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Move trans_call to destination_passing style
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Issue #667

The retptr passed to a function will now often be the actual
destination of the returned value (as in `{field1: func1()}`).
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@marijnh
marijnh committed Oct 4, 2011
1 parent 53c9b9a commit 6e56ec0
Showing 1 changed file with 57 additions and 56 deletions.
113 changes: 57 additions & 56 deletions src/comp/middle/trans.rs
View file
Original file line number Diff line number Diff line change
Expand Up @@ -2470,7 +2470,7 @@ fn trans_binary(cx: @block_ctxt, op: ast::binop, a: @ast::expr, b: @ast::expr,
}
}

// FIXME remove once all uses have been converted to join_returns
// FIXME[DPS] remove once all uses have been converted to join_returns
fn join_branches(parent_cx: @block_ctxt, ins: [result]) -> @block_ctxt {
let out = new_sub_block_ctxt(parent_cx, "join");
let branched = false;
Expand Down Expand Up @@ -2952,8 +2952,7 @@ fn trans_for_each(cx: @block_ctxt, local: @ast::local, seq: @ast::expr,
ast::expr_call(f, args) {
let pair =
create_real_fn_pair(cx, iter_body_llty, lliterbody, llenv.ptr);
let r = trans_call(cx, f, some(pair), args, seq.id);
ret r.res.bcx;
ret trans_call(cx, f, some(pair), args, seq.id, ignore);
}
}
}
Expand Down Expand Up @@ -3300,6 +3299,7 @@ fn expr_is_lval(tcx: ty::ctxt, e: @ast::expr) -> bool {
// The additional bool returned indicates whether it's mem (that is
// represented as an alloca or heap, hence needs a 'load' to be used as an
// immediate).
// FIXME[DPS] only allow this to be called on actual lvals
fn trans_lval(cx: @block_ctxt, e: @ast::expr) -> lval_result {
alt e.node {
ast::expr_path(p) {
Expand Down Expand Up @@ -3340,10 +3340,17 @@ fn trans_lval(cx: @block_ctxt, e: @ast::expr) -> lval_result {
ret lval_mem(sub.bcx, val);
}
ast::expr_call(f, args) {
let {res: {bcx, val}, by_ref} =
trans_call(cx, f, none, args, e.id);
if by_ref { ret lval_mem(bcx, val); }
else { ret lval_val(bcx, val); }
// A by-ref returning function
if expr_is_lval(bcx_tcx(cx), e) {
let cell = empty_dest_cell();
let bcx = trans_call(cx, f, none, args, e.id, by_ref(cell));
ret lval_mem(bcx, *cell);
} else { // By-value return
let {bcx, val} = dps_to_result(cx, {|bcx, dest|
trans_call(bcx, f, none, args, e.id, dest) },
ty::expr_ty(bcx_tcx(cx), e));
ret lval_val(bcx, val);
}
}
_ {
let res = trans_expr(cx, e);
Expand Down Expand Up @@ -3797,7 +3804,8 @@ fn trans_arg_expr(cx: @block_ctxt, arg: ty::arg, lldestty0: TypeRef,
// - trans_args
fn trans_args(cx: @block_ctxt, outer_cx: @block_ctxt, llenv: ValueRef,
gen: option::t<generic_info>,
lliterbody: option::t<ValueRef>, es: [@ast::expr], fn_ty: ty::t)
lliterbody: option::t<ValueRef>, es: [@ast::expr], fn_ty: ty::t,
dest: dest)
-> {bcx: @block_ctxt,
outer_cx: @block_ctxt,
args: [ValueRef],
Expand All @@ -3813,9 +3821,9 @@ fn trans_args(cx: @block_ctxt, outer_cx: @block_ctxt, llenv: ValueRef,

let ccx = bcx_ccx(cx);
let tcx = ccx.tcx;
let bcx: @block_ctxt = cx;
let bcx = cx;
let ret_style = ty::ty_fn_ret_style(tcx, fn_ty);
let by_ref = ast_util::ret_by_ref(ret_style);
let ret_ref = ast_util::ret_by_ref(ret_style);

let retty = ty::ty_fn_ret(tcx, fn_ty), full_retty = retty;
alt gen {
Expand All @@ -3828,13 +3836,21 @@ fn trans_args(cx: @block_ctxt, outer_cx: @block_ctxt, llenv: ValueRef,
_ { }
}
// Arg 0: Output pointer.
let llretslot_res = if ty::type_is_nil(tcx, retty) {
rslt(cx, llvm::LLVMGetUndef(T_ptr(T_nil())))
} else if by_ref {
rslt(cx, alloca(cx, T_ptr(type_of_or_i8(bcx, full_retty))))
} else { alloc_ty(bcx, full_retty) };
bcx = llretslot_res.bcx;
let llretslot = llretslot_res.val;
let llretty = type_of_or_i8(bcx, full_retty);
let dest_ref = false;
let llretslot = alt dest {
ignore. {
if ty::type_is_nil(tcx, full_retty) || !option::is_none(lliterbody) {
llvm::LLVMGetUndef(T_ptr(llretty))
} else { alloca(cx, llretty) }
}
save_in(dst) { dst }
overwrite(_, _) | by_val(_) { alloca(cx, llretty) }
by_ref(_) { dest_ref = true; alloca(cx, T_ptr(llretty)) }
};
// FIXME[DSP] does this always hold?
assert dest_ref == ret_ref;

if ty::type_contains_params(tcx, retty) {
// It's possible that the callee has some generic-ness somewhere in
// its return value -- say a method signature within an obj or a fn
Expand All @@ -3843,7 +3859,7 @@ fn trans_args(cx: @block_ctxt, outer_cx: @block_ctxt, llenv: ValueRef,
// view, for the sake of making a type-compatible call.
check non_ty_var(ccx, retty);
let llretty = T_ptr(type_of_inner(ccx, bcx.sp, retty));
if by_ref { llretty = T_ptr(llretty); }
if ret_ref { llretty = T_ptr(llretty); }
llargs += [PointerCast(cx, llretslot, llretty)];
} else { llargs += [llretslot]; }

Expand Down Expand Up @@ -3899,18 +3915,17 @@ fn trans_args(cx: @block_ctxt, outer_cx: @block_ctxt, llenv: ValueRef,

fn trans_call(in_cx: @block_ctxt, f: @ast::expr,
lliterbody: option::t<ValueRef>, args: [@ast::expr],
id: ast::node_id) -> {res: result, by_ref: bool} {
id: ast::node_id, dest: dest) -> @block_ctxt {
// NB: 'f' isn't necessarily a function; it might be an entire self-call
// expression because of the hack that allows us to process self-calls
// with trans_call.
let tcx = bcx_tcx(in_cx);
let fn_expr_ty = ty::expr_ty(tcx, f);

if check type_is_native_fn_on_c_stack(tcx, fn_expr_ty) {
ret trans_c_stack_native_call(in_cx, f, args);
ret trans_c_stack_native_call(in_cx, f, args, dest);
}

let by_ref = ast_util::ret_by_ref(ty::ty_fn_ret_style(tcx, fn_expr_ty));
let cx = new_scope_block_ctxt(in_cx, "call");
let f_res = trans_callee(cx, f);
let bcx = f_res.bcx;
Expand All @@ -3936,65 +3951,49 @@ fn trans_call(in_cx: @block_ctxt, f: @ast::expr,
let ret_ty = ty::node_id_to_type(tcx, id);
let args_res =
trans_args(bcx, in_cx, llenv, f_res.generic, lliterbody, args,
fn_expr_ty);
fn_expr_ty, dest);
Br(args_res.outer_cx, cx.llbb);
bcx = args_res.bcx;
let llargs = args_res.args;
let llretslot = args_res.retslot;

/*
log_err "calling: " + val_str(bcx_ccx(cx).tn, faddr);
for arg: ValueRef in llargs {
log_err "arg: " + val_str(bcx_ccx(cx).tn, arg);
}
*/

/* If the block is terminated,
then one or more of the args has
type _|_. Since that means it diverges, the code
for the call itself is unreachable. */
let retval = C_nil();
bcx = invoke_full(bcx, faddr, llargs, args_res.to_zero,
args_res.to_revoke);
alt lliterbody {
none. {
if !ty::type_is_nil(tcx, ret_ty) {
if by_ref {
retval = Load(bcx, llretslot);
} else {
retval = load_if_immediate(bcx, llretslot, ret_ty);
// Retval doesn't correspond to anything really tangible
// in the frame, but it's a ref all the same, so we put a
// note here to drop it when we're done in this scope.
add_clean_temp(in_cx, retval, ret_ty);
}
alt dest {
ignore. {
if llvm::LLVMIsUndef(llretslot) != lib::llvm::True {
bcx = drop_ty(bcx, llretslot, ret_ty);
}
}
some(_) {
// If there was an lliterbody, it means we were calling an
// iter, and we are *not* the party using its 'output' value,
// we should ignore llretslot.
save_in(_) { } // Already saved by callee
overwrite(a, t) {
bcx = drop_ty(bcx, a, t);
bcx = memmove_ty(bcx, a, llretslot, ret_ty);
}
by_ref(cell) | by_val(cell) {
*cell = Load(bcx, llretslot);
}
}
// Forget about anything we moved out.
bcx = zero_and_revoke(bcx, args_res.to_zero, args_res.to_revoke);

if !by_ref { bcx = trans_block_cleanups(bcx, cx); }
bcx = trans_block_cleanups(bcx, cx);
let next_cx = new_sub_block_ctxt(in_cx, "next");
if bcx.unreachable || ty::type_is_bot(tcx, ret_ty) {
Unreachable(next_cx);
}
Br(bcx, next_cx.llbb);
bcx = next_cx;
ret {res: rslt(bcx, retval), by_ref: by_ref};
ret next_cx;
}

// Translates a native call on the C stack. Calls into the runtime to perform
// the stack switching operation.
fn trans_c_stack_native_call(bcx: @block_ctxt, f: @ast::expr,
args: [@ast::expr])
-> {res: result, by_ref: bool} {
args: [@ast::expr], dest: dest) -> @block_ctxt {
let ccx = bcx_ccx(bcx);
let f_res = trans_callee(bcx, f);
let llfn = f_res.val; bcx = f_res.bcx;
Expand Down Expand Up @@ -4047,8 +4046,7 @@ fn trans_c_stack_native_call(bcx: @block_ctxt, f: @ast::expr,

// Forget about anything we moved out.
bcx = zero_and_revoke(bcx, to_zero, to_revoke);

ret {res: rslt(bcx, llretval), by_ref: false};
ret store_in_dest(bcx, llretval, dest);
}

fn zero_and_revoke(bcx: @block_ctxt,
Expand Down Expand Up @@ -4345,8 +4343,11 @@ fn trans_expr_dps(bcx: @block_ctxt, e: @ast::expr, dest: dest)
ast::expr_anon_obj(anon_obj) {
ret trans_anon_obj(bcx, e.span, anon_obj, e.id, dest);
}
// FIXME[DPS] untangle non-lval calls and fields from trans_lval
ast::expr_call(_, _) | ast::expr_field(_, _) {
ast::expr_call(f, args) {
ret trans_call(bcx, f, none, args, e.id, dest);
}
// FIXME[DPS] untangle non-lval fields from trans_lval
ast::expr_field(_, _) {
ret lval_to_dps(bcx, e, dest);
}

Expand Down

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