Looking into LLVM

Jakub Jelinek jakub at redhat.com
Mon Oct 26 15:52:48 UTC 2009


On Mon, Oct 26, 2009 at 10:54:46AM -0400, Peter Jones wrote:
> Well, that plus your already voiced complaint about its dwarf generation,
> which is to say that any fairly immediate adoption would also make normal
> development and debugging more painful.

It is not just about horrible dwarf generation, the performance of LLVM
generated code is worse than GCC, you can forget about all the
security enhancements GCC has added in the last 10 years (say
__builtin_object_size is parsed by clang/llvm, but always says it doesn't
know the size, I'm not aware of LLVM supporting something like
-fstack-protector), etc.  A lot of stuff is just stubbed in LLVM, look at
e.g. its __builtin_expect implementation.  You need to look through the hype
at what disadvantages it has.

While there are places where compile time speed is most important (in some
JITing cases), the distro isn't one of those places.

	Jakub




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