Declare main as visibility hidden on targets that default to hidden.

compiler/rustc_codegen_llvm/src/builder.rs

@@ -1458,7 +1458,12 @@ impl<'a, 'll, 'tcx> Builder<'a, 'll, 'tcx> {
         } else {
             format!("llvm.{}.sat.i{}.f{}", instr, int_width, float_width)
         };
-        let f = self.declare_cfn(&name, llvm::UnnamedAddr::No, self.type_func(&[src_ty], dest_ty));
+        let f = self.declare_cfn(
+            &name,
+            llvm::UnnamedAddr::No,
+            llvm::Visibility::Default,
+            self.type_func(&[src_ty], dest_ty),
+        );
         self.call(self.type_func(&[src_ty], dest_ty), f, &[val], None)
     }
 

compiler/rustc_codegen_llvm/src/context.rs

@@ -528,7 +528,12 @@ impl<'ll, 'tcx> MiscMethods<'tcx> for CodegenCx<'ll, 'tcx> {
                     llfn
                 } else {
                     let fty = self.type_variadic_func(&[], self.type_i32());
-                    let llfn = self.declare_cfn(name, llvm::UnnamedAddr::Global, fty);
+                    let llfn = self.declare_cfn(
+                        name,
+                        llvm::UnnamedAddr::Global,
+                        llvm::Visibility::Default,
+                        fty,
+                    );
                     let target_cpu = attributes::target_cpu_attr(self);
                     attributes::apply_to_llfn(llfn, llvm::AttributePlace::Function, &[target_cpu]);
                     llfn
@@ -585,7 +590,13 @@ impl<'ll, 'tcx> MiscMethods<'tcx> for CodegenCx<'ll, 'tcx> {
 
     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", llvm::UnnamedAddr::Global, fn_type))
+            let visibility = if self.sess().target.default_hidden_visibility {
+                llvm::Visibility::Hidden
+            } else {
+                llvm::Visibility::Default
+            };
+
+            Some(self.declare_cfn("main", llvm::UnnamedAddr::Global, visibility, fn_type))
         } else {
             // If the symbol already exists, it is an error: for example, the user wrote
             // #[no_mangle] extern "C" fn main(..) {..}
@@ -615,7 +626,7 @@ impl<'ll> CodegenCx<'ll, '_> {
         } else {
             self.type_variadic_func(&[], ret)
         };
-        let f = self.declare_cfn(name, llvm::UnnamedAddr::No, fn_ty);
+        let f = self.declare_cfn(name, llvm::UnnamedAddr::No, llvm::Visibility::Default, fn_ty);
         self.intrinsics.borrow_mut().insert(name, (fn_ty, f));
         (fn_ty, f)
     }

compiler/rustc_codegen_llvm/src/declare.rs

@@ -32,6 +32,7 @@ fn declare_raw_fn<'ll>(
     name: &str,
     callconv: llvm::CallConv,
     unnamed: llvm::UnnamedAddr,
+    visibility: llvm::Visibility,
     ty: &'ll Type,
 ) -> &'ll Value {
     debug!("declare_raw_fn(name={:?}, ty={:?})", name, ty);
@@ -41,6 +42,7 @@ fn declare_raw_fn<'ll>(
 
     llvm::SetFunctionCallConv(llfn, callconv);
     llvm::SetUnnamedAddress(llfn, unnamed);
+    llvm::SetVisibility(llfn, visibility);
 
     let mut attrs = SmallVec::<[_; 4]>::new();
 
@@ -76,9 +78,10 @@ impl<'ll, 'tcx> CodegenCx<'ll, 'tcx> {
         &self,
         name: &str,
         unnamed: llvm::UnnamedAddr,
+        visibility: llvm::Visibility,
         fn_type: &'ll Type,
     ) -> &'ll Value {
-        declare_raw_fn(self, name, llvm::CCallConv, unnamed, fn_type)
+        declare_raw_fn(self, name, llvm::CCallConv, unnamed, visibility, fn_type)
     }
 
     /// Declare a Rust function.
@@ -95,6 +98,7 @@ impl<'ll, 'tcx> CodegenCx<'ll, 'tcx> {
             name,
             fn_abi.llvm_cconv(),
             llvm::UnnamedAddr::Global,
+            llvm::Visibility::Default,
             fn_abi.llvm_type(self),
         );
         fn_abi.apply_attrs_llfn(self, llfn);

compiler/rustc_codegen_llvm/src/intrinsic.rs

@@ -1216,7 +1216,7 @@ fn generic_simd_intrinsic<'ll, 'tcx>(
             _ => return_error!("unrecognized intrinsic `{}`", name),
         };
         let llvm_name = &format!("llvm.{0}.v{1}{2}", intr_name, in_len, elem_ty_str);
-        let f = bx.declare_cfn(llvm_name, llvm::UnnamedAddr::No, fn_ty);
+        let f = bx.declare_cfn(llvm_name, llvm::UnnamedAddr::No, llvm::Visibility::Default, fn_ty);
         let c =
             bx.call(fn_ty, f, &args.iter().map(|arg| arg.immediate()).collect::<Vec<_>>(), None);
         Ok(c)
@@ -1416,7 +1416,12 @@ fn generic_simd_intrinsic<'ll, 'tcx>(
             &[llvm_pointer_vec_ty, alignment_ty, mask_ty, llvm_elem_vec_ty],
             llvm_elem_vec_ty,
         );
-        let f = bx.declare_cfn(&llvm_intrinsic, llvm::UnnamedAddr::No, fn_ty);
+        let f = bx.declare_cfn(
+            &llvm_intrinsic,
+            llvm::UnnamedAddr::No,
+            llvm::Visibility::Default,
+            fn_ty,
+        );
         let v =
             bx.call(fn_ty, f, &[args[1].immediate(), alignment, mask, args[0].immediate()], None);
         return Ok(v);
@@ -1542,7 +1547,12 @@ fn generic_simd_intrinsic<'ll, 'tcx>(
             format!("llvm.masked.scatter.{}.{}", llvm_elem_vec_str, llvm_pointer_vec_str);
         let fn_ty =
             bx.type_func(&[llvm_elem_vec_ty, llvm_pointer_vec_ty, alignment_ty, mask_ty], ret_t);
-        let f = bx.declare_cfn(&llvm_intrinsic, llvm::UnnamedAddr::No, fn_ty);
+        let f = bx.declare_cfn(
+            &llvm_intrinsic,
+            llvm::UnnamedAddr::No,
+            llvm::Visibility::Default,
+            fn_ty,
+        );
         let v =
             bx.call(fn_ty, f, &[args[0].immediate(), args[1].immediate(), alignment, mask], None);
         return Ok(v);
@@ -1991,7 +2001,8 @@ unsupported {} from `{}` with element `{}` of size `{}` to `{}`"#,
         let vec_ty = bx.cx.type_vector(elem_ty, in_len as u64);
 
         let fn_ty = bx.type_func(&[vec_ty, vec_ty], vec_ty);
-        let f = bx.declare_cfn(llvm_intrinsic, llvm::UnnamedAddr::No, fn_ty);
+        let f =
+            bx.declare_cfn(llvm_intrinsic, llvm::UnnamedAddr::No, llvm::Visibility::Default, fn_ty);
         let v = bx.call(fn_ty, f, &[lhs, rhs], None);
         return Ok(v);
     }

compiler/rustc_codegen_llvm/src/llvm/mod.rs

@@ -172,6 +172,12 @@ pub fn SetUnnamedAddress(global: &Value, unnamed: UnnamedAddr) {
     }
 }
 
+pub fn SetVisibility(global: &Value, visibility: Visibility) {
+    unsafe {
+        LLVMRustSetVisibility(global, visibility);
+    }
+}
+
 pub fn set_thread_local_mode(global: &Value, mode: ThreadLocalMode) {
     unsafe {
         LLVMSetThreadLocalMode(global, mode);