[llvm] [RegAllocFast] Handle single-vdef instrs faster (PR #96284)

[Matt Arsenault via llvm-commits]

================
@@ -258,7 +258,7 @@ class RegAllocFastImpl {
   /// cannot be allocated.
   RegUnitSet UsedInInstr;
   RegUnitSet PhysRegUses;
-  SmallVector<uint16_t, 8> DefOperandIndexes;
+  SmallVector<unsigned, 8> DefOperandIndexes;
----------------
arsenm wrote:

Probably should pre-commit this 

https://github.com/llvm/llvm-project/pull/96284