# VCS编译加速：三步编译和分块编译

验证问题：有不同穿层信号时，模块的partition库能否reuse?

结论：**当穿层信号变化时，受影响的模块不能reuse**。

## 快速开始

### 第一次编译

```bash
make all GENLIB=1
```

### 第二次编译

```bash
make all GENLIB=0
```

## 运行结果

```
Top Level Modules:
       testbench
TimeScale is 1 ns / 1 ps

Note-[PC_SHARED] Reusing shared partition
  Reusing partition '_vcs_pc_package_' from shared library './partitionlib'.



Note-[PC_SHARED] Reusing shared partition
  Reusing partition 'uvm_pkg' from shared library './partitionlib'.



Note-[PC_SHARED] Reusing shared partition
  Reusing partition 'counter_a' from shared library './partitionlib'.



Warning-[PC_NOT_SHARED] Cannot reuse shared partition
  Cannot reuse partition 'counter_b' from shared library './partitionlib'

  There are additional signals that are now targets of hierarchical
  references.



Note-[PC_GEN_PARTITION] Generating partition
  Generating new partition 'counter_b' at
  './partitionlib_test2/counter_b_ipFRWc'.


Warning-[PC_NOT_SHARED] Cannot reuse shared partition
  Cannot reuse partition 'counter_c' from shared library './partitionlib'

  There are additional signals that are now targets of hierarchical
  references.



Note-[PC_GEN_PARTITION] Generating partition
  Generating new partition 'counter_c' at
  './partitionlib_test2/counter_c_chn5zb'.


Note-[PC_SHARED] Reusing shared partition
  Reusing partition 'top' from shared library './partitionlib'.



Warning-[PC_NOT_SHARED] Cannot reuse shared partition
  Cannot reuse partition 'TB.testbench' from shared library './partitionlib'

  Modified Design Units :
        TB.testbench : "./rtl/testbench.sv", 20
  Type of targets of hierarchical references in this partition have changed.



Note-[PC_RECOMPILE] Recompiling partition
  Recompiling partition 'TB.testbench' because of following changes.

  Modified Design Units :
        TB.testbench : "./rtl/testbench.sv", 20
```

检查log可以发现，穿层信号变化涉及到的模块`counter_b、counter_c`都无法reuse。

## 结论

| 序号 | 条件                                                  | 现象    | 结论                         | 备注 |
| ---- | ----------------------------------------------------- | ------- | ---------------------------- | ---- |
| 1    | 第一次：引用a.name； 第二次引用a.name/b.name/c.name； | b/c重编 | 不同的模块，增加的引用会重编 |      |
| 2    | 第一次：引用a.name；第二次引用a.age；                 | a重编   | 同一个模块，不同引用也会重编 |      |
| 3    | 第一次：引用a.name/a.age；第二次引用a.name；          | a重编   | 同一个模块，减少引用也会重编 |      |
| 4    | 第一次：引用a.name；第二次引用a.name/a.age；          | a重编   | 同一个模块，增加引用也会重编 |      |

⚠：只要模块的穿层引用发生变化，就会导致该模块重编。

✍官方文档VCSLCAFeatures.pdf第408页，也有类似表述：Any change in XMRs, trigger recompilation of the referee partition.