diff --git a/src/libcompiler_builtins/Cargo.toml b/src/libcompiler_builtins/Cargo.toml
index a52873fc326..9e91e390a57 100644
--- a/src/libcompiler_builtins/Cargo.toml
+++ b/src/libcompiler_builtins/Cargo.toml
@@ -7,6 +7,7 @@ version = "0.0.0"
 [lib]
 name = "compiler_builtins"
 path = "lib.rs"
+test = false
 
 [dependencies]
 core = { path = "../libcore" }
diff --git a/src/librustc_llvm/ffi.rs b/src/librustc_llvm/ffi.rs
index 78a9d67ed77..8f21bf32c9e 100644
--- a/src/librustc_llvm/ffi.rs
+++ b/src/librustc_llvm/ffi.rs
@@ -426,6 +426,14 @@ pub type OperandBundleDefRef = *mut OperandBundleDef_opaque;
 pub type DiagnosticHandler = unsafe extern "C" fn(DiagnosticInfoRef, *mut c_void);
 pub type InlineAsmDiagHandler = unsafe extern "C" fn(SMDiagnosticRef, *const c_void, c_uint);
 
+/// LLVMVisibility
+#[repr(C)]
+pub enum Visibility {
+    Default,
+    Hidden,
+    Protected,
+}
+
 pub mod debuginfo {
     pub use self::DIDescriptorFlags::*;
     use super::MetadataRef;
@@ -746,8 +754,8 @@ extern "C" {
     pub fn LLVMRustSetLinkage(Global: ValueRef, RustLinkage: Linkage);
     pub fn LLVMGetSection(Global: ValueRef) -> *const c_char;
     pub fn LLVMSetSection(Global: ValueRef, Section: *const c_char);
-    pub fn LLVMGetVisibility(Global: ValueRef) -> c_uint;
-    pub fn LLVMSetVisibility(Global: ValueRef, Viz: c_uint);
+    pub fn LLVMGetVisibility(Global: ValueRef) -> Visibility;
+    pub fn LLVMSetVisibility(Global: ValueRef, Viz: Visibility);
     pub fn LLVMGetAlignment(Global: ValueRef) -> c_uint;
     pub fn LLVMSetAlignment(Global: ValueRef, Bytes: c_uint);
     pub fn LLVMSetDLLStorageClass(V: ValueRef, C: DLLStorageClass);
diff --git a/src/librustc_trans/declare.rs b/src/librustc_trans/declare.rs
index 662e3bec66d..7d6a672077a 100644
--- a/src/librustc_trans/declare.rs
+++ b/src/librustc_trans/declare.rs
@@ -19,6 +19,7 @@
 //!   interested in defining the ValueRef they return.
 //! * Use define_* family of methods when you might be defining the ValueRef.
 //! * When in doubt, define.
+
 use llvm::{self, ValueRef};
 use llvm::AttributePlace::Function;
 use rustc::ty;
@@ -28,6 +29,7 @@ use context::CrateContext;
 use common;
 use type_::Type;
 use value::Value;
+use syntax::attr;
 
 use std::ffi::CString;
 
@@ -70,6 +72,16 @@ fn declare_raw_fn(ccx: &CrateContext, name: &str, callconv: llvm::CallConv, ty:
         llvm::Attribute::NoRedZone.apply_llfn(Function, llfn);
     }
 
+    // If we're compiling the compiler-builtins crate, e.g. the equivalent of
+    // compiler-rt, then we want to implicitly compile everything with hidden
+    // visibility as we're going to link this object all over the place but
+    // don't want the symbols to get exported.
+    if attr::contains_name(ccx.tcx().map.krate_attrs(), "compiler_builtins") {
+        unsafe {
+            llvm::LLVMSetVisibility(llfn, llvm::Visibility::Hidden);
+        }
+    }
+
     match ccx.tcx().sess.opts.cg.opt_level.as_ref().map(String::as_ref) {
         Some("s") => {
             llvm::Attribute::OptimizeForSize.apply_llfn(Function, llfn);