[LLVMdev] spilling & xmm register usage

[Jakob Stoklund Olesen]

On Sep 29, 2010, at 8:35 AM, Ralf Karrenberg wrote:

> Hello everybody,
> 
> I have stumbled upon a test case (the attached module is a slightly
> reduced version) that shows extremely reduced performance on linux
> compared to windows when executed using LLVM's JIT.

What you are describing sounds a lot like http://llvm.org/bugs/show_bug.cgi?id=1512

New awesomeness is being added to the register allocator to deal with this, but it will probably be about 6 months before it can be turned on by default.

Some people have gotten better code form the fast allocator if the basic blocks are few and large.

The difference between Linux and Windows could be caused by different calling conventions. Don't call functions in the middle of your go-fast floating point code.

/jakob