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Tue, 17 Oct 2023 06:52:52 -0700 (PDT) Message-ID: <8c85fc54-3933-4330-a378-c1b444b0771f@linaro.org> Date: Tue, 17 Oct 2023 06:52:50 -0700 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [RFC PATCH] target/m68k: Use i128 for 128-bit load/store in m68k_copy_line() Content-Language: en-US To: =?UTF-8?Q?Philippe_Mathieu-Daud=C3=A9?= , qemu-devel@nongnu.org Cc: Laurent Vivier References: <20231017122702.39311-1-philmd@linaro.org> From: Richard Henderson In-Reply-To: <20231017122702.39311-1-philmd@linaro.org> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit Received-SPF: pass client-ip=2607:f8b0:4864:20::533; envelope-from=richard.henderson@linaro.org; helo=mail-pg1-x533.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=ham 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 10/17/23 05:27, Philippe Mathieu-Daudé wrote: > Signed-off-by: Philippe Mathieu-Daudé > --- > Based-on: <20231013175109.124308-1-richard.henderson@linaro.org> > tcg: Add tcg_gen_{ld,st}_i128 > > RFC because unsure and untested... > --- > target/m68k/translate.c | 14 ++++---------- > 1 file changed, 4 insertions(+), 10 deletions(-) > > diff --git a/target/m68k/translate.c b/target/m68k/translate.c > index 4d0110de95..1e3d155bd9 100644 > --- a/target/m68k/translate.c > +++ b/target/m68k/translate.c > @@ -4293,23 +4293,17 @@ DISAS_INSN(chk2) > > static void m68k_copy_line(TCGv dst, TCGv src, int index) > { > + MemOp mop = MO_128 | MO_TE; > + TCGv_i128 t = tcg_temp_new_i128(); > TCGv addr; > - TCGv_i64 t0, t1; > > addr = tcg_temp_new(); > > - t0 = tcg_temp_new_i64(); > - t1 = tcg_temp_new_i64(); > - > tcg_gen_andi_i32(addr, src, ~15); > - tcg_gen_qemu_ld_i64(t0, addr, index, MO_TEUQ); > - tcg_gen_addi_i32(addr, addr, 8); > - tcg_gen_qemu_ld_i64(t1, addr, index, MO_TEUQ); > + tcg_gen_qemu_ld_i128(t, addr, index, mop); > > tcg_gen_andi_i32(addr, dst, ~15); > - tcg_gen_qemu_st_i64(t0, addr, index, MO_TEUQ); > - tcg_gen_addi_i32(addr, addr, 8); > - tcg_gen_qemu_st_i64(t1, addr, index, MO_TEUQ); > + tcg_gen_st_i128(t, addr, index); Aside from the typo, the other thing you need to consider when introducing 16-byte operations is the atomicity. Do you want or need this to be atomic? For m68k, I strongly suspect that we don't need the entire read or write to be atomic. The manual says "burst reads and writes" without defining those terms. I suspect that MO_ATOM_NONE is sufficient, but MO_ATOM_IFALIGN_PAIR would preserve the atomicity of the current code. r~