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From: Peter Maydell <peter.maydell@linaro.org>
To: Richard Henderson <rth@twiddle.net>
Cc: "QEMU Developers" <qemu-devel@nongnu.org>,
	"Emilio G. Cota" <cota@braap.org>,
	"Alex Bennée" <alex.bennee@linaro.org>,
	"Paolo Bonzini" <pbonzini@redhat.com>,
	"Sergey Fedorov" <serge.fdrv@gmail.com>
Subject: Re: [Qemu-devel] [PATCH v2 06/27] int128: Use complex numbers if advisable
Date: Mon, 4 Jul 2016 13:07:55 +0100	[thread overview]
Message-ID: <CAFEAcA_SC29k55k9Nq+2Mj2XjVdoBh0xBjjpyjOJvpjd=5zYzA@mail.gmail.com> (raw)
In-Reply-To: <1467392693-22715-7-git-send-email-rth@twiddle.net>

On 1 July 2016 at 18:04, Richard Henderson <rth@twiddle.net> wrote:
> If __int128 is not supported, prefer a base type that is
> returned in registers rather than memory.

So which host architectures does this improve?
128 bit integers are nothing to do with complex numbers,
so we ought to have a strong justification for abusing
the _Complex type.

The ifdef suggests this only helps ppc and sparc, which
to my mind is not a sufficient justification.

If there's much benefit from doing this then it would be
better for the compiler on those architectures to support
int128 as a proper native type returned in registers.

> +#if defined(__GNUC__) \
> +    && (defined(__powerpc__) || defined(__sparc__)) \
> +    && !defined(CONFIG_TCG_INTERPRETER)

Why the CONFIG_TCG_INTERPRETER clause ?

thanks
-- PMM

  parent reply	other threads:[~2016-07-04 12:08 UTC|newest]

Thread overview: 48+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2016-07-01 17:04 [Qemu-devel] [PATCH v2 00/27] cmpxchg-based emulation of atomics Richard Henderson
2016-07-01 17:04 ` [Qemu-devel] [PATCH v2 01/27] atomics: add atomic_xor Richard Henderson
2016-08-11 17:19   ` Alex Bennée
2016-07-01 17:04 ` [Qemu-devel] [PATCH v2 02/27] atomics: add atomic_op_fetch variants Richard Henderson
2016-08-11 17:20   ` Alex Bennée
2016-07-01 17:04 ` [Qemu-devel] [PATCH v2 03/27] exec: Avoid direct references to Int128 parts Richard Henderson
2016-07-01 17:04 ` [Qemu-devel] [PATCH v2 04/27] int128: Use __int128 if available Richard Henderson
2016-08-11 10:45   ` Alex Bennée
2016-08-25 19:09   ` [Qemu-devel] [PATCH] fixup! " Alex Bennée
2016-08-26 12:48     ` no-reply
2016-07-01 17:04 ` [Qemu-devel] [PATCH v2 06/27] int128: Use complex numbers if advisable Richard Henderson
2016-07-04 11:51   ` Paolo Bonzini
2016-07-04 12:07   ` Peter Maydell [this message]
2016-07-01 17:04 ` [Qemu-devel] [PATCH v2 07/27] tcg: Add EXCP_ATOMIC Richard Henderson
2016-09-08  8:38   ` Alex Bennée
2016-09-08 16:26     ` Richard Henderson
2016-07-01 17:04 ` [Qemu-devel] [PATCH v2 08/27] HACK: Always enable parallel_cpus Richard Henderson
2016-09-08  8:39   ` Alex Bennée
2016-09-08 16:22     ` Richard Henderson
2016-07-01 17:04 ` [Qemu-devel] [PATCH v2 09/27] tcg: Add atomic helpers Richard Henderson
2016-09-08 13:43   ` Alex Bennée
2016-09-08 16:08     ` Richard Henderson
2016-07-01 17:04 ` [Qemu-devel] [PATCH v2 10/27] tcg: Add atomic128 helpers Richard Henderson
2016-07-08  3:00   ` Emilio G. Cota
2016-07-08  5:26     ` Richard Henderson
2016-08-11 10:02   ` Alex Bennée
2016-07-01 17:04 ` [Qemu-devel] [PATCH v2 11/27] target-i386: emulate LOCK'ed cmpxchg using cmpxchg helpers Richard Henderson
2016-07-08  3:08   ` Emilio G. Cota
2016-07-08  3:19     ` Emilio G. Cota
2016-07-01 17:04 ` [Qemu-devel] [PATCH v2 12/27] target-i386: emulate LOCK'ed OP instructions using atomic helpers Richard Henderson
2016-07-01 17:04 ` [Qemu-devel] [PATCH v2 13/27] target-i386: emulate LOCK'ed INC using atomic helper Richard Henderson
2016-07-01 17:04 ` [Qemu-devel] [PATCH v2 14/27] target-i386: emulate LOCK'ed NOT " Richard Henderson
2016-07-01 17:04 ` [Qemu-devel] [PATCH v2 15/27] target-i386: emulate LOCK'ed NEG using cmpxchg helper Richard Henderson
2016-07-01 17:04 ` [Qemu-devel] [PATCH v2 16/27] target-i386: emulate LOCK'ed XADD using atomic helper Richard Henderson
2016-07-01 17:04 ` [Qemu-devel] [PATCH v2 17/27] target-i386: emulate LOCK'ed BTX ops using atomic helpers Richard Henderson
2016-07-01 17:04 ` [Qemu-devel] [PATCH v2 18/27] target-i386: emulate XCHG using atomic helper Richard Henderson
2016-07-01 17:04 ` [Qemu-devel] [PATCH v2 19/27] target-i386: remove helper_lock() Richard Henderson
2016-07-01 17:04 ` [Qemu-devel] [PATCH v2 20/27] tests: add atomic_add-bench Richard Henderson
2016-07-01 17:04 ` [Qemu-devel] [PATCH v2 21/27] target-arm: Rearrange aa32 load and store functions Richard Henderson
2016-07-01 17:04 ` [Qemu-devel] [PATCH v2 22/27] target-arm: emulate LL/SC using cmpxchg helpers Richard Henderson
2016-07-01 17:04 ` [Qemu-devel] [PATCH v2 23/27] target-arm: emulate SWP with atomic_xchg helper Richard Henderson
2016-07-01 17:04 ` [Qemu-devel] [PATCH v2 24/27] target-arm: emulate aarch64's LL/SC using cmpxchg helpers Richard Henderson
2016-07-08  3:34   ` Emilio G. Cota
2016-07-01 17:04 ` [Qemu-devel] [PATCH v2 25/27] linux-user: remove handling of ARM's EXCP_STREX Richard Henderson
2016-07-01 17:04 ` [Qemu-devel] [PATCH v2 26/27] linux-user: remove handling of aarch64's EXCP_STREX Richard Henderson
2016-07-01 17:04 ` [Qemu-devel] [PATCH v2 27/27] target-arm: remove EXCP_STREX + cpu_exclusive_{test, info} Richard Henderson
2016-07-01 17:23 ` [Qemu-devel] [PATCH v2 00/27] cmpxchg-based emulation of atomics Richard Henderson
2016-07-08  2:53 ` Emilio G. Cota

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