Rollup merge of #120502 - clubby789:remove-ffi-returns-twice, r=compiler-errors

Remove `ffi_returns_twice` feature

The [tracking issue](https://github.com/rust-lang/rust/issues/58314) and [RFC](https://github.com/rust-lang/rfcs/pull/2633) have been closed for a couple of years.

There is also an attribute gate in R-A which should be removed if this lands.

20 files changed, 19 insertions, 120 deletions

diff --git a/compiler/rustc_codegen_gcc/src/attributes.rs b/compiler/rustc_codegen_gcc/src/attributes.rs
index 9f361d36886..142f86b003d 100644
--- a/compiler/rustc_codegen_gcc/src/attributes.rs
+++ b/compiler/rustc_codegen_gcc/src/attributes.rs
@@ -62,9 +62,6 @@ pub fn from_fn_attrs<'gcc, 'tcx>(
         if codegen_fn_attrs.flags.contains(CodegenFnAttrFlags::COLD) {
             func.add_attribute(FnAttribute::Cold);
         }
-        if codegen_fn_attrs.flags.contains(CodegenFnAttrFlags::FFI_RETURNS_TWICE) {
-            func.add_attribute(FnAttribute::ReturnsTwice);
-        }
         if codegen_fn_attrs.flags.contains(CodegenFnAttrFlags::FFI_PURE) {
             func.add_attribute(FnAttribute::Pure);
         }
diff --git a/compiler/rustc_codegen_llvm/src/attributes.rs b/compiler/rustc_codegen_llvm/src/attributes.rs
index 0a7ea599431..07c83f1aa08 100644
--- a/compiler/rustc_codegen_llvm/src/attributes.rs
+++ b/compiler/rustc_codegen_llvm/src/attributes.rs
@@ -356,9 +356,6 @@ pub fn from_fn_attrs<'ll, 'tcx>(
     if codegen_fn_attrs.flags.contains(CodegenFnAttrFlags::COLD) {
         to_add.push(AttributeKind::Cold.create_attr(cx.llcx));
     }
-    if codegen_fn_attrs.flags.contains(CodegenFnAttrFlags::FFI_RETURNS_TWICE) {
-        to_add.push(AttributeKind::ReturnsTwice.create_attr(cx.llcx));
-    }
     if codegen_fn_attrs.flags.contains(CodegenFnAttrFlags::FFI_PURE) {
         to_add.push(MemoryEffects::ReadOnly.create_attr(cx.llcx));
     }
diff --git a/compiler/rustc_codegen_llvm/src/llvm/ffi.rs b/compiler/rustc_codegen_llvm/src/llvm/ffi.rs
index 4ad44a42738..d0044086c61 100644
--- a/compiler/rustc_codegen_llvm/src/llvm/ffi.rs
+++ b/compiler/rustc_codegen_llvm/src/llvm/ffi.rs
@@ -184,7 +184,6 @@ pub enum AttributeKind {
     SanitizeMemory = 22,
     NonLazyBind = 23,
     OptimizeNone = 24,
-    ReturnsTwice = 25,
     ReadNone = 26,
     SanitizeHWAddress = 28,
     WillReturn = 29,
diff --git a/compiler/rustc_codegen_ssa/src/codegen_attrs.rs b/compiler/rustc_codegen_ssa/src/codegen_attrs.rs
index 47b1b080119..b387d0b2258 100644
--- a/compiler/rustc_codegen_ssa/src/codegen_attrs.rs
+++ b/compiler/rustc_codegen_ssa/src/codegen_attrs.rs
@@ -103,9 +103,6 @@ fn codegen_fn_attrs(tcx: TyCtxt<'_>, did: LocalDefId) -> CodegenFnAttrs {
         match name {
             sym::cold => codegen_fn_attrs.flags |= CodegenFnAttrFlags::COLD,
             sym::rustc_allocator => codegen_fn_attrs.flags |= CodegenFnAttrFlags::ALLOCATOR,
-            sym::ffi_returns_twice => {
-                codegen_fn_attrs.flags |= CodegenFnAttrFlags::FFI_RETURNS_TWICE
-            }
             sym::ffi_pure => codegen_fn_attrs.flags |= CodegenFnAttrFlags::FFI_PURE,
             sym::ffi_const => codegen_fn_attrs.flags |= CodegenFnAttrFlags::FFI_CONST,
             sym::rustc_nounwind => codegen_fn_attrs.flags |= CodegenFnAttrFlags::NEVER_UNWIND,
diff --git a/compiler/rustc_error_codes/src/error_codes/E0724.md b/compiler/rustc_error_codes/src/error_codes/E0724.md
index 70578acbe0d..bcefd0a7479 100644
--- a/compiler/rustc_error_codes/src/error_codes/E0724.md
+++ b/compiler/rustc_error_codes/src/error_codes/E0724.md
@@ -1,9 +1,12 @@
+#### Note: this error code is no longer emitted by the compiler.
+
+
 `#[ffi_returns_twice]` was used on something other than a foreign function
 declaration.
 
 Erroneous code example:
 
-```compile_fail,E0724
+```compile_fail
 #![feature(ffi_returns_twice)]
 #![crate_type = "lib"]
 
@@ -15,7 +18,7 @@ pub fn foo() {}
 For example, we might correct the previous example by declaring
 the function inside of an `extern` block.
 
-```
+```compile_fail
 #![feature(ffi_returns_twice)]
 
 extern "C" {
diff --git a/compiler/rustc_feature/src/builtin_attrs.rs b/compiler/rustc_feature/src/builtin_attrs.rs
index 68b6f69854d..019cc1c847e 100644
--- a/compiler/rustc_feature/src/builtin_attrs.rs
+++ b/compiler/rustc_feature/src/builtin_attrs.rs
@@ -440,9 +440,6 @@ pub const BUILTIN_ATTRIBUTES: &[BuiltinAttribute] = &[
         experimental!(optimize),
     ),
 
-    gated!(
-        ffi_returns_twice, Normal, template!(Word), WarnFollowing, experimental!(ffi_returns_twice)
-    ),
     gated!(ffi_pure, Normal, template!(Word), WarnFollowing, experimental!(ffi_pure)),
     gated!(ffi_const, Normal, template!(Word), WarnFollowing, experimental!(ffi_const)),
     gated!(
diff --git a/compiler/rustc_feature/src/removed.rs b/compiler/rustc_feature/src/removed.rs
index 85fcf6a9994..040892df4c3 100644
--- a/compiler/rustc_feature/src/removed.rs
+++ b/compiler/rustc_feature/src/removed.rs
@@ -97,6 +97,9 @@ declare_features! (
     /// Allows `#[doc(include = "some-file")]`.
     (removed, external_doc, "1.54.0", Some(44732),
      Some("use #[doc = include_str!(\"filename\")] instead, which handles macro invocations")),
+    /// Allows using `#[ffi_returns_twice]` on foreign functions.
+    (removed, ffi_returns_twice, "CURRENT_RUSTC_VERSION", Some(58314),
+     Some("being investigated by the ffi-unwind project group")),
     /// Allows generators to be cloned.
     (removed, generator_clone, "1.65.0", Some(95360), Some("renamed to `coroutine_clone`")),
     /// Allows defining generators.
diff --git a/compiler/rustc_feature/src/unstable.rs b/compiler/rustc_feature/src/unstable.rs
index d00621d8254..1fb91ff8bbc 100644
--- a/compiler/rustc_feature/src/unstable.rs
+++ b/compiler/rustc_feature/src/unstable.rs
@@ -465,8 +465,6 @@ declare_features! (
     (unstable, ffi_const, "1.45.0", Some(58328)),
     /// Allows the use of `#[ffi_pure]` on foreign functions.
     (unstable, ffi_pure, "1.45.0", Some(58329)),
-    /// Allows using `#[ffi_returns_twice]` on foreign functions.
-    (unstable, ffi_returns_twice, "1.34.0", Some(58314)),
     /// Allows using `#[repr(align(...))]` on function items
     (unstable, fn_align, "1.53.0", Some(82232)),
     /// Support delegating implementation of functions to other already implemented functions.
diff --git a/compiler/rustc_llvm/llvm-wrapper/LLVMWrapper.h b/compiler/rustc_llvm/llvm-wrapper/LLVMWrapper.h
index 5bfffc5d911..6d578c97f3f 100644
--- a/compiler/rustc_llvm/llvm-wrapper/LLVMWrapper.h
+++ b/compiler/rustc_llvm/llvm-wrapper/LLVMWrapper.h
@@ -76,7 +76,6 @@ enum LLVMRustAttribute {
   SanitizeMemory = 22,
   NonLazyBind = 23,
   OptimizeNone = 24,
-  ReturnsTwice = 25,
   ReadNone = 26,
   SanitizeHWAddress = 28,
   WillReturn = 29,
diff --git a/compiler/rustc_llvm/llvm-wrapper/RustWrapper.cpp b/compiler/rustc_llvm/llvm-wrapper/RustWrapper.cpp
index 0df7b7eed11..a2dfebec594 100644
--- a/compiler/rustc_llvm/llvm-wrapper/RustWrapper.cpp
+++ b/compiler/rustc_llvm/llvm-wrapper/RustWrapper.cpp
@@ -250,8 +250,6 @@ static Attribute::AttrKind fromRust(LLVMRustAttribute Kind) {
     return Attribute::NonLazyBind;
   case OptimizeNone:
     return Attribute::OptimizeNone;
-  case ReturnsTwice:
-    return Attribute::ReturnsTwice;
   case ReadNone:
     return Attribute::ReadNone;
   case SanitizeHWAddress:
diff --git a/compiler/rustc_middle/src/middle/codegen_fn_attrs.rs b/compiler/rustc_middle/src/middle/codegen_fn_attrs.rs
index e11c9371118..7d6d39a2a8a 100644
--- a/compiler/rustc_middle/src/middle/codegen_fn_attrs.rs
+++ b/compiler/rustc_middle/src/middle/codegen_fn_attrs.rs
@@ -74,35 +74,32 @@ bitflags! {
         /// `#[used]`: indicates that LLVM can't eliminate this function (but the
         /// linker can!).
         const USED                      = 1 << 9;
-        /// `#[ffi_returns_twice]`, indicates that an extern function can return
-        /// multiple times
-        const FFI_RETURNS_TWICE         = 1 << 10;
         /// `#[track_caller]`: allow access to the caller location
-        const TRACK_CALLER              = 1 << 11;
+        const TRACK_CALLER              = 1 << 10;
         /// #[ffi_pure]: applies clang's `pure` attribute to a foreign function
         /// declaration.
-        const FFI_PURE                  = 1 << 12;
+        const FFI_PURE                  = 1 << 11;
         /// #[ffi_const]: applies clang's `const` attribute to a foreign function
         /// declaration.
-        const FFI_CONST                 = 1 << 13;
+        const FFI_CONST                 = 1 << 12;
         /// #[cmse_nonsecure_entry]: with a TrustZone-M extension, declare a
         /// function as an entry function from Non-Secure code.
-        const CMSE_NONSECURE_ENTRY      = 1 << 14;
+        const CMSE_NONSECURE_ENTRY      = 1 << 13;
         /// `#[coverage(off)]`: indicates that the function should be ignored by
         /// the MIR `InstrumentCoverage` pass and not added to the coverage map
         /// during codegen.
-        const NO_COVERAGE               = 1 << 15;
+        const NO_COVERAGE               = 1 << 14;
         /// `#[used(linker)]`:
         /// indicates that neither LLVM nor the linker will eliminate this function.
-        const USED_LINKER               = 1 << 16;
+        const USED_LINKER               = 1 << 15;
         /// `#[rustc_deallocator]`: a hint to LLVM that the function only deallocates memory.
-        const DEALLOCATOR               = 1 << 17;
+        const DEALLOCATOR               = 1 << 16;
         /// `#[rustc_reallocator]`: a hint to LLVM that the function only reallocates memory.
-        const REALLOCATOR               = 1 << 18;
+        const REALLOCATOR               = 1 << 17;
         /// `#[rustc_allocator_zeroed]`: a hint to LLVM that the function only allocates zeroed memory.
-        const ALLOCATOR_ZEROED          = 1 << 19;
+        const ALLOCATOR_ZEROED          = 1 << 18;
         /// `#[no_builtins]`: indicates that disable implicit builtin knowledge of functions for the function.
-        const NO_BUILTINS               = 1 << 20;
+        const NO_BUILTINS               = 1 << 19;
     }
 }
 rustc_data_structures::external_bitflags_debug! { CodegenFnAttrFlags }
diff --git a/compiler/rustc_passes/messages.ftl b/compiler/rustc_passes/messages.ftl
index d41cc724408..648ef9d51de 100644
--- a/compiler/rustc_passes/messages.ftl
+++ b/compiler/rustc_passes/messages.ftl
@@ -323,9 +323,6 @@ passes_ffi_const_invalid_target =
 passes_ffi_pure_invalid_target =
     `#[ffi_pure]` may only be used on foreign functions
 
-passes_ffi_returns_twice_invalid_target =
-    `#[ffi_returns_twice]` may only be used on foreign functions
-
 passes_has_incoherent_inherent_impl =
     `rustc_has_incoherent_inherent_impls` attribute should be applied to types or traits.
     .label = only adts, extern types and traits are supported
diff --git a/compiler/rustc_passes/src/check_attr.rs b/compiler/rustc_passes/src/check_attr.rs
index 0f0027db01d..e652c79d851 100644
--- a/compiler/rustc_passes/src/check_attr.rs
+++ b/compiler/rustc_passes/src/check_attr.rs
@@ -192,7 +192,6 @@ impl<'tcx> CheckAttrVisitor<'tcx> {
                 }
                 sym::ffi_pure => self.check_ffi_pure(attr.span, attrs, target),
                 sym::ffi_const => self.check_ffi_const(attr.span, target),
-                sym::ffi_returns_twice => self.check_ffi_returns_twice(attr.span, target),
                 sym::rustc_const_unstable
                 | sym::rustc_const_stable
                 | sym::unstable
@@ -1309,15 +1308,6 @@ impl<'tcx> CheckAttrVisitor<'tcx> {
         }
     }
 
-    fn check_ffi_returns_twice(&self, attr_span: Span, target: Target) -> bool {
-        if target == Target::ForeignFn {
-            true
-        } else {
-            self.dcx().emit_err(errors::FfiReturnsTwiceInvalidTarget { attr_span });
-            false
-        }
-    }
-
     /// Warns against some misuses of `#[must_use]`
     fn check_must_use(&self, hir_id: HirId, attr: &Attribute, target: Target) -> bool {
         if !matches!(
diff --git a/compiler/rustc_passes/src/errors.rs b/compiler/rustc_passes/src/errors.rs
index 77bfe57e370..6a499a98681 100644
--- a/compiler/rustc_passes/src/errors.rs
+++ b/compiler/rustc_passes/src/errors.rs
@@ -390,13 +390,6 @@ pub struct FfiConstInvalidTarget {
     pub attr_span: Span,
 }
 
-#[derive(Diagnostic)]
-#[diag(passes_ffi_returns_twice_invalid_target, code = E0724)]
-pub struct FfiReturnsTwiceInvalidTarget {
-    #[primary_span]
-    pub attr_span: Span,
-}
-
 #[derive(LintDiagnostic)]
 #[diag(passes_must_use_async)]
 pub struct MustUseAsync {
diff --git a/src/tools/tidy/src/ui_tests.rs b/src/tools/tidy/src/ui_tests.rs
index 451276b5ac1..09469427426 100644
--- a/src/tools/tidy/src/ui_tests.rs
+++ b/src/tools/tidy/src/ui_tests.rs
@@ -14,7 +14,7 @@ use std::path::{Path, PathBuf};
 // #73494.
 const ENTRY_LIMIT: usize = 900;
 const ISSUES_ENTRY_LIMIT: usize = 1807;
-const ROOT_ENTRY_LIMIT: usize = 870;
+const ROOT_ENTRY_LIMIT: usize = 868;
 
 const EXPECTED_TEST_FILE_EXTENSIONS: &[&str] = &[
     "rs",     // test source files
diff --git a/tests/codegen/cffi/ffi-returns-twice.rs b/tests/codegen/cffi/ffi-returns-twice.rs
deleted file mode 100644
index 0fbe03f0bb6..00000000000
--- a/tests/codegen/cffi/ffi-returns-twice.rs
+++ /dev/null
@@ -1,11 +0,0 @@
-// compile-flags: -C no-prepopulate-passes
-#![crate_type = "lib"]
-#![feature(ffi_returns_twice)]
-
-pub fn bar() { unsafe { foo() } }
-
-extern "C" {
-    // CHECK: declare{{( dso_local)?}} void @foo(){{.*}}[[ATTRS:#[0-9]+]]
-    // CHECK: attributes [[ATTRS]] = { {{.*}}returns_twice{{.*}} }
-    #[ffi_returns_twice] pub fn foo();
-}
diff --git a/tests/ui/feature-gates/feature-gate-ffi_returns_twice.rs b/tests/ui/feature-gates/feature-gate-ffi_returns_twice.rs
deleted file mode 100644
index f354534356c..00000000000
--- a/tests/ui/feature-gates/feature-gate-ffi_returns_twice.rs
+++ /dev/null
@@ -1,6 +0,0 @@
-#![crate_type = "lib"]
-
-extern "C" {
-    #[ffi_returns_twice] //~ ERROR the `#[ffi_returns_twice]` attribute is an experimental feature
-    pub fn foo();
-}
diff --git a/tests/ui/feature-gates/feature-gate-ffi_returns_twice.stderr b/tests/ui/feature-gates/feature-gate-ffi_returns_twice.stderr
deleted file mode 100644
index 8d19874c36a..00000000000
--- a/tests/ui/feature-gates/feature-gate-ffi_returns_twice.stderr
+++ /dev/null
@@ -1,13 +0,0 @@
-error[E0658]: the `#[ffi_returns_twice]` attribute is an experimental feature
-  --> $DIR/feature-gate-ffi_returns_twice.rs:4:5
-   |
-LL |     #[ffi_returns_twice]
-   |     ^^^^^^^^^^^^^^^^^^^^
-   |
-   = note: see issue #58314 <https://github.com/rust-lang/rust/issues/58314> for more information
-   = help: add `#![feature(ffi_returns_twice)]` 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: aborting due to 1 previous error
-
-For more information about this error, try `rustc --explain E0658`.
diff --git a/tests/ui/ffi_returns_twice.rs b/tests/ui/ffi_returns_twice.rs
deleted file mode 100644
index 8195d0e4863..00000000000
--- a/tests/ui/ffi_returns_twice.rs
+++ /dev/null
@@ -1,15 +0,0 @@
-#![feature(ffi_returns_twice)]
-#![crate_type = "lib"]
-
-#[ffi_returns_twice] //~ ERROR `#[ffi_returns_twice]` may only be used on foreign functions
-pub fn foo() {}
-
-#[ffi_returns_twice] //~ ERROR `#[ffi_returns_twice]` may only be used on foreign functions
-macro_rules! bar {
-    () => ()
-}
-
-extern "C" {
-    #[ffi_returns_twice] //~ ERROR `#[ffi_returns_twice]` may only be used on foreign functions
-    static INT: i32;
-}
diff --git a/tests/ui/ffi_returns_twice.stderr b/tests/ui/ffi_returns_twice.stderr
deleted file mode 100644
index 0abe7613f14..00000000000
--- a/tests/ui/ffi_returns_twice.stderr
+++ /dev/null
@@ -1,21 +0,0 @@
-error[E0724]: `#[ffi_returns_twice]` may only be used on foreign functions
-  --> $DIR/ffi_returns_twice.rs:4:1
-   |
-LL | #[ffi_returns_twice]
-   | ^^^^^^^^^^^^^^^^^^^^
-
-error[E0724]: `#[ffi_returns_twice]` may only be used on foreign functions
-  --> $DIR/ffi_returns_twice.rs:7:1
-   |
-LL | #[ffi_returns_twice]
-   | ^^^^^^^^^^^^^^^^^^^^
-
-error[E0724]: `#[ffi_returns_twice]` may only be used on foreign functions
-  --> $DIR/ffi_returns_twice.rs:13:5
-   |
-LL |     #[ffi_returns_twice]
-   |     ^^^^^^^^^^^^^^^^^^^^
-
-error: aborting due to 3 previous errors
-
-For more information about this error, try `rustc --explain E0724`.