[llvm] 5d3332b - [DWARFLinker] Use union to reduce sizeof(WorklistItem) (NFC)

[Jonas Devlieghere via llvm-commits]

Author: Jonas Devlieghere
Date: 2020-11-06T23:24:41-08:00
New Revision: 5d3332bc3ce2de80c68f4d63a7204e3f5803523b

URL: https://github.com/llvm/llvm-project/commit/5d3332bc3ce2de80c68f4d63a7204e3f5803523b
DIFF: https://github.com/llvm/llvm-project/commit/5d3332bc3ce2de80c68f4d63a7204e3f5803523b.diff

LOG: [DWARFLinker] Use union to reduce sizeof(WorklistItem) (NFC)

Reduce the size of the WorklistItem struct by using a struct.

Added: 
    

Modified: 
    llvm/include/llvm/DWARFLinker/DWARFLinker.h

Removed: 
    


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diff  --git a/llvm/include/llvm/DWARFLinker/DWARFLinker.h b/llvm/include/llvm/DWARFLinker/DWARFLinker.h
index 2fb61b9edf55..a96f403f6811 100644
--- a/llvm/include/llvm/DWARFLinker/DWARFLinker.h
+++ b/llvm/include/llvm/DWARFLinker/DWARFLinker.h
@@ -353,24 +353,26 @@ class DWARFLinker {
   /// of work needs to be performed when processing the current item. The flags
   /// and info fields are optional based on the type.
   struct WorklistItem {
-    WorklistItemType Type;
     DWARFDie Die;
+    WorklistItemType Type;
     CompileUnit &CU;
     unsigned Flags;
-    unsigned AncestorIdx = 0;
-    CompileUnit::DIEInfo *OtherInfo = nullptr;
+    union {
+      const unsigned AncestorIdx;
+      CompileUnit::DIEInfo *OtherInfo;
+    };
 
     WorklistItem(DWARFDie Die, CompileUnit &CU, unsigned Flags,
                  WorklistItemType T = WorklistItemType::LookForDIEsToKeep)
-        : Type(T), Die(Die), CU(CU), Flags(Flags) {}
+        : Die(Die), Type(T), CU(CU), Flags(Flags), AncestorIdx(0) {}
 
     WorklistItem(DWARFDie Die, CompileUnit &CU, WorklistItemType T,
                  CompileUnit::DIEInfo *OtherInfo = nullptr)
-        : Type(T), Die(Die), CU(CU), OtherInfo(OtherInfo) {}
+        : Die(Die), Type(T), CU(CU), Flags(0), OtherInfo(OtherInfo) {}
 
     WorklistItem(unsigned AncestorIdx, CompileUnit &CU, unsigned Flags)
-        : Type(WorklistItemType::LookForParentDIEsToKeep), CU(CU), Flags(Flags),
-          AncestorIdx(AncestorIdx) {}
+        : Die(), Type(WorklistItemType::LookForParentDIEsToKeep), CU(CU),
+          Flags(Flags), AncestorIdx(AncestorIdx) {}
   };
 
   /// returns true if we need to translate strings.