HercuLeS is a new high-level synthesis tool marketed by Ajax Compilers (http://www.ajaxcompilers.com). HercuLeS has been in development since 2009 and it seems that now is the proper time to hit the market Full disclosure: I’m the main (read: sole) developer of HercuLeS.
HercuLeS is based on the following flow: C-> GIMPLE -> N-Address Code -> VHDL.
HercuLeS is extensible in since frontends, analyses and optimization passes can be added by third parties. At this moment, HercuLeS is bundled with a number of external modules for analyses and optimizations at the C, NAC (N-Address Code, its textual IR), Graphviz, and VHDL levels. It supports vendor-independent code so generated HDL descriptions are synthesizable (in principle) to either FPGA or ASIC targets.
It should be noted that certain things are still missing from HercuLeS and there is ongoing work to support them in the future. This is inevitable since our resources are somewhat limited. For instance there is no Verilog backend yet.
We are looking to establish close communication with our users. Our users provide inspiration and their requests drive future development. Criticism is well-accepted at Ajax Compilers