Revert "remove convergent attr"

This reverts commit bc6fd04b73a195981ee77823cf1382d04ab96c44.

Author: Keenuts

clang/lib/Headers/hlsl/hlsl_intrinsics.h

@@ -1471,12 +1471,12 @@ double4 trunc(double4);
 /// true, across all active lanes in the current wave.
 _HLSL_AVAILABILITY(shadermodel, 6.0)
 _HLSL_BUILTIN_ALIAS(__builtin_hlsl_wave_active_count_bits)
-uint WaveActiveCountBits(bool Val);
+__attribute__((convergent)) uint WaveActiveCountBits(bool Val);
 
 /// \brief Returns the index of the current lane within the current wave.
 _HLSL_AVAILABILITY(shadermodel, 6.0)
 _HLSL_BUILTIN_ALIAS(__builtin_hlsl_wave_get_lane_index)
-uint WaveGetLaneIndex();
+__attribute__((convergent)) uint WaveGetLaneIndex();
 
 } // namespace hlsl
 #endif //_HLSL_HLSL_INTRINSICS_H_