-memory addresses referenced from the elements of the bitset metadata. The pass
-will lay out the referenced globals consecutively, so their definitions must
-be available at LTO time. An intrinsic, :ref:`llvm.bitset.test <bitset.test>`,
-generates code to test whether a given pointer is a member of a bitset.
+memory addresses referenced from the elements of the bitset metadata. The
+pass will lay out referenced global variables consecutively, so their
+definitions must be available at LTO time.
+
+A bit set containing functions is transformed into a jump table, which
+is a block of code consisting of one branch instruction for each of the
+functions in the bit set that branches to the target function, and redirect
+any taken function addresses to the corresponding jump table entry. In the
+object file's symbol table, the jump table entries take the identities of
+the original functions, so that addresses taken outside the module will pass
+any verification done inside the module.
+
+Jump tables may call external functions, so their definitions need not
+be available at LTO time. Note that if an externally defined function is a
+member of a bitset, there is no guarantee that its identity within the module
+will be the same as its identity outside of the module, as the former will
+be the jump table entry if a jump table is necessary.
+
+The `GlobalLayoutBuilder`_ class is responsible for laying out the globals
+efficiently to minimize the sizes of the underlying bitsets. An intrinsic,
+:ref:`llvm.bitset.test <bitset.test>`, generates code to test whether a
+given pointer is a member of a bitset.