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_namedeclaration；state1state2...stateNend

vpiNamedFork
fork … join之间的语句是并行执行的；

     fork:  scope_namedeclaration；state1state2...stateNjoin

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:bitassign 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 thesystem 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);
}