[llvm-dev] [RISC-V]How to change the behavior of register allocation for RISC-V inline assembly

[Junning Wu via llvm-dev]

*The problem is, I have an instruction named LQP, which load 4x32-bit from
memory and store them into 4 consecutive GPRs, such as, LQP a0, a4, a5, 4,*
* the loaded data will be stored in (a3,a2,a1,a0), the data address is
4(a4+a5).*

*The RISC-V inline assembly like this:*

  asm volatile
  (
    "lqp   %[z], %[x], %[y], 4\n\t"
    : [z] "=r" (c)
    : [x] "r" (a), [y] "r" (b)
  ) ;

*To get this done, I creat to GPR groups and change the LQP instruction's
definition, like this:*

def GPRA0 : RegisterClass<"RISCV", [XLenVT], 32, (add X10)> {
  let RegInfos = RegInfoByHwMode<
      [RV32,              RV64,              DefaultMode],
      [RegInfo<32,32,32>, RegInfo<64,64,64>, RegInfo<32,32,32>]>;
}

def GPRNOA0A1A2A3 : RegisterClass<"RISCV", [XLenVT], 32, (add
    (sequence "X%u", 14, 17),
    (sequence "X%u", 5, 7),
    (sequence "X%u", 28, 31),
    (sequence "X%u", 8, 9),
    (sequence "X%u", 18, 27),
    (sequence "X%u", 0, 4)
  )> {
  let RegInfos = RegInfoByHwMode<
      [RV32,              RV64,              DefaultMode],
      [RegInfo<32,32,32>, RegInfo<64,64,64>, RegInfo<32,32,32>]>;
}

let hasSideEffects = 0, mayLoad = 1, mayStore = 0 in
def LQP : RVInstRI<0b11, 0b000, OPC_HX_CUS0,
                  (outs GPRA0:$rd), (ins GPRNOA0A1A2A3:$rs1,
GPRNOA0A1A2A3:$rs2, simm5:$shift),
                  "lqp", "$rd, $rs1, $rs2, $shift">, Sched<[]> {
 bits<5> shift;
 bits<5> rs1;
 bits<5> rs2;
 bits<5> rd;

 let Inst{31-30} = 0b11;
 let Inst{29-25} = shift;
 let Inst{24-20} = rs2;
 let Inst{19-15} = rs1;
 let Inst{14-12} = 0b000;
 let Inst{11-7} = rd;
 let Opcode = OPC_HX_CUS0.Value;
}

*and the  DecodeStatus as well, *

static DecodeStatus DecodeGPRA0RegisterClass(MCInst &Inst, uint64_t RegNo,
                                               uint64_t Address,
                                               const void *Decoder) {
  if (RegNo != 10) {
    return MCDisassembler::Fail;
  }

  return DecodeGPRRegisterClass(Inst, RegNo, Address, Decoder);
}

static DecodeStatus DecodeGPRNOA0A1A2A3RegisterClass(MCInst &Inst, uint64_t
RegNo,
                                               uint64_t Address,
                                               const void *Decoder) {
  if (RegNo == 10 || RegNo == 11 || RegNo == 12 || RegNo == 13) {
    return MCDisassembler::Fail;
  }

  return DecodeGPRRegisterClass(Inst, RegNo, Address, Decoder);
}

static DecodeStatus DecodeGPRNOA0A1RegisterClass(MCInst &Inst, uint64_t
RegNo,
                                               uint64_t Address,
                                               const void *Decoder) {
  if (RegNo == 10 || RegNo == 11) {
    return MCDisassembler::Fail;
  }

  return DecodeGPRRegisterClass(Inst, RegNo, Address, Decoder);
}

*Rebuild LLVM+clang, and compile the above c code which got such an error:*

clang -I./env -I./common -I./src/test_newinst
-I/home/llvm/workspace/llvm/llvm-project/llvm_install/riscv32-unknown-elf/include
-mcmodel=medany -static -std=gnu99 -fno-common -fno-builtin-printf
-march=rv32imac -mabi=ilp32 -DMB_ADDR=0x11ffC -O3
--target=riscv32-unknown-elf
--sysroot=/home/llvm/workspace/riscv/riscv-tc-20200316/bin/riscv32-unknown-elf
--gcc-toolchain=/home/llvm/workspace/riscv/riscv-tc-20200316 -o
./build/test_newinst/test_newinst ./src/test_newinst/main.c
./common/syscalls.c ./common/dev.c ./common/crt.S -static  -nostartfiles
-lm -lgcc -T ./common/test.ld

./src/test_newinst/main.c:117:5: error: invalid operand for instruction
    "lqp   %[z], %[x], %[y], 4\n\t"
    ^

<inline asm>:1:8: note: instantiated into assembly here
        lqp   a2, a0, a1, 4

*This error is obvious, and due to the Match_InvalidOperand, I wonder why
the changes do not make any effect for LQP instruction.*
*And I have checked the OperandInfo111[] and RISCVInsts[] for the LQP
instruction, *

static const MCOperandInfo OperandInfo111[] = { { RISCV::GPRA0RegClassID,
0, MCOI::OPERAND_REGISTER, 0 }, { RISCV::GPRNOA0A1A2A3RegClassID, 0,
MCOI::OPERAND_REGISTER, 0 }, { RISCV::GPRNOA0A1A2A3RegClassID, 0,
MCOI::OPERAND_REGISTER, 0 }, { -1, 0, RISCVOp::OPERAND_SIMM5, 0 }, };

{ 457, 4, 1, 4, 0, 0|(1ULL<<MCID::MayLoad), 0x12ULL, nullptr, nullptr,
OperandInfo111, -1 ,nullptr },  // Inst #457 = LQP

*Do I miss something or what I can do in this situation?*
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.llvm.org/pipermail/llvm-dev/attachments/20200407/0746669a/attachment.html>