FAQ

Enzyme builds successfully but won’t run tests ¶

Double check that Enzyme’s build can find lit, LLVM’s testing framework. This can be done by explicitly passing lit as an argument to CMake as described here .

Enzyme is Crashing ¶

LLVM’s plugin infrastructure is broken in many versions. Empirically LLVM 8 and up will often incorrectly disallow memory from being passed between LLVM and a plugin. If you see one of these errors and want to use the same version of LLVM try passing the flag enzyme_preopt=0 described here . The flag disables preprocessing optimizations that Enzyme runs and tends to reduce these errors. If this doesn’t work, check the following.

Illegal TypeAnalysis on LLVM 10+ ¶

There is a known bug in an existing LLVM optimization pass (SROA) that will incorrectly generate type information from a memcpy. This bug has been fixed in LLVM 13

opt can’t find -enzyme option ¶

When you use opt command like below:

opt input.ll -load=/path/to/LLVMEnzyme-VERSION.so -enzyme -o output.ll -S

opt reports a error:opt: unknown pass name 'enzyme'

May be because you are using LLVM 13 or a higher version, which has switched to the new pass manager pipeline. On applicable LLVM versions (up to and including LLVM 15), you can specify that opt useees the old pass manager by adding the --enable-new-pm=0 flag. Alternatively, you can use the new pass manager, which uses the following syntax for opt:

opt input.ll -load-pass-plugin=/path/to/LLVMEnzyme-VERSION.so -passes=enzyme -o output.ll -S

If you are using CMake, Enzyme exports a special ClangEnzymeFlags target which will automatically add the correct flags. See here for an example.

Other ¶

If you have an issue not resolved here, please make an issue on Github and consider making a pull request to this FAQ!