getArgOperandNo helper function

[sstefan1]

Summary

A helper function to get argument number of a arg operand Use.

[lebedev.ri]

Can you add a test? (just refactor some code to use this)

[sstefan1]

small refactoring to use getArgOperandNo

[jdoerfert]

This looks fine but commit it only with the use (one patch maybe).

[sstefan1]

In D66844#1678550, @jdoerfert wrote:

This looks fine but commit it only with the use (one patch maybe).

Should I find another use for the method, or is this one enough?

llvm/include/llvm/IR/InstrTypes.h

bool isArgOperand(const Use *U) const {
     assert(this == U->getUser() &&
            "Only valid to query with a use of this instruction!");
     return arg_begin() <= U && U < arg_end();
   }
   bool isArgOperand(Value::const_user_iterator UI) const {
     return isArgOperand(&UI.getUse());
   }
 
+  /// Given a use for a arg operand, get the arg operand number that
+  /// corresponds to it.
+  unsigned getArgOperandNo(const Use *U) const {
+    assert(isArgOperand(U) && "Arg operand # out of range!");
+    return U - arg_begin();
+  }
+
+  /// Given a value use iterator, return the arg operand number corresponding to
+  /// it. Iterator must actually correspond to a data operand.
+  unsigned getArgOperandNo(Value::const_user_iterator UI) const {
+    return getArgOperandNo(&UI.getUse());
+  }
+
   /// Returns true if this CallSite passes the given Value* as an argument to
   /// the called function.
   bool hasArgument(const Value *V) const {
     return llvm::any_of(args(), [V](const Value *Arg) { return Arg == V; });
   }
 
   Value *getCalledOperand() const { return Op<CalledOperandOpEndIdx>(); }