From patchwork Tue Aug 8 23:06:33 2017 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Luc Van Oostenryck X-Patchwork-Id: 9889243 Return-Path: Received: from mail.wl.linuxfoundation.org (pdx-wl-mail.web.codeaurora.org [172.30.200.125]) by pdx-korg-patchwork.web.codeaurora.org (Postfix) with ESMTP id 3329760363 for ; Tue, 8 Aug 2017 23:07:06 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 2580D28A1E for ; Tue, 8 Aug 2017 23:07:06 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id 1846B2891C; Tue, 8 Aug 2017 23:07:06 +0000 (UTC) X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on pdx-wl-mail.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-6.3 required=2.0 tests=BAYES_00, DKIM_ADSP_CUSTOM_MED, DKIM_SIGNED, FREEMAIL_FROM, RCVD_IN_DNSWL_HI, RCVD_IN_SORBS_SPAM, T_DKIM_INVALID autolearn=ham version=3.3.1 Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id B78792891C for ; Tue, 8 Aug 2017 23:07:05 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752491AbdHHXHE (ORCPT ); Tue, 8 Aug 2017 19:07:04 -0400 Received: from mail-wm0-f65.google.com ([74.125.82.65]:33794 "EHLO mail-wm0-f65.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752475AbdHHXHB (ORCPT ); Tue, 8 Aug 2017 19:07:01 -0400 Received: by mail-wm0-f65.google.com with SMTP id x64so4929617wmg.1 for ; Tue, 08 Aug 2017 16:07:00 -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; bh=LZIOFpQk9Pq5omk1dAqHjsRdn52zPpPpdxmJeVRNZDM=; b=WxNHZKZrQHzpRLzE/rHL6DLRUesBVQSwkHGQRL1L+gLyVZqYfAEfoSm87LMik5cWgp mbVPyY5eeCebgPEM9Brf7wJDWzVAsSpZKxSx/QvEZdmCO32/3mOjeEOKmqaVSLp5ExtB NlnXBrkNe5J0kt0rn2Uqx9ndQ0Db+Bax5cZhzF2x2rjk4t1F3Y3slJkaGC5rUUp/B2OI mmguTc6ZT3CZHMTIHru6wJHJ6WQJK7JOpxiuAIa5vliSqZAbUmq35E8reUFdNCBPMCWj B+BINf4j1Kodg2xuyVnY/OfAbEpgF8mAvUbh/UIkLqqEzVGBsfqrvsRb0P+flnUYjZl7 zyOw== 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; bh=LZIOFpQk9Pq5omk1dAqHjsRdn52zPpPpdxmJeVRNZDM=; b=av8wE67JJ2qNbm3mQZyyx03/BxmeYkDqpFklUx8kpPZ8QnLNRC7+r+Z2rYVEJhYTUb 3sqjinb5FpvGB9PUCcLLWz2kgng+vZ3QPNr5mzRu0y3OiCVPI27XyaQ/I/faEyXv4UNt f8Sg1zCA8igNSu6rowDgN0/zOPjm5eK+3MnTHAluZu02bruPESXjqDJM4+FDKaurKDOa s0/hlTpd2SwEONWatrhICOCFhBtttP1+sE+UKPnhVUll4WzPPlKqNdTz/3P7JbaUYa0c yNNGOxKxs2kQLzdFjdjEVY1007HN8oeD2rfoFM7xSerQIZ7P5WnkAOunH8/95ZHMIZNi DNiA== X-Gm-Message-State: AHYfb5jwgHFiJdiobqLJ6tqQBm3usqbGMx8Pgud4/SsIoWBBlLyALbo2 1wCcOkx1gXtqnf/msfo= X-Received: by 10.80.141.70 with SMTP id t6mr5971708edt.75.1502233619489; Tue, 08 Aug 2017 16:06:59 -0700 (PDT) Received: from localhost.localdomain ([2a02:a03f:4076:600:6494:649b:1a34:f1b]) by smtp.gmail.com with ESMTPSA id n15sm1133490edb.87.2017.08.08.16.06.58 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Tue, 08 Aug 2017 16:06:58 -0700 (PDT) From: Luc Van Oostenryck To: linux-sparse@vger.kernel.org Cc: Christopher Li , Linus Torvalds , Dibyendu Majumdar , Luc Van Oostenryck Subject: [PATCH v3 7/8] transform (A << S) >> S into A & (-1 >> S) Date: Wed, 9 Aug 2017 01:06:33 +0200 Message-Id: <20170808230634.16227-8-luc.vanoostenryck@gmail.com> X-Mailer: git-send-email 2.13.2 In-Reply-To: <20170808230634.16227-1-luc.vanoostenryck@gmail.com> References: <20170808230634.16227-1-luc.vanoostenryck@gmail.com> Sender: linux-sparse-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-sparse@vger.kernel.org X-Virus-Scanned: ClamAV using ClamSMTP More exactly, transform it into: A & (Mask(size) >> S) which is equivalent to: A & Mask(size - S) where Mask(X) is ((1 << X) - 1) This transformation is especially usefull when simplifying code accessing bitfields or for other masking manipulations. Signed-off-by: Luc Van Oostenryck --- simplify.c | 17 +++++++++++++++++ 1 file changed, 17 insertions(+) diff --git a/simplify.c b/simplify.c index f1a898700..23cdd19ae 100644 --- a/simplify.c +++ b/simplify.c @@ -416,6 +416,8 @@ static int simplify_lsr(struct instruction *insn, pseudo_t pseudo, long long val { struct instruction *def; unsigned long long mask; + unsigned int width; + pseudo_t old; if (!value) return replace_with_pseudo(insn, pseudo); @@ -434,6 +436,21 @@ static int simplify_lsr(struct instruction *insn, pseudo_t pseudo, long long val insn->opcode = OP_AND; insn->src2 = value_pseudo(mask >> value); return REPEAT_CSE; + case OP_SHL: + // replace (A << S) >> S + // by A & (Mask(size) >> S) + def = insn->src1->def; + if (!constant(def->src2)) + break; + if (def->src2->value != value) + break; + width = insn->size - value; + insn->src2 = value_pseudo((1ULL << width) - 1); + insn->opcode = OP_AND; + old = insn->src1; + use_pseudo(insn, def->src1, &insn->src1); + remove_usage(old, &insn->src1); + return REPEAT_CSE; } return 0; }