From: Christophe Leroy <christophe.leroy@c-s.fr>
To: Segher Boessenkool <segher@kernel.crashing.org>
Cc: Alistair Popple <alistair@popple.id.au>,
npiggin@gmail.com, bala24@linux.ibm.com,
Jordan Niethe <jniethe5@gmail.com>,
linuxppc-dev@lists.ozlabs.org, dja@axtens.net
Subject: Re: [PATCH v5 18/21] powerpc64: Add prefixed instructions to instruction data type
Date: Wed, 8 Apr 2020 20:43:52 +0200 [thread overview]
Message-ID: <7e93f6e2-9bcf-654d-9260-e9206f9949ba@c-s.fr> (raw)
In-Reply-To: <20200408181101.GG26902@gate.crashing.org>
Le 08/04/2020 à 20:11, Segher Boessenkool a écrit :
> On Mon, Apr 06, 2020 at 12:25:27PM +0200, Christophe Leroy wrote:
>>> if (ppc_inst_prefixed(x) != ppc_inst_prefixed(y))
>>> return false;
>>> else if (ppc_inst_prefixed(x))
>>> return !memcmp(&x, &y, sizeof(struct ppc_inst));
>>
>> Are we sure memcmp() is a good candidate for the comparison ? Can we do
>> simpler ? Especially, I understood a prefixed instruction is a 64 bits
>> properly aligned instruction, can we do a simple u64 compare ? Or is GCC
>> intelligent enough to do that without calling memcmp() function which is
>> heavy ?
>
> A prefixed insn is *not* 8-byte aligned, it is 4-byte aligned, fwiw.
Ah, yes, I read too fast https://patchwork.ozlabs.org/patch/1266721/
It's not 64 bits, it is 64 bytes.
>
> memcmp() isn't as heavy as you fear, not with a non-ancient GCC at least.
> But this could be written in a nicer way, sure :-)
>
>
> Segher
>
Christophe
next prev parent reply other threads:[~2020-04-08 18:46 UTC|newest]
Thread overview: 71+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-04-06 8:09 [PATCH v5 00/21] Initial Prefixed Instruction support Jordan Niethe
2020-04-06 8:09 ` [PATCH v5 01/21] powerpc/xmon: Remove store_inst() for patch_instruction() Jordan Niethe
2020-04-06 8:09 ` [PATCH v5 02/21] powerpc/xmon: Move out-of-line instructions to text section Jordan Niethe
2020-04-07 6:45 ` Balamuruhan S
2020-04-09 6:11 ` Christophe Leroy
2020-04-09 7:26 ` Jordan Niethe
2020-04-06 8:09 ` [PATCH v5 03/21] powerpc: Change calling convention for create_branch() et. al Jordan Niethe
2020-04-06 10:25 ` kbuild test robot
2020-04-06 10:25 ` kbuild test robot
2020-04-07 6:10 ` Balamuruhan S
2020-04-07 6:35 ` Jordan Niethe
2020-04-07 6:59 ` Balamuruhan S
2020-04-06 8:09 ` [PATCH v5 04/21] powerpc: Use a macro for creating instructions from u32s Jordan Niethe
2020-04-07 6:40 ` Balamuruhan S
2020-04-07 8:27 ` Jordan Niethe
2020-04-06 8:09 ` [PATCH v5 05/21] powerpc: Use a function for getting the instruction op code Jordan Niethe
2020-04-06 8:22 ` Christophe Leroy
2020-04-06 9:38 ` Jordan Niethe
2020-04-07 7:04 ` Balamuruhan S
2020-04-07 8:32 ` Jordan Niethe
2020-04-08 18:21 ` Segher Boessenkool
2020-04-09 4:48 ` Jordan Niethe
2020-04-06 8:09 ` [PATCH v5 06/21] powerpc: Use an accessor for instructions Jordan Niethe
2020-04-06 8:09 ` [PATCH v5 07/21] powerpc: Use a function for byte swapping instructions Jordan Niethe
2020-04-07 7:42 ` Balamuruhan S
2020-04-06 8:09 ` [PATCH v5 08/21] powerpc: Introduce functions for instruction equality Jordan Niethe
2020-04-07 7:37 ` Balamuruhan S
2020-04-06 8:09 ` [PATCH v5 09/21] powerpc: Use a datatype for instructions Jordan Niethe
2020-04-06 10:34 ` kbuild test robot
2020-04-06 10:34 ` kbuild test robot
2020-04-06 10:35 ` kbuild test robot
2020-04-06 10:35 ` kbuild test robot
2020-04-07 10:30 ` Balamuruhan S
2020-04-08 2:11 ` Jordan Niethe
2020-04-06 8:09 ` [PATCH v5 10/21] powerpc: Use a function for reading instructions Jordan Niethe
2020-04-07 10:42 ` Balamuruhan S
2020-04-06 8:09 ` [PATCH v5 11/21] powerpc: Define and use __get_user_instr{, inatomic}() Jordan Niethe
2020-04-07 10:48 ` Balamuruhan S
2020-04-08 2:13 ` Jordan Niethe
2020-04-06 8:09 ` [PATCH v5 12/21] powerpc: Introduce a function for reporting instruction length Jordan Niethe
2020-04-07 11:14 ` Balamuruhan S
2020-04-08 2:14 ` Jordan Niethe
2020-04-06 8:09 ` [PATCH v5 13/21] powerpc/xmon: Use a function for reading instructions Jordan Niethe
2020-04-07 11:30 ` Balamuruhan S
2020-04-08 2:18 ` Jordan Niethe
2020-04-09 5:04 ` Balamuruhan S
2020-04-09 5:14 ` Jordan Niethe
2020-04-06 8:09 ` [PATCH v5 14/21] powerpc/xmon: Move insertion of breakpoint for xol'ing Jordan Niethe
2020-04-06 8:09 ` [PATCH v5 15/21] powerpc: Make test_translate_branch() independent of instruction length Jordan Niethe
2020-04-06 8:09 ` [PATCH v5 16/21] powerpc: Enable Prefixed Instructions Jordan Niethe
2020-04-06 8:09 ` [PATCH v5 17/21] powerpc: Define new SRR1 bits for a future ISA version Jordan Niethe
2020-04-06 8:09 ` [PATCH v5 18/21] powerpc64: Add prefixed instructions to instruction data type Jordan Niethe
2020-04-06 9:52 ` Alistair Popple
2020-04-06 10:25 ` Christophe Leroy
2020-04-06 11:13 ` Jordan Niethe
2020-04-08 18:11 ` Segher Boessenkool
2020-04-08 18:43 ` Christophe Leroy [this message]
2020-04-06 10:42 ` Jordan Niethe
2020-04-07 1:39 ` Alistair Popple
2020-04-06 11:04 ` kbuild test robot
2020-04-06 11:04 ` kbuild test robot
2020-04-13 12:04 ` Balamuruhan S
2020-04-15 4:40 ` Jordan Niethe
2020-04-15 8:14 ` Balamuruhan S
2020-04-06 8:09 ` [PATCH v5 19/21] powerpc: Support prefixed instructions in alignment handler Jordan Niethe
2020-04-06 8:09 ` [PATCH v5 20/21] powerpc sstep: Add support for prefixed load/stores Jordan Niethe
2020-04-06 11:29 ` kbuild test robot
2020-04-06 11:29 ` kbuild test robot
2020-04-06 8:09 ` [PATCH v5 21/21] powerpc sstep: Add support for prefixed fixed-point arithmetic Jordan Niethe
2020-04-09 6:39 ` [PATCH v5 00/21] Initial Prefixed Instruction support Christophe Leroy
2020-04-09 7:28 ` Jordan Niethe
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