[committed] libstdc++: Support VAX floats in std::strong_order

[Jonathan Wakely]

Tested x86_64-linux, and basic soundness check on vax-dec-netbsdelf.

Pushed to trunk.

-- >8 --

The VAX float and double format does not support NaN, so the
std::partial_ordering returned by <=> will never be 'unordered'. We can
just use the partial_ordering value as the strong_ordering.

libstdc++-v3/ChangeLog:

	* libsupc++/compare (_Strong_ordering::_S_fp_cmp) [__vax__]: Use
	<=> comparison.
---
 libstdc++-v3/libsupc++/compare | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/libstdc++-v3/libsupc++/compare b/libstdc++-v3/libsupc++/compare
index 050cf7ed20d..3c22d9addf1 100644
--- a/libstdc++-v3/libsupc++/compare
+++ b/libstdc++-v3/libsupc++/compare
@@ -843,6 +843,11 @@ namespace std
 	static constexpr strong_ordering
 	_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);
+#endif
+
 	  auto __ix = _S_fp_bits(__x);
 	  auto __iy = _S_fp_bits(__y);
 
-- 
2.34.1