From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-yb1-xb2d.google.com (mail-yb1-xb2d.google.com [IPv6:2607:f8b0:4864:20::b2d]) by sourceware.org (Postfix) with ESMTPS id 34AFE3857C50 for ; Tue, 21 Jun 2022 18:13:56 +0000 (GMT) DMARC-Filter: OpenDMARC Filter v1.4.1 sourceware.org 34AFE3857C50 Received: by mail-yb1-xb2d.google.com with SMTP id l66so24426312ybl.10 for ; Tue, 21 Jun 2022 11:13:56 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=GczBrHYPJgxjy7H2XGTgQSR/hF45ts0PqoSIqm3ZU6A=; b=OcmSlNfYk0ojtc76oEwFTYjgcTf2oSw6jzZJ3hJ6WRKWNU7biUkj4loAoc7FO7e1gR N9rQUNnbZXSGyhqI3xZBjDD4zJI3H6IjsSO++hMu1XviimaUmq038o88QINwkGyt2R+V a6JeXXvD8RZ3aY2kMrAEIKpevU3fRBL6tthiBCz6839f2IvrYcauJZVbc9vcNlOQ8y5L ekI/6qMOd1LhCnOCgeUiRZTXTnRGiLA2BK0OSlD2zLi4CpBVjNAgV0CmVGkH3QUZVWd9 zpy05yr2YhgNNK6ba5pgH9Oy/zEapB3N+L8MuBETEey+f7JwVuDejJ4rs/tDqKA2APNh qltA== X-Gm-Message-State: AJIora+IQMgYC3G2FduqrkjsnlnMocryzisr7zNqBP4vCNXads2QMq2E Z2C2Ne4qGx3KzuRsV3V+8K/Q+mf0ziBzf2/f6PE= X-Google-Smtp-Source: AGRyM1t/KANrUfQ7BQQSpNbdAFS4GiZDXoPj23jo61putldOEbGODdkE0TQPH2jt21XCg1YO3kYSup0NaM1qzi9Vk3M= X-Received: by 2002:a05:6902:706:b0:669:2493:acd8 with SMTP id k6-20020a056902070600b006692493acd8mr10010973ybt.208.1655835235408; Tue, 21 Jun 2022 11:13:55 -0700 (PDT) MIME-Version: 1.0 References: <20220620163536.2653437-1-goldstein.w.n@gmail.com> <20220620214220.2776648-1-goldstein.w.n@gmail.com> In-Reply-To: From: Noah Goldstein Date: Tue, 21 Jun 2022 11:13:44 -0700 Message-ID: Subject: Re: [PATCH v2] tree-optimization/95821 - Convert strlen + strchr to memchr To: Jakub Jelinek Cc: gcc-patches List , "H.J. Lu" Content-Type: text/plain; charset="UTF-8" X-Spam-Status: No, score=-2.4 required=5.0 tests=BAYES_00, DKIM_SIGNED, DKIM_VALID, DKIM_VALID_AU, DKIM_VALID_EF, FREEMAIL_FROM, KAM_SHORT, RCVD_IN_DNSWL_NONE, SPF_HELO_NONE, SPF_PASS, TXREP, T_SCC_BODY_TEXT_LINE autolearn=ham autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on server2.sourceware.org X-BeenThere: gcc-patches@gcc.gnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Gcc-patches mailing list List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Tue, 21 Jun 2022 18:13:58 -0000 On Tue, Jun 21, 2022 at 5:01 AM Jakub Jelinek wrote: > > On Mon, Jun 20, 2022 at 02:42:20PM -0700, Noah Goldstein wrote: > > This patch allows for strchr(x, c) to the replace with memchr(x, c, > > strlen(x) + 1) if strlen(x) has already been computed earlier in the > > tree. > > > > Handles PR95821: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=95821 > > > > Since memchr doesn't need to re-find the null terminator it is faster > > than strchr. > > > > bootstrapped and tested on x86_64-linux. > > > > PR tree-optimization/95821 > > This should be indented by a single tab, not two. Fixed in V3 > > > > gcc/ > > > > * tree-ssa-strlen.cc (strlen_pass::handle_builtin_strchr): Emit > > memchr instead of strchr if strlen already computed. > > > > gcc/testsuite/ > > > > * c-c++-common/pr95821-1.c: New test. > > * c-c++-common/pr95821-2.c: New test. > > * c-c++-common/pr95821-3.c: New test. > > * c-c++-common/pr95821-4.c: New test. > > * c-c++-common/pr95821-5.c: New test. > > * c-c++-common/pr95821-6.c: New test. > > * c-c++-common/pr95821-7.c: New test. > > * c-c++-common/pr95821-8.c: New test. > > --- a/gcc/tree-ssa-strlen.cc > > +++ b/gcc/tree-ssa-strlen.cc > > @@ -2405,9 +2405,12 @@ strlen_pass::handle_builtin_strlen () > > } > > } > > > > -/* Handle a strchr call. If strlen of the first argument is known, replace > > - the strchr (x, 0) call with the endptr or x + strlen, otherwise remember > > - that lhs of the call is endptr and strlen of the argument is endptr - x. */ > > +/* Handle a strchr call. If strlen of the first argument is known, > > + replace the strchr (x, 0) call with the endptr or x + strlen, > > + otherwise remember that lhs of the call is endptr and strlen of the > > + argument is endptr - x. If strlen of x is not know but has been > > + computed earlier in the tree then replace strchr(x, c) to > > Still missing space before ( above. Sorry, fixed that in V3. > > > + memchr (x, c, strlen + 1). */ > > > > void > > strlen_pass::handle_builtin_strchr () > > @@ -2418,8 +2421,12 @@ strlen_pass::handle_builtin_strchr () > > if (lhs == NULL_TREE) > > return; > > > > - if (!integer_zerop (gimple_call_arg (stmt, 1))) > > - return; > > + tree chr = gimple_call_arg (stmt, 1); > > + /* strchr only uses the lower char of input so to check if its > > + strchr (s, zerop) only take into account the lower char. */ > > + bool is_strchr_zerop > > + = (TREE_CODE (chr) == INTEGER_CST > > + && integer_zerop (fold_convert (char_type_node, chr))); > > The indentation rule is that = should be 2 columns to the right from bool, > so > Fixed in V3. > bool is_strchr_zerop > = (TREE_CODE (chr) == INTEGER_CST > && integer_zerop (fold_convert (char_type_node, chr))); > > > + /* If its not strchr (s, zerop) then try and convert to > > + memchr since strlen has already been computed. */ > > This comment still has the second line weirdly indented. Sorry, have emacs with 4-space tabs so things that look right arent as they seem :/ Fixed in V3 I believe. > > > + tree fn = builtin_decl_explicit (BUILT_IN_MEMCHR); > > + > > + /* Only need to check length strlen (s) + 1 if chr may be zero. > > + Otherwise the last chr (which is known to be zero) can never > > + be a match. NB: We don't need to test if chr is a non-zero > > + integer const with zero char bits because that is taken into > > + account with is_strchr_zerop. */ > > + if (!tree_expr_nonzero_p (chr)) > > The above is unsafe though. tree_expr_nonzero_p (chr) will return true > if say VRP can prove it is not zero, but because of the implicit > (char) chr cast done by the function we need something different. > Say if VRP determines that chr is in [1, INT_MAX] or even just [255, 257] > it doesn't mean (char) chr won't be 0. > So, as I've tried to explain in the previous mail, it can be done e.g. with Added your code in V3. Thanks for the help. > bool chr_nonzero = false; > if (TREE_CODE (chr) == INTEGER_CST > && integer_nonzerop (fold_convert (char_type_node, chr))) > chr_nonzero = true; > else if (TREE_CODE (chr) == SSA_NAME > && CHAR_TYPE_SIZE < INT_TYPE_SIZE) > { > value_range r; > /* Try to determine using ranges if (char) chr must > be always 0. That is true e.g. if all the subranges > have the INT_TYPE_SIZE - CHAR_TYPE_SIZE bits > the same on lower and upper bounds. */ > if (get_range_query (cfun)->range_of_expr (r, chr, stmt) > && r.kind () == VR_RANGE) > { > chr_nonzero = true; > wide_int mask = wi::mask (CHAR_TYPE_SIZE, true, > INT_TYPE_SIZE); > for (int i = 0; i < r.num_pairs (); ++i) > if ((r.lower_bound (i) & mask) > != (r.upper_bound (i) & mask)) > { > chr_nonzero = false; > break; > } > } > } > if (!chr_nonzero) > > Jakub >