[PATCH] D62623: Reduce memory consumption of coverage dumps

[serge via Phabricator via cfe-commits]

serge-sans-paille created this revision.
serge-sans-paille added reviewers: vsk, arphaman.
Herald added subscribers: cfe-commits, dexonsmith.
Herald added a project: clang.
serge-sans-paille edited the summary of this revision.

Avoiding an intermediate join operation, which in turns removes the need for an
intermediate buffer that may be quite large, as showcased by

  https://bugs.llvm.org/show_bug.cgi?id=41965


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D62623

Files:
  clang/lib/CodeGen/CoverageMappingGen.cpp


Index: clang/lib/CodeGen/CoverageMappingGen.cpp
===================================================================
--- clang/lib/CodeGen/CoverageMappingGen.cpp
+++ clang/lib/CodeGen/CoverageMappingGen.cpp
@@ -1388,10 +1388,12 @@
   std::string FilenamesAndCoverageMappings;
   llvm::raw_string_ostream OS(FilenamesAndCoverageMappings);
   CoverageFilenamesSectionWriter(FilenameRefs).write(OS);
-  std::string RawCoverageMappings =
-      llvm::join(CoverageMappings.begin(), CoverageMappings.end(), "");
-  OS << RawCoverageMappings;
-  size_t CoverageMappingSize = RawCoverageMappings.size();
+
+  size_t CoverageMappingSize = 0;
+  for (auto &S : CoverageMappings) {
+    CoverageMappingSize += S.size();
+    OS << std::move(S);
+  }
   size_t FilenamesSize = OS.str().size() - CoverageMappingSize;
   // Append extra zeroes if necessary to ensure that the size of the filenames
   // and coverage mappings is a multiple of 8.


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