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[97.113.7.119]) by smtp.gmail.com with ESMTPSA id a16sm477679pfk.5.2019.08.27.17.07.14 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Tue, 27 Aug 2019 17:07:15 -0700 (PDT) To: Peter Maydell References: <20190819213755.26175-1-richard.henderson@linaro.org> <20190819213755.26175-67-richard.henderson@linaro.org> From: Richard Henderson Openpgp: preference=signencrypt Message-ID: <7f4eac6e-486a-3d99-b533-5fd4ac41864d@linaro.org> Date: Tue, 27 Aug 2019 17:07:13 -0700 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.8.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit X-detected-operating-system: by eggs.gnu.org: Genre and OS details not recognized. X-Received-From: 2607:f8b0:4864:20::442 Subject: Re: [Qemu-devel] [PATCH v2 66/68] target/arm: Convert T16, long branches 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: qemu-arm , QEMU Developers Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On 8/27/19 2:34 AM, Peter Maydell wrote: >> + tcg_gen_andi_i32(tmp, tmp, -4); > > Minor nit, but can we use 0xfffffffc like the old code did, > to avoid the reader having to do 2s-complement arithmetic > in their head to figure out that we're clearing the low 2 bits? I always preferred "x & -c" for exactly the same reason: to avoid the reader having to do 2s compliment arithmetic in their head to figure out that we're aligning to c. But, sure, if you like. > This would be a good place to put a comment equivalent to that > in the old decoder: > > # thumb_insn_is_16bit() ensures we won't be decoding these as > # T16 instructions for a Thumb2 CPU, so these patterns must be > # a Thumb1 split BL/BLX. > >> +BLX_suffix 11101 imm:11 &i >> +BL_BLX_prefix 11110 imm:s11 &i >> +BL_suffix 11111 imm:11 &i I had placed that with trans_BL_BLX_prefix, but I suppose this is a better place. r~