Skip to content

Commit f755f4c

Browse files
RalfJungRalfJung
committed
add rustc_abi to control ABI decisions LLVM does not have flags for, and use it for x86 softfloat
1 parent ccc9ba5 commit f755f4c

21 files changed

+159
-58
lines changed

Diff for: ‎compiler/rustc_target/src/spec/json.rs

+15
Original file line numberDiff line numberDiff line change
@@ -128,6 +128,19 @@ impl Target {
128128
Some(Ok(()))
129129
})).unwrap_or(Ok(()))
130130
} );
131+
($key_name:ident, RustcAbi) => ( {
132+
let name = (stringify!($key_name)).replace("_", "-");
133+
obj.remove(&name).and_then(|o| o.as_str().and_then(|s| {
134+
match s.parse::<super::RustcAbi>() {
135+
Ok(rustc_abi) => base.$key_name = Some(rustc_abi),
136+
_ => return Some(Err(format!(
137+
"'{s}' is not a valid value for rustc-abi. \
138+
Use 'x86-softfloat' or leave the field unset."
139+
))),
140+
}
141+
Some(Ok(()))
142+
})).unwrap_or(Ok(()))
143+
} );
131144
($key_name:ident, RelocModel) => ( {
132145
let name = (stringify!($key_name)).replace("_", "-");
133146
obj.remove(&name).and_then(|o| o.as_str().and_then(|s| {
@@ -611,6 +624,7 @@ impl Target {
611624
key!(llvm_mcount_intrinsic, optional);
612625
key!(llvm_abiname);
613626
key!(llvm_floatabi, FloatAbi)?;
627+
key!(rustc_abi, RustcAbi)?;
614628
key!(relax_elf_relocations, bool);
615629
key!(llvm_args, list);
616630
key!(use_ctors_section, bool);
@@ -786,6 +800,7 @@ impl ToJson for Target {
786800
target_option_val!(llvm_mcount_intrinsic);
787801
target_option_val!(llvm_abiname);
788802
target_option_val!(llvm_floatabi);
803+
target_option_val!(rustc_abi);
789804
target_option_val!(relax_elf_relocations);
790805
target_option_val!(llvm_args);
791806
target_option_val!(use_ctors_section);

Diff for: ‎compiler/rustc_target/src/spec/mod.rs

+45-4
Original file line numberDiff line numberDiff line change
@@ -1114,6 +1114,33 @@ impl ToJson for FloatAbi {
11141114
}
11151115
}
11161116

1117+
/// The Rustc-specific variant of the ABI used for this target.
1118+
#[derive(Clone, Copy, PartialEq, Hash, Debug)]
1119+
pub enum RustcAbi {
1120+
/// On x86-32/64 only: do not use any FPU or SIMD registers for the ABI.
1121+
X86Softfloat,
1122+
}
1123+
1124+
impl FromStr for RustcAbi {
1125+
type Err = ();
1126+
1127+
fn from_str(s: &str) -> Result<RustcAbi, ()> {
1128+
Ok(match s {
1129+
"x86-softfloat" => RustcAbi::X86Softfloat,
1130+
_ => return Err(()),
1131+
})
1132+
}
1133+
}
1134+
1135+
impl ToJson for RustcAbi {
1136+
fn to_json(&self) -> Json {
1137+
match *self {
1138+
RustcAbi::X86Softfloat => "x86-softfloat",
1139+
}
1140+
.to_json()
1141+
}
1142+
}
1143+
11171144
#[derive(Clone, Copy, PartialEq, Hash, Debug)]
11181145
pub enum TlsModel {
11191146
GeneralDynamic,
@@ -2502,6 +2529,12 @@ pub struct TargetOptions {
25022529
/// If not provided, LLVM will infer the float ABI from the target triple (`llvm_target`).
25032530
pub llvm_floatabi: Option<FloatAbi>,
25042531

2532+
/// Picks a specific ABI for this target. This is *not* just for "Rust" ABI functions,
2533+
/// it can also affect "C" ABI functions; the point is that this flag is interpreted by
2534+
/// rustc and not forwarded to LLVM.
2535+
/// So far, this is only used on x86.
2536+
pub rustc_abi: Option<RustcAbi>,
2537+
25052538
/// Whether or not RelaxElfRelocation flag will be passed to the linker
25062539
pub relax_elf_relocations: bool,
25072540

@@ -2661,10 +2694,6 @@ impl TargetOptions {
26612694
.collect();
26622695
}
26632696
}
2664-
2665-
pub(crate) fn has_feature(&self, search_feature: &str) -> bool {
2666-
self.features.split(',').any(|f| f.strip_prefix('+').is_some_and(|f| f == search_feature))
2667-
}
26682697
}
26692698

26702699
impl Default for TargetOptions {
@@ -2770,6 +2799,7 @@ impl Default for TargetOptions {
27702799
llvm_mcount_intrinsic: None,
27712800
llvm_abiname: "".into(),
27722801
llvm_floatabi: None,
2802+
rustc_abi: None,
27732803
relax_elf_relocations: false,
27742804
llvm_args: cvs![],
27752805
use_ctors_section: false,
@@ -3236,6 +3266,17 @@ impl Target {
32363266
_ => {}
32373267
}
32383268

3269+
// Check consistency of Rust ABI declaration.
3270+
if let Some(rust_abi) = self.rustc_abi {
3271+
match rust_abi {
3272+
RustcAbi::X86Softfloat => check_matches!(
3273+
&*self.arch,
3274+
"x86" | "x86_64",
3275+
"`x86-softfloat` ABI is only valid for x86 targets"
3276+
),
3277+
}
3278+
}
3279+
32393280
// Check that the given target-features string makes some basic sense.
32403281
if !self.features.is_empty() {
32413282
let mut features_enabled = FxHashSet::default();

Diff for: ‎compiler/rustc_target/src/spec/targets/i686_unknown_uefi.rs

+2-1
Original file line numberDiff line numberDiff line change
@@ -5,7 +5,7 @@
55
// The cdecl ABI is used. It differs from the stdcall or fastcall ABI.
66
// "i686-unknown-windows" is used to get the minimal subset of windows-specific features.
77

8-
use crate::spec::{Target, base};
8+
use crate::spec::{RustcAbi, Target, base};
99

1010
pub(crate) fn target() -> Target {
1111
let mut base = base::uefi_msvc::opts();
@@ -22,6 +22,7 @@ pub(crate) fn target() -> Target {
2222
// If you initialize FP units yourself, you can override these flags with custom linker
2323
// arguments, thus giving you access to full MMX/SSE acceleration.
2424
base.features = "-mmx,-sse,+soft-float".into();
25+
base.rustc_abi = Some(RustcAbi::X86Softfloat);
2526

2627
// Use -GNU here, because of the reason below:
2728
// Background and Problem:

Diff for: ‎compiler/rustc_target/src/spec/targets/x86_64_unknown_none.rs

+3-2
Original file line numberDiff line numberDiff line change
@@ -5,8 +5,8 @@
55
// features.
66

77
use crate::spec::{
8-
Cc, CodeModel, LinkerFlavor, Lld, PanicStrategy, RelroLevel, SanitizerSet, StackProbeType,
9-
Target, TargetOptions,
8+
Cc, CodeModel, LinkerFlavor, Lld, PanicStrategy, RelroLevel, RustcAbi, SanitizerSet,
9+
StackProbeType, Target, TargetOptions,
1010
};
1111

1212
pub(crate) fn target() -> Target {
@@ -20,6 +20,7 @@ pub(crate) fn target() -> Target {
2020
relro_level: RelroLevel::Full,
2121
linker_flavor: LinkerFlavor::Gnu(Cc::No, Lld::Yes),
2222
linker: Some("rust-lld".into()),
23+
rustc_abi: Some(RustcAbi::X86Softfloat),
2324
features: "-mmx,-sse,-sse2,-sse3,-ssse3,-sse4.1,-sse4.2,-avx,-avx2,+soft-float".into(),
2425
supported_sanitizers: SanitizerSet::KCFI | SanitizerSet::KERNELADDRESS,
2526
disable_redzone: true,

Diff for: ‎compiler/rustc_target/src/spec/targets/x86_64_unknown_uefi.rs

+2-1
Original file line numberDiff line numberDiff line change
@@ -6,7 +6,7 @@
66
// LLVM. "x86_64-unknown-windows" is used to get the minimal subset of windows-specific features.
77

88
use crate::abi::call::Conv;
9-
use crate::spec::{Target, base};
9+
use crate::spec::{RustcAbi, Target, base};
1010

1111
pub(crate) fn target() -> Target {
1212
let mut base = base::uefi_msvc::opts();
@@ -26,6 +26,7 @@ pub(crate) fn target() -> Target {
2626
// If you initialize FP units yourself, you can override these flags with custom linker
2727
// arguments, thus giving you access to full MMX/SSE acceleration.
2828
base.features = "-mmx,-sse,+soft-float".into();
29+
base.rustc_abi = Some(RustcAbi::X86Softfloat);
2930

3031
Target {
3132
llvm_target: "x86_64-unknown-windows".into(),

Diff for: ‎compiler/rustc_target/src/target_features.rs

+36-16
Original file line numberDiff line numberDiff line change
@@ -5,7 +5,7 @@ use rustc_data_structures::fx::{FxHashMap, FxHashSet};
55
use rustc_data_structures::stable_hasher::{HashStable, StableHasher};
66
use rustc_span::{Symbol, sym};
77

8-
use crate::spec::{FloatAbi, Target};
8+
use crate::spec::{FloatAbi, RustcAbi, Target};
99

1010
/// Features that control behaviour of rustc, rather than the codegen.
1111
/// These exist globally and are not in the target-specific lists below.
@@ -417,7 +417,9 @@ const X86_FEATURES: &[(&str, Stability, ImpliedFeatures)] = &[
417417
("sha512", Unstable(sym::sha512_sm_x86), &["avx2"]),
418418
("sm3", Unstable(sym::sha512_sm_x86), &["avx"]),
419419
("sm4", Unstable(sym::sha512_sm_x86), &["avx2"]),
420-
("soft-float", Stability::Forbidden { reason: "unsound because it changes float ABI" }, &[]),
420+
// This cannot actually be toggled, the ABI always fixes it, so it'd make little sense to
421+
// stabilize. It must be in this list for the ABI check to be able to use it.
422+
("soft-float", Stability::Unstable(sym::x87_target_feature), &[]),
421423
("sse", Stable, &[]),
422424
("sse2", Stable, &["sse"]),
423425
("sse3", Stable, &["sse2"]),
@@ -768,23 +770,41 @@ impl Target {
768770
// questions "which ABI is used".
769771
match &*self.arch {
770772
"x86" => {
771-
// We support 2 ABIs, hardfloat (default) and softfloat.
772-
// x86 has no sane ABI indicator so we have to use the target feature.
773-
if self.has_feature("soft-float") {
774-
NOTHING
775-
} else {
776-
// Hardfloat ABI. x87 must be enabled.
777-
FeatureConstraints { required: &["x87"], incompatible: &[] }
773+
// We use our own ABI indicator here; LLVM does not have anything native.
774+
// Every case should require or forbid `soft-float`!
775+
match self.rustc_abi {
776+
None => {
777+
// Default hardfloat ABI.
778+
// x87 must be enabled, soft-float must be disabled.
779+
FeatureConstraints { required: &["x87"], incompatible: &["soft-float"] }
780+
}
781+
Some(RustcAbi::X86Softfloat) => {
782+
// Softfloat ABI, requires corresponding target feature. That feature trumps
783+
// `x87` and all other FPU features so those do not matter.
784+
// Note that this one requirement is the entire implementation of the ABI!
785+
// LLVM handles the rest.
786+
FeatureConstraints { required: &["soft-float"], incompatible: &[] }
787+
}
778788
}
779789
}
780790
"x86_64" => {
781-
// We support 2 ABIs, hardfloat (default) and softfloat.
782-
// x86 has no sane ABI indicator so we have to use the target feature.
783-
if self.has_feature("soft-float") {
784-
NOTHING
785-
} else {
786-
// Hardfloat ABI. x87 and SSE2 must be enabled.
787-
FeatureConstraints { required: &["x87", "sse2"], incompatible: &[] }
791+
// We use our own ABI indicator here; LLVM does not have anything native.
792+
// Every case should require or forbid `soft-float`!
793+
match self.rustc_abi {
794+
None => {
795+
// Default hardfloat ABI. On x86-64, this always includes SSE2.
796+
FeatureConstraints {
797+
required: &["x87", "sse2"],
798+
incompatible: &["soft-float"],
799+
}
800+
}
801+
Some(RustcAbi::X86Softfloat) => {
802+
// Softfloat ABI, requires corresponding target feature. That feature trumps
803+
// `x87` and all other FPU features so those do not matter.
804+
// Note that this one requirement is the entire implementation of the ABI!
805+
// LLVM handles the rest.
806+
FeatureConstraints { required: &["soft-float"], incompatible: &[] }
807+
}
788808
}
789809
}
790810
"arm" => {

Diff for: ‎tests/ui/target-feature/forbidden-hardfloat-target-feature-attribute.rs

+1
Original file line numberDiff line numberDiff line change
@@ -1,3 +1,4 @@
1+
//! Ensure ABI-incompatible features cannot be enabled via `#[target_feature]`.
12
//@ compile-flags: --target=riscv32e-unknown-none-elf --crate-type=lib
23
//@ needs-llvm-components: riscv
34
#![feature(no_core, lang_items, riscv_target_feature)]

Diff for: ‎tests/ui/target-feature/forbidden-hardfloat-target-feature-attribute.stderr

+1-1
Original file line numberDiff line numberDiff line change
@@ -1,5 +1,5 @@
11
error: target feature `d` cannot be enabled with `#[target_feature]`: this feature is incompatible with the target ABI
2-
--> $DIR/forbidden-hardfloat-target-feature-attribute.rs:9:18
2+
--> $DIR/forbidden-hardfloat-target-feature-attribute.rs:10:18
33
|
44
LL | #[target_feature(enable = "d")]
55
| ^^^^^^^^^^^^

Diff for: ‎tests/ui/target-feature/forbidden-hardfloat-target-feature-cfg.rs

-14
This file was deleted.

Diff for: ‎tests/ui/target-feature/forbidden-hardfloat-target-feature-flag-disable-implied.rs

+3
Original file line numberDiff line numberDiff line change
@@ -1,8 +1,11 @@
1+
//! Ensure that if disabling a target feature implies disabling an ABI-required target feature,
2+
//! we complain.
13
//@ compile-flags: --target=x86_64-unknown-linux-gnu --crate-type=lib
24
//@ needs-llvm-components: x86
35
//@ compile-flags: -Ctarget-feature=-sse
46
// For now this is just a warning.
57
//@ build-pass
8+
//@error-pattern: must be enabled to ensure that the ABI
69
#![feature(no_core, lang_items)]
710
#![no_core]
811

Diff for: ‎tests/ui/target-feature/forbidden-hardfloat-target-feature-flag-disable-neon.rs

+1
Original file line numberDiff line numberDiff line change
@@ -3,6 +3,7 @@
33
//@ compile-flags: -Ctarget-feature=-neon
44
// For now this is just a warning.
55
//@ build-pass
6+
//@error-pattern: must be enabled to ensure that the ABI
67
#![feature(no_core, lang_items)]
78
#![no_core]
89

Diff for: ‎tests/ui/target-feature/forbidden-hardfloat-target-feature-flag-disable.rs

+2
Original file line numberDiff line numberDiff line change
@@ -1,8 +1,10 @@
1+
//! Ensure ABI-required features cannot be disabled via `-Ctarget-feature`.
12
//@ compile-flags: --target=x86_64-unknown-linux-gnu --crate-type=lib
23
//@ needs-llvm-components: x86
34
//@ compile-flags: -Ctarget-feature=-x87
45
// For now this is just a warning.
56
//@ build-pass
7+
//@error-pattern: must be enabled to ensure that the ABI
68
#![feature(no_core, lang_items)]
79
#![no_core]
810

Diff for: ‎tests/ui/target-feature/forbidden-hardfloat-target-feature-flag.rs

+12
Original file line numberDiff line numberDiff line change
@@ -0,0 +1,12 @@
1+
//! Ensure ABI-incompatible features cannot be enabled via `-Ctarget-feature`.
2+
//@ compile-flags: --target=x86_64-unknown-linux-gnu --crate-type=lib
3+
//@ needs-llvm-components: x86
4+
//@ compile-flags: -Ctarget-feature=+soft-float
5+
// For now this is just a warning.
6+
//@ build-pass
7+
//@error-pattern: must be disabled to ensure that the ABI
8+
#![feature(no_core, lang_items, riscv_target_feature)]
9+
#![no_core]
10+
11+
#[lang = "sized"]
12+
pub trait Sized {}

Diff for: ‎tests/ui/target-feature/forbidden-hardfloat-target-feature-flag.stderr

+11
Original file line numberDiff line numberDiff line change
@@ -0,0 +1,11 @@
1+
warning: target feature `soft-float` must be disabled to ensure that the ABI of the current target can be implemented correctly
2+
|
3+
= note: this was previously accepted by the compiler but is being phased out; it will become a hard error in a future release!
4+
= note: for more information, see issue #116344 <https://github.com/rust-lang/rust/issues/116344>
5+
6+
warning: unstable feature specified for `-Ctarget-feature`: `soft-float`
7+
|
8+
= note: this feature is not stably supported; its behavior can change in the future
9+
10+
warning: 2 warnings emitted
11+

Diff for: ‎tests/ui/target-feature/forbidden-target-feature-attribute.rs

+4-3
Original file line numberDiff line numberDiff line change
@@ -1,11 +1,12 @@
1-
//@ compile-flags: --target=x86_64-unknown-linux-gnu --crate-type=lib
2-
//@ needs-llvm-components: x86
1+
//! Ensure "forbidden" target features cannot be enabled via `#[target_feature]`.
2+
//@ compile-flags: --target=riscv32e-unknown-none-elf --crate-type=lib
3+
//@ needs-llvm-components: riscv
34
#![feature(no_core, lang_items)]
45
#![no_core]
56

67
#[lang = "sized"]
78
pub trait Sized {}
89

9-
#[target_feature(enable = "soft-float")]
10+
#[target_feature(enable = "forced-atomics")]
1011
//~^ERROR: cannot be enabled with
1112
pub unsafe fn my_fun() {}

Diff for: ‎tests/ui/target-feature/forbidden-target-feature-attribute.stderr

+4-4
Original file line numberDiff line numberDiff line change
@@ -1,8 +1,8 @@
1-
error: target feature `soft-float` cannot be enabled with `#[target_feature]`: unsound because it changes float ABI
2-
--> $DIR/forbidden-target-feature-attribute.rs:9:18
1+
error: target feature `forced-atomics` cannot be enabled with `#[target_feature]`: unsound because it changes the ABI of atomic operations
2+
--> $DIR/forbidden-target-feature-attribute.rs:10:18
33
|
4-
LL | #[target_feature(enable = "soft-float")]
5-
| ^^^^^^^^^^^^^^^^^^^^^
4+
LL | #[target_feature(enable = "forced-atomics")]
5+
| ^^^^^^^^^^^^^^^^^^^^^^^^^
66

77
error: aborting due to 1 previous error
88

Diff for: ‎tests/ui/target-feature/forbidden-target-feature-cfg.rs

+5-4
Original file line numberDiff line numberDiff line change
@@ -1,5 +1,6 @@
1-
//@ compile-flags: --target=x86_64-unknown-none --crate-type=lib
2-
//@ needs-llvm-components: x86
1+
//! Ensure "forbidden" target features are not exposed via `cfg`.
2+
//@ compile-flags: --target=riscv32e-unknown-none-elf --crate-type=lib
3+
//@ needs-llvm-components: riscv
34
//@ check-pass
45
#![feature(no_core, lang_items)]
56
#![no_core]
@@ -10,5 +11,5 @@ pub trait Sized {}
1011

1112
// The compile_error macro does not exist, so if the `cfg` evaluates to `true` this
1213
// complains about the missing macro rather than showing the error... but that's good enough.
13-
#[cfg(target_feature = "soft-float")]
14-
compile_error!("the soft-float feature should not be exposed in `cfg`");
14+
#[cfg(target_feature = "forced-atomics")]
15+
compile_error!("the forced-atomics feature should not be exposed in `cfg`");

Diff for: ‎tests/ui/target-feature/forbidden-target-feature-flag-disable.rs

+5-3
Original file line numberDiff line numberDiff line change
@@ -1,8 +1,10 @@
1-
//@ compile-flags: --target=x86_64-unknown-linux-gnu --crate-type=lib
2-
//@ needs-llvm-components: x86
3-
//@ compile-flags: -Ctarget-feature=-soft-float
1+
//! Ensure "forbidden" target features cannot be disabled via `-Ctarget-feature`.
2+
//@ compile-flags: --target=riscv32e-unknown-none-elf --crate-type=lib
3+
//@ needs-llvm-components: riscv
4+
//@ compile-flags: -Ctarget-feature=-forced-atomics
45
// For now this is just a warning.
56
//@ build-pass
7+
//@error-pattern: unsound because it changes the ABI
68
#![feature(no_core, lang_items)]
79
#![no_core]
810

Diff for: ‎tests/ui/target-feature/forbidden-target-feature-flag-disable.stderr

+1-1
Original file line numberDiff line numberDiff line change
@@ -1,4 +1,4 @@
1-
warning: target feature `soft-float` cannot be disabled with `-Ctarget-feature`: unsound because it changes float ABI
1+
warning: target feature `forced-atomics` cannot be disabled with `-Ctarget-feature`: unsound because it changes the ABI of atomic operations
22
|
33
= note: this was previously accepted by the compiler but is being phased out; it will become a hard error in a future release!
44
= note: for more information, see issue #116344 <https://github.com/rust-lang/rust/issues/116344>

0 commit comments

Comments
 (0)