The llvm.hexagon.M2.mpyd.acc.ll.s1 intrinsic; known as __builtin_HEXAGON_M2_mpyd_acc_ll_s1 in GCC.
See Implementation
The llvm.hexagon.M2.mpyd.acc.ll.s1 intrinsic; known as __builtin_HEXAGON_M2_mpyd_acc_ll_s1 in GCC.