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by alcover 382 days ago
> "hardcode" semi-constants

You mean you somehow avoided a load. But what if the constant was already placed in a register ? Also how could you pinpoint the reference to your constant in the machine code ? I'm quite profane about all this.
2 comments
ronsor 382 days ago
> Also how could you pinpoint the reference to your constant in the machine code?

Not OP, but often one uses an easily identifiable dummy pattern like 0xC0DECA57 or 0xDEADBEEF which can be substituted without also messing up the machine code.

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mananaysiempre 382 days ago
If you’re willing to parse object files (a much easier proposition for ELF than for just about anything else), another option is to have the source code mention the constants as addresses of external symbols, then parse the relocations in the compiled object. Unfortunately, I’ve been unable to figure out a reliable recipe to get a C compiler to emit absolute relocations in position-independent code, even after restricting myself to GCC and Clang for x86 Linux; in some configurations it works and in others you (rather pointlessly) get a PC-relative one followed by an add.
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userbinator 382 days ago
All the registers were already taken.

You use a label.

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