David Majnemer 0f26b0aeb4 [CodeGen] Teach LLVM how to lower @llvm.{min,max}num to {MIN,MAX}NAN ...

The behavior of {MIN,MAX}NAN differs from that of {MIN,MAX}NUM when only
one of the inputs is NaN: -NUM will return the non-NaN argument while
-NAN would return NaN.

It is desirable to lower to @llvm.{min,max}num to -NAN if they don't
have a native instruction for -NUM.  Notably, ARMv7 NEON's vmin has the
-NAN semantics.

N.B.  Of course, it is only safe to do this if the intrinsic call is
marked nnan.

llvm-svn: 266279

2016-04-14 07:13:24 +00:00

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