RISC-V: attributes and assembly / disassembly

[Kito Cheng]

A quick answer is that should be addressed by mapping symbol, but I am not
sure the current implementation status in binutils side, Nelson might be
able to answer this.

https://github.com/riscv-non-isa/riscv-elf-psabi-doc/pull/196

Jan Beulich via Binutils <binutils@sourceware.org> 於 2022年9月12日 週一 18:14 寫道：

> Hello,
>
> for use in other work I've been playing with this piece of assembly code
>
>         .option push
>         .option arch, +c
> aliasC:
>         sll     x1, x1, 3
>         c.slli  x1, 3
>         sra     x8, x8, 3
>         c.srai  x8, 3
>         srl     x8, x8, 3
>         c.srli  x8, 3
>         .option pop
>
> ending up quite surprised that the resulting object doesn't disassemble
> (at least not without giving the disassembler extra options). It then
> occurred to me to drop the push/pop of the options, and voila - things
> worked. Aiui riscv_write_out_attrs() populates Tag_RISCV_arch with the
> state of things at the end of assembly. Which raises (at least) two
> questions:
>
> 1) Shouldn't the assembler accumulate all extensions which were ever
> enabled in the course of processing the source, and use that set to
> populate Tag_RISCV_arch? Even if that's too simplistic, I don't think
> the state of things at the end of assembly can be taken as
> representative for the entire object.
>
> 2) The assembler properly sets the RVC bit in the ELF flags in the
> case described. Shouldn't the disassembler use that information
> alongside the attributes section?
>
> Thanks for any insight,
> Jan
>