llvm dev - Dec 2013 - [LLVMdev] Integrated 'as' for PowerPC by default?

Hi PPC folks,

as of v3.3 the integrated assembler seems to work fine.
But it is not on by default. What is the obstacle for this last step?

Just curious,

    Gabor

Gabor Greif <ggreif at gmail.com> wrote:
> as of v3.3 the integrated assembler seems to work fine.
> But it is not on by default. What is the obstacle for this last step?
Well, it's support is not complete ...  The integrated assembler
supports all general-purpose instructions the compiler itself
generates, but has only partial support for all the rest, in
particular nearly no support for any supervisor mode instructions.

This means that if you use inline asm to generate any of
those instructions (in particular in kernel code or other
code that runs in supervisor mode), this would fail when
using the internal assembler.

Bye,
Ulrich

Hi Ulrich!

Thanks for your answer.

On 12/5/13, Ulrich Weigand <Ulrich.Weigand at de.ibm.com>
wrote:
> Gabor Greif <ggreif at gmail.com> wrote:
>
>> as of v3.3 the integrated assembler seems to work fine.
>> But it is not on by default. What is the obstacle for this last step?
>
> Well, it's support is not complete ...  The integrated assembler
> supports all general-purpose instructions the compiler itself
> generates, but has only partial support for all the rest, in
> particular nearly no support for any supervisor mode instructions.
I see.
>
> This means that if you use inline asm to generate any of
> those instructions (in particular in kernel code or other
> code that runs in supervisor mode), this would fail when
> using the internal assembler.
So '-integrated-as' has not been enabled by default because
clang is not yet a drop-in replacement for 'gcc' in this mode.

Thanks for the clarification.

Cheers,

   Gabor
>
> Bye,
> Ulrich
>
>

On Thu, Dec 05, 2013 at 01:31:03PM +0100, Ulrich Weigand
wrote:
> Gabor Greif <ggreif at gmail.com> wrote:
> 
> > as of v3.3 the integrated assembler seems to work fine.
> > But it is not on by default. What is the obstacle for this last step?
> 
> Well, it's support is not complete ...  The integrated assembler
> supports all general-purpose instructions the compiler itself
> generates, but has only partial support for all the rest, in
> particular nearly no support for any supervisor mode instructions.
> 
> This means that if you use inline asm to generate any of
> those instructions (in particular in kernel code or other
> code that runs in supervisor mode), this would fail when
> using the internal assembler.
I'm not sure that's a strong enough reason. From my experience, at least
for PPC32 it is already less problematic to use the integrated assembler
for ELF.

Joerg