[Gankra]

hmm i've always just mentally modelled TLS as "yeah the OS slaps a pointer to an array in this one register".

but i guess the difference between "pointer to an array" and "a segment of memory" isn't actually that big?

[amluto]

It’s a funny register: you don’t want to read it (and before Ivy Bridge, user code couldn’t read it). The base is added by the CPU when you dereference the pointer. So code like:

    __thread int array[100];
    array[n] += 5:

Effectively computes the offset portion of array+n and then, using CPU assistance, accesses that memory relative to the segment.