User Tools

Site Tools


Icarus Verilog compiler man-page

iverilog(1)		 $Date: 2005/06/28 04:25:55 $		   iverilog(1)

       iverilog - Icarus Verilog compiler

       iverilog	 [-ESVv]  [-Bpath] [-ccmdfile] [-g1|-g2|-g2x] [-Dmacro[=defn]]
       [-pflag=value] [-Iincludedir] [-mmodule] [-Mfile]  [-Nfile]  [-ooutput-
       filename]  [-stopmodule]	 [-ttype]  [-Tmin/typ/max]  [-Wclass] [-ypath]

       iverilog is a compiler that translates Verilog source  code  into  exe-
       cutable	programs  for simulation, or other netlist formats for further
       processing. The currently supported targets are vvp for simulation, and
       xnf and fpga for synthesis. Other target types are added as code gener-
       ators are implemented.

       iverilog accepts the following options:

       -Bbase  The iverilog program uses external programs  and	 configuration
	       files  to  preprocess and compile the Verilog source. Normally,
	       the path used to locate these tools is built into the  iverilog
	       program.	 However,  the	-B  switch allows the user to select a
	       different set of programs. The path given  is  used  to	locate
	       ivlpp, ivl, code generators and the VPI modules.

       -cfile  This  flag specifies an input file that contains a list of Ver-
	       ilog source files. This is similar to the command file of other
	       Verilog simulators, in that it is a file that contains the file
	       names instead of taking them on the command line.  See  Command
	       Files below.

       -Dmacro Defines macro macro with the string ‘1’ as its definition. This
	       form is normally only used to trigger ifdef conditionals in the
	       Verilog source.

	       Defines macro macro as defn.

       -E      Preprocess  the Verilog source, but do not compile it. The out-
	       put file is the Verilog input, but  with	 file  inclusions  and
	       macro  references  expanded  and	 removed.  This is useful, for
	       example, to preprocess Verilog source for use by other  compil-

	       Select  the  Verilog language generation to support in the com-
	       piler. This selects between IEEE1364-1995(1), IEEE1364-2001(2),
	       or   Verilog   with  extension(2x).  Normally,  Icarus  Verilog
	       defaults to the latest known generation of the  language.  This
	       flag is most useful to restrict the language to a set supported
	       by tools of specific generations, for compatibility with	 other

	       Append directory includedir to list of directories searched for
	       Verilog include files. The -I switch may be used many times  to
	       specify	several	 directories  to  search,  the directories are
	       searched in the order they appear on the command line.

       -Mpath  Write into the file specified by path a list of files that con-
	       tribute	to  the compilation of the design. This includes files
	       that are included by include  directives	 and  files  that  are
	       automatically loaded by library support. The output is one file
	       name per line, with no leading or trailing space.

	       Add this module to the list of VPI modules to be loaded by  the
	       simulation.  Many  modules  can	be  specified, and all will be
	       loaded, in the order specified. The system module  is  implicit
	       and always included.

       -Npath  This  is used for debugging the compiler proper. Dump the final
	       netlist form of the design to the specified file. It  otherwise
	       does  not  affect  operation  of the compiler. The dump happens
	       after the design is elaborated and optimized.

       -o filename
	       Place output in the file filename. If no output	file  name  is
	       specified, iverilog uses the default name a.out.

	       Assign  a value to a target specific flag. The -p switch may be
	       used as often as necessary to specify all  the  desired	flags.
	       The  flags that are used depend on the target that is selected,
	       and are described in target specific documentation. Flags  that
	       are not used are ignored.

       -S      Synthesize.  Normally,  if  the	target	can  accept behavioral
	       descriptions the compiler will leave  processes	in  behavioral
	       form.  The  -S  switch causes the compiler to perform synthesis
	       even if it is not necessary for the target. If the target  type
	       is  a  netlist  format, the -S switch is unnecessary and has no

       -s topmodule
	       Specify the top level module to elaborate. Icarus Verilog  will
	       by  default  choose  modules  that  are not instantiated in any
	       other modules, but sometimes that is not sufficient, or instan-
	       tiates too many modules. If the user specifies one or more root
	       modules with -s flags, then they will be used as	 root  modules

	       Use   this  switch  to  select  min,  typ  or  max  times  from
	       min:typ:max expressions. Normally, the compiler will simply use
	       the  typ value from these expressions (with a warning) but this
	       switch will tell the compiler explicitly which  value  to  use.
	       This  will  suppress  the warning that the compiler is making a

	       Use this switch to specify the target output  format.  See  the
	       TARGETS section below for a list of valid output formats.

       -v      Turn  on	 verbose  messages.  This will print the command lines
	       that are executed to perform the actual compilation, along with
	       version information from the various components, as well as the
	       version of the product as a whole.  You will  notice  that  the
	       command	lines include a reference to a key temporary file that
	       passes information to the compiler proper.  To keep  that  file
	       from  being  deleted  at the end of the process, provide a file
	       name of your own in the environment variable  IVERILOG_ICONFIG.

       -V      Print the version of the compiler, and exit.

       -Wclass Turn  on	 different  classes of warnings. See the WARNING TYPES
	       section below for descriptions of the different warning groups.
	       If  multiple -W switches are used, the warning set is the union
	       of all the requested classes.

	       Append the directory to the library module  search  path.  When
	       the  compiler  finds  an	 undefined  module,  it looks in these
	       directories for files with the right name.

       The Icarus Verilog compiler supports module  libraries  as  directories
       that  contain  Verilog  source files.  During elaboration, the compiler
       notices the instantiation of undefined module types. If the user speci-
       fies library search directories, the compiler will search the directory
       for files with the name of the missing module type. If it finds such  a
       file,  it loads it as a Verilog source file, they tries again to elabo-
       rate the module.

       Library module files should contain only a single module, but  this  is
       not  a  requirement. Library modules may reference other modules in the
       library or in the main design.

       The Icarus Verilog compiler supports a variety of targets, for  differ-
       ent purposes, and the -t switch is used to select the desired target.

       null    The  null  target  causes no code to be generated. It is useful
	       for checking the syntax of the Verilog source.

       vvp     This is the default. The vvp target generates code for the  vvp
	       runtime.	 The  output  is a complete program that simulates the
	       design but must be run by the vvp command.

       xnf     This is the Xilinx Netlist Format used by many tools for	 plac-
	       ing devices in FPGAs or other programmable devices. This target
	       is obsolete, use the fpga target instead.

       fpga    This is a synthesis target that	supports  a  variety  of  fpga
	       devices,	 mostly by EDIF format output. The Icarus Verilog fpga
	       code generator can generate complete  designs  or  EDIF	macros
	       that  can  in  turn  be	imported  into larger designs by other
	       tools. The fpga target implies the synthesis -S flag.

       These are the types of warnings that can be selected by the -W  switch.
       All the warning types (other then all) can also be prefixed with no- to
       turn off that warning. This is most useful after a  -Wall  argument  to
       suppress isolated warning types.

       all     This enables all supported warning categories.

	       This  enables  warnings	for creation of implicit declarations.
	       For example, if a scalar wire X is used but not declared in the
	       Verilog source, this will print a warning at its first use.

	       This  enables  warnings for ports of module instantiations that
	       are not connected but probably should be. Dangling input ports,
	       for example, will generate a warning.

	       This  enables  warnings	for  inconsistent use of the timescale
	       directive. It detects if some modules have no timescale, or  if
	       modules inherit timescale from another file. Both probably mean
	       that timescales are inconsistent, and simulation timing can  be
	       confusing and dependent on compilation order.

       If the source file name as a .sft suffix, then it is taken to be a sys-
       tem function table file. A  System  function  table  file  is  used  to
       describe to the compiler the return types for system functions. This is
       necessary because the compiler  needs  this  information	 to  elaborate
       expressions  that  contain  these  system functions, but cannot run the
       sizetf functions since it has no run-time.

       The format of the table is ASCII, one function per  line.  Empty	 lines
       are  ignored,  and  lines that start with the ’#’ character are comment
       lines. Each non-comment line starts with the function  name,  then  the
       vpi type (i.e. vpiSysFuncReal). The following types are supported:

	       The function returns a real/realtime value.

	       The function returns an integer.

       vpiSysFuncSized <wid> <signed|unsigned>
	       The  function  returns  a  vector  with the given width, and is
	       signed or unsigned according to the flag.

       The command file allows the user to place source file names and certain
       command	line  switches	into  a text file instead of on a long command
       line. Command files can include C or C++ style comments, as well	 as  #
       comments, if the # starts the line.

       file name
	       A  simple  file	name or file path is taken to be the name of a
	       Verilog source file. The path starts with the first  non-white-
	       space character. Variables are substitued in file names.

       -y libdir
	       A  -y  token  prefixes a library directory in the command file,
	       exactly like it does on the command line. The parameter to  the
	       -y flag may be on the same line or the next non-comment line.

	       Variables in the libdir are substituted.

	       The +incdir+ token in command files gives directories to search
	       for include files in much the same way that -I  flags  work  on
	       the  command  line. The difference is that multiple +includedir
	       directories are valid parameters to a  single  +incdir+	token,
	       although you may also have multiple +incdir+ lines.

	       Variables in the includedir are substituted.

	       The +libext token in command files fives file extensions to try
	       when looking for a library file. This is useful in  conjunction
	       with  -y flags to list suffixes to try in each directory before
	       moving on to the next library directory.

	       This is another way to specify library directories. See the  -y

	       This  is	 like the +libdir statement, but file names inside the
	       directories declared here are  case  insensitive.  The  missing
	       module  name  in a lookup need not match the file name case, as
	       long as the letters are correct.	 For  example,	"foo"  matches
	       "Foo.v" but not "bar.v".

	       The  +define+ token is the same as the -D option on the command
	       line. The value part of the token is optional.

	       This token causes file names after this in the command file  to
	       be  translated to uppercase. This helps with situations where a
	       directory has passed through a DOS machine, and in the  process
	       the file names become munged.

	       This  is similar to the +toupper-filename hack described above.

       In certain cases, iverilog supports variables in command	 files.	 These
       are  strings of the form "$(varname)", where varname is the name of the
       environment variable to read. The entire string is  replaced  with  the
       contents	 of  that  variable. Variables are only substitued in contexts
       that explicitly support them, including file and directory strings.

       Variable values come from the operating	system	environment,  and  not
       from preprocessor defines elsewhere in the file or the command line.

       These  examples	assume	that  you  have	 a  Verilog source file called
       hello.v in the current directory

       To compile hello.v to an executable file called a.out:

	    iverilog hello.v

       To compile hello.v to an executable file called hello:

	    iverilog -o hello hello.v

       To compile and run explicitly using the vvp runtime:

	    iverilog -ohello.vvp -tvvp hello.v

       To compile hello.v to a file in XNF-format called hello.xnf

	    iverilog -txnf -ohello.xnf hello.v

       Steve Williams (

       vvp(1), <>

       Copyright ©  2002 Stephen Williams

       This document can be freely redistributed according to the terms of the
       GNU General Public License version 2.0

Version			 $Date: 2005/06/28 04:25:55 $		   iverilog(1)
geda/icarus_mp.txt · Last modified: 2012/02/20 15:14 (external edit)