[Bug 266] Can threadasm.S be replaced with generics?

[via D.gnu]

https://bugzilla.gdcproject.org/show_bug.cgi?id=266

--- Comment #3 from Iain Buclaw <ibuclaw at gdcproject.org> ---
(In reply to Iain Buclaw from comment #2)
> (In reply to Johannes Pfau from comment #1)
> > What is the add/sub fp code supposed to do? Doesn't this actually restore
> > the old stack pointer (have to look up the ARM assembler operand order, but
> > isn't add.. => fp = sp+28 and sub... => sp = fp-28 which restores the old
> > sp?).
> 
> Hmm, yeah you're right.  It would all be fine if it weren't for the
> restoring of the FP.  Having a look again, there is the same in the x86
> version too.
> 
> 
>         mov     QWORD PTR [rdi], rsp
>         mov     rsp, rsi
>         lea     rsp, -40[rbp]  <-- Here.
> 
> 

And this explains why the call to stack_restore() was optimized away entirely
without a compiler level memory barrier.  I was rather puzzled by that last
night.

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