From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: by sourceware.org (Postfix, from userid 2136) id 3049A3AA88ED; Tue, 30 Aug 2022 15:43:51 +0000 (GMT) DKIM-Filter: OpenDKIM Filter v2.11.0 sourceware.org 3049A3AA88ED DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gcc.gnu.org; s=default; t=1661874231; bh=gKcLb2SqDihFyLVmyKRe3PTdqDawnJnLiz3wNvNvMXo=; h=From:To:Subject:Date:From; b=d8LlWuhKDNtMvGQ/h0XstP9FVT6/JWDQ1qxiBxhbv6gVFt15mVcW5M4KMUw2hj52e 717QuXjRFm/z/qR7rDBw4f1/PrL+MAo9U2zX3ZcnWEf/0dsJhB5RdWEh+HEyFxZOT1 YTjflCsmUpub9qXDH6dAKskFNsT2c5zQnBZkx9wM= MIME-Version: 1.0 Content-Transfer-Encoding: 7bit Content-Type: text/plain; charset="utf-8" From: Aldy Hernandez To: gcc-cvs@gcc.gnu.org Subject: [gcc r13-2292] Improve union of ranges containing NAN. X-Act-Checkin: gcc X-Git-Author: Aldy Hernandez X-Git-Refname: refs/heads/master X-Git-Oldrev: b73c49f6f88dd7f7569f9a72c8ceb04598d4c15c X-Git-Newrev: 75f59441cd63a1d07e86d70d59c518049f53904f Message-Id: <20220830154351.3049A3AA88ED@sourceware.org> Date: Tue, 30 Aug 2022 15:43:51 +0000 (GMT) List-Id: https://gcc.gnu.org/g:75f59441cd63a1d07e86d70d59c518049f53904f commit r13-2292-g75f59441cd63a1d07e86d70d59c518049f53904f Author: Aldy Hernandez Date: Tue Aug 30 15:46:43 2022 +0200 Improve union of ranges containing NAN. Previously [5,6] U NAN would just drop to VARYING. With this patch, the resulting range becomes [5,6] with the NAN bit set to unknown. [I still have yet to decide what to do with intersections. ISTM, the intersection of a known NAN with anything else should be a NAN, but it could also be undefined (the empty set). I'll have to run some tests and see. Currently, we drop to VARYING cause well... it's always safe to give up;-).] gcc/ChangeLog: * value-range.cc (early_nan_resolve): Change comment. (frange::union_): Handle union when one side is a NAN. (range_tests_nan): Add tests for NAN union. Diff: --- gcc/value-range.cc | 44 ++++++++++++++++++++++++++++++++++---------- 1 file changed, 34 insertions(+), 10 deletions(-) diff --git a/gcc/value-range.cc b/gcc/value-range.cc index b6d6c62c06c..473139c6dbd 100644 --- a/gcc/value-range.cc +++ b/gcc/value-range.cc @@ -403,7 +403,7 @@ early_nan_resolve (frange &r, const frange &other) // There's nothing to do for both NANs. if (r.get_nan ().yes_p () == other.get_nan ().yes_p ()) return false; - // But only one NAN complicates things. + // ?? Perhaps the intersection of a NAN and anything is a NAN ??. r.set_varying (r.type ()); return true; } @@ -420,10 +420,22 @@ frange::union_ (const vrange &v) *this = r; return true; } - // ?? We could do better here. [5,6] U NAN should be [5,6] with the - // NAN maybe bits set. For now, this is conservatively correct. - if (get_nan ().yes_p () || r.get_nan ().yes_p ()) - return early_nan_resolve (*this, r); + + // If one side has a NAN, the union is just the other side plus the + // NAN bit. + if (get_nan ().yes_p ()) + { + *this = r; + // NOP if NAN already set. + set_nan (fp_prop::VARYING); + return true; + } + if (r.get_nan ().yes_p ()) + { + // NOP if NAN already set. + set_nan (fp_prop::VARYING); + return true; + } bool changed = m_props.union_ (r.m_props); @@ -3520,6 +3532,7 @@ static void range_tests_nan () { frange r0, r1; + REAL_VALUE_TYPE q, r; // Equal ranges but with differing NAN bits are not equal. r1 = frange_float ("10", "12"); @@ -3537,13 +3550,24 @@ range_tests_nan () ASSERT_FALSE (r0 == r0); ASSERT_TRUE (r0 != r0); - // Make sure that combining NAN and INF doesn't give any crazy results. + // [5,6] U NAN is [5,6] with an unknown NAN bit. + r0 = frange_float ("5", "6"); + r0.set_nan (fp_prop::NO); + r1 = frange_nan (float_type_node); + r0.union_ (r1); + real_from_string (&q, "5"); + real_from_string (&r, "6"); + ASSERT_TRUE (real_identical (&q, &r0.lower_bound ())); + ASSERT_TRUE (real_identical (&r, &r0.upper_bound ())); + ASSERT_TRUE (r0.get_nan ().varying_p ()); + + // NAN U NAN = NAN r0 = frange_nan (float_type_node); - ASSERT_TRUE (r0.get_nan ().yes_p ()); - r1 = frange_float ("+Inf", "+Inf"); + r1 = frange_nan (float_type_node); r0.union_ (r1); - // [INF, INF] U NAN = VARYING - ASSERT_TRUE (r0.varying_p ()); + ASSERT_TRUE (real_isnan (&r0.lower_bound ())); + ASSERT_TRUE (real_isnan (&r1.upper_bound ())); + ASSERT_TRUE (r0.get_nan ().yes_p ()); // [INF, INF] ^ NAN = VARYING r0 = frange_nan (float_type_node);