From: Richard Henderson <rth@twiddle.net>
To: Stefan Weil <sw@weilnetz.de>, qemu-devel@nongnu.org
Cc: peter.maydell@linaro.org
Subject: Re: [Qemu-devel] [PATCH v2 3/4] tcg: Mask shift counts to avoid undefined behavior
Date: Wed, 19 Mar 2014 08:25:23 -0700 [thread overview]
Message-ID: <5329B6E3.5030002@twiddle.net> (raw)
In-Reply-To: <53293783.3050509@weilnetz.de>
On 03/18/2014 11:21 PM, Stefan Weil wrote:
> Are there test cases which fail with the old code?
Only when running under analysis tools looking for technical violations of the
standard. Under normal circumstances it would never crash since, as with the
native backends, the underlying cpu is going to treat this some rational way.
But I sincerely doubt that we could measure any performance loss in TCI. The
single extra arithmetic operation should be swallowed by the loop back to
interpret the next opcode.
r~
next prev parent reply other threads:[~2014-03-19 15:25 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-03-18 21:30 [Qemu-devel] [PATCH v2 0/4] tcg: out of range shift behavior Richard Henderson
2014-03-18 21:30 ` [Qemu-devel] [PATCH v2 1/4] tcg: Use "unspecified behavior" for shifts Richard Henderson
2014-03-18 21:30 ` [Qemu-devel] [PATCH v2 2/4] tcg: Mask shift quantities while folding Richard Henderson
2014-03-18 22:11 ` Peter Maydell
2014-03-18 21:30 ` [Qemu-devel] [PATCH v2 3/4] tcg: Mask shift counts to avoid undefined behavior Richard Henderson
2014-03-18 22:24 ` Richard Henderson
2014-03-19 6:21 ` Stefan Weil
2014-03-19 10:11 ` Peter Maydell
2014-03-19 15:25 ` Richard Henderson [this message]
2014-03-19 15:59 ` Peter Maydell
2014-03-18 21:30 ` [Qemu-devel] [PATCH v2 4/4] tcg: Fix out of range shift in deposit optimizations Richard Henderson
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