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[216.160.65.90]) by smtp.gmail.com with ESMTPSA id v28sm4728708pgn.81.2020.07.23.20.55.19 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 23 Jul 2020 20:55:20 -0700 (PDT) Subject: Re: [PATCH v2 1/7] target/riscv: Generate nanboxed results from fp helpers To: LIU Zhiwei , qemu-devel@nongnu.org References: <20200724002807.441147-1-richard.henderson@linaro.org> <20200724002807.441147-2-richard.henderson@linaro.org> <1aa6cb56-2f41-45c1-2d32-ec8b3b10780b@c-sky.com> From: Richard Henderson Message-ID: <9e10c17c-7a9e-5f7f-b1e3-c195d4e30b32@linaro.org> Date: Thu, 23 Jul 2020 20:55:18 -0700 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.10.0 MIME-Version: 1.0 In-Reply-To: <1aa6cb56-2f41-45c1-2d32-ec8b3b10780b@c-sky.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 8bit Received-SPF: pass client-ip=2607:f8b0:4864:20::443; envelope-from=richard.henderson@linaro.org; helo=mail-pf1-x443.google.com X-detected-operating-system: by eggs.gnu.org: No matching host in p0f cache. That's all we know. X-Spam_score_int: -20 X-Spam_score: -2.1 X-Spam_bar: -- X-Spam_report: (-2.1 / 5.0 requ) BAYES_00=-1.9, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action 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: frank.chang@sifive.com, alistair23@gmail.com, qemu-riscv@nongnu.org Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On 7/23/20 7:35 PM, LIU Zhiwei wrote: > > > On 2020/7/24 8:28, Richard Henderson wrote: >> Make sure that all results from single-precision scalar helpers >> are properly nan-boxed to 64-bits. >> >> Signed-off-by: Richard Henderson >> --- >>   target/riscv/internals.h  |  5 +++++ >>   target/riscv/fpu_helper.c | 42 +++++++++++++++++++++------------------ >>   2 files changed, 28 insertions(+), 19 deletions(-) >> >> diff --git a/target/riscv/internals.h b/target/riscv/internals.h >> index 37d33820ad..9f4ba7d617 100644 >> --- a/target/riscv/internals.h >> +++ b/target/riscv/internals.h >> @@ -38,4 +38,9 @@ target_ulong fclass_d(uint64_t frs1); >>   #define SEW32 2 >>   #define SEW64 3 >>   +static inline uint64_t nanbox_s(float32 f) >> +{ >> +    return f | MAKE_64BIT_MASK(32, 32); >> +} >> + > If define it here,  we can also define a more general  function with flen. > > +static inline uint64_t nanbox_s(float32 f, uint32_t flen) > +{ > +    return f | MAKE_64BIT_MASK(flen, 64 - flen); > +} > + > > So we can reuse it in fp16 or bf16 scalar instruction and in vector instructions. While we could do that, we will not encounter all possible lengths. In the cover letter, I mentioned defining a second function, static inline uint64_t nanbox_h(float16 f) { return f | MAKE_64BIT_MASK(16, 48); } Having two separate functions will, I believe, be easier to use in practice. r~