[LLVMdev] switching to llvm-g++ as the host compiler

[Evan Cheng]

Please make sure when we are running the llvm test suite the "native"  
executables are still built with gcc (or another compiler) unless it's  
explicitly specified to be llvm-gcc. Thanks.

Evan

On Jul 6, 2009, at 3:47 PM, Stuart Hastings wrote:

> IANACE (I Am Not A Configury Expert :-), but I've been asked to
> reconfigure LLVM and LLVM-GCC to build with LLVM-GCC (perhaps more
> accurately, LLVM-G++).
>
> The patches to do this are short.  In the LLVM tree, this suffices; it
> looks for LLVM-GCC first, and if that fails, falls back to GCC:
>
> Index: llvm.test/autoconf/configure.ac
> ===================================================================
> --- llvm.test/autoconf/configure.ac     (revision 74729)
> +++ llvm.test/autoconf/configure.ac     (working copy)
> @@ -601,8 +601,8 @@
>
>  dnl Check for compilation tools
>  AC_PROG_CPP
> -AC_PROG_CC(gcc)
> -AC_PROG_CXX(g++)
> +AC_PROG_CC([llvm-gcc gcc])
> +AC_PROG_CXX([llvm-g++ g++])
>
>  AC_PROG_NM
>  AC_SUBST(NM)
>
>
> Likewise, in our LLVM-GCC tree, this seems to work for Darwin/x86:
>
> Index: llvm-gcc.test/configure.in
> ===================================================================
> --- llvm-gcc.test/configure.in  (revision 74729)
> +++ llvm-gcc.test/configure.in  (working copy)
> @@ -993,10 +993,10 @@
>    # APPLE LOCAL begin dynamic-no-pic
>    i[[3456789]]86-*-darwin*)
>      host_makefile_frag="config/mh-x86-darwin"
> -    # gcc can default to x86_64 code generation, avoid that
> +    # llvm-gcc can default to x86_64 code generation, avoid that
>      if test "${build}" = "${host}"; then
> -      CC="${CC-gcc} -m32"
> -      CXX="${CXX-g++} -m32"
> +      CC="${CC-llvm-gcc} -m32"
> +      CXX="${CXX-llvm-g++} -m32"
>      fi
>      ;;
>    # APPLE LOCAL end dynamic-no-pic
>
>
> I've done some light testing of these, and I'm convinced they will
> work, at least for those of us on Darwin.  The latter patch is Darwin/
> x86-specific, and hopefully non-contentious.  I would hope the former
> patch wouldn't break anybody, but I thought I'd ask before applying  
> it.
>
> Of course, I'm omitting the diffs resulting from the re-auto-
> confiscation of both trees.  I was obliged to tweak all the version
> checks in the LLVM file AutoRegen.sh in order to get it to run :-),
> but no errors turned up after my hacking.  (Should AutoRegen.sh be
> updated too?)
>
> Comments invited; if there's a better approach, please share.
>
> stuart
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