IR: Stop copying vectors of TrackingMDRef in DIBuilder

No real functionality change here, just avoiding an unnecessary copy of
std::vector<TrackingMDRef> for every subprogram with variables.

llvm-svn: 266907

1 files changed, 12 insertions, 6 deletions

diff --git a/llvm/lib/IR/DIBuilder.cpp b/llvm/lib/IR/DIBuilder.cpp
index 23a822b5..690918c 100644
--- a/llvm/lib/IR/DIBuilder.cpp
+++ b/llvm/lib/IR/DIBuilder.cpp
@@ -97,12 +97,18 @@ void DIBuilder::finalize() {
 
   DISubprogramArray SPs = MDTuple::get(VMContext, AllSubprograms);
   auto resolveVariables = [&](DISubprogram *SP) {
-    if (MDTuple *Temp = SP->getVariables().get()) {
-      const auto &PV = PreservedVariables.lookup(SP);
-      SmallVector<Metadata *, 4> Variables(PV.begin(), PV.end());
-      DINodeArray AV = getOrCreateArray(Variables);
-      TempMDTuple(Temp)->replaceAllUsesWith(AV.get());
-    }
+    MDTuple *Temp = SP->getVariables().get();
+    if (!Temp)
+      return;
+
+    SmallVector<Metadata *, 4> Variables;
+
+    auto PV = PreservedVariables.find(SP);
+    if (PV != PreservedVariables.end())
+      Variables.append(PV->second.begin(), PV->second.end());
+
+    DINodeArray AV = getOrCreateArray(Variables);
+    TempMDTuple(Temp)->replaceAllUsesWith(AV.get());
   };
   for (auto *SP : SPs)
     resolveVariables(SP);