Implement getMemScale/getOffsetScale using MCInst flags coming from tablegen.

There are well over 1000 load and store opcodes. It is near impossible to maintain them all
by hand in a switch statement.

Author: kbeyls

bolt/lib/Target/AArch64/AArch64MCPlusBuilder.cpp

@@ -309,7 +309,7 @@ class AArch64MCPlusBuilder : public MCPlusBuilder {
       if (OffsetOpIdx == -1 || !Inst.getOperand(OffsetOpIdx).isImm())
         return Res;
       int64_t Offset = Inst.getOperand(OffsetOpIdx).getImm() *
-                       AArch64InstrInfo::getMemScale(Opc);
+                       AArch64MCInstrInfo::getOffsetScale(*Info, Opc);
       Res.IsPreIndexOffsetChange = AArch64MCInstrInfo::isPreLdStOpcode(*Info, Opc);
       Res.FromReg = Res.ToReg = Inst.getOperand(BaseOpIdx).getReg();
       Res.MaxOffsetChange = Res.OffsetChange = Offset;
@@ -394,7 +394,7 @@ class AArch64MCPlusBuilder : public MCPlusBuilder {
     if (OffsetOpIdx == -1 || !Inst.getOperand(OffsetOpIdx).isImm())
       return false;
     int64_t Offset = Inst.getOperand(OffsetOpIdx).getImm() *
-                     AArch64InstrInfo::getMemScale(Opc);
+                     AArch64MCInstrInfo::getOffsetScale(*Info, Opc);
     if (AArch64MCInstrInfo::isPostLdStOpcode(*Info, Opc))
       StackOffset = 0;
     else