[PATCH 0/5] Add support for R_386_GOT32X/R_X86_64_[REX_]GOTPCRELX

Rafael Espíndola rafael.espindola@gmail.com
Mon Jan 18 16:44:00 GMT 2016


>> Sorry if I missed this somewhere else, but could you explain why we
>> need these new relocations? Is it just to move work from the linker to
>> the assembler or there was some correctness issue optimizing a plain
>> R_X86_64_GOTPCREL?
>>
>
> They are used to convert memory operand of test and binop into
> immediate operand, where binop is one of adc, add, and, cmp, or,
> sbb, sub, xor instructions, when position-independent code is disabled.
> The new relocation tells linker that it should try such optimization
> since binop is one of mentioned above.

But why not check the instruction in the linker? There is precedent,
since the mov to lea transformation is done for R_X86_64_GOTPCREL.

Cheers,
Rafael



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