From: Richard Henderson <rth@twiddle.net>
To: Peter Maydell <peter.maydell@linaro.org>
Cc: qemu-devel@nongnu.org, patches@linaro.org
Subject: Re: [Qemu-devel] [PATCH 1/2] target-arm: Use sextract32() in branch decode
Date: Fri, 23 Aug 2013 11:09:14 -0700 [thread overview]
Message-ID: <5217A54A.6040300@twiddle.net> (raw)
In-Reply-To: <1377274359-8707-2-git-send-email-peter.maydell@linaro.org>
On 08/23/2013 09:12 AM, Peter Maydell wrote:
> - offset = (((int32_t)insn << 8) >> 8);
> - val += (offset << 2) + 4;
> + offset = sextract32(insn << 2, 0, 26);
> + val += offset + 4;
I read this incorrectly at first, considering the shift of insn, and
I wonder if it's really the best way to write this because of that.
What about just changing the one line to sextract(insn, 0, 24)?
The second line by itself ought not trigger a warning from clang,
because the << 2 never changes the sign bit. If it still does,
perhaps just multiply by 4 instead...
It's a stupid warning. When was the last ones-compliment machine built?
r~
next prev parent reply other threads:[~2013-08-23 18:09 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-08-23 16:12 [Qemu-devel] [PATCH 0/2] target-arm: Avoid clang sanitizer warnings Peter Maydell
2013-08-23 16:12 ` [Qemu-devel] [PATCH 1/2] target-arm: Use sextract32() in branch decode Peter Maydell
2013-08-23 18:09 ` Richard Henderson [this message]
2013-08-24 10:21 ` Peter Maydell
2013-08-23 16:12 ` [Qemu-devel] [PATCH 2/2] target-arm: Avoid "1 << 31" undefined behaviour Peter Maydell
2013-08-23 18:11 ` Richard Henderson
2013-08-24 10:38 ` Peter Maydell
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