[llvm-dev] vector instruction

[Nemanja Ivanovic via llvm-dev]

I'm also not sure what you mean by "its size is a multiple of the operands
size". An instruction's (encoding) size has no correlation to the size of
the registers it operates on in a general sense.

So if you're looking for whether an IR instruction is a "vector
instruction" (i.e. it operates on or produces vectors), you should keep in
mind that every `llvm::Instruction` is an `llvm::Value` and you can get
it's type and check if it's a vector type with something like
`I.getType()->isVectorTy()`.

For MachineInstr's, I think you'd have to ensure that the operand you're
interested in is a register operand, get the register and check the
`MachineRegisterInfo::getRegClass()` for whether it's a vector register.

The reason I've put "vector instruction" in quotes is because that of
course doesn't have a clear definition. For example, is `extractelt` a
vector instruction? How about `insertelt`? What I'm getting at is if an
instruction has scalar inputs and vector outputs or vice-versa. Or if the
instruction has a mixture of vector and scalar operands (think of
loads/stores - address is likely in a scalar register or perhaps some kind
of arithmetic binary operator between a vector and a scalar).

On Tue, Aug 29, 2017 at 8:28 PM, Sam Elliott via llvm-dev <
llvm-dev at lists.llvm.org> wrote:

> This depends on what you mean by "instruction". More context would have
> been useful.
>
> LLVM IR is typed, and therefore you will see the operation applied to
> vector-typed arguments. For example `%3 = add i32 %1, %2` is the scalar
> version, `%3 = add <4 x i32> %1, %2` is the vectorised version (for a given
> IR vector type). The language reference [] has specifics on which
> instructions can operate on both vectors and scalars.
>
> I don't know anything about MIR.
>
> If you're looking at target-specific instructions (such as x86), you
> should look up the instruction documentation as provided by the
> manufacturer/ISA)
>
> Sam
>
> [] https://llvm.org/docs/LangRef.html
>
>
> On 29 Aug 2017, at 2:44 am, Anastasiya Ruzhanskaya via llvm-dev <
> llvm-dev at lists.llvm.org> wrote:
>
> Hello,
> is there a good way to determine that the instruction is a vector
> instruction? Or the only way like it's size is multiple of the operands
> size?
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>
> --
> Archibald Sam Elliott
> ashe2 at cs.washington.edu
> PhD Student, PLSE Group
>
>
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