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[67.216.151.25]) by smtp.gmail.com with ESMTPSA id y205sm890128ywc.6.2019.10.09.15.26.17 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Wed, 09 Oct 2019 15:26:17 -0700 (PDT) Subject: Re: [PATCH] RISC-V: fcvt can set fflags, so set FS accordingly To: Palmer Dabbelt , qemu-riscv@nongnu.org References: <20191009211541.9937-1-palmer@sifive.com> From: Richard Henderson Openpgp: preference=signencrypt Message-ID: <6acbc2de-66b2-a363-cbaa-bf1f458fdf62@linaro.org> Date: Wed, 9 Oct 2019 18:26:15 -0400 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.8.0 MIME-Version: 1.0 In-Reply-To: <20191009211541.9937-1-palmer@sifive.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit X-detected-operating-system: by eggs.gnu.org: Genre and OS details not recognized. X-Received-From: 2607:f8b0:4864:20::b41 X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: qemu-devel@nongnu.org Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On 10/9/19 5:15 PM, Palmer Dabbelt wrote: > A user pinged me to say "my floating point heavy code works in user mode > but not system mode", which I'm guessing is the result of a lazy FP > save/restore issue as those still crop up from time to time as long tail > bugs. I figured it was worth giving the FP stuff a look to see if > anything jumps out, and it turns out that there is a bug: converting > float to integer can set the invalid flag, which is supposed to mark FS > as dirty, but the emulation routine doesn't do so. > > This patch unconditionally marks FS as dirty for fcvt instructions that > convert into X registers (fcvt into F registers already did so). I > haven't actually tried to manifest a bug here, but as far as I can tell > the soft float stuff does set the invalid flag. > > Signed-off-by: Palmer Dabbelt > --- > target/riscv/insn_trans/trans_rvd.inc.c | 2 ++ > target/riscv/insn_trans/trans_rvf.inc.c | 4 ++++ > 2 files changed, 6 insertions(+) Reviewed-by: Richard Henderson r~