cranelift_codegen/isa/
call_conv.rs

1use crate::ir::Type;
2use crate::ir::types;
3use crate::settings::{self, LibcallCallConv};
4use core::fmt;
5use core::str;
6use target_lexicon::{CallingConvention, Triple};
7
8#[cfg(feature = "enable-serde")]
9use serde_derive::{Deserialize, Serialize};
10
11/// Calling convention identifiers.
12#[derive(Debug, Copy, Clone, PartialEq, Eq, Hash)]
13#[cfg_attr(feature = "enable-serde", derive(Serialize, Deserialize))]
14pub enum CallConv {
15    /// Best performance, not ABI-stable.
16    Fast,
17    /// Smallest caller code size, not ABI-stable.
18    Cold,
19    /// Supports tail calls, not ABI-stable except for exception
20    /// payload registers.
21    ///
22    /// On exception resume, a caller to a `tail`-convention function
23    /// assumes that the exception payload values are in the following
24    /// registers (per platform):
25    /// - x86-64: rax, rdx
26    /// - aarch64: x0, x1
27    /// - riscv64: a0, a1
28    /// - pulley{32,64}: x0, x1
29    //
30    // Currently, this is basically sys-v except that callees pop stack
31    // arguments, rather than callers. Expected to change even more in the
32    // future, however!
33    Tail,
34    /// System V-style convention used on many platforms.
35    SystemV,
36    /// Windows "fastcall" convention, also used for x64 and ARM.
37    WindowsFastcall,
38    /// Mac aarch64 calling convention, which is a tweaked aarch64 ABI.
39    AppleAarch64,
40    /// Specialized convention for the probestack function.
41    Probestack,
42    /// The winch calling convention, not ABI-stable.
43    ///
44    /// The main difference to SystemV is that the winch calling convention
45    /// defines no callee-save registers, and restricts the number of return
46    /// registers to one integer, and one floating point.
47    Winch,
48}
49
50impl CallConv {
51    /// Return the default calling convention for the given target triple.
52    pub fn triple_default(triple: &Triple) -> Self {
53        match triple.default_calling_convention() {
54            // Default to System V for unknown targets because most everything
55            // uses System V.
56            Ok(CallingConvention::SystemV) | Err(()) => Self::SystemV,
57            Ok(CallingConvention::AppleAarch64) => Self::AppleAarch64,
58            Ok(CallingConvention::WindowsFastcall) => Self::WindowsFastcall,
59            Ok(unimp) => unimplemented!("calling convention: {:?}", unimp),
60        }
61    }
62
63    /// Returns the calling convention used for libcalls according to the current flags.
64    pub fn for_libcall(flags: &settings::Flags, default_call_conv: CallConv) -> Self {
65        match flags.libcall_call_conv() {
66            LibcallCallConv::IsaDefault => default_call_conv,
67            LibcallCallConv::Fast => Self::Fast,
68            LibcallCallConv::Cold => Self::Cold,
69            LibcallCallConv::SystemV => Self::SystemV,
70            LibcallCallConv::WindowsFastcall => Self::WindowsFastcall,
71            LibcallCallConv::AppleAarch64 => Self::AppleAarch64,
72            LibcallCallConv::Probestack => Self::Probestack,
73        }
74    }
75
76    /// Does this calling convention support tail calls?
77    pub fn supports_tail_calls(&self) -> bool {
78        match self {
79            CallConv::Tail => true,
80            _ => false,
81        }
82    }
83
84    /// Does this calling convention support exceptions?
85    pub fn supports_exceptions(&self) -> bool {
86        match self {
87            CallConv::Tail | CallConv::SystemV | CallConv::Winch => true,
88            _ => false,
89        }
90    }
91
92    /// What types do the exception payload value(s) have?
93    ///
94    /// Note that this function applies to the *callee* of a `try_call`
95    /// instruction. The calling convention of the callee may differ from the
96    /// caller, but the exceptional payload types available are defined by the
97    /// callee calling convention.
98    ///
99    /// Also note that individual backends are responsible for reporting
100    /// register destinations for exceptional types. Internally Cranelift
101    /// asserts that the backend supports the exact same number of register
102    /// destinations as this return value.
103    pub fn exception_payload_types(&self, pointer_ty: Type) -> &[Type] {
104        match self {
105            CallConv::Tail | CallConv::SystemV => match pointer_ty {
106                types::I32 => &[types::I32, types::I32],
107                types::I64 => &[types::I64, types::I64],
108                _ => unreachable!(),
109            },
110            _ => &[],
111        }
112    }
113}
114
115impl fmt::Display for CallConv {
116    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
117        f.write_str(match *self {
118            Self::Fast => "fast",
119            Self::Cold => "cold",
120            Self::Tail => "tail",
121            Self::SystemV => "system_v",
122            Self::WindowsFastcall => "windows_fastcall",
123            Self::AppleAarch64 => "apple_aarch64",
124            Self::Probestack => "probestack",
125            Self::Winch => "winch",
126        })
127    }
128}
129
130impl str::FromStr for CallConv {
131    type Err = ();
132    fn from_str(s: &str) -> Result<Self, Self::Err> {
133        match s {
134            "fast" => Ok(Self::Fast),
135            "cold" => Ok(Self::Cold),
136            "tail" => Ok(Self::Tail),
137            "system_v" => Ok(Self::SystemV),
138            "windows_fastcall" => Ok(Self::WindowsFastcall),
139            "apple_aarch64" => Ok(Self::AppleAarch64),
140            "probestack" => Ok(Self::Probestack),
141            "winch" => Ok(Self::Winch),
142            _ => Err(()),
143        }
144    }
145}
cranelift_codegen/isa/call_conv.rs

cranelift_codegen/isa/
call_conv.rs
