al63              125 src/dps8/dps8_math128.c     uint64_t al63 = a.l & MASK63;  // low 63 bits of a
al63              127 src/dps8/dps8_math128.c     uint64_t l63 = al63 + bl63;    // low 63 bits of a + b, with carry into bit 64