Getting DWARF codes from RTX

[Iyer, Balaji V]

Please see my comments embedded with "BVI>"

-----Original Message-----
From: Ian Lance Taylor [mailto:iant@google.com] 
Sent: Thursday, October 20, 2011 2:18 PM
To: Iyer, Balaji V
Cc: 'gcc@gcc.gnu.org'
Subject: Re: Getting DWARF codes from RTX

"Iyer, Balaji V" <balaji.v.iyer@intel.com> writes:

> 	What I want to do is to look at certain function calls and mark them 
> with a special label and then create a table  with a specialized 
> section with contains the label name, the function name (as ascii 
> string) and then the dwarf code of the register (assuming the 
> parameters can be passed in through registers, otherwise the stack 
> address location) in which the parameters for the function is stored. 
> (Please note that this is something that is customized for another 
> package and I don't have much leeway on how to store this information)
>
> Eg.
>
> If you have:   
> some_func_call (x, y, z)
>
> We will have an assembly like this
>
> 	Set R1, x
> 	Set R2, y
> 	Set R3, z
> LABEL_X:                        <=== SOMETHING I PUT IN
> 	Call some_func_call
>
>
> In my data section I would have something like this:
>
> LABEL_X
> some_func_call
> DW_OP_REG1, DW_OP_REG2, DW_OP_REG3

OK, I think I mostly understand all that.

> So, I need the equivalent dwarf code (in hex) for DW_OP_REG1, DW_OP_REG2 and DW_OP_REG3, so that a dwarf decoder can decode it correctly.

I'm not sure I understand that.  The code for DW_OP_reg1 is 0x51, as you can see in include/dwarf2.h.  But I don't think that is what you mean.

BVI> Actually what I want is to have a way to go from the rtx value e.g (REG: SI 1 di) to 0x51

It sounds like you might be asking for a way to get the DWARF representation of the argument locations of the function call.  See loc_descriptor in gcc/dwarf2out.c.

BVI> I will look into the loc descriptor. Thank you!

Ian

Thanks,

Balaji V. Iyer.