[x264-devel] [PATCH] build: Generate dependency information as a side-effect of compilation

[Janne Grunau]

On 2014-05-03 16:30:31 +0200, Diego Biurrun wrote:
> This allows updating dependency information each time a file is changed,
> instead of creating dependency information once at the first build. In the
> latter case, dependency information is not updated each time a file is
> changed so that it can get out of date quickly.
> ---
> 
> This could still use some testing on ARM and ICL.

Works as expected for C sources on ARM, no change for assembler files.
Adding 'ASFLAGS="$ASFLAGS -MMD"' to the non MACOSX ARM section generates
dependency files as expected. The same doesn't work for darwin/macosx on arm 
due to gas-preprocessor.

>  .gitignore |  2 +-
>  Makefile   | 27 +++++++++++----------------
>  configure  |  8 ++------
>  3 files changed, 14 insertions(+), 23 deletions(-)

the change looks ok, I can't judge whether it's worth it. What is causing 
the slowdown? I'd guess including many small files in the Makefile and 
writing them during compilation. How large is the slowdown?

A full build is slightly faster on linux (cross-compiling with gcc for arm).
make in a fully build tree (i.e. only dependency checking) is 2-3 times 
slower but still takes less then 0.1s with hot fs caches.

Janne