add asm_cfg feature gate

Author: folkertdev

compiler/rustc_builtin_macros/messages.ftl

@@ -1,6 +1,9 @@
 builtin_macros_alloc_error_must_be_fn = alloc_error_handler must be a function
 builtin_macros_alloc_must_statics = allocators must be statics
 
+builtin_macros_asm_cfg =
+    attributes on assembly are unstable
+
 builtin_macros_asm_clobber_abi = clobber_abi
 builtin_macros_asm_clobber_no_reg = asm with `clobber_abi` must specify explicit registers for outputs
 builtin_macros_asm_clobber_outputs = generic outputs

compiler/rustc_builtin_macros/src/asm.rs

@@ -10,13 +10,14 @@ use rustc_index::bit_set::GrowableBitSet;
 use rustc_parse::exp;
 use rustc_parse::parser::{ExpKeywordPair, Parser};
 use rustc_session::lint;
-use rustc_span::{ErrorGuaranteed, InnerSpan, Span, Symbol, kw};
+use rustc_session::parse::feature_err;
+use rustc_span::{ErrorGuaranteed, InnerSpan, Span, Symbol, kw, sym};
 use rustc_target::asm::InlineAsmArch;
 use smallvec::smallvec;
 use {rustc_ast as ast, rustc_parse_format as parse};
 
-use crate::errors;
 use crate::util::{ExprToSpannedString, expr_to_spanned_string};
+use crate::{errors, fluent_generated as fluent};
 
 pub struct AsmArgs {
     pub templates: Vec<P<ast::Expr>>,
@@ -59,19 +60,47 @@ fn eat_operand_keyword<'a>(
     }
 }
 
+/// A parsed list of attributes that is not attached to any item.
+/// Used to check whether `asm!` arguments are configured out.
+struct AsmAttrList(ast::AttrVec);
+
+impl AsmAttrList {
+    fn parse<'a>(ecx: &ExtCtxt<'a>, p: &mut Parser<'a>) -> PResult<'a, Self> {
+        let span_start = p.token.span;
+
+        let mut attributes = ast::AttrVec::new();
+        loop {
+            if p.token != token::Pound {
+                break;
+            }
+
+            let attr = p.parse_attribute(rustc_parse::parser::attr::InnerAttrPolicy::Permitted)?;
+            attributes.push(attr);
+        }
+
+        if !attributes.is_empty() && !ecx.ecfg.features.asm_cfg() {
+            let span = span_start.to(p.prev_token.span);
+            feature_err(ecx.sess, sym::asm_cfg, span, fluent::builtin_macros_asm_cfg).emit();
+        }
+
+        Ok(Self(attributes))
+    }
+}
+
 fn parse_args<'a>(
     ecx: &ExtCtxt<'a>,
     sp: Span,
     tts: TokenStream,
     asm_macro: AsmMacro,
 ) -> PResult<'a, AsmArgs> {
     let mut p = ecx.new_parser_from_tts(tts);
-    parse_asm_args(&mut p, sp, asm_macro)
+    parse_asm_args(ecx, &mut p, sp, asm_macro)
 }
 
 // Primarily public for rustfmt consumption.
 // Internal consumers should continue to leverage `expand_asm`/`expand__global_asm`
 pub fn parse_asm_args<'a>(
+    ecx: &ExtCtxt<'a>,
     p: &mut Parser<'a>,
     sp: Span,
     asm_macro: AsmMacro,
@@ -82,6 +111,7 @@ pub fn parse_asm_args<'a>(
         return Err(dcx.create_err(errors::AsmRequiresTemplate { span: sp }));
     }
 
+    let _attributes = AsmAttrList::parse(ecx, p)?;
     let first_template = p.parse_expr()?;
     let mut args = AsmArgs {
         templates: vec![first_template],
@@ -108,6 +138,8 @@ pub fn parse_asm_args<'a>(
             break;
         } // accept trailing commas
 
+        let _attributes = AsmAttrList::parse(ecx, p)?;
+
         // Parse clobber_abi
         if p.eat_keyword(exp!(ClobberAbi)) {
             parse_clobber_abi(p, &mut args)?;

compiler/rustc_feature/src/unstable.rs

@@ -370,6 +370,8 @@ declare_features! (
     /// Allows inherent and trait methods with arbitrary self types that are raw pointers.
     (unstable, arbitrary_self_types_pointers, "1.83.0", Some(44874)),
     /// Enables experimental inline assembly support for additional architectures.
+    (unstable, asm_cfg, "CURRENT_RUSTC_VERSION", None),
+    /// Enables experimental inline assembly support for additional architectures.
     (unstable, asm_experimental_arch, "1.58.0", Some(93335)),
     /// Enables experimental register support in inline assembly.
     (unstable, asm_experimental_reg, "1.85.0", Some(133416)),

compiler/rustc_span/src/symbol.rs

@@ -472,6 +472,7 @@ symbols! {
         as_ref,
         as_str,
         asm,
+        asm_cfg,
         asm_const,
         asm_experimental_arch,
         asm_experimental_reg,

tests/ui/feature-gates/feature-gate-asm_cfg.rs

@@ -0,0 +1,34 @@
+//@ only-x86_64
+#![crate_type = "lib"]
+
+use std::arch::{asm, global_asm, naked_asm};
+
+global_asm!(
+    "nop",
+    #[cfg(false)] //~ ERROR attributes on assembly are unstable
+    "nop"
+);
+
+#[unsafe(naked)]
+#[no_mangle]
+extern "C" fn naked() {
+    naked_asm!(
+        "mov rax, 5",
+        #[cfg(false)] //~ ERROR attributes on assembly are unstable
+        "mov rax, {a}",
+        "ret",
+        #[cfg(false)] //~ ERROR attributes on assembly are unstable
+        a = const 10,
+    )
+}
+
+fn asm() {
+    unsafe {
+        asm!(
+            "nop",
+            #[cfg(false)] //~ ERROR attributes on assembly are unstable
+            clobber_abi("C"),
+            clobber_abi("C"), //~ ERROR `C` ABI specified multiple times
+        );
+    }
+}

tests/ui/feature-gates/feature-gate-asm_cfg.stderr

@@ -0,0 +1,47 @@
+error[E0658]: attributes on assembly are unstable
+  --> $DIR/feature-gate-asm_cfg.rs:8:5
+   |
+LL |     #[cfg(false)]
+   |     ^^^^^^^^^^^^^
+   |
+   = help: add `#![feature(asm_cfg)]` to the crate attributes to enable
+   = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date
+
+error[E0658]: attributes on assembly are unstable
+  --> $DIR/feature-gate-asm_cfg.rs:17:9
+   |
+LL |         #[cfg(false)]
+   |         ^^^^^^^^^^^^^
+   |
+   = help: add `#![feature(asm_cfg)]` to the crate attributes to enable
+   = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date
+
+error[E0658]: attributes on assembly are unstable
+  --> $DIR/feature-gate-asm_cfg.rs:20:9
+   |
+LL |         #[cfg(false)]
+   |         ^^^^^^^^^^^^^
+   |
+   = help: add `#![feature(asm_cfg)]` to the crate attributes to enable
+   = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date
+
+error[E0658]: attributes on assembly are unstable
+  --> $DIR/feature-gate-asm_cfg.rs:29:13
+   |
+LL |             #[cfg(false)]
+   |             ^^^^^^^^^^^^^
+   |
+   = help: add `#![feature(asm_cfg)]` to the crate attributes to enable
+   = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date
+
+error: `C` ABI specified multiple times
+  --> $DIR/feature-gate-asm_cfg.rs:31:13
+   |
+LL |             clobber_abi("C"),
+   |             ---------------- previously specified here
+LL |             clobber_abi("C"),
+   |             ^^^^^^^^^^^^^^^^
+
+error: aborting due to 5 previous errors
+
+For more information about this error, try `rustc --explain E0658`.