diff --git a/src/librustc/ty/layout.rs b/src/librustc/ty/layout.rs
index 972452601ddd5..b9fc5f59b7bbc 100644
--- a/src/librustc/ty/layout.rs
+++ b/src/librustc/ty/layout.rs
@@ -697,7 +697,7 @@ impl<'tcx> LayoutCx<'tcx, TyCtxt<'tcx>> {
             // SIMD vector types.
             ty::Adt(def, ..) if def.repr.simd() => {
                 let element = self.layout_of(ty.simd_type(tcx))?;
-                let count = ty.simd_size(tcx) as u64;
+                let count = ty.simd_size(tcx);
                 assert!(count > 0);
                 let scalar = match element.abi {
                     Abi::Scalar(ref scalar) => scalar.clone(),
diff --git a/src/librustc/ty/sty.rs b/src/librustc/ty/sty.rs
index 8f6fc02ab4b37..b7e645d55a5fc 100644
--- a/src/librustc/ty/sty.rs
+++ b/src/librustc/ty/sty.rs
@@ -1814,20 +1814,30 @@ impl<'tcx> TyS<'tcx> {
 
     pub fn simd_type(&self, tcx: TyCtxt<'tcx>) -> Ty<'tcx> {
         match self.kind {
-            Adt(def, substs) => {
-                def.non_enum_variant().fields[0].ty(tcx, substs)
-            }
+            Adt(def, substs) => def.non_enum_variant().fields[0].ty(tcx, substs),
             _ => bug!("simd_type called on invalid type")
         }
     }
 
-    pub fn simd_size(&self, _cx: TyCtxt<'_>) -> usize {
+    pub fn simd_size(&self, _tcx: TyCtxt<'tcx>) -> u64 {
+        // Parameter currently unused, but probably needed in the future to
+        // allow `#[repr(simd)] struct Simd<T, const N: usize>([T; N]);`.
         match self.kind {
-            Adt(def, _) => def.non_enum_variant().fields.len(),
+            Adt(def, _) => def.non_enum_variant().fields.len() as u64,
             _ => bug!("simd_size called on invalid type")
         }
     }
 
+    pub fn simd_size_and_type(&self, tcx: TyCtxt<'tcx>) -> (u64, Ty<'tcx>) {
+        match self.kind {
+            Adt(def, substs) => {
+                let variant = def.non_enum_variant();
+                (variant.fields.len() as u64, variant.fields[0].ty(tcx, substs))
+            }
+            _ => bug!("simd_size_and_type called on invalid type")
+        }
+    }
+
     #[inline]
     pub fn is_region_ptr(&self) -> bool {
         match self.kind {
diff --git a/src/librustc_codegen_llvm/intrinsic.rs b/src/librustc_codegen_llvm/intrinsic.rs
index e1ce7f622e2ef..4277ce1d1f754 100644
--- a/src/librustc_codegen_llvm/intrinsic.rs
+++ b/src/librustc_codegen_llvm/intrinsic.rs
@@ -1105,8 +1105,8 @@ fn generic_simd_intrinsic(
         let m_len = match in_ty.kind {
             // Note that this `.unwrap()` crashes for isize/usize, that's sort
             // of intentional as there's not currently a use case for that.
-            ty::Int(i) => i.bit_width().unwrap(),
-            ty::Uint(i) => i.bit_width().unwrap(),
+            ty::Int(i) => i.bit_width().unwrap() as u64,
+            ty::Uint(i) => i.bit_width().unwrap() as u64,
             _ => return_error!("`{}` is not an integral type", in_ty),
         };
         require_simd!(arg_tys[1], "argument");
@@ -1116,7 +1116,7 @@ fn generic_simd_intrinsic(
                  m_len, v_len
         );
         let i1 = bx.type_i1();
-        let i1xn = bx.type_vector(i1, m_len as u64);
+        let i1xn = bx.type_vector(i1, m_len);
         let m_i1s = bx.bitcast(args[0].immediate(), i1xn);
         return Ok(bx.select(m_i1s, args[1].immediate(), args[2].immediate()));
     }
@@ -1160,7 +1160,7 @@ fn generic_simd_intrinsic(
     }
 
     if name.starts_with("simd_shuffle") {
-        let n: usize = name["simd_shuffle".len()..].parse().unwrap_or_else(|_|
+        let n: u64 = name["simd_shuffle".len()..].parse().unwrap_or_else(|_|
             span_bug!(span, "bad `simd_shuffle` instruction only caught in codegen?"));
 
         require_simd!(ret_ty, "return");
@@ -1175,7 +1175,7 @@ fn generic_simd_intrinsic(
                  in_elem, in_ty,
                  ret_ty, ret_ty.simd_type(tcx));
 
-        let total_len = in_len as u128 * 2;
+        let total_len = u128::from(in_len) * 2;
 
         let vector = args[2].immediate();
 
@@ -1251,7 +1251,7 @@ fn generic_simd_intrinsic(
         // trailing bits.
         let expected_int_bits = in_len.max(8);
         match ret_ty.kind {
-           ty::Uint(i) if i.bit_width() == Some(expected_int_bits) => (),
+           ty::Uint(i) if i.bit_width() == Some(expected_int_bits as usize) => (),
             _ => return_error!(
                 "bitmask `{}`, expected `u{}`",
                 ret_ty, expected_int_bits
@@ -1276,7 +1276,8 @@ fn generic_simd_intrinsic(
 
         // Shift the MSB to the right by "in_elem_bitwidth - 1" into the first bit position.
         let shift_indices = vec![
-            bx.cx.const_int(bx.type_ix(in_elem_bitwidth as _), (in_elem_bitwidth - 1) as _); in_len
+            bx.cx.const_int(bx.type_ix(in_elem_bitwidth as _), (in_elem_bitwidth - 1) as _);
+            in_len as _
         ];
         let i_xn_msb = bx.lshr(i_xn, bx.const_vector(shift_indices.as_slice()));
         // Truncate vector to an <i1 x N>
@@ -1291,7 +1292,7 @@ fn generic_simd_intrinsic(
         name: &str,
         in_elem: &::rustc::ty::TyS<'_>,
         in_ty: &::rustc::ty::TyS<'_>,
-        in_len: usize,
+        in_len: u64,
         bx: &mut Builder<'a, 'll, 'tcx>,
         span: Span,
         args: &[OperandRef<'tcx, &'ll Value>],
@@ -1400,7 +1401,7 @@ fn generic_simd_intrinsic(
     // FIXME: use:
     //  https://github.com/llvm-mirror/llvm/blob/master/include/llvm/IR/Function.h#L182
     //  https://github.com/llvm-mirror/llvm/blob/master/include/llvm/IR/Intrinsics.h#L81
-    fn llvm_vector_str(elem_ty: Ty<'_>, vec_len: usize, no_pointers: usize) -> String {
+    fn llvm_vector_str(elem_ty: Ty<'_>, vec_len: u64, no_pointers: usize) -> String {
         let p0s: String = "p0".repeat(no_pointers);
         match elem_ty.kind {
             ty::Int(v) => format!("v{}{}i{}", vec_len, p0s, v.bit_width().unwrap()),
@@ -1410,7 +1411,7 @@ fn generic_simd_intrinsic(
         }
     }
 
-    fn llvm_vector_ty(cx: &CodegenCx<'ll, '_>, elem_ty: Ty<'_>, vec_len: usize,
+    fn llvm_vector_ty(cx: &CodegenCx<'ll, '_>, elem_ty: Ty<'_>, vec_len: u64,
                       mut no_pointers: usize) -> &'ll Type {
         // FIXME: use cx.layout_of(ty).llvm_type() ?
         let mut elem_ty = match elem_ty.kind {
@@ -1423,7 +1424,7 @@ fn generic_simd_intrinsic(
             elem_ty = cx.type_ptr_to(elem_ty);
             no_pointers -= 1;
         }
-        cx.type_vector(elem_ty, vec_len as u64)
+        cx.type_vector(elem_ty, vec_len)
     }
 
 
@@ -1506,7 +1507,7 @@ fn generic_simd_intrinsic(
         // Truncate the mask vector to a vector of i1s:
         let (mask, mask_ty) = {
             let i1 = bx.type_i1();
-            let i1xn = bx.type_vector(i1, in_len as u64);
+            let i1xn = bx.type_vector(i1, in_len);
             (bx.trunc(args[2].immediate(), i1xn), i1xn)
         };
 
@@ -1606,7 +1607,7 @@ fn generic_simd_intrinsic(
         // Truncate the mask vector to a vector of i1s:
         let (mask, mask_ty) = {
             let i1 = bx.type_i1();
-            let i1xn = bx.type_vector(i1, in_len as u64);
+            let i1xn = bx.type_vector(i1, in_len);
             (bx.trunc(args[2].immediate(), i1xn), i1xn)
         };
 
diff --git a/src/librustc_mir/interpret/intrinsics.rs b/src/librustc_mir/interpret/intrinsics.rs
index 6117cf4038a24..23f7b1acb54d4 100644
--- a/src/librustc_mir/interpret/intrinsics.rs
+++ b/src/librustc_mir/interpret/intrinsics.rs
@@ -302,10 +302,10 @@ impl<'mir, 'tcx, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
                 self.copy_op_transmute(args[0], dest)?;
             }
             "simd_insert" => {
-                let index = self.read_scalar(args[1])?.to_u32()? as u64;
-                let scalar = args[2];
+                let index = u64::from(self.read_scalar(args[1])?.to_u32()?);
+                let elem = args[2];
                 let input = args[0];
-                let (len, e_ty) = self.read_vector_ty(input);
+                let (len, e_ty) = input.layout.ty.simd_size_and_type(self.tcx.tcx);
                 assert!(
                     index < len,
                     "Index `{}` must be in bounds of vector type `{}`: `[0, {})`",
@@ -317,15 +317,15 @@ impl<'mir, 'tcx, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
                     dest.layout.ty, input.layout.ty
                 );
                 assert_eq!(
-                    scalar.layout.ty, e_ty,
-                    "Scalar type `{}` must match vector element type `{}`",
-                    scalar.layout.ty, e_ty
+                    elem.layout.ty, e_ty,
+                    "Scalar element type `{}` must match vector element type `{}`",
+                    elem.layout.ty, e_ty
                 );
 
                 for i in 0..len {
                     let place = self.place_field(dest, i)?;
                     let value = if i == index {
-                        scalar
+                        elem
                     } else {
                         self.operand_field(input, i)?
                     };
@@ -333,8 +333,8 @@ impl<'mir, 'tcx, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
                 }
             }
             "simd_extract" => {
-                let index = self.read_scalar(args[1])?.to_u32()? as _;
-                let (len, e_ty) = self.read_vector_ty(args[0]);
+                let index = u64::from(self.read_scalar(args[1])?.to_u32()?);
+                let (len, e_ty) = args[0].layout.ty.simd_size_and_type(self.tcx.tcx);
                 assert!(
                     index < len,
                     "index `{}` is out-of-bounds of vector type `{}` with length `{}`",
diff --git a/src/librustc_mir/interpret/operand.rs b/src/librustc_mir/interpret/operand.rs
index 4d2ccdc20da65..970f76a9d6d7c 100644
--- a/src/librustc_mir/interpret/operand.rs
+++ b/src/librustc_mir/interpret/operand.rs
@@ -315,17 +315,6 @@ impl<'mir, 'tcx, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
         }
     }
 
-    /// Read vector length and element type
-    pub fn read_vector_ty(
-        &self, op: OpTy<'tcx, M::PointerTag>
-    ) -> (u64, &rustc::ty::TyS<'tcx>) {
-        if let layout::Abi::Vector { .. } = op.layout.abi {
-            (op.layout.ty.simd_size(*self.tcx) as _, op.layout.ty.simd_type(*self.tcx))
-        } else {
-            bug!("Type `{}` is not a SIMD vector type", op.layout.ty)
-        }
-    }
-
     /// Read a scalar from a place
     pub fn read_scalar(
         &self,
diff --git a/src/librustc_mir/interpret/terminator.rs b/src/librustc_mir/interpret/terminator.rs
index 4f9e404b2c635..50c4a249c63c2 100644
--- a/src/librustc_mir/interpret/terminator.rs
+++ b/src/librustc_mir/interpret/terminator.rs
@@ -264,6 +264,8 @@ impl<'mir, 'tcx, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
 
         match instance.def {
             ty::InstanceDef::Intrinsic(..) => {
+                assert!(caller_abi == Abi::RustIntrinsic || caller_abi == Abi::PlatformIntrinsic);
+
                 let old_stack = self.cur_frame();
                 let old_bb = self.frame().block;
                 M::call_intrinsic(self, span, instance, args, dest, ret, unwind)?;