add support for m68k 80-bit long double variant

since x86 and m68k are the only archs with 80-bit long double and each
has mandatory endianness, select the variant via endianness.
differences are minor: apparently just byte order and representation
of infinities. the m68k format is not well-documented anywhere I could
find, so if other differences are found they may require additional
changes later.

1 files changed, 11 insertions, 0 deletions

diff --git a/src/internal/libm.h b/src/internal/libm.h
index df864111..a2505f7e 100644
--- a/src/internal/libm.h
+++ b/src/internal/libm.h
@@ -28,6 +28,17 @@ union ldshape {
 		uint16_t se;
 	} i;
 };
+#elif LDBL_MANT_DIG == 64 && LDBL_MAX_EXP == 16384 && __BYTE_ORDER == __BIG_ENDIAN
+/* This is the m68k variant of 80-bit long double, and this definition only works
+ * on archs where the alignment requirement of uint64_t is <= 4. */
+union ldshape {
+	long double f;
+	struct {
+		uint16_t se;
+		uint16_t pad;
+		uint64_t m;
+	} i;
+};
 #elif LDBL_MANT_DIG == 113 && LDBL_MAX_EXP == 16384 && __BYTE_ORDER == __LITTLE_ENDIAN
 union ldshape {
 	long double f;