[llvm-dev] Immediate operand for vector instructions

[Alex Susu via llvm-dev]

   Hello.
     I have problems specifying vector instructions with immediate values in TableGen.

     I wrote the following specification (I got inspired from the MSA vector instructions 
for the Mips back end):
         class MSA_I16_FMT<bits<9> opcode>: MSAInst {
           bits<16> s16;
           let Inst{31-23} = opcode;
           let Inst{26-11} = s16;
         }
         class REP_1R_DESC_BASE<,
                                     InstrItinClass itin = NoItinerary> {
           dag OutOperandList = (outs);
           /* From include/llvm/Target/Target.td:
              let OperandType = "OPERAND_IMMEDIATE" in {
                ...
              def i64imm : Operand<i64>; */
           dag InOperandList = (ins i64imm:$imm);

           string AsmString = "REPEAT_X_TIMES($imm";
           list<dag> Pattern = [(int_repeat_x_times i64imm:$imm)];
           InstrItinClass Itinerary = itin;
         }
         class REP_D_DESC : REP_1R_DESC_BASE;
         class REP_D_ENC :  MSA_I16_FMT<0b101010111>;
         def REP_D: REP_D_ENC, REP_D_DESC;

     and added in the LLVM program (programmatically, in an LLVM pass) an LLVM IR 
repeat_x_times intrinsic.
     To my big surprise (because of the property OperandType = "OPERAND_IMMEDIATE"), the 
resulting ASM codegen'ed by the instruction selector contains a mov and use a register:
         mov     r1, 32767               // <MCInst #75 MOV_ri
                                         //  <MCOperand Reg:2>
                                         //  <MCOperand Imm:32767>>
         REPEAT_X_TIMES(r1);
         ...


     Note that in the end I managed to fix this problem by using an address operand as 
immediate operand (inspired again from Mips MSA vector instructions), but I consider this 
a somewhat strange solution:
         class REP_1R_DESC_BASE<Operand MemOpnd = uimm4_ptr,
                                 ImmLeaf Addr = immLeaf,
                                 InstrItinClass itin = NoItinerary> {
           dag OutOperandList = (outs);
           dag InOperandList = (ins MemOpnd:$addrdst);

           string AsmString = "REPEAT_X_TIMES($addrdst );";
           list<dag> Pattern = [(int_connex_repeat_x_times Addr:$addrdst)];
           InstrItinClass Itinerary = itin;
         }



     So, is there are way to use immediate values that are not memory operands?


   Thank you ,
     Alex