[clang] [clang][modules] Only serialize info for locally-included headers (PR #113718)

[via cfe-commits]

llvmbot wrote:


<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-clang-modules

Author: Jan Svoboda (jansvoboda11)

<details>
<summary>Changes</summary>

I noticed that some PCM files contain `HeaderFileInfo` for headers only included in a dependent PCM file, which is wasteful.

This patch changes the logic to only write headers that are included locally. This makes the PCM files smaller and saves some superfluous deserialization of `HeaderFileInfo` triggered by `Preprocessor::alreadyIncluded()`.

---
Full diff: https://github.com/llvm/llvm-project/pull/113718.diff


3 Files Affected:

- (modified) clang/include/clang/Lex/Preprocessor.h (+1-1) 
- (modified) clang/lib/Lex/HeaderSearch.cpp (-1) 
- (modified) clang/lib/Serialization/ASTWriter.cpp (+3-3) 


``````````diff
diff --git a/clang/include/clang/Lex/Preprocessor.h b/clang/include/clang/Lex/Preprocessor.h
index f3f4de044fc41a..38a527d2324ffe 100644
--- a/clang/include/clang/Lex/Preprocessor.h
+++ b/clang/include/clang/Lex/Preprocessor.h
@@ -1490,7 +1490,7 @@ class Preprocessor {
   /// Mark the file as included.
   /// Returns true if this is the first time the file was included.
   bool markIncluded(FileEntryRef File) {
-    HeaderInfo.getFileInfo(File);
+    HeaderInfo.getFileInfo(File).IsLocallyIncluded = true;
     return IncludedFiles.insert(File).second;
   }
 
diff --git a/clang/lib/Lex/HeaderSearch.cpp b/clang/lib/Lex/HeaderSearch.cpp
index 8826ab449df493..052be1395161d4 100644
--- a/clang/lib/Lex/HeaderSearch.cpp
+++ b/clang/lib/Lex/HeaderSearch.cpp
@@ -1582,7 +1582,6 @@ bool HeaderSearch::ShouldEnterIncludeFile(Preprocessor &PP,
     }
   }
 
-  FileInfo.IsLocallyIncluded = true;
   IsFirstIncludeOfFile = PP.markIncluded(File);
   return true;
 }
diff --git a/clang/lib/Serialization/ASTWriter.cpp b/clang/lib/Serialization/ASTWriter.cpp
index 494890284d2f2c..612fdf499fa750 100644
--- a/clang/lib/Serialization/ASTWriter.cpp
+++ b/clang/lib/Serialization/ASTWriter.cpp
@@ -2163,8 +2163,8 @@ void ASTWriter::WriteHeaderSearch(const HeaderSearch &HS) {
       continue; // We have no information on this being a header file.
     if (!HFI->isCompilingModuleHeader && HFI->isModuleHeader)
       continue; // Header file info is tracked by the owning module file.
-    if (!HFI->isCompilingModuleHeader && !PP->alreadyIncluded(*File))
-      continue; // Non-modular header not included is not needed.
+    if (!HFI->isCompilingModuleHeader && !HFI->IsLocallyIncluded)
+      continue; // Header file info is tracked by the including module file.
 
     // Massage the file path into an appropriate form.
     StringRef Filename = File->getName();
@@ -2176,7 +2176,7 @@ void ASTWriter::WriteHeaderSearch(const HeaderSearch &HS) {
       SavedStrings.push_back(Filename.data());
     }
 
-    bool Included = PP->alreadyIncluded(*File);
+    bool Included = HFI->IsLocallyIncluded || PP->alreadyIncluded(*File);
 
     HeaderFileInfoTrait::key_type Key = {
       Filename, File->getSize(), getTimestampForOutput(*File)

``````````

</details>


https://github.com/llvm/llvm-project/pull/113718