From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: by sourceware.org (Postfix, from userid 2181) id D01B73858C20; Thu, 10 Mar 2022 14:25:57 +0000 (GMT) DKIM-Filter: OpenDKIM Filter v2.11.0 sourceware.org D01B73858C20 MIME-Version: 1.0 Content-Transfer-Encoding: 7bit Content-Type: text/plain; charset="utf-8" From: Jonathan Wakely To: gcc-cvs@gcc.gnu.org, libstdc++-cvs@gcc.gnu.org Subject: [gcc r12-7597] libstdc++: Fix std::strong_order to handle NaN on VAX X-Act-Checkin: gcc X-Git-Author: Jonathan Wakely X-Git-Refname: refs/heads/master X-Git-Oldrev: c65d3c7f9dade18826d1a28d71b98c7cdc3e4300 X-Git-Newrev: 73f3b8a53e6664c079731c2a183c16621481d039 Message-Id: <20220310142557.D01B73858C20@sourceware.org> Date: Thu, 10 Mar 2022 14:25:57 +0000 (GMT) X-BeenThere: libstdc++-cvs@gcc.gnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Libstdc++-cvs mailing list List-Unsubscribe: , List-Archive: List-Help: List-Subscribe: , X-List-Received-Date: Thu, 10 Mar 2022 14:25:57 -0000 https://gcc.gnu.org/g:73f3b8a53e6664c079731c2a183c16621481d039 commit r12-7597-g73f3b8a53e6664c079731c2a183c16621481d039 Author: Jonathan Wakely Date: Thu Mar 10 14:17:03 2022 +0000 libstdc++: Fix std::strong_order to handle NaN on VAX I mistakenly believed that VAX floats do not support NaN, but with GCC __builtin_isnan(__builtin_nan("")) is true. That means my previous change to is wrong, because it fails to handle NaN. When std::numeric_limits::is_iec559 is false, as on VAX, the standard only requires an ordering that is consistent with the ordering observed by comparison operators. With this change the ordering is -NaN < numbers < +NaN, and there is no support for different NaN bit patterns (as I'm not even sure if GCC supports any for VAX). libstdc++-v3/ChangeLog: * libsupc++/compare (_Strong_order::_S_fp_cmp) [__vax__]: Handle NaN. Diff: --- libstdc++-v3/libsupc++/compare | 12 ++++++++++-- 1 file changed, 10 insertions(+), 2 deletions(-) diff --git a/libstdc++-v3/libsupc++/compare b/libstdc++-v3/libsupc++/compare index 3c22d9addf1..6e1ed53eeed 100644 --- a/libstdc++-v3/libsupc++/compare +++ b/libstdc++-v3/libsupc++/compare @@ -844,8 +844,16 @@ namespace std _S_fp_cmp(_Tp __x, _Tp __y) noexcept { #ifdef __vax__ - // VAX format has no NaN, only "excess" for Inf, so totally ordered. - return __builtin_bit_cast(strong_ordering, __x <=> __y); + if (__builtin_isnan(__x) || __builtin_isnan(__y)) + { + int __ix = (bool) __builtin_isnan(__x); + int __iy = (bool) __builtin_isnan(__y); + __ix *= __builtin_signbit(__x) ? -1 : 1; + __iy *= __builtin_signbit(__y) ? -1 : 1; + return __ix <=> __iy; + } + else + return __builtin_bit_cast(strong_ordering, __x <=> __y); #endif auto __ix = _S_fp_bits(__x);