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// Routines useful for garbage collection.
import lib::llvm::True;
import lib::llvm::llvm::ValueRef;
import middle::trans;
import middle::trans::{get_tydesc, tps_normal};
import middle::trans_common::*;
import middle::ty;
import option::none;
import str;
import lll = lib::llvm::llvm;
import bld = trans_build;
type ctxt = @{mutable next_tydesc_num: uint};
fn mk_ctxt() -> ctxt { ret @{mutable next_tydesc_num: 0u}; }
fn add_global(ccx: @crate_ctxt, llval: ValueRef, name: str) -> ValueRef {
let llglobal =
str::as_buf(name,
{|buf|
lll::LLVMAddGlobal(ccx.llmod, val_ty(llval), buf)
});
lll::LLVMSetInitializer(llglobal, llval);
lll::LLVMSetGlobalConstant(llglobal, True);
ret llglobal;
}
fn add_gc_root(cx: @block_ctxt, llval: ValueRef, ty: ty::t) -> @block_ctxt {
let bcx = cx;
let ccx = bcx_ccx(cx);
if !type_is_gc_relevant(bcx_tcx(cx), ty) ||
ty::type_has_dynamic_size(bcx_tcx(cx), ty) {
ret bcx;
}
let gc_cx = bcx_ccx(cx).gc_cx;
// FIXME (issue #839): For now, we are unconditionally zeroing out all
// GC-relevant types. Eventually we should use typestate for this.
bcx = trans::zero_alloca(bcx, llval, ty);
let ti = none;
let td_r = get_tydesc(bcx, ty, false, tps_normal, ti);
bcx = td_r.result.bcx;
let lltydesc = td_r.result.val;
let gcroot = bcx_ccx(bcx).intrinsics.get("llvm.gcroot");
let llvalptr = bld::PointerCast(bcx, llval, T_ptr(T_ptr(T_i8())));
alt td_r.kind {
tk_derived. {
// It's a derived type descriptor. First, spill it.
let lltydescptr = trans::alloca(bcx, val_ty(lltydesc));
let llderivedtydescs =
trans::llderivedtydescs_block_ctxt(bcx_fcx(bcx));
bld::Store(llderivedtydescs, lltydesc, lltydescptr);
let number = gc_cx.next_tydesc_num;
gc_cx.next_tydesc_num += 1u;
let lldestindex =
add_global(bcx_ccx(bcx), C_struct([C_int(ccx, 0),
C_uint(ccx, number)]),
"rust_gc_tydesc_dest_index");
let llsrcindex =
add_global(bcx_ccx(bcx), C_struct([C_int(ccx, 1),
C_uint(ccx, number)]),
"rust_gc_tydesc_src_index");
lldestindex = lll::LLVMConstPointerCast(lldestindex, T_ptr(T_i8()));
llsrcindex = lll::LLVMConstPointerCast(llsrcindex, T_ptr(T_i8()));
lltydescptr =
bld::PointerCast(llderivedtydescs, lltydescptr,
T_ptr(T_ptr(T_i8())));
bld::Call(llderivedtydescs, gcroot, [lltydescptr, lldestindex]);
bld::Call(bcx, gcroot, [llvalptr, llsrcindex]);
}
tk_param. {
bcx_tcx(cx).sess.bug("we should never be trying to root values " +
"of a type parameter");
}
tk_static. {
// Static type descriptor.
let llstaticgcmeta =
add_global(bcx_ccx(bcx), C_struct([C_int(ccx, 2), lltydesc]),
"rust_gc_tydesc_static_gc_meta");
let llstaticgcmetaptr =
lll::LLVMConstPointerCast(llstaticgcmeta, T_ptr(T_i8()));
bld::Call(bcx, gcroot, [llvalptr, llstaticgcmetaptr]);
}
}
ret bcx;
}
fn type_is_gc_relevant(cx: ty::ctxt, ty: ty::t) -> bool {
alt ty::struct(cx, ty) {
ty::ty_nil. | ty::ty_bot. | ty::ty_bool. | ty::ty_int(_) |
ty::ty_float(_) | ty::ty_uint(_) | ty::ty_str. |
ty::ty_type. | ty::ty_native(_) | ty::ty_ptr(_) | ty::ty_type. |
ty::ty_native(_) {
ret false;
}
ty::ty_rec(fields) {
for f in fields { if type_is_gc_relevant(cx, f.mt.ty) { ret true; } }
ret false;
}
ty::ty_tup(elts) {
for elt in elts { if type_is_gc_relevant(cx, elt) { ret true; } }
ret false;
}
ty::ty_tag(did, tps) {
let variants = ty::tag_variants(cx, did);
for variant in *variants {
for aty in variant.args {
let arg_ty = ty::substitute_type_params(cx, tps, aty);
if type_is_gc_relevant(cx, arg_ty) { ret true; }
}
}
ret false;
}
ty::ty_vec(tm) {
ret type_is_gc_relevant(cx, tm.ty);
}
ty::ty_constr(sub, _) { ret type_is_gc_relevant(cx, sub); }
ty::ty_box(_) | ty::ty_uniq(_) | ty::ty_fn(_, _, _, _, _) |
ty::ty_native_fn(_, _) | ty::ty_obj(_) | ty::ty_param(_, _) |
ty::ty_res(_, _, _) {
ret true;
}
ty::ty_var(_) {
fail "ty_var in type_is_gc_relevant";
}
}
}
|
