rustc: Unify fat pointer ABI constants.

This merges the `trt_field_*`, `fn_field_*` and `slice_elt_*` constants
into two `FAT_PTR_*` constants. This resolves the first part of #18590.

11 files changed, 50 insertions, 53 deletions

diff --git a/src/librustc_back/abi.rs b/src/librustc_back/abi.rs
index 335317be4b4..f89d5d826f5 100644
--- a/src/librustc_back/abi.rs
+++ b/src/librustc_back/abi.rs
@@ -14,17 +14,14 @@ pub const box_field_refcnt: uint = 0u;
 pub const box_field_drop_glue: uint = 1u;
 pub const box_field_body: uint = 4u;
 
-// FIXME(18590) although we have three different layouts here, the compiler relies on
-// them being the same. We should replace them with one set of constants.
+/// The first half of a fat pointer.
+/// - For a closure, this is the code address.
+/// - For an object or trait instance, this is the address of the box.
+/// - For a slice, this is the base address.
+pub const FAT_PTR_ADDR: uint = 0;
 
-// The two halves of a closure: code and environment.
-pub const fn_field_code: uint = 0u;
-pub const fn_field_box: uint = 1u;
-
-// The two fields of a trait object/trait instance: vtable and box.
-// The vtable contains the type descriptor as first element.
-pub const trt_field_box: uint = 0u;
-pub const trt_field_vtable: uint = 1u;
-
-pub const slice_elt_base: uint = 0u;
-pub const slice_elt_len: uint = 1u;
+/// The second half of a fat pointer.
+/// - For a closure, this is the address of the environment.
+/// - For an object or trait instance, this is the address of the vtable.
+/// - For a slice, this is the length.
+pub const FAT_PTR_EXTRA: uint = 1u;
diff --git a/src/librustc_trans/trans/_match.rs b/src/librustc_trans/trans/_match.rs
index de406cff6e7..d23e53d2e69 100644
--- a/src/librustc_trans/trans/_match.rs
+++ b/src/librustc_trans/trans/_match.rs
@@ -649,8 +649,8 @@ fn bind_subslice_pat(bcx: Block,
                                 ty::mt {ty: vt.unit_ty, mutbl: ast::MutImmutable});
     let scratch = rvalue_scratch_datum(bcx, slice_ty, "");
     Store(bcx, slice_begin,
-          GEPi(bcx, scratch.val, &[0u, abi::slice_elt_base]));
-    Store(bcx, slice_len, GEPi(bcx, scratch.val, &[0u, abi::slice_elt_len]));
+          GEPi(bcx, scratch.val, &[0u, abi::FAT_PTR_ADDR]));
+    Store(bcx, slice_len, GEPi(bcx, scratch.val, &[0u, abi::FAT_PTR_EXTRA]));
     scratch.val
 }
 
diff --git a/src/librustc_trans/trans/adt.rs b/src/librustc_trans/trans/adt.rs
index 2e184a5d74b..e7d1b9726a1 100644
--- a/src/librustc_trans/trans/adt.rs
+++ b/src/librustc_trans/trans/adt.rs
@@ -52,7 +52,7 @@ use std::num::Int;
 use std::rc::Rc;
 
 use llvm::{ValueRef, True, IntEQ, IntNE};
-use back::abi::slice_elt_base;
+use back::abi;
 use middle::subst;
 use middle::subst::Subst;
 use trans::_match;
@@ -684,7 +684,7 @@ fn struct_wrapped_nullable_bitdiscr(bcx: Block, nndiscr: Disr, ptrfield: Pointer
                                     scrutinee: ValueRef) -> ValueRef {
     let llptrptr = match ptrfield {
         ThinPointer(field) => GEPi(bcx, scrutinee, &[0, field]),
-        FatPointer(field) => GEPi(bcx, scrutinee, &[0, field, slice_elt_base])
+        FatPointer(field) => GEPi(bcx, scrutinee, &[0, field, abi::FAT_PTR_ADDR])
     };
     let llptr = Load(bcx, llptrptr);
     let cmp = if nndiscr == 0 { IntEQ } else { IntNE };
@@ -782,7 +782,7 @@ pub fn trans_set_discr<'blk, 'tcx>(bcx: Block<'blk, 'tcx>, r: &Repr<'tcx>,
                         (GEPi(bcx, val, &[0, field]),
                          type_of::type_of(bcx.ccx(), nonnull.fields[field])),
                     FatPointer(field) => {
-                        let v = GEPi(bcx, val, &[0, field, slice_elt_base]);
+                        let v = GEPi(bcx, val, &[0, field, abi::FAT_PTR_ADDR]);
                         (v, val_ty(v).element_type())
                     }
                 };
@@ -1118,7 +1118,7 @@ pub fn const_get_discrim(ccx: &CrateContext, r: &Repr, val: ValueRef)
         StructWrappedNullablePointer { nndiscr, ptrfield, .. } => {
             let (idx, sub_idx) = match ptrfield {
                 ThinPointer(field) => (field, None),
-                FatPointer(field) => (field, Some(slice_elt_base))
+                FatPointer(field) => (field, Some(abi::FAT_PTR_ADDR))
             };
             if is_null(const_struct_field(ccx, val, idx, sub_idx)) {
                 /* subtraction as uint is ok because nndiscr is either 0 or 1 */
diff --git a/src/librustc_trans/trans/base.rs b/src/librustc_trans/trans/base.rs
index c30ad781cc9..a6f35c29662 100644
--- a/src/librustc_trans/trans/base.rs
+++ b/src/librustc_trans/trans/base.rs
@@ -705,8 +705,8 @@ pub fn iter_structural_ty<'a, 'blk, 'tcx>(cx: Block<'blk, 'tcx>,
     let (data_ptr, info) = if ty::type_is_sized(cx.tcx(), t) {
         (av, None)
     } else {
-        let data = GEPi(cx, av, &[0, abi::slice_elt_base]);
-        let info = GEPi(cx, av, &[0, abi::slice_elt_len]);
+        let data = GEPi(cx, av, &[0, abi::FAT_PTR_ADDR]);
+        let info = GEPi(cx, av, &[0, abi::FAT_PTR_EXTRA]);
         (Load(cx, data), Some(Load(cx, info)))
     };
 
@@ -724,8 +724,8 @@ pub fn iter_structural_ty<'a, 'blk, 'tcx>(cx: Block<'blk, 'tcx>,
                   } else {
                       let boxed_ty = ty::mk_open(cx.tcx(), field_ty);
                       let scratch = datum::rvalue_scratch_datum(cx, boxed_ty, "__fat_ptr_iter");
-                      Store(cx, llfld_a, GEPi(cx, scratch.val, &[0, abi::slice_elt_base]));
-                      Store(cx, info.unwrap(), GEPi(cx, scratch.val, &[0, abi::slice_elt_len]));
+                      Store(cx, llfld_a, GEPi(cx, scratch.val, &[0, abi::FAT_PTR_ADDR]));
+                      Store(cx, info.unwrap(), GEPi(cx, scratch.val, &[0, abi::FAT_PTR_EXTRA]));
                       scratch.val
                   };
                   cx = f(cx, val, field_ty);
diff --git a/src/librustc_trans/trans/callee.rs b/src/librustc_trans/trans/callee.rs
index bf7adbbecef..6d0f5980442 100644
--- a/src/librustc_trans/trans/callee.rs
+++ b/src/librustc_trans/trans/callee.rs
@@ -724,9 +724,9 @@ pub fn trans_call_inner<'a, 'blk, 'tcx>(bcx: Block<'blk, 'tcx>,
             // Closures are represented as (llfn, llclosure) pair:
             // load the requisite values out.
             let pair = d.to_llref();
-            let llfn = GEPi(bcx, pair, &[0u, abi::fn_field_code]);
+            let llfn = GEPi(bcx, pair, &[0u, abi::FAT_PTR_ADDR]);
             let llfn = Load(bcx, llfn);
-            let llenv = GEPi(bcx, pair, &[0u, abi::fn_field_box]);
+            let llenv = GEPi(bcx, pair, &[0u, abi::FAT_PTR_EXTRA]);
             let llenv = Load(bcx, llenv);
             (llfn, Some(llenv), None)
         }
diff --git a/src/librustc_trans/trans/closure.rs b/src/librustc_trans/trans/closure.rs
index d4c93be7eaf..c0c46ed57cc 100644
--- a/src/librustc_trans/trans/closure.rs
+++ b/src/librustc_trans/trans/closure.rs
@@ -339,9 +339,9 @@ fn load_unboxed_closure_environment<'blk, 'tcx>(
 }
 
 fn fill_fn_pair(bcx: Block, pair: ValueRef, llfn: ValueRef, llenvptr: ValueRef) {
-    Store(bcx, llfn, GEPi(bcx, pair, &[0u, abi::fn_field_code]));
+    Store(bcx, llfn, GEPi(bcx, pair, &[0u, abi::FAT_PTR_ADDR]));
     let llenvptr = PointerCast(bcx, llenvptr, Type::i8p(bcx.ccx()));
-    Store(bcx, llenvptr, GEPi(bcx, pair, &[0u, abi::fn_field_box]));
+    Store(bcx, llenvptr, GEPi(bcx, pair, &[0u, abi::FAT_PTR_EXTRA]));
 }
 
 #[deriving(PartialEq)]
diff --git a/src/librustc_trans/trans/consts.rs b/src/librustc_trans/trans/consts.rs
index 4213e941727..c119cf16328 100644
--- a/src/librustc_trans/trans/consts.rs
+++ b/src/librustc_trans/trans/consts.rs
@@ -264,8 +264,8 @@ pub fn const_expr<'a, 'tcx>(cx: &CrateContext<'a, 'tcx>, e: &ast::Expr)
                                         ty::ty_vec(unit_ty, Some(len)) => {
                                             let llunitty = type_of::type_of(cx, unit_ty);
                                             let llptr = const_ptrcast(cx, llconst, llunitty);
-                                            assert_eq!(abi::slice_elt_base, 0);
-                                            assert_eq!(abi::slice_elt_len, 1);
+                                            assert_eq!(abi::FAT_PTR_ADDR, 0);
+                                            assert_eq!(abi::FAT_PTR_EXTRA, 1);
                                             llconst = C_struct(cx, &[
                                                 llptr,
                                                 C_uint(cx, len)
diff --git a/src/librustc_trans/trans/expr.rs b/src/librustc_trans/trans/expr.rs
index 670e893cc0e..b4751578dd1 100644
--- a/src/librustc_trans/trans/expr.rs
+++ b/src/librustc_trans/trans/expr.rs
@@ -171,11 +171,11 @@ pub fn trans<'blk, 'tcx>(bcx: Block<'blk, 'tcx>,
 }
 
 pub fn get_len(bcx: Block, fat_ptr: ValueRef) -> ValueRef {
-    GEPi(bcx, fat_ptr, &[0u, abi::slice_elt_len])
+    GEPi(bcx, fat_ptr, &[0u, abi::FAT_PTR_EXTRA])
 }
 
 pub fn get_dataptr(bcx: Block, fat_ptr: ValueRef) -> ValueRef {
-    GEPi(bcx, fat_ptr, &[0u, abi::slice_elt_base])
+    GEPi(bcx, fat_ptr, &[0u, abi::FAT_PTR_ADDR])
 }
 
 fn apply_adjustments<'blk, 'tcx>(bcx: Block<'blk, 'tcx>,
diff --git a/src/librustc_trans/trans/glue.rs b/src/librustc_trans/trans/glue.rs
index 67b3310dbdf..f4799d7536d 100644
--- a/src/librustc_trans/trans/glue.rs
+++ b/src/librustc_trans/trans/glue.rs
@@ -196,7 +196,7 @@ fn trans_struct_drop_flag<'blk, 'tcx>(mut bcx: Block<'blk, 'tcx>,
     let struct_data = if ty::type_is_sized(bcx.tcx(), t) {
         v0
     } else {
-        let llval = GEPi(bcx, v0, &[0, abi::slice_elt_base]);
+        let llval = GEPi(bcx, v0, &[0, abi::FAT_PTR_ADDR]);
         Load(bcx, llval)
     };
     let drop_flag = unpack_datum!(bcx, adt::trans_drop_flag_ptr(bcx, &*repr, struct_data));
@@ -237,8 +237,8 @@ fn trans_struct_drop<'blk, 'tcx>(bcx: Block<'blk, 'tcx>,
     let (struct_data, info) = if ty::type_is_sized(bcx.tcx(), t) {
         (v0, None)
     } else {
-        let data = GEPi(bcx, v0, &[0, abi::slice_elt_base]);
-        let info = GEPi(bcx, v0, &[0, abi::slice_elt_len]);
+        let data = GEPi(bcx, v0, &[0, abi::FAT_PTR_ADDR]);
+        let info = GEPi(bcx, v0, &[0, abi::FAT_PTR_EXTRA]);
         (Load(bcx, data), Some(Load(bcx, info)))
     };
 
@@ -255,14 +255,14 @@ fn trans_struct_drop<'blk, 'tcx>(bcx: Block<'blk, 'tcx>,
             // The dtor expects a fat pointer, so make one, even if we have to fake it.
             let boxed_ty = ty::mk_open(bcx.tcx(), t);
             let scratch = datum::rvalue_scratch_datum(bcx, boxed_ty, "__fat_ptr_drop_self");
-            Store(bcx, value, GEPi(bcx, scratch.val, &[0, abi::slice_elt_base]));
+            Store(bcx, value, GEPi(bcx, scratch.val, &[0, abi::FAT_PTR_ADDR]));
             Store(bcx,
                   // If we just had a thin pointer, make a fat pointer by sticking
                   // null where we put the unsizing info. This works because t
                   // is a sized type, so we will only unpack the fat pointer, never
                   // use the fake info.
                   info.unwrap_or(C_null(Type::i8p(bcx.ccx()))),
-                  GEPi(bcx, scratch.val, &[0, abi::slice_elt_len]));
+                  GEPi(bcx, scratch.val, &[0, abi::FAT_PTR_EXTRA]));
             PointerCast(variant_cx, scratch.val, params[0])
         } else {
             PointerCast(variant_cx, value, params[0])
@@ -280,8 +280,8 @@ fn trans_struct_drop<'blk, 'tcx>(bcx: Block<'blk, 'tcx>,
             } else {
                 let boxed_ty = ty::mk_open(bcx.tcx(), *ty);
                 let scratch = datum::rvalue_scratch_datum(bcx, boxed_ty, "__fat_ptr_drop_field");
-                Store(bcx, llfld_a, GEPi(bcx, scratch.val, &[0, abi::slice_elt_base]));
-                Store(bcx, info.unwrap(), GEPi(bcx, scratch.val, &[0, abi::slice_elt_len]));
+                Store(bcx, llfld_a, GEPi(bcx, scratch.val, &[0, abi::FAT_PTR_ADDR]));
+                Store(bcx, info.unwrap(), GEPi(bcx, scratch.val, &[0, abi::FAT_PTR_EXTRA]));
                 scratch.val
             };
             variant_cx.fcx.schedule_drop_mem(cleanup::CustomScope(field_scope),
@@ -369,11 +369,11 @@ fn make_drop_glue<'blk, 'tcx>(bcx: Block<'blk, 'tcx>, v0: ValueRef, t: Ty<'tcx>)
                     tvec::make_drop_glue_unboxed(bcx, v0, unit_ty, true)
                 }
                 ty::ty_trait(..) => {
-                    let lluniquevalue = GEPi(bcx, v0, &[0, abi::trt_field_box]);
+                    let lluniquevalue = GEPi(bcx, v0, &[0, abi::FAT_PTR_ADDR]);
                     // Only drop the value when it is non-null
                     let concrete_ptr = Load(bcx, lluniquevalue);
                     with_cond(bcx, IsNotNull(bcx, concrete_ptr), |bcx| {
-                        let dtor_ptr = Load(bcx, GEPi(bcx, v0, &[0, abi::trt_field_vtable]));
+                        let dtor_ptr = Load(bcx, GEPi(bcx, v0, &[0, abi::FAT_PTR_EXTRA]));
                         let dtor = Load(bcx, dtor_ptr);
                         Call(bcx,
                              dtor,
@@ -383,12 +383,12 @@ fn make_drop_glue<'blk, 'tcx>(bcx: Block<'blk, 'tcx>, v0: ValueRef, t: Ty<'tcx>)
                     })
                 }
                 ty::ty_struct(..) if !ty::type_is_sized(bcx.tcx(), content_ty) => {
-                    let llval = GEPi(bcx, v0, &[0, abi::slice_elt_base]);
+                    let llval = GEPi(bcx, v0, &[0, abi::FAT_PTR_ADDR]);
                     let llbox = Load(bcx, llval);
                     let not_null = IsNotNull(bcx, llbox);
                     with_cond(bcx, not_null, |bcx| {
                         let bcx = drop_ty(bcx, v0, content_ty, None);
-                        let info = GEPi(bcx, v0, &[0, abi::slice_elt_len]);
+                        let info = GEPi(bcx, v0, &[0, abi::FAT_PTR_EXTRA]);
                         let info = Load(bcx, info);
                         let (llsize, llalign) = size_and_align_of_dst(bcx, content_ty, info);
                         trans_exchange_free_dyn(bcx, llbox, llsize, llalign)
@@ -440,7 +440,7 @@ fn make_drop_glue<'blk, 'tcx>(bcx: Block<'blk, 'tcx>, v0: ValueRef, t: Ty<'tcx>)
                                                          t,
                                                          |bb, vv, tt| drop_ty(bb, vv, tt, None)),
         ty::ty_closure(ref f) if f.store == ty::UniqTraitStore => {
-            let box_cell_v = GEPi(bcx, v0, &[0u, abi::fn_field_box]);
+            let box_cell_v = GEPi(bcx, v0, &[0u, abi::FAT_PTR_EXTRA]);
             let env = Load(bcx, box_cell_v);
             let env_ptr_ty = Type::at_box(bcx.ccx(), Type::i8(bcx.ccx())).ptr_to();
             let env = PointerCast(bcx, env, env_ptr_ty);
@@ -456,8 +456,8 @@ fn make_drop_glue<'blk, 'tcx>(bcx: Block<'blk, 'tcx>, v0: ValueRef, t: Ty<'tcx>)
             // above), because this happens for a trait field in an unsized
             // struct. If anything is null, it is the whole struct and we won't
             // get here.
-            let lluniquevalue = GEPi(bcx, v0, &[0, abi::trt_field_box]);
-            let dtor_ptr = Load(bcx, GEPi(bcx, v0, &[0, abi::trt_field_vtable]));
+            let lluniquevalue = GEPi(bcx, v0, &[0, abi::FAT_PTR_ADDR]);
+            let dtor_ptr = Load(bcx, GEPi(bcx, v0, &[0, abi::FAT_PTR_EXTRA]));
             let dtor = Load(bcx, dtor_ptr);
             Call(bcx,
                  dtor,
diff --git a/src/librustc_trans/trans/meth.rs b/src/librustc_trans/trans/meth.rs
index 0311d37c3de..0ff7f3ee71c 100644
--- a/src/librustc_trans/trans/meth.rs
+++ b/src/librustc_trans/trans/meth.rs
@@ -481,7 +481,7 @@ pub fn trans_trait_callee_from_llval<'blk, 'tcx>(bcx: Block<'blk, 'tcx>,
 
     // Load the data pointer from the object.
     debug!("(translating trait callee) loading second index from pair");
-    let llboxptr = GEPi(bcx, llpair, &[0u, abi::trt_field_box]);
+    let llboxptr = GEPi(bcx, llpair, &[0u, abi::FAT_PTR_ADDR]);
     let llbox = Load(bcx, llboxptr);
     let llself = PointerCast(bcx, llbox, Type::i8p(ccx));
 
@@ -503,7 +503,7 @@ pub fn trans_trait_callee_from_llval<'blk, 'tcx>(bcx: Block<'blk, 'tcx>,
     let llvtable = Load(bcx,
                         PointerCast(bcx,
                                     GEPi(bcx, llpair,
-                                         &[0u, abi::trt_field_vtable]),
+                                         &[0u, abi::FAT_PTR_EXTRA]),
                                     Type::vtable(ccx).ptr_to().ptr_to()));
     let mptr = Load(bcx, GEPi(bcx, llvtable, &[0u, n_method + VTABLE_OFFSET]));
     let mptr = PointerCast(bcx, mptr, llcallee_ty.ptr_to());
@@ -761,13 +761,13 @@ pub fn trans_trait_cast<'blk, 'tcx>(bcx: Block<'blk, 'tcx>,
     let llbox_ty = type_of(bcx.ccx(), datum_ty);
 
     // Store the pointer into the first half of pair.
-    let llboxdest = GEPi(bcx, lldest, &[0u, abi::trt_field_box]);
+    let llboxdest = GEPi(bcx, lldest, &[0u, abi::FAT_PTR_ADDR]);
     let llboxdest = PointerCast(bcx, llboxdest, llbox_ty.ptr_to());
     bcx = datum.store_to(bcx, llboxdest);
 
     // Store the vtable into the second half of pair.
     let vtable = get_vtable(bcx, datum_ty, trait_ref);
-    let llvtabledest = GEPi(bcx, lldest, &[0u, abi::trt_field_vtable]);
+    let llvtabledest = GEPi(bcx, lldest, &[0u, abi::FAT_PTR_EXTRA]);
     let llvtabledest = PointerCast(bcx, llvtabledest, val_ty(vtable).ptr_to());
     Store(bcx, vtable, llvtabledest);
 
diff --git a/src/librustc_trans/trans/tvec.rs b/src/librustc_trans/trans/tvec.rs
index 359f74bdbf1..8e986defb6a 100644
--- a/src/librustc_trans/trans/tvec.rs
+++ b/src/librustc_trans/trans/tvec.rs
@@ -231,8 +231,8 @@ pub fn trans_lit_str<'blk, 'tcx>(bcx: Block<'blk, 'tcx>,
                 let llbytes = C_uint(bcx.ccx(), bytes);
                 let llcstr = C_cstr(bcx.ccx(), str_lit, false);
                 let llcstr = llvm::LLVMConstPointerCast(llcstr, Type::i8p(bcx.ccx()).to_ref());
-                Store(bcx, llcstr, GEPi(bcx, lldest, &[0u, abi::slice_elt_base]));
-                Store(bcx, llbytes, GEPi(bcx, lldest, &[0u, abi::slice_elt_len]));
+                Store(bcx, llcstr, GEPi(bcx, lldest, &[0u, abi::FAT_PTR_ADDR]));
+                Store(bcx, llbytes, GEPi(bcx, lldest, &[0u, abi::FAT_PTR_EXTRA]));
                 bcx
             }
         }
@@ -401,8 +401,8 @@ pub fn get_fixed_base_and_len(bcx: Block,
 fn get_slice_base_and_len(bcx: Block,
                           llval: ValueRef)
                           -> (ValueRef, ValueRef) {
-    let base = Load(bcx, GEPi(bcx, llval, &[0u, abi::slice_elt_base]));
-    let len = Load(bcx, GEPi(bcx, llval, &[0u, abi::slice_elt_len]));
+    let base = Load(bcx, GEPi(bcx, llval, &[0u, abi::FAT_PTR_ADDR]));
+    let len = Load(bcx, GEPi(bcx, llval, &[0u, abi::FAT_PTR_EXTRA]));
     (base, len)
 }