[LLVMdev] Load MachineFunctionPass plugin from library in llc?

[Ethan J. Johnson]

Hi all,

 

I am working on creating a MachineFunctionPass to perform an analysis on X86
code. After a bit of trouble, I was able to get my pass compiling and
running correctly in llc. However, since a machine pass is compiled directly
into the code generator, rerunning "make" across the LLVM build tree
involves re-linking most of the major libraries and executables. This is a
rather intense process, both in terms of CPU usage and memory (some of the
bigger binaries, especially clang, use as much as 5 GB peak memory during
linking). With a powerful multicore machine and plenty of RAM, this is
doable, but still very time-consuming, and seems wastefully repetitive.

 

For a front-end pass, I can load the pass from a dynamic shared library
using "opt -l path_to_library"; thus I only need to rebuild the pass itself
to test a code change. There does not appear to be such an option in llc for
dynamically linking a machine pass as a plugin. Does anyone know of a way to
achieve something similar?

 

At the very least, it would be nice to be able to just re-compile the parts
of the LLVM tree I need (perhaps just llc). It seems particularly odd that
clang, which is a front-end, would need to be relinked for a code change in
a back-end pass. (clang, and some of its related components, are responsible
for the lion's share of the time-consuming CPU/memory-intensive linking
phase.)

 

FYI, I am using the Autotools (./configure, make) process to build LLVM, but
have also successfully built with CMake and would be willing to try
suggestions involving either.

 

Any advice/suggestions would be greatly appreciated!

 

Thanks,

Ethan Johnson

 

Ethan J. Johnson

Computer Science PhD student, Systems group, University of Rochester

 <mailto:ejohns48 at cs.rochester.edu> ejohns48 at cs.rochester.edu

 <mailto:ethanjohnson at acm.org> ethanjohnson at acm.org

PGP pubkey available from public directory or on request

 

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