Attributor: Avoid double map lookup in updateAttrMapusers/arsenm/attributor/avoid-double-map-lookup-updateAttrMap

This will leave behind the map entry in the unchanged case,
but this seems to not matter. Could erase the newly inserted
entry if that happens, but that also doesn't seem to make a
difference.

1 files changed, 7 insertions, 8 deletions

diff --git a/llvm/lib/Transforms/IPO/Attributor.cpp b/llvm/lib/Transforms/IPO/Attributor.cpp
index 9a35696b7627..daaaf4176946 100644
--- a/llvm/lib/Transforms/IPO/Attributor.cpp
+++ b/llvm/lib/Transforms/IPO/Attributor.cpp
@@ -1136,13 +1136,11 @@ Attributor::updateAttrMap(const IRPosition &IRP, ArrayRef<DescTy> AttrDescs,
     break;
   };
 
-  AttributeList AL;
+  AttributeList AL = IRP.getAttrList();
   Value *AttrListAnchor = IRP.getAttrListAnchor();
-  auto It = AttrsMap.find(AttrListAnchor);
-  if (It == AttrsMap.end())
-    AL = IRP.getAttrList();
-  else
-    AL = It->getSecond();
+  auto [Iter, Inserted] = AttrsMap.insert({AttrListAnchor, AL});
+  if (!Inserted)
+    AL = Iter->second;
 
   LLVMContext &Ctx = IRP.getAnchorValue().getContext();
   auto AttrIdx = IRP.getAttrIdx();
@@ -1160,8 +1158,9 @@ Attributor::updateAttrMap(const IRPosition &IRP, ArrayRef<DescTy> AttrDescs,
 
   AL = AL.removeAttributesAtIndex(Ctx, AttrIdx, AM);
   AL = AL.addAttributesAtIndex(Ctx, AttrIdx, AB);
-  AttrsMap[AttrListAnchor] = AL;
-  return ChangeStatus::CHANGED;
+
+  Iter->second = AL;
+  return HasChanged;
 }
 
 bool Attributor::hasAttr(const IRPosition &IRP,