[llvm] [LoopVectorize][NFC] Simplify ScaledReductionExitInstrs map (PR #123368)

[Florian Hahn via llvm-commits]

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@@ -8913,9 +8914,9 @@ VPRecipeBuilder::tryToCreateWidenRecipe(Instruction *Instr,
              Phi->getIncomingValueForBlock(OrigLoop->getLoopPreheader()));
 
       // If the PHI is used by a partial reduction, set the scale factor.
-      std::optional<std::pair<PartialReductionChain, unsigned>> Pair =
+      std::optional<unsigned> Scale =
           getScaledReductionForInstr(RdxDesc.getLoopExitInstr());
-      unsigned ScaleFactor = Pair ? Pair->second : 1;
+      unsigned ScaleFactor = Scale ? *Scale : 1;
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fhahn wrote:

Does something like `Scale.value_or(1)` work? 

https://github.com/llvm/llvm-project/pull/123368