[llvm-dev] how to add a instruction

[Tianhao Shen via llvm-dev]

Hi,every one.
I' in trouble again.
I want add a new intrinsic mapping a new instruction.


I add the int_x86_max_qb as fllowing:
def int_x86_max_qb: GCCBuiltin<"__builtin_x86_max_qb">, Intrinsic<[llvm_i32_ty], [llvm_i32_ty, llvm_i32_ty], [Commutative]>;


BUILTIN(__builtin_x86_max_qb, "iii", "") 


I define the intrinsic as Pseudo instruction,it succeed.


But when mapping a new instruction.I don't know how to do.
In x86InstrArithmetic.td. I add ,(To make sure the Sched is right, I use the WriteIMul16Reg )
def max_qb : I<0xF0,MRMSrcReg, (outs  GR32:$dst), (ins GR32:$src1,GR32:$src2), "max_qb\t {$dst, $src1,$src2}", [(set GR32:$dst,(X86max_qb GR32:$src1, GR32:$src2))]>,Sched<[WriteIMul16Reg]>,OpSize32 ;
when compile LLVM , the error appears.
"[ 97%] Updating X86GenAsmWriter1.inc...   
Unhandled immediate encoding GR32
Unhandled immediate encoding
"


But when I write the same as the instruction IMUL32rr, there is no error in compiling.(I don't use the EFLAGS at all, so I think it's wrong. Indeed, it made a error when using it.)
let Defs = [EFLAGS] in {
let Constraints = "$src1 = $dst" in {
let isCommutable = 1 in {
def max_qb : I<0xF0,MRMSrcReg, (outs  GR32:$dst), (ins GR32:$src1,GR32:$src2), "max_qb\t {$dst, $src1,$src2}", [(set GR32:$dst,(X86max_qb GR32:$src1, GR32:$src2))]>,Sched<[WriteIMul16Reg]>,OpSize32 ;
}
}


What I don't understand is that how I define "let   in  ".
Thanks,
Tianhao Shen.



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