Caching make

[Pete Johnson]

I am using make for IC design builds. Our tool flows typically involve 
dozens of different tools and compile chains of up to 20 steps. Much 
more complicated than the typical software flow. Some steps (like design 
synthesis) can take up to a day to run.

To avoid accidentally triggering a recompile that could last a day, we 
generally code the Makefile to allow dependencies to be switched in and 
out using a variable defined on the command line. This generally works 
well. However, for some targets which only require a few minutes to 
build, this is undesirable. Too much manual intervention is required to 
deal with this.

What would be useful is a cache. The idea is that targets could be saved 
along with a checksum of the dependency files. Future compile steps 
could be avoided by comparing the checksums of dependencies against 
previous builds and then just copying the cached target file if 
everything matched.

I have looked at CCache but this is C specific.

Does anyone have recommendations about how to set something like this up 
in GNU Make? Has this been done before?

Thanks,

-Pete