When adding intrinsic in riscv，the command line option -target-feature fails to set the corresponding feature of subtarget to true, resulting in an error, so how to enable the feature correctly?

Beginners
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1

descreption：

Following ⚙ D99158 [RISCV] Implement intrinsics for P extension, I want to add an instruction in the P-like extension to riscv, but I have been stuck on failing to enable the corresponding feature

error：

./ztest.c:14:21: error: builtin requires at least one of the following extensions to be enabled: 'Zpn'
   14 |          unsigned int d =  __rv_add16(a, b);
      |                            ^~~~~~~~~~~~~~~~
1 error generated.

The version of llvm : 17.0

test program：

int main () {
	unsigned int a = 10;
	unsigned int b = 10;
	
	 unsigned int d =  __rv_add16(a, b);
	return 0;
}

The command to run:

../clang -cc1 -triple riscv32 -O2 -target-feature +experimental-zpn -emit-llvm ./ztest.c -o test.ll

The modifications I made are as follows:

llvm-project/clang/include/clang/Basic/BuiltinsRISCV.def

TARGET_BUILTIN(__rv_add16, "ULiULiULi", "nc", "experimental-zpn")

llvm-project/llvm/include/llvm/IR/IntrinsicsRISCV.td

let TargetPrefix = "riscv" in {
	class RVPBinaryIntrinsics
		  : Intrinsic<[llvm_any_ty],
					  [LLVMMatchType<0>, LLVMMatchType<0>],
					  [IntrNoMem]>;

	multiclass RVPBinaryIntrinsics {
		def "int_riscv_" # NAME : RVPBinaryIntrinsics;
	}

	defm add8     : RVPBinaryIntrinsics;
	defm add16    : RVPBinaryIntrinsics;
  defm kaddw    : RVPBinaryIntrinsics;
  defm ksubw    : RVPBinaryIntrinsics;
}

llvm-project/clang/lib/CodeGen/CGBuiltin.cpp

#define BUILTIN_ID(NAME)            \
 case RISCV::BI__rv_##NAME:         \
    ID = Intrinsic::riscv_##NAME;   \
    break;
// Intrinsic type is obtained from Ops[0].
  case RISCV::BI__rv_add8:
  case RISCV::BI__rv_add16:
  case RISCV::BI__rv_ksubw:
  case RISCV::BI__rv_kaddw: {
    switch (BuiltinID) {
      default : llvm_unreachable("unexpected builtin ID");
      BUILTIN_ID(add8)
      BUILTIN_ID(add16)
      BUILTIN_ID(kaddw)
      BUILTIN_ID(ksubw)
    }
#undef BUILTIN_ID
    IntrinsicTypes = {Ops[0]->getType()};
    break;
  }

llvm-project/llvm/lib/Target/RISCV/RISCVFeatures.td

def FeatureStdExtZpn
    : SubtargetFeature<"experimental-zpn", "HasStdExtZpn", "true",
                       "'Zpn' (Normal 'P' Instructions)">;
def HasStdExtZpn : Predicate<"Subtarget->hasStdExtZpn()">,
                             AssemblerPredicate<(all_of FeatureStdExtZpn),
                         "'Zpn' (Normal 'P' Instructions)">;

llvm-project/llvm/lib/Target/RISCV/RISCVInstrInfoP.td


//insturction def
let hasSideEffects = 0, mayLoad = 0, mayStore = 0 in
class RVPBinary<bits<7> funct7, bits<3> funct3, string opcodestr,
                DAGOperand rd_kind = GPR, DAGOperand rs1_kind = GPR,
                DAGOperand rs2_kind = GPR>
    : RVInstR<funct7, funct3, OPC_OP_P,
              (outs rd_kind:$rd), (ins rs1_kind:$rs1, rs2_kind:$rs2),
              opcodestr, "$rd, $rs1, $rs2">;

let Predicates = [HasStdExtZpn] in {
def ADD8     : RVPBinary<0b0100100, 0b000, "add8">,
               Sched<[]>;
def ADD16    : RVPBinary<0b0100000, 0b000, "add16">,
               Sched<[]>;
def KADDW    : RVPBinary<0b0000000, 0b001, "kaddw">,
               Sched<[]>;
def KSUBW    : RVPBinary<0b0000001, 0b001, "ksubw">,
               Sched<[]>;
}// Predicates = [HasStdExtZpn]



// match pattern 
class RVPBinaryIntPat<RVInst Inst, string IntID>
    : Pat<(XLenVT (!cast<Intrinsic>("int_riscv_" # IntID)
                   XLenVT:$rs1, XLenVT:$rs2)),
          (Inst GPR:$rs1, GPR:$rs2)>;

let Predicates = [HasStdExtZpn] in {
    def : RVPBinaryIntPat<ADD8,     "add8">;
    def : RVPBinaryIntPat<ADD16,    "add16">;
    def : RVPBinaryIntPat<KADDW,     "kaddw">;
    def : RVPBinaryIntPat<KSUBW,     "ksubw">;
}
2

OK,I solved it myself
RISCVISAInfo.cpp, Some content needs to be added, and there are some restrictions on the feature in the target-feature in the command line

3

You should post the specifics so others who hit the same error as you know what they got wrong.

4

The reason for the above error（When there is no problem with your def file, intrinsic, and feature definitions）

  • I think if you want to add custom features, especially with strange names, it is very likely that you need to modify part of the source code in ISAInfo
  • Please read the code in RISCVISAInfo.cpp carefully
  • my solution ： add legal features name in SupportedExtensions vector， so，I changed the name of the feature to ztao

def FeatureStdExtZtao
    : SubtargetFeature<"ztao", "HasStdExtZtao", "true",
                       "'Ztao' (Normal 'P' Instructions)">;
def HasStdExtZtao : Predicate<"Subtarget->hasStdExtZtao()">,
                             AssemblerPredicate<(all_of FeatureStdExtZtao),
                         "'Ztao' (Normal 'P' Instructions)">;
5

ok