[pdb] Allow zero-copy read support for symbol streams.

This reduces the amount of memory used by llvm-pdbdump by roughly
1/3 of the size of the PDB file.

Differential Revision: http://reviews.llvm.org/D20724
Reviewed By: ruiu

llvm-svn: 271025

1 files changed, 4 insertions, 6 deletions

diff --git a/llvm/lib/DebugInfo/PDB/Raw/DbiStream.cpp b/llvm/lib/DebugInfo/PDB/Raw/DbiStream.cpp
index 35937574645..1827ab078df 100644
--- a/llvm/lib/DebugInfo/PDB/Raw/DbiStream.cpp
+++ b/llvm/lib/DebugInfo/PDB/Raw/DbiStream.cpp
@@ -136,14 +136,12 @@ Error DbiStream::reload() {
     return make_error<RawError>(raw_error_code::corrupt_file,
                                 "DBI type server substream not aligned.");
 
-  if (auto EC =
-          Reader.readStreamRef(ModInfoSubstream, Header->ModiSubstreamSize))
-    return EC;
-
   // Since each ModInfo in the stream is a variable length, we have to iterate
   // them to know how many there actually are.
-  codeview::VarStreamArray ModInfoArray(ModInfoSubstream, ModInfoRecordLength);
-  for (auto Info : ModInfoArray) {
+  codeview::VarStreamArray<ModInfo> ModInfoArray;
+  if (auto EC = Reader.readArray(ModInfoArray, Header->ModiSubstreamSize))
+    return EC;
+  for (auto &Info : ModInfoArray) {
     ModuleInfos.emplace_back(Info);
   }