AEGIS: An LLVM Pass for Hardware Reliability

Transient hardware faults — a bit flipped in a cache line or a register by a stray particle or a marginal voltage — do not announce themselves. The machine keeps running and quietly produces the wrong answer. AEGIS is an LLVM pass that makes a program check its own arithmetic, so that a corrupted value is caught before it can escape.

The pass implements Error Detection by Duplicated Instructions (EDDI). It duplicates global, stack, and heap values and compares the two copies at the points where a wrong value would become observable: before a store, before a branch, and before a function call. Getting this to work on real programs meant more than duplicating instructions:

• Call boundaries. Call sites are rewritten to pass shadow arguments and retrieve shadow return values, so duplication survives across function calls rather than stopping at each one.
• Pointer sizes. Knowing how much memory to duplicate behind a pointer is not something the IR tells you. The pass recovers it from DWARF debug metadata, falling back to a signature table for library calls.
• Extensibility. Hardening schemes are registered through a strategy registry, so adding a new one is a single self-registering file rather than an edit threaded through the pass.
• Testing. A regression suite validates both that the transformation is correct and that fault-detection coverage holds across the benchmark suite.

Measured against L1 cache fault injection, AEGIS reduces silent data corruption by 1.3× to 29× across qsort, matmul, and CRC32, at a runtime cost of 1.6× to 3.0×.

Built with C++, LLVM, Clang, and CMake.