[LLVMdev] [RFC] Ideas on improving Compiler-RT CMake

[Chris Bieneman]

> On Jun 2, 2015, at 6:29 PM, Richard Smith <richard at metafoo.co.uk> wrote:
> 
> On 2 Jun 2015 2:04 pm, "Jonathan Roelofs" <jonathan at codesourcery.com <mailto:jonathan at codesourcery.com>> wrote:
> >
> >
> >
> > On 6/2/15 2:38 PM, Duncan P. N. Exon Smith wrote:
> >>
> >>
> >>> On 2015-Jun-01, at 19:47, Chris Bieneman <beanz at apple.com <mailto:beanz at apple.com>> wrote:
> >>>
> >>>> If we drop support for building compiler-rt with GCC, this gets even simpler. Compiler-rt is *Clang's* runtime library, after all.
> >>>
> >>>
> >>> I don’t know if it is on the table to drop supporting compiler-rt with GCC, but that would dramatically simplify things.
> >>
> >>
> >> Weird, I'd assumed building compiler-rt with something other than
> >> clang was unsupported.  Maybe I'm missing something, but shouldn't
> >> the only supported configuration be building with the just-built
> >> clang?
> >
> >
> > The current default for an in-tree build is to build compiler-rt with whatever compiler is being used to build Clang... sometimes that compiler is GCC.
> >
> > I agree though. We should always use the just-built Clang, and have that behavior be opt-out (if folks need it), instead of opt-in as it is now.
> 
> What would the build system do for a cross compile of Clang?
> 
This is the big question right? If we decide to only support building compiler-rt with the just-built clang that inherently means that you always have to build a clang that can run on host, so cross-compiling clang means building for host first, then the target.

I don’t think that is the behavior we want.

I suspect the behavior we probably want is to use the just-built clang by default unless you are cross-compiling, in which case use the host compiler.

Whether or not the host compiler needs to be clang, or any version restrictions we want to apply is a separate issue.

-Chris
> >
> > Jon
> >
> >
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> >>
> >
> > -- 
> > Jon Roelofs
> > jonathan at codesourcery.com <mailto:jonathan at codesourcery.com>
> > CodeSourcery / Mentor Embedded
> >
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