[llvm-dev] Issues in Vector Add Instruction Machine Code Emission

[Craig Topper via llvm-dev]

Does your ADD instruction have VEX_4V or EVEX_4V as part of its declaration
in the td file?

~Craig

On Mon, Sep 4, 2017 at 2:11 PM, hameeza ahmed <hahmed2305 at gmail.com> wrote:

> Hello,
> I am trying to emit binary for my implemented vector instructions.
> Although yet i havent done any change or addition in MC framework, For
> vector load instruction there are no error coming. But for vector add
>
> instruction is something like this;
>
> > %R_0_REG2048b_1<def> = P_256B_VADD %R_0_REG2048b_1<kill>,
> %R_0_REG2048b_0<kill>
>
> I am getting the following error:
>
> Unknown immediate size
> UNREACHABLE executed at /lib/Target/X86/MCTargetDesc/X86BaseInfo.h:574!
>
>
>  i made  extensive use of gdb and after debugging i found the line with
> issue in X86MCCodeEmitter.cpp.
>
> Here NumOps=3 (all registers). and CurOp is 1st initialized to 0.
>
> then, the following code gets executed;
>
> case X86II::MRMDestReg: {
>     EmitByte(BaseOpcode, CurByte, OS);
>     unsigned SrcRegNum = CurOp + 1; //SrcRegNum=1
> EmitRegModRMByte(MI.getOperand(CurOp),
>                      GetX86RegNum(MI.getOperand(SrcRegNum)), CurByte, OS);
>     CurOp = SrcRegNum + 1;
>     break;
>   }
> so here CurOp becomes 2.
>
> After this;
>
> it comes to;
> else {
>     // If there is a remaining operand, it must be a trailing immediate.
> Emit it
>     // according to the right size for the instruction. Some instructions
>     // (SSE4a extrq and insertq) have two trailing immediates.
>     while (CurOp != NumOps && NumOps - CurOp <= 2) {
>       EmitImmediate(MI.getOperand(CurOp++), MI.getLoc(),
>                     X86II::getSizeOfImm(TSFlags), getImmFixupKind(TSFlags),
>                     CurByte, OS, Fixups);
>     }
>
> here CurOp=2 !=NumOps=3 && 3-2<=2
> so while condition is satisfied and it goes to emitimmediate which is
> wrong and there prints error message.
>
> Since, there are no immediate involved in instruction, it should not go to
> emitimmediate. How to solve this issue?
>
> Please help.
>
> Thank You
>
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