From patchwork Sun Mar 21 21:54:54 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Yury Norov X-Patchwork-Id: 12153363 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-15.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_GIT autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id C76A0C4345E for ; Sun, 21 Mar 2021 21:56:11 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id A7ED06194E for ; Sun, 21 Mar 2021 21:56:11 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231394AbhCUVzl (ORCPT ); Sun, 21 Mar 2021 17:55:41 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:60552 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231440AbhCUVzK (ORCPT ); Sun, 21 Mar 2021 17:55:10 -0400 Received: from mail-qk1-x734.google.com (mail-qk1-x734.google.com [IPv6:2607:f8b0:4864:20::734]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id A66C8C061762; Sun, 21 Mar 2021 14:55:09 -0700 (PDT) Received: by mail-qk1-x734.google.com with SMTP id g20so8737401qkk.1; Sun, 21 Mar 2021 14:55:09 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=from:to:cc:subject:date:message-id:in-reply-to:references :mime-version:content-transfer-encoding; bh=N+ZJiIhOello7KIiJWn70PNFcjQDb7YzgmEeWxqS6i8=; b=tVBJcQ2Z1OeiE7yZJp00R0GWuGmbRMch1UIymsy+1icV5ZZl89V39I6APSsX5RC+du OidD6OAzApuYX0qRD8WDRahmthtEODOJprSx08RQiO/8rrxoBscsKiXt0re9LyIvwyGj UtQTsHJsb9CDgacCnK1DY2425TmkMPYuRlV4KT4R8XN25ezl1CqMoSFhah8YKQmSLt7W EcV5NxQTJj0qtvwR4Bo20BWEYha4lsHBvutrwYG5ABwq4FAR/9kjEROkIcHS7CPU6FI9 sR1VKee0hWx+JAOz72ZJnU8ex7PBNptS0K5UK6hIJ4yXVWUvP6z86I2uXrQ6HciYKI9Q HRaA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:from:to:cc:subject:date:message-id:in-reply-to :references:mime-version:content-transfer-encoding; bh=N+ZJiIhOello7KIiJWn70PNFcjQDb7YzgmEeWxqS6i8=; b=MWkDbKn3i0/rEoBTzFMS1F/1afCWykE/Q3TjnNx1Zwite3Rp3G4O03TRY5tfpTClEi +CbkEvdpDadbrmrmt12eeDe1htAeyNNCUbREW00XXoPD8K1zxX4QDzFA010U57eVVX4/ sBjiWr07RijhkRKsIWOk5ofDJUQmlk+MSALm6+Dm6Aa6AaOHMqFDWHeHR+g4lUgxkaNv jRlZcQ/NkfYQVkUaLsHYUsjgHg4P1o4HsvRpCrz/P7TCXsgNVxjbhmfiL0iP0/ZqS+SZ iWrlby5eCkMaqgwCPCFrisf5UMEHaxDCkuivsMAUWBOPjwXwbqA8eaZFhyEyW7lqYP3m D0Dw== X-Gm-Message-State: AOAM531Y6mv9VcGKUcY9kShi2trrNTui+ISNfApUFpC+hkC2xquVjG2w 9utMeB9mZvvmJOYfk3Sm9QB5YlWJjVY= X-Google-Smtp-Source: ABdhPJzXJ/pBLcWQlCs9aYDoSEsrnNjRo+VU6WS1hwmYPn8C+33iM9tNZaO5kKLEbj9grKrbK3kImw== X-Received: by 2002:a05:620a:118f:: with SMTP id b15mr3068805qkk.5.1616363708628; Sun, 21 Mar 2021 14:55:08 -0700 (PDT) Received: from localhost ([76.73.146.210]) by smtp.gmail.com with ESMTPSA id y13sm7718612qto.39.2021.03.21.14.55.08 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sun, 21 Mar 2021 14:55:08 -0700 (PDT) From: Yury Norov To: linux-kernel@vger.kernel.org Cc: Yury Norov , linux-m68k@lists.linux-m68k.org, linux-arch@vger.kernel.org, linux-sh@vger.kernel.org, Alexey Klimov , Andrew Morton , Andy Shevchenko , Arnd Bergmann , David Sterba , Dennis Zhou , Geert Uytterhoeven , Jianpeng Ma , Joe Perches , John Paul Adrian Glaubitz , Josh Poimboeuf , Rasmus Villemoes , Rich Felker , Stefano Brivio , Wei Yang , Wolfram Sang , Yoshinori Sato Subject: [PATCH 09/12] lib: add fast path for find_next_*_bit() Date: Sun, 21 Mar 2021 14:54:54 -0700 Message-Id: <20210321215457.588554-10-yury.norov@gmail.com> X-Mailer: git-send-email 2.25.1 In-Reply-To: <20210321215457.588554-1-yury.norov@gmail.com> References: <20210321215457.588554-1-yury.norov@gmail.com> MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: linux-sh@vger.kernel.org Similarly to bitmap functions, find_next_*_bit() users will benefit if we'll handle a case of bitmaps that fit into a single word inline. In the very best case, the compiler may replace a function call with a few instructions. This is the quite typical find_next_bit() user: unsigned int cpumask_next(int n, const struct cpumask *srcp) { /* -1 is a legal arg here. */ if (n != -1) cpumask_check(n); return find_next_bit(cpumask_bits(srcp), nr_cpumask_bits, n + 1); } EXPORT_SYMBOL(cpumask_next); Currently, on ARM64 the generated code looks like this: 0000000000000000 : 0: a9bf7bfd stp x29, x30, [sp, #-16]! 4: 11000402 add w2, w0, #0x1 8: aa0103e0 mov x0, x1 c: d2800401 mov x1, #0x40 // #64 10: 910003fd mov x29, sp 14: 93407c42 sxtw x2, w2 18: 94000000 bl 0 1c: a8c17bfd ldp x29, x30, [sp], #16 20: d65f03c0 ret 24: d503201f nop After applying this patch: 0000000000000140 : 140: 11000400 add w0, w0, #0x1 144: 93407c00 sxtw x0, w0 148: f100fc1f cmp x0, #0x3f 14c: 54000168 b.hi 178 // b.pmore 150: f9400023 ldr x3, [x1] 154: 92800001 mov x1, #0xffffffffffffffff // #-1 158: 9ac02020 lsl x0, x1, x0 15c: 52800802 mov w2, #0x40 // #64 160: 8a030001 and x1, x0, x3 164: dac00020 rbit x0, x1 168: f100003f cmp x1, #0x0 16c: dac01000 clz x0, x0 170: 1a800040 csel w0, w2, w0, eq // eq = none 174: d65f03c0 ret 178: 52800800 mov w0, #0x40 // #64 17c: d65f03c0 ret find_next_bit() call is replaced with 6 instructions. find_next_bit() itself is 41 instructions plus function call overhead. Despite inlining, the scripts/bloat-o-meter report smaller .text size after applying the series: add/remove: 11/9 grow/shrink: 233/176 up/down: 5780/-6768 (-988) Signed-off-by: Yury Norov --- include/asm-generic/bitops/find.h | 30 ++++++++++++++++++++++++++++++ include/asm-generic/bitops/le.h | 21 +++++++++++++++++++++ 2 files changed, 51 insertions(+) diff --git a/include/asm-generic/bitops/find.h b/include/asm-generic/bitops/find.h index 7ad70dab8e93..4148c74a1e4d 100644 --- a/include/asm-generic/bitops/find.h +++ b/include/asm-generic/bitops/find.h @@ -20,6 +20,16 @@ static inline unsigned long find_next_bit(const unsigned long *addr, unsigned long size, unsigned long offset) { + if (small_const_nbits(size)) { + unsigned long val; + + if (unlikely(offset >= size)) + return size; + + val = *addr & GENMASK(size - 1, offset); + return val ? __ffs(val) : size; + } + return _find_next_bit(addr, NULL, size, offset, 0UL, 0); } #endif @@ -40,6 +50,16 @@ unsigned long find_next_and_bit(const unsigned long *addr1, const unsigned long *addr2, unsigned long size, unsigned long offset) { + if (small_const_nbits(size)) { + unsigned long val; + + if (unlikely(offset >= size)) + return size; + + val = *addr1 & *addr2 & GENMASK(size - 1, offset); + return val ? __ffs(val) : size; + } + return _find_next_bit(addr1, addr2, size, offset, 0UL, 0); } #endif @@ -58,6 +78,16 @@ static inline unsigned long find_next_zero_bit(const unsigned long *addr, unsigned long size, unsigned long offset) { + if (small_const_nbits(size)) { + unsigned long val; + + if (unlikely(offset >= size)) + return size; + + val = *addr | ~GENMASK(size - 1, offset); + return val == ~0UL ? size : ffz(val); + } + return _find_next_bit(addr, NULL, size, offset, ~0UL, 0); } #endif diff --git a/include/asm-generic/bitops/le.h b/include/asm-generic/bitops/le.h index 21305f6cea0b..5a28629cbf4d 100644 --- a/include/asm-generic/bitops/le.h +++ b/include/asm-generic/bitops/le.h @@ -5,6 +5,7 @@ #include #include #include +#include #if defined(__LITTLE_ENDIAN) @@ -37,6 +38,16 @@ static inline unsigned long find_next_zero_bit_le(const void *addr, unsigned long size, unsigned long offset) { + if (small_const_nbits(size)) { + unsigned long val = *(const unsigned long *)addr; + + if (unlikely(offset >= size)) + return size; + + val = swab(val) | ~GENMASK(size - 1, offset); + return val == ~0UL ? size : ffz(val); + } + return _find_next_bit(addr, NULL, size, offset, ~0UL, 1); } #endif @@ -46,6 +57,16 @@ static inline unsigned long find_next_bit_le(const void *addr, unsigned long size, unsigned long offset) { + if (small_const_nbits(size)) { + unsigned long val = *(const unsigned long *)addr; + + if (unlikely(offset >= size)) + return size; + + val = swab(val) & GENMASK(size - 1, offset); + return val ? __ffs(val) : size; + } + return _find_next_bit(addr, NULL, size, offset, 0UL, 1); } #endif