Tamar Christina <tamar.christ...@arm.com> writes:
>> -----Original Message-----
>> From: Richard Sandiford <richard.sandif...@arm.com>
>> Sent: Monday, June 13, 2022 9:41 AM
>> To: Tamar Christina <tamar.christ...@arm.com>
>> Cc: gcc-patches@gcc.gnu.org; nd <n...@arm.com>; rguent...@suse.de
>> Subject: Re: [PATCH]middle-end Use subregs to expand COMPLEX_EXPR to
>> set the lowpart.
>>
>> Tamar Christina <tamar.christ...@arm.com> writes:
>> > Hi All,
>> >
>> > When lowering COMPLEX_EXPR we currently emit two VEC_EXTRACTs.
>> One
>> > for the lowpart and one for the highpart.
>> >
>> > The problem with this is that in RTL the lvalue of the RTX is the only
>> > thing tying the two instructions together.
>> >
>> > This means that e.g. combine is unable to try to combine the two
>> > instructions for setting the lowpart and highpart.
>> >
>> > For ISAs that have bit extract instructions we can eliminate one of
>> > the extracts if, and only if we're setting the entire complex number.
>> >
>> > This change changes the expand code when we're setting the entire
>> > complex number to generate a subreg for the lowpart instead of a
>> vec_extract.
>> >
>> > This allows us to optimize sequences such as:
>> >
>> > _Complex int f(int a, int b) {
>> > _Complex int t = a + b * 1i;
>> > return t;
>> > }
>> >
>> > from:
>> >
>> > f:
>> > bfi x2, x0, 0, 32
>> > bfi x2, x1, 32, 32
>> > mov x0, x2
>> > ret
>> >
>> > into:
>> >
>> > f:
>> > bfi x0, x1, 32, 32
>> > ret
>> >
>> > I have also confirmed the codegen for x86_64 did not change.
>> >
>> > Bootstrapped Regtested on aarch64-none-linux-gnu, x86_64-pc-linux-gnu
>> > and no issues.
>> >
>> > Ok for master?
>>
>> I'm not sure this is endian-safe. For big-endian it's the imaginary part
>> that can
>> be written as a subreg. The real part might be the high part of a register.
>>
>> Maybe a more general way to handle this would be to add (yet another)
>> parameter to store_bit_field that indicates that the current value of the
>> structure is undefined. That would also be useful in at least one other
>> caller
>> (from calls.cc). write_complex_part could then have a similar parameter,
>> true for the first write and false for the second.
>
> Ohayou-gozaimasu!
>
> I've rewritten it using the approach you requested. I attempted to set the
> flag
> In the correct places as well.
Thanks, looks good. But rather than treat this as a new case, I think
we can instead generalise this store_bit_field_1 code:
else if (constant_multiple_p (bitnum, regsize * BITS_PER_UNIT, ®num)
&& multiple_p (bitsize, regsize * BITS_PER_UNIT)
&& known_ge (GET_MODE_BITSIZE (GET_MODE (op0)), bitsize))
{
sub = simplify_gen_subreg (fieldmode, op0, GET_MODE (op0),
regnum * regsize);
if (sub)
{
if (reverse)
value = flip_storage_order (fieldmode, value);
emit_move_insn (sub, value);
return true;
}
}
so that the multiple_p test is skipped if the structure is undefined.
Richard
> Bootstrapped Regtested on aarch64-none-linux-gnu, x86_64-pc-linux-gnu
> and no issues.
>
> Ok for master?
>
> Thanks,
> Tamar
>
> gcc/ChangeLog:
>
> * expmed.cc (store_bit_field): Add parameter that indicates if value is
> still undefined and if so emit a subreg move instead.
> * expr.h (write_complex_part): Likewise.
> * expmed.h (store_bit_field): Add new parameter.
> * builtins.cc (expand_ifn_atomic_compare_exchange_into_call): Use new
> parameter.
> (expand_ifn_atomic_compare_exchange): Likewise.
> * calls.cc (store_unaligned_arguments_into_pseudos): Likewise.
> * emit-rtl.cc (validate_subreg): Likewise.
> * expr.cc (emit_group_store): Likewise.
> (copy_blkmode_from_reg): Likewise.
> (copy_blkmode_to_reg): Likewise.
> (clear_storage_hints): Likewise.
> (write_complex_part): Likewise.
> (emit_move_complex_parts): Likewise.
> (expand_assignment): Likewise.
> (store_expr): Likewise.
> (store_field): Likewise.
> (expand_expr_real_2): Likewise.
> * ifcvt.cc (noce_emit_move_insn): Likewise.
> * internal-fn.cc (expand_arith_set_overflow): Likewise.
> (expand_arith_overflow_result_store): Likewise.
> (expand_addsub_overflow): Likewise.
> (expand_neg_overflow): Likewise.
> (expand_mul_overflow): Likewise.
> (expand_arith_overflow): Likewise.
>
> gcc/testsuite/ChangeLog:
>
> * g++.target/aarch64/complex-init.C: New test.
>
> --- inline copy of patch ---
>
> diff --git a/gcc/builtins.cc b/gcc/builtins.cc
> index
> 4c6c29390531d8ae9765add598621727213b23ec..8c80e46d9c9c9c2a7e1ce0f8add86729fd542b16
> 100644
> --- a/gcc/builtins.cc
> +++ b/gcc/builtins.cc
> @@ -6014,8 +6014,8 @@ expand_ifn_atomic_compare_exchange_into_call (gcall
> *call, machine_mode mode)
> if (GET_MODE (boolret) != mode)
> boolret = convert_modes (mode, GET_MODE (boolret), boolret, 1);
> x = force_reg (mode, x);
> - write_complex_part (target, boolret, true);
> - write_complex_part (target, x, false);
> + write_complex_part (target, boolret, true, true);
> + write_complex_part (target, x, false, false);
> }
> }
>
> @@ -6070,8 +6070,8 @@ expand_ifn_atomic_compare_exchange (gcall *call)
> rtx target = expand_expr (lhs, NULL_RTX, VOIDmode, EXPAND_WRITE);
> if (GET_MODE (boolret) != mode)
> boolret = convert_modes (mode, GET_MODE (boolret), boolret, 1);
> - write_complex_part (target, boolret, true);
> - write_complex_part (target, oldval, false);
> + write_complex_part (target, boolret, true, true);
> + write_complex_part (target, oldval, false, false);
> }
> }
>
> diff --git a/gcc/calls.cc b/gcc/calls.cc
> index
> e13469cfd43b5bdd4ca0d2b8458a9e4f996e36e9..586af170879ab0152e9c0634a4b8e0ce03ea8d6e
> 100644
> --- a/gcc/calls.cc
> +++ b/gcc/calls.cc
> @@ -1214,7 +1214,7 @@ store_unaligned_arguments_into_pseudos (struct arg_data
> *args, int num_actuals)
>
> bytes -= bitsize / BITS_PER_UNIT;
> store_bit_field (reg, bitsize, endian_correction, 0, 0,
> - word_mode, word, false);
> + word_mode, word, false, false);
> }
> }
> }
> diff --git a/gcc/emit-rtl.cc b/gcc/emit-rtl.cc
> index
> f4404d7abe33b565358b7f609a91114c75ecf4e7..15ffca2ffe986bca56c1fae9381bd33f5d6b012d
> 100644
> --- a/gcc/emit-rtl.cc
> +++ b/gcc/emit-rtl.cc
> @@ -947,9 +947,11 @@ validate_subreg (machine_mode omode, machine_mode imode,
> && GET_MODE_INNER (omode) == GET_MODE_INNER (imode))
> ;
> /* Subregs involving floating point modes are not allowed to
> - change size. Therefore (subreg:DI (reg:DF) 0) is fine, but
> + change size unless it's an insert into a complex mode.
> + Therefore (subreg:DI (reg:DF) 0) and (subreg:CS (reg:SF) 0) are fine,
> but
> (subreg:SI (reg:DF) 0) isn't. */
> - else if (FLOAT_MODE_P (imode) || FLOAT_MODE_P (omode))
> + else if ((FLOAT_MODE_P (imode) || FLOAT_MODE_P (omode))
> + && !COMPLEX_MODE_P (omode))
> {
> if (! (known_eq (isize, osize)
> /* LRA can use subreg to store a floating point value in
> diff --git a/gcc/expmed.h b/gcc/expmed.h
> index
> ee1ddc82b601ce02957c493dad0d70eee2784ed7..0b2538c4c6bd51dfdc772ef70bdf631c0bed8717
> 100644
> --- a/gcc/expmed.h
> +++ b/gcc/expmed.h
> @@ -715,7 +715,7 @@ extern rtx expand_divmod (int, enum tree_code,
> machine_mode, rtx, rtx,
>
> extern void store_bit_field (rtx, poly_uint64, poly_uint64,
> poly_uint64, poly_uint64,
> - machine_mode, rtx, bool);
> + machine_mode, rtx, bool, bool);
> extern rtx extract_bit_field (rtx, poly_uint64, poly_uint64, int, rtx,
> machine_mode, machine_mode, bool, rtx *);
> extern rtx extract_low_bits (machine_mode, machine_mode, rtx);
> diff --git a/gcc/expmed.cc b/gcc/expmed.cc
> index
> ed39c88bd044279113f46661608c53b8a69d81a1..9c66cc40f60aadf5472b25770cb16d6e9f85a7e2
> 100644
> --- a/gcc/expmed.cc
> +++ b/gcc/expmed.cc
> @@ -1112,13 +1112,15 @@ store_integral_bit_field (rtx op0,
> opt_scalar_int_mode op0_mode,
>
> FIELDMODE is the machine-mode of the FIELD_DECL node for this field.
>
> - If REVERSE is true, the store is to be done in reverse order. */
> + If REVERSE is true, the store is to be done in reverse order.
> +
> + If UNDEFINED_P is true then STR_RTX is currently undefined. */
>
> void
> store_bit_field (rtx str_rtx, poly_uint64 bitsize, poly_uint64 bitnum,
> poly_uint64 bitregion_start, poly_uint64 bitregion_end,
> machine_mode fieldmode,
> - rtx value, bool reverse)
> + rtx value, bool reverse, bool undefined_p)
> {
> /* Handle -fstrict-volatile-bitfields in the cases where it applies. */
> unsigned HOST_WIDE_INT ibitsize = 0, ibitnum = 0;
> @@ -1160,6 +1162,18 @@ store_bit_field (rtx str_rtx, poly_uint64 bitsize,
> poly_uint64 bitnum,
> return;
> }
>
> + if (bitsize.is_constant (&ibitsize)
> + && bitnum.is_constant (&ibitnum)
> + && is_a <scalar_int_mode> (fieldmode, &int_mode)
> + && undefined_p
> + && ibitsize == GET_MODE_BITSIZE (int_mode))
> + {
> + gcc_assert (ibitnum % BITS_PER_UNIT == 0);
> + rtx dest = lowpart_subreg (GET_MODE (value), str_rtx, GET_MODE
> (str_rtx));
> + emit_move_insn (dest, value);
> + return;
> + }
> +
> /* Under the C++0x memory model, we must not touch bits outside the
> bit region. Adjust the address to start at the beginning of the
> bit region. */
> diff --git a/gcc/expr.h b/gcc/expr.h
> index
> 7e5cf495a2bf12e15e2a00d293dfb54f830f38dd..41447e023c7218db195e8db3725714cffb10b3f3
> 100644
> --- a/gcc/expr.h
> +++ b/gcc/expr.h
> @@ -253,7 +253,7 @@ extern rtx_insn *emit_move_insn_1 (rtx, rtx);
> extern rtx_insn *emit_move_complex_push (machine_mode, rtx, rtx);
> extern rtx_insn *emit_move_complex_parts (rtx, rtx);
> extern rtx read_complex_part (rtx, bool);
> -extern void write_complex_part (rtx, rtx, bool);
> +extern void write_complex_part (rtx, rtx, bool, bool);
> extern rtx read_complex_part (rtx, bool);
> extern rtx emit_move_resolve_push (machine_mode, rtx);
>
> diff --git a/gcc/expr.cc b/gcc/expr.cc
> index
> 5f7142b975ada2cd8b00663d35ba1e0004b8e28d..c7f057a87fbc92d81388c87dd3754b4d21af6612
> 100644
> --- a/gcc/expr.cc
> +++ b/gcc/expr.cc
> @@ -2850,7 +2850,7 @@ emit_group_store (rtx orig_dst, rtx src, tree type
> ATTRIBUTE_UNUSED,
> store_bit_field (dest,
> adj_bytelen * BITS_PER_UNIT, bytepos * BITS_PER_UNIT,
> bytepos * BITS_PER_UNIT, ssize * BITS_PER_UNIT - 1,
> - VOIDmode, tmps[i], false);
> + VOIDmode, tmps[i], false, false);
> }
>
> /* Optimize the access just a bit. */
> @@ -2864,7 +2864,7 @@ emit_group_store (rtx orig_dst, rtx src, tree type
> ATTRIBUTE_UNUSED,
>
> else
> store_bit_field (dest, bytelen * BITS_PER_UNIT, bytepos * BITS_PER_UNIT,
> - 0, 0, mode, tmps[i], false);
> + 0, 0, mode, tmps[i], false, false);
> }
>
> /* Copy from the pseudo into the (probable) hard reg. */
> @@ -2997,7 +2997,7 @@ copy_blkmode_from_reg (rtx target, rtx srcreg, tree
> type)
> xbitpos % BITS_PER_WORD, 1,
> NULL_RTX, copy_mode, copy_mode,
> false, NULL),
> - false);
> + false, false);
> }
> }
>
> @@ -3099,7 +3099,7 @@ copy_blkmode_to_reg (machine_mode mode_in, tree src)
> bitpos % BITS_PER_WORD, 1,
> NULL_RTX, word_mode, word_mode,
> false, NULL),
> - false);
> + false, false);
> }
>
> if (mode == BLKmode)
> @@ -3267,8 +3267,8 @@ clear_storage_hints (rtx object, rtx size, enum
> block_op_methods method,
> zero = CONST0_RTX (GET_MODE_INNER (mode));
> if (zero != NULL)
> {
> - write_complex_part (object, zero, 0);
> - write_complex_part (object, zero, 1);
> + write_complex_part (object, zero, 0, true);
> + write_complex_part (object, zero, 1, false);
> return NULL;
> }
> }
> @@ -3429,10 +3429,11 @@ set_storage_via_setmem (rtx object, rtx size, rtx
> val, unsigned int align,
>
>
>
> /* Write to one of the components of the complex value CPLX. Write VAL to
> - the real part if IMAG_P is false, and the imaginary part if its true. */
> + the real part if IMAG_P is false, and the imaginary part if its true.
> + If UNDEFINED_P then the value in CPLX is currently undefined. */
>
> void
> -write_complex_part (rtx cplx, rtx val, bool imag_p)
> +write_complex_part (rtx cplx, rtx val, bool imag_p, bool undefined_p)
> {
> machine_mode cmode;
> scalar_mode imode;
> @@ -3487,7 +3488,7 @@ write_complex_part (rtx cplx, rtx val, bool imag_p)
> }
>
> store_bit_field (cplx, ibitsize, imag_p ? ibitsize : 0, 0, 0, imode, val,
> - false);
> + false, undefined_p);
> }
>
> /* Extract one of the components of the complex value CPLX. Extract the
> @@ -3740,8 +3741,8 @@ emit_move_complex_parts (rtx x, rtx y)
> && REG_P (x) && !reg_overlap_mentioned_p (x, y))
> emit_clobber (x);
>
> - write_complex_part (x, read_complex_part (y, false), false);
> - write_complex_part (x, read_complex_part (y, true), true);
> + write_complex_part (x, read_complex_part (y, false), false, true);
> + write_complex_part (x, read_complex_part (y, true), true, false);
>
> return get_last_insn ();
> }
> @@ -5385,7 +5386,7 @@ expand_assignment (tree to, tree from, bool nontemporal)
> }
> else
> store_bit_field (mem, GET_MODE_BITSIZE (mode), 0, 0, 0, mode, reg,
> - false);
> + false, false);
> return;
> }
>
> @@ -5607,8 +5608,8 @@ expand_assignment (tree to, tree from, bool nontemporal)
> concat_store_slow:;
> rtx temp = assign_stack_temp (GET_MODE (to_rtx),
> GET_MODE_SIZE (GET_MODE (to_rtx)));
> - write_complex_part (temp, XEXP (to_rtx, 0), false);
> - write_complex_part (temp, XEXP (to_rtx, 1), true);
> + write_complex_part (temp, XEXP (to_rtx, 0), false, true);
> + write_complex_part (temp, XEXP (to_rtx, 1), true, false);
> result = store_field (temp, bitsize, bitpos,
> bitregion_start, bitregion_end,
> mode1, from, get_alias_set (to),
> @@ -6166,7 +6167,8 @@ store_expr (tree exp, rtx target, int call_param_p,
> store_bit_field (target,
> rtx_to_poly_int64 (expr_size (exp))
> * BITS_PER_UNIT,
> - 0, 0, 0, GET_MODE (temp), temp, reverse);
> + 0, 0, 0, GET_MODE (temp), temp, reverse,
> + false);
> }
> else
> convert_move (target, temp, TYPE_UNSIGNED (TREE_TYPE (exp)));
> @@ -7556,7 +7558,7 @@ store_field (rtx target, poly_int64 bitsize, poly_int64
> bitpos,
> gcc_checking_assert (known_ge (bitpos, 0));
> store_bit_field (target, bitsize, bitpos,
> bitregion_start, bitregion_end,
> - mode, temp, reverse);
> + mode, temp, reverse, false);
>
> return const0_rtx;
> }
> @@ -10012,8 +10014,8 @@ expand_expr_real_2 (sepops ops, rtx target,
> machine_mode tmode,
> complex_expr_swap_order:
> /* Move the imaginary (op1) and real (op0) parts to their
> location. */
> - write_complex_part (target, op1, true);
> - write_complex_part (target, op0, false);
> + write_complex_part (target, op1, true, true);
> + write_complex_part (target, op0, false, false);
>
> return target;
> }
> @@ -10042,8 +10044,8 @@ expand_expr_real_2 (sepops ops, rtx target,
> machine_mode tmode,
> }
>
> /* Move the real (op0) and imaginary (op1) parts to their location. */
> - write_complex_part (target, op0, false);
> - write_complex_part (target, op1, true);
> + write_complex_part (target, op0, false, true);
> + write_complex_part (target, op1, true, false);
>
> return target;
>
> @@ -10282,7 +10284,7 @@ expand_expr_real_2 (sepops ops, rtx target,
> machine_mode tmode,
> rtx dst = gen_reg_rtx (mode);
> emit_move_insn (dst, op0);
> store_bit_field (dst, bitsize, bitpos, 0, 0,
> - TYPE_MODE (TREE_TYPE (treeop1)), op1, false);
> + TYPE_MODE (TREE_TYPE (treeop1)), op1, false, false);
> return dst;
> }
>
> diff --git a/gcc/ifcvt.cc b/gcc/ifcvt.cc
> index
> 22960a67f893316563e46658fab8f06cf9cbeb80..149403586f4e220d27759a3c36cf5806d03f2040
> 100644
> --- a/gcc/ifcvt.cc
> +++ b/gcc/ifcvt.cc
> @@ -999,7 +999,8 @@ noce_emit_move_insn (rtx x, rtx y)
> }
>
> gcc_assert (start < (MEM_P (op) ? BITS_PER_UNIT : BITS_PER_WORD));
> - store_bit_field (op, size, start, 0, 0, GET_MODE (x), y, false);
> + store_bit_field (op, size, start, 0, 0, GET_MODE (x), y, false,
> + false);
> return;
> }
>
> @@ -1056,7 +1057,7 @@ noce_emit_move_insn (rtx x, rtx y)
> outmode = GET_MODE (outer);
> bitpos = SUBREG_BYTE (outer) * BITS_PER_UNIT;
> store_bit_field (inner, GET_MODE_BITSIZE (outmode), bitpos,
> - 0, 0, outmode, y, false);
> + 0, 0, outmode, y, false, false);
> }
>
> /* Return the CC reg if it is used in COND. */
> diff --git a/gcc/internal-fn.cc b/gcc/internal-fn.cc
> index
> 8b1733e20c4455e4e8c383c92fe859f4256cae69..8baf52f01516a0e8294176af68e69ec67e43278f
> 100644
> --- a/gcc/internal-fn.cc
> +++ b/gcc/internal-fn.cc
> @@ -735,9 +735,9 @@ expand_arith_set_overflow (tree lhs, rtx target)
> {
> if (TYPE_PRECISION (TREE_TYPE (TREE_TYPE (lhs))) == 1
> && !TYPE_UNSIGNED (TREE_TYPE (TREE_TYPE (lhs))))
> - write_complex_part (target, constm1_rtx, true);
> + write_complex_part (target, constm1_rtx, true, false);
> else
> - write_complex_part (target, const1_rtx, true);
> + write_complex_part (target, const1_rtx, true, false);
> }
>
> /* Helper for expand_*_overflow. Store RES into the __real__ part
> @@ -792,7 +792,7 @@ expand_arith_overflow_result_store (tree lhs, rtx target,
> expand_arith_set_overflow (lhs, target);
> emit_label (done_label);
> }
> - write_complex_part (target, lres, false);
> + write_complex_part (target, lres, false, false);
> }
>
> /* Helper for expand_*_overflow. Store RES into TARGET. */
> @@ -837,7 +837,7 @@ expand_addsub_overflow (location_t loc, tree_code code,
> tree lhs,
> {
> target = expand_expr (lhs, NULL_RTX, VOIDmode, EXPAND_WRITE);
> if (!is_ubsan)
> - write_complex_part (target, const0_rtx, true);
> + write_complex_part (target, const0_rtx, true, false);
> }
>
> /* We assume both operands and result have the same precision
> @@ -1282,7 +1282,7 @@ expand_neg_overflow (location_t loc, tree lhs, tree
> arg1, bool is_ubsan,
> {
> target = expand_expr (lhs, NULL_RTX, VOIDmode, EXPAND_WRITE);
> if (!is_ubsan)
> - write_complex_part (target, const0_rtx, true);
> + write_complex_part (target, const0_rtx, true, false);
> }
>
> enum insn_code icode = optab_handler (negv3_optab, mode);
> @@ -1407,7 +1407,7 @@ expand_mul_overflow (location_t loc, tree lhs, tree
> arg0, tree arg1,
> {
> target = expand_expr (lhs, NULL_RTX, VOIDmode, EXPAND_WRITE);
> if (!is_ubsan)
> - write_complex_part (target, const0_rtx, true);
> + write_complex_part (target, const0_rtx, true, false);
> }
>
> if (is_ubsan)
> @@ -2224,7 +2224,7 @@ expand_mul_overflow (location_t loc, tree lhs, tree
> arg0, tree arg1,
> do_compare_rtx_and_jump (op1, res, NE, true, mode, NULL_RTX, NULL,
> all_done_label,
> profile_probability::very_unlikely ());
> emit_label (set_noovf);
> - write_complex_part (target, const0_rtx, true);
> + write_complex_part (target, const0_rtx, true, false);
> emit_label (all_done_label);
> }
>
> @@ -2493,7 +2493,7 @@ expand_arith_overflow (enum tree_code code, gimple
> *stmt)
> {
> /* The infinity precision result will always fit into result. */
> rtx target = expand_expr (lhs, NULL_RTX, VOIDmode, EXPAND_WRITE);
> - write_complex_part (target, const0_rtx, true);
> + write_complex_part (target, const0_rtx, true, false);
> scalar_int_mode mode = SCALAR_INT_TYPE_MODE (type);
> struct separate_ops ops;
> ops.code = code;
> diff --git a/gcc/testsuite/g++.target/aarch64/complex-init.C
> b/gcc/testsuite/g++.target/aarch64/complex-init.C
> new file mode 100644
> index
> 0000000000000000000000000000000000000000..d3fd3e88d04a87bacf1c4ee74ce25282c6ff81e8
> --- /dev/null
> +++ b/gcc/testsuite/g++.target/aarch64/complex-init.C
> @@ -0,0 +1,40 @@
> +/* { dg-do compile } */
> +/* { dg-options "-O2" } */
> +/* { dg-final { check-function-bodies "**" "" "" { target { le } } } } */
> +
> +/*
> +** _Z1fii:
> +** ...
> +** bfi x0, x1, 32, 32
> +** ret
> +** ...
> +*/
> +_Complex int f(int a, int b) {
> + _Complex int t = a + b * 1i;
> + return t;
> +}
> +
> +/*
> +** _Z2f2ii:
> +** ...
> +** bfi x0, x1, 32, 32
> +** ret
> +** ...
> +*/
> +_Complex int f2(int a, int b) {
> + _Complex int t = {a, b};
> + return t;
> +}
> +
> +/*
> +** _Z12f_convolutedii:
> +** ...
> +** bfi x0, x1, 32, 32
> +** ret
> +** ...
> +*/
> +_Complex int f_convoluted(int a, int b) {
> + _Complex int t = (_Complex int)a;
> + __imag__ t = b;
> + return t;
> +}
