| Issue |
61447
|
| Summary |
[C++20] [Modules] Writing PCM will be unexpectedly slow with additional import.
|
| Labels |
clang:modules
|
| Assignees |
|
| Reporter |
ChuanqiXu9
|
We can find the reproducer at: https://discourse.llvm.org/t/modules-increased-build-times/68755/7
For short:
```
// test.cppm
module;
#include <iostream>
export module test;
import vulkan; // Vulcan is constructed big module.
```
will take 3~4s to generate the pcm.
And
```
module;
#include <iostream>
export module test.without.import;
```
will take about 0.5s to complete only.
Note that:
```
#include <iostream>
import vulkan;
```
will take 0.5s to complete too.
Currently I located in `ASTWriter::WriteDecl`. But I am not sure if this can be fixed simply.
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