diff options
| author | Jonathan Wakely <jwakely@redhat.com> | 2022-03-10 14:17:03 +0000 |
|---|---|---|
| committer | Jonathan Wakely <jwakely@redhat.com> | 2022-03-10 14:25:46 +0000 |
| commit | 73f3b8a53e6664c079731c2a183c16621481d039 (patch) | |
| tree | 2699289256ab4cb281f0c9c534a3c1d0a8fb1713 | |
| parent | c65d3c7f9dade18826d1a28d71b98c7cdc3e4300 (diff) | |
| download | gcc-73f3b8a53e6664c079731c2a183c16621481d039.zip gcc-73f3b8a53e6664c079731c2a183c16621481d039.tar.gz gcc-73f3b8a53e6664c079731c2a183c16621481d039.tar.bz2 | |
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 <compare> is wrong, because it fails to handle NaN.
When std::numeric_limits<floating-point-type>::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.
| -rw-r--r-- | libstdc++-v3/libsupc++/compare | 12 |
1 files changed, 10 insertions, 2 deletions
diff --git a/libstdc++-v3/libsupc++/compare b/libstdc++-v3/libsupc++/compare index 3c22d9a..6e1ed53 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); |