4 files changed, 480 insertions, 0 deletions
diff --git a/compiler/rustc_parse/messages.ftl b/compiler/rustc_parse/messages.ftl
index a6919afef12..1f221b4bf78 100644
--- a/compiler/rustc_parse/messages.ftl
+++ b/compiler/rustc_parse/messages.ftl
@@ -8,6 +8,30 @@ parse_array_brackets_instead_of_braces = this is a block expression, not an arra
 
 parse_array_index_offset_of = array indexing not supported in offset_of
 
+parse_asm_expected_comma = expected token: `,`
+    .label = expected `,`
+
+parse_asm_expected_other = expected operand, {$is_inline_asm ->
+    [false] options
+    *[true] clobber_abi, options
+    }, or additional template string
+
+parse_asm_expected_register_class_or_explicit_register = expected register class or explicit register
+
+parse_asm_expected_string_literal = expected string literal
+    .label = not a string literal
+
+parse_asm_non_abi = at least one abi must be provided as an argument to `clobber_abi`
+
+parse_asm_requires_template = requires at least a template string argument
+
+parse_asm_sym_no_path = expected a path for argument to `sym`
+
+parse_asm_underscore_input = _ cannot be used for input operands
+
+parse_asm_unsupported_operand = the `{$symbol}` operand cannot be used with `{$macro_name}!`
+    .label = the `{$symbol}` operand is not meaningful for global-scoped inline assembly, remove it
+
 parse_assignment_else_not_allowed = <assignment> ... else {"{"} ... {"}"} is not allowed
 
 parse_associated_static_item_not_allowed = associated `static` items are not allowed
diff --git a/compiler/rustc_parse/src/errors.rs b/compiler/rustc_parse/src/errors.rs
index 31a48b22cfe..2dba568a258 100644
--- a/compiler/rustc_parse/src/errors.rs
+++ b/compiler/rustc_parse/src/errors.rs
@@ -3525,3 +3525,73 @@ pub(crate) struct MoveSelfModifier {
     pub insertion_span: Span,
     pub modifier: String,
 }
+
+#[derive(Diagnostic)]
+#[diag(parse_asm_unsupported_operand)]
+pub(crate) struct AsmUnsupportedOperand<'a> {
+    #[primary_span]
+    #[label]
+    pub(crate) span: Span,
+    pub(crate) symbol: &'a str,
+    pub(crate) macro_name: &'static str,
+}
+
+#[derive(Diagnostic)]
+#[diag(parse_asm_underscore_input)]
+pub(crate) struct AsmUnderscoreInput {
+    #[primary_span]
+    pub(crate) span: Span,
+}
+
+#[derive(Diagnostic)]
+#[diag(parse_asm_sym_no_path)]
+pub(crate) struct AsmSymNoPath {
+    #[primary_span]
+    pub(crate) span: Span,
+}
+
+#[derive(Diagnostic)]
+#[diag(parse_asm_requires_template)]
+pub(crate) struct AsmRequiresTemplate {
+    #[primary_span]
+    pub(crate) span: Span,
+}
+
+#[derive(Diagnostic)]
+#[diag(parse_asm_expected_comma)]
+pub(crate) struct AsmExpectedComma {
+    #[primary_span]
+    #[label]
+    pub(crate) span: Span,
+}
+
+#[derive(Diagnostic)]
+#[diag(parse_asm_expected_other)]
+pub(crate) struct AsmExpectedOther {
+    #[primary_span]
+    #[label(parse_asm_expected_other)]
+    pub(crate) span: Span,
+    pub(crate) is_inline_asm: bool,
+}
+
+#[derive(Diagnostic)]
+#[diag(parse_asm_non_abi)]
+pub(crate) struct NonABI {
+    #[primary_span]
+    pub(crate) span: Span,
+}
+
+#[derive(Diagnostic)]
+#[diag(parse_asm_expected_string_literal)]
+pub(crate) struct AsmExpectedStringLiteral {
+    #[primary_span]
+    #[label]
+    pub(crate) span: Span,
+}
+
+#[derive(Diagnostic)]
+#[diag(parse_asm_expected_register_class_or_explicit_register)]
+pub(crate) struct ExpectedRegisterClassOrExplicitRegister {
+    #[primary_span]
+    pub(crate) span: Span,
+}
diff --git a/compiler/rustc_parse/src/parser/asm.rs b/compiler/rustc_parse/src/parser/asm.rs
new file mode 100644
index 00000000000..d4d0612a317
--- /dev/null
+++ b/compiler/rustc_parse/src/parser/asm.rs
@@ -0,0 +1,385 @@
+use rustc_ast::ptr::P;
+use rustc_ast::{self as ast, AsmMacro};
+use rustc_span::{Span, Symbol, kw};
+
+use super::{ExpKeywordPair, ForceCollect, IdentIsRaw, Trailing, UsePreAttrPos};
+use crate::{PResult, Parser, errors, exp, token};
+
+/// An argument to one of the `asm!` macros. The argument is syntactically valid, but is otherwise
+/// not validated at all.
+pub struct AsmArg {
+    pub kind: AsmArgKind,
+    pub attributes: AsmAttrVec,
+    pub span: Span,
+}
+
+pub enum AsmArgKind {
+    Template(P<ast::Expr>),
+    Operand(Option<Symbol>, ast::InlineAsmOperand),
+    Options(Vec<AsmOption>),
+    ClobberAbi(Vec<(Symbol, Span)>),
+}
+
+pub struct AsmOption {
+    pub symbol: Symbol,
+    pub span: Span,
+    // A bitset, with only the bit for this option's symbol set.
+    pub options: ast::InlineAsmOptions,
+    // Used when suggesting to remove an option.
+    pub span_with_comma: Span,
+}
+
+/// A parsed list of attributes that is not attached to any item.
+/// Used to check whether `asm!` arguments are configured out.
+pub struct AsmAttrVec(pub ast::AttrVec);
+
+impl AsmAttrVec {
+    fn parse<'a>(p: &mut Parser<'a>) -> PResult<'a, Self> {
+        let attrs = p.parse_outer_attributes()?;
+
+        p.collect_tokens(None, attrs, ForceCollect::No, |_, attrs| {
+            Ok((Self(attrs), Trailing::No, UsePreAttrPos::No))
+        })
+    }
+}
+impl ast::HasAttrs for AsmAttrVec {
+    // Follows `ast::Expr`.
+    const SUPPORTS_CUSTOM_INNER_ATTRS: bool = false;
+
+    fn attrs(&self) -> &[rustc_ast::Attribute] {
+        &self.0
+    }
+
+    fn visit_attrs(&mut self, f: impl FnOnce(&mut rustc_ast::AttrVec)) {
+        f(&mut self.0)
+    }
+}
+
+impl ast::HasTokens for AsmAttrVec {
+    fn tokens(&self) -> Option<&rustc_ast::tokenstream::LazyAttrTokenStream> {
+        None
+    }
+
+    fn tokens_mut(&mut self) -> Option<&mut Option<rustc_ast::tokenstream::LazyAttrTokenStream>> {
+        None
+    }
+}
+
+/// Used for better error messages when operand types are used that are not
+/// supported by the current macro (e.g. `in` or `out` for `global_asm!`)
+///
+/// returns
+///
+/// - `Ok(true)` if the current token matches the keyword, and was expected
+/// - `Ok(false)` if the current token does not match the keyword
+/// - `Err(_)` if the current token matches the keyword, but was not expected
+fn eat_operand_keyword<'a>(
+    p: &mut Parser<'a>,
+    exp: ExpKeywordPair,
+    asm_macro: AsmMacro,
+) -> PResult<'a, bool> {
+    if matches!(asm_macro, AsmMacro::Asm) {
+        Ok(p.eat_keyword(exp))
+    } else {
+        let span = p.token.span;
+        if p.eat_keyword_noexpect(exp.kw) {
+            // in gets printed as `r#in` otherwise
+            let symbol = if exp.kw == kw::In { "in" } else { exp.kw.as_str() };
+            Err(p.dcx().create_err(errors::AsmUnsupportedOperand {
+                span,
+                symbol,
+                macro_name: asm_macro.macro_name(),
+            }))
+        } else {
+            Ok(false)
+        }
+    }
+}
+
+fn parse_asm_operand<'a>(
+    p: &mut Parser<'a>,
+    asm_macro: AsmMacro,
+) -> PResult<'a, Option<ast::InlineAsmOperand>> {
+    let dcx = p.dcx();
+
+    Ok(Some(if eat_operand_keyword(p, exp!(In), asm_macro)? {
+        let reg = parse_reg(p)?;
+        if p.eat_keyword(exp!(Underscore)) {
+            let err = dcx.create_err(errors::AsmUnderscoreInput { span: p.token.span });
+            return Err(err);
+        }
+        let expr = p.parse_expr()?;
+        ast::InlineAsmOperand::In { reg, expr }
+    } else if eat_operand_keyword(p, exp!(Out), asm_macro)? {
+        let reg = parse_reg(p)?;
+        let expr = if p.eat_keyword(exp!(Underscore)) { None } else { Some(p.parse_expr()?) };
+        ast::InlineAsmOperand::Out { reg, expr, late: false }
+    } else if eat_operand_keyword(p, exp!(Lateout), asm_macro)? {
+        let reg = parse_reg(p)?;
+        let expr = if p.eat_keyword(exp!(Underscore)) { None } else { Some(p.parse_expr()?) };
+        ast::InlineAsmOperand::Out { reg, expr, late: true }
+    } else if eat_operand_keyword(p, exp!(Inout), asm_macro)? {
+        let reg = parse_reg(p)?;
+        if p.eat_keyword(exp!(Underscore)) {
+            let err = dcx.create_err(errors::AsmUnderscoreInput { span: p.token.span });
+            return Err(err);
+        }
+        let expr = p.parse_expr()?;
+        if p.eat(exp!(FatArrow)) {
+            let out_expr =
+                if p.eat_keyword(exp!(Underscore)) { None } else { Some(p.parse_expr()?) };
+            ast::InlineAsmOperand::SplitInOut { reg, in_expr: expr, out_expr, late: false }
+        } else {
+            ast::InlineAsmOperand::InOut { reg, expr, late: false }
+        }
+    } else if eat_operand_keyword(p, exp!(Inlateout), asm_macro)? {
+        let reg = parse_reg(p)?;
+        if p.eat_keyword(exp!(Underscore)) {
+            let err = dcx.create_err(errors::AsmUnderscoreInput { span: p.token.span });
+            return Err(err);
+        }
+        let expr = p.parse_expr()?;
+        if p.eat(exp!(FatArrow)) {
+            let out_expr =
+                if p.eat_keyword(exp!(Underscore)) { None } else { Some(p.parse_expr()?) };
+            ast::InlineAsmOperand::SplitInOut { reg, in_expr: expr, out_expr, late: true }
+        } else {
+            ast::InlineAsmOperand::InOut { reg, expr, late: true }
+        }
+    } else if eat_operand_keyword(p, exp!(Label), asm_macro)? {
+        let block = p.parse_block()?;
+        ast::InlineAsmOperand::Label { block }
+    } else if p.eat_keyword(exp!(Const)) {
+        let anon_const = p.parse_expr_anon_const()?;
+        ast::InlineAsmOperand::Const { anon_const }
+    } else if p.eat_keyword(exp!(Sym)) {
+        let expr = p.parse_expr()?;
+        let ast::ExprKind::Path(qself, path) = &expr.kind else {
+            let err = dcx.create_err(errors::AsmSymNoPath { span: expr.span });
+            return Err(err);
+        };
+        let sym =
+            ast::InlineAsmSym { id: ast::DUMMY_NODE_ID, qself: qself.clone(), path: path.clone() };
+        ast::InlineAsmOperand::Sym { sym }
+    } else {
+        return Ok(None);
+    }))
+}
+
+// Public for rustfmt.
+pub fn parse_asm_args<'a>(
+    p: &mut Parser<'a>,
+    sp: Span,
+    asm_macro: AsmMacro,
+) -> PResult<'a, Vec<AsmArg>> {
+    let dcx = p.dcx();
+
+    if p.token == token::Eof {
+        return Err(dcx.create_err(errors::AsmRequiresTemplate { span: sp }));
+    }
+
+    let mut args = Vec::new();
+
+    let attributes = AsmAttrVec::parse(p)?;
+    let first_template = p.parse_expr()?;
+    args.push(AsmArg {
+        span: first_template.span,
+        kind: AsmArgKind::Template(first_template),
+        attributes,
+    });
+
+    let mut allow_templates = true;
+
+    while p.token != token::Eof {
+        if !p.eat(exp!(Comma)) {
+            if allow_templates {
+                // After a template string, we always expect *only* a comma...
+                return Err(dcx.create_err(errors::AsmExpectedComma { span: p.token.span }));
+            } else {
+                // ...after that delegate to `expect` to also include the other expected tokens.
+                return Err(p.expect(exp!(Comma)).err().unwrap());
+            }
+        }
+
+        // Accept trailing commas.
+        if p.token == token::Eof {
+            break;
+        }
+
+        let attributes = AsmAttrVec::parse(p)?;
+        let span_start = p.token.span;
+
+        // Parse `clobber_abi`.
+        if p.eat_keyword(exp!(ClobberAbi)) {
+            allow_templates = false;
+
+            args.push(AsmArg {
+                kind: AsmArgKind::ClobberAbi(parse_clobber_abi(p)?),
+                span: span_start.to(p.prev_token.span),
+                attributes,
+            });
+
+            continue;
+        }
+
+        // Parse `options`.
+        if p.eat_keyword(exp!(Options)) {
+            allow_templates = false;
+
+            args.push(AsmArg {
+                kind: AsmArgKind::Options(parse_options(p, asm_macro)?),
+                span: span_start.to(p.prev_token.span),
+                attributes,
+            });
+
+            continue;
+        }
+
+        // Parse operand names.
+        let name = if p.token.is_ident() && p.look_ahead(1, |t| *t == token::Eq) {
+            let (ident, _) = p.token.ident().unwrap();
+            p.bump();
+            p.expect(exp!(Eq))?;
+            allow_templates = false;
+            Some(ident.name)
+        } else {
+            None
+        };
+
+        if let Some(op) = parse_asm_operand(p, asm_macro)? {
+            allow_templates = false;
+
+            args.push(AsmArg {
+                span: span_start.to(p.prev_token.span),
+                kind: AsmArgKind::Operand(name, op),
+                attributes,
+            });
+        } else if allow_templates {
+            let template = p.parse_expr()?;
+            // If it can't possibly expand to a string, provide diagnostics here to include other
+            // things it could have been.
+            match template.kind {
+                ast::ExprKind::Lit(token_lit)
+                    if matches!(
+                        token_lit.kind,
+                        token::LitKind::Str | token::LitKind::StrRaw(_)
+                    ) => {}
+                ast::ExprKind::MacCall(..) => {}
+                _ => {
+                    let err = dcx.create_err(errors::AsmExpectedOther {
+                        span: template.span,
+                        is_inline_asm: matches!(asm_macro, AsmMacro::Asm),
+                    });
+                    return Err(err);
+                }
+            }
+
+            args.push(AsmArg {
+                span: template.span,
+                kind: AsmArgKind::Template(template),
+                attributes,
+            });
+        } else {
+            p.unexpected_any()?
+        }
+    }
+
+    Ok(args)
+}
+
+fn parse_options<'a>(p: &mut Parser<'a>, asm_macro: AsmMacro) -> PResult<'a, Vec<AsmOption>> {
+    p.expect(exp!(OpenParen))?;
+
+    let mut asm_options = Vec::new();
+
+    while !p.eat(exp!(CloseParen)) {
+        const OPTIONS: [(ExpKeywordPair, ast::InlineAsmOptions); ast::InlineAsmOptions::COUNT] = [
+            (exp!(Pure), ast::InlineAsmOptions::PURE),
+            (exp!(Nomem), ast::InlineAsmOptions::NOMEM),
+            (exp!(Readonly), ast::InlineAsmOptions::READONLY),
+            (exp!(PreservesFlags), ast::InlineAsmOptions::PRESERVES_FLAGS),
+            (exp!(Noreturn), ast::InlineAsmOptions::NORETURN),
+            (exp!(Nostack), ast::InlineAsmOptions::NOSTACK),
+            (exp!(MayUnwind), ast::InlineAsmOptions::MAY_UNWIND),
+            (exp!(AttSyntax), ast::InlineAsmOptions::ATT_SYNTAX),
+            (exp!(Raw), ast::InlineAsmOptions::RAW),
+        ];
+
+        'blk: {
+            for (exp, options) in OPTIONS {
+                // Gives a more accurate list of expected next tokens.
+                let kw_matched = if asm_macro.is_supported_option(options) {
+                    p.eat_keyword(exp)
+                } else {
+                    p.eat_keyword_noexpect(exp.kw)
+                };
+
+                if kw_matched {
+                    let span = p.prev_token.span;
+                    let span_with_comma =
+                        if p.token == token::Comma { span.to(p.token.span) } else { span };
+
+                    asm_options.push(AsmOption { symbol: exp.kw, span, options, span_with_comma });
+                    break 'blk;
+                }
+            }
+
+            return p.unexpected_any();
+        }
+
+        // Allow trailing commas.
+        if p.eat(exp!(CloseParen)) {
+            break;
+        }
+        p.expect(exp!(Comma))?;
+    }
+
+    Ok(asm_options)
+}
+
+fn parse_clobber_abi<'a>(p: &mut Parser<'a>) -> PResult<'a, Vec<(Symbol, Span)>> {
+    p.expect(exp!(OpenParen))?;
+
+    if p.eat(exp!(CloseParen)) {
+        return Err(p.dcx().create_err(errors::NonABI { span: p.token.span }));
+    }
+
+    let mut new_abis = Vec::new();
+    while !p.eat(exp!(CloseParen)) {
+        match p.parse_str_lit() {
+            Ok(str_lit) => {
+                new_abis.push((str_lit.symbol_unescaped, str_lit.span));
+            }
+            Err(opt_lit) => {
+                let span = opt_lit.map_or(p.token.span, |lit| lit.span);
+                return Err(p.dcx().create_err(errors::AsmExpectedStringLiteral { span }));
+            }
+        };
+
+        // Allow trailing commas
+        if p.eat(exp!(CloseParen)) {
+            break;
+        }
+        p.expect(exp!(Comma))?;
+    }
+
+    Ok(new_abis)
+}
+
+fn parse_reg<'a>(p: &mut Parser<'a>) -> PResult<'a, ast::InlineAsmRegOrRegClass> {
+    p.expect(exp!(OpenParen))?;
+    let result = match p.token.uninterpolate().kind {
+        token::Ident(name, IdentIsRaw::No) => ast::InlineAsmRegOrRegClass::RegClass(name),
+        token::Literal(token::Lit { kind: token::LitKind::Str, symbol, suffix: _ }) => {
+            ast::InlineAsmRegOrRegClass::Reg(symbol)
+        }
+        _ => {
+            return Err(p.dcx().create_err(errors::ExpectedRegisterClassOrExplicitRegister {
+                span: p.token.span,
+            }));
+        }
+    };
+    p.bump();
+    p.expect(exp!(CloseParen))?;
+    Ok(result)
+}
diff --git a/compiler/rustc_parse/src/parser/mod.rs b/compiler/rustc_parse/src/parser/mod.rs
index 968376678f3..b2e90251367 100644
--- a/compiler/rustc_parse/src/parser/mod.rs
+++ b/compiler/rustc_parse/src/parser/mod.rs
@@ -1,3 +1,4 @@
+pub mod asm;
 pub mod attr;
 mod attr_wrapper;
 mod diagnostics;