rust-lang · RalfJung · Jul 10, 2020 · Jul 10, 2020 · Aug 29, 2020 · Sep 18, 2020
diff --git a/Cargo.lock b/Cargo.lock
@@ -207,6 +207,7 @@ dependencies = [
  "ignore",
  "lazy_static",
  "libc",
+ "merge",
  "num_cpus",
  "opener",
  "pretty_assertions",
@@ -1909,6 +1910,28 @@ dependencies = [
  "autocfg",
 ]
 
+[[package]]
+name = "merge"
+version = "0.1.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "10bbef93abb1da61525bbc45eeaff6473a41907d19f8f9aa5168d214e10693e9"
+dependencies = [
+ "merge_derive",
+ "num-traits",
+]
+
+[[package]]
+name = "merge_derive"
+version = "0.1.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "209d075476da2e63b4b29e72a2ef627b840589588e71400a25e3565c4f849d07"
+dependencies = [
+ "proc-macro-error",
+ "proc-macro2",
+ "quote",
+ "syn",
+]
+
 [[package]]
 name = "minifier"
 version = "0.0.33"

diff --git a/compiler/rustc_codegen_llvm/src/base.rs b/compiler/rustc_codegen_llvm/src/base.rs
@@ -108,7 +108,7 @@ pub fn compile_codegen_unit(
 
     // We assume that the cost to run LLVM on a CGU is proportional to
     // the time we needed for codegenning it.
-    let cost = time_to_codegen.as_secs() * 1_000_000_000 + time_to_codegen.subsec_nanos() as u64;
+    let cost = time_to_codegen.as_nanos() as u64;
 
     fn module_codegen(tcx: TyCtxt<'_>, cgu_name: Symbol) -> ModuleCodegen<ModuleLlvm> {
         let cgu = tcx.codegen_unit(cgu_name);

diff --git a/compiler/rustc_codegen_llvm/src/consts.rs b/compiler/rustc_codegen_llvm/src/consts.rs
@@ -7,6 +7,7 @@ use crate::type_of::LayoutLlvmExt;
 use crate::value::Value;
 use libc::c_uint;
 use rustc_codegen_ssa::traits::*;
+use rustc_data_structures::const_cstr;
 use rustc_hir as hir;
 use rustc_hir::def_id::DefId;
 use rustc_hir::Node;
@@ -22,8 +23,6 @@ use rustc_span::Span;
 use rustc_target::abi::{AddressSpace, Align, HasDataLayout, LayoutOf, Primitive, Scalar, Size};
 use tracing::debug;
 
-use std::ffi::CStr;
-
 pub fn const_alloc_to_llvm(cx: &CodegenCx<'ll, '_>, alloc: &Allocation) -> &'ll Value {
     let mut llvals = Vec::with_capacity(alloc.relocations().len() + 1);
     let dl = cx.data_layout();
@@ -454,9 +453,9 @@ impl StaticMethods for CodegenCx<'ll, 'tcx> {
                             .all(|&byte| byte == 0);
 
                     let sect_name = if all_bytes_are_zero {
-                        CStr::from_bytes_with_nul_unchecked(b"__DATA,__thread_bss\0")
+                        const_cstr!("__DATA,__thread_bss")
                     } else {
-                        CStr::from_bytes_with_nul_unchecked(b"__DATA,__thread_data\0")
+                        const_cstr!("__DATA,__thread_data")
                     };
                     llvm::LLVMSetSection(g, sect_name.as_ptr());
                 }

diff --git a/compiler/rustc_codegen_llvm/src/context.rs b/compiler/rustc_codegen_llvm/src/context.rs
@@ -433,6 +433,17 @@ impl MiscMethods<'tcx> for CodegenCx<'ll, 'tcx> {
             llvm::LLVMSetSection(g, section.as_ptr());
         }
     }
+
+    fn declare_c_main(&self, fn_type: Self::Type) -> Option<Self::Function> {
+        if self.get_declared_value("main").is_none() {
+            Some(self.declare_cfn("main", fn_type))
+        } else {
+            // If the symbol already exists, it is an error: for example, the user wrote
+            // #[no_mangle] extern "C" fn main(..) {..}
+            // instead of #[start]
+            None
+        }
+    }
 }
 
 impl CodegenCx<'b, 'tcx> {

diff --git a/compiler/rustc_codegen_llvm/src/declare.rs b/compiler/rustc_codegen_llvm/src/declare.rs
@@ -51,42 +51,69 @@ fn declare_raw_fn(
     llfn
 }
 
-impl DeclareMethods<'tcx> for CodegenCx<'ll, 'tcx> {
-    fn declare_global(&self, name: &str, ty: &'ll Type) -> &'ll Value {
+impl CodegenCx<'ll, 'tcx> {
+    /// Declare a global value.
+    ///
+    /// If there’s a value with the same name already declared, the function will
+    /// return its Value instead.
+    pub fn declare_global(&self, name: &str, ty: &'ll Type) -> &'ll Value {
         debug!("declare_global(name={:?})", name);
         unsafe { llvm::LLVMRustGetOrInsertGlobal(self.llmod, name.as_ptr().cast(), name.len(), ty) }
     }
 
-    fn declare_cfn(&self, name: &str, fn_type: &'ll Type) -> &'ll Value {
+    /// Declare a C ABI function.
+    ///
+    /// Only use this for foreign function ABIs and glue. For Rust functions use
+    /// `declare_fn` instead.
+    ///
+    /// If there’s a value with the same name already declared, the function will
+    /// update the declaration and return existing Value instead.
+    pub fn declare_cfn(&self, name: &str, fn_type: &'ll Type) -> &'ll Value {
         declare_raw_fn(self, name, llvm::CCallConv, fn_type)
     }
 
-    fn declare_fn(&self, name: &str, fn_abi: &FnAbi<'tcx, Ty<'tcx>>) -> &'ll Value {
+    /// Declare a Rust function.
+    ///
+    /// If there’s a value with the same name already declared, the function will
+    /// update the declaration and return existing Value instead.
+    pub fn declare_fn(&self, name: &str, fn_abi: &FnAbi<'tcx, Ty<'tcx>>) -> &'ll Value {
         debug!("declare_rust_fn(name={:?}, fn_abi={:?})", name, fn_abi);
 
         let llfn = declare_raw_fn(self, name, fn_abi.llvm_cconv(), fn_abi.llvm_type(self));
         fn_abi.apply_attrs_llfn(self, llfn);
         llfn
     }
 
-    fn define_global(&self, name: &str, ty: &'ll Type) -> Option<&'ll Value> {
+    /// Declare a global with an intention to define it.
+    ///
+    /// Use this function when you intend to define a global. This function will
+    /// return `None` if the name already has a definition associated with it. In that
+    /// case an error should be reported to the user, because it usually happens due
+    /// to user’s fault (e.g., misuse of `#[no_mangle]` or `#[export_name]` attributes).
+    pub fn define_global(&self, name: &str, ty: &'ll Type) -> Option<&'ll Value> {
         if self.get_defined_value(name).is_some() {
             None
         } else {
             Some(self.declare_global(name, ty))
         }
     }
 
-    fn define_private_global(&self, ty: &'ll Type) -> &'ll Value {
+    /// Declare a private global
+    ///
+    /// Use this function when you intend to define a global without a name.
+    pub fn define_private_global(&self, ty: &'ll Type) -> &'ll Value {
         unsafe { llvm::LLVMRustInsertPrivateGlobal(self.llmod, ty) }
     }
 
-    fn get_declared_value(&self, name: &str) -> Option<&'ll Value> {
+    /// Gets declared value by name.
+    pub fn get_declared_value(&self, name: &str) -> Option<&'ll Value> {
         debug!("get_declared_value(name={:?})", name);
         unsafe { llvm::LLVMRustGetNamedValue(self.llmod, name.as_ptr().cast(), name.len()) }
     }
 
-    fn get_defined_value(&self, name: &str) -> Option<&'ll Value> {
+    /// Gets defined or externally defined (AvailableExternally linkage) value by
+    /// name.
+    pub fn get_defined_value(&self, name: &str) -> Option<&'ll Value> {
         self.get_declared_value(name).and_then(|val| {
             let declaration = unsafe { llvm::LLVMIsDeclaration(val) != 0 };
             if !declaration { Some(val) } else { None }

diff --git a/compiler/rustc_codegen_ssa/src/base.rs b/compiler/rustc_codegen_ssa/src/base.rs
@@ -407,16 +407,18 @@ pub fn maybe_create_entry_wrapper<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>>(
         // listing.
         let main_ret_ty = cx.tcx().erase_regions(&main_ret_ty.no_bound_vars().unwrap());
 
-        if cx.get_declared_value("main").is_some() {
-            // FIXME: We should be smart and show a better diagnostic here.
-            cx.sess()
-                .struct_span_err(sp, "entry symbol `main` declared multiple times")
-                .help("did you use `#[no_mangle]` on `fn main`? Use `#[start]` instead")
-                .emit();
-            cx.sess().abort_if_errors();
-            bug!();
-        }
-        let llfn = cx.declare_cfn("main", llfty);
+        let llfn = match cx.declare_c_main(llfty) {
+            Some(llfn) => llfn,
+            None => {
+                // FIXME: We should be smart and show a better diagnostic here.
+                cx.sess()
+                    .struct_span_err(sp, "entry symbol `main` declared multiple times")
+                    .help("did you use `#[no_mangle]` on `fn main`? Use `#[start]` instead")
+                    .emit();
+                cx.sess().abort_if_errors();
+                bug!();
+            }
+        };
 
         // `main` should respect same config for frame pointer elimination as rest of code
         cx.set_frame_pointer_elimination(llfn);

diff --git a/compiler/rustc_codegen_ssa/src/traits/declare.rs b/compiler/rustc_codegen_ssa/src/traits/declare.rs
@@ -1,51 +1,7 @@
 use super::BackendTypes;
 use rustc_hir::def_id::DefId;
 use rustc_middle::mir::mono::{Linkage, Visibility};
-use rustc_middle::ty::{Instance, Ty};
-use rustc_target::abi::call::FnAbi;
-
-pub trait DeclareMethods<'tcx>: BackendTypes {
-    /// Declare a global value.
-    ///
-    /// If there’s a value with the same name already declared, the function will
-    /// return its Value instead.
-    fn declare_global(&self, name: &str, ty: Self::Type) -> Self::Value;
-
-    /// Declare a C ABI function.
-    ///
-    /// Only use this for foreign function ABIs and glue. For Rust functions use
-    /// `declare_fn` instead.
-    ///
-    /// If there’s a value with the same name already declared, the function will
-    /// update the declaration and return existing Value instead.
-    fn declare_cfn(&self, name: &str, fn_type: Self::Type) -> Self::Function;
-
-    /// Declare a Rust function.
-    ///
-    /// If there’s a value with the same name already declared, the function will
-    /// update the declaration and return existing Value instead.
-    fn declare_fn(&self, name: &str, fn_abi: &FnAbi<'tcx, Ty<'tcx>>) -> Self::Function;
-
-    /// Declare a global with an intention to define it.
-    ///
-    /// Use this function when you intend to define a global. This function will
-    /// return `None` if the name already has a definition associated with it. In that
-    /// case an error should be reported to the user, because it usually happens due
-    /// to user’s fault (e.g., misuse of `#[no_mangle]` or `#[export_name]` attributes).
-    fn define_global(&self, name: &str, ty: Self::Type) -> Option<Self::Value>;
-
-    /// Declare a private global
-    ///
-    /// Use this function when you intend to define a global without a name.
-    fn define_private_global(&self, ty: Self::Type) -> Self::Value;
-
-    /// Gets declared value by name.
-    fn get_declared_value(&self, name: &str) -> Option<Self::Value>;
-
-    /// Gets defined or externally defined (AvailableExternally linkage) value by
-    /// name.
-    fn get_defined_value(&self, name: &str) -> Option<Self::Value>;
-}
+use rustc_middle::ty::Instance;
 
 pub trait PreDefineMethods<'tcx>: BackendTypes {
     fn predefine_static(

diff --git a/compiler/rustc_codegen_ssa/src/traits/misc.rs b/compiler/rustc_codegen_ssa/src/traits/misc.rs
@@ -19,4 +19,6 @@ pub trait MiscMethods<'tcx>: BackendTypes {
     fn set_frame_pointer_elimination(&self, llfn: Self::Function);
     fn apply_target_cpu_attr(&self, llfn: Self::Function);
     fn create_used_variable(&self);
+    /// Declares the extern "C" main function for the entry point. Returns None if the symbol already exists.
+    fn declare_c_main(&self, fn_type: Self::Type) -> Option<Self::Function>;
 }
diff --git a/compiler/rustc_codegen_ssa/src/traits/mod.rs b/compiler/rustc_codegen_ssa/src/traits/mod.rs
@@ -35,7 +35,7 @@ pub use self::builder::{BuilderMethods, OverflowOp};
 pub use self::consts::ConstMethods;
 pub use self::coverageinfo::{CoverageInfoBuilderMethods, CoverageInfoMethods};
 pub use self::debuginfo::{DebugInfoBuilderMethods, DebugInfoMethods};
-pub use self::declare::{DeclareMethods, PreDefineMethods};
+pub use self::declare::PreDefineMethods;
 pub use self::intrinsic::IntrinsicCallMethods;
 pub use self::misc::MiscMethods;
 pub use self::statics::{StaticBuilderMethods, StaticMethods};
@@ -60,7 +60,6 @@ pub trait CodegenMethods<'tcx>:
     + StaticMethods
     + CoverageInfoMethods
     + DebugInfoMethods<'tcx>
-    + DeclareMethods<'tcx>
     + AsmMethods
     + PreDefineMethods<'tcx>
     + HasParamEnv<'tcx>
@@ -77,7 +76,6 @@ impl<'tcx, T> CodegenMethods<'tcx> for T where
         + StaticMethods
         + CoverageInfoMethods
         + DebugInfoMethods<'tcx>
-        + DeclareMethods<'tcx>
         + AsmMethods
         + PreDefineMethods<'tcx>
         + HasParamEnv<'tcx>

diff --git a/compiler/rustc_data_structures/src/macros.rs b/compiler/rustc_data_structures/src/macros.rs
@@ -1,15 +1,3 @@
-/// A simple static assertion macro.
-#[macro_export]
-#[allow_internal_unstable(type_ascription)]
-macro_rules! static_assert {
-    ($test:expr) => {
-        // Use the bool to access an array such that if the bool is false, the access
-        // is out-of-bounds.
-        #[allow(dead_code)]
-        const _: () = [()][!($test: bool) as usize];
-    };
-}
-
 /// Type size assertion. The first argument is a type and the second argument is its expected size.
 #[macro_export]
 macro_rules! static_assert_size {

diff --git a/compiler/rustc_data_structures/src/profiling.rs b/compiler/rustc_data_structures/src/profiling.rs
@@ -600,10 +600,7 @@ pub fn print_time_passes_entry(do_it: bool, what: &str, dur: Duration) {
 // Hack up our own formatting for the duration to make it easier for scripts
 // to parse (always use the same number of decimal places and the same unit).
 pub fn duration_to_secs_str(dur: std::time::Duration) -> String {
-    const NANOS_PER_SEC: f64 = 1_000_000_000.0;
-    let secs = dur.as_secs() as f64 + dur.subsec_nanos() as f64 / NANOS_PER_SEC;
-
-    format!("{:.3}", secs)
+    format!("{:.3}", dur.as_secs_f64())
 }
 
 // Memory reporting

diff --git a/config.toml.example b/config.toml.example
@@ -9,6 +9,16 @@
 # a custom configuration file can also be specified with `--config` to the build
 # system.
 
+# =============================================================================
+# Global Settings
+# =============================================================================
+
+# Use different pre-set defaults than the global defaults.
+#
+# See `src/bootstrap/defaults` for more information.
+# Note that this has no default value (x.py uses the defaults in `config.toml.example`).
+#profile = <none>
+
 # =============================================================================
 # Tweaking how LLVM is compiled
 # =============================================================================