[llvm] [GISEL] Add G_VSCALE instruction (PR #84542)

[Craig Topper via llvm-commits]

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@@ -1124,6 +1124,18 @@ class MachineIRBuilder {
   MachineInstrBuilder buildInsert(const DstOp &Res, const SrcOp &Src,
                                   const SrcOp &Op, unsigned Index);
 
+  /// Build and insert \p Res = G_VSCALE \p MinElts
+  ///
+  /// G_VSCALE puts the value of the runtime vscale multiplied by \p MinElts
+  /// into \p Res.
+  ///
+  /// \pre setBasicBlock or setMI must have been called.
+  /// \pre \p Res must be a generic virtual register with scalar type.
+  /// \pre \p Src must be a generic virtual register with scalar type.
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topperc wrote:

There is no `Src`

https://github.com/llvm/llvm-project/pull/84542