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Mon, 3 Feb 2025 09:42:55 +0100 (CET) From: Andreas Schwab To: Jessica Clarke Cc: Alexandre Ghiti , linux-riscv@lists.infradead.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] riscv/atomic: Do proper sign extension also for unsigned in arch_cmpxchg In-Reply-To: (Jessica Clarke's message of "Thu, 30 Jan 2025 17:21:28 +0000") References: Date: Mon, 03 Feb 2025 09:42:55 +0100 Message-ID: User-Agent: Gnus/5.13 (Gnus v5.13) Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain X-Spam-Level: ** X-Spamd-Result: default: False [2.70 / 50.00]; BAYES_HAM(-3.00)[99.99%]; HFILTER_HOSTNAME_UNKNOWN(2.50)[]; RDNS_NONE(2.00)[]; ONCE_RECEIVED(1.20)[]; HFILTER_HELO_IP_A(1.00)[hawking.nue2.suse.org]; NEURAL_HAM_LONG(-1.00)[-1.000]; HFILTER_HELO_NORES_A_OR_MX(0.30)[hawking.nue2.suse.org]; R_DKIM_ALLOW(-0.20)[suse.de:s=susede2_rsa,suse.de:s=susede2_ed25519]; RCVD_NO_TLS_LAST(0.10)[]; MIME_GOOD(-0.10)[text/plain]; NEURAL_HAM_SHORT(-0.09)[-0.440]; MX_GOOD(-0.01)[]; DKIM_SIGNED(0.00)[suse.de:s=susede2_rsa,suse.de:s=susede2_ed25519]; FUZZY_BLOCKED(0.00)[rspamd.com]; MIME_TRACE(0.00)[0:+]; ARC_NA(0.00)[]; DIRECT_TO_MX(0.00)[Gnus/5.13 (Gnus v5.13)]; DKIM_TRACE(0.00)[suse.de:+]; TO_DN_SOME(0.00)[]; FROM_EQ_ENVFROM(0.00)[]; FROM_HAS_DN(0.00)[]; TO_MATCH_ENVRCPT_ALL(0.00)[]; MID_RHS_MATCH_FROM(0.00)[]; RCPT_COUNT_THREE(0.00)[4]; RCVD_COUNT_ONE(0.00)[1]; DBL_BLOCKED_OPENRESOLVER(0.00)[suse.de:email,suse.de:dkim,suse.de:mid] X-Spam-Score: 2.70 X-Spamd-Bar: ++ X-Rspamd-Queue-Id: 4266E1F37C X-Rspamd-Action: no action X-Rspamd-Server: rspamd2.dmz-prg2.suse.org X-Spam-Flag: NO On Jan 30 2025, Jessica Clarke wrote: > On 30 Jan 2025, at 15:53, Andreas Schwab wrote: >> >> On Jan 30 2025, Alexandre Ghiti wrote: >> >>> a2 is used as it is passed by the calling function, so we can't be sure a2 >>> is sign extended to me, what am I missing? >> >> 32-bit scalar arguments are guaranteed to be sign extended on entry. > > Firstly, the calling convention is irrelevant if the function is > inlined, which this almost always will be. This is only about the non-inlined variant. -- Andreas Schwab, SUSE Labs, schwab@suse.de GPG Key fingerprint = 0196 BAD8 1CE9 1970 F4BE 1748 E4D4 88E3 0EEA B9D7 "And now for something completely different."