skaller wrote:
This is not true. If you use a register for any purpose like this,
it can't be used for anything else and that has a cost.
On x86_64 which I use, every register is valuable. Don't you dare
take one away, it would have a serious performance impact AND
it would stop ME using that register for something which my application
might consider much more important, for example as a pointer to the
minor heap in a copying collector (Ocaml does this, it is the
reason it has very high performance.. I would do this in Felix too
if I could figure out how to reload the variable in a callback
invoked by foreign code). This applies to %fs on i386 too: if
the compiler uses that register, other uses are denied, and the
compiler can't tell which is more important.
You really can't be serious in your comment about fs, if you
understand the architecture ...
