librustc: Separate NullablePointer into RawNullablePointer and Struct…

…WrappedNullablePointer.

src/librustc/middle/trans/adt.rs

@@ -85,20 +85,30 @@ pub enum Repr {
      * all start with a field for the discriminant.
      */
     General(IntType, Vec<Struct>),
+    /**
+     * Two cases distinguished by a nullable pointer: the case with discriminant
+     * `nndiscr` must have single field which is known to be nonnull due to its type.
+     * The other case is known to be zero sized. Hence we represent the enum
+     * as simply a nullable pointer: if not null it indicates the `nndiscr` variant,
+     * otherwise it indicates the other case.
+     */
+    RawNullablePointer {
+        pub nndiscr: Disr,
+        pub nnty: ty::t,
+        pub nullfields: Vec<ty::t>
+    },
     /**
      * Two cases distinguished by a nullable pointer: the case with discriminant
      * `nndiscr` is represented by the struct `nonnull`, where the `ptrfield`th
      * field is known to be nonnull due to its type; if that field is null, then
      * it represents the other case, which is inhabited by at most one value
      * (and all other fields are undefined/unused).
-     * If the case with the nullable pointer has a single field then we don't
-     * wrap it in a struct and instead just deal with it directly as a pointer.
      *
      * For example, `std::option::Option` instantiated at a safe pointer type
      * is represented such that `None` is a null pointer and `Some` is the
      * identity function.
      */
-    NullablePointer {
+    StructWrappedNullablePointer {
         pub nonnull: Struct,
         pub nndiscr: Disr,
         pub ptrfield: uint,
@@ -202,17 +212,23 @@ fn represent_type_uncached(cx: &CrateContext, t: ty::t) -> Repr {
                     if cases.get(1 - discr).is_zerolen(cx) {
                         match cases.get(discr).find_ptr() {
                             Some(ptrfield) => {
-                                return NullablePointer {
-                                    nndiscr: discr as u64,
-                                    nonnull: mk_struct(cx,
-                                                       cases.get(discr)
-                                                            .tys
-                                                            .as_slice(),
-                                                       false),
-                                    ptrfield: ptrfield,
-                                    nullfields: cases.get(1 - discr).tys
-                                                                    .clone()
-                                }
+                                let st = mk_struct(cx, cases.get(discr).tys.as_slice(),
+                                                   false);
+
+                                return if st.fields.len() == 1 {
+                                    RawNullablePointer {
+                                        nndiscr: discr as Disr,
+                                        nnty: *st.fields.get(0),
+                                        nullfields: cases.get(1 - discr).tys.clone()
+                                    }
+                                } else {
+                                    StructWrappedNullablePointer {
+                                        nndiscr: discr as Disr,
+                                        nonnull: st,
+                                        ptrfield: ptrfield,
+                                        nullfields: cases.get(1 - discr).tys.clone()
+                                    }
+                                };
                             }
                             None => { }
                         }
@@ -415,11 +431,8 @@ pub fn incomplete_type_of(cx: &CrateContext, r: &Repr, name: &str) -> Type {
 }
 pub fn finish_type_of(cx: &CrateContext, r: &Repr, llty: &mut Type) {
     match *r {
-        CEnum(..) | General(..) => {
-        }
-        NullablePointer { nonnull: ref st, .. } if st.fields.len() == 1 => {
-        }
-        Univariant(ref st, _) | NullablePointer { nonnull: ref st, .. } =>
+        CEnum(..) | General(..) | RawNullablePointer { .. } => { }
+        Univariant(ref st, _) | StructWrappedNullablePointer { nonnull: ref st, .. } =>
             llty.set_struct_body(struct_llfields(cx, st, false).as_slice(),
                                  st.packed)
     }
@@ -428,14 +441,8 @@ pub fn finish_type_of(cx: &CrateContext, r: &Repr, llty: &mut Type) {
 fn generic_type_of(cx: &CrateContext, r: &Repr, name: Option<&str>, sizing: bool) -> Type {
     match *r {
         CEnum(ity, _, _) => ll_inttype(cx, ity),
-        NullablePointer { nonnull: ref st, .. } if st.fields.len() == 1 => {
-            if sizing {
-                type_of::sizing_type_of(cx, *st.fields.get(0))
-            } else {
-                type_of::type_of(cx, *st.fields.get(0))
-            }
-        }
-        Univariant(ref st, _) | NullablePointer { nonnull: ref st, .. } => {
+        RawNullablePointer { nnty, .. } => type_of::sizing_type_of(cx, nnty),
+        Univariant(ref st, _) | StructWrappedNullablePointer { nonnull: ref st, .. } => {
             match name {
                 None => {
                     Type::struct_(cx, struct_llfields(cx, st, sizing).as_slice(),
@@ -507,12 +514,10 @@ fn struct_llfields(cx: &CrateContext, st: &Struct, sizing: bool) -> Vec<Type> {
 pub fn trans_switch(bcx: &Block, r: &Repr, scrutinee: ValueRef)
     -> (_match::branch_kind, Option<ValueRef>) {
     match *r {
-        CEnum(..) | General(..) => {
+        CEnum(..) | General(..) |
+        RawNullablePointer { .. } | StructWrappedNullablePointer { .. } => {
             (_match::switch, Some(trans_get_discr(bcx, r, scrutinee, None)))
         }
-        NullablePointer { nonnull: ref nonnull, nndiscr, ptrfield, .. } => {
-            (_match::switch, Some(nullable_bitdiscr(bcx, nonnull, nndiscr, ptrfield, scrutinee)))
-        }
         Univariant(..) => {
             (_match::single, None)
         }
@@ -540,8 +545,14 @@ pub fn trans_get_discr(bcx: &Block, r: &Repr, scrutinee: ValueRef, cast_to: Opti
             val = C_u8(bcx.ccx(), 0);
             signed = false;
         }
-        NullablePointer { nonnull: ref nonnull, nndiscr, ptrfield, .. } => {
-            val = nullable_bitdiscr(bcx, nonnull, nndiscr, ptrfield, scrutinee);
+        RawNullablePointer { nndiscr, nnty, .. } =>  {
+            let cmp = if nndiscr == 0 { IntEQ } else { IntNE };
+            let llptrty = type_of::sizing_type_of(bcx.ccx(), nnty);
+            val = ICmp(bcx, cmp, Load(bcx, scrutinee), C_null(llptrty));
+            signed = false;
+        }
+        StructWrappedNullablePointer { nonnull: ref nonnull, nndiscr, ptrfield, .. } => {
+            val = struct_wrapped_nullable_bitdiscr(bcx, nonnull, nndiscr, ptrfield, scrutinee);
             signed = false;
         }
     }
@@ -551,13 +562,9 @@ pub fn trans_get_discr(bcx: &Block, r: &Repr, scrutinee: ValueRef, cast_to: Opti
     }
 }
 
-fn nullable_bitdiscr(bcx: &Block, nonnull: &Struct, nndiscr: Disr, ptrfield: uint,
-                     scrutinee: ValueRef) -> ValueRef {
-    let llptr = if nonnull.fields.len() == 1 {
-        Load(bcx, scrutinee)
-    } else {
-        Load(bcx, GEPi(bcx, scrutinee, [0, ptrfield]))
-    };
+fn struct_wrapped_nullable_bitdiscr(bcx: &Block, nonnull: &Struct, nndiscr: Disr, ptrfield: uint,
+                                    scrutinee: ValueRef) -> ValueRef {
+    let llptr = Load(bcx, GEPi(bcx, scrutinee, [0, ptrfield]));
     let cmp = if nndiscr == 0 { IntEQ } else { IntNE };
     let llptrty = type_of::type_of(bcx.ccx(), *nonnull.fields.get(ptrfield));
     ICmp(bcx, cmp, llptr, C_null(llptrty))
@@ -606,7 +613,8 @@ pub fn trans_case<'a>(bcx: &'a Block<'a>, r: &Repr, discr: Disr)
         Univariant(..) => {
             bcx.ccx().sess().bug("no cases for univariants or structs")
         }
-        NullablePointer { .. } => {
+        RawNullablePointer { .. } |
+        StructWrappedNullablePointer { .. } => {
             assert!(discr == 0 || discr == 1);
             _match::single_result(Result::new(bcx, C_i1(bcx.ccx(), discr != 0)))
         }
@@ -637,13 +645,15 @@ pub fn trans_start_init(bcx: &Block, r: &Repr, val: ValueRef, discr: Disr) {
         Univariant(..) => {
             assert_eq!(discr, 0);
         }
-        NullablePointer { nonnull: ref nonnull, nndiscr, ptrfield, .. } => {
+        RawNullablePointer { nndiscr, nnty, ..} => {
             if discr != nndiscr {
-                let llptrptr = if nonnull.fields.len() == 1 {
-                    val
-                } else {
-                    GEPi(bcx, val, [0, ptrfield])
-                };
+                let llptrty = type_of::sizing_type_of(bcx.ccx(), nnty);
+                Store(bcx, C_null(llptrty), val)
+            }
+        }
+        StructWrappedNullablePointer { nonnull: ref nonnull, nndiscr, ptrfield, .. } => {
+            if discr != nndiscr {
+                let llptrptr = GEPi(bcx, val, [0, ptrfield]);
                 let llptrty = type_of::type_of(bcx.ccx(),
                                                *nonnull.fields.get(ptrfield));
                 Store(bcx, C_null(llptrty), llptrptr)
@@ -671,8 +681,11 @@ pub fn num_args(r: &Repr, discr: Disr) -> uint {
             st.fields.len() - (if dtor { 1 } else { 0 })
         }
         General(_, ref cases) => cases.get(discr as uint).fields.len() - 1,
-        NullablePointer { nonnull: ref nonnull, nndiscr,
-                         nullfields: ref nullfields, .. } => {
+        RawNullablePointer { nndiscr, ref nullfields, .. } => {
+            if discr == nndiscr { 1 } else { nullfields.len() }
+        }
+        StructWrappedNullablePointer { nonnull: ref nonnull, nndiscr,
+                                       nullfields: ref nullfields, .. } => {
             if discr == nndiscr { nonnull.fields.len() } else { nullfields.len() }
         }
     }
@@ -695,24 +708,25 @@ pub fn trans_field_ptr(bcx: &Block, r: &Repr, val: ValueRef, discr: Disr,
         General(_, ref cases) => {
             struct_field_ptr(bcx, cases.get(discr as uint), val, ix + 1, true)
         }
-        NullablePointer { nonnull: ref nonnull, nullfields: ref nullfields,
-                         nndiscr, .. } => {
-            if discr == nndiscr {
-                if nonnull.fields.len() == 1 {
-                    assert_eq!(ix, 0);
-                    val
-                } else {
-                    struct_field_ptr(bcx, nonnull, val, ix, false)
-                }
-            } else {
-                // The unit-like case might have a nonzero number of unit-like fields.
-                // (e.g., Result or Either with () as one side.)
-                let ty = type_of::type_of(bcx.ccx(), *nullfields.get(ix));
-                assert_eq!(machine::llsize_of_alloc(bcx.ccx(), ty), 0);
-                // The contents of memory at this pointer can't matter, but use
-                // the value that's "reasonable" in case of pointer comparison.
-                PointerCast(bcx, val, ty.ptr_to())
-            }
+        RawNullablePointer { nndiscr, ref nullfields, .. } |
+        StructWrappedNullablePointer { nndiscr, ref nullfields, .. } if discr != nndiscr => {
+            // The unit-like case might have a nonzero number of unit-like fields.
+            // (e.d., Result of Either with (), as one side.)
+            let ty = type_of::type_of(bcx.ccx(), *nullfields.get(ix));
+            assert_eq!(machine::llsize_of_alloc(bcx.ccx(), ty), 0);
+            // The contents of memory at this pointer can't matter, but use
+            // the value that's "reasonable" in case of pointer comparision.
+            PointerCast(bcx, val, ty.ptr_to())
+        }
+        RawNullablePointer { nndiscr, nnty, .. } => {
+            assert_eq!(ix, 0);
+            assert_eq!(discr, nndiscr);
+            let ty = type_of::type_of(bcx.ccx(), nnty);
+            PointerCast(bcx, val, ty.ptr_to())
+        }
+        StructWrappedNullablePointer { ref nonnull, nndiscr, .. } => {
+            assert_eq!(discr, nndiscr);
+            struct_field_ptr(bcx, nonnull, val, ix, false)
         }
     }
 }
@@ -784,15 +798,15 @@ pub fn trans_const(ccx: &CrateContext, r: &Repr, discr: Disr,
             let contents = build_const_struct(ccx, st, vals);
             C_struct(ccx, contents.as_slice(), st.packed)
         }
-        NullablePointer { nonnull: ref st, nndiscr, .. } if st.fields.len() == 1 => {
+        RawNullablePointer { nndiscr, nnty, .. } => {
             if discr == nndiscr {
                 assert_eq!(vals.len(), 1);
                 vals[0]
             } else {
-                C_null(type_of::sizing_type_of(ccx, *st.fields.get(0)))
+                C_null(type_of::sizing_type_of(ccx, nnty))
             }
         }
-        NullablePointer { nonnull: ref nonnull, nndiscr, .. } => {
+        StructWrappedNullablePointer { nonnull: ref nonnull, nndiscr, .. } => {
             if discr == nndiscr {
                 C_struct(ccx, build_const_struct(ccx,
                                                  nonnull,
@@ -900,15 +914,15 @@ pub fn const_get_discrim(ccx: &CrateContext, r: &Repr, val: ValueRef)
             }
         }
         Univariant(..) => 0,
-        NullablePointer { nonnull: ref st, nndiscr, .. } if st.fields.len() == 1 => {
+        RawNullablePointer { nndiscr, .. } => {
             if is_null(val) {
                 /* subtraction as uint is ok because nndiscr is either 0 or 1 */
                 (1 - nndiscr) as Disr
             } else {
                 nndiscr
             }
         }
-        NullablePointer { nndiscr, ptrfield, .. } => {
+        StructWrappedNullablePointer { nndiscr, ptrfield, .. } => {
             if is_null(const_struct_field(ccx, val, ptrfield)) {
                 /* subtraction as uint is ok because nndiscr is either 0 or 1 */
                 (1 - nndiscr) as Disr
@@ -932,11 +946,11 @@ pub fn const_get_field(ccx: &CrateContext, r: &Repr, val: ValueRef,
         CEnum(..) => ccx.sess().bug("element access in C-like enum const"),
         Univariant(..) => const_struct_field(ccx, val, ix),
         General(..) => const_struct_field(ccx, val, ix + 1),
-        NullablePointer { nonnull: ref st, .. } if st.fields.len() == 1 => {
+        RawNullablePointer { .. } => {
             assert_eq!(ix, 0);
             val
         }
-        NullablePointer{ .. } => const_struct_field(ccx, val, ix)
+        StructWrappedNullablePointer{ .. } => const_struct_field(ccx, val, ix)
     }
 }
 

src/librustc/middle/trans/debuginfo.rs

@@ -1657,7 +1657,10 @@ fn prepare_enum_metadata(cx: &CrateContext,
                 }),
             }
         }
-        adt::NullablePointer { nonnull: ref struct_def, nndiscr, .. } => {
+        adt::RawNullablePointer { nnty, .. } => {
+            FinalMetadata(type_metadata(cx, nnty, span))
+        }
+        adt::StructWrappedNullablePointer { nonnull: ref struct_def, nndiscr, .. } => {
             let (metadata_stub,
                  variant_llvm_type,
                  member_description_factory) =