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#![no_builtins] should prevent a crate from participating in LTO #35540
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OK, I looked at the code around LTO and I think I know how to implement this. Will implement it and report back.
It works! I'll send a PR.
- added a commit that references this issue
on Aug 16, 2016
This attribute is needed to prevent LLVM from optimizing a
memcpyimplementation into a recursive call. However this attribute is not preserved in LTO builds: the attribute only works if it is set at the top-level crate.Since crates containing implementations of built-in functions aren't meant to be called directly, they don't benefit from LTO and should be linked as a separate object.
One workaround (using rlibc as an example) is to first compile a
rlibc_innercrate as a staticlib with#![no_builtins], and then compile therlibccrate as a rlib which links torlibc_inner.a.cc #31544 @alexcrichton @japaric