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     /// The winch calling convention, not ABI-stable.
32     ///
33     /// The main difference to SystemV is that the winch calling convention
34     /// defines no callee-save registers, and restricts the number of return
35     /// registers to one integer, and one floating point.
36     Winch,
37 }
38 
39 impl CallConv {
40     /// Return the default calling convention for the given target triple.
41     pub fn triple_default(triple: &Triple) -> Self {
42         match triple.default_calling_convention() {
43             // Default to System V for unknown targets because most everything
44             // uses System V.
45             Ok(CallingConvention::SystemV) | Err(()) => Self::SystemV,
46             Ok(CallingConvention::AppleAarch64) => Self::AppleAarch64,
47             Ok(CallingConvention::WindowsFastcall) => Self::WindowsFastcall,
48             Ok(unimp) => unimplemented!("calling convention: {:?}", unimp),
49         }
50     }
51 
52     /// Returns the calling convention used for libcalls according to the current flags.
53     pub fn for_libcall(flags: &settings::Flags, default_call_conv: CallConv) -> Self {
54         match flags.libcall_call_conv() {
55             LibcallCallConv::IsaDefault => default_call_conv,
56             LibcallCallConv::Fast => Self::Fast,
57             LibcallCallConv::Cold => Self::Cold,
58             LibcallCallConv::SystemV => Self::SystemV,
59             LibcallCallConv::WindowsFastcall => Self::WindowsFastcall,
60             LibcallCallConv::AppleAarch64 => Self::AppleAarch64,
61             LibcallCallConv::Probestack => Self::Probestack,
62         }
63     }
64 
65     /// Does this calling convention support tail calls?
66     pub fn supports_tail_calls(&self) -> bool {
67         match self {
68             CallConv::Tail => true,
69             _ => false,
70         }
71     }
72 }
73 
74 impl fmt::Display for CallConv {
75     fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
76         f.write_str(match *self {
77             Self::Fast => "fast",
78             Self::Cold => "cold",
79             Self::Tail => "tail",
80             Self::SystemV => "system_v",
81             Self::WindowsFastcall => "windows_fastcall",
82             Self::AppleAarch64 => "apple_aarch64",
83             Self::Probestack => "probestack",
84             Self::Winch => "winch",
85         })
86     }
87 }
88 
89 impl str::FromStr for CallConv {
90     type Err = ();
91     fn from_str(s: &str) -> Result<Self, Self::Err> {
92         match s {
93             "fast" => Ok(Self::Fast),
94             "cold" => Ok(Self::Cold),
95             "tail" => Ok(Self::Tail),
96             "system_v" => Ok(Self::SystemV),
97             "windows_fastcall" => Ok(Self::WindowsFastcall),
98             "apple_aarch64" => Ok(Self::AppleAarch64),
99             "probestack" => Ok(Self::Probestack),
100             "winch" => Ok(Self::Winch),
101             _ => Err(()),
102         }
103     }
104 }
105