From: "Maciej W. Rozycki" <macro@linux-mips.org>
To: Fredrik Noring <noring@nocrew.org>
Cc: "Richard Henderson" <richard.henderson@linaro.org>,
"Aleksandar Markovic" <amarkovic@wavecomp.com>,
"Philippe Mathieu-Daudé" <f4bug@amsat.org>,
"Aurelien Jarno" <aurelien@aurel32.net>,
"qemu-devel@nongnu.org Developers" <qemu-devel@nongnu.org>,
"Jürgen Urban" <JuergenUrban@gmx.de>
Subject: Re: [Qemu-devel] [PATCH] target/mips: Support Toshiba specific three-operand MADD and MADDU
Date: Tue, 16 Oct 2018 20:02:03 +0100 (BST) [thread overview]
Message-ID: <alpine.LFD.2.21.1810161955490.16498@eddie.linux-mips.org> (raw)
In-Reply-To: <20181016185250.GC2323@sx9>
On Tue, 16 Oct 2018, Fredrik Noring wrote:
> > I would not implement r5900 for mips32 in that case,
> > I would implement it only for TARGET_MIPS64.
>
> R5900 Linux implements the O32 ABI, which is why 32-bit QEMU user-mode is
> very useful. Perhaps a better alternative is to define the MMI registers
> as 128-bit, similar to
>
> static TCGv_u128 mmi_gpr[32];
>
> and then copy cpu_gpr to/from mmi_gpr as needed when running the MMIs?
FWIW, I agree as far as the user emulation mode is concerned. All 64-bit
MIPS hardware is currently set up by the Linux kernel for 64-bit execution
by keeping CP0.Status.UX set when running o32 user processes anyway.
A change to this policy (and also the use of CP0.Status.PX for n32) has
been discussed, in partictular in the course of investigating address
space overflows caused by GCC using the indexed addressing modes under the
assumption that the address space wraps at 32 bits for o32 and n32
software, where indeed it does not. No change has been implemented
though.
Maciej
next prev parent reply other threads:[~2018-10-16 19:02 UTC|newest]
Thread overview: 21+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-10-14 14:29 [Qemu-devel] [PATCH] target/mips: Support Toshiba specific three-operand MADD and MADDU Philippe Mathieu-Daudé
2018-10-14 16:41 ` Fredrik Noring
2018-10-14 21:56 ` Philippe Mathieu-Daudé
2018-10-14 23:03 ` Maciej W. Rozycki
2018-10-15 17:02 ` Fredrik Noring
2018-10-16 9:43 ` Aleksandar Markovic
2018-10-16 18:19 ` Fredrik Noring
2018-10-16 18:37 ` Richard Henderson
2018-10-16 18:52 ` Fredrik Noring
2018-10-16 19:02 ` Maciej W. Rozycki [this message]
2018-10-19 18:09 ` Aleksandar Markovic
2018-10-28 19:43 ` Aleksandar Markovic
2018-10-28 20:00 ` Maciej W. Rozycki
2018-10-29 11:52 ` Aleksandar Markovic
2018-10-29 14:51 ` Fredrik Noring
2018-10-29 15:03 ` Aleksandar Markovic
2018-10-29 15:44 ` Maciej W. Rozycki
2018-10-16 18:55 ` Maciej W. Rozycki
2018-10-15 15:36 ` Fredrik Noring
2018-10-24 18:01 ` Fredrik Noring
2018-10-26 11:17 ` Aleksandar Markovic
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