Almost any higher level language to verilog/vhdl conversion will not give you optimal results, except for very basic implementations. The problem is the C/Matlab/ etc. languages do not have hardware constructs, so the conversion is forced to basically generate a flat unrolled design that ends up taking more resources and running slower than the desired operation.
In one case I worked on, a software engineer tried to use a C->Verilog converter to generate code for image warping. The C code worked, but was too slow. (Taking several seconds to warp a signal 800x480 frame). She worked with an FAE for over 4 months trying to convert the algorithm to a hardware implementation. The net result was they could never get it to fit in the target device.
I took the software and was able to generate a pretty small design that could do the warping at 20->30 pfs. (with 15 fps being the target update rate).