From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.1 (2015-04-28) on dcvr.yhbt.net X-Spam-Level: X-Spam-ASN: AS31976 209.132.180.0/23 X-Spam-Status: No, score=-11.4 required=3.0 tests=AWL,BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, RCVD_IN_DNSWL_HI,T_DKIMWL_WL_MED,USER_IN_DEF_DKIM_WL shortcircuit=no autolearn=ham autolearn_force=no version=3.4.1 Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by dcvr.yhbt.net (Postfix) with ESMTP id EE0911F597 for ; Thu, 19 Jul 2018 22:19:47 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730998AbeGSXEw (ORCPT ); Thu, 19 Jul 2018 19:04:52 -0400 Received: from mail-yw0-f201.google.com ([209.85.161.201]:41301 "EHLO mail-yw0-f201.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1730369AbeGSXEw (ORCPT ); Thu, 19 Jul 2018 19:04:52 -0400 Received: by mail-yw0-f201.google.com with SMTP id c204-v6so5184884ywa.8 for ; Thu, 19 Jul 2018 15:19:46 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20161025; h=mime-version:date:in-reply-to:message-id:references:subject:from:to :cc; bh=WwEXJhUMUccgT51nsSDrT9Jj1Fy2iOhxiNkEgW4VMeE=; b=mVqp/+DD2mW+ITHbZGDwMPgimPZO40xj6t0tGG32yTwIUbjCNJuODaZABsTQQsahfN y31lG5FPhgovU2zPeTs+/Gc8fu4+i8YjP5F1QukdFl0VVCoAZdQ91zqwVkZ41l6DpTPB V/qD7n79mmYL7Nj5ktWLMKR6hnHxEucJnO/gDszn1A8KBbztO4XBfwvsAHudBEY3u+e3 jUU1H4dTmTVJpn1GPyBUQHyaBSx63jweWqvFeo0zovSAn0EPD0RLePxe1Q/93l/YT7c0 Sm/QG3MYDppT6xKCP2ti01iIdJ5uNslQtov+HQ9Q+xs/uAyFZT/VYmnj4NwQ/nFtGXy6 JPLg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:date:in-reply-to:message-id :references:subject:from:to:cc; bh=WwEXJhUMUccgT51nsSDrT9Jj1Fy2iOhxiNkEgW4VMeE=; b=CWzSXJeRgBWo+WWa5EvCre+rD8YOMYfdjn/+Fpl7JSmSkhNVpFTLQ+QsbQrS94IDOA c4Gu27D6C2jiEnzraCYu7atfA18f4C9+Ta+0XnW5AI6NgMltoaBPhVcDnPWVhcvEeqEx c0nWL+g3xbHjz9uUVhlVRf5hbPjcCNyakvdocNnqMXcaqoAGf8SERMz3Ow0s7eeBlKOQ kLhMszF7baHOAXFfz7aseGZCdiFWcjAzHFsAd309+N/Y+lcE/vxKSa5MwftUXInEWsPZ CqCkIT/1uAxV9Og+XxIOhz8Dv56XDiCB7zcTUxQaC4Y/NiOHg4RRB4Yp5Y4qbkMnBdjX gKOg== X-Gm-Message-State: AOUpUlGroT16HRBJanJozFVyHJeTvbkPMx4H0pkioB2HSu5cwjOhA5Bf lJ78TccTZ7JlpocgPUXXQo3tDDQ85MjygMwhgCKel639HRb8CftXXD0UUrMWfNQ4NQaGmJ4EUat 6eeQEzDdxqnhFBakcVaQUXnlQ4laLOytHTZw/XWPmpVgE3m9d//aMtx2XKbsk X-Google-Smtp-Source: AAOMgpeBhYg9TcqyBWtVGXkbM1HXbEbjC6V4Bti/bz/JWR+nwCJLTwkSdmdrdBiNE1ZEGGMD/Qoag+WxTtGO MIME-Version: 1.0 X-Received: by 2002:a81:278c:: with SMTP id n134-v6mr3719273ywn.214.1532038785616; Thu, 19 Jul 2018 15:19:45 -0700 (PDT) Date: Thu, 19 Jul 2018 15:19:42 -0700 In-Reply-To: <20180719185620.124768-4-sbeller@google.com> Message-Id: <20180719221942.179565-1-sbeller@google.com> References: <20180719185620.124768-4-sbeller@google.com> X-Mailer: git-send-email 2.18.0.233.g985f88cf7e-goog Subject: [PATCH] xdiff/histogram: remove tail recursion From: Stefan Beller To: git@vger.kernel.org Cc: Stefan Beller Content-Type: text/plain; charset="UTF-8" Sender: git-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: git@vger.kernel.org When running the same reproduction script as the previous patch, it turns out the stack is too small, which can be easily avoided. Signed-off-by: Stefan Beller --- xdiff/xhistogram.c | 20 ++++++++++++++------ 1 file changed, 14 insertions(+), 6 deletions(-) diff --git a/xdiff/xhistogram.c b/xdiff/xhistogram.c index fc2d3cd95d9..ec85f5992bd 100644 --- a/xdiff/xhistogram.c +++ b/xdiff/xhistogram.c @@ -318,7 +318,9 @@ static int histogram_diff(xpparam_t const *xpp, xdfenv_t *env, { struct region lcs; int lcs_found; - int result = -1; + int result; +redo: + result = -1; if (count1 <= 0 && count2 <= 0) return 0; @@ -355,11 +357,17 @@ static int histogram_diff(xpparam_t const *xpp, xdfenv_t *env, line2, lcs.begin2 - line2); if (result) goto out; - result = histogram_diff(xpp, env, - lcs.end1 + 1, LINE_END(1) - lcs.end1, - lcs.end2 + 1, LINE_END(2) - lcs.end2); - if (result) - goto out; + /* + * result = histogram_diff(xpp, env, + * lcs.end1 + 1, LINE_END(1) - lcs.end1, + * lcs.end2 + 1, LINE_END(2) - lcs.end2); + * but let's optimize tail recursion ourself: + */ + count1 = LINE_END(1) - lcs.end1; + line1 = lcs.end1 + 1; + count2 = LINE_END(2) - lcs.end2; + line2 = lcs.end2 + 1; + goto redo; } } out: -- 2.18.0.233.g985f88cf7e-goog