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Re: [Gold] how to do relax in Gold ?

On Tue, Jan 15, 2013 at 10:02 PM, Shawn <> wrote:
> Hi All:
>     I'am porting Gold to our processor right now ,everything is fine except
> the label whose value is big.  For Example, the following instruction assign
> a LABEL value to register R0:
>    ===========
>     R0 = LABEL_0;
>    ===========
> 1. Our Objects
>   Our instruction is encoded in 32bit,   if the value of "LABLE_0" is too
> big, for example 0x40000, there is not enough space to encode the
> instruction into a 32bit instruction, we have to expand "R0 = LABEL_0" into
> a 64bit instruction automatically.
>   Because the value of "LABEL_0" is not known until link-time, we hope
> "Gold" can handle this .
> 2. My plan  & Question:
>   I found the function related to our object is  the "Target::do_relax"
> function, but only & has overwritten it. The "do_relax" in
> & is too complicate to analyze. I hope to get a clean
> implementation of Our Objects.
>    a)  Scan  relocation info in all input objects, find the relocations that
> may  need relaxation ( read & compare the symbol value )
>          How can I read the relocation info ?
>          How can I reany advice ad the symbol  value ? Is the value read
> from the Symbol_table represent the value after layout ?
>    b)  for each relocation that  need relaxation, insert a 32bit stub in the
> VIEW, and update the value of the symbol which is located after the
> relocation site.
>     And is there any other example related to relaxation except &
> ? or any document ?

No, sorry.

I think one approach would be to record the possible relaxation points
in your scan_relocs routine.  You will have all the relocation
information available there.  That will let you detect out of range
relocations where you can insert stubs.


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