[LLVMdev] Deprecating autoconf/make?

Greg Fitzgerald garious at gmail.com
Thu May 23 15:28:16 PDT 2013

Hi Jim,

> Perhaps I’m misunderstanding you. Are you suggesting
> using QEMU as part of the LLVM build process?

Just for the case of building the runtime libraries for a cross-compiled
version of clang.

Another option is to have the compiler-rt build depend on a host build of
clang.  So when cross-compiling clang, we'd generate two clang builds: a
target version to ship, and a throwaway host version that only exists to
cross-compile compiler-rt.

I think this second option is the more elegant one (less source
dependencies), but is it possible in a single CMake build?  The QEMU
solution entertains the idea of pushing forward with just one
cross-compiler and putting all projects in one big [parallel] build.  But
if the QEMU dependency is too impractical, then compiler-rt requires a
pre-built host cross-compiler.  If no one takes issue with that, is it safe
to just ignore the compiler-rt build in "autotools vs CMake" debate?  It
means we'll need a build to invoke the two builds.  Should we write that in
Make or CMake? :)


On Thu, May 23, 2013 at 1:51 PM, Jim Grosbach <grosbach at apple.com> wrote:

> On May 23, 2013, at 10:30 AM, Greg Fitzgerald <garious at gmail.com> wrote:
> On Thu, May 23, 2013 at 6:01 AM, Jean-Daniel Dupas <devlists at shadowlab.org
> > wrote:
>> If you want to build a clang version that target x86 and ARM on an x86
>> machine and your actual compiler does not support compiling for ARM, you
>> have to use the just built clang.
> Using the just-built-clang will only work if compiler-rt has access to
> each target's sysroot.  Compiler-rt attempts to do this by stubbing out
> sysroots (see the SDKs directory), but I wonder how well that'll work.
>  There's only one ARM backend, for example, but multiple ARM targets (i.e.
> arm-none-linux-gnueabi, arm-linux-androideabi).  Does there need to be a
> separate compiler-rt for each target triple or can we get by with one per
> architecture?  It feels like it has to be one per target triple, but it
> doesn't look to be implemented that way.  I'm new to compiler-rt, but is it
> possible that its CMake and autotools builds are both broken for everything
> but the host target?
> Of course, if you are building a clang version that have to run on an
>> other target, you should use you current compiler.
> We don't need a special case for this.  You can run the just-built-clang
> on an emulator such as QEMU.
> Perhaps I’m misunderstanding you. Are you suggesting using QEMU as part of
> the LLVM build process?
> -Greg
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