Rollup merge of #147736 - folkertdev:stabilize-asm-cfg, r=jdonszelmann
Stabilize `asm_cfg` tracking issue: https://github.com/rust-lang/rust/issues/140364 closes https://github.com/rust-lang/rust/issues/140364 Reference PR: - https://github.com/rust-lang/reference/pull/2063 # Request for Stabilization ## Summary The `cfg_asm` feature allows `#[cfg(...)]` and `#[cfg_attr(...)]` on the arguments of the assembly macros, for instance: ```rust asm!( // or global_asm! or naked_asm! "nop", #[cfg(target_feature = "sse2")] "nop", // ... #[cfg(target_feature = "sse2")] a = const 123, // only used on sse2 ); ``` ## Semantics Templates, operands, `options` and `clobber_abi` in the assembly macros (`asm!`, `naked_asm!` and `global_asm!`) can be annotated with `#[cfg(...)]` and `#[cfg_attr(...)]`. When the condition evaluates to true, the annotated argument has no effect, and is completely ignored when expanding the assembly macro. ## Documentation reference PR: https://github.com/rust-lang/reference/pull/2063 ## Tests - [tests/ui/asm/cfg.rs](https://github.com/rust-lang/rust/blob/master/tests/ui/asm/cfg.rs) checks that `cfg`'d arguments where the condition evaluates to false have no effect - [tests/ui/asm/cfg-parse-error.rs](https://github.com/rust-lang/rust/blob/master/tests/ui/asm/cfg.rs) checks the parsing rules (parsing effectively assumes that the cfg conditions are all true) ## History - https://github.com/rust-lang/rust/issues/140279 - https://github.com/rust-lang/rust/pull/140367 # Resolved questions **how are other attributes handled** Other attributes are parsed, but explicitly rejected. # unresolved questions **operand before template** The current implementation expects at least one template string before any operands. In the example below, if the `cfg` condition evaluates to true, the assembly block is ill-formed. But even when it evaluates to `false` this block is rejected, because the parser still expects just a template (a template is parsed as an expression and then validated to ensure that it is or expands to a string literal). Changing how this works is difficult. ```rust // This is rejected because `a = out(reg) x` does not parse as an expresion. asm!( #[cfg(false)] a = out(reg) x, //~ ERROR expected token: `,` "", ); ``` **lint on positional arguments?** Adding a lint to warn on the definition or use of positional arguments being `cfg`'d out was discussed in https://github.com/rust-lang/rust/issues/140279#issuecomment-2832237372 and subsequent comments. Such a lint is not currently implemented, but that may not be a blocker based on the comments there. r? `@traviscross` (I'm assuming you'll reassign as needed)
This commit is contained in:
Matthias Krüger
GitHub
commit
04e4f95e7e
10 changed files with 12 additions and 131 deletions
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@ -3,8 +3,6 @@ builtin_macros_alloc_must_statics = allocators must be statics
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builtin_macros_asm_attribute_not_supported =
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this attribute is not supported on assembly
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builtin_macros_asm_cfg =
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the `#[cfg(/* ... */)]` and `#[cfg_attr(/* ... */)]` attributes on assembly are unstable
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builtin_macros_asm_clobber_abi = clobber_abi
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builtin_macros_asm_clobber_no_reg = asm with `clobber_abi` must specify explicit registers for outputs
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@ -6,14 +6,13 @@ use rustc_expand::base::*;
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use rustc_index::bit_set::GrowableBitSet;
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use rustc_parse::parser::asm::*;
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use rustc_session::lint;
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use rustc_session::parse::feature_err;
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use rustc_span::{ErrorGuaranteed, InnerSpan, Span, Symbol, sym};
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use rustc_target::asm::InlineAsmArch;
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use smallvec::smallvec;
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use {rustc_ast as ast, rustc_parse_format as parse};
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use crate::errors;
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use crate::util::{ExprToSpannedString, expr_to_spanned_string};
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use crate::{errors, fluent_generated as fluent};
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/// Validated assembly arguments, ready for macro expansion.
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struct ValidatedAsmArgs {
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@ -64,22 +63,13 @@ fn validate_asm_args<'a>(
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for arg in args {
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for attr in arg.attributes.0.iter() {
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match attr.name() {
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Some(sym::cfg | sym::cfg_attr) => {
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if !ecx.ecfg.features.asm_cfg() {
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let span = attr.span();
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feature_err(ecx.sess, sym::asm_cfg, span, fluent::builtin_macros_asm_cfg)
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.emit();
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}
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}
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_ => {
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ecx.dcx().emit_err(errors::AsmAttributeNotSupported { span: attr.span() });
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}
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if !matches!(attr.name(), Some(sym::cfg | sym::cfg_attr)) {
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ecx.dcx().emit_err(errors::AsmAttributeNotSupported { span: attr.span() });
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}
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}
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// Skip arguments that are configured out.
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if ecx.ecfg.features.asm_cfg() && strip_unconfigured.configure(arg.attributes).is_none() {
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if strip_unconfigured.configure(arg.attributes).is_none() {
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continue;
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}
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@ -60,6 +60,8 @@ declare_features! (
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(accepted, adx_target_feature, "1.61.0", Some(44839)),
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/// Allows explicit discriminants on non-unit enum variants.
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(accepted, arbitrary_enum_discriminant, "1.66.0", Some(60553)),
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/// Allows #[cfg(...)] on inline assembly templates and operands.
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(accepted, asm_cfg, "CURRENT_RUSTC_VERSION", Some(140364)),
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/// Allows using `const` operands in inline assembly.
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(accepted, asm_const, "1.82.0", Some(93332)),
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/// Allows using `label` operands in inline assembly.
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@ -382,8 +382,6 @@ declare_features! (
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(unstable, arbitrary_self_types, "1.23.0", Some(44874)),
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/// Allows inherent and trait methods with arbitrary self types that are raw pointers.
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(unstable, arbitrary_self_types_pointers, "1.83.0", Some(44874)),
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/// Allows #[cfg(...)] on inline assembly templates and operands.
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(unstable, asm_cfg, "1.89.0", Some(140364)),
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/// Enables experimental inline assembly support for additional architectures.
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(unstable, asm_experimental_arch, "1.58.0", Some(93335)),
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/// Enables experimental register support in inline assembly.
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@ -7,7 +7,6 @@
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#![feature(compiler_builtins)]
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#![feature(core_intrinsics)]
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#![feature(linkage)]
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#![feature(asm_cfg)]
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#![feature(naked_functions)]
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#![feature(repr_simd)]
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#![feature(macro_metavar_expr_concat)]
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@ -1,5 +1,4 @@
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//@ needs-asm-support
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#![feature(asm_cfg)]
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use std::arch::asm;
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@ -1,5 +1,5 @@
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error: expected one of `#`, `clobber_abi`, `const`, `in`, `inlateout`, `inout`, `label`, `lateout`, `options`, `out`, or `sym`, found `""`
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--> $DIR/cfg-parse-error.rs:16:13
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--> $DIR/cfg-parse-error.rs:15:13
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LL | a = out(reg) x,
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| - expected one of 11 possible tokens
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@ -7,7 +7,7 @@ LL | "",
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| ^^ unexpected token
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error: expected one of `#`, `clobber_abi`, `const`, `in`, `inlateout`, `inout`, `label`, `lateout`, `options`, `out`, or `sym`, found `""`
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--> $DIR/cfg-parse-error.rs:26:13
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--> $DIR/cfg-parse-error.rs:25:13
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LL | },
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| - expected one of 11 possible tokens
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@ -15,19 +15,19 @@ LL | "",
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| ^^ unexpected token
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error: expected token: `,`
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--> $DIR/cfg-parse-error.rs:41:26
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--> $DIR/cfg-parse-error.rs:40:26
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LL | a = out(reg) x,
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| ^ expected `,`
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error: this attribute is not supported on assembly
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--> $DIR/cfg-parse-error.rs:47:13
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--> $DIR/cfg-parse-error.rs:46:13
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LL | #[rustfmt::skip]
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| ^^^^^^^^^^^^^^^^
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error: an inner attribute is not permitted in this context
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--> $DIR/cfg-parse-error.rs:53:13
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--> $DIR/cfg-parse-error.rs:52:13
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LL | #![rustfmt::skip]
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| ^^^^^^^^^^^^^^^^^
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@ -3,7 +3,7 @@
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//@ revisions: reva revb
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//@ only-x86_64
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//@ run-pass
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#![feature(asm_cfg, cfg_select)]
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#![feature(cfg_select)]
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use std::arch::{asm, naked_asm};
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@ -1,48 +0,0 @@
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//@ only-x86_64
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#![crate_type = "lib"]
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use std::arch::{asm, global_asm, naked_asm};
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global_asm!(
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"nop",
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#[cfg(false)]
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//~^ ERROR the `#[cfg(/* ... */)]` and `#[cfg_attr(/* ... */)]` attributes on assembly are unstable
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"nop"
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);
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#[unsafe(naked)]
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#[no_mangle]
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extern "C" fn naked() {
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naked_asm!(
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"mov rax, 5",
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#[cfg(false)]
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//~^ ERROR the `#[cfg(/* ... */)]` and `#[cfg_attr(/* ... */)]` attributes on assembly are unstable
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"mov rax, {a}",
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"ret",
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#[cfg(false)]
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//~^ ERROR the `#[cfg(/* ... */)]` and `#[cfg_attr(/* ... */)]` attributes on assembly are unstable
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a = const 10,
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)
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}
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fn asm() {
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unsafe {
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asm!(
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"nop",
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#[cfg(false)]
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//~^ ERROR the `#[cfg(/* ... */)]` and `#[cfg_attr(/* ... */)]` attributes on assembly are unstable
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clobber_abi("C"),
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clobber_abi("C"), //~ ERROR `C` ABI specified multiple times
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);
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}
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}
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fn bad_attribute() {
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unsafe {
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asm!(
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#[inline]
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//~^ ERROR this attribute is not supported on assembly
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"nop"
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)
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};
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}
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@ -1,57 +0,0 @@
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error[E0658]: the `#[cfg(/* ... */)]` and `#[cfg_attr(/* ... */)]` attributes on assembly are unstable
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--> $DIR/feature-gate-asm_cfg.rs:8:5
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LL | #[cfg(false)]
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| ^^^^^^^^^^^^^
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= note: see issue #140364 <https://github.com/rust-lang/rust/issues/140364> for more information
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= help: add `#![feature(asm_cfg)]` to the crate attributes to enable
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= note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date
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error[E0658]: the `#[cfg(/* ... */)]` and `#[cfg_attr(/* ... */)]` attributes on assembly are unstable
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--> $DIR/feature-gate-asm_cfg.rs:18:9
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LL | #[cfg(false)]
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| ^^^^^^^^^^^^^
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= note: see issue #140364 <https://github.com/rust-lang/rust/issues/140364> for more information
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= help: add `#![feature(asm_cfg)]` to the crate attributes to enable
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= note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date
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error[E0658]: the `#[cfg(/* ... */)]` and `#[cfg_attr(/* ... */)]` attributes on assembly are unstable
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--> $DIR/feature-gate-asm_cfg.rs:22:9
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LL | #[cfg(false)]
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| ^^^^^^^^^^^^^
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= note: see issue #140364 <https://github.com/rust-lang/rust/issues/140364> for more information
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= help: add `#![feature(asm_cfg)]` to the crate attributes to enable
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= note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date
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error[E0658]: the `#[cfg(/* ... */)]` and `#[cfg_attr(/* ... */)]` attributes on assembly are unstable
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--> $DIR/feature-gate-asm_cfg.rs:32:13
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LL | #[cfg(false)]
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| ^^^^^^^^^^^^^
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= note: see issue #140364 <https://github.com/rust-lang/rust/issues/140364> for more information
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= help: add `#![feature(asm_cfg)]` to the crate attributes to enable
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= note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date
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error: this attribute is not supported on assembly
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--> $DIR/feature-gate-asm_cfg.rs:43:13
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LL | #[inline]
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| ^^^^^^^^^
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error: `C` ABI specified multiple times
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--> $DIR/feature-gate-asm_cfg.rs:35:13
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LL | clobber_abi("C"),
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| ---------------- previously specified here
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LL | clobber_abi("C"),
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| ^^^^^^^^^^^^^^^^
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error: aborting due to 6 previous errors
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For more information about this error, try `rustc --explain E0658`.
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