Useful Commands

Emit LLVM IR

> clang -S -emit-llvm file.c -o file.bc

produces file.bc with textual LLVM IR.

-S like in gcc says emit textual assembly rather than assembled binary

if -o file.bc is omitted, it will generate file.ll.

Compile LLVM IR to assembly

> llc file.bc

produces file.s with assembly (defaulting to machine architecture the command is run on). LLC docs are available here.

Run LLVM bitcode direclty

lli file.bc

executes the program in file.bc (it can be textual or binary bitcode). LLI docs are available here.

ELLCC (Online experimentation)

All of the above can be done on local llvm installation as well. But it might help to experiment online at ELLCC: http://ellcc.org/demo/index.cgi

Pass

A pass needs a Makefile and a .exports file (don't know why it needs an .exports file.)

Build Pass

Run

> gmake

from inside the pass directory.

Test Pass

Run

> opt -S -load ../../../Debug+Asserts/lib/<pass_name>.so -<pass_command_line_argument> < <input_bc_file> > <output_bc_file>

-S is to ensure any output is generate as textural IR.

More information is available in Writing a Hello World Pass.

Issues:

• Difficulty finding header files (e.g. I had to spend a good 15 minutes on finding llvm/Intrinsic.h)
• Isn't there a getOrInsertGlobalVariable function?

OCCAM INSTALL NOTES:

• export OCCAM_SRC=pwd/OCCAM is actually export OCCAM_SRC=pwd
• even if adding all the variables to .profile, 'export ' needs to precede the variable
• add export LD_LIBRARY_PATH=/usr/local/lib:${LD_LIBRARY_PATH}