Add support for specifying multiple clobber_abi in asm!

Allow multiple clobber_abi in asm

Update docs
Fix aarch64 test
Combine abis
Emit duplicate ABI error, empty ABI list error
multiple clobber_abi

Author: asquared31415

compiler/rustc_ast/src/ast.rs

@@ -2058,7 +2058,7 @@ pub struct InlineAsm {
     pub template: Vec<InlineAsmTemplatePiece>,
     pub template_strs: Box<[(Symbol, Option<Symbol>, Span)]>,
     pub operands: Vec<(InlineAsmOperand, Span)>,
-    pub clobber_abi: Option<(Symbol, Span)>,
+    pub clobber_abis: Vec<(Symbol, Span)>,
     pub options: InlineAsmOptions,
     pub line_spans: Vec<Span>,
 }
@@ -2715,7 +2715,7 @@ pub enum ItemKind {
     /// E.g., `extern {}` or `extern "C" {}`.
     ForeignMod(ForeignMod),
     /// Module-level inline assembly (from `global_asm!()`).
-    GlobalAsm(InlineAsm),
+    GlobalAsm(Box<InlineAsm>),
     /// A type alias (`type`).
     ///
     /// E.g., `type Foo = Bar<u8>;`.

compiler/rustc_ast_lowering/src/asm.rs

@@ -2,6 +2,7 @@ use super::LoweringContext;
 
 use rustc_ast::*;
 use rustc_data_structures::fx::FxHashMap;
+use rustc_data_structures::stable_set::FxHashSet;
 use rustc_errors::struct_span_err;
 use rustc_hir as hir;
 use rustc_session::parse::feature_err;
@@ -49,22 +50,47 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
                 .emit();
         }
 
-        let mut clobber_abi = None;
+        let mut clobber_abis = FxHashMap::default();
         if let Some(asm_arch) = asm_arch {
-            if let Some((abi_name, abi_span)) = asm.clobber_abi {
-                match asm::InlineAsmClobberAbi::parse(asm_arch, &self.sess.target, abi_name) {
-                    Ok(abi) => clobber_abi = Some((abi, abi_span)),
+            for (abi_name, abi_span) in &asm.clobber_abis {
+                match asm::InlineAsmClobberAbi::parse(asm_arch, &self.sess.target, *abi_name) {
+                    Ok(abi) => {
+                        // If the abi was already in the list, emit an error
+                        match clobber_abis.get(&abi) {
+                            Some((prev_name, prev_sp)) => {
+                                let mut err = self.sess.struct_span_err(
+                                    *abi_span,
+                                    &format!("`{}` ABI specified multiple times", prev_name),
+                                );
+                                err.span_label(*prev_sp, "previously specified here");
+
+                                // Multiple different abi names may actually be the same ABI
+                                // If the specified ABIs are not the same name, alert the user that they resolve to the same ABI
+                                let source_map = self.sess.source_map();
+                                if source_map.span_to_snippet(*prev_sp)
+                                    != source_map.span_to_snippet(*abi_span)
+                                {
+                                    err.note("these ABIs are equivalent on the current target");
+                                }
+
+                                err.emit();
+                            }
+                            None => {
+                                clobber_abis.insert(abi, (abi_name, *abi_span));
+                            }
+                        }
+                    }
                     Err(&[]) => {
                         self.sess
                             .struct_span_err(
-                                abi_span,
+                                *abi_span,
                                 "`clobber_abi` is not supported on this target",
                             )
                             .emit();
                     }
                     Err(supported_abis) => {
                         let mut err =
-                            self.sess.struct_span_err(abi_span, "invalid ABI for `clobber_abi`");
+                            self.sess.struct_span_err(*abi_span, "invalid ABI for `clobber_abi`");
                         let mut abis = format!("`{}`", supported_abis[0]);
                         for m in &supported_abis[1..] {
                             let _ = write!(abis, ", `{}`", m);
@@ -348,8 +374,14 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
 
         // If a clobber_abi is specified, add the necessary clobbers to the
         // operands list.
-        if let Some((abi, abi_span)) = clobber_abi {
+        let mut clobbered = FxHashSet::default();
+        for (abi, (_, abi_span)) in clobber_abis {
             for &clobber in abi.clobbered_regs() {
+                // Don't emit a clobber for a register already clobbered
+                if clobbered.contains(&clobber) {
+                    continue;
+                }
+
                 let mut output_used = false;
                 clobber.overlapping_regs(|reg| {
                     if used_output_regs.contains_key(&reg) {
@@ -366,6 +398,7 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
                         },
                         self.lower_span(abi_span),
                     ));
+                    clobbered.insert(clobber);
                 }
             }
         }

compiler/rustc_ast_pretty/src/pprust/state.rs

@@ -2235,8 +2235,8 @@ impl<'a> State<'a> {
 
         let mut args = vec![AsmArg::Template(InlineAsmTemplatePiece::to_string(&asm.template))];
         args.extend(asm.operands.iter().map(|(o, _)| AsmArg::Operand(o)));
-        if let Some((abi, _)) = asm.clobber_abi {
-            args.push(AsmArg::ClobberAbi(abi));
+        for (abi, _) in &asm.clobber_abis {
+            args.push(AsmArg::ClobberAbi(*abi));
         }
         if !asm.options.is_empty() {
             args.push(AsmArg::Options(asm.options));

compiler/rustc_builtin_macros/src/asm.rs

@@ -19,7 +19,7 @@ struct AsmArgs {
     operands: Vec<(ast::InlineAsmOperand, Span)>,
     named_args: FxHashMap<Symbol, usize>,
     reg_args: FxHashSet<usize>,
-    clobber_abi: Option<(Symbol, Span)>,
+    clobber_abis: Vec<(Symbol, Span)>,
     options: ast::InlineAsmOptions,
     options_spans: Vec<Span>,
 }
@@ -64,7 +64,7 @@ fn parse_args<'a>(
         operands: vec![],
         named_args: FxHashMap::default(),
         reg_args: FxHashSet::default(),
-        clobber_abi: None,
+        clobber_abis: Vec::new(),
         options: ast::InlineAsmOptions::empty(),
         options_spans: vec![],
     };
@@ -210,9 +210,9 @@ fn parse_args<'a>(
                 .span_labels(args.options_spans.clone(), "previous options")
                 .span_label(span, "argument")
                 .emit();
-        } else if let Some((_, abi_span)) = args.clobber_abi {
+        } else if let Some((_, abi_span)) = args.clobber_abis.last() {
             ecx.struct_span_err(span, "arguments are not allowed after clobber_abi")
-                .span_label(abi_span, "clobber_abi")
+                .span_label(*abi_span, "clobber_abi")
                 .span_label(span, "argument")
                 .emit();
         }
@@ -322,10 +322,13 @@ fn parse_args<'a>(
         // Bail out now since this is likely to confuse MIR
         return Err(err);
     }
-    if let Some((_, abi_span)) = args.clobber_abi {
+
+    if args.clobber_abis.len() > 0 {
         if is_global_asm {
-            let err =
-                ecx.struct_span_err(abi_span, "`clobber_abi` cannot be used with `global_asm!`");
+            let err = ecx.struct_span_err(
+                args.clobber_abis.iter().map(|(_, span)| *span).collect::<Vec<Span>>(),
+                "`clobber_abi` cannot be used with `global_asm!`",
+            );
 
             // Bail out now since this is likely to confuse later stages
             return Err(err);
@@ -335,7 +338,10 @@ fn parse_args<'a>(
                 regclass_outputs.clone(),
                 "asm with `clobber_abi` must specify explicit registers for outputs",
             )
-            .span_label(abi_span, "clobber_abi")
+            .span_labels(
+                args.clobber_abis.iter().map(|(_, span)| *span).collect::<Vec<Span>>(),
+                "clobber_abi",
+            )
             .span_labels(regclass_outputs, "generic outputs")
             .emit();
         }
@@ -439,37 +445,61 @@ fn parse_clobber_abi<'a>(
 
     p.expect(&token::OpenDelim(token::DelimToken::Paren))?;
 
-    let clobber_abi = match p.parse_str_lit() {
-        Ok(str_lit) => str_lit.symbol_unescaped,
-        Err(opt_lit) => {
-            let span = opt_lit.map_or(p.token.span, |lit| lit.span);
-            let mut err = p.sess.span_diagnostic.struct_span_err(span, "expected string literal");
-            err.span_label(span, "not a string literal");
-            return Err(err);
-        }
-    };
+    if p.eat(&token::CloseDelim(token::DelimToken::Paren)) {
+        let err = p.sess.span_diagnostic.struct_span_err(
+            p.token.span,
+            "at least one abi must be provided as an argument to `clobber_abi`",
+        );
+        return Err(err);
+    }
 
-    p.expect(&token::CloseDelim(token::DelimToken::Paren))?;
+    let mut new_abis = Vec::new();
+    loop {
+        match p.parse_str_lit() {
+            Ok(str_lit) => {
+                new_abis.push((str_lit.symbol_unescaped, str_lit.span));
+            }
+            Err(opt_lit) => {
+                // If the non-string literal is a closing paren then it's the end of the list and is fine
+                if p.eat(&token::CloseDelim(token::DelimToken::Paren)) {
+                    break;
+                }
+                let span = opt_lit.map_or(p.token.span, |lit| lit.span);
+                let mut err =
+                    p.sess.span_diagnostic.struct_span_err(span, "expected string literal");
+                err.span_label(span, "not a string literal");
+                return Err(err);
+            }
+        };
 
-    let new_span = span_start.to(p.prev_token.span);
+        // Allow trailing commas
+        if p.eat(&token::CloseDelim(token::DelimToken::Paren)) {
+            break;
+        }
+        p.expect(&token::Comma)?;
+    }
 
-    if let Some((_, prev_span)) = args.clobber_abi {
-        let mut err = p
-            .sess
-            .span_diagnostic
-            .struct_span_err(new_span, "clobber_abi specified multiple times");
-        err.span_label(prev_span, "clobber_abi previously specified here");
-        return Err(err);
-    } else if !args.options_spans.is_empty() {
+    let full_span = span_start.to(p.prev_token.span);
+
+    if !args.options_spans.is_empty() {
         let mut err = p
             .sess
             .span_diagnostic
-            .struct_span_err(new_span, "clobber_abi is not allowed after options");
+            .struct_span_err(full_span, "clobber_abi is not allowed after options");
         err.span_labels(args.options_spans.clone(), "options");
         return Err(err);
     }
 
-    args.clobber_abi = Some((clobber_abi, new_span));
+    match &new_abis[..] {
+        // should have errored above during parsing
+        [] => unreachable!(),
+        [(abi, _span)] => args.clobber_abis.push((*abi, full_span)),
+        [abis @ ..] => {
+            for (abi, span) in abis {
+                args.clobber_abis.push((*abi, *span));
+            }
+        }
+    }
 
     Ok(())
 }
@@ -770,7 +800,7 @@ fn expand_preparsed_asm(ecx: &mut ExtCtxt<'_>, args: AsmArgs) -> Option<ast::Inl
         template,
         template_strs: template_strs.into_boxed_slice(),
         operands: args.operands,
-        clobber_abi: args.clobber_abi,
+        clobber_abis: args.clobber_abis,
         options: args.options,
         line_spans,
     })
@@ -815,7 +845,7 @@ pub fn expand_global_asm<'cx>(
                     ident: Ident::empty(),
                     attrs: Vec::new(),
                     id: ast::DUMMY_NODE_ID,
-                    kind: ast::ItemKind::GlobalAsm(inline_asm),
+                    kind: ast::ItemKind::GlobalAsm(Box::new(inline_asm)),
                     vis: ast::Visibility {
                         span: sp.shrink_to_lo(),
                         kind: ast::VisibilityKind::Inherited,

src/doc/unstable-book/src/library-features/asm.md

@@ -319,7 +319,7 @@ fn call_foo(arg: i32) -> i32 {
 
 Note that the `fn` or `static` item does not need to be public or `#[no_mangle]`: the compiler will automatically insert the appropriate mangled symbol name into the assembly code.
 
-By default, `asm!` assumes that any register not specified as an output will have its contents preserved by the assembly code. The [`clobber_abi`](#abi-clobbers) argument to `asm!` tells the compiler to automatically insert the necessary clobber operands according to the given calling convention ABI: any register which is not fully preserved in that ABI will be treated as clobbered.
+By default, `asm!` assumes that any register not specified as an output will have its contents preserved by the assembly code. The [`clobber_abi`](#abi-clobbers) argument to `asm!` tells the compiler to automatically insert the necessary clobber operands according to the given calling convention ABI: any register which is not fully preserved in that ABI will be treated as clobbered.  Multiple `clobber_abi` arguments may be provided and all clobbers from all specified ABIs will be inserted.
 
 ## Register template modifiers
 
@@ -453,10 +453,10 @@ reg_spec := <register class> / "<explicit register>"
 operand_expr := expr / "_" / expr "=>" expr / expr "=>" "_"
 reg_operand := dir_spec "(" reg_spec ")" operand_expr
 operand := reg_operand / "const" const_expr / "sym" path
-clobber_abi := "clobber_abi(" <abi> ")"
+clobber_abi := "clobber_abi(" <abi> *["," <abi>] [","] ")"
 option := "pure" / "nomem" / "readonly" / "preserves_flags" / "noreturn" / "nostack" / "att_syntax" / "raw"
 options := "options(" option *["," option] [","] ")"
-asm := "asm!(" format_string *("," format_string) *("," [ident "="] operand) ["," clobber_abi] *("," options) [","] ")"
+asm := "asm!(" format_string *("," format_string) *("," [ident "="] operand) *("," clobber_abi) *("," options) [","] ")"
 ```
 
 Inline assembly is currently supported on the following architectures:
@@ -799,6 +799,8 @@ As stated in the previous section, passing an input value smaller than the regis
 
 The `clobber_abi` keyword can be used to apply a default set of clobbers to an `asm` block. This will automatically insert the necessary clobber constraints as needed for calling a function with a particular calling convention: if the calling convention does not fully preserve the value of a register across a call then a `lateout("reg") _` is implicitly added to the operands list.
 
+`clobber_abi` may be specified any number of times. It will insert a clobber for all unique registers in the union of all specified calling conventions.
+
 Generic register class outputs are disallowed by the compiler when `clobber_abi` is used: all outputs must specify an explicit register. Explicit register outputs have precedence over the implicit clobbers inserted by `clobber_abi`: a clobber will only be inserted for a register if that register is not used as an output.
 The following ABIs can be used with `clobber_abi`:
 

src/test/ui/asm/aarch64/parse-error.rs

@@ -51,7 +51,6 @@ fn main() {
         asm!("{}", options(), clobber_abi("C"), const foo);
         //~^ ERROR clobber_abi is not allowed after options
         asm!("", clobber_abi("C"), clobber_abi("C"));
-        //~^ ERROR clobber_abi specified multiple times
         asm!("{a}", a = const foo, a = const bar);
         //~^ ERROR duplicate argument named `a`
         //~^^ ERROR argument never used
@@ -121,7 +120,7 @@ global_asm!("", options(), clobber_abi("C"));
 global_asm!("{}", options(), clobber_abi("C"), const FOO);
 //~^ ERROR clobber_abi is not allowed after options
 global_asm!("", clobber_abi("C"), clobber_abi("C"));
-//~^ ERROR clobber_abi specified multiple times
+//~^ ERROR `clobber_abi` cannot be used with `global_asm!`
 global_asm!("{a}", a = const FOO, a = const BAR);
 //~^ ERROR duplicate argument named `a`
 //~^^ ERROR argument never used