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[97.90.106.114]) by smtp.gmail.com with ESMTPSA id k100sm312141pjb.57.2020.07.06.13.48.06 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 06 Jul 2020 13:48:07 -0700 (PDT) Subject: Re: [PULL v2 12/64] target/riscv: add vector amo operations To: Alistair Francis References: <20200702162354.928528-1-alistair.francis@wdc.com> <20200702162354.928528-13-alistair.francis@wdc.com> From: Richard Henderson Message-ID: Date: Mon, 6 Jul 2020 13:48:05 -0700 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.8.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Received-SPF: pass client-ip=2607:f8b0:4864:20::542; envelope-from=richard.henderson@linaro.org; helo=mail-pg1-x542.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=_AUTOLEARN 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: Peter Maydell , LIU Zhiwei , QEMU Developers , Alistair Francis Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On 7/5/20 11:20 AM, Peter Maydell wrote: > On Thu, 2 Jul 2020 at 17:33, Alistair Francis wrote: >> >> From: LIU Zhiwei >> >> Vector AMOs operate as if aq and rl bits were zero on each element >> with regard to ordering relative to other instructions in the same hart. >> Vector AMOs provide no ordering guarantee between element operations >> in the same vector AMO instruction > > Hi; Coverity thinks (probably wrongly) that there might be an array > overflow here: > >> +static bool amo_op(DisasContext *s, arg_rwdvm *a, uint8_t seq) >> +{ >> + uint32_t data = 0; >> + gen_helper_amo *fn; >> + static gen_helper_amo *const fnsw[9] = { > > This is a 9-element array... > >> + /* no atomic operation */ >> + gen_helper_vamoswapw_v_w, >> + gen_helper_vamoaddw_v_w, >> + gen_helper_vamoxorw_v_w, >> + gen_helper_vamoandw_v_w, >> + gen_helper_vamoorw_v_w, >> + gen_helper_vamominw_v_w, >> + gen_helper_vamomaxw_v_w, >> + gen_helper_vamominuw_v_w, >> + gen_helper_vamomaxuw_v_w >> + }; > >> + if (tb_cflags(s->base.tb) & CF_PARALLEL) { >> + gen_helper_exit_atomic(cpu_env); >> + s->base.is_jmp = DISAS_NORETURN; >> + return true; >> + } else { >> + if (s->sew == 3) { >> +#ifdef TARGET_RISCV64 >> + fn = fnsd[seq]; >> +#else >> + /* Check done in amo_check(). */ >> + g_assert_not_reached(); >> +#endif >> + } else { >> + fn = fnsw[seq]; > > ...which we here index via 'seq'... > > >> +#ifdef TARGET_RISCV64 >> +GEN_VEXT_TRANS(vamoswapd_v, 9, rwdvm, amo_op, amo_check) >> +GEN_VEXT_TRANS(vamoaddd_v, 10, rwdvm, amo_op, amo_check) >> +GEN_VEXT_TRANS(vamoxord_v, 11, rwdvm, amo_op, amo_check) >> +GEN_VEXT_TRANS(vamoandd_v, 12, rwdvm, amo_op, amo_check) >> +GEN_VEXT_TRANS(vamoord_v, 13, rwdvm, amo_op, amo_check) >> +GEN_VEXT_TRANS(vamomind_v, 14, rwdvm, amo_op, amo_check) >> +GEN_VEXT_TRANS(vamomaxd_v, 15, rwdvm, amo_op, amo_check) >> +GEN_VEXT_TRANS(vamominud_v, 16, rwdvm, amo_op, amo_check) >> +GEN_VEXT_TRANS(vamomaxud_v, 17, rwdvm, amo_op, amo_check) >> +#endif > > ...which in the calls that these macros expand out to can > be 9 or greater. FWIW, I think it would be better to have the gen_helper_amo *fn symbol here in the macro than a magic "seq" number. r~