From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-qk1-x732.google.com (mail-qk1-x732.google.com [IPv6:2607:f8b0:4864:20::732]) by sourceware.org (Postfix) with ESMTPS id E70BB383B799 for ; Tue, 21 Jun 2022 07:43:27 +0000 (GMT) DMARC-Filter: OpenDMARC Filter v1.4.1 sourceware.org E70BB383B799 Received: by mail-qk1-x732.google.com with SMTP id d23so9456792qke.0 for ; Tue, 21 Jun 2022 00:43:27 -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=GAUP22W74ULz88fid/bTwWCaLNIhr8XzBz+LstOFQNo=; b=cfKla34LD6dX49bq/Nw4cHRgcqpV6f/NMudUSir/Aty3RNxjQI1fl1kxoRvW9KS3PE 5VX2h3sFrJxbmH+nsOgEIUsL5tGeLyBP1ZFzSyXql4gXCmQ2vE5tPEhrqesUXXcL1s6T F+hulgF3LkMPN/Z3x/jKp0C4mAs8O6DHm+ac1UE0yXaY/y+5jwzn+2oiyzmjwsbuDBvZ 8ByFrsh12ydxmbkFnuU2SmGAK1RoJoc4p2p9LGNK2aheWSDQqq84tO4YTR0GopsQAZP/ pkpGk1x+q/95eU7aeCghF+Ljck4eReCDhhqRvhv+mnHQxO7De/K1ItIluba80Hw/Eoc6 OmNw== X-Gm-Message-State: AJIora/u5aXnzc7RzQoewnyu5I5SuidjRAWira4lhZo4G32CtfA/H0GT YUzYYlEcyBqj3d3HYpZa/z3MLo6l88R5c+4fYyE= X-Google-Smtp-Source: AGRyM1uu4MotwI+acNAJpyVFVmHgKL7SgT4BUSFNnSv32Xrgllbdn4KqpeGURaviw0gN7HlHNtwEaOjRzBAdwrFmXc0= X-Received: by 2002:a37:a252:0:b0:6a9:756d:d16d with SMTP id l79-20020a37a252000000b006a9756dd16dmr18605271qke.350.1655797407322; Tue, 21 Jun 2022 00:43:27 -0700 (PDT) MIME-Version: 1.0 References: In-Reply-To: From: Richard Biener Date: Tue, 21 Jun 2022 09:43:16 +0200 Message-ID: Subject: Re: [PATCH 1/2]middle-end: Simplify subtract where both arguments are being bitwise inverted. To: Tamar Christina Cc: Richard Sandiford , Richard Biener via Gcc-patches , Richard Guenther , nd Content-Type: text/plain; charset="UTF-8" X-Spam-Status: No, score=-8.1 required=5.0 tests=BAYES_00, DKIM_SIGNED, DKIM_VALID, DKIM_VALID_AU, DKIM_VALID_EF, FREEMAIL_FROM, GIT_PATCH_0, 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 07:43:29 -0000 On Mon, Jun 20, 2022 at 10:49 AM Tamar Christina wrote: > > > -----Original Message----- > > From: Richard Sandiford > > Sent: Monday, June 20, 2022 9:19 AM > > To: Richard Biener via Gcc-patches > > Cc: Tamar Christina ; Richard Biener > > ; Richard Guenther ; > > nd > > Subject: Re: [PATCH 1/2]middle-end: Simplify subtract where both > > arguments are being bitwise inverted. > > > > Richard Biener via Gcc-patches writes: > > > On Thu, Jun 16, 2022 at 1:10 PM Tamar Christina via Gcc-patches > > > wrote: > > >> > > >> Hi All, > > >> > > >> This adds a match.pd rule that drops the bitwwise nots when both > > >> arguments to a subtract is inverted. i.e. for: > > >> > > >> float g(float a, float b) > > >> { > > >> return ~(int)a - ~(int)b; > > >> } > > >> > > >> we instead generate > > >> > > >> float g(float a, float b) > > >> { > > >> return (int)a - (int)b; > > >> } > > >> > > >> We already do a limited version of this from the fold_binary fold > > >> functions but this makes a more general version in match.pd that applies > > more often. > > >> > > >> Bootstrapped Regtested on aarch64-none-linux-gnu and no issues. > > >> > > >> Ok for master? > > >> > > >> Thanks, > > >> Tamar > > >> > > >> gcc/ChangeLog: > > >> > > >> * match.pd: New bit_not rule. > > >> > > >> gcc/testsuite/ChangeLog: > > >> > > >> * gcc.dg/subnot.c: New test. > > >> > > >> --- inline copy of patch -- > > >> diff --git a/gcc/match.pd b/gcc/match.pd index > > >> > > a59b6778f661cf9121dd3503f43472871e4da445..51b0a1b562409af535e53828a1 > > 0 > > >> c30b8a3e1ae2e 100644 > > >> --- a/gcc/match.pd > > >> +++ b/gcc/match.pd > > >> @@ -1258,6 +1258,10 @@ DEFINE_INT_AND_FLOAT_ROUND_FN (RINT) > > >> (simplify > > >> (bit_not (plus:c (bit_not @0) @1)) > > >> (minus @0 @1)) > > >> +/* (~X - ~Y) -> X - Y. */ > > >> +(simplify > > >> + (minus (bit_not @0) (bit_not @1)) > > >> + (minus @0 @1)) > > > > > > It doesn't seem correct. > > > > > > (gdb) p/x ~-1 - ~0x80000000 > > > $3 = 0x80000001 > > > (gdb) p/x -1 - 0x80000000 > > > $4 = 0x7fffffff > > > > > > where I was looking for a case exposing undefined integer overflow. > > > > Yeah, shouldn't it be folding to (minus @1 @0) instead? > > > > ~X = (-X - 1) > > -Y = (-Y - 1) > > > > so: > > > > ~X - ~Y = (-X - 1) - (-Y - 1) > > = -X - 1 + Y + 1 > > = Y - X > > > > You're right, sorry, I should have paid more attention when I wrote the patch. You still need to watch out for undefined overflow cases in the result that were well-defined in the original expression I think. Richard. > Tamar > > Richard > > > > > > > Richard. > > > > > >> > > >> /* ~(X - Y) -> ~X + Y. */ > > >> (simplify > > >> diff --git a/gcc/testsuite/gcc.dg/subnot.c > > >> b/gcc/testsuite/gcc.dg/subnot.c new file mode 100644 index > > >> > > 0000000000000000000000000000000000000000..d621bacd27bd3d19a010e4c9f > > 83 > > >> 1aa77d28bd02d > > >> --- /dev/null > > >> +++ b/gcc/testsuite/gcc.dg/subnot.c > > >> @@ -0,0 +1,9 @@ > > >> +/* { dg-do compile } */ > > >> +/* { dg-options "-O -fdump-tree-optimized" } */ > > >> + > > >> +float g(float a, float b) > > >> +{ > > >> + return ~(int)a - ~(int)b; > > >> +} > > >> + > > >> +/* { dg-final { scan-tree-dump-not "~" "optimized" } } */ > > >> > > >> > > >> > > >> > > >> --