Gentoo's Bugzilla –
Attachment 588838 Details for
Bug 693360dev-lang/rust-1.37: .../sys-devel/llvm-8.0.1/work/llvm-8.0.1.src/lib/Target/PowerPC/PPCISelDAGToDAG.cpp:1109: llvm::SDValue {anonymous}::BitPermutationSelector::ValueBit::getValue() const: Assertion `hasValue() && "Cannot get the value of a constant bit"'