[cfe-dev] compiler-rt non-neon builds are still broken

[Jonathan Roelofs]

On 12/14/14 9:43 AM, Renato Golin wrote:
> On 14 December 2014 at 14:02, İsmail Dönmez <ismail at donmez.ws> wrote:
>> Scratch that, doesn't seem to work for my cross-build setup. But seems
>> to work on native ARM builder. Weird.
>
> Hi Ismail,
>
> @ is the comment character in ARM assembly, but not always recognised? Not sure.
>
> Anyway, we should not even try to unwind D16~D31 when you compile the
> library with VFPv3-D16. If we had push/pop for .cpu and .fpu for ARM,
> we could fix that one pretty quickly, but we don't.
That's an interesting point. Really we should split this function in two, so the 
demand-saving logic saves the high regs only when an EHT entry requests it. That 
way you can build an unwinder that will work on both VFPv3-D16 processors, and 
ones with D16~D31.
>
> My guess is that we should not be emitting that line at all, so
> replacing __ARM_FP by __ARM_NEON would be the right thing, and only
> emitting stcl when ARCH < 7 and vstmia otherwise.
>
> If that works, it'll depend on how you compile your library, and it'd
> be good to know how people do that and what do they expect to see. For
> instance, I don't expect to see that function be called at all when
> ARCH < 7 && !NEON.
It'd be nice if we could eliminate those preprocessor checks so you could link a 
-march=armv5t unwinder against an -mfpu=neon binary and have it work.

I added the original ones so I could build -march=armv4t, -march=thumbv4t, 
-march=thumbv6-m unwinders, because I couldn't figure out how to get the 
assembler shut up about unsupported coprocessor instructions. Is there a way to 
tell the assembler "yes, I really really know what I'm doing"? If so, that would 
be a much better solution than what we've got now.


Cheers,

Jon
>
> cheers,
> --renato
>
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-- 
Jon Roelofs
jonathan at codesourcery.com
CodeSourcery / Mentor Embedded