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rustc_target: add "unwind" payloads to Abi

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### Overview

    This commit begins the implementation work for RFC 2945. For more
    information, see the rendered RFC [1] and tracking issue [2].

    A boolean `unwind` payload is added to the `C`, `System`, `Stdcall`,
    and `Thiscall` variants, marking whether unwinding across FFI
    boundaries is acceptable. The cases where each of these variants'
    `unwind` member is true correspond with the `C-unwind`,
    `system-unwind`, `stdcall-unwind`, and `thiscall-unwind` ABI strings
    introduced in RFC 2945 [3].

 ### Feature Gate and Unstable Book

    This commit adds a `c_unwind` feature gate for the new ABI strings.
    Tests for this feature gate are included in `src/test/ui/c-unwind/`,
    which ensure that this feature gate works correctly for each of the
    new ABIs.

    A new language features entry in the unstable book is added as well.

 ### Further Work To Be Done

    This commit does not proceed to implement the new unwinding ABIs,
    and is intentionally scoped specifically to *defining* the ABIs and
    their feature flag.

 ### One Note on Test Churn

    This will lead to some test churn, in re-blessing hash tests, as the
    deleted comment in `src/librustc_target/spec/abi.rs` mentioned,
    because we can no longer guarantee the ordering of the `Abi`
    variants.

    While this is a downside, this decision was made bearing in mind
    that RFC 2945 states the following, in the "Other `unwind` Strings"
    section [3]:

    >  More unwind variants of existing ABI strings may be introduced,
    >  with the same semantics, without an additional RFC.

    Adding a new variant for each of these cases, rather than specifying
    a payload for a given ABI, would quickly become untenable, and make
    working with the `Abi` enum prone to mistakes.

    This approach encodes the unwinding information *into* a given ABI,
    to account for the future possibility of other `-unwind` ABI
    strings.

 ### Ignore Directives

    `ignore-*` directives are used in two of our `*-unwind` ABI test
    cases.

    Specifically, the `stdcall-unwind` and `thiscall-unwind` test cases
    ignore architectures that do not support `stdcall` and
    `thiscall`, respectively.

    These directives are cribbed from
    `src/test/ui/c-variadic/variadic-ffi-1.rs` for `stdcall`, and
    `src/test/ui/extern/extern-thiscall.rs` for `thiscall`.

    This would otherwise fail on some targets, see:
    fcf697f902

 ### Footnotes

[1]: https://github.com/rust-lang/rfcs/blob/master/text/2945-c-unwind-abi.md
[2]: https://github.com/rust-lang/rust/issues/74990
[3]: https://github.com/rust-lang/rfcs/blob/master/text/2945-c-unwind-abi.md#other-unwind-abi-strings
This commit is contained in:
katelyn a. martin 2020-08-27 11:49:18 -04:00
parent 3a5d45f68c
commit df45c579de
29 changed files with 277 additions and 52 deletions
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65
compiler/rustc_target/src/spec/abi.rs
View file

@ -8,24 +8,21 @@ mod tests;
#[derive(PartialEq, Eq, PartialOrd, Ord, Hash, Clone, Copy, Debug)]
#[derive(HashStable_Generic, Encodable, Decodable)]
pub enum Abi {
// N.B., this ordering MUST match the AbiDatas array below.
// (This is ensured by the test indices_are_correct().)
// Multiplatform / generic ABIs
//
// These ABIs come first because every time we add a new ABI, we
// have to re-bless all the hashing tests. These are used in many
// places, so giving them stable values reduces test churn. The
// specific values are meaningless.
Rust = 0,
C = 1,
Rust,
C { unwind: bool },
// Single platform ABIs
Cdecl,
Stdcall,
Stdcall { unwind: bool },
Fastcall,
Vectorcall,
Thiscall,
Thiscall { unwind: bool },
Aapcs,
Win64,
SysV64,
@ -39,7 +36,7 @@ pub enum Abi {
CCmseNonSecureCall,
// Multiplatform / generic ABIs
System,
System { unwind: bool },
RustIntrinsic,
RustCall,
PlatformIntrinsic,
@ -61,13 +58,16 @@ pub struct AbiData {
const AbiDatas: &[AbiData] = &[
// Cross-platform ABIs
AbiData { abi: Abi::Rust, name: "Rust", generic: true },
AbiData { abi: Abi::C, name: "C", generic: true },
AbiData { abi: Abi::C { unwind: false }, name: "C", generic: true },
AbiData { abi: Abi::C { unwind: true }, name: "C-unwind", generic: true },
// Platform-specific ABIs
AbiData { abi: Abi::Cdecl, name: "cdecl", generic: false },
AbiData { abi: Abi::Stdcall, name: "stdcall", generic: false },
AbiData { abi: Abi::Stdcall { unwind: false }, name: "stdcall", generic: false },
AbiData { abi: Abi::Stdcall { unwind: true }, name: "stdcall-unwind", generic: false },
AbiData { abi: Abi::Fastcall, name: "fastcall", generic: false },
AbiData { abi: Abi::Vectorcall, name: "vectorcall", generic: false },
AbiData { abi: Abi::Thiscall, name: "thiscall", generic: false },
AbiData { abi: Abi::Thiscall { unwind: false }, name: "thiscall", generic: false },
AbiData { abi: Abi::Thiscall { unwind: true }, name: "thiscall-unwind", generic: false },
AbiData { abi: Abi::Aapcs, name: "aapcs", generic: false },
AbiData { abi: Abi::Win64, name: "win64", generic: false },
AbiData { abi: Abi::SysV64, name: "sysv64", generic: false },
@ -84,7 +84,8 @@ const AbiDatas: &[AbiData] = &[
},
AbiData { abi: Abi::CCmseNonSecureCall, name: "C-cmse-nonsecure-call", generic: false },
// Cross-platform ABIs
AbiData { abi: Abi::System, name: "system", generic: true },
AbiData { abi: Abi::System { unwind: false }, name: "system", generic: true },
AbiData { abi: Abi::System { unwind: true }, name: "system-unwind", generic: true },
AbiData { abi: Abi::RustIntrinsic, name: "rust-intrinsic", generic: true },
AbiData { abi: Abi::RustCall, name: "rust-call", generic: true },
AbiData { abi: Abi::PlatformIntrinsic, name: "platform-intrinsic", generic: true },
@ -103,7 +104,41 @@ pub fn all_names() -> Vec<&'static str> {
impl Abi {
#[inline]
pub fn index(self) -> usize {
self as usize
// N.B., this ordering MUST match the AbiDatas array above.
// (This is ensured by the test indices_are_correct().)
use Abi::*;
match self {
// Cross-platform ABIs
Rust => 0,
C { unwind: false } => 1,
C { unwind: true } => 2,
// Platform-specific ABIs
Cdecl => 3,
Stdcall { unwind: false } => 4,
Stdcall { unwind: true } => 5,
Fastcall => 6,
Vectorcall => 7,
Thiscall { unwind: false } => 8,
Thiscall { unwind: true } => 9,
Aapcs => 10,
Win64 => 11,
SysV64 => 12,
PtxKernel => 13,
Msp430Interrupt => 14,
X86Interrupt => 15,
AmdGpuKernel => 16,
EfiApi => 17,
AvrInterrupt => 18,
AvrNonBlockingInterrupt => 19,
CCmseNonSecureCall => 20,
// Cross-platform ABIs
System { unwind: false } => 21,
System { unwind: true } => 22,
RustIntrinsic => 23,
RustCall => 24,
PlatformIntrinsic => 25,
Unadjusted => 26,
}
}
#[inline]
@ -122,6 +157,8 @@ impl Abi {
impl fmt::Display for Abi {
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
write!(f, "\"{}\"", self.name())
match self {
abi => write!(f, "\"{}\"", abi.name()),
}
}
}

11
compiler/rustc_target/src/spec/arm_base.rs
View file

@ -2,5 +2,14 @@ use crate::spec::abi::Abi;
// All the calling conventions trigger an assertion(Unsupported calling convention) in llvm on arm
pub fn unsupported_abis() -> Vec<Abi> {
vec![Abi::Stdcall, Abi::Fastcall, Abi::Vectorcall, Abi::Thiscall, Abi::Win64, Abi::SysV64]
vec![
Abi::Stdcall { unwind: false },
Abi::Stdcall { unwind: true },
Abi::Fastcall,
Abi::Vectorcall,
Abi::Thiscall { unwind: false },
Abi::Thiscall { unwind: true },
Abi::Win64,
Abi::SysV64,
]
}

6
compiler/rustc_target/src/spec/mipsel_unknown_none.rs
View file

@ -23,10 +23,12 @@ pub fn target() -> Target {
panic_strategy: PanicStrategy::Abort,
relocation_model: RelocModel::Static,
unsupported_abis: vec![
Abi::Stdcall,
Abi::Stdcall { unwind: false },
Abi::Stdcall { unwind: true },
Abi::Fastcall,
Abi::Vectorcall,
Abi::Thiscall,
Abi::Thiscall { unwind: false },
Abi::Thiscall { unwind: true },
Abi::Win64,
Abi::SysV64,
],

19
compiler/rustc_target/src/spec/mod.rs
View file

@ -1283,24 +1283,31 @@ impl Target {
/// Given a function ABI, turn it into the correct ABI for this target.
pub fn adjust_abi(&self, abi: Abi) -> Abi {
match abi {
Abi::System => {
Abi::System { unwind } => {
if self.is_like_windows && self.arch == "x86" {
Abi::Stdcall
Abi::Stdcall { unwind }
} else {
Abi::C
Abi::C { unwind }
}
}
// These ABI kinds are ignored on non-x86 Windows targets.
// See https://docs.microsoft.com/en-us/cpp/cpp/argument-passing-and-naming-conventions
// and the individual pages for __stdcall et al.
Abi::Stdcall | Abi::Fastcall | Abi::Vectorcall | Abi::Thiscall => {
if self.is_like_windows && self.arch != "x86" { Abi::C } else { abi }
Abi::Stdcall { unwind } | Abi::Thiscall { unwind } => {
if self.is_like_windows && self.arch != "x86" { Abi::C { unwind } } else { abi }
}
Abi::Fastcall | Abi::Vectorcall => {
if self.is_like_windows && self.arch != "x86" {
Abi::C { unwind: false }
} else {
abi
}
}
Abi::EfiApi => {
if self.arch == "x86_64" {
Abi::Win64
} else {
Abi::C
Abi::C { unwind: false }
}
}
abi => abi,

6
compiler/rustc_target/src/spec/nvptx64_nvidia_cuda.rs
View file

@ -49,10 +49,12 @@ pub fn target() -> Target {
// create the tests for this.
unsupported_abis: vec![
Abi::Cdecl,
Abi::Stdcall,
Abi::Stdcall { unwind: false },
Abi::Stdcall { unwind: true },
Abi::Fastcall,
Abi::Vectorcall,
Abi::Thiscall,
Abi::Thiscall { unwind: false },
Abi::Thiscall { unwind: true },
Abi::Aapcs,
Abi::Win64,
Abi::SysV64,

6
compiler/rustc_target/src/spec/riscv_base.rs
View file

@ -5,10 +5,12 @@ use crate::spec::abi::Abi;
pub fn unsupported_abis() -> Vec<Abi> {
vec![
Abi::Cdecl,
Abi::Stdcall,
Abi::Stdcall { unwind: false },
Abi::Stdcall { unwind: true },
Abi::Fastcall,
Abi::Vectorcall,
Abi::Thiscall,
Abi::Thiscall { unwind: false },
Abi::Thiscall { unwind: true },
Abi::Aapcs,
Abi::Win64,
Abi::SysV64,