Custom hardware accelerators usage is shifting towards new application domains such as graph analytics and unstructured text analysis. These applications expose complex control-flow which is challenging to map to hardware, especially when operating from a C/C++ description using High-Level Synthesis toolchains. Several approaches relying on speculative execution have been proposed to overcome those limitations, but they often fail to handle the multiple interacting speculations required for realistic use-cases. This paper proposes a fully automated hardware synthesis flow based on a source-to-source compiler that identifies and explores intricate speculation configurations to generate speculative hardware accelerators.