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([156.19.246.23]) by smtp.gmail.com with ESMTPSA id gu26-20020a056a004e5a00b006ed9760b815sm11947413pfb.211.2024.04.24.15.57.19 for (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 24 Apr 2024 15:57:19 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linaro.org; s=google; t=1713999440; x=1714604240; darn=nongnu.org; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:to:from:from:to:cc:subject:date:message-id :reply-to; bh=m6Ty8XllMR28noTCDsk0N/pyr7ynqbZ4X/2NsrzAk7g=; b=EIJF2JfFle4HshL+IB2q0BEng8M3pVv8dlpmDkzESnUYV9Xdw0mHZknY4Wtt28xBgB PMCL1SSlm4zJXxSCvaylY4neRB1pUidZRK0gTdp+O6bd6GGGm3hQlixzdvQMx1VQ27dm 0oTkWnMosRiXacHJVvChmjv4Ydhn44mXgCXDGilCMESKDp8IhNUG5W4UeMuYHz1SY0+I n6ajMcNSlOOfmudFITevwxfh/q2G9Mu4MiTZy6eE9r7KpK+Sfp2kmgt/lj1rz0QnjO/T MSIy6dkvtDfifhfdj13yHeGsraNw6z/hpKuDGryA8NMs+OaBwbKtDH0vvBF0/EPQbJ8q 5i3g== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1713999440; x=1714604240; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:to:from:x-gm-message-state:from:to:cc :subject:date:message-id:reply-to; bh=m6Ty8XllMR28noTCDsk0N/pyr7ynqbZ4X/2NsrzAk7g=; b=jeXPeDvGmytZwrXMjufH3+i5CcQ+b+tin+SUuC4rj9lFkdJiaJQ4WfFhkrP47AH9Lt ELBWQi+FwotJBd66ACHR5nFAzLYPaAj2RkvetcAsi8EZp9QXtIJ9o2tDwF7HLiIIFe6/ 3QwevKKLr3hdAtB/FbVJsRV41ncdSDohLYHUlwbvHOhu5TpMekUJfbcw9j5wrX1LUgwP 3QBrMvfbxVr7BHPYfkk0Pq2jMXySghzIuxcvXPFoiUtN1Hdsmkat6awFWWTPkFtcSgS+ o4cgzxDPT25vPUgjb51rJMKxqWzQqKL1SlIlTZ6U3AjIs56OmUh1+TEzuJ2+tW4jBN9k 7Xgw== X-Gm-Message-State: AOJu0Yz80XXeCasE9nosdeiyeOTaVoEB44PCtXH0tuhiEnQPen8Q607+ JD7CE29AQobkJkrKIbXEdFeLV75IYh99EaJr8rOWBO4bdy0zTnQowAgOfFyei+9brYKsf5TcYHM N X-Google-Smtp-Source: AGHT+IFi3v3haAiVYAcS0Tq2YknEglq790m6wZExwKUTQRhXLSQ3+D27uE22H/jdfOxwFiT6kqpIug== X-Received: by 2002:a05:6a21:3989:b0:1a7:9ed1:fc21 with SMTP id ad9-20020a056a21398900b001a79ed1fc21mr1899489pzc.22.1713999440407; Wed, 24 Apr 2024 15:57:20 -0700 (PDT) From: Richard Henderson To: qemu-devel@nongnu.org Subject: [PATCH v6 06/10] util/bufferiszero: Improve scalar variant Date: Wed, 24 Apr 2024 15:57:01 -0700 Message-Id: <20240424225705.929812-7-richard.henderson@linaro.org> X-Mailer: git-send-email 2.34.1 In-Reply-To: <20240424225705.929812-1-richard.henderson@linaro.org> References: <20240424225705.929812-1-richard.henderson@linaro.org> MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Received-SPF: pass (zohomail.com: domain of gnu.org designates 209.51.188.17 as permitted sender) client-ip=209.51.188.17; envelope-from=qemu-devel-bounces+importer=patchew.org@nongnu.org; helo=lists.gnu.org; Received-SPF: pass client-ip=2607:f8b0:4864:20::535; envelope-from=richard.henderson@linaro.org; helo=mail-pg1-x535.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+importer=patchew.org@nongnu.org Sender: qemu-devel-bounces+importer=patchew.org@nongnu.org X-ZohoMail-DKIM: pass (identity @linaro.org) X-ZM-MESSAGEID: 1713999535387100003 Content-Type: text/plain; charset="utf-8" Split less-than and greater-than 256 cases. Use unaligned accesses for head and tail. Avoid using out-of-bounds pointers in loop boundary conditions. Signed-off-by: Richard Henderson Reviewed-by: Philippe Mathieu-Daud=C3=A9 --- util/bufferiszero.c | 85 +++++++++++++++++++++++++++------------------ 1 file changed, 51 insertions(+), 34 deletions(-) diff --git a/util/bufferiszero.c b/util/bufferiszero.c index 02df82b4ff..c9a7ded016 100644 --- a/util/bufferiszero.c +++ b/util/bufferiszero.c @@ -28,40 +28,57 @@ =20 static bool (*buffer_is_zero_accel)(const void *, size_t); =20 -static bool buffer_is_zero_integer(const void *buf, size_t len) +static bool buffer_is_zero_int_lt256(const void *buf, size_t len) { - if (unlikely(len < 8)) { - /* For a very small buffer, simply accumulate all the bytes. */ - const unsigned char *p =3D buf; - const unsigned char *e =3D buf + len; - unsigned char t =3D 0; + uint64_t t; + const uint64_t *p, *e; =20 - do { - t |=3D *p++; - } while (p < e); - - return t =3D=3D 0; - } else { - /* Otherwise, use the unaligned memory access functions to - handle the beginning and end of the buffer, with a couple - of loops handling the middle aligned section. */ - uint64_t t =3D ldq_he_p(buf); - const uint64_t *p =3D (uint64_t *)(((uintptr_t)buf + 8) & -8); - const uint64_t *e =3D (uint64_t *)(((uintptr_t)buf + len) & -8); - - for (; p + 8 <=3D e; p +=3D 8) { - if (t) { - return false; - } - t =3D p[0] | p[1] | p[2] | p[3] | p[4] | p[5] | p[6] | p[7]; - } - while (p < e) { - t |=3D *p++; - } - t |=3D ldq_he_p(buf + len - 8); - - return t =3D=3D 0; + /* + * Use unaligned memory access functions to handle + * the beginning and end of the buffer. + */ + if (unlikely(len <=3D 8)) { + return (ldl_he_p(buf) | ldl_he_p(buf + len - 4)) =3D=3D 0; } + + t =3D ldq_he_p(buf) | ldq_he_p(buf + len - 8); + p =3D QEMU_ALIGN_PTR_DOWN(buf + 8, 8); + e =3D QEMU_ALIGN_PTR_DOWN(buf + len - 1, 8); + + /* Read 0 to 31 aligned words from the middle. */ + while (p < e) { + t |=3D *p++; + } + return t =3D=3D 0; +} + +static bool buffer_is_zero_int_ge256(const void *buf, size_t len) +{ + /* + * Use unaligned memory access functions to handle + * the beginning and end of the buffer. + */ + uint64_t t =3D ldq_he_p(buf) | ldq_he_p(buf + len - 8); + const uint64_t *p =3D QEMU_ALIGN_PTR_DOWN(buf + 8, 8); + const uint64_t *e =3D QEMU_ALIGN_PTR_DOWN(buf + len - 1, 8); + + /* Collect a partial block at the tail end. */ + t |=3D e[-7] | e[-6] | e[-5] | e[-4] | e[-3] | e[-2] | e[-1]; + + /* + * Loop over 64 byte blocks. + * With the head and tail removed, e - p >=3D 30, + * so the loop must iterate at least 3 times. + */ + do { + if (t) { + return false; + } + t =3D p[0] | p[1] | p[2] | p[3] | p[4] | p[5] | p[6] | p[7]; + p +=3D 8; + } while (p < e - 7); + + return t =3D=3D 0; } =20 #if defined(CONFIG_AVX2_OPT) || defined(__SSE2__) @@ -173,7 +190,7 @@ select_accel_cpuinfo(unsigned info) { CPUINFO_AVX2, buffer_zero_avx2 }, #endif { CPUINFO_SSE2, buffer_zero_sse2 }, - { CPUINFO_ALWAYS, buffer_is_zero_integer }, + { CPUINFO_ALWAYS, buffer_is_zero_int_ge256 }, }; =20 for (unsigned i =3D 0; i < ARRAY_SIZE(all); ++i) { @@ -211,7 +228,7 @@ bool test_buffer_is_zero_next_accel(void) return false; } =20 -#define INIT_ACCEL buffer_is_zero_integer +#define INIT_ACCEL buffer_is_zero_int_ge256 #endif =20 static bool (*buffer_is_zero_accel)(const void *, size_t) =3D INIT_ACCEL; @@ -232,7 +249,7 @@ bool buffer_is_zero_ool(const void *buf, size_t len) if (likely(len >=3D 256)) { return buffer_is_zero_accel(buf, len); } - return buffer_is_zero_integer(buf, len); + return buffer_is_zero_int_lt256(buf, len); } =20 bool buffer_is_zero_ge256(const void *buf, size_t len) --=20 2.34.1