[llvm] [RISCV][VLOPT] Add support for vrgather (PR #148249)

[Luke Lau via llvm-commits]

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@@ -747,6 +747,14 @@ getOperandLog2EEW(const MachineOperand &MO, const MachineRegisterInfo *MRI) {
     return TwoTimes ? MILog2SEW + 1 : MILog2SEW;
   }
 
+  // Vector Register Gather with 16-bit Index Elements Instruction
+  // Dest and source data EEW=SEW. Index vector EEW=16.
+  case RISCV::VRGATHEREI16_VV: {
+    if (MO.getOperandNo() == 2)
+      return 4;
+    return MILog2SEW;
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lukel97 wrote:

Can you add MIR tests for VRGATHEREI16_VV in vl-opt-op-info.mir?

https://github.com/llvm/llvm-project/pull/148249