2011/7/19 Johan Tibell johan.tib...@gmail.com:
On Tue, Jul 19, 2011 at 6:02 PM, Johan Tibell johan.tib...@gmail.com wrote:
I've implemented the primop but run into some difficulty: to use the
above fallback I need the code to be statically linked into every
binary. I'm not quite sure how to achieve that.
If dynamic linking doesn't hurt performance (too much). Could I stick
this piece of C code in ghc-prim? Are we guaranteed to always link
against ghc-prim?
GCC manages by having
the above function definition in libc, which is always statically
linked.
I just realized that this isn't true. I wonder if GCC's
__builtin_popcount suffers a performance degradation when libc is
dynamically linked.
I assume you meant libgcc and not libc.
I think the linking is a bit of a red herring, ideally they want to
inline it and that requires LTO and static linking and GHC can't do
LTO anyway. There should be little overhead (one extra jump, a cycle
or two) in calling a dynamically linked function compared to a
non-inlined statically linked one.
One small advantage of static linking is that the functions won't be
included if they're not used.
I think LLVM uses a small statically linked compiler run-time
library for the same purpose.
However I believe this is the case still. I'll need to doublecheck.
Johan
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Cheers,
Niklas
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