[PATCH] generate .init_array instead of .ctors sections for AArch64 ELF targets

[Rafael Espíndola]

On 9 January 2014 11:40, Kristof Beyls <kristof.beyls at arm.com> wrote:
> The .init_array should be used on any platform that follows the AArch64
> C++ ABI, which I think would be any platform using ELF as an object file
> format. I think that the patch does implement that (but this is an area
> of the code I'm not very familiar with).
>
> As for factoring out defaulting -fuse-init-array: the decision logic
> for Linux::addClangTargetOptions and Generic_GCC:addClangTargetOptions
> is different, so the only thing to factor out would be
> +  if (DriverArgs.hasFlag(options::OPT_fuse_init_array,
> +                         options::OPT_fno_use_init_array,
> +                         UseInitArrayDefault))
> +    CC1Args.push_back("-fuse-init-array");
> The conditions on when to add this by default would remain different
> between Generic_GCC and Linux, and therefore the 2 implementations of
> addClangTargetOptions in the Generic_GCC and Linux subclasses need to
> remain.
> Generic_GCC:
>   bool UseInitArrayDefault = getTriple().getArch() == llvm::Triple::aarch64;
>
> Linux:
>   const Generic_GCC::GCCVersion &V = GCCInstallation.getVersion();
>   bool UseInitArrayDefault =
>       !V.isOlderThan(4, 7, 0) ||
>       getTriple().getArch() == llvm::Triple::aarch64 ||
>       getTriple().getEnvironment() == llvm::Triple::Android;
>
> Or am I missing something obvious here?
> Is it worthwhile to factor out only the 4 lines that add the -fuse-init-array
> option into a separate function?

Yes. First, from your description you probably want to change
Generic_ELF instead of Generic_GCC. Second, Linux inherits from
Generic_ELF, so I think what you can do is:

remove Linux::addClangTargetOptions
add a Generic_ELF::addClangTargetOptions

Combine the logic you added with the one that is currently in the
linux toolchain. That is, UseInitArrayDefault would be

Arch == llvm::Triple::aarch64 || (OS == Linux && (!V.isOlderThan(4, 7,
0) || getTriple().getEnvironment() == llvm::Triple::Android))

Cheers,
Rafael