Support for below instruction is added 1. CFLUSH.D.L1 2. CDISCARD.D.L1 3. CEASE Additionally, Zihintpause extension is added to sifive s76 for pause instruction. Spec - https://sifive.cdn.prismic.io/sifive/767804da-53b2-4893-97d5-b7c030ae0a94_s76mc_core_complex_manual_21G3.pdf Reviewed By: craig.topper Differential Revision: https://reviews.llvm.org/D153370