[LLVMdev] XMM in X86 Backend

Dale Johannesen dalej at apple.com
Mon Jun 7 12:17:16 PDT 2010

On Jun 7, 2010, at 10:04 AMPDT, kapil anand wrote:
> LLVM Backend is using xmms it involves a lot of register moves. llc  
> has one option -mcpu=686, where output does not use xmm but it  
> disables some other instructions also. Is there any fine grain  
> optimization flag like ( -mfpmath = 387 which is present in gcc)  
> which would just instruction backend to use fpstack instead of SSE  
> instructions and still not limit the instructions


Note that this doesn't change the calling convention; in particular,  
the only supported calling convention for 64-bit x86 uses SSE, so  
you'll get an error if you use the above for a function returning  
double in 64-bit mode.

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