From patchwork Thu Sep 17 15:35:47 2015 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Eric Botcazou X-Patchwork-Id: 518917 Return-Path: X-Original-To: incoming@patchwork.ozlabs.org Delivered-To: patchwork-incoming@bilbo.ozlabs.org Received: from sourceware.org (server1.sourceware.org [209.132.180.131]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by ozlabs.org (Postfix) with ESMTPS id 110C91415A1 for ; Fri, 18 Sep 2015 01:36:41 +1000 (AEST) Authentication-Results: ozlabs.org; dkim=pass (1024-bit key; unprotected) header.d=gcc.gnu.org header.i=@gcc.gnu.org header.b=th/M+ZMR; dkim-atps=neutral DomainKey-Signature: a=rsa-sha1; c=nofws; d=gcc.gnu.org; h=list-id :list-unsubscribe:list-archive:list-post:list-help:sender:from :to:subject:date:message-id:mime-version:content-type :content-transfer-encoding; q=dns; s=default; b=f21pLmkAqx9DdAg4 FTESieorZFgkhCaO3CNsBB/4TgF6DbYkUtx5R+0AZqAJ8tDkx8dFVq8Oya8NYQUq gUDCvreMRCBDMJDRj6QYSHx5SwRikipWRw8d7l+nFrqaMWWA1Q3ePzraSaoELtsf Y27717A1W/uD4hG7HNkURd2sedo= DKIM-Signature: v=1; a=rsa-sha1; c=relaxed; d=gcc.gnu.org; h=list-id :list-unsubscribe:list-archive:list-post:list-help:sender:from :to:subject:date:message-id:mime-version:content-type :content-transfer-encoding; s=default; bh=Wk6X2gjRyYKRAfpYzAcl2M dspzg=; b=th/M+ZMRtWgYVtOxGawWaNwCxDc3sdyo5ZlmMym+BRLrrfd0EC6HSQ QZtQgmAeSiJ63x5lQG4A1DAs5VKBgSMWHyWP7Di0e1H3/iTMgtFt5GGV06cDjeeR lKIu3Yh0O/BEngaHThxvHkSXdVwBBPyogJTeABQQNC7fIWiLkH2gI= Received: (qmail 10176 invoked by alias); 17 Sep 2015 15:36:32 -0000 Mailing-List: contact gcc-patches-help@gcc.gnu.org; run by ezmlm Precedence: bulk List-Id: List-Unsubscribe: List-Archive: List-Post: List-Help: Sender: gcc-patches-owner@gcc.gnu.org Delivered-To: mailing list gcc-patches@gcc.gnu.org Received: (qmail 10150 invoked by uid 89); 17 Sep 2015 15:36:30 -0000 Authentication-Results: sourceware.org; auth=none X-Virus-Found: No X-Spam-SWARE-Status: No, score=0.0 required=5.0 tests=AWL, BAYES_50, KAM_ASCII_DIVIDERS, KAM_LAZY_DOMAIN_SECURITY, RCVD_IN_DNSWL_LOW autolearn=no version=3.3.2 X-HELO: smtp.eu.adacore.com Received: from mel.act-europe.fr (HELO smtp.eu.adacore.com) (194.98.77.210) by sourceware.org (qpsmtpd/0.93/v0.84-503-g423c35a) with (AES256-GCM-SHA384 encrypted) ESMTPS; Thu, 17 Sep 2015 15:36:27 +0000 Received: from localhost (localhost [127.0.0.1]) by filtered-smtp.eu.adacore.com (Postfix) with ESMTP id 648502A3AC13 for ; Thu, 17 Sep 2015 17:36:24 +0200 (CEST) Received: from smtp.eu.adacore.com ([127.0.0.1]) by localhost (smtp.eu.adacore.com [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id WWPdbCdpWsnK for ; Thu, 17 Sep 2015 17:36:24 +0200 (CEST) Received: from polaris.localnet (bon31-6-88-161-99-133.fbx.proxad.net [88.161.99.133]) (using TLSv1 with cipher ECDHE-RSA-AES256-SHA (256/256 bits)) (No client certificate requested) by smtp.eu.adacore.com (Postfix) with ESMTPSA id 4013D2A3AC11 for ; Thu, 17 Sep 2015 17:36:24 +0200 (CEST) From: Eric Botcazou To: gcc-patches@gcc.gnu.org Subject: Amend documentation of DF LIVE problem Date: Thu, 17 Sep 2015 17:35:47 +0200 Message-ID: <2726385.nUEyknGWlN@polaris> User-Agent: KMail/4.7.2 (Linux/3.1.10-1.29-desktop; KDE/4.7.2; x86_64; ; ) MIME-Version: 1.0 As discussed in the audit trail of PR rtl-optimization/66790, the doc of the DF_LIVE problem is confusing/wrong so the attached patch amends it. Approved by Kenneth and applied on all active branches. 2015-09-17 Eric Botcazou PR rtl-optimization/66790 * df-problems.c (LIVE): Amend documentation. Index: df-problems.c =================================================================== --- df-problems.c (revision 227819) +++ df-problems.c (working copy) @@ -1309,22 +1309,23 @@ df_lr_verify_transfer_functions (void) /*---------------------------------------------------------------------------- - LIVE AND MUST-INITIALIZED REGISTERS. + LIVE AND MAY-INITIALIZED REGISTERS. This problem first computes the IN and OUT bitvectors for the - must-initialized registers problems, which is a forward problem. - It gives the set of registers for which we MUST have an available - definition on any path from the entry block to the entry/exit of - a basic block. Sets generate a definition, while clobbers kill + may-initialized registers problems, which is a forward problem. + It gives the set of registers for which we MAY have an available + definition, i.e. for which there is an available definition on + at least one path from the entry block to the entry/exit of a + basic block. Sets generate a definition, while clobbers kill a definition. In and out bitvectors are built for each basic block and are indexed by regnum (see df.h for details). In and out bitvectors in struct - df_live_bb_info actually refers to the must-initialized problem; + df_live_bb_info actually refers to the may-initialized problem; Then, the in and out sets for the LIVE problem itself are computed. These are the logical AND of the IN and OUT sets from the LR problem - and the must-initialized problem. + and the may-initialized problem. ----------------------------------------------------------------------------*/ /* Private data used to verify the solution for this problem. */ @@ -1531,7 +1532,7 @@ df_live_confluence_n (edge e) } -/* Transfer function for the forwards must-initialized problem. */ +/* Transfer function for the forwards may-initialized problem. */ static bool df_live_transfer_function (int bb_index) @@ -1555,7 +1556,7 @@ df_live_transfer_function (int bb_index) } -/* And the LR info with the must-initialized registers, to produce the LIVE info. */ +/* And the LR info with the may-initialized registers to produce the LIVE info. */ static void df_live_finalize (bitmap all_blocks)