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

[Thorsten Schütt via llvm-commits]

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@@ -1289,6 +1289,15 @@ def G_MERGE_VALUES : GenericInstruction {
   let variadicOpsType = type1;
 }
 
+// Generic vscale.
+// Puts the value of the runtime vscale multiplied by the value in the source
+// operand into the destination register.
+def G_VSCALE : GenericInstruction {
+  let OutOperandList = (outs type0:$dst);
+  let InOperandList = (ins untyped_imm_0:$src);
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tschuett wrote:

For G_CONSTANT, we retrieve the value as following:
https://github.com/llvm/llvm-project/blob/cf1319f9c6561afea381bbfc1a18f5c1fb7b46b0/llvm/lib/CodeGen/GlobalISel/Utils.cpp#L395

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