[llvm-commits] [llvm] r154265 - in /llvm/trunk: lib/CodeGen/SelectionDAG/DAGCombiner.cpp test/CodeGen/ARM/vdiv_combine.ll test/CodeGen/X86/fdiv.ll

[Benjamin Kramer]

On 08.04.2012, at 19:51, Duncan Sands wrote:

> Hi Benjamin,
> 
>>>> One thing to keep in mind is that we don't want to turn fdivs into fmuls with a denormal number. Denormals may be disabled on the CPU (ops always return 0.0), in other cases they are just painfully slow.
>>> 
>>> how to tell if the reciprocal is denormal?  I don't immediately see an APFloat
>>> method for that.
>> 
>> I guess it needs a new method, there seems to be no way to check it from the outside :(
> 
> is it actually possible for a reciprocal to be denormal?

Yes, for very large numbers.

> printf("%d\n", isnormal(1.0/DBL_MAX));
0

- Ben

> 
> Ciao, Duncan.