[PATCH 2/3] RISC-V: correct alignment directive handling for text sections

[Jan Beulich]

On 04.09.2024 01:02, Palmer Dabbelt wrote:
> On Mon, 12 Aug 2024 08:08:04 PDT (-0700), jbeulich@suse.com wrote:
>> .insn or data emitted inside text sections can lead to positions not
>> being at insn granularity. In such situations using alignment
>> directives should reliably enforce the requested alignment.
>> Specifically requests to align back to insn granularity may not be
>> ignored (where, as a subcase thereof, the ordering of ".option norvc"
>> and e.g. ".p2align 2" should not matter; so far the alignment directive
>> needs to come first to have any effect). Similarly ahead of emitting
>> NOPs alignment first needs to be forced back to insn granularity.
>>
>> The new testcases actually point out a corner case issue in the
>> disassembler as well, which is being corrected at the same time: We
>> don't want to print "0x" without any subsequent digits.
> 
> Sorry for being slow here.  Nelson and I talked about this a few times.  
> IIRC a bunch of the complexity in the code was related to trying to 
> avoid mixing RVC instructions into non-RVC regions in order to re-gain 
> alignment.  I remember there being some reason that we didn't want to 
> emit instructions when changing rvc->norvc, but I can't remember what 
> that reason was.  So maybe I'm just crazy here...
> 
> Jim might remember?  IIRC he was at least sitting there talking about 
> this stuff as it was getting fixed, I forget if he wrote the code.
> 
> That said, I think you just found another bug: certainly ignoring the 
> alignment directive is going to break things, so that's bad.  I don't 
> see anything wrong with the actual code here, though...
> 
> So Nelson is going to run some regressions and see what's up.  If they 
> all pass and nobody can remember a reason this wouldn't work, then I 
> think we just go with it.

Mind me asking if there has been any progress here?

Jan