Iverilog源码分析 -- VPI scope的实现

在Verilog里面采用module/endmodule 来组成整个design的hierarchy结构, 比如， 如下的代码：

会产生如下的hierarchy结构：

目前在Verilog的LRM， 有如下几种scope类型：

• Module
• Task
• Funcion
• Named block

在IVerilog 里面， 定义了如下6中scope以及相关的定义如下：

• vpiModule

• vpiTask

• vpiFunction
  上述3中， 比较常见， 忽略例子；

• vpiNamedBegin
  begin … end之间的语句是串行执行的；

       begin:  scope_name
            declaration；
            state1
            state2
            ...
            stateN
       end
  

• vpiNamedFork
  fork … join之间的语句是并行执行的；

       fork:  scope_name
            declaration；
            state1
            state2
            ...
            stateN
       join
  

• vpiGenScope

  1 、generate-for语句必需用genvar关键字定义for的索引变量；
  2、 for的内容必须用begin…end块包起来，哪怕只有一句；
  3、 begin…end块必须起个名字；

  module gray2bin1 (bin, gray);
  parameter SIZE = 8; // this module is parameterizable
  output [SIZE-1:0] bin;
  input [SIZE-1:0] gray;
  genvar i;generate
  for(i=0; i<SIZE; i=i+1)
       begin:bit
              assign bin[i] = ^gray[SIZE-1:i];
       end
  endgenerate
  endmodule
  

在vvp/vpi_scope.cc里面， 对于上述6中类型的scope， 每一种定义了一个class， 继承自__vpiScope积累。

在Iverilog的整个流程里面， IVerilog负责产生一个xx.vvp 文件， 这是一个网表结构的文件， vvp程序会读取该文件， 产生vvp内存的信号；

从*.v scope的产生

在verilog .v文件里面，每次碰到一个scope， 在parser.y文件定义了每一种label对应的处理函数：

void
compile_scope_decl(char*label, char*type, char*name, char*tname,
                   char*parent, long file_idx, long lineno,
                   long def_file_idx, long def_lineno, long is_cell)
{
      count_vpi_scopes += 1;
      char vec_type;
      char sign_flag;
      unsigned wid;

      __vpiScope*scope;
      if (strcmp(type,"module") == 0) {
	    scope = new vpiScopeModule(name, tname);
      } else if ( sscanf(type, "function.vec%c.%c%u", &vec_type, &sign_flag, &wid) == 3 ) {
	    int type_code;
	    if (sign_flag=='s') {
		  type_code = vpiSizedSignedFunc;
	    } else if (sign_flag=='u') {
		  type_code = vpiSizedFunc;
	    } else if (sign_flag=='i') {
		  type_code = vpiIntFunc;
	    } else {
		  assert(0);
		  type_code = vpiSizedFunc;
	    }
	    vvp_bit4_t init_val = vec_type == '4' ? BIT4_X : BIT4_0;
	    scope = new vpiScopeFunction(name, tname, false, type_code, wid, init_val);

      } else if ( sscanf(type, "autofunction.vec%c.%c%u", &vec_type, &sign_flag, &wid) == 3 ) {
	    int type_code;
	    switch (sign_flag) {
		case 's':
		  type_code = vpiSizedSignedFunc;
		  break;
		case 'u':
		  type_code = vpiSizedFunc;
		  break;
		default:
		  assert(0);
		  type_code = vpiSizedFunc;
		  break;
	    }
	    vvp_bit4_t init_val = vec_type == '4' ? BIT4_X : BIT4_0;
	    scope = new vpiScopeFunction(name, tname, true, type_code, wid, init_val);

      } else if (strcmp(type,"function.obj") == 0) {
	    scope = new vpiScopeFunction(name, tname, false, vpiSizedFunc, 0, BIT4_0);
      } else if (strcmp(type,"autofunction.obj") == 0) {
	    scope = new vpiScopeFunction(name, tname, true, vpiSizedFunc, 0, BIT4_0);
      } else if (strcmp(type,"function.real") == 0) {
	    scope = new vpiScopeFunction(name, tname, false, vpiRealFunc, 0, BIT4_0);
      } else if (strcmp(type,"autofunction.real") == 0) {
	    scope = new vpiScopeFunction(name, tname, true, vpiRealFunc, 0, BIT4_0);
      } else if (strcmp(type,"function.str") == 0) {
	    scope = new vpiScopeFunction(name, tname, false, vpiOtherFunc, 0, BIT4_0);
      } else if (strcmp(type,"autofunction.str") == 0) {
	    scope = new vpiScopeFunction(name, tname, true, vpiOtherFunc, 0, BIT4_0);
      } else if (strcmp(type,"function.void") == 0) {
	    scope = new vpiScopeFunction(name, tname, false, vpiOtherFunc, 0, BIT4_0);
      } else if (strcmp(type,"autofunction.void") == 0) {
	    scope = new vpiScopeFunction(name, tname, true, vpiOtherFunc, 0, BIT4_0);
      } else if (strcmp(type,"task") == 0) {
	    scope = new vpiScopeTask(name, tname);
      } else if (strcmp(type,"autotask") == 0) {
	    scope = new vpiScopeTaskAuto(name, tname);
      } else if (strcmp(type,"fork") == 0) {
	    scope = new vpiScopeFork(name, tname);
      } else if (strcmp(type,"autofork") == 0) {
	    scope = new vpiScopeForkAuto(name, tname);
      } else if (strcmp(type,"begin") == 0) {
	    scope = new vpiScopeBegin(name, tname);
      } else if (strcmp(type,"autobegin") == 0) {
	    scope = new vpiScopeBeginAuto(name, tname);
      } else if (strcmp(type,"generate") == 0) {
	    scope = new vpiScopeGenerate(name, tname);
      } else if (strcmp(type,"package") == 0) {
	    scope = new vpiScopePackage(name, tname);
      } else if (strcmp(type,"class") == 0) {
	    scope = new vpiScopeClass(name, tname);
      } else {
	    scope = new vpiScopeModule(name, tname);
	    assert(0);
      }

      scope->file_idx = (unsigned) file_idx;
      scope->lineno  = (unsigned) lineno;
      scope->def_file_idx = (unsigned) def_file_idx;
      scope->def_lineno  = (unsigned) def_lineno;
      scope->item = 0;
      scope->nitem = 0;
      scope->live_contexts = 0;
      scope->free_contexts = 0;

      if (is_cell) scope->is_cell = true;
      else scope->is_cell = false;

      current_scope = scope;

      compile_vpi_symbol(label, scope);

      free(label);
      free(type);
      delete[] name;
      delete[] tname;

      if (parent) {
	    static vpiHandle obj;
	    compile_vpi_lookup(&obj, parent);
	    assert(obj);
	    __vpiScope*sp = dynamic_cast<__vpiScope*>(obj);
	    vpip_attach_to_scope(sp, scope);
	    scope->scope = dynamic_cast<__vpiScope*>(obj);

	      /* Inherit time units and precision from the parent scope. */
	    scope->time_units = sp->time_units;
	    scope->time_precision = sp->time_precision;

      } else {
	    scope->scope = 0x0;

	    vpip_root_table.push_back(scope);

	      /* Root scopes inherit time_units and precision from the
	         system precision. */
	    scope->time_units = vpip_get_time_precision();
	    scope->time_precision = vpip_get_time_precision();
      }
}

添加scope的自对象

current_scope是一个全局变量， 指到当前正在处理的scope：

__vpiScope* vpip_peek_current_scope(void)
{
      return current_scope;
}
void vpip_attach_to_scope(__vpiScope*scope, vpiHandle obj)
{
      assert(scope);
      scope->intern.push_back(obj);
}