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[174.21.149.226]) by smtp.gmail.com with ESMTPSA id a142sm2686505pfa.6.2020.05.01.09.51.15 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Fri, 01 May 2020 09:51:16 -0700 (PDT) Subject: Re: About hardfloat in ppc To: luoyonggang@gmail.com References: <871ro6ld2f.fsf@linaro.org> <87sggmjgit.fsf@linaro.org> <43ac337c-752a-7151-1e88-de01949571de@linaro.org> <874kszkdhm.fsf@linaro.org> From: Richard Henderson Message-ID: <851c309c-37f2-ea4a-b471-52bddde527c7@linaro.org> Date: Fri, 1 May 2020 09:51:14 -0700 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.7.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 8bit Received-SPF: pass client-ip=2607:f8b0:4864:20::62b; envelope-from=richard.henderson@linaro.org; helo=mail-pl1-x62b.google.com X-detected-operating-system: by eggs.gnu.org: Error: [-] PROGRAM ABORT : Malformed IPv6 address (bad octet value). Location : parse_addr6(), p0f-client.c:67 X-Received-From: 2607:f8b0:4864:20::62b 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: Dino Papararo , "qemu-devel@nongnu.org" , Programmingkid , "qemu-ppc@nongnu.org" , Howard Spoelstra , =?UTF-8?Q?Alex_Benn=c3=a9e?= Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On 5/1/20 9:29 AM, 罗勇刚(Yonggang Luo) wrote: > On Fri, May 1, 2020 at 10:18 PM Richard Henderson Step 1 is to rearrange the fp helpers to eliminate helper_reset_fpstatus(). > I've mentioned this before, that it's possible to leave the steady-state of > env->fp_status.exception_flags == 0, so there's no need for a separate function > call.  I suspect this is worth a decent speedup by itself. > > Hi Richard, what kinds of rearrange the fp need to be done? Can you give me a > more detailed example? I am still not get the idea. See target/openrisc, helper_update_fpcsr. This is like target/ppc helper_float_check_status, in that it is called after the primary fpu helper, after the fpu result is written back to the architectural register, to process fpu exceptions. Note that if get_float_exception_flags returns non-zero, we immediately reset them to zero. Thus the exception flags are only ever non-zero in between the primary fpu operation and the update of the fpscr. Thus, no need for a separate helper_reset_fpstatus. r~