Rollup of 4 pull requests

compiler/rustc_codegen_cranelift/src/intrinsics/mod.rs

@@ -1136,6 +1136,11 @@ pub(crate) fn codegen_intrinsic_call<'tcx>(
                 };
             ret.write_cvalue(fx, CValue::by_val(is_eq_value, ret.layout()));
         };
+
+        black_box, (c a) {
+            // FIXME implement black_box semantics
+            ret.write_cvalue(fx, a);
+        };
     }
 
     if let Some((_, dest)) = destination {

compiler/rustc_codegen_llvm/src/asm.rs

@@ -425,7 +425,7 @@ impl AsmMethods for CodegenCx<'ll, 'tcx> {
     }
 }
 
-fn inline_asm_call(
+pub(crate) fn inline_asm_call(
     bx: &mut Builder<'a, 'll, 'tcx>,
     asm: &str,
     cons: &str,

compiler/rustc_codegen_llvm/src/intrinsic.rs

@@ -7,6 +7,7 @@ use crate::type_of::LayoutLlvmExt;
 use crate::va_arg::emit_va_arg;
 use crate::value::Value;
 
+use rustc_ast as ast;
 use rustc_codegen_ssa::base::{compare_simd_types, wants_msvc_seh};
 use rustc_codegen_ssa::common::span_invalid_monomorphization_error;
 use rustc_codegen_ssa::common::{IntPredicate, TypeKind};
@@ -327,6 +328,31 @@ impl IntrinsicCallMethods<'tcx> for Builder<'a, 'll, 'tcx> {
                 }
             }
 
+            sym::black_box => {
+                args[0].val.store(self, result);
+
+                // We need to "use" the argument in some way LLVM can't introspect, and on
+                // targets that support it we can typically leverage inline assembly to do
+                // this. LLVM's interpretation of inline assembly is that it's, well, a black
+                // box. This isn't the greatest implementation since it probably deoptimizes
+                // more than we want, but it's so far good enough.
+                crate::asm::inline_asm_call(
+                    self,
+                    "",
+                    "r,~{memory}",
+                    &[result.llval],
+                    self.type_void(),
+                    true,
+                    false,
+                    ast::LlvmAsmDialect::Att,
+                    &[span],
+                )
+                .unwrap_or_else(|| bug!("failed to generate inline asm call for `black_box`"));
+
+                // We have copied the value to `result` already.
+                return;
+            }
+
             _ if name_str.starts_with("simd_") => {
                 match generic_simd_intrinsic(self, name, callee_ty, args, ret_ty, llret_ty, span) {
                     Ok(llval) => llval,

compiler/rustc_lint/src/non_fmt_panic.rs

@@ -2,6 +2,7 @@ use crate::{LateContext, LateLintPass, LintContext};
 use rustc_ast as ast;
 use rustc_errors::{pluralize, Applicability};
 use rustc_hir as hir;
+use rustc_middle::lint::in_external_macro;
 use rustc_middle::ty;
 use rustc_parse_format::{ParseMode, Parser, Piece};
 use rustc_session::lint::FutureIncompatibilityReason;
@@ -75,6 +76,11 @@ fn check_panic<'tcx>(cx: &LateContext<'tcx>, f: &'tcx hir::Expr<'tcx>, arg: &'tc
 
     let (span, panic, symbol_str) = panic_call(cx, f);
 
+    if in_external_macro(cx.sess(), span) {
+        // Nothing that can be done about it in the current crate.
+        return;
+    }
+
     // Find the span of the argument to `panic!()`, before expansion in the
     // case of `panic!(some_macro!())`.
     // We don't use source_callsite(), because this `panic!(..)` might itself
@@ -152,6 +158,13 @@ fn check_panic_str<'tcx>(
         return;
     }
 
+    let (span, _, _) = panic_call(cx, f);
+
+    if in_external_macro(cx.sess(), span) && in_external_macro(cx.sess(), arg.span) {
+        // Nothing that can be done about it in the current crate.
+        return;
+    }
+
     let fmt_span = arg.span.source_callsite();
 
     let (snippet, style) = match cx.sess().parse_sess.source_map().span_to_snippet(fmt_span) {
@@ -167,8 +180,6 @@ fn check_panic_str<'tcx>(
         Parser::new(fmt.as_ref(), style, snippet.clone(), false, ParseMode::Format);
     let n_arguments = (&mut fmt_parser).filter(|a| matches!(a, Piece::NextArgument(_))).count();
 
-    let (span, _, _) = panic_call(cx, f);
-
     if n_arguments > 0 && fmt_parser.errors.is_empty() {
         let arg_spans: Vec<_> = match &fmt_parser.arg_places[..] {
             [] => vec![fmt_span],

compiler/rustc_middle/src/ty/layout.rs

@@ -112,9 +112,6 @@ impl IntegerExt for Integer {
         let unsigned_fit = Integer::fit_unsigned(cmp::max(min as u128, max as u128));
         let signed_fit = cmp::max(Integer::fit_signed(min), Integer::fit_signed(max));
 
-        let mut min_from_extern = None;
-        let min_default = I8;
-
         if let Some(ity) = repr.int {
             let discr = Integer::from_attr(&tcx, ity);
             let fit = if ity.is_signed() { signed_fit } else { unsigned_fit };
@@ -128,19 +125,14 @@ impl IntegerExt for Integer {
             return (discr, ity.is_signed());
         }
 
-        if repr.c() {
-            match &tcx.sess.target.arch[..] {
-                "hexagon" => min_from_extern = Some(I8),
-                // WARNING: the ARM EABI has two variants; the one corresponding
-                // to `at_least == I32` appears to be used on Linux and NetBSD,
-                // but some systems may use the variant corresponding to no
-                // lower bound. However, we don't run on those yet...?
-                "arm" => min_from_extern = Some(I32),
-                _ => min_from_extern = Some(I32),
-            }
-        }
-
-        let at_least = min_from_extern.unwrap_or(min_default);
+        let at_least = if repr.c() {
+            // This is usually I32, however it can be different on some platforms,
+            // notably hexagon and arm-none/thumb-none
+            tcx.data_layout().c_enum_min_size
+        } else {
+            // repr(Rust) enums try to be as small as possible
+            I8
+        };
 
         // If there are no negative values, we can use the unsigned fit.
         if min >= 0 {

compiler/rustc_mir/src/interpret/intrinsics.rs

@@ -465,7 +465,7 @@ impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
                 );
                 self.copy_op(&self.operand_index(&args[0], index)?, dest)?;
             }
-            sym::likely | sym::unlikely => {
+            sym::likely | sym::unlikely | sym::black_box => {
                 // These just return their argument
                 self.copy_op(&args[0], dest)?;
             }

compiler/rustc_span/src/symbol.rs

@@ -335,6 +335,7 @@ symbols! {
         bitreverse,
         bitxor,
         bitxor_assign,
+        black_box,
         block,
         bool,
         borrowck_graphviz_format,

compiler/rustc_target/src/abi/mod.rs

@@ -36,6 +36,9 @@ pub struct TargetDataLayout {
     pub vector_align: Vec<(Size, AbiAndPrefAlign)>,
 
     pub instruction_address_space: AddressSpace,
+
+    /// Minimum size of #[repr(C)] enums (default I32 bits)
+    pub c_enum_min_size: Integer,
 }
 
 impl Default for TargetDataLayout {
@@ -60,6 +63,7 @@ impl Default for TargetDataLayout {
                 (Size::from_bits(128), AbiAndPrefAlign::new(align(128))),
             ],
             instruction_address_space: AddressSpace::DATA,
+            c_enum_min_size: Integer::I32,
         }
     }
 }
@@ -173,6 +177,8 @@ impl TargetDataLayout {
             ));
         }
 
+        dl.c_enum_min_size = Integer::from_size(Size::from_bits(target.c_enum_min_bits))?;
+
         Ok(dl)
     }
 
@@ -610,6 +616,17 @@ impl Integer {
         }
         I8
     }
+
+    fn from_size(size: Size) -> Result<Self, String> {
+        match size.bits() {
+            8 => Ok(Integer::I8),
+            16 => Ok(Integer::I16),
+            32 => Ok(Integer::I32),
+            64 => Ok(Integer::I64),
+            128 => Ok(Integer::I128),
+            _ => Err(format!("rust does not support integers with {} bits", size.bits())),
+        }
+    }
 }
 
 /// Fundamental unit of memory access and layout.

compiler/rustc_target/src/spec/armebv7r_none_eabi.rs

@@ -20,6 +20,8 @@ pub fn target() -> Target {
             panic_strategy: PanicStrategy::Abort,
             max_atomic_width: Some(32),
             emit_debug_gdb_scripts: false,
+            // GCC and Clang default to 8 for arm-none here
+            c_enum_min_bits: 8,
             ..Default::default()
         },
     }

compiler/rustc_target/src/spec/armebv7r_none_eabihf.rs

@@ -21,6 +21,8 @@ pub fn target() -> Target {
             features: "+vfp3,-d32,-fp16".to_string(),
             max_atomic_width: Some(32),
             emit_debug_gdb_scripts: false,
+            // GCC and Clang default to 8 for arm-none here
+            c_enum_min_bits: 8,
             ..Default::default()
         },
     }

compiler/rustc_target/src/spec/armv7a_none_eabi.rs

@@ -28,6 +28,7 @@ pub fn target() -> Target {
         max_atomic_width: Some(64),
         panic_strategy: PanicStrategy::Abort,
         emit_debug_gdb_scripts: false,
+        c_enum_min_bits: 8,
         ..Default::default()
     };
     Target {

compiler/rustc_target/src/spec/armv7a_none_eabihf.rs

@@ -19,6 +19,8 @@ pub fn target() -> Target {
         max_atomic_width: Some(64),
         panic_strategy: PanicStrategy::Abort,
         emit_debug_gdb_scripts: false,
+        // GCC and Clang default to 8 for arm-none here
+        c_enum_min_bits: 8,
         ..Default::default()
     };
     Target {

compiler/rustc_target/src/spec/armv7r_none_eabi.rs

@@ -19,6 +19,8 @@ pub fn target() -> Target {
             panic_strategy: PanicStrategy::Abort,
             max_atomic_width: Some(32),
             emit_debug_gdb_scripts: false,
+            // GCC and Clang default to 8 for arm-none here
+            c_enum_min_bits: 8,
             ..Default::default()
         },
     }

compiler/rustc_target/src/spec/armv7r_none_eabihf.rs

@@ -20,6 +20,8 @@ pub fn target() -> Target {
             features: "+vfp3,-d32,-fp16".to_string(),
             max_atomic_width: Some(32),
             emit_debug_gdb_scripts: false,
+            // GCC and Clang default to 8 for arm-none here
+            c_enum_min_bits: 8,
             ..Default::default()
         },
     }

compiler/rustc_target/src/spec/hexagon_unknown_linux_musl.rs

@@ -13,6 +13,8 @@ pub fn target() -> Target {
     base.dynamic_linking = true;
     base.executables = true;
 
+    base.c_enum_min_bits = 8;
+
     Target {
         llvm_target: "hexagon-unknown-linux-musl".to_string(),
         pointer_width: 32,

compiler/rustc_target/src/spec/mod.rs

@@ -1336,6 +1336,9 @@ pub struct TargetOptions {
 
     /// If present it's a default value to use for adjusting the C ABI.
     pub default_adjusted_cabi: Option<Abi>,
+
+    /// Minimum number of bits in #[repr(C)] enum. Defaults to 32.
+    pub c_enum_min_bits: u64,
 }
 
 impl Default for TargetOptions {
@@ -1440,6 +1443,7 @@ impl Default for TargetOptions {
             split_debuginfo: SplitDebuginfo::Off,
             supported_sanitizers: SanitizerSet::empty(),
             default_adjusted_cabi: None,
+            c_enum_min_bits: 32,
         }
     }
 }
@@ -1604,6 +1608,12 @@ impl Target {
                     base.$key_name = s;
                 }
             } );
+            ($key_name:ident, u64) => ( {
+                let name = (stringify!($key_name)).replace("_", "-");
+                if let Some(s) = obj.remove_key(&name).and_then(|j| Json::as_u64(&j)) {
+                    base.$key_name = s;
+                }
+            } );
             ($key_name:ident, Option<u32>) => ( {
                 let name = (stringify!($key_name)).replace("_", "-");
                 if let Some(s) = obj.remove_key(&name).and_then(|j| Json::as_u64(&j)) {
@@ -2017,6 +2027,7 @@ impl Target {
         key!(split_debuginfo, SplitDebuginfo)?;
         key!(supported_sanitizers, SanitizerSet)?;
         key!(default_adjusted_cabi, Option<Abi>)?;
+        key!(c_enum_min_bits, u64);
 
         if base.is_builtin {
             // This can cause unfortunate ICEs later down the line.
@@ -2255,6 +2266,7 @@ impl ToJson for Target {
         target_option_val!(has_thumb_interworking);
         target_option_val!(split_debuginfo);
         target_option_val!(supported_sanitizers);
+        target_option_val!(c_enum_min_bits);
 
         if let Some(abi) = self.default_adjusted_cabi {
             d.insert("default-adjusted-cabi".to_string(), Abi::name(abi).to_json());

compiler/rustc_target/src/spec/thumb_base.rs

@@ -53,6 +53,9 @@ pub fn opts() -> TargetOptions {
         // LLVM is eager to trash the link register when calling `noreturn` functions, which
         // breaks debugging. Preserve LR by default to prevent that from happening.
         frame_pointer: FramePointer::Always,
+        // ARM supports multiple ABIs for enums, the linux one matches the default of 32 here
+        // but any arm-none or thumb-none target will be defaulted to 8 on GCC and clang
+        c_enum_min_bits: 8,
         ..Default::default()
     }
 }

compiler/rustc_typeck/src/check/intrinsic.rs

@@ -102,6 +102,7 @@ pub fn intrinsic_operation_unsafety(intrinsic: Symbol) -> hir::Unsafety {
         | sym::maxnumf64
         | sym::type_name
         | sym::forget
+        | sym::black_box
         | sym::variant_count => hir::Unsafety::Normal,
         _ => hir::Unsafety::Unsafe,
     }
@@ -387,6 +388,8 @@ pub fn check_intrinsic_type(tcx: TyCtxt<'_>, it: &hir::ForeignItem<'_>) {
                 (1, vec![param_ty; 2], tcx.types.bool)
             }
 
+            sym::black_box => (1, vec![param(0)], param(0)),
+
             other => {
                 tcx.sess.emit_err(UnrecognizedIntrinsicFunction { span: it.span, name: other });
                 return;

compiler/rustc_typeck/src/check/upvar.rs

@@ -649,11 +649,20 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                         match self.tcx.sess.source_map().span_to_snippet(closure_body_span) {
                             Ok(s) => {
                                 let trimmed = s.trim_start();
+                                let mut lines = trimmed.lines();
+                                let line1 = lines.next().unwrap_or_default();
 
                                 // If the closure contains a block then replace the opening brace
                                 // with "{ let _ = (..); "
-                                let sugg = if let Some('{') = trimmed.chars().next() {
-                                    format!("{{ {}; {}", migration_string, &trimmed[1..])
+                                let sugg = if line1.trim_end() == "{" {
+                                    // This is a multi-line closure with just a `{` on the first line,
+                                    // so we put the `let` on its own line.
+                                    // We take the indentation from the next non-empty line.
+                                    let line2 = lines.filter(|line| !line.is_empty()).next().unwrap_or_default();
+                                    let indent = line2.split_once(|c: char| !c.is_whitespace()).unwrap_or_default().0;
+                                    format!("{{\n{}{};{}", indent, migration_string, &trimmed[line1.len()..])
+                                } else if line1.starts_with('{') {
+                                    format!("{{ {}; {}", migration_string, &trimmed[1..].trim_start())
                                 } else {
                                     format!("{{ {}; {} }}", migration_string, s)
                                 };

library/core/src/hint.rs

@@ -152,23 +152,19 @@ pub fn spin_loop() {
 /// backend used. Programs cannot rely on `black_box` for *correctness* in any way.
 ///
 /// [`std::convert::identity`]: crate::convert::identity
-#[cfg_attr(not(miri), inline)]
-#[cfg_attr(miri, inline(never))]
+#[inline]
 #[unstable(feature = "bench_black_box", issue = "64102")]
-#[cfg_attr(miri, allow(unused_mut))]
+#[cfg_attr(not(bootstrap), allow(unused_mut))]
 pub fn black_box<T>(mut dummy: T) -> T {
-    // We need to "use" the argument in some way LLVM can't introspect, and on
-    // targets that support it we can typically leverage inline assembly to do
-    // this. LLVM's interpretation of inline assembly is that it's, well, a black
-    // box. This isn't the greatest implementation since it probably deoptimizes
-    // more than we want, but it's so far good enough.
-
-    #[cfg(not(miri))] // This is just a hint, so it is fine to skip in Miri.
+    #[cfg(bootstrap)]
     // SAFETY: the inline assembly is a no-op.
     unsafe {
-        // FIXME: Cannot use `asm!` because it doesn't support MIPS and other architectures.
         llvm_asm!("" : : "r"(&mut dummy) : "memory" : "volatile");
+        dummy
     }
 
-    dummy
+    #[cfg(not(bootstrap))]
+    {
+        crate::intrinsics::black_box(dummy)
+    }
 }