[llvm-dev] Reducing code size of Position Independent Executables (PIE) by shrinking the size of dynamic relocations section

Florian Weimer via llvm-dev llvm-dev at lists.llvm.org
Sun Jan 7 02:31:10 PST 2018

* Roland McGrath:

> Given this corpus of "reloc traces" you can code up many competing encoding
> formats and do serious measurements of their space savings across the
> entire corpus from simple simulations without having to implement each
> encoding in an actual toolchain and dynamic linker to do the analysis.

On the other hand, the linker currently assumes that the order in
which relative relocations are emitted does not matter.  With a
different encoding scheme, future linkers might reorder the
relocations or data objects themselves, either to reduce relocation
encoding size, or to make relocations more efficient (perhaps to
support vectorization).  Unfortunately, the numbers which can be
derived from ET_DYN files will not reflect to what extent such
reordering is possible.

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