[llvm] [RISCV] Porting hasAllNBitUsers to RISCV GISel for instruction select (PR #124678)

[Craig Topper via llvm-commits]

================
@@ -186,6 +201,169 @@ RISCVInstructionSelector::RISCVInstructionSelector(
 {
 }
 
+bool RISCVInstructionSelector::hasAllNBitUsers(const MachineInstr &MI,
+                                               unsigned Bits,
+                                               const unsigned Depth) const {
+
+  assert((MI.getOpcode() == TargetOpcode::G_ADD ||
+          MI.getOpcode() == TargetOpcode::G_SUB ||
+          MI.getOpcode() == TargetOpcode::G_MUL ||
+          MI.getOpcode() == TargetOpcode::G_SHL ||
+          MI.getOpcode() == TargetOpcode::G_LSHR ||
+          MI.getOpcode() == TargetOpcode::G_AND ||
+          MI.getOpcode() == TargetOpcode::G_OR ||
+          MI.getOpcode() == TargetOpcode::G_XOR ||
+          MI.getOpcode() == TargetOpcode::G_SEXT_INREG || Depth != 0) &&
+         "Unexpected opcode");
+
+  if (Depth >= RISCVInstructionSelector::MaxRecursionDepth)
+    return false;
+
+  // Skip Vectors
+  // if(Depth == 0 && !MI.getOperand(0).isScalar())
+  //    return false;
+
+  for (MachineInstr &Use : MRI->use_instructions(MI.getOperand(0).getReg())) {
----------------
topperc wrote:

This needs to be `use_operands` so we can get the operand number. Here's the code from RISCVOptWInstrs

```
    for (auto &UserOp : MRI.use_nodbg_operands(DestReg)) {                       
      const MachineInstr *UserMI = UserOp.getParent();                           
      unsigned OpIdx = UserOp.getOperandNo(); 
```

https://github.com/llvm/llvm-project/pull/124678