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From: Richard Henderson To: Chinmay Rath , qemu-ppc@nongnu.org Cc: qemu-devel@nongnu.org, npiggin@gmail.com, danielhb413@gmail.com, harshpb@linux.ibm.com References: <20240621114604.868415-1-rathc@linux.ibm.com> <20240621114604.868415-3-rathc@linux.ibm.com> Content-Language: en-US In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit Received-SPF: pass client-ip=2607:f8b0:4864:20::531; envelope-from=richard.henderson@linaro.org; helo=mail-pg1-x531.google.com 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=unavailable autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org On 6/21/24 09:34, Richard Henderson wrote: > On 6/21/24 04:46, Chinmay Rath wrote: >> +    tcg_gen_qemu_ld_i128(avr, EA, ctx->mem_idx, DEF_MEMOP(MO_128)); >> +    set_avr_full(a->rt, avr); > > This needs to specify atomicity as well.  This is much more important to for 16 byte > operations than smaller accesses, as this might require stop-the-world semantics depending > on the host. > > According to section 1.4 Storage Atomicity, we need no more than 8-byte atomicity for > these vector operations, and then the following the alignment bits down. > > So: MO_128 | MO_ATOM_IFALIGN_PAIR, Actually, you need MO_ATOM_SUBALIGN semantics, maxing out at MO_64, which hasn't been implemented. But since none of the rest of target/ppc has been updated to use SUBALIGN, using IFALIGN is not a regression. r~