[llvm-dev] Help adding entries to .symtab

[Liad Mordekoviz via llvm-dev]

Hey Paul,
first of all thank you for taking the time to answer me,
if I understand you correctly, I need to modify the instruction it self so
one of it's operands is a symbol, and then at MC layer handle that symbol
and add an entry to the symtab for that label?
What kind of symbol should I use doing such thing? external symbol or
MCSymbol?
I was trying to find where in the code during the MC layer I add entries to
the symtab, I'd really appreciate some directions in the area.

Let me give an example so my questions might be a bit more clearer:
BB#0
...some opcodes...
mov r1, BB#1

BB#1
...some opcodes...

I'd like to put a place holder instead of the BB#1 in the mov opcode, and
create a symbol named "BB#1" that points to that opcode, so during link
time I can replace that placeholder with the actual address of BB#1.

Again thank you for your time and answer,
Liad.

On Thu, Dec 14, 2017 at 9:03 PM, Robinson, Paul <paul.robinson at sony.com>
wrote:

> The .symtab has symbols; you could define a label for the instruction, and
> store something in the symbol table entry for the label.  This kind of
> thing would be done in the MC layer.
>
> This would be one way to provide annotations that aren't needed for
> execution.  If you need to change the instruction itself, for example to
> have the instruction refer to memory somewhere, then you need to modify the
> instruction itself.
>
> --paulr
>
>
>
> *From:* llvm-dev [mailto:llvm-dev-bounces at lists.llvm.org] *On Behalf Of *Liad
> Mordekoviz via llvm-dev
> *Sent:* Thursday, December 14, 2017 2:37 AM
> *To:* llvm-dev
> *Subject:* [llvm-dev] Help adding entries to .symtab
>
>
>
> Hi everyone,
>
>
>
> I am fairly new to LLVM, I'm working on a new backend.
>
> I am trying to add information to a specific instruction using the .symtab
> in the ELF format.
>
> I've been searching through the LLVM source code trying to find a way to
> do such a thing.
>
> Can anyone help me with some directions or point me to some documents in
> the matter.
>
>
>
> Thanks, Liad.
>
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