[llvm] [SelectionDAG] Unique extended single-element VT lists with VTLists (NFC) (PR #219516)

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<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-llvm-selectiondag

Author: Kazu Hirata (kazutakahirata)

<details>
<summary>Changes</summary>

This patch uniques single-element lists containing an extended EVT in
DenseSet-based VTLists, added on August 28, 2026 in commit 1829cfa8daf2.

Assisted-by: Antigravity


---
Full diff: https://github.com/llvm/llvm-project/pull/219516.diff


2 Files Affected:

- (modified) llvm/include/llvm/CodeGen/SelectionDAG.h (-3) 
- (modified) llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp (+2-1) 


``````````diff
diff --git a/llvm/include/llvm/CodeGen/SelectionDAG.h b/llvm/include/llvm/CodeGen/SelectionDAG.h
index c0649b6c75c7c..c2d457a35ceff 100644
--- a/llvm/include/llvm/CodeGen/SelectionDAG.h
+++ b/llvm/include/llvm/CodeGen/SelectionDAG.h
@@ -208,9 +208,6 @@ class SelectionDAG {
   BlockFrequencyInfo *BFI = nullptr;
   MachineModuleInfo *MMI = nullptr;
 
-  /// Extended EVTs used for single value VTLists.
-  std::set<EVT, EVT::compareRawBits> EVTs;
-
   /// Uniquing of VT lists.  Each key aliases the EVT array that the returned
   /// SDVTList points at, allocated from \p Allocator.
   struct VTListInfo {
diff --git a/llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp b/llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
index 07d7636e6cb3b..f2c919cca9d97 100644
--- a/llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
@@ -12262,7 +12262,8 @@ SDVTList SelectionDAG::getVTList(EVT VT) {
   if (!VT.isExtended())
     return makeVTList(SDNode::getValueTypeList(VT.getSimpleVT()), 1);
 
-  return makeVTList(&(*EVTs.insert(VT).first), 1);
+  EVT VTs[] = {VT};
+  return getVTList(VTs);
 }
 
 SDVTList SelectionDAG::getVTList(EVT VT1, EVT VT2) {

``````````

</details>


https://github.com/llvm/llvm-project/pull/219516