The failed shard is the JavaScriptSemanticGraphBuilder short-circuit
mutation test, which also failed on main run 38003459598 at the same
base commit (08ec2bf8) before this branch started CI, and passed on
main run 38003459600 minutes later at the same commit.
The cross-format oracle requires a callee whose recovered control flow
has more than one basic block, and rea_cross_branch provided it through
a symmetric if/else of tail calls. Clang 21 folds that shape into a
conditional negate plus one tail branch, a single basic block, so the
lane rejected a correct Ghidra analysis of the fixture.
Give the branch a loop whose trip count depends on a volatile global:
no compiler can eliminate the backedge, and the callee stays multi-block
at every optimization level on every toolchain.
GRAB Racem