From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mga09.intel.com (mga09.intel.com [134.134.136.24]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 3C53E28EB for ; Fri, 24 Jun 2022 12:13:37 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1656072817; x=1687608817; h=from:to:cc:subject:date:message-id:in-reply-to: references:mime-version:content-transfer-encoding; bh=UwGnL3cKrVpIYdUCZi0g8IIvLiuF1HHfK1nv3YKvvvI=; b=WitzaqL5ZK6Pbggm+YUdNVI01iBvUWBxf/VitY30SMEKR1sMdk29ex/S vgGRcsvHF+hc/UbW7Uep3XhuOFwQ4opSxNnWjcGcnXjBX5sCFgWvhTA52 pSkPUoNMLf39YVMXMmlW0HE6HnxRU4DsK1e+U49CJKHRgpmvCncjeoDKT mVLgzejUZioOPTvrW7Y8eBy72gQYUq+1TxwtmudLznYdK++2/bln0bL6V gx0QyXaqPFnRHl3piklsCNxFB0UNNCY+Y5OTZTU/LRV513dpfqq+vXM1Z Q+tv7DEtX7K14cZXp28nKwveFh2VcNNV21FF4saHbRmnsBp//qj65/O8b Q==; X-IronPort-AV: E=McAfee;i="6400,9594,10387"; a="281722738" X-IronPort-AV: E=Sophos;i="5.92,218,1650956400"; d="scan'208";a="281722738" Received: from orsmga005.jf.intel.com ([10.7.209.41]) by orsmga102.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 24 Jun 2022 05:13:37 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.92,218,1650956400"; d="scan'208";a="765726377" Received: from irvmail001.ir.intel.com ([10.43.11.63]) by orsmga005.jf.intel.com with ESMTP; 24 Jun 2022 05:13:30 -0700 Received: from newjersey.igk.intel.com (newjersey.igk.intel.com [10.102.20.203]) by irvmail001.ir.intel.com (8.14.3/8.13.6/MailSET/Hub) with ESMTP id 25OCDEo8014999; Fri, 24 Jun 2022 13:13:28 +0100 From: Alexander Lobakin To: Arnd Bergmann , Yury Norov Cc: Alexander Lobakin , Andy Shevchenko , Mark Rutland , Matt Turner , Brian Cain , Geert Uytterhoeven , Yoshinori Sato , Rich Felker , "David S. Miller" , Kees Cook , "Peter Zijlstra (Intel)" , Marco Elver , Borislav Petkov , Tony Luck , Maciej Fijalkowski , Jesse Brandeburg , Greg Kroah-Hartman , Nathan Chancellor , Nick Desaulniers , Tom Rix , kernel test robot , linux-alpha@vger.kernel.org, linux-hexagon@vger.kernel.org, linux-ia64@vger.kernel.org, linux-m68k@lists.linux-m68k.org, linux-sh@vger.kernel.org, sparclinux@vger.kernel.org, linux-arch@vger.kernel.org, llvm@lists.linux.dev, linux-kernel@vger.kernel.org Subject: [PATCH v5 8/9] bitmap: don't assume compiler evaluates small mem*() builtins calls Date: Fri, 24 Jun 2022 14:13:12 +0200 Message-Id: <20220624121313.2382500-9-alexandr.lobakin@intel.com> X-Mailer: git-send-email 2.36.1 In-Reply-To: <20220624121313.2382500-1-alexandr.lobakin@intel.com> References: <20220624121313.2382500-1-alexandr.lobakin@intel.com> Precedence: bulk X-Mailing-List: llvm@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Intel kernel bot triggered the build bug on ARC architecture that in fact is as follows: DECLARE_BITMAP(bitmap, BITS_PER_LONG); bitmap_clear(bitmap, 0, BITS_PER_LONG); BUILD_BUG_ON(!__builtin_constant_p(*bitmap)); which can be expanded to: unsigned long bitmap[1]; memset(bitmap, 0, sizeof(*bitmap)); BUILD_BUG_ON(!__builtin_constant_p(*bitmap)); In most cases, a compiler is able to expand small/simple mem*() calls to simple assignments or bitops, in this case that would mean: unsigned long bitmap[1] = { 0 }; BUILD_BUG_ON(!__builtin_constant_p(*bitmap)); and on most architectures this works, but not on ARC, despite having -O3 for every build. So, to make this work, in case when the last bit to modify is still within the first long (small_const_nbits()), just use plain assignments for the rest of bitmap_*() functions which still use mem*(), but didn't receive such compile-time optimizations yet. This doesn't have the same coverage as compilers provide, but at least something to start: text: add/remove: 3/7 grow/shrink: 43/78 up/down: 1848/-3370 (-1546) data: add/remove: 1/11 grow/shrink: 0/8 up/down: 4/-356 (-352) notably cpumask_*() family when NR_CPUS <= BITS_PER_LONG: netif_get_num_default_rss_queues 38 4 -34 cpumask_copy 90 - -90 cpumask_clear 146 - -146 and the abovementioned assertion started passing. Signed-off-by: Alexander Lobakin --- include/linux/bitmap.h | 22 +++++++++++++++++++--- 1 file changed, 19 insertions(+), 3 deletions(-) diff --git a/include/linux/bitmap.h b/include/linux/bitmap.h index 2e6cd5681040..a0f4f3af8d30 100644 --- a/include/linux/bitmap.h +++ b/include/linux/bitmap.h @@ -238,20 +238,32 @@ extern int bitmap_print_list_to_buf(char *buf, const unsigned long *maskp, static inline void bitmap_zero(unsigned long *dst, unsigned int nbits) { unsigned int len = BITS_TO_LONGS(nbits) * sizeof(unsigned long); - memset(dst, 0, len); + + if (small_const_nbits(nbits)) + *dst = 0; + else + memset(dst, 0, len); } static inline void bitmap_fill(unsigned long *dst, unsigned int nbits) { unsigned int len = BITS_TO_LONGS(nbits) * sizeof(unsigned long); - memset(dst, 0xff, len); + + if (small_const_nbits(nbits)) + *dst = ~0UL; + else + memset(dst, 0xff, len); } static inline void bitmap_copy(unsigned long *dst, const unsigned long *src, unsigned int nbits) { unsigned int len = BITS_TO_LONGS(nbits) * sizeof(unsigned long); - memcpy(dst, src, len); + + if (small_const_nbits(nbits)) + *dst = *src; + else + memcpy(dst, src, len); } /* @@ -431,6 +443,8 @@ static __always_inline void bitmap_set(unsigned long *map, unsigned int start, { if (__builtin_constant_p(nbits) && nbits == 1) __set_bit(start, map); + else if (small_const_nbits(start + nbits)) + *map |= GENMASK(start + nbits - 1, start); else if (__builtin_constant_p(start & BITMAP_MEM_MASK) && IS_ALIGNED(start, BITMAP_MEM_ALIGNMENT) && __builtin_constant_p(nbits & BITMAP_MEM_MASK) && @@ -445,6 +459,8 @@ static __always_inline void bitmap_clear(unsigned long *map, unsigned int start, { if (__builtin_constant_p(nbits) && nbits == 1) __clear_bit(start, map); + else if (small_const_nbits(start + nbits)) + *map &= ~GENMASK(start + nbits - 1, start); else if (__builtin_constant_p(start & BITMAP_MEM_MASK) && IS_ALIGNED(start, BITMAP_MEM_ALIGNMENT) && __builtin_constant_p(nbits & BITMAP_MEM_MASK) && -- 2.36.1