High-level synthesis (HLS) is widely used to translate a behavioural specification written in C/C++ into a register transfer level (RTL) design. Due to the abstraction gap, it is a challenging task to guarantee the functional equivalence between the input C/C++ code and its corresponding RTL of HLS. This paper presents a C to RTL equivalence checking framework DEEQ for HLS verification. In our proposed method, a high-level behaviour is first extracted from the RTL. It then identifies all traces of both behaviours, merges compatible traces within a behavior, finds corresponding traces between two behaviours using a data-driven approach. Finally, a satisfiability problem is formulated to prove the equivalence of corresponding traces of both behaviours. The proposed method is completely automated and does not take any internal information from the HLS tool. Experimental results show that our proposed method proves the end-to-end equivalence for a commercial HLS tool for several benchmarks.