57 lines
2.1 KiB
Plaintext
57 lines
2.1 KiB
Plaintext
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HOW IT WORKS
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The VPI interface for Icarus Verilog works by creating from a
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collection of PLI applications a single vpi module. The vpi module
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includes compiled code for the applications linked together (with any
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other libraries that the applications need) into a module with a
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single exported symbol, the vlog_startup_routines array.
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The product that wishes to invoke the module (normally at run time)
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loads the module, locates the vlog_startup_routines table, and calls
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all the startup routines contained in that table. It is possible for a
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product to link with many modules. In that case, all the modules are
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linked in and startup routines are called in order.
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The product that uses vpi modules uses the environment variable
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VPI_MODULE_PATH as a ':' separated list of directories. This is the
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module search path. When a module is specified by name (using whatever
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means the product supports) the module search path is scanned until
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the module is located.
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The special module name "system.vpi" is part of the core Icarus
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Verilog distribution and includes implementations of the standard
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system tasks/functions.
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COMPILING A VPI MODULE (LINUX)
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To compile a module, first compile down to object files all the PLI
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applications that you wish to include in the module. Then, create a
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small "C" source file that defines only the startup table like so:
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extern void hello_register();
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void (*vlog_startup_routines[])() = {
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hello_register,
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0
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};
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Compile this table source down to its object file, as well. Finally,
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link the application with the command:
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cc -o foo.vpi -shared <all the .o files>
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No VPI libraries need to be included because the product that loads
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the module will supply all the standard vpi functions. If you use any
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non-vpi library functions, you may need to include libraries to
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support them.
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The resulting foo.vpi file is the vpi module. Place it in a location
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where the product to use it can locate it.
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CAVEAT EMPTOR
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Only the calltf function is supported. The compiletf and sizetf
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functions are invoked at compile time, and the ivl compiler does not
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yet support VPI.
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