[llvm] [RISCV] Initial codegen support for the XRivosVizip extension (PR #131933)

[Min-Yih Hsu via llvm-commits]

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@@ -4611,6 +4613,36 @@ static bool isElementRotate(std::array<std::pair<int, int>, 2> &SrcInfo,
          SrcInfo[1].second - SrcInfo[0].second == (int)NumElts;
 }
 
+static bool isAlternating(const std::array<std::pair<int, int>, 2> &SrcInfo,
+                          const ArrayRef<int> Mask, bool RequiredPolarity) {
+  int NumElts = Mask.size();
+  for (unsigned i = 0; i != Mask.size(); ++i) {
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mshockwave wrote:

nit:
```suggestion
  for (unsigned i = 0; i != NumElts; ++i) {
```

https://github.com/llvm/llvm-project/pull/131933