[llvm] [LV] Support generating masks for switch terminators. (PR #99808)

[via llvm-commits]

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@@ -6456,6 +6456,17 @@ LoopVectorizationCostModel::getInstructionCost(Instruction *I,
     // a predicated block since it will become a fall-through, although we
     // may decide in the future to call TTI for all branches.
   }
+  case Instruction::Switch: {
+    if (VF.isScalar())
+      return TTI.getCFInstrCost(Instruction::Switch, CostKind);
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ayalz wrote:

The above scalar cost seems right, wonder about the vector cost below - the cost associated with predicating conditional branches is collected when visiting each phi, rather than the branch itself. May be good to calibrate  with some tests, can leave behind a TODO to be done separately.

https://github.com/llvm/llvm-project/pull/99808