[cfe-dev] Integrating "-distribute" into clang's Driver

[Eli Friedman]

On Thu, May 13, 2010 at 4:27 PM, Mike Miller <michael.g.miller at gmail.com> wrote:
> Hi cfe-dev,
>
> I've added an option to -cc1: -distribute. The option takes as input a
> single source file, and produces object code, by distributing the
> source to slaves. I'm now trying to make '-distribute' a
> non-cc1-option as well, so that a user can use -distribute in their
> CFLAGS to get projects to build in a distributed manner without much
> hassle. I have several questions regarding this:
>
> 1. Since I'm skipping the assembler(I'm doing assembly on slaves), but
> still going on to the linker, I'm confused about how to integrate the
> -distribute option into the Action pipeline in Driver.cpp. What's the
> best way to do this? I'd like to be able to smartly handle a user
> typing "clang -distribute -E  myFile.c" by not invoking -distribute in
> -cc1 if no object code is required.

The -integrated-as option is pretty similar to what you need; try
taking a look at how that is implemented?  As for -E, you can check
explicitly in Clang::ConstructJob in lib/Driver/Tools.cpp.

> 2. Since I'm skipping the assembler, I need to know where to save the
> object code to on disk. Is there an easy way to get clang to pass -cc1
> the expected location of the object file, so that the linker will be
> able to find the object file?

See above.

> 3. Is there any way (or does clang already) invoke multiple -cc1s in
> parallel where possible? If not, would this be easy to add in? When
> called with -distribute, clang will just connect via a UNIX socket to
> another process, send over the source+args, and receive the diags, and
> the object file will be written out to disk by the process at the
> other end of the socket, so I'm not worried about thread safety at
> all.

It probably wouldn't be that difficult to implement; the driver
already invokes separate -cc1 instances when it is passed multiple
files.  That said, majority of popular build systems don't call the
compiler in this way, so it isn't very high priority.

-Eli