[llvm] [VPlan] Simplify vp.merge true, (or x, y), x -> vp.merge y, true, x (PR #135017)

[Florian Hahn via llvm-commits]

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@@ -439,6 +457,104 @@ m_DerivedIV(const Op0_t &Op0, const Op1_t &Op1, const Op2_t &Op2) {
   return VPDerivedIV_match<Op0_t, Op1_t, Op2_t>({Op0, Op1, Op2});
 }
 
+template <typename Opnd_t> struct Argument_match {
+  unsigned OpI;
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fhahn wrote:

```suggestion
  /// Call argument index to match.
  unsigned OpI;
```

https://github.com/llvm/llvm-project/pull/135017