We've had several user reports of this through our support, and reproduced it
internally as well (on a 270X, which is our officially supported minimum spec).
Seems to be specific to SI cards.

Given that this has regressed since the original release of the game, is it
possible to get a workaround into Mesa, e.g. disabling the load/store
vectorizer like suggested for SI cards (perhaps just restricted to Hitman),
until the issue is resolved in LLVM?