From: Jiufu Guo <guojiufu@linux.ibm.com>
To: Segher Boessenkool <segher@kernel.crashing.org>
Cc: gcc-patches@gcc.gnu.org, dje.gcc@gmail.com, linkw@gcc.gnu.org,
bergner@linux.ibm.com, rguenther@suse.de,
richard.sandiford@arm.com, jeffreyalaw@gmail.com
Subject: Re: [PATCH] rs6000: replace '(const_int 0)' to 'unspec:BLK [(const_int 0)]' for stack_tie
Date: Wed, 14 Jun 2023 12:06:29 +0800 [thread overview]
Message-ID: <7no7liadru.fsf@ltcden2-lp1.aus.stglabs.ibm.com> (raw)
In-Reply-To: <20230613183320.GU19790@gate.crashing.org> (Segher Boessenkool's message of "Tue, 13 Jun 2023 13:33:20 -0500")
Hi,
Segher Boessenkool <segher@kernel.crashing.org> writes:
> Hi!
>
> As I said in a reply to the original patch: not okay. Sorry.
Thanks a lot for your comments!
I'm also thinking about other solutions:
1. "set (mem/c:BLK (reg/f:DI 1 1) (const_int 0 [0])"
This is the existing pattern. It may be read as an action
to clean an unknown-size memory block.
2. "set (mem/c:BLK (reg/f:DI 1 1) unspec:blk (const_int 0 [0])
UNSPEC_TIE".
Current patch is using this one.
3. "set (mem/c:DI (reg/f:DI 1 1) unspec:DI (const_int 0 [0])
UNSPEC_TIE".
This avoids using BLK on unspec, but using DI.
4. "set (mem/c:BLK (reg/f:DI 1 1) unspec (const_int 0 [0])
UNSPEC_TIE"
There is still a mode for the unspec.
>
> But some comments on this patch:
>
> On Tue, Jun 13, 2023 at 08:23:35PM +0800, Jiufu Guo wrote:
>> + && XINT (SET_SRC (set), 1) == UNSPEC_TIE
>> + && XVECEXP (SET_SRC (set), 0, 0) == const0_rtx);
>
> This makes it required that the operand of an UNSPEC_TIE unspec is a
> const_int 0. This should be documented somewhere. Ideally you would
> want no operand at all here, but every unspec has an operand.
Right! Since checked UNSPEC_TIE arleady, we may not need to check
the inner operand. Like " && XINT (SET_SRC (set), 1) == UNSPEC_TIE);".
>
>> + RTVEC_ELT (p, i)
>> + = gen_rtx_SET (mem, gen_rtx_UNSPEC (BLKmode, gen_rtvec (1, const0_rtx),
>> + UNSPEC_TIE));
>
> If it is hard to indent your code, your code is trying to do to much.
> Just have an extra temporary?
>
> rtx un = gen_rtx_UNSPEC (BLKmode, gen_rtvec (1, const0_rtx), UNSPEC_TIE);
> RTVEC_ELT (p, i) = gen_rtx_SET (mem, un);
>
> That is shorter even, and certainly more readable :-)
Yeap, thanks!
>
>> @@ -10828,7 +10829,9 @@ (define_expand "restore_stack_block"
>> operands[4] = gen_frame_mem (Pmode, operands[1]);
>> p = rtvec_alloc (1);
>> RTVEC_ELT (p, 0) = gen_rtx_SET (gen_frame_mem (BLKmode, operands[0]),
>> - const0_rtx);
>> + gen_rtx_UNSPEC (BLKmode,
>> + gen_rtvec (1, const0_rtx),
>> + UNSPEC_TIE));
>> operands[5] = gen_rtx_PARALLEL (VOIDmode, p);
>
> I have a hard time to see how this could ever be seen as clearer or more
> obvious or anything like that :-(
I was thinking about just invoking gen_stack_tie here.
BR,
Jeff (Jiufu Guo)
>
>
> Segher
next prev parent reply other threads:[~2023-06-14 4:06 UTC|newest]
Thread overview: 33+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-06-13 12:23 Jiufu Guo
2023-06-13 12:48 ` Xi Ruoyao
2023-06-14 1:55 ` Jiufu Guo
2023-06-14 9:18 ` Xi Ruoyao
2023-06-14 15:05 ` Segher Boessenkool
2023-06-15 7:59 ` Jiufu Guo
2023-06-13 18:33 ` Segher Boessenkool
2023-06-14 4:06 ` Jiufu Guo [this message]
2023-06-14 7:59 ` Richard Biener
2023-06-14 9:04 ` Richard Sandiford
2023-06-14 9:22 ` Richard Biener
2023-06-14 9:43 ` Richard Sandiford
2023-06-14 9:52 ` Richard Biener
2023-06-14 10:02 ` Richard Sandiford
2023-06-14 16:08 ` Segher Boessenkool
2023-06-14 16:32 ` Segher Boessenkool
2023-06-14 9:29 ` Jiufu Guo
2023-06-14 16:38 ` Segher Boessenkool
2023-06-14 9:26 ` Jiufu Guo
2023-06-14 15:45 ` Segher Boessenkool
2023-06-14 15:38 ` Segher Boessenkool
2023-06-14 16:25 ` Richard Biener
2023-06-14 17:03 ` Segher Boessenkool
2023-06-14 15:15 ` Segher Boessenkool
2023-06-15 7:00 ` Jiufu Guo
2023-06-15 16:30 ` Segher Boessenkool
2023-06-16 2:24 ` Jiufu Guo
-- strict thread matches above, loose matches on Subject: below --
2023-06-12 13:19 Jiufu Guo
2023-06-13 0:24 ` David Edelsohn
2023-06-13 2:15 ` Jiufu Guo
2023-06-13 18:14 ` Segher Boessenkool
2023-06-13 18:59 ` David Edelsohn
2023-06-14 3:00 ` Jiufu Guo
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