ModelSim SE User's Manual - Electrical and Computer Engineering

UM-124 5 - Verilog simulation
Optimizing Verilog designs
Running vopt on your design
ModelSim SE User’s Manual
Once all of your design files are compiled into libraries, you will often want to optimize the
entire design to maximize simulator performance. The tool that performs global
optimizations is called vopt (CR-371).
Note: Gate-level designs should generally not be optimized with vopt. See "Optimizing
gate-level designs" (UM-127) below for more details.
The vopt command (CR-371) loads compiled design units from their libraries and
regenerates optimized code. The basic flow is as follows:
Compile all your modules with vlog -vopt
The -vopt argument notifies vlog that you intend to run vopt on the design. As a result,
vlog does not produce code. If you exclude the -vopt argument, vlog produces code and
then vopt reproduces the code in an optimized format. The code production from vlog is
therefore wasted.
Run vopt on the top-level module to optimize the entire design
Run vsim on the optimized design unit
Example
The following is an example invocation of vlog and vopt and the resulting transcript
messages:
% vlog -vopt cpu_rtl.v
-- Compiling module fp_unit
-- Compiling module mult_56
-- Compiling module testbench
-- Compiling module cpu
-- Compiling module i_unit
-- Compiling module mem_mux
-- Compiling module memory32
-- Compiling module op_unit
Top level modules:
testbench
% vopt testbench -o mydesign
Analyzing design...
Optimizing 8 modules of which 6 are inlined:
-- Inlining module i_unit(fast)
-- Inlining module mem_mux(fast)
-- Inlining module op_unit(fast)
-- Inlining module memory32(fast)
-- Inlining module mult_56(fast)
-- Inlining module fp_unit(fast)
-- Optimizing module cpu(fast)
-- Optimizing module testbench(fast)