From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (qmail 56560 invoked by alias); 14 Aug 2015 08:28:28 -0000 Mailing-List: contact gcc-patches-help@gcc.gnu.org; run by ezmlm Precedence: bulk List-Id: List-Archive: List-Post: List-Help: Sender: gcc-patches-owner@gcc.gnu.org Received: (qmail 56527 invoked by uid 89); 14 Aug 2015 08:28:27 -0000 Authentication-Results: sourceware.org; auth=none X-Virus-Found: No X-Spam-SWARE-Status: No, score=-2.0 required=5.0 tests=AWL,BAYES_00,FREEMAIL_FROM,RCVD_IN_DNSWL_LOW,SPF_PASS autolearn=ham version=3.3.2 X-HELO: mail-ig0-f169.google.com Received: from mail-ig0-f169.google.com (HELO mail-ig0-f169.google.com) (209.85.213.169) by sourceware.org (qpsmtpd/0.93/v0.84-503-g423c35a) with (AES128-GCM-SHA256 encrypted) ESMTPS; Fri, 14 Aug 2015 08:28:26 +0000 Received: by igui7 with SMTP id i7so7501000igu.0 for ; Fri, 14 Aug 2015 01:28:24 -0700 (PDT) MIME-Version: 1.0 X-Received: by 10.50.87.74 with SMTP id v10mr1553193igz.37.1439540903838; Fri, 14 Aug 2015 01:28:23 -0700 (PDT) Received: by 10.107.32.140 with HTTP; Fri, 14 Aug 2015 01:28:23 -0700 (PDT) In-Reply-To: <000801d0c919$220d0b70$66272250$@arm.com> References: <000801d0c919$220d0b70$66272250$@arm.com> Date: Fri, 14 Aug 2015 08:32:00 -0000 Message-ID: Subject: Re: [PATCH GCC]Improve loop bound info by simplifying conversions in iv base From: Richard Biener To: Bin Cheng Cc: GCC Patches Content-Type: text/plain; charset=UTF-8 X-IsSubscribed: yes X-SW-Source: 2015-08/txt/msg00762.txt.bz2 On Tue, Jul 28, 2015 at 11:38 AM, Bin Cheng wrote: > Hi, > For now, SCEV may compute iv base in the form of "(signed T)((unsigned > T)base + step))". This complicates other optimizations/analysis depending > on SCEV because it's hard to dive into type conversions. For many cases, > such type conversions can be simplified with additional range information > implied by loop initial conditions. This patch does such simplification. > With simplified iv base, loop niter analysis can compute more accurate bound > information since sensible value range can be derived for "base+step". For > example, accurate loop bound&may_be_zero information is computed for cases > added by this patch. > The code is actually borrowed from loop_exits_before_overflow. Moreover, > with simplified iv base, the second case handled in that function now > becomes the first case. I didn't remove that part of code because it may(?) > still be visited in scev analysis itself and simple_iv isn't an interface > for that. > > Is it OK? It looks quite special given it only handles a very specific pattern. Did you do any larger collecting of statistics on how many times this triggers, esp. how many times simplify_using_initial_conditions succeeds and how many times not? This function is somewhat expensive. + || !operand_equal_p (iv->step, + fold_convert (type, + TREE_OPERAND (e, 1)), 0)) operand_equal_p can handle sign-differences in integer constants, no need to fold_convert here. Also if you know that you are comparing integer constants please use tree_int_cst_equal_p. + extreme = lower_bound_in_type (type, type); that's a strange function to call here (with two same types). Looks like just wide_int_to_tree (type, wi::max/min_value (type)). + extreme = fold_build2 (MINUS_EXPR, type, extreme, iv->step); so as iv->step is an INTEGER_CST please do this whole thing using wide_ints and only build trees here: + e = fold_build2 (code, boolean_type_node, base, extreme); Thanks, Richard. > Thanks, > bin > > 2015-07-28 Bin Cheng > > * tree-ssa-loop-niter.c (tree_simplify_using_condition): Export > the interface. > * tree-ssa-loop-niter.h (tree_simplify_using_condition): Declare. > * tree-scalar-evolution.c (simple_iv): Simplify type conversions > in iv base using loop initial conditions. > > gcc/testsuite/ChangeLog > 2015-07-28 Bin Cheng > > * gcc.dg/tree-ssa/loop-bound-2.c: New test. > * gcc.dg/tree-ssa/loop-bound-4.c: New test. > * gcc.dg/tree-ssa/loop-bound-6.c: New test.