feat(decode): implement shift instructions

Author: EmbroiderSnow

sim/src/decode.c

@@ -86,6 +86,9 @@ void decode_exec(Decode *s){
     INSTPAT("??????? ????? ????? 010 ????? 00100 11", slti   , I, R(rd) = (int64_t)src1 < (int64_t)imm);
     INSTPAT("??????? ????? ????? 011 ????? 00100 11", sltiu  , I, R(rd) = src1 < imm);
     // SLLI, SRLI, SRAI
+    INSTPAT("0000000 ????? ????? 001 ????? 00100 11", slli   , I, R(rd) = src1 << (imm & 0x3f));
+    INSTPAT("0000000 ????? ????? 101 ????? 00100 11", srli   , I, R(rd) = src1 >> (imm & 0x3f));
+    INSTPAT("0100000 ????? ????? 101 ????? 00100 11", srai   , I, R(rd) = (int64_t)src1 >> (imm & 0x3f));
     // XORI, ORI, ANDI
     // ADDIW
     // SLLI, SRLI, SRAI, SLLIW, SRLIW, SRAIW