On PowerPC64, when a function call offset is too large to encode in a call instruction the address is stored in a table in the data segment. A thunk is used to load the branch target address from the table relative to the TOC-pointer and indirectly branch to the callee. When linking position-dependent code the addresses are stored directly in the table, for position-independent code the table is allocated and filled in at load time by the dynamic linker.
For position-independent code the branch targets could have also gone in either the .got.plt or .igot.plt, but since the handling of the .got.plt/.igot.plt is already somewhat complicated and the .branch_lt section is needed for the position-dependent case anyway, I thought it was clearer to use the new section in both cases.
executable -> position-dependent executable?
Config->Pic is true when linking .so or PIE executable.