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[88.187.86.199]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-4391da9652bsm144654865e9.2.2025.02.10.02.29.15 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 10 Feb 2025 02:29:15 -0800 (PST) Message-ID: <4b4dacd6-f61c-44d9-9764-d111413e42d0@linaro.org> Date: Mon, 10 Feb 2025 11:29:14 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PULL 7/9] tcg/optimize: optimize TSTNE using smask and zmask To: Paolo Bonzini , qemu-devel@nongnu.org References: <20250210102255.2555097-1-pbonzini@redhat.com> <20250210102255.2555097-8-pbonzini@redhat.com> Content-Language: en-US From: =?UTF-8?Q?Philippe_Mathieu-Daud=C3=A9?= In-Reply-To: <20250210102255.2555097-8-pbonzini@redhat.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Received-SPF: pass client-ip=2a00:1450:4864:20::32a; envelope-from=philmd@linaro.org; helo=mail-wm1-x32a.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 10/2/25 11:22, Paolo Bonzini wrote: > Generalize the existing optimization of "TSTNE x,sign" and "TSTNE x,-1". > This can be useful for example in the i386 frontend, which will generate > tests of zero-extended registers against 0xffffffff. > > Ironically, on x86 hosts this is a very slight pessimization in the very > case it's meant to optimize because > > brcond_i64 cc_dst,$0xffffffff,tsteq,$L1 > > (test %ebx, %ebx) is 1 byte smaller than > > brcond_i64 cc_dst,$0x0,eq,$L1 > > (test %rbx, %rbx). However, in general it is an improvement, especially > if it avoids placing a large immediate in the constant pool. > > Signed-off-by: Paolo Bonzini > --- > tcg/optimize.c | 13 ++++++++----- > 1 file changed, 8 insertions(+), 5 deletions(-) Reviewed-by: Richard Henderson https://lore.kernel.org/qemu-devel/484b6063-e21f-48d6-9121-6c0c64396889@linaro.org/