Introduction to SystemC Verification Library (SCV)

Anupam BakshiAgnisys, Inc.

April 14th 2013

ISCUG

What does SystemC Verification need?

• Test Generation

– Constrained Random

• Connection to HDL

– At various busses in the test bench

• Functional Coverage

– Scoreboard

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What SCV provides?

• Test Generation– Constrained Randomization

– Weighted Randomization

• Connection to HDL– API for connection to HDL

• Functional Coverage– Transaction monitoring & recording ability

– But no built-in coverage

– Requires post processing

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What SCV Provides? (contd.)

• Data Introspection (similar to Verilog PLI but for C/C++ data structures)

• Randomization and seed management for reproducibility of simulation runs

• Transaction Monitoring and Recording

• Sparse Array Support

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How to get started with SCV?

• Download SystemC and SCV : http://www.accellera.org

– Get SystemC lib : systemc-2.3.0.tgz

– Get SCV lib : scv-1.0p2-sysc2.2.12jun06.tgz

• Compile SystemC

• Compile SCV

– On x86_64 linux will need a patch

• http://thawedoutnow.blogspot.tw/2013/02/scv-for-x8664-linux-patch.html

• OR use Simulation Vendor Tools

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Running SCV examples

• Copy Makefile.rules.in to Makefile.rules– Define variables to point to the SCV and SystemC

include and lib directories

includedir=/home/cae/systemc/systemc-2.3.0/include

libdir=/home/cae/systemc/systemc-2.3.0/lib-linux64

SYSC_INC_PREFIX=$includedir

SYSC_LIB_PREFIX=$libdir

• Ensure LD_LIBRARY_PATH is set for dynamic libraries

• Patch is required : scv_constraint.h.patch

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SCV Smart Pointer

• Key to using SCV

• No hassles of memory allocation/de-allocation

• Randomization

• Weighted Randomization

• Constrained Randomization

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scv_smart_ptr<T> and scv_extensionsobject

This slide © WHDL (Intro to SystemC Modeling and Verification).

Reproduced with permission.

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data_type T

scv_extensions<T>object

scv_smart_ptr<T> constructor automatically creates underlying scv_extensions objectscv_smart_ptr<T>

Acts like a pointer to the scv_extensions object

scv_smart_pointer example

scv_smart_pointer<int> sm_int(“sm_int_label”);

sm_int->print();

sm_int->next(); // randomize values

sm_int->keep_out(1, 5);

sm_int->keep_only(-10, 10);

sm_int->write(10);

sm_int->read();

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Randomization

• Get a new random value set

– Next()

• Initialize the random number generator

– scv_random::set_global_seed(int)

• Pick a different seed each time

– scv_random::pick_random_seed()

• Enable/disable randomization

– enable_randomization()/disable_randomization()

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Random Distribution

• Ranges

– keep_out()

– keep_only()

• Weighted

Distribution

– scv_bag()

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scv_smart_ptr<data_t> data_p("data");

//create a distribution for generating the state data//highest probabilty for states 1-4, zero chance for 3

and//lower probability for 0, 5, and 6.

scv_bag<onehot_t> state_dist("state_dist");state_dist.add(STATE_0, 10);state_dist.add(STATE_1, 25);state_dist.add(STATE_2, 25);state_dist.add(STATE_4, 25);state_dist.add(STATE_5, 10);state_dist.add(STATE_6, 5);

//set the distribution for the state variable in data_pdata_p->state.set_mode(state_dist);

Constraints

struct addr_constraint : public scv_constraint_base {//create the objects that will be constrainedscv_smart_ptr<int> row;scv_smart_ptr<int> col;

SCV_CONSTRAINT_CTOR(addr_constraint) {//constraint row to be between 10 and 50 exclusive or 200 and 250 inclusiveSCV_CONSTRAINT ( (row() > 10 && row() < 50) ||

(row() >= 200 && row() <= 250) );

//constraint col to be less than row+20 and greater than row-5SCV_CONSTRAINT ( col() > ( row() - 5) );SCV_CONSTRAINT ( col() < ( row() + 20) );

}};

// SCV_SOFT_CONSTRAINT : Only warning, if constraint is not met, no error

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Constraints (contd.)

scv_random::set_global_seed(1023);

//instantiate a constrained objectaddr_constraint addr("addr");

//randomize the object five times and print the valuesfor(int i=0; i<5; ++i) {addr.next();scv_out << "Row: " << *(addr.row) << "; Col: “ << *(addr.col) << endl;

}scv_out << endl;

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SCV Register Examplestruct reg1_t {sc_uint<2> field1;sc_uint<5> field2;

};

struct reg2_t {sc_uint<3> f1;sc_uint<4> f2;sc_uint<1> f3;

};

struct block_t {reg1_t reg1;reg2_t reg2;

};

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template<>class scv_extensions<block_t> : public

scv_extensions_base<block_t> {public:

scv_extensions<reg1_t > reg1;scv_extensions<reg2_t > reg2;

SCV_EXTENSIONS_CTOR(block_t) {SCV_FIELD(reg1);SCV_FIELD(reg2);

}};

SCV Register Example (contd.)

scv_smart_ptr<block_t> block_p ("block");

scv_random::set_global_seed(10);

block_p->reg1.field2.keep_only(1, 10);

block_p->next();

block_p->print();

block_p->next();

block_p->print();

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SCV Register example outputRandom value for block:{

reg1 {field1:2field2:5 // Note the value has been constrained

}reg2 {

f1:3f2:13f3:0

}}

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{reg1 {field1:3field2:2

}reg2 {f1:0f2:9f3:1

}}

Summary

• SCV promotes advanced verification methodology

• Where to go for more info?

– Go to the source : www.accellera.org

– Join the SystemC Verification Working Group (VWG)

• Apparently working on the next release

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Q/A

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