[llvm] Attributor: Avoid double map lookup in updateAttrMap (PR #182666)

[via llvm-commits]

llvmbot wrote:


<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-llvm-transforms

Author: Matt Arsenault (arsenm)

<details>
<summary>Changes</summary>

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.

---
Full diff: https://github.com/llvm/llvm-project/pull/182666.diff


1 Files Affected:

- (modified) llvm/lib/Transforms/IPO/Attributor.cpp (+7-8) 


``````````diff
diff --git a/llvm/lib/Transforms/IPO/Attributor.cpp b/llvm/lib/Transforms/IPO/Attributor.cpp
index 9a35696b7627c..daaaf4176946a 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,

``````````

</details>


https://github.com/llvm/llvm-project/pull/182666