The "private global" terminology, likely came from
llvm/lib/IR/Mangler.cpp, is misleading: "private" is the opposite of
"global", and these prefixed symbols are not global in the object file
format sense (e.g. ELF has STB_GLOBAL while these symbols are always
STB_LOCAL). The term "internal symbol" better describes their purpose:
symbols for internal use by compilers and assemblers, not meant to be
visible externally.
This rename is a step toward adopting the "internal symbol prefix"
terminology agreed with GNU as
(https://sourceware.org/pipermail/binutils/2026-March/148448.html).
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