Added bit_field intrisic

Author: Eichenherz

include/nbl/builtin/hlsl/bit.hlsl

@@ -23,6 +23,12 @@ NBL_ALIAS_TEMPLATE_FUNCTION(std::rotl, rotl);
 NBL_ALIAS_TEMPLATE_FUNCTION(std::rotr, rotr);
 NBL_ALIAS_TEMPLATE_FUNCTION(std::countl_zero, countl_zero);
 
+template<typename Unsigned>
+Unsigned bitfield_extract_unsigned( Unsigned val, uint32_t offsetBits, uint32_t numBits )
+{
+    return ( val >> offsetBits ) & ( ( 1 << numBits ) - 1 );
+}
+
 }
 #else
 
@@ -102,6 +108,13 @@ uint16_t countl_zero(T n)
     return impl::clz<sizeof(T)*8>(n);
 }
 
+// TODO: templated "switch" depending on signedness  
+template<typename Unsigned>
+Unsigned bitfield_extract_unsigned( Unsigned val, uint32_t offsetBits, uint32_t numBits )
+{
+    return spirv::bitfieldExtractUnsigned<Unsigned>( val, offsetBits, numBits );
+}
+
 }
 }
 #endif

include/nbl/builtin/hlsl/spirv_intrinsics/core.hlsl

@@ -129,6 +129,15 @@ void memoryBarrier(uint32_t memoryScope, uint32_t memorySemantics);
 template<class T, class U>
 [[vk::ext_instruction(spv::OpBitcast)]]
 T bitcast(U);
+
+template<typename Unsigned>
+[[vk::ext_instruction( spv::OpBitFieldUExtract )]]
+Unsigned bitfieldExtractUnsigned( Unsigned val, uint32_t offsetBits, uint32_t numBits );
+
+template<typename Signed>
+[[vk::ext_instruction( spv::OpBitFieldSExtract )]]
+Signed bitfieldExtractSigned( Signed val, uint32_t offsetBits, uint32_t numBits );
+
 }
 #endif
 }