From patchwork Wed Aug 9 19:38:05 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: 9891735 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 5460C602D7 for ; Wed, 9 Aug 2017 19:39:10 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 467052832D for ; Wed, 9 Aug 2017 19:39:10 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id 3A12128672; Wed, 9 Aug 2017 19:39:10 +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 36BD92832D for ; Wed, 9 Aug 2017 19:39:09 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751944AbdHITjI (ORCPT ); Wed, 9 Aug 2017 15:39:08 -0400 Received: from mail-wm0-f67.google.com ([74.125.82.67]:33422 "EHLO mail-wm0-f67.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751932AbdHITjI (ORCPT ); Wed, 9 Aug 2017 15:39:08 -0400 Received: by mail-wm0-f67.google.com with SMTP id q189so631296wmd.0 for ; Wed, 09 Aug 2017 12:39:07 -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=dUSUXHZDA8x8zcsVbG1NgPkZUBwW8+6eYKczBpvIPAA=; b=rHyhF3DjdNFFzllkiK8y+Jwo7l21+5lY4zGcfo/nVu/vOQkzXIHfrkj+Xthpu0ztqT JOjBDgAv1G1EIDHNyVtV873Fp/7SexscZqX8vgK2VIqKjbQPK9bfnorD87q5hpio3f+q KsqSmMJBRuuUGxf5wksa7NwnQN8UU8swPo0whFNRDu7T4+6ZEJi/u/BDRZ9VsiLzRyV0 j/zT8x5zkcMVjx8M3aWAGaiVqKynrCRZZB49Q37Hf+tJzln+9OBfuQE4kqfccJQj+B3b QAcD1P6Z5nJbOvwWFjtJpAj44LFg7SLgw4qVYKnOrR4EDU7//eIVwvv1DSU2xZFP0Lfa V3Xw== 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=dUSUXHZDA8x8zcsVbG1NgPkZUBwW8+6eYKczBpvIPAA=; b=UI6Ddx6jo1SzEjvhFn7f3ukPIxdc3F68o0JoNRu4Adn9gTpwpVF9vOrEdLCRbw0nwj 55ieVUoZ94c5FYM07EtN9bwFOwhtKqWWWo+0UxeM9pjjX5enRQLHi2ospaCgyILoMLgq HuN8iiweSY8hLOlr4pfLsuZWdyyTjsE6cL90OAgAig6cECQrCV+8+8imt+RfjGrjYUbn r/PChM3SWpkq1+irbUrTFmpaWqKaIJXM1VEJVQSFG3YiBHcePJ/hzzZ6YD6emP9QiBI5 oo7FUstZAS7sri15BwFXbUx+MqyZGPRqIPSHAINnNOhUjGYeC6WgJ+MlXzXL48Hs5gcl oW1g== X-Gm-Message-State: AHYfb5hiS4O3FPDEQ6JNA7yKkdQSGtxl3b0vSmF8osmv5pgbarV0Iw0A giQMA+Hter38CrxAFk4= X-Received: by 10.80.212.14 with SMTP id t14mr9519458edh.172.1502307546981; Wed, 09 Aug 2017 12:39:06 -0700 (PDT) Received: from localhost.localdomain ([2a02:a03f:4076:600:a54f:2a42:70ce:5bd2]) by smtp.gmail.com with ESMTPSA id t36sm2984437edb.38.2017.08.09.12.39.05 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Wed, 09 Aug 2017 12:39:06 -0700 (PDT) From: Luc Van Oostenryck To: linux-sparse@vger.kernel.org Cc: Christopher Li , Luc Van Oostenryck Subject: [PATCH v4 8/9] transform (A << S) >> S into A & (-1 >> S) Date: Wed, 9 Aug 2017 21:38:05 +0200 Message-Id: <20170809193806.30975-9-luc.vanoostenryck@gmail.com> X-Mailer: git-send-email 2.14.0 In-Reply-To: <20170809193806.30975-1-luc.vanoostenryck@gmail.com> References: <20170809193806.30975-1-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 e8bf1c171..370d4cb81 100644 --- a/simplify.c +++ b/simplify.c @@ -415,6 +415,8 @@ 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); @@ -433,6 +435,21 @@ 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; }