diff --git a/src/librustc_codegen_llvm/callee.rs b/src/librustc_codegen_llvm/callee.rs
index 153e300a5232e..fff0177c94842 100644
--- a/src/librustc_codegen_llvm/callee.rs
+++ b/src/librustc_codegen_llvm/callee.rs
@@ -91,7 +91,7 @@ pub fn get_fn(
             llfn
         }
     } else {
-        let llfn = declare::declare_fn(cx, &sym, fn_ty, instance.is_vtable_shim());
+        let llfn = declare::declare_fn(cx, &sym, common::ty_fn_sig_vtable(cx, fn_ty, instance.is_vtable_shim()));
         assert_eq!(common::val_ty(llfn), llptrty);
         debug!("get_fn: not casting pointer!");
 
diff --git a/src/librustc_codegen_llvm/context.rs b/src/librustc_codegen_llvm/context.rs
index 8087f130afaa0..241f7989e1681 100644
--- a/src/librustc_codegen_llvm/context.rs
+++ b/src/librustc_codegen_llvm/context.rs
@@ -404,15 +404,15 @@ impl<'b, 'tcx> CodegenCx<'b, 'tcx> {
             return llfn;
         }
 
-        let ty = tcx.mk_fn_ptr(ty::Binder::bind(tcx.mk_fn_sig(
+        let sig = ty::Binder::bind(tcx.mk_fn_sig(
             iter::once(tcx.mk_mut_ptr(tcx.types.u8)),
             tcx.types.never,
             false,
             hir::Unsafety::Unsafe,
             Abi::C
-        )));
+        ));
 
-        let llfn = declare::declare_fn(self, "rust_eh_unwind_resume", ty, false);
+        let llfn = declare::declare_fn(self, "rust_eh_unwind_resume", sig);
         attributes::unwind(llfn, true);
         attributes::apply_target_cpu_attr(self, llfn);
         unwresume.set(Some(llfn));
diff --git a/src/librustc_codegen_llvm/declare.rs b/src/librustc_codegen_llvm/declare.rs
index 0d01e9ef7ddab..f4aede55ce1a6 100644
--- a/src/librustc_codegen_llvm/declare.rs
+++ b/src/librustc_codegen_llvm/declare.rs
@@ -22,7 +22,7 @@
 
 use llvm;
 use llvm::AttributePlace::Function;
-use rustc::ty::{self, Ty};
+use rustc::ty::{self, PolyFnSig};
 use rustc::ty::layout::LayoutOf;
 use rustc::session::config::Sanitizer;
 use rustc_data_structures::small_c_str::SmallCStr;
@@ -30,7 +30,6 @@ use rustc_target::spec::PanicStrategy;
 use abi::{Abi, FnType, FnTypeExt};
 use attributes;
 use context::CodegenCx;
-use common;
 use type_::Type;
 use value::Value;
 
@@ -129,12 +128,9 @@ pub fn declare_cfn(cx: &CodegenCx<'ll, '_>, name: &str, fn_type: &'ll Type) -> &
 pub fn declare_fn(
     cx: &CodegenCx<'ll, 'tcx>,
     name: &str,
-    fn_type: Ty<'tcx>,
-    is_vtable_shim: bool,
+    sig: PolyFnSig<'tcx>,
 ) -> &'ll Value {
-    debug!("declare_rust_fn(name={:?}, fn_type={:?}, is_vtable_shim={:?})",
-           name, fn_type, is_vtable_shim);
-    let sig = common::ty_fn_sig_vtable(cx, fn_type, is_vtable_shim);
+    debug!("declare_rust_fn(name={:?}, sig={:?})", name, sig);
     let sig = cx.tcx.normalize_erasing_late_bound_regions(ty::ParamEnv::reveal_all(), &sig);
     debug!("declare_rust_fn (after region erasure) sig={:?}", sig);
 
@@ -186,12 +182,12 @@ pub fn define_private_global(cx: &CodegenCx<'ll, '_>, ty: &'ll Type) -> &'ll Val
 pub fn define_fn(
     cx: &CodegenCx<'ll, 'tcx>,
     name: &str,
-    fn_type: Ty<'tcx>,
+    fn_sig: PolyFnSig<'tcx>,
 ) -> &'ll Value {
     if get_defined_value(cx, name).is_some() {
         cx.sess().fatal(&format!("symbol `{}` already defined", name))
     } else {
-        declare_fn(cx, name, fn_type, false)
+        declare_fn(cx, name, fn_sig)
     }
 }
 
@@ -203,9 +199,9 @@ pub fn define_fn(
 pub fn define_internal_fn(
     cx: &CodegenCx<'ll, 'tcx>,
     name: &str,
-    fn_type: Ty<'tcx>,
+    fn_sig: PolyFnSig<'tcx>,
 ) -> &'ll Value {
-    let llfn = define_fn(cx, name, fn_type);
+    let llfn = define_fn(cx, name, fn_sig);
     unsafe { llvm::LLVMRustSetLinkage(llfn, llvm::Linkage::InternalLinkage) };
     llfn
 }
diff --git a/src/librustc_codegen_llvm/intrinsic.rs b/src/librustc_codegen_llvm/intrinsic.rs
index 272196afa6f92..03244c18ac3e4 100644
--- a/src/librustc_codegen_llvm/intrinsic.rs
+++ b/src/librustc_codegen_llvm/intrinsic.rs
@@ -933,14 +933,14 @@ fn gen_fn<'ll, 'tcx>(
     output: Ty<'tcx>,
     codegen: &mut dyn FnMut(Builder<'_, 'll, 'tcx>),
 ) -> &'ll Value {
-    let rust_fn_ty = cx.tcx.mk_fn_ptr(ty::Binder::bind(cx.tcx.mk_fn_sig(
+    let rust_fn_sig = ty::Binder::bind(cx.tcx.mk_fn_sig(
         inputs.into_iter(),
         output,
         false,
         hir::Unsafety::Unsafe,
         Abi::Rust
-    )));
-    let llfn = declare::define_internal_fn(cx, name, rust_fn_ty);
+    ));
+    let llfn = declare::define_internal_fn(cx, name, rust_fn_sig);
     attributes::from_fn_attrs(cx, llfn, None);
     let bx = Builder::new_block(cx, llfn, "entry-block");
     codegen(bx);
diff --git a/src/librustc_codegen_llvm/mono_item.rs b/src/librustc_codegen_llvm/mono_item.rs
index aab8613b75619..d160f114d4ccd 100644
--- a/src/librustc_codegen_llvm/mono_item.rs
+++ b/src/librustc_codegen_llvm/mono_item.rs
@@ -17,6 +17,7 @@
 use asm;
 use attributes;
 use base;
+use common;
 use consts;
 use context::CodegenCx;
 use declare;
@@ -154,8 +155,9 @@ fn predefine_fn<'a, 'tcx>(cx: &CodegenCx<'a, 'tcx>,
             !instance.substs.has_param_types());
 
     let mono_ty = instance.ty(cx.tcx);
+    let mono_sig = common::ty_fn_sig_vtable(cx, mono_ty, instance.is_vtable_shim());
     let attrs = cx.tcx.codegen_fn_attrs(instance.def_id());
-    let lldecl = declare::declare_fn(cx, symbol_name, mono_ty, instance.is_vtable_shim());
+    let lldecl = declare::declare_fn(cx, symbol_name, mono_sig);
     unsafe { llvm::LLVMRustSetLinkage(lldecl, base::linkage_to_llvm(linkage)) };
     base::set_link_section(lldecl, &attrs);
     if linkage == Linkage::LinkOnceODR ||