[PATCH] gas: sframe: partially process DWARF expressions in CFI_escape

[Indu Bhagat]

On 1/29/25 9:11 AM, Jens Remus wrote:
> On 28.01.2025 01:57, Indu Bhagat wrote:
>> CFI_escape is most commonly used to include DWARF expressions in the
>> unwind information.  One may also use CFI_escape to add OS-specific CFI
>> opcodes.  Up until now, SFrame generation process would skip generating
>> SFrame FDE at the mere sight of a CFI_escape opcode.
>>
>> Fine tune the handling of CFI_escape for SFrame generation by explicitly
>> checking for some "harmless" (in context of SFrame generation)
>> CFI_escape DWARF expressions:
>>    - DW_CFA_expression affecting non SP/FP registers
>>    - DW_CFA_value_expression affecting non SP/FP registers.
> 
> Could that be extended to also process the CFI instructions already
> supported by SFrame, such as e.g. DW_CFA_val_offset through
> sframe_xlate_do_val_offset()?
> 

We could invoke sframe_xlate_do_val_offset (), we will just have to 
craft a new struct cfi_insn_data object just for checking the register...

What is the opinion on copying the necessary conditional into 
sframe_xlate_do_expr () for DW_CFA_val_offset ?

> On s390 Glibc for instance uses .cfi_escape to piece together
> .cfi_val_offset due to minimum binutils release requirements.
>