[LLVMdev] [PATCH] fix outs/ins of MOV16mr instruction (X86)

[Jun Koi]

On Wed, Mar 25, 2015 at 10:28 AM, Tim Northover <t.p.northover at gmail.com>
wrote:

> >> Why?  i16mem here stands for the pointer, not the actual memory.  A
> >> store doesn't define a pointer, so why would it be in "outs"?
> >
> > Then why does this "i16mem:$dst" belongs to "ins"? Is that wrong,
> correct?
>
> Think about a typical instruction:
>
>     movw %ax, 1234(%rax, 4, %rbx)
>
> The components making up the "i16mem" operand are "1234", %rax, 4 and
> %rbx (+ a hidden segment register). None of those are defined/written
> by the instruction (but they are read). So they need to be ins.
>
> What's written is some nebulous memory location specified by those
> operands. This isn't modelled by LLVM's basic instructions at all
> (except possibly via mayLoad and mayStore).
>

Got it, thanks!

A question: I still dont really understand why & how LLVM uses these "outs"
& "ins" information from each instruction.
Any hint, please?

Thanks,
Jun
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.llvm.org/pipermail/llvm-dev/attachments/20150402/754d0b55/attachment.html>