }
56 
57     /// Returns the calling convention used for libcalls according to the current flags.
58     pub fn for_libcall(flags: &settings::Flags, default_call_conv: CallConv) -> Self {
59         match flags.libcall_call_conv() {
60             LibcallCallConv::IsaDefault => default_call_conv,
61             LibcallCallConv::Fast => Self::Fast,
62             LibcallCallConv::Cold => Self::Cold,
63             LibcallCallConv::SystemV => Self::SystemV,
64             LibcallCallConv::WindowsFastcall => Self::WindowsFastcall,
65             LibcallCallConv::AppleAarch64 => Self::AppleAarch64,
66             LibcallCallConv::Probestack => Self::Probestack,
67         }
68     }
69 
70     /// Does this calling convention support tail calls?
71     pub fn supports_tail_calls(&self) -> bool {
72         match self {
73             CallConv::Tail => true,
74             _ => false,
75         }
76     }
77 
78     /// Is the calling convention extending the Windows Fastcall ABI?
79     pub fn extends_windows_fastcall(self) -> bool {
80         match self {
81             Self::WindowsFastcall => true,
82             _ => false,
83         }
84     }
85 
86     /// Is the calling convention extending the Apple aarch64 ABI?
87     pub fn extends_apple_aarch64(self) -> bool {
88         match self {
89             Self::AppleAarch64 => true,
90             _ => false,
91         }
92     }
93 }
94 
95 impl fmt::Display for CallConv {
96     fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
97         f.write_str(match *self {
98             Self::Fast => "fast",
99             Self::Cold => "cold",
100             Self::Tail => "tail",
101             Self::SystemV => "system_v",
102             Self::WindowsFastcall => "windows_fastcall",
103             Self::AppleAarch64 => "apple_aarch64",
104             Self::Probestack => "probestack",
105             Self::WasmtimeSystemV => "wasmtime_system_v",
106             Self::Winch => "winch",
107         })
108     }
109 }
110 
111 impl str::FromStr for CallConv {
112     type Err = ();
113     fn from_str(s: &str) -> Result<Self, Self::Err> {
114         match s {
115             "fast" => Ok(Self::Fast),
116             "cold" => Ok(Self::Cold),
117             "tail" => Ok(Self::Tail),
118             "system_v" => Ok(Self::SystemV),
119             "windows_fastcall" => Ok(Self::WindowsFastcall),
120             "apple_aarch64" => Ok(Self::AppleAarch64),
121             "probestack" => Ok(Self::Probestack),
122             "wasmtime_system_v" => Ok(Self::WasmtimeSystemV),
123             "winch" => Ok(Self::Winch),
124             _ => Err(()),
125         }
126     }
127 }
128