Passes

xollvm is a toolbox of composable passes. You enable them per function via annotations; the driver runs them in a fixed topological order. All parameters are optional — unspecified keys use their defaults.

The function pipeline

expression control flow call post-hardening virtualisation

Pass	ID	Category	What it does
Constant encryption	constenc	expr	Encrypts scalar int/FP constant operands into runtime-opaque materializations.
MBA	mba	expr	Rewrites integer expressions as Mixed Boolean/Arithmetic equivalents.
Substitution	substitution	expr	Replaces instructions with equivalent idiom sequences.
Virtual call	vcall	call	Virtualises direct calls via synthetic vtables.
Basic-block split	split	cfg	Splits blocks to increase graph complexity.
Semantic diffusion	sdiff	expr	Volatile-slot masking that resists local simplification.
Bogus control flow	bcf	cfg	Opaque predicates + fake edges.
CFG flattening	flattening	cfg	Replaces structured control flow with a dispatcher.
Anti-optimization shield	shield	post	Volatile barriers + opaque identities.
Anti-decompiler	adec	post	indirectbr trampolines, asm junk, pointer aliasing.
Code virtualisation	vm	vm	Compiles the function body into a private bytecode stream.

Module-only passes (run before the function pipeline):

Pass	ID	What it does
Function merging	fmerge	Collapses same-group= functions into one selector-dispatched super-function.
String encryption	strenc	Encrypts string literals; AES-128-CTR / ChaCha20 / XOR.

Picking passes

• New here? Start with the strategy bundles.
• Matching passes to an attacker? See Choosing passes.
• vm is its own section — the Virtualization deep-dive.

vm conflicts with flattening

Both restructure the whole CFG. Use one or the other per function; the pipeline rejects the combination.