[LLVMdev] VFCmp failing when unordered or UnsafeFPMath on x86

Evan Cheng evan.cheng at apple.com
Fri Jun 13 16:03:54 PDT 2008

On Jun 13, 2008, at 12:27 AM, Nicolas Capens wrote:

> Hi all,
> When trying to generate a VFCmp instruction when UnsafeFPMath is set  
> to true I get an assert “Unexpected CondCode” on my x86 system. This  
> also happens with UnsafeFPMath set to false and using an unordered  
> compare. Could someone look into this?

Have you filed a bug?

> While I’m at it, is there any reason why only the most significant  
> bit of the return value of VFCmp is defined (according to the  
> documentation)? Both AltiVec and SSE set the components of the  
> result to either all 1’s or all 0’s. Having only the most  
> significant bit doesn’t seem useful to me at all, and (arithmetic)  
> shifting vectors to replicate the bit isn’t supported.

Nate can probably explain this better than anyone.


> Thanks!
> Nicolas Capens
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