[llvm-commits] [LLVMdev] a question about constant fold for fdiv

[Reid Spencer]

Chris / Jeff,

No need to file a bug. Here's a patch that I think solves this. Could
you (preferably both) review this to make sure I've interpreted the IEEE
754 standard correctly?

Thanks,

Reid.

On Thu, 2007-03-22 at 18:42 -0800, Chris Lattner wrote:
> On Thu, 22 Mar 2007, Jeff Cohen wrote:
> > Jeff Cohen wrote:
> >>  The standard apparently doesn't explicitly handle 0/0, but the position of 
> >>  the IEEE appears to be that it should yield a NaN of the appropriate sign. 
> >>  See http://standards.ieee.org/reading/ieee/interp/754-1985.html
> >
> > OK, it does explicitly handle it.  My reading comprehension seems to be 
> > lacking right now :(
> >
> > http://754r.ucbtest.org/standards/754xml.html#invalid-exception
> >
> > The above lists all operations that yield a NaN.
> 
> Sounds like a bug, please file it or fix it :)  The code in question is 
> VMCore/ConstantFold.cpp:654.  It should produce the appropriately signed 
> NaN instead of Inf.
> 
> -Chris
> 
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