TLS and x86-64 fs:
Cecil Ward
cecil at cecilward.com
Wed Jun 28 23:41:34 UTC 2023
On Wednesday, 28 June 2023 at 23:39:43 UTC, Cecil Ward wrote:
> It seems that in x86-64 Linux (which I think is what
> godbolt.org uses - is that correct?), LDC emits a function call
> to get the address of your TLS static base. GDC seems to be
> vastly more efficient as it simply uses an fs: segment override
> and apart from that accesses the RAM directly. I don’t know
> what is happening if someone takes the address of a TLS static
> and mixes it with a comparison or pointer arithmetic with say
> an alloc cell or address in one of the stacks. How that works
> is a GDC question.
>
> I wonder why the difference in method between the compilers ?
> Could LDC steal the GDC tech here in order to get much more
> speed ?
Perhaps I should try taking the address of a TLS static with GDC
and taking a look at its value?
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