Rollup merge of #89316 - asquared31415:multiple-clobber-abi, r=Amanieu

Add support for specifying multiple clobber_abi in `asm!`

r? `@Amanieu`
cc #72016
`@rustbot` label: +A-inline-assembly +F-asm

Author: fee1-dead

compiler/rustc_ast/src/ast.rs

@@ -2056,7 +2056,7 @@ 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>,
 }
@@ -2705,7 +2705,7 @@ 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_span::{Span, Symbol};
@@ -27,11 +28,13 @@ 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 {
+            for &(abi_name, abi_span) in &asm.clobber_abis {
                 match asm::InlineAsmClobberAbi::parse(asm_arch, &self.sess.target, abi_name) {
-                    Ok(abi) => clobber_abi = Some((abi, abi_span)),
+                    Ok(abi) => {
+                        clobber_abis.insert(abi, abi_span);
+                    }
                     Err(&[]) => {
                         self.sess
                             .struct_span_err(
@@ -368,8 +371,14 @@ 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) {
@@ -386,6 +395,7 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
                         },
                         self.lower_span(abi_span),
                     ));
+                    clobbered.insert(clobber);
                 }
             }
         }

compiler/rustc_ast_pretty/src/pprust/state.rs

@@ -2199,8 +2199,8 @@ 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![],
     };
@@ -210,7 +210,7 @@ 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(span, "argument")
@@ -322,10 +322,12 @@ 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(|(_, sp)| *sp).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 +337,10 @@ 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(|(_, sp)| *sp).collect::<Vec<Span>>(),
+                "clobber_abi",
+            )
             .span_labels(regclass_outputs, "generic outputs")
             .emit();
         }
@@ -453,14 +458,7 @@ fn parse_clobber_abi<'a>(
 
     let new_span = span_start.to(p.prev_token.span);
 
-    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() {
+    if !args.options_spans.is_empty() {
         let mut err = p
             .sess
             .span_diagnostic
@@ -469,7 +467,7 @@ fn parse_clobber_abi<'a>(
         return Err(err);
     }
 
-    args.clobber_abi = Some((clobber_abi, new_span));
+    args.clobber_abis.push((clobber_abi, new_span));
 
     Ok(())
 }
@@ -770,7 +768,7 @@ 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 +813,7 @@ pub fn expand_global_asm<'cx>(
                     ident: Ident::invalid(),
                     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
 
@@ -456,7 +456,7 @@ operand := reg_operand / "const" const_expr / "sym" path
 clobber_abi := "clobber_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/multiple-clobber-abi.rs

@@ -0,0 +1,34 @@
+// run-pass
+// needs-asm-support
+// only-x86_64
+
+// Checks that multiple clobber_abi options can be used
+
+#![feature(asm)]
+
+extern "sysv64" fn foo(x: i32) -> i32 {
+    x + 16
+}
+
+extern "win64" fn bar(x: i32) -> i32 {
+    x / 2
+}
+
+fn main() {
+    let x = 8;
+    let y: i32;
+    // call `foo` with `x` as the input, and then `bar` with the output of `foo`
+    // and output that to `y`
+    unsafe {
+        asm!(
+            "call {}; mov rcx, rax; call {}",
+            sym foo,
+            sym bar,
+            in("rdi") x,
+            out("rax") y,
+            clobber_abi("sysv64"),
+            clobber_abi("win64")
+        );
+    }
+    assert_eq!((x, y), (8, 12));
+}

src/test/ui/asm/x86_64/bad-options.rs

@@ -21,6 +21,8 @@ fn main() {
         //~^ ERROR invalid ABI for `clobber_abi`
         asm!("{}", out(reg) foo, clobber_abi("C"));
         //~^ ERROR asm with `clobber_abi` must specify explicit registers for outputs
+        asm!("{}", out(reg) foo, clobber_abi("C"), clobber_abi("C"));
+        //~^ ERROR asm with `clobber_abi` must specify explicit registers for outputs
         asm!("", out("eax") foo, clobber_abi("C"));
     }
 }

src/test/ui/asm/x86_64/bad-options.stderr

@@ -36,38 +36,47 @@ LL |         asm!("{}", out(reg) foo, clobber_abi("C"));
    |                    |
    |                    generic outputs
 
+error: asm with `clobber_abi` must specify explicit registers for outputs
+  --> $DIR/bad-options.rs:24:20
+   |
+LL |         asm!("{}", out(reg) foo, clobber_abi("C"), clobber_abi("C"));
+   |                    ^^^^^^^^^^^^  ----------------  ---------------- clobber_abi
+   |                    |             |
+   |                    |             clobber_abi
+   |                    generic outputs
+
 error: expected one of `)`, `att_syntax`, or `raw`, found `nomem`
-  --> $DIR/bad-options.rs:28:25
+  --> $DIR/bad-options.rs:30:25
    |
 LL | global_asm!("", options(nomem));
    |                         ^^^^^ expected one of `)`, `att_syntax`, or `raw`
 
 error: expected one of `)`, `att_syntax`, or `raw`, found `readonly`
-  --> $DIR/bad-options.rs:30:25
+  --> $DIR/bad-options.rs:32:25
    |
 LL | global_asm!("", options(readonly));
    |                         ^^^^^^^^ expected one of `)`, `att_syntax`, or `raw`
 
 error: expected one of `)`, `att_syntax`, or `raw`, found `noreturn`
-  --> $DIR/bad-options.rs:32:25
+  --> $DIR/bad-options.rs:34:25
    |
 LL | global_asm!("", options(noreturn));
    |                         ^^^^^^^^ expected one of `)`, `att_syntax`, or `raw`
 
 error: expected one of `)`, `att_syntax`, or `raw`, found `pure`
-  --> $DIR/bad-options.rs:34:25
+  --> $DIR/bad-options.rs:36:25
    |
 LL | global_asm!("", options(pure));
    |                         ^^^^ expected one of `)`, `att_syntax`, or `raw`
 
 error: expected one of `)`, `att_syntax`, or `raw`, found `nostack`
-  --> $DIR/bad-options.rs:36:25
+  --> $DIR/bad-options.rs:38:25
    |
 LL | global_asm!("", options(nostack));
    |                         ^^^^^^^ expected one of `)`, `att_syntax`, or `raw`
 
 error: expected one of `)`, `att_syntax`, or `raw`, found `preserves_flags`
-  --> $DIR/bad-options.rs:38:25
+  --> $DIR/bad-options.rs:40:25
    |
 LL | global_asm!("", options(preserves_flags));
    |                         ^^^^^^^^^^^^^^^ expected one of `)`, `att_syntax`, or `raw`
@@ -80,5 +89,5 @@ LL |         asm!("", clobber_abi("foo"));
    |
    = note: the following ABIs are supported on this target: `C`, `system`, `efiapi`, `win64`, `sysv64`
 
-error: aborting due to 13 previous errors
+error: aborting due to 14 previous errors
 

src/test/ui/asm/x86_64/parse-error.rs

@@ -50,8 +50,6 @@ fn main() {
         //~^ ERROR clobber_abi is not allowed after options
         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 +119,7 @@ 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