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Add constants for trait object fields, and replace "magic numbers" in GEPi() calls with them #6172

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Add constants for trait object fields, and replace "magic numbers" in GEPi() calls with them #6172

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7 changes: 7 additions & 0 deletions src/librustc/back/abi.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -57,6 +57,13 @@ pub static n_tydesc_fields: uint = 8u;
pub static fn_field_code: uint = 0u;
pub static fn_field_box: uint = 1u;

// The three fields of a trait object/trait instance: vtable, box, and type
// description.
pub static trt_field_vtable: uint = 0u;
pub static trt_field_box: uint = 1u;
// This field is only present in unique trait objects, so it comes last.
pub static trt_field_tydesc: uint = 2u;

pub static vec_elt_fill: uint = 0u;

pub static vec_elt_alloc: uint = 1u;
Expand Down
12 changes: 6 additions & 6 deletions src/librustc/middle/trans/glue.rs
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Expand Up @@ -549,12 +549,12 @@ pub fn make_drop_glue(bcx: block, v0: ValueRef, t: ty::t) {
closure::make_closure_glue(bcx, v0, t, drop_ty)
}
ty::ty_trait(_, _, ty::BoxTraitStore, _) => {
let llbox = Load(bcx, GEPi(bcx, v0, [0u, 1u]));
let llbox = Load(bcx, GEPi(bcx, v0, [0u, abi::trt_field_box]));
decr_refcnt_maybe_free(bcx, llbox, ty::mk_opaque_box(ccx.tcx))
}
ty::ty_trait(_, _, ty::UniqTraitStore, _) => {
let lluniquevalue = GEPi(bcx, v0, [0, 1]);
let lltydesc = Load(bcx, GEPi(bcx, v0, [0, 2]));
let lluniquevalue = GEPi(bcx, v0, [0, abi::trt_field_box]);
let lltydesc = Load(bcx, GEPi(bcx, v0, [0, abi::trt_field_tydesc]));
call_tydesc_glue_full(bcx, lluniquevalue, lltydesc,
abi::tydesc_field_free_glue, None);
bcx
Expand Down Expand Up @@ -613,13 +613,13 @@ pub fn make_take_glue(bcx: block, v: ValueRef, t: ty::t) {
closure::make_closure_glue(bcx, v, t, take_ty)
}
ty::ty_trait(_, _, ty::BoxTraitStore, _) => {
let llbox = Load(bcx, GEPi(bcx, v, [0u, 1u]));
let llbox = Load(bcx, GEPi(bcx, v, [0u, abi::trt_field_box]));
incr_refcnt_of_boxed(bcx, llbox);
bcx
}
ty::ty_trait(_, _, ty::UniqTraitStore, _) => {
let llval = GEPi(bcx, v, [0, 1]);
let lltydesc = Load(bcx, GEPi(bcx, v, [0, 2]));
let llval = GEPi(bcx, v, [0, abi::trt_field_box]);
let lltydesc = Load(bcx, GEPi(bcx, v, [0, abi::trt_field_tydesc]));
call_tydesc_glue_full(bcx, llval, lltydesc,
abi::tydesc_field_take_glue, None);
bcx
Expand Down
26 changes: 15 additions & 11 deletions src/librustc/middle/trans/meth.rs
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Expand Up @@ -637,14 +637,15 @@ pub fn trans_trait_callee_from_llval(bcx: block,
val_str(bcx.ccx().tn, llpair));
let llvtable = Load(bcx,
PointerCast(bcx,
GEPi(bcx, llpair, [0u, 0u]),
GEPi(bcx, llpair,
[0u, abi::trt_field_vtable]),
T_ptr(T_ptr(T_vtable()))));

// Load the box from the @Trait pair and GEP over the box header if
// necessary:
let mut llself;
debug!("(translating trait callee) loading second index from pair");
let llbox = Load(bcx, GEPi(bcx, llpair, [0u, 1u]));
let llbox = Load(bcx, GEPi(bcx, llpair, [0u, abi::trt_field_box]));

// Munge `llself` appropriately for the type of `self` in the method.
let self_mode;
Expand Down Expand Up @@ -845,27 +846,30 @@ pub fn trans_trait_cast(bcx: block,

match store {
ty::RegionTraitStore(_) | ty::BoxTraitStore => {
let mut llboxdest = GEPi(bcx, lldest, [0u, 1u]);
// Just store the pointer into the pair.
let mut llboxdest = GEPi(bcx, lldest, [0u, abi::trt_field_box]);
// Just store the pointer into the pair. (Region/borrowed
// and boxed trait objects are represented as pairs, and
// have no type descriptor field.)
llboxdest = PointerCast(bcx,
llboxdest,
T_ptr(type_of(bcx.ccx(), v_ty)));
bcx = expr::trans_into(bcx, val, SaveIn(llboxdest));
}
ty::UniqTraitStore => {
// Translate the uniquely-owned value into the second element of
// the triple. (The first element is the vtable.)
let mut llvaldest = GEPi(bcx, lldest, [0, 1]);
// Translate the uniquely-owned value in the
// triple. (Unique trait objects are represented as
// triples.)
let mut llvaldest = GEPi(bcx, lldest, [0, abi::trt_field_box]);
llvaldest = PointerCast(bcx,
llvaldest,
T_ptr(type_of(bcx.ccx(), v_ty)));
bcx = expr::trans_into(bcx, val, SaveIn(llvaldest));

// Get the type descriptor of the wrapped value and store it into
// the third element of the triple as well.
// Get the type descriptor of the wrapped value and store
// it in the triple as well.
let tydesc = get_tydesc(bcx.ccx(), v_ty);
glue::lazily_emit_all_tydesc_glue(bcx.ccx(), tydesc);
let lltydescdest = GEPi(bcx, lldest, [0, 2]);
let lltydescdest = GEPi(bcx, lldest, [0, abi::trt_field_tydesc]);
Store(bcx, tydesc.tydesc, lltydescdest);
}
}
Expand All @@ -875,7 +879,7 @@ pub fn trans_trait_cast(bcx: block,
let orig = resolve_vtable_in_fn_ctxt(bcx.fcx, orig);
let vtable = get_vtable(bcx.ccx(), orig);
Store(bcx, vtable, PointerCast(bcx,
GEPi(bcx, lldest, [0u, 0u]),
GEPi(bcx, lldest, [0u, abi::trt_field_vtable]),
T_ptr(val_ty(vtable))));

bcx
Expand Down