Fix C++ emit for bit_cast inst. (shader-slang#1570)

Co-authored-by: Yong He <yhe@nvidia.com>

Author: csyonghe

prelude/slang-cpp-types.h

@@ -1036,6 +1036,12 @@ struct ComputeVaryingInput
 typedef void(*ComputeThreadFunc)(ComputeThreadVaryingInput* varyingInput, void* uniformEntryPointParams, void* uniformState);
 typedef void(*ComputeFunc)(ComputeVaryingInput* varyingInput, void* uniformEntryPointParams, void* uniformState);
 
+template<typename TResult, typename TInput>
+TResult slang_bit_cast(TInput val)
+{
+    return *(TResult*)(&val);
+}
+
 #ifdef SLANG_PRELUDE_NAMESPACE
 }
 #endif

prelude/slang-cuda-prelude.h

@@ -1237,6 +1237,12 @@ __device__ uint3 operator*(uint3 a, dim3 b)
     return r;
 }
 
+template<typename TResult, typename TInput>
+__inline__ __device__ TResult slang_bit_cast(TInput val)
+{
+    return *(TResult*)(&val);
+}
+
 /* !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! */
 
 

source/slang/slang-emit-cpp.cpp

@@ -2238,9 +2238,9 @@ bool CPPSourceEmitter::tryEmitInstExprImpl(IRInst* inst, const EmitOpInfo& inOut
         }
         case kIROp_BitCast:
         {
-            m_writer->emit("((");
+            m_writer->emit("(slang_bit_cast<");
             emitType(inst->getDataType());
-            m_writer->emit(")(");
+            m_writer->emit(">(");
             emitOperand(inst->getOperand(0), getInfo(EmitOp::General));
             m_writer->emit("))");
             return true;