From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mailscanner01.zoner.fi (mailscanner01.zoner.fi [84.34.166.10]) (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 4FB0785282 for ; Wed, 20 Mar 2024 18:47:46 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=84.34.166.10 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1710960470; cv=none; b=eQ+UR/b+pEx396LgvvfrCPH8VBLrxpkOSan5UOhyfYKLgXSJwYlUHNfWdOERU0SEayJ7sGknd6Mn/7NYhXRptbwczYpfU+tfCcmucqHek4e10+kzMSo/tc8hyUKETBXLATC+nAxG1e8TPcBtr6YJsbpmmwoXiU9m3Kbx/16iRWU= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1710960470; c=relaxed/simple; bh=wEjY393WFSzEeWiwjkl/GFZDH84R1QcgM4sHjnLfaQY=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=caZm1KAOF35LbhftrX+mXNtGpNMAjz6IPw5HpqiYSNMuWKp+LtdWC6/WyngW4XY+TAutoM8zzsg+O350J+/lzlCEtypule4EJbeVZ/Gqetb3IJs2oT/YCF+c5UlJOPqn+uFN7CBIrBunQsC5Mb1CNWDKjimkmaqAqlnOsTmXTA4= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=tukaani.org; spf=pass smtp.mailfrom=tukaani.org; arc=none smtp.client-ip=84.34.166.10 Authentication-Results: smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=tukaani.org Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=tukaani.org Received: from www25.zoner.fi (www25.zoner.fi [84.34.147.45]) by mailscanner01.zoner.fi (Postfix) with ESMTPS id B7686402D4; Wed, 20 Mar 2024 20:39:26 +0200 (EET) Received: from mail.zoner.fi ([84.34.147.244]) by www25.zoner.fi with esmtp (Exim 4.96.1-7-g79877b70e) (envelope-from ) id 1rn0qU-0001dW-1Z; Wed, 20 Mar 2024 20:39:26 +0200 From: Lasse Collin To: Andrew Morton Cc: Lasse Collin , Jia Tan , linux-kernel@vger.kernel.org Subject: [PATCH 07/11] xz: Optimize for-loop conditions in the BCJ decoders Date: Wed, 20 Mar 2024 20:38:40 +0200 Message-ID: <20240320183846.19475-8-lasse.collin@tukaani.org> X-Mailer: git-send-email 2.44.0 In-Reply-To: <20240320183846.19475-1-lasse.collin@tukaani.org> References: <20240320183846.19475-1-lasse.collin@tukaani.org> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Compilers cannot optimize the addition "i + 4" away since theoretically it could overflow. Reviewed-by: Jia Tan Signed-off-by: Lasse Collin --- lib/xz/xz_dec_bcj.c | 23 ++++++++++++++++++----- 1 file changed, 18 insertions(+), 5 deletions(-) diff --git a/lib/xz/xz_dec_bcj.c b/lib/xz/xz_dec_bcj.c index ab9237ed6db8..e0b4bf4999c0 100644 --- a/lib/xz/xz_dec_bcj.c +++ b/lib/xz/xz_dec_bcj.c @@ -161,7 +161,9 @@ static size_t bcj_powerpc(struct xz_dec_bcj *s, uint8_t *buf, size_t size) size_t i; uint32_t instr; - for (i = 0; i + 4 <= size; i += 4) { + size &= ~(size_t)3; + + for (i = 0; i < size; i += 4) { instr = get_unaligned_be32(buf + i); if ((instr & 0xFC000003) == 0x48000001) { instr &= 0x03FFFFFC; @@ -218,7 +220,9 @@ static size_t bcj_ia64(struct xz_dec_bcj *s, uint8_t *buf, size_t size) /* Instruction normalized with bit_res for easier manipulation */ uint64_t norm; - for (i = 0; i + 16 <= size; i += 16) { + size &= ~(size_t)15; + + for (i = 0; i < size; i += 16) { mask = branch_table[buf[i] & 0x1F]; for (slot = 0, bit_pos = 5; slot < 3; ++slot, bit_pos += 41) { if (((mask >> slot) & 1) == 0) @@ -266,7 +270,9 @@ static size_t bcj_arm(struct xz_dec_bcj *s, uint8_t *buf, size_t size) size_t i; uint32_t addr; - for (i = 0; i + 4 <= size; i += 4) { + size &= ~(size_t)3; + + for (i = 0; i < size; i += 4) { if (buf[i + 3] == 0xEB) { addr = (uint32_t)buf[i] | ((uint32_t)buf[i + 1] << 8) | ((uint32_t)buf[i + 2] << 16); @@ -289,7 +295,12 @@ static size_t bcj_armthumb(struct xz_dec_bcj *s, uint8_t *buf, size_t size) size_t i; uint32_t addr; - for (i = 0; i + 4 <= size; i += 2) { + if (size < 4) + return 0; + + size -= 4; + + for (i = 0; i <= size; i += 2) { if ((buf[i + 1] & 0xF8) == 0xF0 && (buf[i + 3] & 0xF8) == 0xF8) { addr = (((uint32_t)buf[i + 1] & 0x07) << 19) @@ -317,7 +328,9 @@ static size_t bcj_sparc(struct xz_dec_bcj *s, uint8_t *buf, size_t size) size_t i; uint32_t instr; - for (i = 0; i + 4 <= size; i += 4) { + size &= ~(size_t)3; + + for (i = 0; i < size; i += 4) { instr = get_unaligned_be32(buf + i); if ((instr >> 22) == 0x100 || (instr >> 22) == 0x1FF) { instr <<= 2; -- 2.44.0