I'm not aware of any definitive definition of HLS, but generally the term is used to describe something like Xilinx Vitis HLS, which is a set of tools to transform C or Cpp (-ish) programs into something that can be "run" on an fpga.
Silice ( to the extent I understand it ) and projects like Chisel and migen are tools to compensate for some of the shortcomings of verilog and vhdl mostly in areas concerning software engineering practices: modularity, code-reuse, strong typing, testability.
Silice ( to the extent I understand it ) and projects like Chisel and migen are tools to compensate for some of the shortcomings of verilog and vhdl mostly in areas concerning software engineering practices: modularity, code-reuse, strong typing, testability.