libnss_tcb: Allow for local-dynamic TLS-model optimizations. #29
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Ready for review. Let's do #28 after this one. |
Since we dropped the conditionalized use of readdir_r(3) in commit 557818c, the dirstream object for use with readdir(3) can now get adapted easily in a way the compiler (and/or the linker) is able to apply global-dynamic to local-dynamic optimizations for the used thread-local storage model. Signed-off-by: Björn Esser <[email protected]>
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I doubt those potential optimizations outweigh the complexity added here, and besides Ulrich's https://www.akkadia.org/drepper/tls.pdf says local-dynamic is only more optimal when there's more than one variable. But I don't mind.
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According to Ulrich Drepper, "The local dynamic TLS model is an optimization of the general dynamic TLS model. The compiler can generate code following this model if it can recognize that the thread-local variable is defined in the same object it is referenced in. This includes, for instance, thread-local variables with file scope". Given that |
Well, yes, one would need to check the relocs in asm ouput of the file. Anyways, I've verified that we in fact don't need this. Closing here. |
Since we dropped the conditionalized use of readdir_r(3) in commit 557818c, the dirstream object for use with readdir(3) can now get adapted easily in a way the compiler (and/or the linker) is able to apply global-dynamic to local-dynamic optimizations for the used thread-local storage model.