diff --git a/src/librustc_trans/common.rs b/src/librustc_trans/common.rs
index eb6ea8fa94b0a..419267cb269c9 100644
--- a/src/librustc_trans/common.rs
+++ b/src/librustc_trans/common.rs
@@ -45,37 +45,30 @@ use rustc_i128::u128;
 pub use context::{CrateContext, SharedCrateContext};
 
 pub fn type_is_fat_ptr<'a, 'tcx>(ccx: &CrateContext<'a, 'tcx>, ty: Ty<'tcx>) -> bool {
-    match ty.sty {
-        ty::TyRawPtr(ty::TypeAndMut{ty, ..}) |
-        ty::TyRef(_, ty::TypeAndMut{ty, ..}) |
-        ty::TyBox(ty) => {
-            !ccx.shared().type_is_sized(ty)
-        }
-        _ => {
-            false
-        }
+    if let Layout::FatPointer { .. } = *ccx.layout_of(ty) {
+        true
+    } else {
+        false
     }
 }
 
 pub fn type_is_immediate<'a, 'tcx>(ccx: &CrateContext<'a, 'tcx>, ty: Ty<'tcx>) -> bool {
-    use machine::llsize_of_alloc;
-    use type_of::sizing_type_of;
-
-    let simple = ty.is_scalar() ||
-        ty.is_unique() || ty.is_region_ptr() ||
-        ty.is_simd();
-    if simple && !type_is_fat_ptr(ccx, ty) {
-        return true;
-    }
-    if !ccx.shared().type_is_sized(ty) {
-        return false;
-    }
-    match ty.sty {
-        ty::TyAdt(..) | ty::TyTuple(..) | ty::TyArray(..) | ty::TyClosure(..) => {
-            let llty = sizing_type_of(ccx, ty);
-            llsize_of_alloc(ccx, llty) <= llsize_of_alloc(ccx, ccx.int_type())
+    let layout = ccx.layout_of(ty);
+    match *layout {
+        Layout::CEnum { .. } |
+        Layout::Scalar { .. } |
+        Layout::Vector { .. } => true,
+
+        Layout::FatPointer { .. } => false,
+
+        Layout::Array { .. } |
+        Layout::Univariant { .. } |
+        Layout::General { .. } |
+        Layout::UntaggedUnion { .. } |
+        Layout::RawNullablePointer { .. } |
+        Layout::StructWrappedNullablePointer { .. } => {
+            !layout.is_unsized() && layout.size(&ccx.tcx().data_layout).bytes() == 0
         }
-        _ => type_is_zero_size(ccx, ty)
     }
 }
 
diff --git a/src/librustc_trans/mir/rvalue.rs b/src/librustc_trans/mir/rvalue.rs
index 67fb8cf576d62..1b97a8d010cfe 100644
--- a/src/librustc_trans/mir/rvalue.rs
+++ b/src/librustc_trans/mir/rvalue.rs
@@ -260,22 +260,9 @@ impl<'a, 'tcx> MirContext<'a, 'tcx> {
                         let r_t_out = CastTy::from_ty(cast_ty).expect("bad output type for cast");
                         let ll_t_in = type_of::immediate_type_of(bcx.ccx, operand.ty);
                         let ll_t_out = type_of::immediate_type_of(bcx.ccx, cast_ty);
-                        let (llval, signed) = if let CastTy::Int(IntTy::CEnum) = r_t_in {
-                            let l = bcx.ccx.layout_of(operand.ty);
-                            let discr = match operand.val {
-                                OperandValue::Immediate(llval) => llval,
-                                OperandValue::Ref(llptr) => {
-                                    adt::trans_get_discr(&bcx, operand.ty, llptr, None, true)
-                                }
-                                OperandValue::Pair(..) => bug!("Unexpected Pair operand")
-                            };
-                            let (signed, min, max) = match l {
-                                &Layout::CEnum { signed, min, max, .. } => {
-                                    (signed, min, max)
-                                }
-                                _ => bug!("CEnum {:?} is not an enum", operand)
-                            };
-
+                        let llval = operand.immediate();
+                        let l = bcx.ccx.layout_of(operand.ty);
+                        let signed = if let Layout::CEnum { signed, min, max, .. } = *l {
                             if max > min {
                                 // We want `table[e as usize]` to not
                                 // have bound checks, and this is the most
@@ -283,14 +270,14 @@ impl<'a, 'tcx> MirContext<'a, 'tcx> {
 
                                 base::call_assume(&bcx, bcx.icmp(
                                     llvm::IntULE,
-                                    discr,
-                                    C_integral(common::val_ty(discr), max, false)
-                                ))
+                                    llval,
+                                    C_integral(common::val_ty(llval), max, false)
+                                ));
                             }
 
-                            (discr, signed)
+                            signed
                         } else {
-                            (operand.immediate(), operand.ty.is_signed())
+                            operand.ty.is_signed()
                         };
 
                         let newval = match (r_t_in, r_t_out) {