[PDB] Add the ability to lookup global symbols by name.

The Globals table is a hash table keyed on symbol name, so
it's possible to lookup symbols by name in O(1) time.  Add
a function to the globals stream to do this, and add an option
to llvm-pdbutil to exercise this, then use it to write some
tests to verify correctness.

llvm-svn: 343951

1 files changed, 8 insertions, 0 deletions

diff --git a/llvm/lib/DebugInfo/PDB/Native/ModuleDebugStream.cpp b/llvm/lib/DebugInfo/PDB/Native/ModuleDebugStream.cpp
index 2e1f61c7a25..6464b85982e 100644
--- a/llvm/lib/DebugInfo/PDB/Native/ModuleDebugStream.cpp
+++ b/llvm/lib/DebugInfo/PDB/Native/ModuleDebugStream.cpp
@@ -97,6 +97,14 @@ ModuleDebugStreamRef::symbols(bool *HadError) const {
   return make_range(SymbolArray.begin(HadError), SymbolArray.end());
 }
 
+CVSymbol ModuleDebugStreamRef::readSymbolAtOffset(uint32_t Offset) const {
+  // Offsets include the size of the 4-byte magic at the beginning, but lookup
+  // doesn't take that into account, so subtract it here.
+  auto Iter = SymbolArray.at(Offset - 4);
+  assert(Iter != SymbolArray.end());
+  return *Iter;
+}
+
 iterator_range<ModuleDebugStreamRef::DebugSubsectionIterator>
 ModuleDebugStreamRef::subsections() const {
   return make_range(Subsections.begin(), Subsections.end());