From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (qmail 23490 invoked by alias); 30 Dec 2012 19:24:11 -0000 Received: (qmail 23480 invoked by uid 22791); 30 Dec 2012 19:24:10 -0000 X-SWARE-Spam-Status: No, hits=-4.9 required=5.0 tests=AWL,BAYES_00,DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,FREEMAIL_FROM,KHOP_RCVD_TRUST,KHOP_THREADED,RCVD_IN_DNSWL_LOW,RCVD_IN_HOSTKARMA_YE X-Spam-Check-By: sourceware.org Received: from mail-wg0-f51.google.com (HELO mail-wg0-f51.google.com) (74.125.82.51) by sourceware.org (qpsmtpd/0.43rc1) with ESMTP; Sun, 30 Dec 2012 19:24:05 +0000 Received: by mail-wg0-f51.google.com with SMTP id gg4so5409697wgb.6 for ; Sun, 30 Dec 2012 11:24:03 -0800 (PST) MIME-Version: 1.0 Received: by 10.180.75.208 with SMTP id e16mr60736676wiw.3.1356895443701; Sun, 30 Dec 2012 11:24:03 -0800 (PST) Received: by 10.194.179.130 with HTTP; Sun, 30 Dec 2012 11:24:03 -0800 (PST) In-Reply-To: <87d2y0vhms.fsf@talisman.default> References: <87d2y0vhms.fsf@talisman.default> Date: Sun, 30 Dec 2012 19:24:00 -0000 Message-ID: Subject: Re: RFA: Fix uint128_t range checking in VRP From: Richard Biener To: gcc-patches@gcc.gnu.org, rdsandiford@googlemail.com Content-Type: text/plain; charset=ISO-8859-1 X-IsSubscribed: yes 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 X-SW-Source: 2012-12/txt/msg01485.txt.bz2 On Sun, Dec 23, 2012 at 5:48 PM, Richard Sandiford wrote: > The minimum uint128_t value is an all-zeros double_int and the maximum > value is an all-ones double_int. Truncating these values to int and > then sign-extending them gives the same all-zeros and all-ones values, > so tree-vrp.c:range_fits_type_p concludes that uint128_t fits in an int. > > This showed up as a miscompilation of __fractutasf on mips64-linux-gnu, > which in turn showed up in convert-float-4.c. > > There was already code to handle this problem when changing the sign > and keeping the precision, but I think the rule applies regardless > of precision. > > Tested on x86_64-linux-gnu and mips64-linux-gnu. OK to install? Ok. Thanks, Richard. > Richard > > > gcc/ > * tree-vrp.c (range_fits_type_p): Require the MSB of the double_int > to be clear for sign changes. > > gcc/testsuite/ > * gcc.dg/torture/fp-int-convert-2.c: New test. > > Index: gcc/tree-vrp.c > =================================================================== > --- gcc/tree-vrp.c 2012-12-23 11:50:39.046419271 +0000 > +++ gcc/tree-vrp.c 2012-12-23 11:51:17.814677008 +0000 > @@ -8766,9 +8766,11 @@ range_fits_type_p (value_range_t *vr, un > || TREE_CODE (vr->max) != INTEGER_CST) > return false; > > - /* For precision-preserving sign-changes the MSB of the double-int > - has to be clear. */ > - if (src_precision == precision > + /* For sign changes, the MSB of the double_int has to be clear. > + An unsigned value with its MSB set cannot be represented by > + a signed double_int, while a negative value cannot be represented > + by an unsigned double_int. */ > + if (TYPE_UNSIGNED (src_type) != unsigned_p > && (TREE_INT_CST_HIGH (vr->min) | TREE_INT_CST_HIGH (vr->max)) < 0) > return false; > > Index: gcc/testsuite/gcc.dg/torture/fp-int-convert-2.c > =================================================================== > --- /dev/null 2012-12-03 19:06:31.446621561 +0000 > +++ gcc/testsuite/gcc.dg/torture/fp-int-convert-2.c 2012-12-23 13:46:35.449077882 +0000 > @@ -0,0 +1,18 @@ > +/* { dg-do run } */ > +/* { dg-require-effective-target int128 } */ > + > +extern void abort (void); > + > +float __attribute__((noinline)) > +f (__uint128_t x) > +{ > + return x + 1; > +} > + > +int > +main (void) > +{ > + if (f (0xffffffffu) == 0) > + abort (); > + return 0; > +}