R_X86_64_SIZE64/R_X86_64_SIZE32 relocations were introduced in 0.98v of "System V Application Binary Interface x86-64" (http://www.x86-64.org/documentation/abi.pdf).
Calculation for them is Z + A, where:
Z - Represents the size of the symbol whose index resides in the relocation entry.
A - Represents the addend used to compute the value of the relocatable field.
Currently afaik gold does not support these, but bfd does.
Is this correct? If my understanding is correct, if a symbol can be preempted, SIZE relocations for the symbol are ignored in this implementation. Is this what you expected?