The llvm.hexagon.M2.mpyd.hh.s0 intrinsic; known as __builtin_HEXAGON_M2_mpyd_hh_s0 in GCC.
See Implementation
The llvm.hexagon.M2.mpyd.hh.s0 intrinsic; known as __builtin_HEXAGON_M2_mpyd_hh_s0 in GCC.