Add assert to prevent inf and nan in HLSLHalf_t::GetULP

Author: alsepkow

include/dxc/Test/HlslTestUtils.h

@@ -527,6 +527,10 @@ static const uint16_t Float16NegDenorm = 0x8008;
 static const uint16_t Float16PosZero = 0x0000;
 static const uint16_t Float16NegZero = 0x8000;
 
+inline bool IsInfFloat16(uint16_t val) {
+  return (val == Float16PosInf) || (val == Float16NegInf);
+}
+
 inline bool GetSign(float x) { return std::signbit(x); }
 
 inline int GetMantissa(float x) {

tools/clang/unittests/HLSLExec/LongVectorTestData.h

@@ -119,6 +119,9 @@ struct HLSLHalf_t {
   HLSLHalf_t(DirectX::PackedVector::HALF) = delete;
 
   static double GetULP(HLSLHalf_t A) {
+    DXASSERT(!IsInfFloat16(A.Val), "ULP of infinity is undefined");
+    DXASSERT(!IsNanFloat16(A.Val), "ULP of NaN is undefined");
+
     HLSLHalf_t Next = A;
     ++Next.Val;