[LLVMdev] Machine Code for different architectures

[Johnny Val]

Hi Matthew,

The byte==8 bits is more of a Clang issue rather than an LLVM issue. I
believe your bigger issue will be the fact that you would need to make
i24's a legal type in your backend, which as far as I know (unless
something has changed recently), is a _big_ job. I briefly looked into it
at one point, and decided to leave it for another day.

I am also unsure how hard byte=8bits is backed into Clang. You might want
to ask cfe-dev.

I hope that helps.

Johnny

On Tue, Sep 9, 2014 at 7:41 AM, Matthew Gardiner <mg11 at csr.com> wrote:

> Hi,
>
> We have some DSP architectures (kalimba) which have 24-bits as their
> "minimum addressable unit". So this means that the sizeof a char (and
> an int and a short for that matter) is 24-bits.
>
> I quickly read the posted link WritingAnLLVMBackend.html but did not
> see an obvious answer to the following question:
>
> Is it possible to write a backend that faithfully represents these
> architectures or is sizeof_byte==8 bits baked into to llvm?
>
> Does anyone have any views on the above?
>
> thanks
> Matthew Gardiner
>
>
> On Tue, 9 Sep 2014 18:21:01 +1200
> Bruce Hoult <bruce at hoult.org> wrote:
>
> > http://llvm.org/docs/WritingAnLLVMBackend.html
> >
> >
> > On Tue, Sep 9, 2014 at 6:09 PM, Prakash Premkumar
> > <prakash.prax at gmail.com> wrote:
> >
> > > How does LLVM generate machine code for different architectures?
> > > For example, the machine code for x86 and amd will vary.
> > >
> > > How does LLVM convert its IR to machine code for different
> > > architectures.Can you please explain the approach? Is it just write
> > > two different programs for two different architectures and pass a
> > > flag to the compiler based on which machine code you want to
> > > generate?
> > >
> > > Thanks a lot for your explanations.
> > >
> > > Thanks
> > > Prakash
> > >
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