This top-level module exports the LLVM IR definitions and some basic functions to inspect the IR. The sub-modules under LLVM.Analysis provide higher-level tools for analyzing the IR.

The functions to parse LLVM Bitcode into a Haskell ADT are in the llvm-data-interop package (in the LLVM.Parse module). The first is parseLLVMFile:

 import LLVM.Parse
 main = do
   m <- parseLLVMFile defaultParserOptions filePath
   either error analyzeModule

 analyzeModule :: Module -> IO ()

The defaultParserOptions direct the parser to keep all metadata. This behavior can be changed to discard the location metadata normally attached to each instruction, saving a great deal of space. Metadata describing the source-level types of functions, arguments, and local variables (among other things) is preserved. If the module was compiled without debug information, no metadata will be parsed at all.

There are two variants of parseLLVMFile:

• hParseLLVMFile parses its input from a Handle instead of a named file.
• parseLLVM parses its input from a (strict) ByteString.

There is also a higher-level wrapper in LLVM.Analysis.Util.Testing:

 import LLVM.Analysis.Util.Testing
 import LLVM.Parse
 main = do
   m <- buildModule ["-mem2reg", "-gvn"] (parseLLVMFile defaultParserOptions) filePath
   either error analyzeModule

This wrapper function accepts both LLVM Bitcode and C/C++ source files. Source files are compiled with clang into bitcode; the resulting bitcode is fed to the opt binary, which is passed the options in the first argument to buildModule.

By default, this helper calls binaries named clang, clang++, and opt, which are expected to be in your PATH. To accommodate distro packages, additional names are searched for opt: opt-3.2, opt-3.1, and opt-3.0.

If you cannot place these binaries in your PATH, or if your binaries have different names, you can specify them (either using absolute or relative paths) with the environment variables LLVM_CLANG, LLVM_CLANGXX, and LLVM_OPT. These environment variables override any default searching.