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([2001:8a0:f93a:3b00:e038:5cdc:b8bf:4653]) by smtp.gmail.com with ESMTPSA id l22-20020a05600c089600b003c43dc42b4dsm7517255wmp.16.2022.10.10.07.56.41 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 10 Oct 2022 07:56:41 -0700 (PDT) Subject: Re: [PATCH] [Arm] Remove dead FPA code To: Luis Machado , gdb-patches@sourceware.org References: <20220920123012.189293-1-luis.machado@arm.com> From: Pedro Alves Message-ID: <8b615b88-26d8-a480-ad9f-51be749169cb@palves.net> Date: Mon, 10 Oct 2022 15:56:40 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.10.1 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 8bit X-Spam-Status: No, score=-3.6 required=5.0 tests=BAYES_00, BODY_8BITS, FREEMAIL_FORGED_FROMDOMAIN, FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS, KAM_DMARC_STATUS, NICE_REPLY_A, RCVD_IN_DNSWL_NONE, RCVD_IN_MSPIKE_H2, SPF_HELO_NONE, SPF_PASS, TXREP autolearn=ham autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on server2.sourceware.org X-BeenThere: gdb-patches@sourceware.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Gdb-patches mailing list List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Mon, 10 Oct 2022 14:56:46 -0000 Hi, On 2022-10-04 9:43 a.m., Luis Machado wrote: > > >>> -   The packet format which >>> -   includes FPA registers should be considered deprecated for >>> -   M-profile targets.  */ >>> - >>> -static void >>> -arm_register_g_packet_guesses (struct gdbarch *gdbarch) >>> -{ >>> -  arm_gdbarch_tdep *tdep = gdbarch_tdep (gdbarch); >>> - >>> -  if (tdep->is_m) >>> -    { >>> -      const target_desc *tdesc; >>> - >>> -      /* If we know from the executable this is an M-profile target, >>> -     cater for remote targets whose register set layout is the >>> -     same as the FPA layout.  */ >>> -      tdesc = arm_read_mprofile_description (ARM_M_TYPE_WITH_FPA); >>> -      register_remote_g_packet_guess (gdbarch, >>> -                      ARM_CORE_REGS_SIZE + ARM_FP_REGS_SIZE, >>> -                      tdesc); >>> - >>> -      /* The regular M-profile layout.  */ >>> -      tdesc = arm_read_mprofile_description (ARM_M_TYPE_M_PROFILE); >>> -      register_remote_g_packet_guess (gdbarch, ARM_CORE_REGS_SIZE, >>> -                      tdesc); >>> - >>> -      /* M-profile plus M4F VFP.  */ >>> -      tdesc = arm_read_mprofile_description (ARM_M_TYPE_VFP_D16); >>> -      register_remote_g_packet_guess (gdbarch, >>> -                      ARM_CORE_REGS_SIZE + ARM_VFP2_REGS_SIZE, >>> -                      tdesc); >>> -      /* M-profile plus MVE.  */ >>> -      tdesc = arm_read_mprofile_description (ARM_M_TYPE_MVE); >>> -      register_remote_g_packet_guess (gdbarch, ARM_CORE_REGS_SIZE >>> -                      + ARM_VFP2_REGS_SIZE >>> -                      + ARM_INT_REGISTER_SIZE, tdesc); >>> - >>> -      /* M-profile system (stack pointers).  */ >>> -      tdesc = arm_read_mprofile_description (ARM_M_TYPE_SYSTEM); >>> -      register_remote_g_packet_guess (gdbarch, 2 * ARM_INT_REGISTER_SIZE, tdesc); >> >> And what about all these other non-FPA guesses?  Do you really mean to drop them? >> > > More recently we've added two new guesses for MVE and M-profile system registers, but it doesn't > make sense to do so, as these features are advertised as XML already. What was the justification for adding them back then, then? > So in my opinion, we should > drop the g packet guesses completely and rely solely on XML descriptions. Then I think that it should be proposed in a separate patch, as it has nothing to do with dropping FPA support. Off hand, I don't really see what you win much removing the guesses. The code that it allows removing isn't something that would block any redesign or big cleanup in gdb, as gdb needs to know how to create built-in tdescs for core files, anyhow (even if not these particular tdescs), and the tdesc generation code is even shared with gdbserver.